Novel Method for Conversion of Biomass to Fuel

The United States needs efficient and cost-effective methods to convert biomass into liquid transportation fuels. Thermochemical gasification of biomass into synthesis gas followed by catalytic conversion into liquid fuels is a promising approach. One particularly attractive liquid fuel is ethanol. However, the thermochemical conversion of biomass into ethanol has been sta lled by lack of a cata lyst that can eff iciently and selectively convert syngas into e thanol. Problems with conventional heterogeneous catalysts include very poor selectivity and the production of undesired sideproductsespecially methane. To overcome shortcomings of solid heterogeneous catalysts for direct conversion of synthesis gas into ethanol, in Phase I we developed a homogeneous catalyst dissolved in an ionic liquid that plays a part in stabilizing the catalyst, controlling selectivity, and providing temperature control. The Phase II project will optimize the homogeneous catalytic process for economic scale-up, enabling the use of biomass-derived synthesis gas for the large-scale production of fuel ethanol. Synthesis gas was converted into ethanol while minimizing production of undesired side productsespecially methane, by utilizing homogeneous catalysts of nonvolatile, inorganic metal anions dissolved and stabilized in a highly thermally conductive, nonvolatile, ionic liquid. The homogeneous system also catalyzed the water-gas shift reaction, chemically consuming water co-produced with the ethanol, allowing energy-efficient separation of the ethanol from the ionic liquid while simultaneously producing hydrogen and allowing use of syngas with a CO/hydrogen molecular ratio of 1/1 or less, compatible with compositions derived from biomass gasifiers. A preliminary techno-economic analysis was performed for a 110 million gallon/year ethanol plant, showing that the optimized process would be competitive with or superior to other means of ethanol production. The homogeneous catalytic process will be refined with modeling, catalyst optimization and testing. Process and economic analysis for scale-up will be done in collaboration with our Phase II partners, including a major ethanol producer that would adopt the technology if the experimental results and process analysis meet industry benchmarks. Commercial Applications or other Benefits: The existing market for fuel ethanol is enormous, with annual U.S. consumption of 13.1 billion gallons, and is expected to grow to 36 billion gallons by 2022.