(6ds) Liquid Fuel Production Via the Integration of Glycerol Processing Over C-Supported Pt-Re Catalysts with Fischer-Tropsch Synthesis
We have studied the direct production of liquid alkanes from glycerol via an integrated process involving catalytic conversion of concentrated glycerol solutions to H2/CO gas mixtures (synthesis gas) with subsequent Fischer-Tropsch synthesis. We show that the addition of Re to C-supported Pt-based catalysts increases the rate of synthesis gas production by a factor of 5 compared to Pt/C at conversions lower than 20% and with a H2 co-feed. However, Pt-Re/C is an order of magnitude more active than Pt/C at conditions leading to higher CO pressures (greater than 20% conversion and without H2 co-feed), suggesting that the primary promotional effect of Re is to weaken the interaction of CO with the surface, thereby decreasing the CO coverage and allowing the catalyst to operate at high rates in the presence of gaseous CO. Temperature-programmed reduction, CO and H2 chemisorption, and X-ray diffraction studies indicate the formation of a Pt-Re alloy. Importantly, we show that this Pt-Re/C catalyst produces synthesis gas at high rates and selectivities suitable for Fischer-Tropsch synthesis (H2/CO 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). The oxygenated hydrocarbon byproducts from glycerol conversion do not significantly inhibit Fischer-Tropsch synthesis, and in some cases, have a synergistic effect of participating in hydrocarbon chain growth. 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 in the chemical industry or recycled for conversion to gaseous products.