(118b) Conversion of Synthesis Gas into Ethanol Using Homogeneous Catalysts

Before production of fuel ethanol became dominated by fermentation routes, many of the large oil and chemical companies utilized synthesis gas produced from natural gas and patented methods for conversion of H₂ + CO into ethanol using homogeneous catalysis. They often employed metals long used in Fischer-Tropsch synthesis, because of the ability of these metals to catalyze CO-transfer and CO-insertion reactions.  By a judicious choice of ligands and reactor residence time, chain lengths of the Fischer-Tropsch products could be limited to the lower molecular-weight alcohols. Ongoing work at TDA Research, Inc. demonstrates that a wide variety of transition-metal oxides are reduced by the H₂ + CO of high-pressure synthesis gas into carbonyl anions and anionic metal-carbonyl hydrides that remain stable at ambient pressure and temperature. In general, the TDA carbonyl anions catalyze CO-transfer reactions; hydrides transfer hydrogen for reduction reactions, and carbonyl hydrides transfer both CO and hydrogen. Rate to ethanol exceeds 0.26 g ethanol/g metal catalyst/h, which on a metals basis, is equivalent to the best heterogeneous catalysts reported, but with the homogeneous system showing much higher selectivity, especially in minimizing low-value CH₄.

Acknowledgement: U.S. Department of Energy, Office of Science, Grant Award: DE-SC0004376.