(651e) Pt-Fe Intermetallic Alloy Nanoparticles As Selective Propane Dehydrogenation Catalysts

Bimetallic Pt-Fe catalysts were synthesized with nominal Fe:Pt atomic ratios of 0.7, 2.9, and 4.4 and compared to monometallic Pt and Fe catalysts for propane dehydrogenation at 550 ^oC. The three bimetallic catalysts were greater than 95% selective towards propylene. The Pt catalyst was only 70% selective and the Fe catalyst produced almost exclusively methane. ­In-situ X-ray absorption spectroscopy and X-ray diffraction revealed that Pt and Fe formed intermetallic alloys and that the phase varied with the Fe:Pt ratio. As the atomic ratio was increased, first the Pt₃Fe phase was formed, then PtFe, and lastly PtFe₃. The increase in selectivity is proposed to arise from the elimination of Pt ensembles responsible for hydrogenolysis, the primary competing reaction. Changes in the energy and shape of the XANES of each phase indicate differences in the electronic structure of Pt in each alloy.