3210 Chapter 26 



Ammonia (NH3) is manufactured from synthesis gas produced from natural 



gas by steam reforming, CH4 + H2O ►SHj + CO, the reverse of equation 26- 



14 (Wiseman 1972). The synthesis gas is enriched in hydrogen by the water shift 

 reaction (equation 26-13). Carbon dioxide and small amounts of unconverted 

 carbon monoxide have to be removed as they poison the ammonia synthesis 

 catalyst. Most of the carbon dioxide is removed by scrubbing with a solution of 

 potassium carbonate. After scrubbing, the gas still contains small amounts of 

 carbon dioxide and carbon monoxide; final removal is accomplished by the 

 methanation reaction (equation 26-14). Both carbon monoxide and carbon diox- 

 ide are converted into methane, which is left in the hydrogen gas as it dos not 

 interfere with ammonia synthesis. In the final step (equation 26-15), ammonia 

 synthesis is carried out by reacting the hydrogen gas with nitrogen gas at high 

 temperature and pressure over an iron catalyst. 



3H2 + N2!!!!!lV 2NH3 (26-15) 



A = - 26 kcal 



Ammonia is used to manufacture fertilizers, explosives, nitric acid, and 

 synthetic fibers. 



High yields of methanol (CH3OH) are also obtainable from synthesis gas 

 (Wender 1980). The water shift reaction alters the hydrogen to carbon monoxide 

 ratio in the medium Btu gas to that required in equation 26-16. 



2H2 + CO !!I!lZ!l^. CH3OH (26- 1 6) 



A = - 26 kcal 



Methanol is a major industrial organic chemical, widely used as a solvent and 

 in synthesis of other materials. Its largest use is for formaldehyde, important to 

 the forest products industry as the basis for synthetic resins such as urea- 

 formaldehyde and phenol-formaldehyde. The resins are used in the manufacture 

 of plywood, particleboard, and plastics. 



Coal to methanol conversion efficiency (59 percent) is higher than that for 

 wood to methanol (38 percent),'"^ and coal conversion facilities will be larger, 

 making them even more efficient. Ammonia from wood appears more promising 

 than methanol. Wood has a lower carbon to hydrogen ratio than coal which 

 favors the wood feedstock. There is also a possibility that natural gas currently 

 being flared in the Middle East will be converted to methanol or other synthesis 

 gas derivatives and exported (Love and Overend 1978). 



Liquid fuels for automobiles. — Methanol and ethanol (see section 26-7 for 

 ethanol process) can both be used to fuel modified automobile engines. Such 

 modification includes the use of fuel injection systems as well as some type of 

 induction heating system to improve vaporization of the alcohols (Park et al. 

 1978ab). Methanol and ethanol can also be blended with gasoline to fuel un- 

 modified automobile engines. Such mixtures are popularly termed gasahol. 



•"^Hokanson and Rowell (1977) projected a yield of 100 gallons of methanol per ovendry ton of 

 wood, based on all process energy coming from the wood; the methanol would have a heat value 

 amounting to 38 percent of projected total energy input. 



