Fischer−Tropsch Synfuels from Biomass: Maximizing Carbon Efficiency and Hydrocarbon Yield
Abstract
According to various published process studies, efficiencies of biomass-to-liquid conversion may be expected in the range of 30−50% for chemical energy and 25−45% for carbon recovered in hydrocarbon products. Strategies for improving carbon conversion efficiency include minimizing O2 consumption in gasification and increasing synthesis selectivities and CO2 conversion during synthesis with hydrogen added from external sources. CO2 conversion during Fischer−Tropsch (FT) synthesis is possible with a CO/CO2 shift-active catalyst, if sufficient H2 is available. A combined experimental and modeling study has shown that equilibrium and kinetic limitations involved can be decreased by means of a membrane, which allows for in situ removal of H2O from the catalyst bed. The results help to quantify the effects of H2O permeability, permselectivities, and reaction conditions and help to indicate directions for further membrane development. This paper collects yield and efficiency estimates for FT synfuel production from biomass feedstocks. Limiting factors for the heating value output are discussed, and a conceptual/experimental study is presented that addresses in situ H2O removal by a hydrophilic membrane, aiming at maximizing carbon efficiency.