**4. Fischer-Tropsch diesel production**

One of the commercially accessible methods of manufacturing clean synthetic fuel from syngas is Fischer-Tropsch technique. Industrially speaking, coal/pet-coke/ biomass emits huge quantities of carbon dioxide that can be used to enhance the fuel production.

Because of the increased level of carbon dioxide in atmosphere and also the depletion of conventional fuels, scientific researches recommend the chemical recycling of carbon dioxide into renewable fuel and more added-value chemicals [8].

The production of synthetic fuel from syngas is favorable process owing to its portability as well as to its large quantity of chemical energy, saved without further processing and easy to use.

The raw syngas undergoes multiple energy intensive processes to fulfill the stoichiometric requirements (2.05 < H2/CO < 2.15) for Fischer-Tropsch, including removal of carbon dioxide for subsequent sequestrating, to mitigate negative carbon dioxide emission impacts. Absorption techniques with mono- and diethyl amines are the most popular technology for the removal of carbonic gases from syngas. These procedures are energy intensive owing to the intermediate steps of absorption, desorption, and compression.

The main Fischer-Tropsch reaction is to produce aliphatic long-chain saturated hydrocarbons from syngas (Eq. (3)). There are a lot of side reactions that occur on active sites accompanying the main reaction (Eq. (4)).

Original FT reaction:

$$\text{nCO} + 2\text{nH}\_2 \rightarrow \text{(CH}\_2\text{)n} + \text{nH}\_2\text{O}; \Delta\text{H} 298\text{ K} = -152\text{ kJ}\text{mol}^{-1}\tag{3}$$

Carbon dioxide is also a Fischer-Tropsch waste product and considered to effect the targeted yield of the produced liquid hydrocarbons, and also the presence of carbon dioxide can lead to a substantial reduction in the catalytic reaction activity [10]. This is due to the water-gas-shift (WGS) reaction (Eq. (4)) by which the hydrogen lack is overcome and releases a large quantity of carbon dioxide during the reaction.

Water-gas-shift reaction:

$$\text{CO} + \text{H}\_2\text{O} \rightleftharpoons \text{CO}\_2 + \text{H}\_2; \Delta \text{H} 298 \text{ K} = -41.2 \text{ kJ/mol}^{-1} \tag{4}$$

It was reported that the carbon dioxide found in syngas plays the role of an oxidizing agent on reduced Co/γ-Al2O3, which effects the conversion of carbon monoxide and C5+ hydrocarbons selectivity. Another role for the carbon dioxide was proposed as an inert gas in cobalt-based catalysts [10]. Another approach described the formation of dioxide during the Fischer-Tropsch reaction that will reduce with the using of syngas-containing carbon dioxide as the equilibrium tends to be directed in the inverse direction without affecting the Fischer-Tropsch process.

The change in equilibrium of carbon dioxide is the first step in Fischer-Tropsch (Eq. (6)), resulting in an enhanced proportion of oxygen atoms in carbon monoxide, which is retrieved by water over iron-based carboxylic catalysts comprising syngas. The produced carbon monoxide from this shift is further processed in the Fischer-Tropsch technique.

Boudouard reaction:

$$\text{ZCO} \rightleftharpoons \text{CO}\_2 + \text{C(s)}; \Delta \text{H} \text{298 K} = -172.5 \text{ kJ} \text{mol}^{-1} \tag{5}$$

Modified CO2-FT reaction:

$$\rm CO\_2 + H\_2 \rightleftharpoons CO \rightarrow 2nH\_2 \rightarrow (CH\_2)\text{n} + nH\_2O + H\_2O \tag{6}$$

Direct CO2 hydrogenation:

$$\text{nCO}\_2 + 2\text{nH}\_2 \rightarrow \text{(CuH}\_2\text{n)}\text{n=2-4 + nH}\_2\text{O}\tag{7}$$

The low selectiveness of 10Co5Fe supported on carbon nanofiber catalyst to produce methane during Fischer-Tropsch reaction. The increase in carbon dioxide levels in syngas produces only 22% of C5+ hydrocarbons.

Fe3O4 catalyzes the transformation of carbon dioxide into carbon monoxide through the inverse response of the water-gas-shift system, while χ-Fe5C2 is involved in hydrocarbon production.

Catalytic transformation of syngas was demonstrated with the use of bifunctional Fe-Co, backed on hierarchical HZSM-5, of 16% (mol%) carbon dioxide in hydrogen deficiencies. 1Fe:2Co (wt%) is the most effective bimetallic mixture of several combinations of iron and cobalt.

## **5. Conclusion**


**29**

**Author details**

(EPRI), Egypt

Raghda Ahmed El-Nagar1

*Syngas Production, Properties, and Its Importance DOI: http://dx.doi.org/10.5772/intechopen.89379*

meters per the mass of the feedstock.

manufacturing clean synthetic fuel from syngas.

• Syngas can be produced from gasification of biomass/coal or reforming of natural gas, and the yield is measured by the mass of the produced in cubic

• Fischer-Tropsch technique is one of the commercially accessible methods of

\* and Alaa Ali Ghanem<sup>2</sup>

\*Address all correspondence to: raghda\_elnagar@yahoo.com

provided the original work is properly cited.

1 Analysis and Evaluation Department, Egyptian Petroleum Research Institute

2 Production Department, Egyptian Petroleum Research Institute (EPRI), Egypt

© 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,

*Syngas Production, Properties, and Its Importance DOI: http://dx.doi.org/10.5772/intechopen.89379*

*Sustainable Alternative Syngas Fuel*

Water-gas-shift reaction:

Fischer-Tropsch technique. Boudouard reaction:

Modified CO2-FT reaction:

Direct CO2 hydrogenation:

involved in hydrocarbon production.

several combinations of iron and cobalt.

major syngas properties.

during the reaction.

Carbon dioxide is also a Fischer-Tropsch waste product and considered to effect the targeted yield of the produced liquid hydrocarbons, and also the presence of carbon dioxide can lead to a substantial reduction in the catalytic reaction activity [10]. This is due to the water-gas-shift (WGS) reaction (Eq. (4)) by which the hydrogen lack is overcome and releases a large quantity of carbon dioxide

It was reported that the carbon dioxide found in syngas plays the role of an oxidizing agent on reduced Co/γ-Al2O3, which effects the conversion of carbon monoxide and C5+ hydrocarbons selectivity. Another role for the carbon dioxide was proposed as an inert gas in cobalt-based catalysts [10]. Another approach described the formation of dioxide during the Fischer-Tropsch reaction that will reduce with the using of syngas-containing carbon dioxide as the equilibrium tends to be directed in the inverse direction without affecting the Fischer-Tropsch process. The change in equilibrium of carbon dioxide is the first step in Fischer-Tropsch (Eq. (6)), resulting in an enhanced proportion of oxygen atoms in carbon monoxide, which is retrieved by water over iron-based carboxylic catalysts comprising syngas. The produced carbon monoxide from this shift is further processed in the

CO + H2O ⇌ CO2 + H2;ΔH298 K = −41.2 kJmol−1 (4)

2CO ⇌ CO2 + C(s);ΔH298 K = −172.5 kJmol−1 (5)

CO2 + H2 ⇌ CO → 2nH2 → (CH2)n + nH2O + H2O (6)

The low selectiveness of 10Co5Fe supported on carbon nanofiber catalyst to produce methane during Fischer-Tropsch reaction. The increase in carbon dioxide

Fe3O4 catalyzes the transformation of carbon dioxide into carbon monoxide through the inverse response of the water-gas-shift system, while χ-Fe5C2 is

Catalytic transformation of syngas was demonstrated with the use of bifunctional Fe-Co, backed on hierarchical HZSM-5, of 16% (mol%) carbon dioxide in hydrogen deficiencies. 1Fe:2Co (wt%) is the most effective bimetallic mixture of

• The synthesis gas is defined as a gas with H2 and CO as the main components

• The flammability limit of the syngas and the laminar flame velocity are the

levels in syngas produces only 22% of C5+ hydrocarbons.

nCO2 + 2nH2 → (CnH2n)n = 2–4 + nH2O (7)

**28**

**5. Conclusion**

of fuel.

