(73a) Production of Liquid Fuels Via Catalytic Glycerol Processing Coupled with Fischer-Tropsch Synthesis
We have studied the direct conversion of glycerol to liquid alkanes via an integrated process involving catalytic conversion of concentrated glycerol solutions to H2/CO gas mixtures (synthesis gas) combined with subsequent Fischer-Tropsch synthesis in the same reactor. We show that the addition of Re to C-supported Pt-based catalysts increases the rate of synthesis gas production by an order of magnitude at conditions leading to higher CO pressures. Also, we show that this Pt-Re/C catalyst produces synthesis gas at high rates and selectivities suitable for Fischer-Tropsch synthesis (H2/CO ratios between 1.0 and 1.6) from concentrated glycerol feed solutions (between 50 wt% and 80 wt%) at low temperatures (548 K) and high pressures (5-17 bar). Importantly, the water and oxygenated hydrocarbon byproducts from glycerol conversion either have negligible effects on the subsequent Fischer-Tropsch synthesis (e.g., water, acetone, and ethanol) or have synergistic effects by participating in hydrocarbon chain growth (e.g., acetol). Finally, we show that liquid hydrocarbons can be produced from glycerol in a two-bed, single reactor system at 548 K and pressures between 5 and 17 bar. The hydrocarbon products have a selectivity to C5+ alkanes of 75% at 17 bar, and the aqueous liquid effluent contains between 5 wt% and 15 wt% methanol, ethanol, and acetone, which can be separated from the water via distillation and used as chemicals or recycled for conversion to gaseous products. This integrated process has the potential for improving the economics of liquid fuel production from biomass via Fischer-Tropsch synthesis.