Characteristics and catalytic properties of Pt-Sn/Al2O3 nanoparticles synthesized by one-step flame spray pyrolysis in the dehydrogenation of propane

The Pt-Sn/Al2O3 catalysts with 0.3 wt% Pt and 0.5-1.5 wt% Sn loading were prepared by one-step flame spray pyrolysis (FSP). Unlike the catalysts prepared by conventional impregnation method, the FSP-derived catalysts were composed of single-crystal line gamma-alumina particles with the as-prepared primary particle size of 10-18 nm and contained only large pores. The FSP catalysts exhibited superior catalytic activity and better stability than the ones made by impregnation in the dehydrogenation of propane, while they did not alter the selectivity to propylene (in all cases, propylene selectivity >= 96%). The presence of large pores in the flame-made catalysts not only facilitated diffusion of the reactants and products but could also lessen the amount of carbon deposited during reactions. As revealed by CO chemisorption, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), the metal particles appeared to be partially covered by the alumina matrix (Al-O) due to the simultaneous formation of particles during FSP synthesis. Such phenomena, however, were shown to result in the formation of active Pt-Sn ensembles for propane dehydrogenation as shown by higher turnover frequencies (TOFs). (C) 2009 Published by Elsevier B.V.