Parametric characterization and influence of tin on the performance of Pt-Sn/ SAPO-34 catalyst for selective propane dehydrogenation to propylene

Abstract

The selective propane dehydrogenation to propylene was studied to enhance Pt-Sn/SAPO-34 catalyst performance. The objective was to achieve higher propylene selectivity; therefore, the reaction was parametrically characterized to obtain necessary information to integrate the process operating conditions. The optimum operating conditions were found to be temperature 585 °C, weight hour space velocity 5.6 h-1 or lower, H2/C 3H8 molar ratio 0.25, and conversion range 14-25%. Further intensification and the role of Sn on the performance of Pt-Sn/SAPO-34 catalyst were investigated, as stereochemistry and thermodynamics are inextricably tied up with each other. The catalyst was characterized by a number of physiochemical techniques: X-ray fluorescence, Brunauer-Emmett-Teller surface area measurement, X-ray diffraction, temperature-programmed desorption of NH 3, temperature-programmed reduction of H2, infrared spectra, temperature-programmed oxidation, and O2-pulse coke analysis. The catalytic performance was largely improved with the presence of Sn up to a certain limit; after that, it caused diminution in the reaction rate. The Sn loading modifies surface Pt ensembles; those helped Pt to be well dispersed by changing the interfacial character between the metal and support. Moreover, Sn facilitates the transfer of carbon deposit from the metal sites to the support. In general, it is noted that the increase in Sn content from 1 wt % affects catalyst performance adversely. Higher propylene selectivity (94%) and total olefin selectivity (97.2%) were obtained using [Pt(0.5 wt %) - Sn(1 wt %)]/SAPO-34. © 2010 American Chemical Society.