(478b) Effective Limits of CO2 and Methane Recycle to Mixed Alcohol Reactors Operated with Metal Sulfide Catalysts

When producing liquid fuels from biomass-derived syngas, process integration and selection of operating conditions are critical factors in determining the economic viability of a plant. This is because biomass to liquids (BTL) plants must be small to assure day-to-day and year-to-year availability of feedstock. As such, unit operations that clean and treat syngas do not benefit from economies of scale as do larger plants, and the quality of gas used for gas to liquids (GTL) reactions may need to be reduced and/or gas may need to be recycled to the GTL reactor without retreatment to achieve an economic BTL plant design. This work explores some of the effects of syngas recycle to a mixed alcohol reactor using a promoted molybdenum sulfide catalyst. Specifically, the effects of methane and carbon dioxide buildup are explored and limits on the concentrations of these species are suggested. Additionally, the advantages and disadvantages of recycling methanol directly to the reactor are discussed, and alternative methods of catalyst sulfiding are suggested.