Unveiling Geometric and Electronic Effects of Pt Species on Water-Tolerant Pt/Zsm-5 Catalyst for Propane Oxidation

Abstract

The geometric and electronic effects of Pt species on Pt/ZSM-5 catalyst water-tolerance have been investigated for propane oxidation by controlling the Si/Al ratio of ZSM-5. Under wet condition (5% H2O), it is found that Pt/ZSM-5(18) catalyst contains both irreversible and reversible deactivation Pt active sites; Pt/ZSM-5(130) and Pt/ZSM-5(500) catalysts have only reversible deactivation Pt active sites; all the Pt active sites in the Pt/ZSM-5(1200) catalyst are water tolerant. It is further found that the Si/Al ratio of ZSM-5 significantly affects the geometrical and electronic states of Pt particles, and surface acid sites of catalysts, thereby leading to the different catalytic behaviors of Pt/ZSM-5 catalysts toward water tolerance. Low Si/Al ratio of ZSM-5 benefits to anchor the Pt species and form small Pt particles, but Pt species with small particles and more partially oxidized Pt species (Ptδ+) in Pt/ZSM-5 are seriously poisoned by H2O, therefore giving inferior water tolerance.

Keywords: Pt/ZSM-5 catalyst, Propane oxidation, Water tolerance, Pt active sites, Si/Al ratio