3212 



Chapter 26 



WOOD- 



STEAM ■ 



OXYGEN ■ 



> GASOLINE 



Figure 26-29. — Overall scheme for the production of gasoline from wood. Selling the 

 methane produced in the gasification step instead of reconverting it into synthesis gas 

 would lower the cost of methanol production. (Drawing after Meisel et al. 1976.) 



90 to 100. Some of the remaining lower-boiling hydrocarbons can be converted 

 into gasoline by an additional alkylation reaction. When this is done, total 

 gasoline yield approaches 90 percent. The remaining 10 percent is valuable 

 liquefied petroleum gas (LPG) (Meisel et al. 1976). 



The primary source of methanol for the Mobil process is expected to be coal in 

 the United States and perhaps natural gas in some other countries. However, in 

 some areas it may be economically feasible to use wood as a source of methanol 

 (fig. 26-29). 



The Fischer-Tropsch reaction also makes hydrocarbons from synthesis gas 

 (Wiseman 1972). The process was used by Germany during World War II to 

 produce both liquid fuels and hydrocarbons for chemical syntheses. The reaction 

 uses a cobalt catalyst at high temperatures to give a complex mixture of hydro- 

 carbons. While gasoline can be made from the process, extensive facilities are 

 needed to separate and upgrade the primary reaction products (Kuester 1980). 

 Today the process is uneconomical in most countries, but is used in South 

 Africa. Current active research and development, focused on mechanisms, 

 catalysts, and reaction designs, may revive commercial use of the Fischer- 

 Tropsch process to produce basic hydrocarbons (Haggin 1981). 



Catalysis. — All of the reactions described above are carried out with hetero- 

 geneous catalysis. That is, reactants are gases and liquids which come in contact 

 with a solid catalyst. The reactions occur on the surface and in crevices of the 

 catalyst. Heterogeneous catalysis is advantageous because the catalyst can be 

 separated readily from the product stream resulting from the reaction. 



Heterogeneous catalysis has been the backbone of the petrochemical industry. 

 Recently, homogeneous catalysis (both reactants and catalyst are in solution) 

 by use of metal cluster compounds has been demonstrated for several reactions. 

 Of interest to the utilization of synthesis gas is the reduction of carbon monox- 

 ide. Ethylene glycol, an important industrial chemical, can be produced in high 

 yield from the reaction of synthesis gas with a rodium complex. 



H2 + rn complex ^ unru.ru.nu (78%) + other alcohols (22%) 



(26-18) 



Under certain conditions methanol can also be produced by this approach. While 

 these homogeneously catalyzed reactions will undoubtedly be employed in the 

 future, they are not yet commercially feasible (Anderson 1980; Wender 1980). 

 Readers interested in further study should find useful Garten et al. (n.d.), an 

 assessment and perspective of the application of catalytic technologies to the 

 thermochemical conversion of biomass to gaseous and liquid fuels. For a more 



