(492b) Catalytic Hydrothermal Decarboxylation of Unsaturated Fatty Acids with Ptsnx/C

Pt/C is an effective hydrothermal catalyst for decarboxylating saturated fatty acids without added hydrogen, but it has shown low selectivity and activity for decarboxylating unsaturated fatty acids – a common oil precursor in biological sources such as soybeans and algae.  We compared three different Sn containing alloys to Pt/C: Pt₃Sn/C, PtSn/C, and PtSn₃/C by performing batch reactions in liquid water at 350 ˚C for two hours with stearic (C18:0), oleic (C18:1), and linoleic (C18:2) acids.  Pt/C gave a 0.70±0.05, 0.16±0.03, and 0.083±0.009 yield of the C₁₇ alkanes, as opposed to the unobserved direct decarboxylation products, for the oleic and linoleic acid feeds. Stearic acid was the major byproduct with the unsaturated feeds.  In contrast, the PtSn_x/C catalysts yielded two to three times higher C₁₇ yield.  Experiments in D₂O showed that the source of hydrogen for saturation of the fatty acids was water.  These results show that PtSn alloys may give better performance in terms of upgrading biologically derived carboxylic acids to liquid fuels.