**4. Butanol as raw material in biodiesel production**

By using of butanol as blending material for gasoline and diesel fuels has many advantages towards fuel ethanol (Andersen et al., 2010; Bruno et al., 2009, Duck and Bruce, 1945, Workman et al., 1983), additionally, it can also be used as reactive component in biodiesel production. Butanol can substitute methanol as an alcohol for esterification (Wahlen et al., 2008; Nimcevic et al., 2000, Stoldt and Dave, 1998), it can be an acetal forming compounds for transforming of acetone or other ketones into acetals, or can easily be converted to butyraldehyde for the conversion of glycerol formed during trans-esterification of oils into 1,3-dioxane- or dioxolane type fuel additives (Silva et al., 2010)

#### **4.1 Butanol as blending or reactive component in biodiesel production**

The butanol or the butanol - acetone - ethanol mixture produced in the ABE fermentation have been tested already during the World War II as a blending components for gasoline powered engines (Duck and Bruce, 1945). The engines can be powered with gasoline containing butanol up to 40 % without any technical modification of the engine. The characteristics of pure butanol and ABE solvent mixtures as gasoline or diesel fuel additives have been tested in detail. Generally, the blended mixtures produce almost the same power and thermal efficiency as the gasoline (Schrock and Clark, 1983). The same time the blending has a positive effect via substantially decreasing the NOx content of the exhaust gases.

Since the modern mobile agricultural equipment used in the production of biomass is mostly diesel powered, both ethanol and butanol have been tested for using them as blending components of diesel fuels. By the addition of butanol or ABE blends to diesel fuel the thermal efficiency could be increased, the exhaust gas temperatures are lowered and the soot formation is decreased. The operational parameters of the engine have been studied in detail (Workman et al., 1983). Butanol proved to be an alternative diesel fuel blend. By using butanol as a reactive component in vegetable oil butyl ester preparation or preparation of butanol based acetals, the residual butanol content does not has to be removed from the reaction mixture because it can act as blending component. A special case of the extraction of butanol from aqueous solutions during ABE fermentation is when the extractant is vegatable oil (Welsh and Williams, 1989). The butanol to be extracted can be reacted easily with the extractant. Since the vegetable oil alkyl esters are also extractants of the butanol (Crabbe et al., 2001, Ishizaki et al., 1999), this method can easily be integrated into a catalyst free supercritical trans-esterification technology, when the partially trans-esterified vegetable oil is recycled into the extraction process until its complete transformation into butylester. Since the butanol content extracted in the last step does not need to be separated from the butyl ester product, the method is advantageously integrated into the waste free biodiesel production system.

The use of butanol as a reactive component in biodiesel production has a lot of advantage. First of all, the convenient base catalyzed reaction takes place in homogeneous phase, thus the reaction is faster, the separation of the glycerol is better and the temperature of the reaction can be lowered. The excess of the butanol does not need to be removed from the ester phase. The viscosity of the butylester mixture prepared from soya oil was found to be 4.50 mm2/s at 40 °C, the cetane index was 69. The cloud point of butyl-biodiesel is -3 °C. The flash point and pour point were found to be 44 and –13 °C, respectively (Wahlen et al., 2008). Since butanol reacts with free acids faster than methanol, the high acid containing vegetable oils (free fatty acid content of vegetable oils varies from 7 to 40 %), the waste

An Integrated Waste-Free Biomass Utilization

System for an Increased Productivity of Biofuel and Bioenergy 211

In addition to these possibilities, in case of high acid containing raw vegetable oils, the acid content can also be transformed into butyl-type biofuel and does not need to be recovered as soaps. The abovementioned possibilities can be applied as parts of an integrated system together with other techniques to improve biofuel production, e.g. during the conversion of vegetable oils into methyl esters, the free fatty acids liberated from calcium soaps can be

Glycerol is a very hygroscopic material and its combustion heat is low due to its high oxygen content. Neither its viscosity nor its hygroscopic nature or the miscibility properties indicate direct applicability as a fuel component. However, the glycerol is a reactive compound, thus the glycerol formed in the biodiesel synthesis can be transformed into lower oxygen containing compounds or to their mixture by various reactions (Guerro-Perez et al., 2009, Mota et al., 2009). In order to decrease the oxygen content of the products formed, the most reliable way is water elimination. It can be performed by reduction or by condensation reactions performed with reactants containing O= or HO-functions. The structure and reactivity ensure a series of water elimination (intra or intermolecular)

The glycerol can act as a multifunctional primary and secondary alcohol and can easily be dimerized or polymerised into compounds with residual alcohol functions and alcoholic type reactivity. The glycerol can also be reacted with various other alcohol derivatives (with methanol residue from trans-esterification or with ethanol or butanol from ABE fermentation) into ethers. Transformation into cyclic acetals by using oxo-compounds e.g. acetone from ABE fermentation or acetone – acetaldehyde - butyraldehyde mixtures from the oxidation of not separated ABE products can also be performed. The formed acetals are cyclic dioxolane and dioxane type primary or secondary alcohols, or their stereoisomers (if R1 and R2 are not the same), respectively (Ferreira, et. al., 2010; Kótai and Angyal, 2011).

By partial oxidation of the mixture of primary alcohols from the first ABE fraction containing acetone, ethanol and butanol to aldehydes, a mixture of alcohols and oxocompounds can be prepared. By using the waste glycerol containing methanol from the biodiesel production (or formaldehyde from the methanol oxidation) can provide a complex reaction mixture which can be condensed into an un-separated multicomponent mixture of various oxygenates with lower oxygen content than the starting glycerol. This mixture does not require complete separation into components or individual compounds to use it as a fuel. The reaction has been studied in the presence of various acidic catalysts as sulfuric acid, sulfonated styrene-divinyl-benzene copolymers and p-toluene-sulfonic acid. All of the catalyst gave similar results, the main product have been the 1,3-dioxolane derivatives. Various other components have also been formed in 1-2 % amount of each. The low-boiling fractions contain mainly the starting alcohols, acetone and dialkoxypropane derivatives, the

O O

R1 R2

+

OH OH

O

O

R1

(5)

R2

**4.2 Transformation of the wastes of butanol and biodiesel production into fuel** 

esterified with butanol instead of methanol as well (see Chapter 3.3).

reactions and formation of a variety of compounds.

OH

+

O

R1 R2

HO

HO

cooked oils or other high free acid containing oils can also be used as raw materials. These high free fatty acid containing oils could not be trans-esterified economically with methanol and basic catalysts, and in the presence of acidic catalysts the reactions are very slow.

Solid phase heterogeneous catalysts have not widely been available for use them in industrial scale for these type of oils (Di Serio et al., 2008). The acid catalysts simultaneously catalyze the esterification of the free acids and the trans-esterification of the glycerides however, butyl esters are formed more easier than methyl esters (Wahlen et al., 2008). Methanol, ethanol, n-propanol and n-butanol have been reacted with oleic acid as a model for free fatty acids at 4:1 alcohol/acid molar ratio in the presence of 5 % sulfuric acid ( as catalyst ) at 80 °C for 16 min. The conversion was best (90%) for n-butanol, and the worst in the case of methanol (85%). The difference in trans-esterification activity of C1-4 alcohols in the presence of H2SO4 catalyst is more significant. The methanol can react with the soybean oil (10:1 methanol/bound fatty acid ratio) at 60 °C with 5 % sulfuric acid as catalyst only with 2 % conversion within 32 min. By using 12:1 alcohol/soybean oil ratio and 80 °C temperature, the methanol and ethanol gave 18 % conversion in 16 min, while the propanol and butanol showed 50 % conversion during the same time. The reaction of butanol with vegetable oils at a mixed feedstock containing oleic acid and soya oil with a ratio of 5:1-1:5 required minimum 2:1 butanol/fatty acid (free and bound) molar ratio at 110 °C in the presence of 5% H2SO4 catalyst . Using microwave heating at 6:1 butanol/soybean oil ratio in the presence of 3 % H2SO4, a 98 % conversion was achieved within 50 min. By using microwave heating the trans-esterification reaction of the vegetable oils with butanol can be performed without any catalyst under supercritical conditions (Geuens et al., 2008). Since the butanol boiling point is higher than methanol boiling point, the reactions takes place at higher temperatures without using extremely large pressures. The best results were achieved at 310 °C and 80 bar pressure in SiC coated tube reactor. The lack of the catalyst results very a small amount of glycerol without soap formation. The excess of butanol does not need to be separated from the ester phase or can be flashed out from the glycerol phase for recycling.

By using n-butanol instead of methanol and butoxylation of the unsaturated alkyl chain improve the ratio of the fossil energy used to produce a unit of renewable energy source. The highly unsaturated oils cause gum and deposit formation, but their epoxidation with peroxy-acetic acid and contacting the epoxides with n-butanol in the presence of 2 % sulfuric acid as catalyst at 80 C°, results 100% conversion of the epoxides. The selectivity is 87 %, and the 46 % conversion of the unsaturated alkyl chains does not cause an increase in the cloud point (Smith et al., 2009). As it can be seen, the butanol increases the amount of the biofuel produced from raw vegetable oil, by molar weight increasing referring to methyl esters (Table 3., Nimcevic et al., 2000), by incorporating butoxy groups into the unsaturated alkyl chains and by mixing the excess butanol with the formed fuel.


Table 3. Alcohol inputs in the production of biodiesel

cooked oils or other high free acid containing oils can also be used as raw materials. These high free fatty acid containing oils could not be trans-esterified economically with methanol and basic catalysts, and in the presence of acidic catalysts the reactions are very slow.

Solid phase heterogeneous catalysts have not widely been available for use them in industrial scale for these type of oils (Di Serio et al., 2008). The acid catalysts simultaneously catalyze the esterification of the free acids and the trans-esterification of the glycerides however, butyl esters are formed more easier than methyl esters (Wahlen et al., 2008). Methanol, ethanol, n-propanol and n-butanol have been reacted with oleic acid as a model for free fatty acids at 4:1 alcohol/acid molar ratio in the presence of 5 % sulfuric acid ( as catalyst ) at 80 °C for 16 min. The conversion was best (90%) for n-butanol, and the worst in the case of methanol (85%). The difference in trans-esterification activity of C1-4 alcohols in the presence of H2SO4 catalyst is more significant. The methanol can react with the soybean oil (10:1 methanol/bound fatty acid ratio) at 60 °C with 5 % sulfuric acid as catalyst only with 2 % conversion within 32 min. By using 12:1 alcohol/soybean oil ratio and 80 °C temperature, the methanol and ethanol gave 18 % conversion in 16 min, while the propanol and butanol showed 50 % conversion during the same time. The reaction of butanol with vegetable oils at a mixed feedstock containing oleic acid and soya oil with a ratio of 5:1-1:5 required minimum 2:1 butanol/fatty acid (free and bound) molar ratio at 110 °C in the presence of 5% H2SO4 catalyst . Using microwave heating at 6:1 butanol/soybean oil ratio in the presence of 3 % H2SO4, a 98 % conversion was achieved within 50 min. By using microwave heating the trans-esterification reaction of the vegetable oils with butanol can be performed without any catalyst under supercritical conditions (Geuens et al., 2008). Since the butanol boiling point is higher than methanol boiling point, the reactions takes place at higher temperatures without using extremely large pressures. The best results were achieved at 310 °C and 80 bar pressure in SiC coated tube reactor. The lack of the catalyst results very a small amount of glycerol without soap formation. The excess of butanol does not need to be separated from the ester phase or can be flashed out from the glycerol phase

By using n-butanol instead of methanol and butoxylation of the unsaturated alkyl chain improve the ratio of the fossil energy used to produce a unit of renewable energy source. The highly unsaturated oils cause gum and deposit formation, but their epoxidation with peroxy-acetic acid and contacting the epoxides with n-butanol in the presence of 2 % sulfuric acid as catalyst at 80 C°, results 100% conversion of the epoxides. The selectivity is 87 %, and the 46 % conversion of the unsaturated alkyl chains does not cause an increase in the cloud point (Smith et al., 2009). As it can be seen, the butanol increases the amount of the biofuel produced from raw vegetable oil, by molar weight increasing referring to methyl esters (Table 3., Nimcevic et al., 2000), by incorporating butoxy groups into the unsaturated

**Combustion value Alcohol molar** 

**ester molecule MJ/kg MJ/kmol** 

**fraction in the** 

alkyl chains and by mixing the excess butanol with the formed fuel.

Table 3. Alcohol inputs in the production of biodiesel

Methyl 39.83 14156 8.7 Ethyl 40.03 14787 12.2 Butyl 40.52 16103 18.4

for recycling.

**Ester** 

In addition to these possibilities, in case of high acid containing raw vegetable oils, the acid content can also be transformed into butyl-type biofuel and does not need to be recovered as soaps. The abovementioned possibilities can be applied as parts of an integrated system together with other techniques to improve biofuel production, e.g. during the conversion of vegetable oils into methyl esters, the free fatty acids liberated from calcium soaps can be esterified with butanol instead of methanol as well (see Chapter 3.3).

#### **4.2 Transformation of the wastes of butanol and biodiesel production into fuel**

Glycerol is a very hygroscopic material and its combustion heat is low due to its high oxygen content. Neither its viscosity nor its hygroscopic nature or the miscibility properties indicate direct applicability as a fuel component. However, the glycerol is a reactive compound, thus the glycerol formed in the biodiesel synthesis can be transformed into lower oxygen containing compounds or to their mixture by various reactions (Guerro-Perez et al., 2009, Mota et al., 2009). In order to decrease the oxygen content of the products formed, the most reliable way is water elimination. It can be performed by reduction or by condensation reactions performed with reactants containing O= or HO-functions. The structure and reactivity ensure a series of water elimination (intra or intermolecular) reactions and formation of a variety of compounds.

The glycerol can act as a multifunctional primary and secondary alcohol and can easily be dimerized or polymerised into compounds with residual alcohol functions and alcoholic type reactivity. The glycerol can also be reacted with various other alcohol derivatives (with methanol residue from trans-esterification or with ethanol or butanol from ABE fermentation) into ethers. Transformation into cyclic acetals by using oxo-compounds e.g. acetone from ABE fermentation or acetone – acetaldehyde - butyraldehyde mixtures from the oxidation of not separated ABE products can also be performed. The formed acetals are cyclic dioxolane and dioxane type primary or secondary alcohols, or their stereoisomers (if R1 and R2 are not the same), respectively (Ferreira, et. al., 2010; Kótai and Angyal, 2011).

By partial oxidation of the mixture of primary alcohols from the first ABE fraction containing acetone, ethanol and butanol to aldehydes, a mixture of alcohols and oxocompounds can be prepared. By using the waste glycerol containing methanol from the biodiesel production (or formaldehyde from the methanol oxidation) can provide a complex reaction mixture which can be condensed into an un-separated multicomponent mixture of various oxygenates with lower oxygen content than the starting glycerol. This mixture does not require complete separation into components or individual compounds to use it as a fuel. The reaction has been studied in the presence of various acidic catalysts as sulfuric acid, sulfonated styrene-divinyl-benzene copolymers and p-toluene-sulfonic acid. All of the catalyst gave similar results, the main product have been the 1,3-dioxolane derivatives. Various other components have also been formed in 1-2 % amount of each. The low-boiling fractions contain mainly the starting alcohols, acetone and dialkoxypropane derivatives, the

An Integrated Waste-Free Biomass Utilization

*Dialkoxi-methanes* 

*Dialkoxyethanes* 

*Dialkoxybutanes* 

*1,3-Dioxolanes (2 isomers)* 

2006).

*1,3-Dioxanes* 

System for an Increased Productivity of Biofuel and Bioenergy 213

**Compounds Alcohol Oxo-reactants Fraction Peak area** 

(MeO)2CH2 MeOH CH2O I-II 2 (EtO)2CH2 EtOH CH2O I-IV 5 BuOCH2OMe BuOH,MeOH CH2O I-III 15 BuOCH2OEt BuOH,EtOH CH2O I-IV 14 (BuO)2CH2 BuOH CH2O II-V 5

(BuO)(MeO)CHCH3 BuOH,MeOH CH3CHO I-IV 1 (BuO)2CHCH3 BuOH CH3CHO IV-V 2

(BuO)2CHCH2CH2CH3 BuOH PrCHO IV-V 2

2-Me-4-CH2OH-1,3-dioxolane glycerol CH3CHO I-V 6 2-Me-4-CH2OH-1,3-dioxolane glycerol CH3CHO V 4 2-Pr-4-CH2OH-1,3-dioxolane glycerol PrCHO V 12 2-Pr-4-CH2OH-1,3-dioxolane glycerol acetone IV-V 11

2-Me-5-OH-1,3-dioxane glycerol CH3CHO IV-V 2 2-Pr-5-OH-1,3-dioxane glycerol PrCHO V 3 Table 5. The identified components of the reaction between biodiesel waste and partially

**Glycerol formal content** 0 0.5 % 1% 5% 10% **Density, g/cm3** 0.8592 0.8620 0.8631 0.8711 0.8802 **Freezing point, °C** -7 -16 -21 -21 -21 **Viscosity at -10 C°, cSt** Solid No data 548.2 343.3 No data

Not only acetals, but other ether type components can also be used as fuel blends. The condensation products formed with alcoholic functions can be used for further acetal formation. The dioxolane and dioxane type compounds with alcoholic function groups can be esterified or etherified in a further reaction into other valuable products (Jalinski,

**RME + glycerol formal**

oxidized ABE production waste streams in the presence of Varion KSM catalyst

Table 6. Effect of glycerol formal on properties of methyl ester of rapeseed oil

higher fractions contain mainly 2,2-dimethyl-4-hydroxymethyl-1,3-dioxolane, its mixture with the starting alcohols and the formed dialkoxypropanes. The 2,2-dimethyl-5-hydroxy-1,3-dioxane has appeared only in the distillation residue because its boiling point is higher than 120 °C. In the acetalization of acetone with glycerol the two possible isomers 1,3 dioxolane or 1,3-dioxane ring containing products can also be formed in the 1,2- or 1,3-type cyclization reactions. The molar ratio of the dioxolane /dioxane and the yields slightly depend on the type of the acidic catalyst. The composition of a typical reaction mixture is illustrated in Table 4. The main product is the 2,2-dimethyl-4-hydroxymethyl-1,3-dioxolane, a smaller amount of the 2,2-dimethyl-5-hydroxy-1,3-dioxane and dialkoxy-propanes are also formed. Two mixed methoxy-group containing acetals are formed, as well. Thus, it seems to be probably that the primarily formed 2,2-dimethoxypropane has reacted with the higher primary alcohols. In order to increase the complexity of the mixture, which is an optimal situation for fuels, the glycerol - MeOH mixture was mixed with the first un-separated fraction of the butanol production which contains EtOH, acetone and BuOH, and reacted with various oxo- compounds prepared from the abovementioned alcohols by oxidation (CH2O, CH3CHO and butyraldehyde).


Table 4. The acetals formed in the reaction of ABE solvents and glycerol containing methanol with Varion KSM acidic ion exchanger catalyst at 3 h reflux

It can be seen that from the same molar amounts of the alcohols the acetone prefers the reaction with the glycerol, or the dialkoxy-propanes formed reacts with the glycerol via reformation of the alcohols.

In this way, the waste stream from ABE and biodiesel production with or without oxidative treatment results an un-separated mixture containing various alcoholic and oxo-components which can react with each other in various water elimination reactions to from a variety of lower oxygen containing acetal/ether type compounds. The formed mixture contains components with a wide boiling range. Table 5 contains the product distribution in a mixture formed in the reaction of 1-1 equivalents of acetone, acetaldehyde, n-butyaldehyde and formaldehyde by 1 equivalent of glycerol and 2-2 equivalents of MeOH, EtOH and BuOH with Varion KSM sulfonated ion exchanger as catalyst under 3 h reflux. The reaction mixture has been separated into five fractions to study the distribution of each component formed and the starting material in the fractions. Depending on the reaction conditions, molar ratios of each reactant and the catalyst, the product distribution can be varied. Two isomers of 2-alkyl-4-hydroxymethyl dioxolanes are formed which have different boiling points. As an example, the effect of glycerol formal on the properties of the biodiesels can be seen in Table. 6. (Puche, 2009)

higher fractions contain mainly 2,2-dimethyl-4-hydroxymethyl-1,3-dioxolane, its mixture with the starting alcohols and the formed dialkoxypropanes. The 2,2-dimethyl-5-hydroxy-1,3-dioxane has appeared only in the distillation residue because its boiling point is higher than 120 °C. In the acetalization of acetone with glycerol the two possible isomers 1,3 dioxolane or 1,3-dioxane ring containing products can also be formed in the 1,2- or 1,3-type cyclization reactions. The molar ratio of the dioxolane /dioxane and the yields slightly depend on the type of the acidic catalyst. The composition of a typical reaction mixture is illustrated in Table 4. The main product is the 2,2-dimethyl-4-hydroxymethyl-1,3-dioxolane, a smaller amount of the 2,2-dimethyl-5-hydroxy-1,3-dioxane and dialkoxy-propanes are also formed. Two mixed methoxy-group containing acetals are formed, as well. Thus, it seems to be probably that the primarily formed 2,2-dimethoxypropane has reacted with the higher primary alcohols. In order to increase the complexity of the mixture, which is an optimal situation for fuels, the glycerol - MeOH mixture was mixed with the first un-separated fraction of the butanol production which contains EtOH, acetone and BuOH, and reacted with various oxo- compounds prepared from the abovementioned alcohols by oxidation

**Compound Alcohol Fraction Peak area B.p. range**  MeC(OMe)2Me MeOH I-IV 1 58-99 °C MeC(OMe)(OEt)Me MeOH, EtOH I-IV 2 58-99 °C MeC(OEt)2Me EtOH III,IV 1 71-99 °C MeC(OMe)(OBu)Me MeOH, BuOH I-IV 1 58-99 °C

3-dioxolane glycerol III-VI 88 71-120 °C<

3-dioxane glycerol VI 2 120 °C<

It can be seen that from the same molar amounts of the alcohols the acetone prefers the reaction with the glycerol, or the dialkoxy-propanes formed reacts with the glycerol via re-

In this way, the waste stream from ABE and biodiesel production with or without oxidative treatment results an un-separated mixture containing various alcoholic and oxo-components which can react with each other in various water elimination reactions to from a variety of lower oxygen containing acetal/ether type compounds. The formed mixture contains components with a wide boiling range. Table 5 contains the product distribution in a mixture formed in the reaction of 1-1 equivalents of acetone, acetaldehyde, n-butyaldehyde and formaldehyde by 1 equivalent of glycerol and 2-2 equivalents of MeOH, EtOH and BuOH with Varion KSM sulfonated ion exchanger as catalyst under 3 h reflux. The reaction mixture has been separated into five fractions to study the distribution of each component formed and the starting material in the fractions. Depending on the reaction conditions, molar ratios of each reactant and the catalyst, the product distribution can be varied. Two isomers of 2-alkyl-4-hydroxymethyl dioxolanes are formed which have different boiling points. As an example, the effect of glycerol formal on the properties of the biodiesels can be

Table 4. The acetals formed in the reaction of ABE solvents and glycerol containing

methanol with Varion KSM acidic ion exchanger catalyst at 3 h reflux

(CH2O, CH3CHO and butyraldehyde).

2,2-Me2-4-CH2OH-1,

2,2-dimethyl-5-OH-1,

formation of the alcohols.

seen in Table. 6. (Puche, 2009)


Table 5. The identified components of the reaction between biodiesel waste and partially oxidized ABE production waste streams in the presence of Varion KSM catalyst


Table 6. Effect of glycerol formal on properties of methyl ester of rapeseed oil

Not only acetals, but other ether type components can also be used as fuel blends. The condensation products formed with alcoholic functions can be used for further acetal formation. The dioxolane and dioxane type compounds with alcoholic function groups can be esterified or etherified in a further reaction into other valuable products (Jalinski, 2006).

An Integrated Waste-Free Biomass Utilization

of fuel mixture can be further increased.

glycerol ethers (Barrault et al., 1998).

biocomponent into fuels until 2020).

component in biofuel production.

System for an Increased Productivity of Biofuel and Bioenergy 215

Since the glycerol has hydroxyl groups with various reactivity, depending on the catalyst and the reaction conditions, various dimers and even more type of oligomers and polymers can be formed. By using these dimers (oligomers) in acetal forming reactions, the complexity

Not only water elimination, but increasing carbon chain length can decrease the relative oxygen content and increase the combustion heat and improve the fuel properties. Selective etherification of glycerol or the free alcoholic function groups of the condensates formed from the glycerol. The alcohol functions of glycerol or other alcohols formed during polymerization of glycerol or acetal production can easily be alkylated by reaction with isoalkenes (Klepacova et al., 2003). Trans-esterification of crude soya oil with methanol in the presence of NaOH catalyst, then separating the glycerol phase reacted with the mixture in the presence of Amberlyte-15 acidic ion exchanger catalysts for 2 when isobutylene converts the glycerol into ethers. The mixture formed contains 9 % triether, 47 % diether, 21 % mono-ether, 5 % unreacted glycerol, 14 % isobutylene and 4 % methyl esters. By separating and recycling the starting materials and the mono-ethers the residue can be mixed with the ester phase formed in the trans-esterification when a mixture is formed containing 12 % ethers and 88 % methyl esters. Its clouding point is below 0 °C and having a viscosity of 5.94 cSt which is lower with 9 oC and 0.5 cSt, respectively, if this parameters are compared to the ester phase without the addition of

The oxygenate mixtures produced in the abovementioned ways ensures that a very complex mixture of compounds could be manufactured, in which all components of the ABE fermentation and biodiesel production turn into fuel component. These blending materials have very advantageous properties, decrease the viscosity, decrease the pouring point and soot formation and improve the cetane number. In this way, vegetable oil ester (mainly butyl ester), butanol and acetal or other oxygenate mixture containing biodiesels are formed with much higher production efficiency compared to the classical vegetable oil methyl esters. Thus, our technology can provide an aromatic hydrocarbon-free fuel which can be used even in highly populated large cities. Since biodiesels, fossil diesels and the gasolines can be mixed with pure butanol up to an amount of 40% without influencing the fuel properties, and these oxygenates can also be used around in an amount of 20 %, these new kind of fuel mixtures can provide a solution for the EU demand (incorporation of 20 %

It is an obvious question that which bioalcohol should be used for the replacement of methanol in biodiesel production, or it is worth to change the ethanol blends of fuels to

Comparison of technical and economical assessment for corn and switch grass fermented by yeast into ethanol and C. acetobutylicum into butanol showed (Pfromm et al., 2010) that biobutanol production is not competitive with ethanol production. As an example, the carbon balances for corn are illustrated in Fig. 3. However, involving new technologies, new raw materials (e.g. sugar sorghum) and the extractive fermentation processes combined with immobilized cell techniques, and decrease the production cost by means of the new separation technologies, the butanol becomes competitive as blending or reactive

butanol which has much better fuel properties and energy content than the ethanol.

**5. Other aspects of the integrated biomass utilization system** 

The general scheme for transformation of glycerol into fuel components with ABE components is given by eqn. (6), where R1, R2 and R3 are Me, Et, Bu, CH3C(O)-, C3H7C(O)-, R4 and R5 are H, Me, Pr, and R6 means Me, Et, Bu, CH3C(O)-, C3H7C(O) or other groups derived from the alcohol-type glycerol condensation products. Transformation of all three hydroxyl groups of the glycerol into alkoxy groups (methoxy, ethoxy or butoxy), or esterifying them with low carbon chain carboxylic acids (acetic acid, butyric acid) decrease the hydrophil nature and oxygen content and increase the combustion heat, the miscibility with fuel. Thus, these compounds are advantageous fuel additives (Mota et al., 2009). Since ethanol, butanol, methanol, acetic and butyric acid are products/by-products and intermediates of the ABE fermentation or biodiesel production, these reactions are candidates for integration into a complex biomass utilization system. The intermediate acetic and butyric acid can also be used as acylation agents for the cyclic acetals, and in this way all product of the ABE fermentation become fuel component. Not only these organic acids but carbonic acid can also acts as acid residue in the esterified products. The carbonate compounds prepared form acetals formed from n-butyraldehyde or acetone and glycerol lowering the soot and the particulate formation during ignition of the diesel fuels (Delfort, 2004). Alkylation or acylation of free hydroxy-groups in 1,3-dioxolane and dioxane type fuel blends increases their solubility with two order of magnitudes (Jalinski, 2006)].

It is obvious, that glycerol which has primary and secondary alcohol functions, and can be condensed with itself to different kind of polyglycerols (Barrault et al., 1998). Polyglycerols can be obtained at high temperature vapor phase reaction over solid catalysts as alkali and alkaline earth metal hydroxides or carbonates, zeolites, La-ion-exchanged zeolites and ion-exchanger resins (Barrault et al., 1998). In the presence of resins, the main product is the diglycerol.

O

OR6

O

R5 R4

OH

O O

R4 R5

OR6

O

R1

(6)

(7)

R3O OR2

HO OH

The general scheme for transformation of glycerol into fuel components with ABE components is given by eqn. (6), where R1, R2 and R3 are Me, Et, Bu, CH3C(O)-, C3H7C(O)-, R4 and R5 are H, Me, Pr, and R6 means Me, Et, Bu, CH3C(O)-, C3H7C(O) or other groups derived from the alcohol-type glycerol condensation products. Transformation of all three hydroxyl groups of the glycerol into alkoxy groups (methoxy, ethoxy or butoxy), or esterifying them with low carbon chain carboxylic acids (acetic acid, butyric acid) decrease the hydrophil nature and oxygen content and increase the combustion heat, the miscibility with fuel. Thus, these compounds are advantageous fuel additives (Mota et al., 2009). Since ethanol, butanol, methanol, acetic and butyric acid are products/by-products and intermediates of the ABE fermentation or biodiesel production, these reactions are candidates for integration into a complex biomass utilization system. The intermediate acetic and butyric acid can also be used as acylation agents for the cyclic acetals, and in this way all product of the ABE fermentation become fuel component. Not only these organic acids but carbonic acid can also acts as acid residue in the esterified products. The carbonate compounds prepared form acetals formed from n-butyraldehyde or acetone and glycerol lowering the soot and the particulate formation during ignition of the diesel fuels (Delfort, 2004). Alkylation or acylation of free hydroxy-groups in 1,3-dioxolane and dioxane type fuel

blends increases their solubility with two order of magnitudes (Jalinski, 2006)].

OH

OH

OH

+

HO <sup>+</sup>

HO O OH OH OH

O

HO OH

HO O OH

HO

It is obvious, that glycerol which has primary and secondary alcohol functions, and can be condensed with itself to different kind of polyglycerols (Barrault et al., 1998). Polyglycerols can be obtained at high temperature vapor phase reaction over solid catalysts as alkali and alkaline earth metal hydroxides or carbonates, zeolites, La-ion-exchanged zeolites and ion-exchanger resins (Barrault et al., 1998). In the presence of resins, the main product is the diglycerol.

+

HO

O

O

O

O

HO O

O

OH

OH

OH

Since the glycerol has hydroxyl groups with various reactivity, depending on the catalyst and the reaction conditions, various dimers and even more type of oligomers and polymers can be formed. By using these dimers (oligomers) in acetal forming reactions, the complexity of fuel mixture can be further increased.

Not only water elimination, but increasing carbon chain length can decrease the relative oxygen content and increase the combustion heat and improve the fuel properties. Selective etherification of glycerol or the free alcoholic function groups of the condensates formed from the glycerol. The alcohol functions of glycerol or other alcohols formed during polymerization of glycerol or acetal production can easily be alkylated by reaction with isoalkenes (Klepacova et al., 2003). Trans-esterification of crude soya oil with methanol in the presence of NaOH catalyst, then separating the glycerol phase reacted with the mixture in the presence of Amberlyte-15 acidic ion exchanger catalysts for 2 when isobutylene converts the glycerol into ethers. The mixture formed contains 9 % triether, 47 % diether, 21 % mono-ether, 5 % unreacted glycerol, 14 % isobutylene and 4 % methyl esters. By separating and recycling the starting materials and the mono-ethers the residue can be mixed with the ester phase formed in the trans-esterification when a mixture is formed containing 12 % ethers and 88 % methyl esters. Its clouding point is below 0 °C and having a viscosity of 5.94 cSt which is lower with 9 oC and 0.5 cSt, respectively, if this parameters are compared to the ester phase without the addition of glycerol ethers (Barrault et al., 1998).

The oxygenate mixtures produced in the abovementioned ways ensures that a very complex mixture of compounds could be manufactured, in which all components of the ABE fermentation and biodiesel production turn into fuel component. These blending materials have very advantageous properties, decrease the viscosity, decrease the pouring point and soot formation and improve the cetane number. In this way, vegetable oil ester (mainly butyl ester), butanol and acetal or other oxygenate mixture containing biodiesels are formed with much higher production efficiency compared to the classical vegetable oil methyl esters. Thus, our technology can provide an aromatic hydrocarbon-free fuel which can be used even in highly populated large cities. Since biodiesels, fossil diesels and the gasolines can be mixed with pure butanol up to an amount of 40% without influencing the fuel properties, and these oxygenates can also be used around in an amount of 20 %, these new kind of fuel mixtures can provide a solution for the EU demand (incorporation of 20 % biocomponent into fuels until 2020).
