Task 4.9 -- Value-added products from syngas

The work on advanced fuel forms in 1996 focused on the synthesis of higher alcohols from mixtures of hydrogen and carbon dioxide (syngas) from coal gasification. The conversion of coal gasification products to commercially valuable alcohols will provide an important new market for current and future gasification plants. Initial work in this project utilized a novel molybdenum sulfide catalyst previously shown to be active for hydrodesulfurization reactions of coal liquids. The support for the active metal sulfide is a layered mixed oxide (hydrotalcite) capable of interaction with the metal sites for catalysis of carbon monoxide reductions. These catalysts have a high surface area, are highly porous, and have basic and acidic functionality. A pressurized fixed-bed flow-through reactor was constructed, and the MoS{sub 2} catalysts were tested with syngas under a variety of conditions. Unfortunately, the catalysts, even with higher molybdenum loading and addition of promoters, failed to give alcohol products. A batch reactor test of the catalyst was also conducted, but did not produce alcohol products. Group 8 metals have been used previously in catalysts for syngas reactions. Ruthenium and rhodium catalysts were prepared by impregnation of a hydrotalcite support. Tests with these catalysts in flow-through reactors also did not produce the desired alcohol products. The formation of higher alcohols from smaller ones, such as methanol and ethanol, could be commercially important if high selectivity could be achieved. The methanol and ethanol would be derived from syngas and fermentation, respectively. Based on previous work in other laboratories, it was hypothesized that the hydrotalcite supported MoS{sub 2} or Ru or Rh catalysts could catalyze the formation of butyl alcohols. Although the desired 1-butanol was obtained in batch reactions with the promoted Ru catalyst, the reaction was not as selective as desired. Product suitable for a lower-vapor-pressure gasoline oxygenate additive was obtained, but it may not be economical to market such products in competition with methyl tertiary-butyl-ether. Flow-through catalytic bed reactions were not successful