Surface modification of PtSn/Al2O3 catalyst by organic acid chelation and its effect on propane dehydrogenation performance

Abstract

A series of Pt-based catalysts has been prepared by a chelating-agent-assisted impregnation method, and characterized by N2 adsorption/desorption, XRD, XPS, H2-TPR, NH3-TPD, pyridine-FTIR, CO-DRIFT-IR, Raman, and TG techniques to investigate the influence of organic acids on physicochemical properties. It was found that, except in the case of tartaric acid, organic acid-assisted preparation not only led to higher dispersion of Pt particles in comparison with organic acid-free catalyst PtSn/Al2O3, but also changed the concentration of Lewis acid sites and modified the interaction between the metallic Pt sites and the support. Experiments on the catalytic dehydrogenation of propane have revealed that the optimal dehydrogenation performance, with a propane conversion of 35% and a propylene selectivity of 93%, was obtained over the citric acid-assisted catalyst (PtSn/Al2O3-CA). Lewis acid sites are mainly responsible for activating C–H bonds during the tandem activation–cleavage process, whereas coke deposition and the aggregation of Pt sites are mainly responsible for deactivation of the catalyst.