Energy, fuels, and chemicals 3209 



CHEMICALS AND FUELS PRODUCTION 



Synthesis gas (hydrogen and carbon monoxide) can be used to produce 

 several important chemicals and fuels (Wender 1980). Methane, hydrogen, 

 ammonia, methanol, ethylene glycol, and gasoline can be made directly from 

 synthesis gas. Additionally, a high octane gasoline can be produced from metha- 

 nol in a one-step process. 



Medium Btu gas from wood gasification should be well suited for use as 

 synthesis gas because of its high hydrogen and carbon monoxide content. On the 

 other hand, low Btu gas would not be so well suited since large amounts of 

 nitrogen would have to be removed to convert it to synthesis gas. An exception 

 might be in ammonia production. 



Reed (1980), with a high-pressure downdraft design (fig. 26-27) using oxy- 

 gen, propane, and nitrogen to gasify wood pellets, produced clean synthesis gas 

 comprised solely of hydrogen and carbon monoxide. 



Hydrogen, methane, ammonia, and methanol. — Hydrogen can be pro- 

 duced from synthesis gas by the water shift reaction (Wender 1980). Hydrogen 

 already in the synthesis gas remains unchanged, but added water reacts at high 

 temperature with carbon monoxide and a catalyst to yield hydrogen. 



CO + H.Oif!!!!^ CO2 + H2 



AH = -9.84 kcal ' (26-13) 



Carbon dioxide formed can be removed from the gas stream to give pure 

 hydrogen gas. The reaction is also used to obtain hydrogen to carbon monoxide 

 ratios appropriate for certain syntheses. Methanol production requires 2H2: ICO, 

 while methane requires SH^ilCO. 



Hydrogen holds much promise as an environmentally clean fuel; its combus- 

 tion yields only water and heat energy. A promising new technology is the 

 development of metal hydrides for the safe storage, shipping, and use of hydro- 

 gen as a fuel. Although its general use may be in the somewhat distant future, 

 increased use of hydrogen as a transportation fuel may be expected, especially 

 for mass transit in areas with air pollution problems. 



Methane (CH4) can be produced by the methanation reaction shown below: 



3H2 + CO'—L^ CH4 + H.O 



AH = -49.3 kcal " (26-14) 



Since this reaction requires 3 moles of hydrogen to one mole of carbon monox- 

 ide, the water shift reaction can be used to adjust this ratio in the medium Btu gas 

 and maximize the yield of methane. Methane is a suitable substitute for natural 

 gas inasmuch as natural gas is composed primarily of methane (85 percent) with 

 lesser amounts of other hydrocarbons and nitrogen. While the relatively low Btu 

 values of low and medium Btu gas from wood gasification preclude storage or 

 transport over any distance, conversion to methane provides a route for the 

 production of a pipeline-quality substitute (950 Btu/sdcO for natural gas (Bliss 

 and Blake 1977). 



