Insights into the active sites of chlorine-resistant Pt-based bimetallic catalysts for benzene oxidation

Abstract

Since the Pt-based catalysts often suffer severe deactivation by chlorine, development of a catalyst with good activity and chlorine-resistant ability is of importance in effectively controlling emissions of (chlorinated) volatile organic compounds ((C)VOCs). In this work, we prepared the Al2O3-supported bimetallic catalysts with narrow metal particle size distributions and their application in benzene oxidation. It is found that PtW/Al2O3 showed the highest catalytic activity and the lowest activation energy. The characterization results were well correlated with the catalytic activities, and a Pt–MOx (M = W, Mo) bimetallic synergistic effect was proposed. In situ FTIR studies reveal that the transformation from phenol to benzoquinone was the key step in benzene oxidation process. The influence of 1,2-dichloroethane (DCE) on catalytic activity for benzene oxidation of the as-obtained samples was also examined. It is demonstrated that there was a competitive adsorption between benzene and DCE molecules, and the DCE exerted an inhibitive effect on benzene oxidation. We conclude that excellent catalytic performance of the bimetallic sample was associated with its good abilities to adsorb and activate benzene on small ensembles of the MOx in proximity contact with Pt as well as the strong interaction between the highly dispersed metallic Pt species and the MOx clusters (which led to enhancement in anti-deactivation of the Pt species under the oxygen-rich and Cl-containing reaction conditions). We are sure that the present work can provide an idea for understanding the nature of bimetallic active sites and rationally designing the efficient bimetallic catalysts for the oxidative removal of VOCs.