Preface

Pyrolysis is an irreversible thermochemical treatment process of materials at elevated temperatures in an inert atmosphere. Pyrolysis is used heavily in the chemical industry to produce many forms of carbon and other chemicals from petroleum, coal, wood, oil shale, biomass or organic waste materials. It is the basis of several methods for producing fuel from biomass. Pyrolysis also is the process of conversion of buried organic matter into fossil fuels.

Many factors contribute to making pyrolysis an attractive and possibly an essential process for converting biomass into bio-fuel or bio-energy. During the last fifty years or so, and almost within living memory, man has witnessed an almost imperceptible change in the energy situation from surplus and cheap availability to scarcity. Renewable sources of energy have to be found in order to meet the continuously rising demand and decreasing energy reserves. Waste products and other low-quality sources of energy and bottom-of-the-barrel residues may no longer be discarded, and pyrolysis is one of the most effective processes for treating and upgrading waste products.

Books and learned articles on pyrolysis are not few in number, but a new book on pyrolysis is always called for in view of the continuous developments and new processes in this important field of the chemical industry. The chapters in this book cover a wide area of this important topic. The introductory chapter in particular gives a brief but comprehensive account of the various pyrolysis processes, products and materials. The other chapters of the book deal with specific processes including, among others, fast pyrolysis and pyrolysis of lignin and biomass materials such as waste tyres and waste plastics. Other topics discussed include synthesis of different pyrolysis products including bio-oil and biochar and modelling and optimization of pyrolysis products.

Readers of this book may not find an exhaustive or an encyclopaedic account of all pyrolysis processes, products and materials, but they will find many interesting and relevant topics related to different aspects of pyrolysis discussed by eminent researchers in this field from across the world.

A final word needs to be said regarding IntechOpen in particular and other publishers of open access books, which have made knowledge and research freely available to all who seek it. The cooperation and support of the IntechOpen staff in the preparation and final publication of this book is duly acknowledged.

> **Hassan Al-Haj Ibrahim** Professor of Chemical Engineering, Director of Quality Assurance, Arab University for Science and Technology, Hamah, Syria

**1**

**Chapter 1**

**1. Introduction**

*Hassan Al-Haj Ibrahim*

treated with light rather than heat.

the hazardous health effects of smoking.

ture, pressure and chemical agents [1].

quent secondary reactions of the primary volatiles.

Introductory Chapter: Pyrolysis

gasification varies between 0.25 and 0.50 (*Er* = 0.25 − 0.50).

Pyrolysis, or thermolysis, is in essence an irreversible thermochemical treatment process of complex solid or fluid chemical substances at elevated temperatures in an inert or oxygen-free atmosphere, where the rate of pyrolysis is temperaturedependent and it increases with temperature. During pyrolysis the molecules are subjected to very high temperatures leading to very high molecular vibrations at which the molecules are stretched and shaken to such an extent that they start breaking down into smaller molecules. Pyrolysis also is always the first step in other processes such as gasification and combustion where partial or total oxidation of the treated material occurs. Thermochemical treatment processes are generally classified according to their equivalence ratio (ER), which is defined as the amount of air added relative to the amount of air required for stoichiometric combustion. The equivalence ratio for pyrolysis is 0 (ER = 0), whereas the equivalence ratio for combustion is equal to or greater than 1 (*ER* ≥ 1), and the equivalence ratio for

The word "pyrolysis" is coined from two Ancient Greek words pyro (πυρο) meaning fire and lysis (λύσις) meaning separating (or solution), so pyrolysis means separation by fire or heat. In photolysis, by contrast, the chemical substances are

The simplest example of pyrolysis is food cooking. When food is cooked, the temperature of food increases leading to higher molecular vibrations and breakdown of larger complex molecules into smaller and simpler molecules which are easier to digest. Another example of pyrolysis is the pyrolysis of tobacco, paper and additives, in cigarettes and other products, which generates many volatile products including nicotine, carbon monoxide and tar that are responsible for the aroma and

A process similar to the pyrolysis process takes place to some extent in nature, where organic substances of biological origin are buried and transformed into fossil fuels and coals of progressively higher carbon content under the action of tempera-

Pyrolysis is basically a thermal decomposition process where a raw material of high molecular weight is decomposed or cracked to produce primary volatiles. The primary thermal decomposition and dehydrogenation reactions are accompanied in general with secondary polymerization and isomerization reactions of the primary volatiles. The extent of the secondary reactions depends on the pyrolysis conditions as well as on the type of the pyrolysis reactor used. Secondary reactions are generally favored by high residence times and high temperatures. As it is practically impossible to achieve a completely oxygen-free atmosphere, there will be a small amount of oxidation reactions as well. The yields of the pyrolysis products are due to both the primary decomposition reactions of the raw material and the subse-

## **Chapter 1**

## Introductory Chapter: Pyrolysis

*Hassan Al-Haj Ibrahim*

## **1. Introduction**

Pyrolysis, or thermolysis, is in essence an irreversible thermochemical treatment process of complex solid or fluid chemical substances at elevated temperatures in an inert or oxygen-free atmosphere, where the rate of pyrolysis is temperaturedependent and it increases with temperature. During pyrolysis the molecules are subjected to very high temperatures leading to very high molecular vibrations at which the molecules are stretched and shaken to such an extent that they start breaking down into smaller molecules. Pyrolysis also is always the first step in other processes such as gasification and combustion where partial or total oxidation of the treated material occurs. Thermochemical treatment processes are generally classified according to their equivalence ratio (ER), which is defined as the amount of air added relative to the amount of air required for stoichiometric combustion. The equivalence ratio for pyrolysis is 0 (ER = 0), whereas the equivalence ratio for combustion is equal to or greater than 1 (*ER* ≥ 1), and the equivalence ratio for gasification varies between 0.25 and 0.50 (*Er* = 0.25 − 0.50).

The word "pyrolysis" is coined from two Ancient Greek words pyro (πυρο) meaning fire and lysis (λύσις) meaning separating (or solution), so pyrolysis means separation by fire or heat. In photolysis, by contrast, the chemical substances are treated with light rather than heat.

The simplest example of pyrolysis is food cooking. When food is cooked, the temperature of food increases leading to higher molecular vibrations and breakdown of larger complex molecules into smaller and simpler molecules which are easier to digest. Another example of pyrolysis is the pyrolysis of tobacco, paper and additives, in cigarettes and other products, which generates many volatile products including nicotine, carbon monoxide and tar that are responsible for the aroma and the hazardous health effects of smoking.

A process similar to the pyrolysis process takes place to some extent in nature, where organic substances of biological origin are buried and transformed into fossil fuels and coals of progressively higher carbon content under the action of temperature, pressure and chemical agents [1].

Pyrolysis is basically a thermal decomposition process where a raw material of high molecular weight is decomposed or cracked to produce primary volatiles. The primary thermal decomposition and dehydrogenation reactions are accompanied in general with secondary polymerization and isomerization reactions of the primary volatiles. The extent of the secondary reactions depends on the pyrolysis conditions as well as on the type of the pyrolysis reactor used. Secondary reactions are generally favored by high residence times and high temperatures. As it is practically impossible to achieve a completely oxygen-free atmosphere, there will be a small amount of oxidation reactions as well. The yields of the pyrolysis products are due to both the primary decomposition reactions of the raw material and the subsequent secondary reactions of the primary volatiles.

The end products of pyrolysis include solid residual coproducts and ash, noncondensable gases and condensable liquids known variously as pyrolysis oil, pyrolytic oil, bio-oil or tar. The type and yields of the pyrolysis products depend for the most part on the type of material treated. The pyrolysis end products can also be controlled by optimizing pyrolysis parameters such as temperature, heating rate, residence time, pressure, feed particle size and type of reactor. For example, the production of bio-oil through pyrolysis, which is a thermodynamically nonequilibrium process, requires only a short residence time in a high-temperature zone followed by rapid thermal quenching. In some pyrolysis processes, a product that is up to 80% liquid by weight can be produced.

Pyrolysis is mostly applied to organic materials. It is basically a carbonization process where an organic material of high molecular weight is decomposed or cracked to produce a solid residue with high (or higher) carbon content and some volatile products. As is well-known, any organic matter can be carbonized or made to lose progressively its atoms other than carbon to become an artificial carbon material or "carbon". In addition to organic materials, pyrolysis can be applied in certain cases to inorganic materials and to water and aqueous solutions.

Pyrolysis is an endothermic process. Determination of the overall energy balance and the thermal efficiency of the process is a fundamental step in designing an efficient pyrolysis reactor. The use of renewable energy or solar-thermal power to drive pyrolysis could make the process more economical and carbon neutral [2, 3].

Pyrolysis reactions typically occur at temperatures between 400 and 800°C. As the temperature changes, the product distribution can be altered. Lower pyrolysis temperatures usually produce more liquid and solid products, while higher temperatures favor the production of more gases as a result of more powerful thermal cracking reactions. The pyrolysis temperature has also a significant effect on the properties of the pyrolysis products. The calorific value of the pyrolytic oil, for example, increases mostly with increasing temperature.

The rate of heat transfer also influences the product distribution. In fast pyrolysis at lower temperatures, higher heating rates and small residence times favor liquid yield as the cracking of larger molecules to produce gaseous products is hindered. Liquid yield is also favored by immediate and rapid quenching which is often used to maximize the production of liquid products by condensing the vapors and gaseous molecules. Intermediate pyrolysis in screw reactors with longer residence time (minutes vs. seconds) can also be used for bio-oil production. In this process, two condensates are usually obtained, an aqueous phase and an organic phase defined as bio-oil. Although the yield of bio-oil is lower compared to fast pyrolysis, the bio-oils produced from intermediate pyrolysis are more stable, contain less oxygen, and have lower molecular weight substances, and the process is easier to control [4]. Slow pyrolysis, on the other hand, can be used to maximize the yield of solid char. This process requires slow pyrolytic decomposition at low temperatures.

Pyrolysis may be carried out at atmospheric or higher pressure or in vacuum where uncontrolled combustion is avoided. In practice, however, pyrolysis is mostly carried out at atmospheric pressure as creating a vacuum or high pressure drastically increases the cost of process equipment. Operation under high pressures results generally in greater yields of biochar and gases, while lower pressure or vacuum results in increased production of liquid products.

While feed particle size may not greatly affect pyrolysis product distribution, larger particle size tends in general to increase the liquid yield at a higher temperature range. Smaller particle sizes on the other hand favor the internal heat transfer within the particles. In fluidized bed reactors, the particles must be greater than a minimum, in order to avoid entrainment of fines, particularly where the material has a low density [5].

**3**

*Introductory Chapter: Pyrolysis*

products.

biomass [7, 8].

system [9].

unusable byproducts.

cals and chemical feedstocks.

**2. Industrial applications of pyrolysis**

*DOI: http://dx.doi.org/10.5772/intechopen.90366*

commercial-scale production of pyrolysis oil [6].

Reactor type is crucial for the efficient production of pyrolysis oil. Reactor types include packed or fixed-bed reactors, rotary kiln reactors and fluidized bed reactors. Fluidized bed reactors in particular, such as the auger, bubbling fluidized bed reactor and the circulating fluidized bed reactor, are highly efficient for the large

Fluidized and fixed-bed reactors are mostly exterior-heating pyrolysis reactors where heat is transmitted from the exterior surface to the interior of the material. In fluidized bed reactors, fluidization increases mixing and interaction leading to efficient heat transfer, uniform temperatures, improved reaction rates and higher yield of bio-oil. On the other hand, interior heating is utilized in microwave-assisted pyrolysis with high energy effectiveness and the production of uniform products. Unlike traditional heating, microwave heating provides quick quenching of the pyrolysis vapors, which avoids secondary decomposition reactions of the primary

A catalyst may be used in catalytic pyrolysis processes to improve the yield and lower the temperature and/or time of reaction. Aromatic hydrocarbons such as benzene, toluene and xylenes may be directly produced by catalytic pyrolysis of

A pyrolysis-based process has several advantages over other treatment processes:

1.The technology is relatively simple and can be made compact and lightweight. Applications of pyrolysis processes range from large-scale industrial applications where high temperatures are used to smaller-scale operations, even portable biomass conversion units, where the temperatures may be much lower. Mobile pyrolysis units for the production of liquid and solid fuels have been designed for the treatment of timber and lumber mill and other agricultural wastes. The pyrolysis units are built on trailers and consist of four basic groups: feed preparation machinery, a fluidized bed pyrolysis vessel, product separation equipment and an onboard gas turbine electrical generation

2.Pyrolysis, furthermore, can be conducted as a batch, low-pressure process,

3.Pyrolysis can also be used for all types of solid and liquid products and can be

4.The pyrolysis technology can be designed to produce minimal amounts of

5.In comparison with other treatment processes such as gasification, pyrolysis produces in general fewer air emissions, lower emission of nitrogen and sulfur oxides, less CO2 generation, less dust emission and no emission of dioxin inside

Pyrolysis is a proven and energetically efficient chemical technology that is used heavily in the chemical industry. Pyrolysis may be used in biorefineries for making a wide range of products and materials on which a future sustainable society may be based including many forms of carbon, fuels and other potentially valuable chemi-

the pyrolyzer due to the pyrolysis with deoxidized hydrocarbon gas.

with minimal requirements for feedstock preprocessing.

easily adapted to changes in feedstock composition.

#### *Introductory Chapter: Pyrolysis DOI: http://dx.doi.org/10.5772/intechopen.90366*

*Recent Advances in Pyrolysis*

up to 80% liquid by weight can be produced.

The end products of pyrolysis include solid residual coproducts and ash, noncondensable gases and condensable liquids known variously as pyrolysis oil, pyrolytic oil, bio-oil or tar. The type and yields of the pyrolysis products depend for the most part on the type of material treated. The pyrolysis end products can also be controlled by optimizing pyrolysis parameters such as temperature, heating rate, residence time, pressure, feed particle size and type of reactor. For example, the production of bio-oil through pyrolysis, which is a thermodynamically nonequilibrium process, requires only a short residence time in a high-temperature zone followed by rapid thermal quenching. In some pyrolysis processes, a product that is

Pyrolysis is mostly applied to organic materials. It is basically a carbonization process where an organic material of high molecular weight is decomposed or cracked to produce a solid residue with high (or higher) carbon content and some volatile products. As is well-known, any organic matter can be carbonized or made to lose progressively its atoms other than carbon to become an artificial carbon material or "carbon". In addition to organic materials, pyrolysis can be applied in

Pyrolysis is an endothermic process. Determination of the overall energy balance and the thermal efficiency of the process is a fundamental step in designing an efficient pyrolysis reactor. The use of renewable energy or solar-thermal power to drive pyrolysis could make the process more economical and carbon neutral [2, 3]. Pyrolysis reactions typically occur at temperatures between 400 and 800°C. As the temperature changes, the product distribution can be altered. Lower pyrolysis temperatures usually produce more liquid and solid products, while higher temperatures favor the production of more gases as a result of more powerful thermal cracking reactions. The pyrolysis temperature has also a significant effect on the properties of the pyrolysis products. The calorific value of the pyrolytic oil, for

The rate of heat transfer also influences the product distribution. In fast pyroly-

While feed particle size may not greatly affect pyrolysis product distribution, larger particle size tends in general to increase the liquid yield at a higher temperature range. Smaller particle sizes on the other hand favor the internal heat transfer within the particles. In fluidized bed reactors, the particles must be greater than a minimum, in order to avoid entrainment of fines, particularly where the material

sis at lower temperatures, higher heating rates and small residence times favor liquid yield as the cracking of larger molecules to produce gaseous products is hindered. Liquid yield is also favored by immediate and rapid quenching which is often used to maximize the production of liquid products by condensing the vapors and gaseous molecules. Intermediate pyrolysis in screw reactors with longer residence time (minutes vs. seconds) can also be used for bio-oil production. In this process, two condensates are usually obtained, an aqueous phase and an organic phase defined as bio-oil. Although the yield of bio-oil is lower compared to fast pyrolysis, the bio-oils produced from intermediate pyrolysis are more stable, contain less oxygen, and have lower molecular weight substances, and the process is easier to control [4]. Slow pyrolysis, on the other hand, can be used to maximize the yield of solid char. This process requires slow pyrolytic decomposition at low temperatures. Pyrolysis may be carried out at atmospheric or higher pressure or in vacuum where uncontrolled combustion is avoided. In practice, however, pyrolysis is mostly carried out at atmospheric pressure as creating a vacuum or high pressure drastically increases the cost of process equipment. Operation under high pressures results generally in greater yields of biochar and gases, while lower pressure or

certain cases to inorganic materials and to water and aqueous solutions.

example, increases mostly with increasing temperature.

vacuum results in increased production of liquid products.

**2**

has a low density [5].

Reactor type is crucial for the efficient production of pyrolysis oil. Reactor types include packed or fixed-bed reactors, rotary kiln reactors and fluidized bed reactors. Fluidized bed reactors in particular, such as the auger, bubbling fluidized bed reactor and the circulating fluidized bed reactor, are highly efficient for the large commercial-scale production of pyrolysis oil [6].

Fluidized and fixed-bed reactors are mostly exterior-heating pyrolysis reactors where heat is transmitted from the exterior surface to the interior of the material. In fluidized bed reactors, fluidization increases mixing and interaction leading to efficient heat transfer, uniform temperatures, improved reaction rates and higher yield of bio-oil. On the other hand, interior heating is utilized in microwave-assisted pyrolysis with high energy effectiveness and the production of uniform products. Unlike traditional heating, microwave heating provides quick quenching of the pyrolysis vapors, which avoids secondary decomposition reactions of the primary products.

A catalyst may be used in catalytic pyrolysis processes to improve the yield and lower the temperature and/or time of reaction. Aromatic hydrocarbons such as benzene, toluene and xylenes may be directly produced by catalytic pyrolysis of biomass [7, 8].

A pyrolysis-based process has several advantages over other treatment processes:


## **2. Industrial applications of pyrolysis**

Pyrolysis is a proven and energetically efficient chemical technology that is used heavily in the chemical industry. Pyrolysis may be used in biorefineries for making a wide range of products and materials on which a future sustainable society may be based including many forms of carbon, fuels and other potentially valuable chemicals and chemical feedstocks.

There are a great many pyrolysis processes used in the production of fuels and chemicals. Such processes differ in the type of process, the use of catalysts, the substances treated and the end products. Pyrolysis processes include catalytic and noncatalytic pyrolysis, hydrous pyrolysis, vacuum pyrolysis, slow pyrolysis, torrefaction, fast pyrolysis, fluidized bed pyrolysis, flash pyrolysis, microwave-induced pyrolysis, plasma pyrolysis, empty tube pyrolysis, on-line pyrolysis and ultrasonic spray pyrolysis (USP). Other pyrolysis processes include also thermal decomposition, destructive and dry distillation, charring, tyre recycling and pyrolysis, liquefaction, high- and low-temperature carbonization, coking and thermal and catalytic cracking.

Common pyrolysis methods are frequently associated with many disadvantages including low gas yield, reducing the total energy value of the gas, and high content of tar in the gas, causing corrosion problems in the gas collection equipment and increasing the need for further treatment of the gas produced [6, 10, 11]. The disadvantages of the traditional pyrolysis methods may be overcome by radio-frequency plasma pyrolysis technology or by adding catalysts and steam.

Compared with noncatalytic pyrolysis, catalytic pyrolysis increases the pyrolytic gas and char yields but decreases the amount of oil [12]. The hydrogen concentration of the pyrolytic gas can also be considerably increased by the use of some catalysts [13]. The effect of the use of catalysts on the pyrolytic gas yield was investigated by Chen et al. It was found that some catalysts, particularly chromium oxide, have a strong positive influence on the pyrolytic gas, while other catalysts such as CuO even inhibits the pyrolytic gas yield [14]. Catalytic pyrolysis affects also the chemical composition and characteristics of the bio-oil produced. With catalytic biomass pyrolysis, the need for costly condensation and re-evaporation procedures prior to bio-oil upgrading is essentially eliminated [15, 16]. The effect of the catalysts on the yields and structure of products, however, becomes less significant with increasing temperature [17, 18].

Hydrogen may also be used in the pyrolysis process to enhance the chemical reduction and suppress oxidation by the elemental oxygen in the feedstock. The use of hydrogen can also change the pyrolysis products distribution.

Different catalysts may be used in different catalytic processes including Pt–Rh alloy, nickel-based catalysts, chromium oxide, Co/Mo/Al2O3, solid phosphoric acid and zeolite [19]. In a study conducted on biomass pyrolysis in a fixed-bed reactor, chromium oxide was used leading to gas yield improvement [14]. Oxygenated products can be reduced by utilizing zeolite-type catalysts [20]. Because of their high surface area and regular pore structures, mesoporous zeolites tend to inhibit repolymerization reactions [21, 22]. Zeolite catalyst was used in a catalytic pyrolysis process for the production of bio-oil from rice straw in a fluidized bed reactor. The water content in the bio-oil increased due to deoxygenation, and the aromatic compounds and the calorific value were also increased [12].

In hydrous or steam pyrolysis, organic materials are decomposed in the presence of superheated water or steam. The use of water as a pyrolyzing media also allows the feedstock to be introduced into the reactor in an aqueous form. The use of steam allows pyrolysis to occur at lower temperatures and higher pressures. In general, hydrous pyrolysis gives cleaner carbon with better properties and a relatively high surface area and porosity that are similar in nature to activated charcoal. The oil produced, however, contains high sulfur content and should normally be desulphurized. The C/H ratio of the pyrolytic oil is somewhat higher than that found for petroleumderived fuels. This ratio indicates that such oil is a mixture of aliphatic and aromatic compounds. There is evidence to indicate that increasing the steam ratio (kg of steam/kg of biomass) leads to an almost linear increase of the calorific value of the biogas and an equally linear decrease in the calorific value of the biochar.

**5**

*Introductory Chapter: Pyrolysis*

mostly below 10 mg/Nm3

and CO2.

can enhance the decomposition of tar [27].

ing point and also to avoid adverse chemical reactions.

heating rates commonly applied in torrefaction.

shaped particles during grinding or milling [29].

*DOI: http://dx.doi.org/10.5772/intechopen.90366*

Bio-oils and fuels can be produced by hydrous pyrolysis of rice straw and other biomass materials. Steam cracking of petroleum oils can be used for the production of different cracking chemicals such as ethylene, which is a compound used for the

, can be achieved because high-energy species, such as

According to Tu et al., radio-frequency plasma pyrolysis technology can overcome the disadvantages of common pyrolysis methods [23]. This is a capacitive dielectric heating method which employs an alternating current with high frequency and voltage to build up an electromagnetic field that produces plasma to induce the target material resulting in vigorous colliding, rubbing and thus self-heating. As the material is heated under a suitable degree of vacuum, pyrolysis occurs. The many advantages of this method include high heating rate, short heating time to reach the setting temperature, low heat loss, high concentration of syngas and low residual tar [5, 9, 24–27]. The high heating rate can efficiently decompose the combustible solid to gas products of H2, CO, CH4 and low carbon hydrocarbons such as C2–C5 [23]. The low concentration of tar in the gas phase,

electrons, ions, atoms and free radicals, produced from the radio-frequency plasma

In vacuum pyrolysis, the organic material is heated in vacuum to reduce its boil-

In slow, or conventional, pyrolysis, the feedstock is heated slowly at a low heating rate (0.1 to 2°C per second) to low temperatures (<400°C) for a long period of time. During slow pyrolysis of biomass, the biomass is slowly devolatilized leading to the production of tar and char as the main products. The gas produced consists mainly of methane along with minor amounts of hydrogen, propane, ethylene, CO

Torrefaction, also known as mild pyrolysis, is an example of a slow pyrolysis process. Torrefaction of biomass is a mild form of pyrolysis carried out under atmospheric conditions and at temperatures typically ranging between 200 and 320°C, where the onset of primary pyrolysis occurs at 200°C. For the low temperatures applied in torrefaction, the warm-up period is relatively short, even for the low

Torrefaction serves to improve the properties of biomass in relation to thermochemical processing techniques for energy generation such as combustion, co-combustion with coal or gasification. Torrefaction also eliminates all biological activity reducing the risk of fire and stopping biological decomposition. About 10% of the energy content in the biomass is lost as a result of the torrefaction process, but this energy of the volatiles can be used as a heating fuel for the process itself. During torrefaction, moisture and low-weight organic volatile components are removed, and the biomass loses typically 20% of its mass (dry bone basis). In addition, torrefaction partly depolymerizes the biopolymers (cellulose, hemicellulose and lignin) and the long polysaccharide chains, producing a hydrophobic, dry, blackened solid product as "torrefied biomass" or "bio-coal" with an increased energy density (on a mass basis) and greatly increased grindability. As a result, significantly lower energy is required to process the torrefied fuel, and it no longer requires separate handling facilities when co-fired with coal in existing power stations [20]. Torrefied or so-called roasted wood has found applications as a barbecue fuel and firelighter [28]. Finally, it has been suggested that torrefied biomass is a suitable feedstock for systems previously not considered feasible for raw biomass solid fuels such as entrained flow gasification. This is because torrefied biomass forms more spherical-

In fast pyrolysis, on the other hand, the organic materials are rapidly heated at 450–600°C in the absence of air in which fast heat transfer (100–1000°C/s) is

production of many polymers and antifreeze (ethylene glycol).

#### *Introductory Chapter: Pyrolysis DOI: http://dx.doi.org/10.5772/intechopen.90366*

*Recent Advances in Pyrolysis*

catalytic cracking.

There are a great many pyrolysis processes used in the production of fuels and chemicals. Such processes differ in the type of process, the use of catalysts, the substances treated and the end products. Pyrolysis processes include catalytic and noncatalytic pyrolysis, hydrous pyrolysis, vacuum pyrolysis, slow pyrolysis, torrefaction, fast pyrolysis, fluidized bed pyrolysis, flash pyrolysis, microwave-induced pyrolysis, plasma pyrolysis, empty tube pyrolysis, on-line pyrolysis and ultrasonic spray pyrolysis (USP). Other pyrolysis processes include also thermal decomposition, destructive and dry distillation, charring, tyre recycling and pyrolysis, liquefaction, high- and low-temperature carbonization, coking and thermal and

Common pyrolysis methods are frequently associated with many disadvantages including low gas yield, reducing the total energy value of the gas, and high content of tar in the gas, causing corrosion problems in the gas collection equipment and increasing the need for further treatment of the gas produced [6, 10, 11]. The disadvantages of the traditional pyrolysis methods may be overcome by radio-frequency

Compared with noncatalytic pyrolysis, catalytic pyrolysis increases the pyrolytic gas and char yields but decreases the amount of oil [12]. The hydrogen concentration of the pyrolytic gas can also be considerably increased by the use of some catalysts [13]. The effect of the use of catalysts on the pyrolytic gas yield was investigated by Chen et al. It was found that some catalysts, particularly chromium oxide, have a strong positive influence on the pyrolytic gas, while other catalysts such as CuO even inhibits the pyrolytic gas yield [14]. Catalytic pyrolysis affects also the chemical composition and characteristics of the bio-oil produced. With catalytic biomass pyrolysis, the need for costly condensation and re-evaporation procedures prior to bio-oil upgrading is essentially eliminated [15, 16]. The effect of the catalysts on the yields and structure of products, however, becomes less signifi-

Hydrogen may also be used in the pyrolysis process to enhance the chemical reduction and suppress oxidation by the elemental oxygen in the feedstock. The use

Different catalysts may be used in different catalytic processes including Pt–Rh alloy, nickel-based catalysts, chromium oxide, Co/Mo/Al2O3, solid phosphoric acid and zeolite [19]. In a study conducted on biomass pyrolysis in a fixed-bed reactor, chromium oxide was used leading to gas yield improvement [14]. Oxygenated products can be reduced by utilizing zeolite-type catalysts [20]. Because of their high surface area and regular pore structures, mesoporous zeolites tend to inhibit repolymerization reactions [21, 22]. Zeolite catalyst was used in a catalytic pyrolysis process for the production of bio-oil from rice straw in a fluidized bed reactor. The water content in the bio-oil increased due to deoxygenation, and the aromatic

In hydrous or steam pyrolysis, organic materials are decomposed in the presence of superheated water or steam. The use of water as a pyrolyzing media also allows the feedstock to be introduced into the reactor in an aqueous form. The use of steam allows pyrolysis to occur at lower temperatures and higher pressures. In general, hydrous pyrolysis gives cleaner carbon with better properties and a relatively high surface area and porosity that are similar in nature to activated charcoal. The oil produced, however, contains high sulfur content and should normally be desulphurized. The C/H ratio of the pyrolytic oil is somewhat higher than that found for petroleumderived fuels. This ratio indicates that such oil is a mixture of aliphatic and aromatic compounds. There is evidence to indicate that increasing the steam ratio (kg of steam/kg of biomass) leads to an almost linear increase of the calorific value of the

plasma pyrolysis technology or by adding catalysts and steam.

of hydrogen can also change the pyrolysis products distribution.

compounds and the calorific value were also increased [12].

biogas and an equally linear decrease in the calorific value of the biochar.

cant with increasing temperature [17, 18].

**4**

Bio-oils and fuels can be produced by hydrous pyrolysis of rice straw and other biomass materials. Steam cracking of petroleum oils can be used for the production of different cracking chemicals such as ethylene, which is a compound used for the production of many polymers and antifreeze (ethylene glycol).

According to Tu et al., radio-frequency plasma pyrolysis technology can overcome the disadvantages of common pyrolysis methods [23]. This is a capacitive dielectric heating method which employs an alternating current with high frequency and voltage to build up an electromagnetic field that produces plasma to induce the target material resulting in vigorous colliding, rubbing and thus self-heating. As the material is heated under a suitable degree of vacuum, pyrolysis occurs. The many advantages of this method include high heating rate, short heating time to reach the setting temperature, low heat loss, high concentration of syngas and low residual tar [5, 9, 24–27]. The high heating rate can efficiently decompose the combustible solid to gas products of H2, CO, CH4 and low carbon hydrocarbons such as C2–C5 [23]. The low concentration of tar in the gas phase, mostly below 10 mg/Nm3 , can be achieved because high-energy species, such as electrons, ions, atoms and free radicals, produced from the radio-frequency plasma can enhance the decomposition of tar [27].

In vacuum pyrolysis, the organic material is heated in vacuum to reduce its boiling point and also to avoid adverse chemical reactions.

In slow, or conventional, pyrolysis, the feedstock is heated slowly at a low heating rate (0.1 to 2°C per second) to low temperatures (<400°C) for a long period of time. During slow pyrolysis of biomass, the biomass is slowly devolatilized leading to the production of tar and char as the main products. The gas produced consists mainly of methane along with minor amounts of hydrogen, propane, ethylene, CO and CO2.

Torrefaction, also known as mild pyrolysis, is an example of a slow pyrolysis process. Torrefaction of biomass is a mild form of pyrolysis carried out under atmospheric conditions and at temperatures typically ranging between 200 and 320°C, where the onset of primary pyrolysis occurs at 200°C. For the low temperatures applied in torrefaction, the warm-up period is relatively short, even for the low heating rates commonly applied in torrefaction.

Torrefaction serves to improve the properties of biomass in relation to thermochemical processing techniques for energy generation such as combustion, co-combustion with coal or gasification. Torrefaction also eliminates all biological activity reducing the risk of fire and stopping biological decomposition. About 10% of the energy content in the biomass is lost as a result of the torrefaction process, but this energy of the volatiles can be used as a heating fuel for the process itself. During torrefaction, moisture and low-weight organic volatile components are removed, and the biomass loses typically 20% of its mass (dry bone basis). In addition, torrefaction partly depolymerizes the biopolymers (cellulose, hemicellulose and lignin) and the long polysaccharide chains, producing a hydrophobic, dry, blackened solid product as "torrefied biomass" or "bio-coal" with an increased energy density (on a mass basis) and greatly increased grindability. As a result, significantly lower energy is required to process the torrefied fuel, and it no longer requires separate handling facilities when co-fired with coal in existing power stations [20]. Torrefied or so-called roasted wood has found applications as a barbecue fuel and firelighter [28]. Finally, it has been suggested that torrefied biomass is a suitable feedstock for systems previously not considered feasible for raw biomass solid fuels such as entrained flow gasification. This is because torrefied biomass forms more sphericalshaped particles during grinding or milling [29].

In fast pyrolysis, on the other hand, the organic materials are rapidly heated at 450–600°C in the absence of air in which fast heat transfer (100–1000°C/s) is

#### *Recent Advances in Pyrolysis*

applied. Achieving very high heating and heat transfer rates during pyrolysis usually requires a finely ground biomass feed. Fast pyrolysis is a well-known technique for the production of high-volatile products. Due to the short vapor residence times, products are high-quality ethylene-rich gases which can be used subsequently to produce alcohols or gasoline. The production of char and tar is considerably less in this process [30, 31].

The fast pyrolysis process has been progressively designed and optimized for producing bio-oils from biomass. A number of essential features are required for the production of bio-oil by fast pyrolysis. These include very high heating rates (1000°C/s), high heat transfer rates (600–1000 W/cm2 ), short vapor residence times (typically less than 2 seconds), lower process temperatures and efficient and rapid quenching of the condensable vapors in order to prevent their cracking and hence maximize oil production [6, 32]. In experiments conducted by Lee et al., the optimum reaction temperature range for the production of bio-oil by fast pyrolysis was found to be 410–510°C [33]. The bio-oil produced by such a process may contain large molecules derived from lignin which adversely affects the bio-oil properties [34, 35].

Catalytic fast pyrolysis can be used to produce aromatics using a range of different lignocellulosic feedstocks. Catalytic fast pyrolysis has several advantages over other biomass conversion processes where pyrolysis reactions can occur in a single reactor using inexpensive aluminosilicate catalysts [36].

With the application of induction heating, a fast pyrolysis process was used for producing valuable products from rice straw, sugarcane bagasse and coconut shell in an externally heated fixed-bed reactor [37]. In one process, the straw is pulverized, dried at 150°C, mixed with other raw materials, press formed at 200°C and finally carbonized at 300–350**°**C [38]. In another process, the biomass mixture, after pulverization and extrusion, is oven dried and carbonized at 600–800**°**C [39].

Infrared radiation is an efficient technique for fast heating processes since the energy from the infrared radiation is directly transferred to the process material. Infrared radiation is used as the heating source for many applications such as food processing, surface heating, solid decomposition and fast pyrolysis of oil shale [40]. In a study by Siramard et al. on the pyrolysis of shale oil in a fixed-bed reactor with infrared heating, it was found that shale oil production is affected by the direction of the infrared beam with higher yield achieved by the cross-current in comparison with the co-current heating. This is to be explained by the fact that the residence time of the volatiles was shorter in the case of the cross-current which led to the reduction of secondary cracking reactions of the volatiles. Reduced pyrolysis pressure was also found to be beneficial to the release of volatiles and the reduction of secondary cracking reactions [40].

Fluidized bed pyrolysis is carried out in a fluidized bed created by passing an upwardly moving carrier gas stream through a bed of the solid particulate substance under appropriate conditions to cause the solid/fluid mixture to behave as a fluid. The use of a carrier gas for fluidization results in a lower calorific value of the biogas produced. A fluidized bed reactor operating at atmospheric pressure at 500°C was used to produce bio-oils from wood feedstocks and rice straw [41]. A circulating fluidized bed reactor with sand used as bed material was used at a gauge pressure of about 5–15 kPa for the production of pyrolysis oil from napier grass (*Pennisetum purpureum*) with a calorific value of 19.79 MJ/kg. The maximum pyrolysis oil production was 37 wt% at 480°C of bed temperature. The oil produced is applicable to steam engines and gas turbine engines but not to diesel engines [42].

Higher efficiency is sometimes achieved by flash pyrolysis, also called anhydrous pyrolysis. In this process, the starting material is finely divided or crushed and quickly heated to between 350 and 500°C for less than 2 seconds, generally in

**7**

*Introductory Chapter: Pyrolysis*

example, in organic synthesis.

such as municipal solid wastes [48].

decreased [45].

*DOI: http://dx.doi.org/10.5772/intechopen.90366*

vacuum in order to decrease the boiling point of the byproducts and avoid adverse chemical reactions. In this process, the insulating char layer that forms at the surface of the reacting particles is continuously removed. This process is used, for

A flash pyrolysis process was developed by Longanbach and Bauer to produce liquid fuels, chars and gases from bituminous and subbituminous coal, municipal refuse, grass straw and other biomass materials. In this process, the biomass material is heated by contact with hot recycle char and carried in gas stream through a reactor where pyrolysis occurs at very short residence times and heat-up rates [43]. A flash pyrolysis process was also developed to convert municipal, industrial and agricultural wastes into pyrolytic oil at near ambient pressure with no need for chemicals or catalysts. At the same time, inorganics were recovered [44].

Microwave heating is an electromagnetic irradiation in the range of wavelengths from 0.01 to 1 m and the equivalent frequency range of 0.3–300 GHz. Normally, the microwave reactors for chemical synthesis and all domestic microwave ovens operate at 2.45 GHz frequency, which corresponds to a wavelength of 12.25 cm. The material which absorbs microwave irradiation is known as microwave dielectrics, and microwave heating is thus referred to sometimes as dielectric heating [45, 46]. Microwave heating has been widely used in many areas of thermochemical treatment of waste materials such as biomass, waste cooking oil and scrap tyres. This is mainly due to its high heating efficiency and easy operation. Microwave heating is an inside heating process that is carried out within the heated sample as a whole. It requires in general less energy input than conventional heating and has in addition other advantages including heating uniformity and shorter heating time [47]. In microwave-induced pyrolysis, focussed heating by microwaves makes the resulting pyrolysis different from the traditional pyrolysis. Microwave-induced pyrolysis does not require in general agitation, fluidization or a high degree of grinding, and, furthermore, it can be used for the treatment of mixed feedstocks

According to Huang et al., higher microwave power levels contribute to higher heating rates and reaction temperatures and can therefore produce a torrefied biomass with higher calorific value and lower H/C and O/C ratios [49]. The suitable microwave power levels proposed by Wang et al. are to be set between 250 and 300 W for the torrefaction of rice husk and sugarcane residues [50]. In a study by Ahmad et al., torrefied palm kernel shell had the highest calorific value at the microwave power level of 450 W. However, when the microwave power level increased from 450 to 600 W, the calorific value of the torrefied mass

A work by Zhu et al. has shown that microwave heating can change the supermolecular structure of lignocellulosic materials [51]. In a study by Huang et al., it was suggested that a hydrogen-rich fuel gas (51–55% H2) can be produced from rice straw using microwave-induced pyrolysis. The major components in the gaseous product were H2, CO2, CO and CH4. Alkanes, polars and low-ringed polycyclic aromatic hydrocarbons were the three primary kinds of compounds in the liquid product. From the viewpoint of energy consumption, close to 60% of the input

Bio-oils of viscosities lower than the viscosity of light and heavy fuel oil and therefore easier to handle and process were obtained by microwave-assisted pyroly-

Microwave heating was also used for the treatment of waste tyres. Experiments

manageable product properties were achieved. Typical products were a solid residue

were run in a batch laboratory scale with an oven operating at a frequency of 2.45 GHz with a variable energy output up to 6 kW. Short pyrolysis time and

energy could be derived and utilized as bioenergy [52].

sis of aspen, canola and corncob feedstocks [41].

#### *Introductory Chapter: Pyrolysis DOI: http://dx.doi.org/10.5772/intechopen.90366*

*Recent Advances in Pyrolysis*

this process [30, 31].

properties [34, 35].

secondary cracking reactions [40].

applied. Achieving very high heating and heat transfer rates during pyrolysis usually requires a finely ground biomass feed. Fast pyrolysis is a well-known technique for the production of high-volatile products. Due to the short vapor residence times, products are high-quality ethylene-rich gases which can be used subsequently to produce alcohols or gasoline. The production of char and tar is considerably less in

The fast pyrolysis process has been progressively designed and optimized for producing bio-oils from biomass. A number of essential features are required for the production of bio-oil by fast pyrolysis. These include very high heating rates

times (typically less than 2 seconds), lower process temperatures and efficient and rapid quenching of the condensable vapors in order to prevent their cracking and hence maximize oil production [6, 32]. In experiments conducted by Lee et al., the optimum reaction temperature range for the production of bio-oil by fast pyrolysis was found to be 410–510°C [33]. The bio-oil produced by such a process may contain large molecules derived from lignin which adversely affects the bio-oil

Catalytic fast pyrolysis can be used to produce aromatics using a range of different lignocellulosic feedstocks. Catalytic fast pyrolysis has several advantages over other biomass conversion processes where pyrolysis reactions can occur in a single

With the application of induction heating, a fast pyrolysis process was used for producing valuable products from rice straw, sugarcane bagasse and coconut shell in an externally heated fixed-bed reactor [37]. In one process, the straw is pulverized, dried at 150°C, mixed with other raw materials, press formed at 200°C and finally carbonized at 300–350**°**C [38]. In another process, the biomass mixture, after pulverization and extrusion, is oven dried and carbonized at 600–800**°**C [39]. Infrared radiation is an efficient technique for fast heating processes since the energy from the infrared radiation is directly transferred to the process material. Infrared radiation is used as the heating source for many applications such as food processing, surface heating, solid decomposition and fast pyrolysis of oil shale [40]. In a study by Siramard et al. on the pyrolysis of shale oil in a fixed-bed reactor with infrared heating, it was found that shale oil production is affected by the direction of the infrared beam with higher yield achieved by the cross-current in comparison with the co-current heating. This is to be explained by the fact that the residence time of the volatiles was shorter in the case of the cross-current which led to the reduction of secondary cracking reactions of the volatiles. Reduced pyrolysis pressure was also found to be beneficial to the release of volatiles and the reduction of

Fluidized bed pyrolysis is carried out in a fluidized bed created by passing an upwardly moving carrier gas stream through a bed of the solid particulate substance under appropriate conditions to cause the solid/fluid mixture to behave as a fluid. The use of a carrier gas for fluidization results in a lower calorific value of the biogas produced. A fluidized bed reactor operating at atmospheric pressure at 500°C was used to produce bio-oils from wood feedstocks and rice straw [41]. A circulating fluidized bed reactor with sand used as bed material was used at a gauge pressure of about 5–15 kPa for the production of pyrolysis oil from napier grass (*Pennisetum purpureum*) with a calorific value of 19.79 MJ/kg. The maximum pyrolysis oil production was 37 wt% at 480°C of bed temperature. The oil produced is applicable

to steam engines and gas turbine engines but not to diesel engines [42].

Higher efficiency is sometimes achieved by flash pyrolysis, also called anhydrous pyrolysis. In this process, the starting material is finely divided or crushed and quickly heated to between 350 and 500°C for less than 2 seconds, generally in

), short vapor residence

(1000°C/s), high heat transfer rates (600–1000 W/cm2

reactor using inexpensive aluminosilicate catalysts [36].

**6**

vacuum in order to decrease the boiling point of the byproducts and avoid adverse chemical reactions. In this process, the insulating char layer that forms at the surface of the reacting particles is continuously removed. This process is used, for example, in organic synthesis.

A flash pyrolysis process was developed by Longanbach and Bauer to produce liquid fuels, chars and gases from bituminous and subbituminous coal, municipal refuse, grass straw and other biomass materials. In this process, the biomass material is heated by contact with hot recycle char and carried in gas stream through a reactor where pyrolysis occurs at very short residence times and heat-up rates [43]. A flash pyrolysis process was also developed to convert municipal, industrial and agricultural wastes into pyrolytic oil at near ambient pressure with no need for chemicals or catalysts. At the same time, inorganics were recovered [44].

Microwave heating is an electromagnetic irradiation in the range of wavelengths from 0.01 to 1 m and the equivalent frequency range of 0.3–300 GHz. Normally, the microwave reactors for chemical synthesis and all domestic microwave ovens operate at 2.45 GHz frequency, which corresponds to a wavelength of 12.25 cm. The material which absorbs microwave irradiation is known as microwave dielectrics, and microwave heating is thus referred to sometimes as dielectric heating [45, 46].

Microwave heating has been widely used in many areas of thermochemical treatment of waste materials such as biomass, waste cooking oil and scrap tyres. This is mainly due to its high heating efficiency and easy operation. Microwave heating is an inside heating process that is carried out within the heated sample as a whole. It requires in general less energy input than conventional heating and has in addition other advantages including heating uniformity and shorter heating time [47]. In microwave-induced pyrolysis, focussed heating by microwaves makes the resulting pyrolysis different from the traditional pyrolysis. Microwave-induced pyrolysis does not require in general agitation, fluidization or a high degree of grinding, and, furthermore, it can be used for the treatment of mixed feedstocks such as municipal solid wastes [48].

According to Huang et al., higher microwave power levels contribute to higher heating rates and reaction temperatures and can therefore produce a torrefied biomass with higher calorific value and lower H/C and O/C ratios [49]. The suitable microwave power levels proposed by Wang et al. are to be set between 250 and 300 W for the torrefaction of rice husk and sugarcane residues [50]. In a study by Ahmad et al., torrefied palm kernel shell had the highest calorific value at the microwave power level of 450 W. However, when the microwave power level increased from 450 to 600 W, the calorific value of the torrefied mass decreased [45].

A work by Zhu et al. has shown that microwave heating can change the supermolecular structure of lignocellulosic materials [51]. In a study by Huang et al., it was suggested that a hydrogen-rich fuel gas (51–55% H2) can be produced from rice straw using microwave-induced pyrolysis. The major components in the gaseous product were H2, CO2, CO and CH4. Alkanes, polars and low-ringed polycyclic aromatic hydrocarbons were the three primary kinds of compounds in the liquid product. From the viewpoint of energy consumption, close to 60% of the input energy could be derived and utilized as bioenergy [52].

Bio-oils of viscosities lower than the viscosity of light and heavy fuel oil and therefore easier to handle and process were obtained by microwave-assisted pyrolysis of aspen, canola and corncob feedstocks [41].

Microwave heating was also used for the treatment of waste tyres. Experiments were run in a batch laboratory scale with an oven operating at a frequency of 2.45 GHz with a variable energy output up to 6 kW. Short pyrolysis time and manageable product properties were achieved. Typical products were a solid residue

#### *Recent Advances in Pyrolysis*

containing up to 92% of carbon, a low-viscosity oil with a high calorific value and a gas containing light hydrocarbons, hydrogen and only traces of N2 [53].

In empty tube pyrolysis, a heated alumina or nickel tube is used in which the samples are injected. This method was developed simultaneously by two groups working at the Scottish Crop Research Institute and at Indiana University.

In ultrasonic spray pyrolysis (USP), an ultrasonic nozzle is utilized for fine chemical synthesis such as the synthesis of nanoparticles, zirconia and oxides.

Liquefaction is the thermochemical conversion of an organic solid into a liquid composed of heavy molecular compounds with characteristics similar to petroleum-based liquids such as fuel oils. Liquefaction may also involve the production of a liquid from a pyrolytic gas stream.

The materials treated by pyrolysis include:


## **3. Other applications of pyrolysis**

In addition to being a production process of chemicals and fuels, pyrolysis can be used for other purposes such as carbon-14 dating, thermal decomposition, thermal cleaning and removing of contaminants and for analysis and identification purposes as well. Pyrolysis can also be used as a pretreatment for more conventional techniques, such as incineration, gasification or steam reforming. Thermal decomposition reactions are the basis of reforming processes in the oil refining industry used to improve the combustion characteristics of gasoline and increase its octane number. In the petrochemical industry, reforming is used mainly to produce aromatic compounds which are used as feedstocks. In the treatment of plastic waste, a dual process of pyrolysis followed by steam reforming of the pyrolytic products is used for the production of gaseous fuels and hydrogen. Pyrolysis may also be used to coat a preformed substrate with a layer of pyrolytic carbon. This is typically done in a fluidized bed reactor heated to 1000–2000°C. Pyrolytic carbon coatings are used in many applications, including artificial heart valves.

A common process of thermal cleaning that is of particular interest in the oil and petrochemical industry is thermal desulphurization. Thermal desulphurization is the process where the substance to be treated is heated under atmospheric pressure in an inert atmosphere to a specified temperature and then kept at that temperature for a specified period of time. Most organic sulfur compounds undergo thermal decomposition at elevated temperatures, but some sulfur compounds decompose at lower temperatures such as many mercaptans which decompose at about 600 K and some sulphides which decompose at 530–670 K [26]. This process was found to be the most practical process for the desulphurization of petcoke and can be the only one possible when other techniques prove to be difficult or inefficient as was found in at least one case with Syrian petcoke [55].

**9**

**Author details**

Hassan Al-Haj Ibrahim

Arab University for Science and Technology, Hamah, Syria

provided the original work is properly cited.

\*Address all correspondence to: sanjim84@yahoo.com; hasahi123@hotmail.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Introductory Chapter: Pyrolysis*

*DOI: http://dx.doi.org/10.5772/intechopen.90366*

*Introductory Chapter: Pyrolysis DOI: http://dx.doi.org/10.5772/intechopen.90366*

*Recent Advances in Pyrolysis*

a liquid from a pyrolytic gas stream.

The materials treated by pyrolysis include:

• Liquid materials such as petroleum fractions.

used in many applications, including artificial heart valves.

in at least one case with Syrian petcoke [55].

**3. Other applications of pyrolysis**

containing up to 92% of carbon, a low-viscosity oil with a high calorific value and a

In empty tube pyrolysis, a heated alumina or nickel tube is used in which the samples are injected. This method was developed simultaneously by two groups working at the Scottish Crop Research Institute and at Indiana University.

In ultrasonic spray pyrolysis (USP), an ultrasonic nozzle is utilized for fine chemical synthesis such as the synthesis of nanoparticles, zirconia and oxides.

Liquefaction is the thermochemical conversion of an organic solid into a liquid composed of heavy molecular compounds with characteristics similar to petroleum-based liquids such as fuel oils. Liquefaction may also involve the production of

• Solid materials such as oil shale, coal, wood, woody and herbaceous biomass and organic, agricultural and municipal solid waste materials including straw, animal dung and human fecal waste, waste plastics and even waste printed circuit boards. Rice straw in particular has several characteristics that make it an attractive lignocellulosic material for bioethanol production, such as high cellulose and hemicellulose content that can be readily hydrolysed into fermentable sugars. The high ash and silica content of rice straw, however, makes the selection of an appropriate pretreatment technique a major challenge in developing an economically viable technology for bioethanol production [54].

In addition to being a production process of chemicals and fuels, pyrolysis can be used for other purposes such as carbon-14 dating, thermal decomposition, thermal cleaning and removing of contaminants and for analysis and identification purposes as well. Pyrolysis can also be used as a pretreatment for more conventional techniques, such as incineration, gasification or steam reforming. Thermal decomposition reactions are the basis of reforming processes in the oil refining industry used to improve the combustion characteristics of gasoline and increase its octane number. In the petrochemical industry, reforming is used mainly to produce aromatic compounds which are used as feedstocks. In the treatment of plastic waste, a dual process of pyrolysis followed by steam reforming of the pyrolytic products is used for the production of gaseous fuels and hydrogen. Pyrolysis may also be used to coat a preformed substrate with a layer of pyrolytic carbon. This is typically done in a fluidized bed reactor heated to 1000–2000°C. Pyrolytic carbon coatings are

A common process of thermal cleaning that is of particular interest in the oil and petrochemical industry is thermal desulphurization. Thermal desulphurization is the process where the substance to be treated is heated under atmospheric pressure in an inert atmosphere to a specified temperature and then kept at that temperature for a specified period of time. Most organic sulfur compounds undergo thermal decomposition at elevated temperatures, but some sulfur compounds decompose at lower temperatures such as many mercaptans which decompose at about 600 K and some sulphides which decompose at 530–670 K [26]. This process was found to be the most practical process for the desulphurization of petcoke and can be the only one possible when other techniques prove to be difficult or inefficient as was found

gas containing light hydrocarbons, hydrogen and only traces of N2 [53].

**8**

## **Author details**

Hassan Al-Haj Ibrahim Arab University for Science and Technology, Hamah, Syria

\*Address all correspondence to: sanjim84@yahoo.com; hasahi123@hotmail.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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[30] Meyers RA. Coal desulphurization. New York: Marcel Dekker; 1977

[31] Gibbins-Matham J, Kandiyoti R. Coal pyrolysis yields from fast and slow heating in a wire-mesh apparatus with a gas sweep. Energy & Fuels. 1988;**2**:505-511

[32] Bayerbach R, Meier D. Journal of Analytical and Applied Pyrolysis. 2009;**85**:98-107

[33] Lee K et al. Influence of reaction temperature, pretreatment, and a char removal system on the production of bio-oil from Rice straw by fast pyrolysis, using a fluidized bed. Energy & Fuels. 2005;**19**(5):2179-2184

[34] Lédé J et al. Properties of bio-oils produced by biomass fast pyrolysis in a cyclone reactor. Fuel. 2007;**86**(11-12):1800-1810

[35] Oasmaa A, Kuoppala E. Fast pyrolysis of forestry residue. 3. Storage stability of liquid fuel. Energy Fuel. 2003;**17**:1075-1084

[36] Fosteret AJ et al. optimizing the aromatic yield and distribution from catalytic fast pyrolysis of biomass over ZSM-5. Applied Catalysis A: General. 2012;**423**:154-161

[37] Tsai WT et al. Fast pyrolysis of rice straw, sugarcane bagasse and coconut shell in an induction-heating reactor. Journal of Analytical and Applied Pyrolysis. 2006;**76**(1-2):230-237

[38] Zhang L, Wang G. Method for preparation of solid fuel briquets from straw. China Patent No. CN 1699525; 2004

**10**

1980;**4**:713-720

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2018;**79**:214-222

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[12] Choi JC et al. Bio-oil production from rice straw by the catalytic pyrolysis

[13] Chen G et al. Catalytic pyrolysis of biomass for hydrogen rich fuel gas production. Energy Conversion and Management. 2003;**44**(14):2289-2296

application to biomass pyrolysis in a fixed bed reactor. Energy Sources.

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& Fuels. 2000;**14**:1161-1167

Reviews. 2010;**14**:233-248

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[16] Samolada MC. Catalyst evaluation for catalytic biomass pyrolysis. Energy

[17] Panda AK et al. Thermolysis of waste plastics to liquid fuel, a suitable method for plastic waste management and manufacture of value added products—A world prospective. Renewable and Sustainable Energy

[18] Miskolczi N et al. Thermal and thermo-catalytic degradation of highdensity polyethylene waste. Journal of Analytical and Applied Pyrolysis.

[19] Morris M. Production of bio-oils via catalytic pyrolysis. In: Handbook of Biofuels Production. Elsevier: Woodhead Publishing Series in Energy;

over zeolites. Hwahak Konghak.

[14] Chen G et al. Catalytic

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[2] Yacob TW et al. Pyrolysis of human feces: Gas yield analysis and kinetic modelling. Waste Management.

[3] Lichty P. Rapid high temperature solar thermal biomass gasification in a prototype cavity reactor. Journal

of Solar Energy Engineering.

[4] Boscagli C et al. Influence of feedstock, catalyst, pyrolysis and hydrotreatment temperature on the composition of upgraded oils from intermediate pyrolysis. Biomass and

Bioenergy. 2018;**116**:236-248

[5] Conesa JA et al. Pyrolysis of

[7] Jae J et al. Depolymerization of lignocellulosic biomass to fuel precursors: Maximizing carbon

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polyethylene in a fluidized bed reactor. Energy & Fuels. 1994;**8**:1238-1246

[6] Bridgwater AV. Renewable fuels and chemicals by thermal processing of biomass. Chemical Engineering Journal.

efficiency by combining hydrolysis with pyrolysis. Energy & Environmental

[8] Thring RW et al. The production of gasoline range hydrocarbons from Alcell lignin using HZSM-5 catalyst. Fuel Processing Technology. 2000;**62**:17-30

[9] Wiens J. Mobile pyrolysis system for on-site biomass conversion to liquid and solid fuels. Symposium Papers: Energy from Biomass and Wastes.

[10] Chen G et al. Biomass pyrolysis/ gasification for product gas production: [39] Shen X. Method for manufacturing solid fuel from cattle manure, straw, and sawdust. China Patent No. CN 101629114; 2010

[40] Siramard S et al. Secondary cracking of volatile and its avoidance in infrared-heating pyrolysis reactor. Carbon Resources Conversion. 2018;**1**(3):202-208

[41] Luo Z et al. Research on biomass fast pyrolysis for liquid fuel. Biomass and Bioenergy. 2004;**26**(5):455-462

[42] Suntivarakorn R et al. Fast pyrolysis from Napier grass for pyrolysis oil production by using circulating fluidized bed reactor: Improvement of pyrolysis system and production cost. Energy Reports. 2018;**4**:565-575

[43] Longanbach JR, Bauer F. Fuels and Chemicals by Pyrolysis, ACS Symposium Series, 1976, 32 (Ind. Lab. Pyrolyses, Symp.)1975. pp. 476-491

[44] Pober K, Bauer H. From garbage to oil. ChemTech. 1977;**7**(3):164-169

[45] Zhu SD et al. Microwave-assisted alkali pre-treatment of wheat straw and its enzymatic hydrolysis. Biosystems Engineering. 2006;**94**(3):437-442

[46] Motasemi F, Afzal MT. A review on the microwave-assisted pyrolysis technique. Renewable and Sustainable Energy Reviews. 2013;**28**:317-330

[47] Cheng J et al. Improvement of coal water slurry property through coal physicochemical modifications by microwave irradiation and thermal heat. Energy & Fuels. 2008;**22**(4):2422-2428

[48] Karunanithy C, Muthukumarappan K. Rheological characterization of bio-oils from pilot scale microwave assisted pyrolysis, Ch. 13. In: Bernardes M, editor. Biofuel's Engineering Process Technology. Intech; 2011. pp. 293-316

[49] Huang YF et al. Microwave torrefaction of rice straw and pennisetum. Bioresource Technology. 2012;**123**:1-7

[50] Wang MJ et al. Microwave-induced torrefaction of rice husk and sugarcane residues. Energy. 2012;**37**(1):177-184

[51] Zhu SD et al. Microwave-assisted alkali pre-treatment of wheat straw and its enzymatic hydrolysis. Process Biochemistry. 2005;**40**(9):3082-3086

[52] Al-Haj Ibrahim H. Bio-energy production from rice straw. Recent Advances in Petrochemical Science. 2018;**5**(5):1-6

[53] Undri A. Microwave pyrolysis of polymeric materials: Waste tires treatment and characterization of the value-added products. Journal of Analytical and Applied Pyrolysis. 2013;**103**:149-158

[54] Al-Haj Ibrahim H. Pretreatment of straw for bioethanol production. Energy Procedia. 2012;**14**:542-551

[55] Al-Haj Ibrahim H, Ali MM. Thermal desulphurization of Syrian petroleum coke. Journal of King Saud University. 2005;**17**(2):199-212

**13**

**Chapter 2**

**Abstract**

A Study on Pyrolysis of Lignin

The aromatics have widespread uses across the chemical industries. Where, the monocyclic aromatics (e.g. BTX) and phenolics compounds are important basic raw materials for several industrial petrochemical processes such as synthetic polymers, detergents, biocides, resins, explosives, etc. Traditional production of these valuable chemicals has been dependent on fossil resources for more than half a century. So, it requires strategies for alternative chemical production from renewable sources especially from nonedible biomass. This chapter presents a review of the recent literature on the fast pyrolysis process for the production of aromatic hydrocarbons using mesoporous catalysts. We focus on the factors that can enhance the yield of aromatics and the lifetime of the catalyst used. Background information on catalyst deactivation during the pyrolysis process was described. The role of mesoporous catalyst's acidity and textural and topological properties of lignin to aromatics

over Mesoporous Materials

*Abdelrahman Mohamed Rabie and* 

*Marwa Mohamed Abouelela*

conversion was also discussed in detail.

**mesoporous catalysts**

**Keywords:** pyrolysis, fast pyrolysis, lignin, mesoporous materials

to bio-oil and high valuable chemical products [10].

bons such as benzene, toluene, and xylenes [1, 3, 11–16].

**1. Fast pyrolysis of lignin for production of aromatic hydrocarbons by** 

Catalytic fast pyrolysis of lignin with catalysts to produce aromatic hydrocarbons has attracted many research interests in recent years. Aromatic hydrocarbons, especially benzene, toluene, ethyl benzene and xylenes (BTEX), are considered to be important and valuable chemicals in the petroleum industry (**Figure 1**) [1–5]. Pyrolysis of lignin is the thermal depolymerization of organic materials in an oxygen-free environment in a temperature range of 300–900°C [6–8]. During the thermal decomposition process, hemicellulose, cellulose, and lignin undergo different reactions, leading to a three-stage reaction: moisture removal, main depolymerization, and biochar formation [9]. Fast pyrolysis is considered one of the most economical and highly efficient technologies to convert biomass and lignin

Catalytic fast pyrolysis (CFP) is a further modification of fast pyrolysis directed toward the production of hydrocarbon fuels. By pyrolyzing biomass in the presence of a catalyst, it is possible to catalyze the direct production of aromatic hydrocar-

Catalytic fast pyrolysis has several advantages over other biomass conversion approaches. (1) All of the desired chemistry can occur in a single reactor using

## **Chapter 2**

*Recent Advances in Pyrolysis*

101629114; 2010

2018;**1**(3):202-208

[39] Shen X. Method for manufacturing solid fuel from cattle manure, straw, and sawdust. China Patent No. CN

[49] Huang YF et al. Microwave torrefaction of rice straw and

2012;**123**:1-7

2018;**5**(5):1-6

2013;**103**:149-158

2005;**17**(2):199-212

Procedia. 2012;**14**:542-551

pennisetum. Bioresource Technology.

[50] Wang MJ et al. Microwave-induced torrefaction of rice husk and sugarcane residues. Energy. 2012;**37**(1):177-184

[51] Zhu SD et al. Microwave-assisted alkali pre-treatment of wheat straw and its enzymatic hydrolysis. Process Biochemistry. 2005;**40**(9):3082-3086

[52] Al-Haj Ibrahim H. Bio-energy production from rice straw. Recent Advances in Petrochemical Science.

[53] Undri A. Microwave pyrolysis of polymeric materials: Waste tires treatment and characterization of the value-added products. Journal of Analytical and Applied Pyrolysis.

[54] Al-Haj Ibrahim H. Pretreatment of straw for bioethanol production. Energy

[55] Al-Haj Ibrahim H, Ali MM. Thermal desulphurization of Syrian petroleum coke. Journal of King Saud University.

[41] Luo Z et al. Research on biomass fast pyrolysis for liquid fuel. Biomass and Bioenergy. 2004;**26**(5):455-462

[42] Suntivarakorn R et al. Fast pyrolysis from Napier grass for pyrolysis oil production by using circulating fluidized bed reactor: Improvement of pyrolysis system and production cost. Energy Reports. 2018;**4**:565-575

[43] Longanbach JR, Bauer F. Fuels and Chemicals by Pyrolysis, ACS Symposium Series, 1976, 32 (Ind. Lab. Pyrolyses, Symp.)1975. pp. 476-491

[44] Pober K, Bauer H. From garbage to oil. ChemTech. 1977;**7**(3):164-169

[45] Zhu SD et al. Microwave-assisted alkali pre-treatment of wheat straw and its enzymatic hydrolysis. Biosystems Engineering. 2006;**94**(3):437-442

[46] Motasemi F, Afzal MT. A review on the microwave-assisted pyrolysis technique. Renewable and Sustainable Energy Reviews. 2013;**28**:317-330

[47] Cheng J et al. Improvement of coal water slurry property through coal physicochemical modifications by microwave irradiation and thermal heat. Energy & Fuels.

[48] Karunanithy C, Muthukumarappan K. Rheological characterization of bio-oils from pilot scale microwave assisted pyrolysis, Ch. 13. In: Bernardes M, editor. Biofuel's Engineering Process Technology. Intech; 2011. pp. 293-316

2008;**22**(4):2422-2428

[40] Siramard S et al. Secondary cracking of volatile and its avoidance in infrared-heating pyrolysis reactor. Carbon Resources Conversion.

**12**

## A Study on Pyrolysis of Lignin over Mesoporous Materials

*Abdelrahman Mohamed Rabie and Marwa Mohamed Abouelela*

## **Abstract**

The aromatics have widespread uses across the chemical industries. Where, the monocyclic aromatics (e.g. BTX) and phenolics compounds are important basic raw materials for several industrial petrochemical processes such as synthetic polymers, detergents, biocides, resins, explosives, etc. Traditional production of these valuable chemicals has been dependent on fossil resources for more than half a century. So, it requires strategies for alternative chemical production from renewable sources especially from nonedible biomass. This chapter presents a review of the recent literature on the fast pyrolysis process for the production of aromatic hydrocarbons using mesoporous catalysts. We focus on the factors that can enhance the yield of aromatics and the lifetime of the catalyst used. Background information on catalyst deactivation during the pyrolysis process was described. The role of mesoporous catalyst's acidity and textural and topological properties of lignin to aromatics conversion was also discussed in detail.

**Keywords:** pyrolysis, fast pyrolysis, lignin, mesoporous materials

## **1. Fast pyrolysis of lignin for production of aromatic hydrocarbons by mesoporous catalysts**

Catalytic fast pyrolysis of lignin with catalysts to produce aromatic hydrocarbons has attracted many research interests in recent years. Aromatic hydrocarbons, especially benzene, toluene, ethyl benzene and xylenes (BTEX), are considered to be important and valuable chemicals in the petroleum industry (**Figure 1**) [1–5].

Pyrolysis of lignin is the thermal depolymerization of organic materials in an oxygen-free environment in a temperature range of 300–900°C [6–8]. During the thermal decomposition process, hemicellulose, cellulose, and lignin undergo different reactions, leading to a three-stage reaction: moisture removal, main depolymerization, and biochar formation [9]. Fast pyrolysis is considered one of the most economical and highly efficient technologies to convert biomass and lignin to bio-oil and high valuable chemical products [10].

Catalytic fast pyrolysis (CFP) is a further modification of fast pyrolysis directed toward the production of hydrocarbon fuels. By pyrolyzing biomass in the presence of a catalyst, it is possible to catalyze the direct production of aromatic hydrocarbons such as benzene, toluene, and xylenes [1, 3, 11–16].

Catalytic fast pyrolysis has several advantages over other biomass conversion approaches. (1) All of the desired chemistry can occur in a single reactor using

**Figure 1.** *Various products of fast pyrolysis of lignin.*

inexpensive aluminosilicate catalysts. (2) Catalytic fast pyrolysis can be used to process a range of different lignocellulosic feedstocks with only simple pretreatment (drying and grinding, for example) prior to reaction. (3) The aromatics produced through catalytic fast pyrolysis can readily be blended into the existing gasoline infrastructure to reduce the use of crude oil [17].

Lignin is an aromatic and optically inactive amorphous heteropolymer, which is often synthesized by free radical assisted peroxidase mediated dehydrogenation of phenylpropanoid precursors, namely coniferyl alcohol, p-coumaryl alcohol, and sinapyl alcohol, joined altogether via non-hydrolysable linkages. The ratios of these three monolignols vary significantly among different plant species. For example, coniferyl alcohol is abundant in soft wood lignin while hard wood lignin comprises both coniferyl and sinapyl alcohols; however, grass lignin contains all three monolignols [18].

## **2. Factors that influence the pyrolysis process**

The bio-oil yield from catalytic fast pyrolysis of lignin differs according to many parameters including kind of the catalyst, reactor types, temperature and the rate of heating, and reaction time, which can be 21 explained in following subdivisions.

## **2.1 Kind of the catalyst**

The catalyst throughout the pyrolysis process causes cracking reactions and improves the quality of biomass pyrolysis products, relying on the operating conditions. The catalyst kind and reactor design play a vital role in the production of primary products during the pyrolysis process. Gaseous and liquid products can be produced by the catalytic cracking of the primary pyrolysis vapors.

Oxygenated products can be reduced by utilizing zeolite-type catalysts [19]. Zeolite-type catalysts have been studied in the pyrolysis process of lignin. Jackson et al. [20] studied the catalytic pyrolysis of lignin over KZSM-5, HZSM-5, solid phosphoric acid, Al-MCM-41, and Co/Mo/Al2O3. Reaction over HZSM-5 generated aromatic compounds (46.7% simple aromatics and 46.2% naphthalenic ring compounds), while reaction over Al-MCM-41 generated 17.3% simple aromatics, 13.5% naphthenic ring compounds, and 66.5% oxygenated aromatics. MCM-41 has

**15**

**Figure 2.**

*A Study on Pyrolysis of Lignin over Mesoporous Materials*

resistance of the molecular diffusion in pores.

its distinctive advantages. It is suitable for macromolecular catalytic reactions due to its larger pore size; it can make adsorption and separation, and it decreases the

introduces enough sites on the surface for adsorption and catalytic reactions of reactive components, and it produces comparatively low char products [10] (**Figure 2**). Mesoporous zeolites catalysts are favorable to inhibit the repolymerization reaction, this because the high surface area and regular pore structures [22, 23], which makes mesoporous supports suitable for the catalytic upgrading of lignocellulose [24]. Mullen and Boateng studied the pyrolysis process of four various lignin sources over CoO/MoO3 and zeolite H-ZSM5 catalysts. They found that the H-ZSM5 catalyst was more active to produce aromatic hydrocarbons from lignin [25]. Ma et al. reported that H-USY has large enough pore size and the produced molecules during the fast pyrolysis process of alkaline lignin were able to penetrate the pores of the zeolite catalyst. The inside reaction could prevent the formation of char [26]. Thepparat et al. compared the influence of NiMo/Al2O3 and mesostructured silica catalysts on the depolymerization reaction of organosolv lignin extracted from woody eucalyptus. They found that MCM-41 and SBA-15 produced the lowest char yield [27].

Reactors, where the pyrolysis process takes place, play an essential role in the yield and composition of bio-oil produced from lignin pyrolysis; this is because it associates with the rate of the heating of the system, method of heat transfer, residence time of volatiles and conversion capacity of lignin. In the fast pyrolysis of lignin, the outside heating pyrolysis reactors and internal heating pyrolysis reactors are used [28].

Fluidized reactor and Fixed-bed reactor are mostly utilized in the outside heating pyrolysis system, in which the heat transmits from the exterior surface to the interior of the material. Fixed-bed reactor consists of a feeding unit, a gas flowing

/g), which

As well, MCM-41 has a large specific surface area (up to 1000 m2

*DOI: http://dx.doi.org/10.5772/intechopen.83785*

**2.2 Reactor types**

**2.3 Exterior heating pyrolysis reactors**

*Catalytic fast pyrolysis using different mesoporous materials [21].*

### *A Study on Pyrolysis of Lignin over Mesoporous Materials DOI: http://dx.doi.org/10.5772/intechopen.83785*

its distinctive advantages. It is suitable for macromolecular catalytic reactions due to its larger pore size; it can make adsorption and separation, and it decreases the resistance of the molecular diffusion in pores.

As well, MCM-41 has a large specific surface area (up to 1000 m2 /g), which introduces enough sites on the surface for adsorption and catalytic reactions of reactive components, and it produces comparatively low char products [10] (**Figure 2**).

Mesoporous zeolites catalysts are favorable to inhibit the repolymerization reaction, this because the high surface area and regular pore structures [22, 23], which makes mesoporous supports suitable for the catalytic upgrading of lignocellulose [24]. Mullen and Boateng studied the pyrolysis process of four various lignin sources over CoO/MoO3 and zeolite H-ZSM5 catalysts. They found that the H-ZSM5 catalyst was more active to produce aromatic hydrocarbons from lignin [25]. Ma et al. reported that H-USY has large enough pore size and the produced molecules during the fast pyrolysis process of alkaline lignin were able to penetrate the pores of the zeolite catalyst. The inside reaction could prevent the formation of char [26]. Thepparat et al. compared the influence of NiMo/Al2O3 and mesostructured silica catalysts on the depolymerization reaction of organosolv lignin extracted from woody eucalyptus. They found that MCM-41 and SBA-15 produced the lowest char yield [27].

## **2.2 Reactor types**

*Recent Advances in Pyrolysis*

inexpensive aluminosilicate catalysts. (2) Catalytic fast pyrolysis can be used to process a range of different lignocellulosic feedstocks with only simple pretreatment (drying and grinding, for example) prior to reaction. (3) The aromatics produced through catalytic fast pyrolysis can readily be blended into the existing gasoline

Lignin is an aromatic and optically inactive amorphous heteropolymer, which is often synthesized by free radical assisted peroxidase mediated dehydrogenation of phenylpropanoid precursors, namely coniferyl alcohol, p-coumaryl alcohol, and sinapyl alcohol, joined altogether via non-hydrolysable linkages. The ratios of these three monolignols vary significantly among different plant species. For example, coniferyl alcohol is abundant in soft wood lignin while hard wood lignin comprises both coniferyl and sinapyl alcohols; however, grass lignin contains all three

The bio-oil yield from catalytic fast pyrolysis of lignin differs according to many parameters including kind of the catalyst, reactor types, temperature and the rate of heating, and reaction time, which can be 21 explained in following subdivisions.

The catalyst throughout the pyrolysis process causes cracking reactions and improves the quality of biomass pyrolysis products, relying on the operating conditions. The catalyst kind and reactor design play a vital role in the production of primary products during the pyrolysis process. Gaseous and liquid products can be

Oxygenated products can be reduced by utilizing zeolite-type catalysts [19]. Zeolite-type catalysts have been studied in the pyrolysis process of lignin. Jackson et al. [20] studied the catalytic pyrolysis of lignin over KZSM-5, HZSM-5, solid phosphoric acid, Al-MCM-41, and Co/Mo/Al2O3. Reaction over HZSM-5 generated aromatic compounds (46.7% simple aromatics and 46.2% naphthalenic ring compounds), while reaction over Al-MCM-41 generated 17.3% simple aromatics, 13.5% naphthenic ring compounds, and 66.5% oxygenated aromatics. MCM-41 has

produced by the catalytic cracking of the primary pyrolysis vapors.

infrastructure to reduce the use of crude oil [17].

*Various products of fast pyrolysis of lignin.*

**2. Factors that influence the pyrolysis process**

monolignols [18].

**Figure 1.**

**2.1 Kind of the catalyst**

**14**

Reactors, where the pyrolysis process takes place, play an essential role in the yield and composition of bio-oil produced from lignin pyrolysis; this is because it associates with the rate of the heating of the system, method of heat transfer, residence time of volatiles and conversion capacity of lignin. In the fast pyrolysis of lignin, the outside heating pyrolysis reactors and internal heating pyrolysis reactors are used [28].

## **2.3 Exterior heating pyrolysis reactors**

Fluidized reactor and Fixed-bed reactor are mostly utilized in the outside heating pyrolysis system, in which the heat transmits from the exterior surface to the interior of the material. Fixed-bed reactor consists of a feeding unit, a gas flowing

**Figure 2.** *Catalytic fast pyrolysis using different mesoporous materials [21].* unit, and a static bed (reaction bed), and a product exit was utilized in reactions that took place between gas phase (gaseous reactants) and solid phase (catalyst bed). Recently, Fixed-bed reactor has been widely used in the pyrolysis process of lignin or biomass. Generally, the heater that supplies the energy for pyrolysis of lignin is the electric furnace [20, 29]. The rate of heating is uneven and the efficiency of heating is low; this is because the furnace is usually attached on the periphery of the fixed bed. So, the yield of bio-oil is low and the end products are less homogenous.

However, fixed bed is appropriate for the catalytic pyrolysis process. Catalytic pyrolysis of lignin can produce High yield of aromatic compounds [30]. This is because the primary products from catalytic pyrolysis of lignin necessarily pass through the long catalytic bed (static bed), introducing more contacting opportunity for pyrolysis vapors and catalyst. Fluidized-bed reactor supplies more enormous heating for the pyrolysis process compared to fixed-bed reactor. Fluidized-bed reactor is a chamber that facilitates the mixing of gas substrates or liquid with solid particles acting as a fluid. The fluidization increases the mixing and interaction among gas and particles, resulting in efficient heat transfer symmetric temperature, and superb reaction rate.

The pyrolysis process of lignin in fluidized-bed reactor produced higher yield of bio-oil. In addition, the pyrolysis process of lignin in fluidized bed reactor produces lower guaiacols compared to the pyrolysis process in fixed-bed reactor. Even though the selectivity relies on diverse factors such as reaction conditions and the source of lignin, the high heat transfer effectiveness of fluidized-bed also secures equal high temperature during the pyrolysis process, which is contributory to demethoxylation reaction of lignin [31]. Anyhow, fluidized-bed reactor has some flaws for the pyrolysis process of lignin. The highest temperature was noticed nearly in the upper border of the bed [32] because of the continuous reaction of pyrolysis vapors in the part, indicating that undesirable side reaction happens out of the fluidized bed and in completed pyrolysis reaction in the cell of the fluidized bed, which could produce more of undesirable by-products. So, it was noticed that the most desired products were commonly gotten at the half length of the reactor [33].

#### **2.4 Interior heating pyrolysis reactors**

In fluidized bed and fixed reactors, furnace, catalyst, and hot gases are utilized as heating media, which provide the energy to the substance from the exterior surface to the interior center. These ineffectual traditional pyrolysis processes are usually producing low yield of bio-oil with low quality. Nowadays, microwave technology introduces unprecedented techniques for pyrolysis. Microwave radiation produces energy as a result of the interaction among polar molecules present in the material and electromagnetic field; the heat transmits from the interior to the exterior surface of the substance [34]. Microwave-assisted pyrolysis indicates high energy effectiveness and supplies identical interior heating. Pyrolysis process by microwave produces uniform products due to the distinctive thermal gradients [35].

Unlike traditional heating, microwave heating provides quick quenching of pyrolysis vapors, which avoid the second decomposition reactions of the primary products. Compared to pyrolysis by electric heating, the pyrolysis process by microwave assists the production of phenolic compounds from lignin [36]. In addition, esters and hydrocarbons in bio-oil steeply rose compared to that gained from electric-heating pyrolysis due to the formation of hot points formed by microwave heating, which facilitates the conversion of guaiacols to gases such CO and H2 [37].

**17**

gas yield.

time.

**2.6 Effect of the reaction time**

**2.7 Effect of lignin source**

was achieved at 600°C.

*A Study on Pyrolysis of Lignin over Mesoporous Materials*

Temperature has a crucial effect in the catalytic fast pyrolysis of lignin. To decease the secondary reactions of primary vapors which decline the yield and quality of liquid products, a quick heating and cooling of primary vapors should be used [38]. As well as, the slow heating rate produces high yield of char [39]. Temperature has a vital influence on the yield of char and its properties. High temperatures lead to lower yield of char in all of pyrolysis reactions. The first cause for this is the removing of many volatile substances from the char at high temperatures, resulting in a decline in the char yield. For instance, the char yield declines from 31 to 17% with a rise in the temperature from 638K to 879K [40]. Low temperatures lead to imperfect decomposition of biomass resulting in a high quantity of unpyrolyzed solid materials in char content. Also, temperature has an influence on the composition of the char, chars obtained at high temperatures having high carbon content [41, 42]. At the temperatures higher than 773K,The char contains more than 85wt% carbon [43]. The yield of Liquid products increases by raising the pyrolysis temperatures up to an extreme value, at 673– 823 K, but it greatly relies on other operating factors. For a diverse of feedstock sorts, it has been studied that the extreme yield of pyrolysis oil is produced at temperatures of about 673–823 K with a constant decline in char yield and rise in

The time when the biomass was sustained at a specific pyrolysis temperature is the reaction time. In batch systems, the reaction time must be adequate to achieve the required result in the process. Secondary reactions of primary vapors can occur under long reaction time such as carbonization, thermal cracking, and gasification that lead low bio-oil yield [44, 45]. As well as, the reaction time is essential for the reactor configuration step. Tsai et al. [45] studied the pyrolysis process of rice husk in fixed bed reactor, they observed That, the bio-oil yield rose by rising the reaction time from 1 min to 2 min. However, the yields after that were noticed to decline slightly at long holding

The source of lignin and method of isolation have a great impact on the pyrolysis process and the distribution of pyrolysis products. Wang et al. [46] studied the pyrolysis process of various four sorts of lignin, Klason lignin (KL), alkali lignin (AL), milled wood lignin (MWL), and organosolv lignin (OL), separated from the same pine wood, by TG-FTIR and Py-GC/MS as well as 13C NMR spectroscopy. The 13C NMR indicated chemical structure of these separated lignin's is diverse. Ether bonds such as ß-O-4 have lower thermal stability and can decompose readily at low temperatures. So, lignin's containing more ether bonds could show weaker thermal stability. Alkali lignin and milled wood lignin, because they contain more ß-O-4 bonds in their structures, have a lower temperature at maximum weight loss rate (346 and 359°C, respectively) than OL (396°C) or KL (405°C). So, the pyrolysis process of AL and MWL produced more phenolic compounds at lower temperatures. The predominate products in pyrolysis of these softwood lignin's are guaiacyl-type compounds due to shortage of syringyl-type unit in the structure of softwood and the highest yield of phenol

*DOI: http://dx.doi.org/10.5772/intechopen.83785*

**2.5 Temperature and the rate of heating**

## **2.5 Temperature and the rate of heating**

*Recent Advances in Pyrolysis*

less homogenous.

metric temperature, and superb reaction rate.

were commonly gotten at the half length of the reactor [33].

**2.4 Interior heating pyrolysis reactors**

unit, and a static bed (reaction bed), and a product exit was utilized in reactions that took place between gas phase (gaseous reactants) and solid phase (catalyst bed). Recently, Fixed-bed reactor has been widely used in the pyrolysis process of lignin or biomass. Generally, the heater that supplies the energy for pyrolysis of lignin is the electric furnace [20, 29]. The rate of heating is uneven and the efficiency of heating is low; this is because the furnace is usually attached on the periphery of the fixed bed. So, the yield of bio-oil is low and the end products are

However, fixed bed is appropriate for the catalytic pyrolysis process. Catalytic

The pyrolysis process of lignin in fluidized-bed reactor produced higher yield of bio-oil. In addition, the pyrolysis process of lignin in fluidized bed reactor produces lower guaiacols compared to the pyrolysis process in fixed-bed reactor. Even though the selectivity relies on diverse factors such as reaction conditions and the source of lignin, the high heat transfer effectiveness of fluidized-bed also secures equal high temperature during the pyrolysis process, which is contributory to demethoxylation reaction of lignin [31]. Anyhow, fluidized-bed reactor has some flaws for the pyrolysis process of lignin. The highest temperature was noticed nearly in the upper border of the bed [32] because of the continuous reaction of pyrolysis vapors in the part, indicating that undesirable side reaction happens out of the fluidized bed and in completed pyrolysis reaction in the cell of the fluidized bed, which could produce more of undesirable by-products. So, it was noticed that the most desired products

In fluidized bed and fixed reactors, furnace, catalyst, and hot gases are utilized

as heating media, which provide the energy to the substance from the exterior surface to the interior center. These ineffectual traditional pyrolysis processes are usually producing low yield of bio-oil with low quality. Nowadays, microwave technology introduces unprecedented techniques for pyrolysis. Microwave radiation produces energy as a result of the interaction among polar molecules present in the material and electromagnetic field; the heat transmits from the interior to the exterior surface of the substance [34]. Microwave-assisted pyrolysis indicates high energy effectiveness and supplies identical interior heating. Pyrolysis process by microwave produces uniform products due to the distinctive thermal

Unlike traditional heating, microwave heating provides quick quenching of pyrolysis vapors, which avoid the second decomposition reactions of the primary products. Compared to pyrolysis by electric heating, the pyrolysis process by microwave assists the production of phenolic compounds from lignin [36]. In addition, esters and hydrocarbons in bio-oil steeply rose compared to that gained from electric-heating pyrolysis due to the formation of hot points formed by microwave heating, which facilitates the conversion of guaiacols to gases such CO and H2 [37].

pyrolysis of lignin can produce High yield of aromatic compounds [30]. This is because the primary products from catalytic pyrolysis of lignin necessarily pass through the long catalytic bed (static bed), introducing more contacting opportunity for pyrolysis vapors and catalyst. Fluidized-bed reactor supplies more enormous heating for the pyrolysis process compared to fixed-bed reactor. Fluidized-bed reactor is a chamber that facilitates the mixing of gas substrates or liquid with solid particles acting as a fluid. The fluidization increases the mixing and interaction among gas and particles, resulting in efficient heat transfer sym-

**16**

gradients [35].

Temperature has a crucial effect in the catalytic fast pyrolysis of lignin. To decease the secondary reactions of primary vapors which decline the yield and quality of liquid products, a quick heating and cooling of primary vapors should be used [38]. As well as, the slow heating rate produces high yield of char [39]. Temperature has a vital influence on the yield of char and its properties. High temperatures lead to lower yield of char in all of pyrolysis reactions. The first cause for this is the removing of many volatile substances from the char at high temperatures, resulting in a decline in the char yield. For instance, the char yield declines from 31 to 17% with a rise in the temperature from 638K to 879K [40]. Low temperatures lead to imperfect decomposition of biomass resulting in a high quantity of unpyrolyzed solid materials in char content. Also, temperature has an influence on the composition of the char, chars obtained at high temperatures having high carbon content [41, 42]. At the temperatures higher than 773K,The char contains more than 85wt% carbon [43]. The yield of Liquid products increases by raising the pyrolysis temperatures up to an extreme value, at 673– 823 K, but it greatly relies on other operating factors. For a diverse of feedstock sorts, it has been studied that the extreme yield of pyrolysis oil is produced at temperatures of about 673–823 K with a constant decline in char yield and rise in gas yield.

## **2.6 Effect of the reaction time**

The time when the biomass was sustained at a specific pyrolysis temperature is the reaction time. In batch systems, the reaction time must be adequate to achieve the required result in the process. Secondary reactions of primary vapors can occur under long reaction time such as carbonization, thermal cracking, and gasification that lead low bio-oil yield [44, 45]. As well as, the reaction time is essential for the reactor configuration step. Tsai et al. [45] studied the pyrolysis process of rice husk in fixed bed reactor, they observed That, the bio-oil yield rose by rising the reaction time from 1 min to 2 min. However, the yields after that were noticed to decline slightly at long holding time.

### **2.7 Effect of lignin source**

The source of lignin and method of isolation have a great impact on the pyrolysis process and the distribution of pyrolysis products. Wang et al. [46] studied the pyrolysis process of various four sorts of lignin, Klason lignin (KL), alkali lignin (AL), milled wood lignin (MWL), and organosolv lignin (OL), separated from the same pine wood, by TG-FTIR and Py-GC/MS as well as 13C NMR spectroscopy. The 13C NMR indicated chemical structure of these separated lignin's is diverse. Ether bonds such as ß-O-4 have lower thermal stability and can decompose readily at low temperatures. So, lignin's containing more ether bonds could show weaker thermal stability. Alkali lignin and milled wood lignin, because they contain more ß-O-4 bonds in their structures, have a lower temperature at maximum weight loss rate (346 and 359°C, respectively) than OL (396°C) or KL (405°C). So, the pyrolysis process of AL and MWL produced more phenolic compounds at lower temperatures. The predominate products in pyrolysis of these softwood lignin's are guaiacyl-type compounds due to shortage of syringyl-type unit in the structure of softwood and the highest yield of phenol was achieved at 600°C.

Mullen and Boateng [25] studied the pyrolysis of lignin from four various sources over an acidic zeolite (HZSM-5) and a mixed metal oxide catalyst (CoO/ MoO3). Even though two catalysts formed to be efficient catalysts for deoxygenation reaction, enhancing the formation of aromatic hydrocarbons from lignin, the acidic HZSM-5 was observed to be more active than CoO/MoO3.

## **3. Deactivation of the catalysts**

Phenolic compounds produced from Lignin pyrolysis are substantially adsorbed on acidic sites of zeolite catalyst, and could behave as a coke precursor and produce a great amount of coke [47]. A great amount of coke produced from catalytic fast pyrolysis of lignin commonly leads to quick deactivation of zeolite catalysts, which declines the carbon conversion effectiveness [48]. Ivanov et al. studied the deactivation of H-ZSM5 zeolite by the formation of coke and the regeneration in the production of phenol from nitrous oxide oxidation of the benzene [49]. They observed that the main reason for the deactivating effect of coke is the poisoning of active sites. A large content of coke requires to be removed for the regeneration of the catalytic activity of the catalyst.

## **4. The role of mesoporous catalyst acidity and textural topology**

There have been many recent studies on the role of mesoporous catalysts in fast pyrolysis of lignin to aromatic compounds [20, 50–56].

In our previous publication [36] we studied the production of highly selective BTX from catalytic fast pyrolysis of lignin over supported mesoporous silica. We found that the yield of BTX rose from 17.0% in the case of MCM-48 to 32.5% in the case of Al/MCM-48 (8.4%) and 49.4% in the case of Zr/MCM-48 (2.9%) due to enhancing the acidity of the catalysts. Between the studied catalysts, Zr4+ loaded onto MCM-48 was considered a favorable catalyst for lignin pyrolysis with high activity and selectivity to BTX yield.

A.M. Elfadly et al [57] studied the Production of aromatic hydrocarbons from catalytic pyrolysis of lignin over acid-activated bentonite clay. They found that the catalytic fast pyrolysis of lignin over HCl-activated bentonite (mainly montmorillonite) produced a diverse of aromatics such BTX, naphthalene, indenes, and alkyl benzene, with extraordinary selectivity toward O&P-xylenes. The production of o&p-xylenes was remarkably improved at a temperature of about 550–650°C. Thus, it would be favorable to carry out the catalytic pyrolysis over HCl-activated bentonite if O&P-xylenes are the required products. They concluded that the enhanced activity of HCl-activated bentonite is due to the improvement in the textural characteristics and strong Bronsted acid sites resulted from acid treatment. H2SO4 and H3PO4 treatments formed an amorphous material and caused the destruction of the bentonite crystalline structure. Thus, these substances showed inactivity in catalytic fast pyrolysis of lignin.

Victoria B. F. Custodis et al [58] studied the Catalytic Fast Pyrolysis of Lignin over High Surface Area Mesoporous Aluminosilicates, and they focused on the influence of Acidity and Porosity. The results revealed that the acid sites (mild Bronsted and stronger Lewis) are responsible for catalyzing the pyrolysis intermediates to produce lower oxygenated phenolic compounds and aromatic

**19**

*A Study on Pyrolysis of Lignin over Mesoporous Materials*

hydrocarbons. MCM-41 in nano size produced a high yield and selectivity of aromatic hydrocarbons. The two most important factors are diffusion, which is affected by the pore and grain size, and the active site, which may be moderately acidic by Lewis acid sites. Nanosized grains and moderate acidity are important ingredients for a perfect catalyst for catalytic fast pyrolysis of lignin. Nanosized Al- MCM-41(50) formed the highest quantity of aromatic hydrocarbons (containing naphthalenes) (peak area 80%) compared to all mesoporous

Lee et al. [59] studied the conversion of lignin over Al-MCM-48. Al-MCM-48

Yi-Xin Chen et al [60] studied the arene production by W2C/MCM-41-catalyzed upgrading of vapors from fast pyrolysis of lignin. The experiments were carried out in a micro pyrolyzer-gas chromatography/mass spectrometer (P-GC/MS). A range of W2C/MCM-41 catalysts with various catalyst loading quantities (Si/W) was prepared, and the activity, selectivity, and the stability degree of the catalysts were studied. They found that the catalyst with Si/W = 50:1 showed the best activity and the highest arene yield. Also, the increase in the loading percent of catalyst can enhance the cracking reaction of pyrolysis vapors. The mechanism of lignin fast pyrolysis included dehydration, demethylation, and rearrangement reactions. They concluded that MCM-41 catalysts have the best activity to catalyze the production of monocyclic arenes from primary pyrolysis vapors. In addition, they showed a high stability in catalytic fast pyrolysis of lignin. So, the modified mesoporous MCM-41 catalysts with tungsten carbide are favorable catalysts in catalytic fast

Lee et al. [61] studied the catalytic fast pyrolysis of lignin over mesoporous Y zeolite using Py-GC/MS. The catalytic fast pyrolysis of lignin was taking place at 500°C using pyrolysis gas chromatography/mass spectrometry. Mesoporous Y zeolite and mesoporous material, Al-MCM-41, were tested for the catalytic fast pyrolysis of lignin. The noncatalytic pyrolysis of lignin produced phenolic compounds as a main product; this is because lignin composition mainly includes phenyl propane units. Catalytic upgrading of primary pyrolysis vapors increased the yields of low-molecular-mass phenolic compounds, monocyclic aromatics, and poly aromatic hydrocarbons (PAHs). The production of monocyclic aromatics and PAHs was increased significantly when the more acidic mesoporous Y zeolite was utilized. In contrast, the yield of alkoxy phenolic compounds was greater when the low acidic Al-MCM-41 was tested. Increasing mesoporous Y/lignin ratio showed

enhanced the production of light phenolic compounds extremely. The yields of aromatics and hydrocarbons were also improved by catalytic upgrading. Al-MCM-48 promoted the cracking, aromatization, and deoxygenation reactions, like decarbonylation. The hydrocarbons yield increased with increasing catalyst quantity to reach C/L = 1:5. This was due to the increased opportunity of catalytic reactions to occur on the acidic sites of the catalyst, such as cracking, decarboxylation, decarbonylation, and aromatization. Most produced hydrocarbons were cyclic and aromatic compounds, such as BTX. This indicates that phenolic compounds were transformed to cyclic and aromatic hydrocarbons by catalytic deoxygenation and cracking over Al-MCM-48 catalyst. However, the total quantity of aromatics and hydrocarbons was low compared to that of phenolic compounds. This is due to the weak acid sites of Al-MCM-48. The production of aromatics and hydrocarbons is enhanced over strong Bronsted acid sites, which are not present on Al-MCM-48. Furthermore, Si-MCM-48, which doesn't contain acid sites, exhibited lower deoxygenation effectiveness

*DOI: http://dx.doi.org/10.5772/intechopen.83785*

catalysts.

than Al-MCM-48.

pyrolysis of lignin.

*Recent Advances in Pyrolysis*

activity of the catalyst.

**3. Deactivation of the catalysts**

Mullen and Boateng [25] studied the pyrolysis of lignin from four various sources over an acidic zeolite (HZSM-5) and a mixed metal oxide catalyst (CoO/ MoO3). Even though two catalysts formed to be efficient catalysts for deoxygenation reaction, enhancing the formation of aromatic hydrocarbons from lignin, the acidic

Phenolic compounds produced from Lignin pyrolysis are substantially adsorbed on acidic sites of zeolite catalyst, and could behave as a coke precursor and produce a great amount of coke [47]. A great amount of coke produced from catalytic fast pyrolysis of lignin commonly leads to quick deactivation of zeolite catalysts, which declines the carbon conversion effectiveness [48]. Ivanov et al. studied the deactivation of H-ZSM5 zeolite by the formation of coke and the regeneration in the production of phenol from nitrous oxide oxidation of the benzene [49]. They observed that the main reason for the deactivating effect of coke is the poisoning of active sites. A large content of coke requires to be removed for the regeneration of the catalytic

**4. The role of mesoporous catalyst acidity and textural topology**

pyrolysis of lignin to aromatic compounds [20, 50–56].

activity and selectivity to BTX yield.

There have been many recent studies on the role of mesoporous catalysts in fast

In our previous publication [36] we studied the production of highly selective BTX from catalytic fast pyrolysis of lignin over supported mesoporous silica. We found that the yield of BTX rose from 17.0% in the case of MCM-48 to 32.5% in the case of Al/MCM-48 (8.4%) and 49.4% in the case of Zr/MCM-48 (2.9%) due to enhancing the acidity of the catalysts. Between the studied catalysts, Zr4+ loaded onto MCM-48 was considered a favorable catalyst for lignin pyrolysis with high

A.M. Elfadly et al [57] studied the Production of aromatic hydrocarbons from catalytic pyrolysis of lignin over acid-activated bentonite clay. They found that the catalytic fast pyrolysis of lignin over HCl-activated bentonite (mainly montmorillonite) produced a diverse of aromatics such BTX, naphthalene, indenes, and alkyl benzene, with extraordinary selectivity toward O&P-xylenes. The production of o&p-xylenes was remarkably improved at a temperature of about 550–650°C. Thus, it would be favorable to carry out the catalytic pyrolysis over HCl-activated bentonite if O&P-xylenes are the required products. They concluded that the enhanced activity of HCl-activated bentonite is due to the improvement in the textural characteristics and strong Bronsted acid sites resulted from acid treatment. H2SO4 and H3PO4 treatments formed an amorphous material and caused the destruction of the bentonite crystalline structure. Thus, these substances showed inactivity in catalytic fast pyrolysis of

Victoria B. F. Custodis et al [58] studied the Catalytic Fast Pyrolysis of Lignin over High Surface Area Mesoporous Aluminosilicates, and they focused on the influence of Acidity and Porosity. The results revealed that the acid sites (mild Bronsted and stronger Lewis) are responsible for catalyzing the pyrolysis intermediates to produce lower oxygenated phenolic compounds and aromatic

HZSM-5 was observed to be more active than CoO/MoO3.

**18**

lignin.

hydrocarbons. MCM-41 in nano size produced a high yield and selectivity of aromatic hydrocarbons. The two most important factors are diffusion, which is affected by the pore and grain size, and the active site, which may be moderately acidic by Lewis acid sites. Nanosized grains and moderate acidity are important ingredients for a perfect catalyst for catalytic fast pyrolysis of lignin. Nanosized Al- MCM-41(50) formed the highest quantity of aromatic hydrocarbons (containing naphthalenes) (peak area 80%) compared to all mesoporous catalysts.

Lee et al. [59] studied the conversion of lignin over Al-MCM-48. Al-MCM-48 enhanced the production of light phenolic compounds extremely. The yields of aromatics and hydrocarbons were also improved by catalytic upgrading. Al-MCM-48 promoted the cracking, aromatization, and deoxygenation reactions, like decarbonylation. The hydrocarbons yield increased with increasing catalyst quantity to reach C/L = 1:5. This was due to the increased opportunity of catalytic reactions to occur on the acidic sites of the catalyst, such as cracking, decarboxylation, decarbonylation, and aromatization. Most produced hydrocarbons were cyclic and aromatic compounds, such as BTX. This indicates that phenolic compounds were transformed to cyclic and aromatic hydrocarbons by catalytic deoxygenation and cracking over Al-MCM-48 catalyst. However, the total quantity of aromatics and hydrocarbons was low compared to that of phenolic compounds. This is due to the weak acid sites of Al-MCM-48. The production of aromatics and hydrocarbons is enhanced over strong Bronsted acid sites, which are not present on Al-MCM-48. Furthermore, Si-MCM-48, which doesn't contain acid sites, exhibited lower deoxygenation effectiveness than Al-MCM-48.

Yi-Xin Chen et al [60] studied the arene production by W2C/MCM-41-catalyzed upgrading of vapors from fast pyrolysis of lignin. The experiments were carried out in a micro pyrolyzer-gas chromatography/mass spectrometer (P-GC/MS). A range of W2C/MCM-41 catalysts with various catalyst loading quantities (Si/W) was prepared, and the activity, selectivity, and the stability degree of the catalysts were studied. They found that the catalyst with Si/W = 50:1 showed the best activity and the highest arene yield. Also, the increase in the loading percent of catalyst can enhance the cracking reaction of pyrolysis vapors. The mechanism of lignin fast pyrolysis included dehydration, demethylation, and rearrangement reactions. They concluded that MCM-41 catalysts have the best activity to catalyze the production of monocyclic arenes from primary pyrolysis vapors. In addition, they showed a high stability in catalytic fast pyrolysis of lignin. So, the modified mesoporous MCM-41 catalysts with tungsten carbide are favorable catalysts in catalytic fast pyrolysis of lignin.

Lee et al. [61] studied the catalytic fast pyrolysis of lignin over mesoporous Y zeolite using Py-GC/MS. The catalytic fast pyrolysis of lignin was taking place at 500°C using pyrolysis gas chromatography/mass spectrometry. Mesoporous Y zeolite and mesoporous material, Al-MCM-41, were tested for the catalytic fast pyrolysis of lignin. The noncatalytic pyrolysis of lignin produced phenolic compounds as a main product; this is because lignin composition mainly includes phenyl propane units. Catalytic upgrading of primary pyrolysis vapors increased the yields of low-molecular-mass phenolic compounds, monocyclic aromatics, and poly aromatic hydrocarbons (PAHs). The production of monocyclic aromatics and PAHs was increased significantly when the more acidic mesoporous Y zeolite was utilized. In contrast, the yield of alkoxy phenolic compounds was greater when the low acidic Al-MCM-41 was tested. Increasing mesoporous Y/lignin ratio showed

a sharp increase in the yield of monocyclic aromatic compounds and PAHs; also, the yield of light phenolics increased, but the yield of total phenolic compounds declined.

Ming-hui Fan et al [62] studied the Catalytic Depolymerization of lignin for the production of BTX. The conversion of lignin to benzene, toluene, and xylenes (BTX) was tested over the HZSM-5 and MCM-22 catalysts; the HZSM-5 catalyst indicated the largest yield of BTX. They studied various reaction conditions, involving temperature, the catalyst/lignin ratio, and the gas flow rate. The carbon yield of BTX was nearly 25.3 C-mol% in the presence of HZSM-5 catalyst at a temperature of 550°C, a flow of N2 300 cm3 /min, and a catalyst/lignin ratio of 2:1. HZSM-5 showed the best activity due to the mild acidity; in addition, the small pore size are useful for cracking and the deoxygenation reactions of lignin. Temperature has a high impact on the product distribution. The BTX selectivity increased by raising the temperature, but high temperature may lead to the production of olefins and alkanes due to a second cracking reaction. The BTX selectivity is strongly associated with the catalyst/lignin ratio, and the optimum ratio of catalyst to lignin was nearly 2:1. More increase of the catalyst/lignin ratio will decline the BTX yield, which leads to an increase in the yield of gas products. They observed that the reaction time should be carefully controlled to obtain high-yield BTX. The production of BTX was performed through depolymerization of lignin followed by the deoxygenation reaction.

The influence of various catalysts on the yield of aromatics during the fast pyrolysis process of biomass is summarized in **Table 1**.

Based on these studies, high quality aromatic compounds will be produced by a suitable choice of catalyst and reaction conditions.

Tang S et al. [64] studied the catalytic pyrolysis of lignin over hierarchical HZSM-5 zeolites prepared by posttreatment with alkaline solutions. They observed that the alkali treatment of HZSM-5 enhanced the catalytic activity of HZSM-5 zeolite for cracking of bulky oxygenates produced from lignin pyrolysis to form aromatic hydrocarbons. The HZSM-5 zeolite treated with 0.3 mol/L NaOH was the best choice for the catalytic fast pyrolysis of lignin for the production of aromatic hydrocarbons.

Compared to the parent HZSM-5, alkali-treated HZSM-5 zeolite showed greater selectivity to aromatic hydrocarbons by the catalytic fast pyrolysis of lignin. Some of the silicon species from the zeolite structures are removed during alkali treatment, forming new intracrystalline mesopores in the HZSM-5 grains, destroying a portion of the crystalline structure, and reducing the density of strong acid sites, which are the catalytic sites responsible for the conversion of oxygenated compounds to aromatic hydrocarbons. Even though the density of strong acid sites in zeolites is declined by alkali treatment, the effectiveness of transforming of bulky oxygenates to aromatic hydrocarbons is improved.

Catalytic pyrolysis of lignin with red mud derived hierarchical porous catalyst for the production of alkyl-phenols and hydrocarbons was studied by Wang et al. [65]. They investigated the catalytic behavior of the synthetic ACRM catalyst in the thermal decomposition of lignin. The prepared ACRM catalyst had a wellstructured hierarchical porosity, which could enhance the specific surface area and the dispersion of acidic sites and active metal oxides. These enhanced properties of the ACRM showed high catalytic activity during the catalytic pyrolysis of lignin vapors. The catalyst increased the production of alkyl phenols and aromatic hydrocarbons in bio-oil by about 74% at 550°C, due to promoting the dehydroxylation, demethoxylation, demethylation, and alkylation reactions [66].

**21**

**Table 1.**

*A Study on Pyrolysis of Lignin over Mesoporous Materials*

Quartz reactor with G'C/MS

Quartz reactor with GC/MS

Quartz reactor with GC/MS

In a down-flow fixedbed quartz reactor

Micro pyrolyzer-gas chromatography/ mass spectrometer (P-GC/MS)

Fixed-bed quartz reactor system

Fixed-bed quartz reactor system

Fixed-bed quartz reactor system

*Influence of various catalysts on the yield of aromatics during the fast pyrolysis process of biomass.*

**Used reactor Pyrolysis condition Yield of** 

of 20 cm s<sup>−</sup><sup>1</sup>

of 20 cm s<sup>−</sup><sup>1</sup>

of 20 cm s<sup>−</sup><sup>1</sup>

Py-GC/MS Pyrolysis performed

Flow system Pyrolysis performed at

Flow system Pyrolysis performed at

C/L ratio = 4:1, temperature at 650°C in a helium atmosphere at a heating rate

time = 20 1.

C/L ratio = 4:1, temperature at 650°C in a helium atmosphere at a heating rate

time = 20 s.

C/L ratio = 4:1, temperature at 650°C in a helium atmosphere at a heating rate

time = 20 s.

At temperature 650°C, flow of N2 = 75 ml/min and C/L ratio 3:1.

> at 500°C, lignin/ Al-MCM-48 = 1/5.

Reaction conditions: 750°C, 20 s, C/L = 10:1.

T = 550°C, f(N2) = 300 cm3

min, and a catalyst/lignin ratio of 2.

T = 550°C, f(N2) = 300 cm3

min, and a catalyst/lignin ratio of 2:1.

Pyrolysis performed at T = 600°C, f (N2) = 25 ml/ min, and a catalyst/lignin ratio of 3:1.

Pyrolysis performed at T = 550°C, f (N2) = 25 ml/ min, and a catalyst/lignin ratio of 3:1.

Pyrolysis performed at T = 550°C, f (N2) = 25 ml/ min, and a catalyst/lignin ratio of 2:1.

/

/

, and reaction

, and reaction

, and reaction

**aromatics (BTX) (%)**

**Yield of phenols (%)**

80 15 [58]

53 25 [58]

57 22 [58]

18 2 [57]

3.82 11.17 [59]

14.22 0.67 [60]

25.3 3 [62]

19 3.5 [63]

17 1.12 [21]

32.5 5.6 [21]

49.4 1.09 [21]

**Ref**

*DOI: http://dx.doi.org/10.5772/intechopen.83785*

**feed**

lignin

lignin

lignin

lignin

powder (kraft, alkali)

lignin

Sulfurfree lignin from wheat straw

free lignin from wheat straw

lignin

lignin

lignin

**Catalyst Type of** 

Al-MCM-41(50) Alkaline

Al-MSU-J (50)2 Alkaline

Al-SBA-15(50)-2 Alkaline

AB(HCl) Alkaline

Al-MCM-48 Lignin

W2C/ MCM-41 Alkaline

MCM-22 Sulfur-

MCM-48 Alkaline

Al/MCM-48 Alkaline

Zr/MCM-48 Alkaline


*Recent Advances in Pyrolysis*

at a temperature of 550°C, a flow of N2 300 cm3

followed by the deoxygenation reaction.

pyrolysis process of biomass is summarized in **Table 1**.

suitable choice of catalyst and reaction conditions.

oxygenates to aromatic hydrocarbons is improved.

declined.

hydrocarbons.

a sharp increase in the yield of monocyclic aromatic compounds and PAHs; also, the yield of light phenolics increased, but the yield of total phenolic compounds

Ming-hui Fan et al [62] studied the Catalytic Depolymerization of lignin for the production of BTX. The conversion of lignin to benzene, toluene, and xylenes (BTX) was tested over the HZSM-5 and MCM-22 catalysts; the HZSM-5 catalyst indicated the largest yield of BTX. They studied various reaction conditions, involving temperature, the catalyst/lignin ratio, and the gas flow rate. The carbon yield of BTX was nearly 25.3 C-mol% in the presence of HZSM-5 catalyst

of 2:1. HZSM-5 showed the best activity due to the mild acidity; in addition, the small pore size are useful for cracking and the deoxygenation reactions of lignin. Temperature has a high impact on the product distribution. The BTX selectivity increased by raising the temperature, but high temperature may lead to the production of olefins and alkanes due to a second cracking reaction. The BTX selectivity is strongly associated with the catalyst/lignin ratio, and the optimum ratio of catalyst to lignin was nearly 2:1. More increase of the catalyst/lignin ratio will decline the BTX yield, which leads to an increase in the yield of gas products. They observed that the reaction time should be carefully controlled to obtain high-yield BTX. The production of BTX was performed through depolymerization of lignin

The influence of various catalysts on the yield of aromatics during the fast

Tang S et al. [64] studied the catalytic pyrolysis of lignin over hierarchical HZSM-5 zeolites prepared by posttreatment with alkaline solutions. They observed that the alkali treatment of HZSM-5 enhanced the catalytic activity of HZSM-5 zeolite for cracking of bulky oxygenates produced from lignin pyrolysis to form aromatic hydrocarbons. The HZSM-5 zeolite treated with 0.3 mol/L NaOH was the best choice for the catalytic fast pyrolysis of lignin for the production of aromatic

Based on these studies, high quality aromatic compounds will be produced by a

Compared to the parent HZSM-5, alkali-treated HZSM-5 zeolite showed greater selectivity to aromatic hydrocarbons by the catalytic fast pyrolysis of lignin. Some of the silicon species from the zeolite structures are removed during alkali treatment, forming new intracrystalline mesopores in the HZSM-5 grains, destroying a portion of the crystalline structure, and reducing the density of strong acid sites, which are the catalytic sites responsible for the conversion of oxygenated compounds to aromatic hydrocarbons. Even though the density of strong acid sites in zeolites is declined by alkali treatment, the effectiveness of transforming of bulky

Catalytic pyrolysis of lignin with red mud derived hierarchical porous catalyst for the production of alkyl-phenols and hydrocarbons was studied by Wang et al. [65]. They investigated the catalytic behavior of the synthetic ACRM catalyst in the thermal decomposition of lignin. The prepared ACRM catalyst had a wellstructured hierarchical porosity, which could enhance the specific surface area and the dispersion of acidic sites and active metal oxides. These enhanced properties of the ACRM showed high catalytic activity during the catalytic pyrolysis of lignin vapors. The catalyst increased the production of alkyl phenols and aromatic hydrocarbons in bio-oil by about 74% at 550°C, due to promoting the dehydroxylation, demethoxylation, demethylation, and alkylation

/min, and a catalyst/lignin ratio

**20**

reactions [66].

#### **Table 1.**

*Influence of various catalysts on the yield of aromatics during the fast pyrolysis process of biomass.*

*Recent Advances in Pyrolysis*

## **Author details**

Abdelrahman Mohamed Rabie\* and Marwa Mohamed Abouelela Petrochemical Department, Egyptian Petroleum Research Institute, Cairo, Egypt

\*Address all correspondence to: abdo3040@yahoo.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**23**

2019;**180**:36-43

2019;**239**:1015-1027

*A Study on Pyrolysis of Lignin over Mesoporous Materials*

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[12] Carlson TR, Jae J, Lin YC, Tompsett GA, Huber GW. Catalytic fast pyrolysis of glucose with HZSM-5: The combined homogeneous and heterogeneous reactions. Journal of Catalysis.

[13] Carlson TR, Vispute TP, Huber GW. Green gasoline by catalytic fast pyrolysis of solid biomass derived compounds. Chemistry and Sustainability Energy and Materials.

[14] Cheng YT, Huber GW. Chemistry of furan conversion into aromatics and olefins over HZSM-5: A model biomass conversion reaction. ACS Catalysis.

[15] Jae J, Tompsett GA, Foster AJ, Hammond KD, Auerbach SM, Lobo RF, et al. Investigation into the shape selectivity of zeolite catalysts for biomass conversion. Journal of Catalysis. 2011;**279**:257-268

[16] Jae J, Tompsett GA, Lin YC, Carlson TR, Shen J, Zhang T, et al. Depolymerization of lignocellulosic biomass to fuel precursors: Maximizing

carbon efficiency by combining

Chemistry. 2016;**40**:1-15

*DOI: http://dx.doi.org/10.5772/intechopen.83785*

[1] Carlson TR, Tompsett GA, Conner WC, Huber GW. Aromatic production from catalytic fast pyrolysis of biomassderived feedstocks. Topics in Catalysis.

[2] Rezaei PS, Shafaghat H, Daud WMAW. Production of green aromatics and olefins by catalytic cracking of oxygenate compounds derived from biomass pyrolysis: A review. Applied Catalysis A: General. 2014;**469**:490-511

[3] Carlson TR, Cheng YT, Jae J, Huber GW. Production of green aromatics and olefins by catalytic fast pyrolysis of wood sawdust. Energy and

Environmental Science. 2011;**4**:145-161

comprehensive review on the pyrolysis of lignocellulosic biomass. Renewable

[5] Wang B, Xu F, Zong P, Zhang J, Tian Y, Qiao Y. Effects of heating rate on fast pyrolysis behavior and product distribution of Jerusalem artichoke stalk by using TG-FTIR and Py-GC/ MS. Renewable Energy. 2019;**132**:486-496

[6] Han X, Guo Y, Liu X, Xia Q , Wang Y. Catalytic conversion of lignocellulosic biomass into hydrocarbons: A mini review. Catalysis Today. 2019;**319**:2-13

[7] Dai L, Wang Y, Liu Y, Ruan R, He C, Duan D, et al. Bridging the relationship between hydrothermal pretreatment and co-pyrolysis: Effect of hydrothermal pretreatment on aromatic production. Energy Conversion and Management.

[8] He Y, Bie Y, Lehtonen J, Liu R, Cai J. Hydrodeoxygenation of guaiacol as a model compound of lignin-derived pyrolysis bio-oil over zirconia-supported Rh catalyst: Process optimization and reaction kinetics. Fuel.

[4] Dhyani V, Bhaskar T. A

Energy. 2018;**129**:695-716

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*A Study on Pyrolysis of Lignin over Mesoporous Materials DOI: http://dx.doi.org/10.5772/intechopen.83785*

## **References**

*Recent Advances in Pyrolysis*

**22**

**Author details**

provided the original work is properly cited.

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Petrochemical Department, Egyptian Petroleum Research Institute, Cairo, Egypt

Abdelrahman Mohamed Rabie\* and Marwa Mohamed Abouelela

\*Address all correspondence to: abdo3040@yahoo.com

[1] Carlson TR, Tompsett GA, Conner WC, Huber GW. Aromatic production from catalytic fast pyrolysis of biomassderived feedstocks. Topics in Catalysis. 2009;**52**:241

[2] Rezaei PS, Shafaghat H, Daud WMAW. Production of green aromatics and olefins by catalytic cracking of oxygenate compounds derived from biomass pyrolysis: A review. Applied Catalysis A: General. 2014;**469**:490-511

[3] Carlson TR, Cheng YT, Jae J, Huber GW. Production of green aromatics and olefins by catalytic fast pyrolysis of wood sawdust. Energy and Environmental Science. 2011;**4**:145-161

[4] Dhyani V, Bhaskar T. A comprehensive review on the pyrolysis of lignocellulosic biomass. Renewable Energy. 2018;**129**:695-716

[5] Wang B, Xu F, Zong P, Zhang J, Tian Y, Qiao Y. Effects of heating rate on fast pyrolysis behavior and product distribution of Jerusalem artichoke stalk by using TG-FTIR and Py-GC/ MS. Renewable Energy. 2019;**132**:486-496

[6] Han X, Guo Y, Liu X, Xia Q , Wang Y. Catalytic conversion of lignocellulosic biomass into hydrocarbons: A mini review. Catalysis Today. 2019;**319**:2-13

[7] Dai L, Wang Y, Liu Y, Ruan R, He C, Duan D, et al. Bridging the relationship between hydrothermal pretreatment and co-pyrolysis: Effect of hydrothermal pretreatment on aromatic production. Energy Conversion and Management. 2019;**180**:36-43

[8] He Y, Bie Y, Lehtonen J, Liu R, Cai J. Hydrodeoxygenation of guaiacol as a model compound of lignin-derived pyrolysis bio-oil over zirconia-supported Rh catalyst: Process optimization and reaction kinetics. Fuel. 2019;**239**:1015-1027

[9] Cha JS, Park SH, Jung SC, Ryu C, Jeon JK, Shin MC, et al. Production and utilization of biochar: A review. Journal of Industrial and Engineering Chemistry. 2016;**40**:1-15

[10] Chi Y, Xue J, Zhuo J, Zhang D, Liu M, Yao Q. Catalytic co-pyrolysis of cellulose and polypropylene over all-silica mesoporous catalyst MCM-41 and Al-MCM-41. Science of the Total Environment. 2018;**633**:1105-1113

[11] Carlson TR, Jae J, Huber GW. Mechanistic insights from isotopic studies of glucose conversion to aromatics over ZSM-5. ChemCatChem. 2009;**1**:107-110

[12] Carlson TR, Jae J, Lin YC, Tompsett GA, Huber GW. Catalytic fast pyrolysis of glucose with HZSM-5: The combined homogeneous and heterogeneous reactions. Journal of Catalysis. 2010;**270**:110-124

[13] Carlson TR, Vispute TP, Huber GW. Green gasoline by catalytic fast pyrolysis of solid biomass derived compounds. Chemistry and Sustainability Energy and Materials. 2008;**1**:397-400

[14] Cheng YT, Huber GW. Chemistry of furan conversion into aromatics and olefins over HZSM-5: A model biomass conversion reaction. ACS Catalysis. 2011;**1**:611-628

[15] Jae J, Tompsett GA, Foster AJ, Hammond KD, Auerbach SM, Lobo RF, et al. Investigation into the shape selectivity of zeolite catalysts for biomass conversion. Journal of Catalysis. 2011;**279**:257-268

[16] Jae J, Tompsett GA, Lin YC, Carlson TR, Shen J, Zhang T, et al. Depolymerization of lignocellulosic biomass to fuel precursors: Maximizing carbon efficiency by combining

hydrolysis with pyrolysis. Energy and Environmental Science. 2010;**3**:358-365

[17] Foster AJ, Jae J, Cheng YT, Huber GW, Lobo RF. Optimizing the aromatic yield and distribution from catalytic fast pyrolysis of biomass over ZSM-5. Applied Catalysis A: General. 2012;**423**:154-161

[18] Duval A, Lawoko M. A review on lignin-based polymeric, micro-and nano-structured materials. Reactive and Functional Polymers. 2014;**85**:78-96

[19] Yaman S. Pyrolysis of biomass to produce fuels and chemical feedstocks. Energy Conversion and Management. 2004;**45**:651-671

[20] Jackson MA, Compton DL, Boateng AA. Screening heterogeneous catalysts for the pyrolysis of lignin. Journal of Analytical and Applied Pyrolysis. 2009;**85**:226-230

[21] Elfadly A, Zeid I, Yehia F, Rabie A, Park S-E. Highly selective BTX from catalytic fast pyrolysis of lignin over supported mesoporous silica. International Journal of Biological Macromolecules. 2016;**91**:278-293

[22] Zhu Y, Li H, Xu J, Yuan H, Wang J, Li X. Monodispersed mesoporous SBA-15 with novel morphologies: Controllable synthesis and morphology dependence of humidity sensing. CrystEngComm. 2011;**13**:402-405

[23] Zhu Y, Li H, Zheng Q , Xu J, Li X. Amine-functionalized SBA-15 with uniform morphology and well-defined mesostructure for highly sensitive chemosensors to detect formaldehyde vapor. Langmuir. 2012;**28**:7843-7850

[24] Gao D, Duan A, Zhang X, Zhao Z, E H, Li J, et al. Synthesis of NiMo catalysts supported on mesoporous Al-SBA-15 with different morphologies and their catalytic performance

of DBT HDS. Applied Catalysis B: Environmental. 2015;**165**:269-284

[25] Mullen CA, Boateng AA. Catalytic pyrolysis-GC/MS of lignin from several sources. Fuel Processing Technology. 2010;**91**:1446-1458

[26] Ma Z, Troussard E, van Bokhoven JA. Controlling the selectivity to chemicals from lignin via catalytic fast pyrolysis. Applied Catalysis A: General. 2012;**423**:130-136

[27] Klamrassamee T, Laosiripojana N, Cronin D, Moghaddam L, Zhang Z, Doherty WO. Effects of mesostructured silica catalysts on the depolymerization of organosolv lignin fractionated from woody eucalyptus. Bioresource Technology. 2015;**180**:222-229

[28] Fan L, Zhang Y, Liu S, Zhou N, Chen P, Cheng Y, et al. Bio-oil from fast pyrolysis of lignin: Effects of process and upgrading parameters. Bioresource Technology. 2017;**241**:1118-1126

[29] Ferdous D, Dalai A, Bej S, Thring R, Bakhshi N. Production of H2 and medium Btu gas via pyrolysis of lignins in a fixed-bed reactor. Fuel Processing Technology. 2001;**70**:9-26

[30] Thring RW, Katikaneni SP, Bakhshi NN. The production of gasoline range hydrocarbons from Alcell® lignin using HZSM-5 catalyst. Fuel Processing Technology. 2000;**62**:17-30

[31] Jiang G, Nowakowski DJ, Bridgwater AV. Effect of the temperature on the composition of lignin pyrolysis products. Energy & Fuels. 2010;**24**:4470-4475

[32] Kuznetsov B, Shchipko M. The conversion of wood lignin to char materials in a fluidized bed of Al• Cu• Cr oxide catalysts. Bioresource Technology. 1995;**52**:13-19

**25**

2010;**157**:481-494

1977

*A Study on Pyrolysis of Lignin over Mesoporous Materials*

[41] Thurner F, Mann U. Kinetic investigation of wood pyrolysis. Industrial and Engineering Chemistry Process Design and Development.

[42] Alves S, Figueiredo J. A model for pyrolysis of wet wood. Chemical Engineering Science.

[43] Wang X, Kersten SR, Prins W, van Swaaij WP. Biomass pyrolysis in a fluidized bed reactor. Part 2: Experimental validation of model results. Industrial and Engineering Chemistry Research.

[44] Bartoli M, Rosi L, Giovannelli A, Frediani P, Frediani M. Production of bio-oils and bio-char from Arundo donax through microwave assisted pyrolysis in a multimode batch reactor. Journal of Analytical and Applied Pyrolysis. 2016;**122**:479-489

[45] Tsai W, Lee M, Chang Y. Fast pyrolysis of rice husk: Product yields and compositions. Bioresource Technology. 2007;**98**:22-28

[46] Wang S, Ru B, Lin H, Sun W, Luo Z. Pyrolysis behaviors of four lignin polymers isolated from the same pine wood. Bioresource Technology.

[47] Rezaei PS, Shafaghat H, Daud WMAW. Aromatic hydrocarbon production by catalytic pyrolysis of palm kernel shell waste using a bifunctional Fe/HBeta catalyst: Effect of lignin-derived phenolics on zeolite deactivation. Green Chemistry.

[48] Bi Y, Lei X, Xu G, Chen H, Hu J. Catalytic fast pyrolysis of kraft lignin over hierarchical HZSM-5 and Hβ zeolites. Catalysts. 2018;**8**:82

1981;**20**:482-488

1989;**44**:2861-2869

2005;**44**:8786-8795

2015;**182**:120-127

2016;**18**:1684-1693

*DOI: http://dx.doi.org/10.5772/intechopen.83785*

[33] Sales FG, Maranhão LC, Lima Filho NM, Abreu CA. Experimental evaluation and continuous catalytic process for fine aldehyde production from lignin. Chemical Engineering

[34] Morgan HM Jr, Bu Q , Liang J, Liu Y, Mao H, Shi A, et al. A review of catalytic microwave pyrolysis of lignocellulosic biomass for valueadded fuel and chemicals. Bioresource

Technology. 2017;**230**:112-121

[36] Anca-Couce A. Reaction

[37] Bu Q , Lei H, Wang L, Wei Y, Zhu L, Zhang X, et al. Bio-based phenols and fuel production from catalytic microwave pyrolysis of lignin by activated carbons. Bioresource Technology. 2014;**162**:142-147

[38] Shafizadeh F, Chin PP. Thermal deterioration of wood. ACS Symposium Series American Chemical Society.

[39] Kersten SR, Wang X, Prins W, van Swaaij WP. Biomass pyrolysis in a fluidized bed reactor. Part 1: Literature

review and model simulations.

Research. 2005;**44**:8773-8785

[40] Park WC, Atreya A, Baum HR. Experimental and theoretical investigation of heat and mass transfer processes during wood pyrolysis. Combustion and Flame.

Industrial and Engineering Chemistry

Science. 2016;**53**:41-79

2013;**144**:240-246

[35] Beneroso D, Bermúdez J, Arenillas A, Menéndez J. Microwave pyrolysis of microalgae for high syngas

production. Bioresource Technology.

mechanisms and multi-scale modelling of lignocellulosic biomass pyrolysis. Progress in Energy and Combustion

Science. 2007;**62**:5386-5391

*A Study on Pyrolysis of Lignin over Mesoporous Materials DOI: http://dx.doi.org/10.5772/intechopen.83785*

[33] Sales FG, Maranhão LC, Lima Filho NM, Abreu CA. Experimental evaluation and continuous catalytic process for fine aldehyde production from lignin. Chemical Engineering Science. 2007;**62**:5386-5391

*Recent Advances in Pyrolysis*

2012;**423**:154-161

2004;**45**:651-671

2009;**85**:226-230

hydrolysis with pyrolysis. Energy and Environmental Science. 2010;**3**:358-365 of DBT HDS. Applied Catalysis B: Environmental. 2015;**165**:269-284

2010;**91**:1446-1458

2012;**423**:130-136

2015;**180**:222-229

[25] Mullen CA, Boateng AA. Catalytic pyrolysis-GC/MS of lignin from several sources. Fuel Processing Technology.

[26] Ma Z, Troussard E, van Bokhoven JA. Controlling the selectivity to chemicals from lignin via catalytic fast pyrolysis. Applied Catalysis A: General.

[27] Klamrassamee T, Laosiripojana N, Cronin D, Moghaddam L, Zhang Z, Doherty WO. Effects of mesostructured silica catalysts on the depolymerization of organosolv lignin fractionated from woody eucalyptus. Bioresource Technology.

[28] Fan L, Zhang Y, Liu S, Zhou N, Chen P, Cheng Y, et al. Bio-oil from fast pyrolysis of lignin: Effects of process and upgrading parameters. Bioresource

Technology. 2017;**241**:1118-1126

Technology. 2001;**70**:9-26

Technology. 2000;**62**:17-30

Fuels. 2010;**24**:4470-4475

Technology. 1995;**52**:13-19

[32] Kuznetsov B, Shchipko M. The conversion of wood lignin to char materials in a fluidized bed of

Al• Cu• Cr oxide catalysts. Bioresource

[31] Jiang G, Nowakowski DJ, Bridgwater AV. Effect of the temperature on the composition of lignin pyrolysis products. Energy &

[29] Ferdous D, Dalai A, Bej S, Thring R, Bakhshi N. Production of H2 and medium Btu gas via pyrolysis of lignins in a fixed-bed reactor. Fuel Processing

[30] Thring RW, Katikaneni SP, Bakhshi NN. The production of gasoline range hydrocarbons from Alcell® lignin using HZSM-5 catalyst. Fuel Processing

[17] Foster AJ, Jae J, Cheng YT, Huber GW, Lobo RF. Optimizing the aromatic yield and distribution from catalytic fast pyrolysis of biomass over ZSM-5. Applied Catalysis A: General.

[18] Duval A, Lawoko M. A review on lignin-based polymeric, micro-and nano-structured materials. Reactive and Functional Polymers. 2014;**85**:78-96

[19] Yaman S. Pyrolysis of biomass to produce fuels and chemical feedstocks. Energy Conversion and Management.

[20] Jackson MA, Compton DL, Boateng AA. Screening heterogeneous catalysts for the pyrolysis of lignin. Journal of Analytical and Applied Pyrolysis.

[21] Elfadly A, Zeid I, Yehia F, Rabie A, Park S-E. Highly selective BTX from catalytic fast pyrolysis of lignin over supported mesoporous silica. International Journal of Biological Macromolecules. 2016;**91**:278-293

[22] Zhu Y, Li H, Xu J, Yuan H, Wang J, Li X. Monodispersed mesoporous SBA-15 with novel morphologies: Controllable synthesis and morphology dependence of humidity sensing. CrystEngComm. 2011;**13**:402-405

[23] Zhu Y, Li H, Zheng Q , Xu J, Li X. Amine-functionalized SBA-15 with uniform morphology and well-defined mesostructure for highly sensitive chemosensors to detect formaldehyde vapor. Langmuir. 2012;**28**:7843-7850

[24] Gao D, Duan A, Zhang X, Zhao Z, E H, Li J, et al. Synthesis of NiMo catalysts supported on mesoporous Al-SBA-15 with different morphologies

and their catalytic performance

**24**

[34] Morgan HM Jr, Bu Q , Liang J, Liu Y, Mao H, Shi A, et al. A review of catalytic microwave pyrolysis of lignocellulosic biomass for valueadded fuel and chemicals. Bioresource Technology. 2017;**230**:112-121

[35] Beneroso D, Bermúdez J, Arenillas A, Menéndez J. Microwave pyrolysis of microalgae for high syngas production. Bioresource Technology. 2013;**144**:240-246

[36] Anca-Couce A. Reaction mechanisms and multi-scale modelling of lignocellulosic biomass pyrolysis. Progress in Energy and Combustion Science. 2016;**53**:41-79

[37] Bu Q , Lei H, Wang L, Wei Y, Zhu L, Zhang X, et al. Bio-based phenols and fuel production from catalytic microwave pyrolysis of lignin by activated carbons. Bioresource Technology. 2014;**162**:142-147

[38] Shafizadeh F, Chin PP. Thermal deterioration of wood. ACS Symposium Series American Chemical Society. 1977

[39] Kersten SR, Wang X, Prins W, van Swaaij WP. Biomass pyrolysis in a fluidized bed reactor. Part 1: Literature review and model simulations. Industrial and Engineering Chemistry Research. 2005;**44**:8773-8785

[40] Park WC, Atreya A, Baum HR. Experimental and theoretical investigation of heat and mass transfer processes during wood pyrolysis. Combustion and Flame. 2010;**157**:481-494

[41] Thurner F, Mann U. Kinetic investigation of wood pyrolysis. Industrial and Engineering Chemistry Process Design and Development. 1981;**20**:482-488

[42] Alves S, Figueiredo J. A model for pyrolysis of wet wood. Chemical Engineering Science. 1989;**44**:2861-2869

[43] Wang X, Kersten SR, Prins W, van Swaaij WP. Biomass pyrolysis in a fluidized bed reactor. Part 2: Experimental validation of model results. Industrial and Engineering Chemistry Research. 2005;**44**:8786-8795

[44] Bartoli M, Rosi L, Giovannelli A, Frediani P, Frediani M. Production of bio-oils and bio-char from Arundo donax through microwave assisted pyrolysis in a multimode batch reactor. Journal of Analytical and Applied Pyrolysis. 2016;**122**:479-489

[45] Tsai W, Lee M, Chang Y. Fast pyrolysis of rice husk: Product yields and compositions. Bioresource Technology. 2007;**98**:22-28

[46] Wang S, Ru B, Lin H, Sun W, Luo Z. Pyrolysis behaviors of four lignin polymers isolated from the same pine wood. Bioresource Technology. 2015;**182**:120-127

[47] Rezaei PS, Shafaghat H, Daud WMAW. Aromatic hydrocarbon production by catalytic pyrolysis of palm kernel shell waste using a bifunctional Fe/HBeta catalyst: Effect of lignin-derived phenolics on zeolite deactivation. Green Chemistry. 2016;**18**:1684-1693

[48] Bi Y, Lei X, Xu G, Chen H, Hu J. Catalytic fast pyrolysis of kraft lignin over hierarchical HZSM-5 and Hβ zeolites. Catalysts. 2018;**8**:82

[49] Ivanov D, Sobolev V, Panov G. Deactivation by coking and regeneration of zeolite catalysts for benzene-to-phenol oxidation. Applied Catalysis A: General. 2003;**241**:113-121

[50] Shen D, Zhao J, Xiao R, Gu S. Production of aromatic monomers from catalytic pyrolysis of black-liquor lignin. Journal of Analytical and Applied Pyrolysis. 2015;**111**:47-54

[51] Couhert C, Commandre JM, Salvador S. Is it possible to predict gas yields of any biomass after rapid pyrolysis at high temperature from its composition in cellulose, hemicellulose and lignin? Fuel. 2009;**88**:408-417

[52] Welker C, Balasubramanian V, Petti C, Rai K, DeBolt S, Mendu V. Engineering plant biomass lignin content and composition for biofuels and bioproducts. Energies. 2015;**8**:7654-7676

[53] Giudicianni P, Cardone G, Ragucci R. Cellulose, hemicellulose and lignin slow steam pyrolysis: Thermal decomposition of biomass components mixtures. Journal of Analytical and Applied Pyrolysis. 2013;**100**:213-222

[54] Iliopoulou E, Antonakou E, Karakoulia S, Vasalos I, Lappas A, Triantafyllidis K. Catalytic conversion of biomass pyrolysis products by mesoporous materials: Effect of steam stability and acidity of Al-MCM-41 catalysts. Chemical Engineering Journal. 2007;**134**:51-57

[55] Kelkar S, Saffron CM, Andreassi K, Li Z, Murkute A, Miller DJ, et al. A survey of catalysts for aromatics from fast pyrolysis of biomass. Applied Catalysis B: Environmental. 2015;**174**:85-95

[56] Stefanidis SD, Kalogiannis KG, Iliopoulou EF, Michailof CM, Pilavachi PA, Lappas AA. A study of lignocellulosic biomass pyrolysis via

the pyrolysis of cellulose, hemicellulose and lignin. Journal of Analytical and Applied Pyrolysis. 2014;**105**:143-150

[57] Elfadly A, Zeid I, Yehia F, Abouelela M, Rabie A. Production of aromatic hydrocarbons from catalytic pyrolysis of lignin over acid-activated bentonite clay. Fuel Processing Technology. 2017;**163**:1-7

[58] Custodis VB, Karakoulia SA, Triantafyllidis KS, van Bokhoven JA. Catalytic fast pyrolysis of lignin over high-surface-area mesoporous aluminosilicates: Effect of porosity and acidity. ChemSusChem. 2016;**9**:1134-1145

[59] Lee HW, Lee IG, Park SH, Jeon JK, Suh DJ, Jung J, et al. Application of mesoporous Al-MCM-48 material to the conversion of lignin. Journal of Nanoscience and Nanotechnology. 2014;**14**:2990-2995

[60] Chen YX, Zheng Y, Li M, Zhu XF. Arene production by W2C/MCM-41 catalyzed upgrading of vapors from fast pyrolysis of lignin. Fuel Processing Technology. 2015;**134**:46-51

[61] Lee HW, Kim TH, Park SH, Jeon JK, Suh DJ, Park YK. Catalytic fast pyrolysis of lignin over mesoporous Y zeolite using Py-GC/MS. Journal of Nanoscience and Nanotechnology. 2013;**13**:2640-2646

[62] Fan MH, Deng SM, Wang TJ, Li QX. Production of BTX through catalytic depolymerization of lignin. Chinese Journal of Chemical Physics. 2014;**27**:221-226

[63] Deng SM, Fan MH, Wang TJ, Li QX. Transformation of biomass into aromatics with zeolite catalysts. Chinese Journal of Chemical Physics. 2014;**27**:361

[64] Tang S, Zhang C, Xue X, Pan Z, Wang D, Zhang R. Catalytic pyrolysis of lignin over hierarchical HZSM-5 zeolites

**27**

*A Study on Pyrolysis of Lignin over Mesoporous Materials*

*DOI: http://dx.doi.org/10.5772/intechopen.83785*

prepared by post-treatment with alkaline solutions. Journal of Analytical and Applied Pyrolysis. 2019;**137**:86-95

[65] Tang S, Zhang C, Xue X, Pan Z, Wang D, Zhang R. Catalytic pyrolysis of lignin over hierarchical HZSM-5 zeolites

prepared by post-treatment with alkaline solutions. Journal of Analytical

and Applied Pyrolysis. 2018

2018;**136**:8-17

[66] Wang S, Li Z, Bai X, Yi W, Fu P. Catalytic pyrolysis of lignin with red mud derived hierarchical porous catalyst for alkyl-phenols and hydrocarbons production. Journal of Analytical and Applied Pyrolysis.

*A Study on Pyrolysis of Lignin over Mesoporous Materials DOI: http://dx.doi.org/10.5772/intechopen.83785*

prepared by post-treatment with alkaline solutions. Journal of Analytical and Applied Pyrolysis. 2019;**137**:86-95

*Recent Advances in Pyrolysis*

[49] Ivanov D, Sobolev V, Panov G. Deactivation by coking and

the pyrolysis of cellulose, hemicellulose and lignin. Journal of Analytical and Applied Pyrolysis. 2014;**105**:143-150

[57] Elfadly A, Zeid I, Yehia F, Abouelela M, Rabie A. Production of aromatic hydrocarbons from catalytic pyrolysis of lignin over acid-activated bentonite clay. Fuel Processing Technology.

[58] Custodis VB, Karakoulia SA, Triantafyllidis KS, van Bokhoven JA. Catalytic fast pyrolysis of lignin over high-surface-area mesoporous aluminosilicates: Effect of porosity and acidity. ChemSusChem.

[59] Lee HW, Lee IG, Park SH, Jeon JK, Suh DJ, Jung J, et al. Application of mesoporous Al-MCM-48 material to the conversion of lignin. Journal of Nanoscience and Nanotechnology.

[60] Chen YX, Zheng Y, Li M, Zhu XF. Arene production by W2C/MCM-41 catalyzed upgrading of vapors from fast pyrolysis of lignin. Fuel Processing

[61] Lee HW, Kim TH, Park SH, Jeon JK, Suh DJ, Park YK. Catalytic fast pyrolysis of lignin over mesoporous Y zeolite using Py-GC/MS. Journal of Nanoscience and Nanotechnology.

[62] Fan MH, Deng SM, Wang TJ, Li QX. Production of BTX through catalytic depolymerization of lignin. Chinese Journal of Chemical Physics.

[63] Deng SM, Fan MH, Wang TJ, Li QX. Transformation of biomass into aromatics with zeolite catalysts. Chinese Journal of Chemical Physics.

[64] Tang S, Zhang C, Xue X, Pan Z, Wang D, Zhang R. Catalytic pyrolysis of lignin over hierarchical HZSM-5 zeolites

Technology. 2015;**134**:46-51

2017;**163**:1-7

2016;**9**:1134-1145

2014;**14**:2990-2995

2013;**13**:2640-2646

2014;**27**:221-226

2014;**27**:361

regeneration of zeolite catalysts for benzene-to-phenol oxidation. Applied Catalysis A: General. 2003;**241**:113-121

[50] Shen D, Zhao J, Xiao R, Gu S. Production of aromatic monomers from catalytic pyrolysis of black-liquor lignin. Journal of Analytical and Applied

[51] Couhert C, Commandre JM, Salvador S. Is it possible to predict gas yields of any biomass after rapid pyrolysis at high temperature from its composition in cellulose, hemicellulose and lignin? Fuel. 2009;**88**:408-417

[52] Welker C, Balasubramanian V, Petti C, Rai K, DeBolt S, Mendu V. Engineering plant biomass lignin content and composition for biofuels and bioproducts. Energies.

[53] Giudicianni P, Cardone G, Ragucci R. Cellulose, hemicellulose and lignin slow steam pyrolysis: Thermal decomposition of biomass components mixtures. Journal of Analytical and Applied Pyrolysis. 2013;**100**:213-222

[54] Iliopoulou E, Antonakou E, Karakoulia S, Vasalos I, Lappas A, Triantafyllidis K. Catalytic conversion of biomass pyrolysis products by mesoporous materials: Effect of steam stability and acidity of Al-MCM-41 catalysts. Chemical Engineering Journal.

[55] Kelkar S, Saffron CM, Andreassi K, Li Z, Murkute A, Miller DJ, et al. A survey of catalysts for aromatics from fast pyrolysis of biomass. Applied Catalysis B: Environmental.

[56] Stefanidis SD, Kalogiannis KG, Iliopoulou EF, Michailof CM, Pilavachi PA, Lappas AA. A study of lignocellulosic biomass pyrolysis via

2015;**8**:7654-7676

2007;**134**:51-57

2015;**174**:85-95

Pyrolysis. 2015;**111**:47-54

**26**

[65] Tang S, Zhang C, Xue X, Pan Z, Wang D, Zhang R. Catalytic pyrolysis of lignin over hierarchical HZSM-5 zeolites prepared by post-treatment with alkaline solutions. Journal of Analytical and Applied Pyrolysis. 2018

[66] Wang S, Li Z, Bai X, Yi W, Fu P. Catalytic pyrolysis of lignin with red mud derived hierarchical porous catalyst for alkyl-phenols and hydrocarbons production. Journal of Analytical and Applied Pyrolysis. 2018;**136**:8-17

**29**

**Chapter 3**

**Abstract**

of Energy

clean and eco-friendly solid fuel.

**1. Introduction**

*Krishna Yadav and Sheeja Jagadevan*

Influence of Process Parameters on

Synthesis of Biochar by Pyrolysis

of Biomass: An Alternative Source

Organic matter derived from plants and animals are known as biomass. It has a great potential to be used as an alternate source of energy by employing thermochemical conversion techniques. Among the available techniques, pyrolysis is considered to be the most efficient technique used for the conversion of biomassbased waste into value-added solid, liquid and gaseous products through heating in an oxygen-limited environment. Biochar (solid fuel) is a carbonaceous material and has multiple applications in various fields such as soil health, climate stability, water resource, energy efficiency and conservation. The yield of biochar depends on organic constituents of biomass and the pyrolytic process parameters such as temperature, time, heating rate, purging gas, particle size, catalyst, flow rate, pressure and types of pyrolysis reactors. Suitable conditions for biochar production were observed to be slow pyrolysis, low carrier gas flow rate, acid-catalysed biomass or biomass mixed with some inorganic salts, low heating rate, large particle size, high pressure, longer residence time, low temperature, feedstocks with high lignin content and pyrolysis reactors with lower bed height. Thermal conversion of biomass could be a possible sustainable alternative to provide economically viable,

**Keywords:** biomass, biochar, process parameters, pyrolysis, solid fuel

Biomass refers to organic materials derived from plants and animals and is one of the natural sources of renewable energy. Organic materials present in biomass are the most abundant bio-resource that plays a key role in carbon sequestration by capturing carbon dioxide from the atmosphere through the process of photosynthesis, thereby reducing the greenhouse gases (GHGs). Biomass has a direct effect on energy, environment and economy (3E) of any country [1]. In developing countries such as India, the contribution of biomass towards societal transformations and environment is immense as people are generally directly associated with different forms of biomass. These forms of biomass may vary from forestry, small plants, trees (woody plants), organic wastes, domestic wastes and agricultural wastes. Biomass can be employed as a renewable substitute of fossil fuels because it serves

## **Chapter 3**
