Oxidative dehydrogenation of propane over Pt-Sn/Si-beta catalysts: key role of Pt-Sn interaction

摘要

Bimetallic Pt-Sn catalysts supported on dealuminated Si-beta zeolite were prepared via wet impregnation and the nanoscale close contact between Pt and Sn species in Pt-Sn/Si-beta was confirmed by electron microscopy analyses. Characterization results from temperature-programmed reduction by hydrogen (H-2-TPR) and X-ray photoelectron spectroscopy (XPS) indicated the interaction between Pt and Sn species, and the electron transfer from SnO2 to Pt species was clearly demonstrated by the XPS and FTIR spectra of CO adsorption. The as-prepared bimetallic Pt-Sn/Si-beta catalyst exhibited remarkable performance in the oxidative dehydrogenation of propane (ODHP), in great contrast to monometallic Pt/Si-beta and Sn/Si-beta. Typically, a stable propane conversion of 37% and a propylene selectivity of 75% could be simultaneously achieved on 0.5Pt-5Sn/Si-beta at a reaction temperature of 773 K. Temperature-programmed desorption experiments revealed that the propane adsorption significantly strengthened while the propylene adsorption weakened on the bimetallic Pt-Sn/Si-beta catalyst, which accordingly resulted in its remarkable performance in ODHP reaction. The spatial separation of Pt and Sn species was observed on the used Pt-Sn/Si-beta catalyst and it was responsible for the catalytic deactivation.