Intermetallic compound PtMny-derived Pt−MnOx supported on mesoporous CeO2: Highly efficient catalysts for the combustion of toluene

Abstract

Intermetallic compounds are a kind of important materials in heterogeneous catalysis. In this work, we first synthesized the PtMny intermetallic nanocrystals using the polyvinyl pyrrolidone-assisted ethylene glycol reduction method, and then loaded them on the surface of mesoporous CeO2 (meso-CeO2) derived from a KIT-6-templating route, generating the mPt−nMnOx/meso-CeO2 (m = 0−0.39 wt%, n = 0−1.21 wt%) catalysts after calcination at 500 °C in air. It is found that the as-obtained catalysts displayed an ordered mesoporous architecture with surface areas of 95−108 m2/g. The 0.37Pt−0.16MnOx/meso-CeO2 sample exhibited the best catalytic performance for toluene combustion (T50 % =162 °C and T90 % =171 °C at space velocity = 40,000 mL/(g h)). Kinetic analysis reveals that the apparent activation energy (57 kJ/mol) obtained over the best-performing 0.37Pt−0.16MnOx/meso-CeO2 sample was lower than those (63−75 kJ/mol) obtained over the other samples. Furthermore, the 0.37Pt−0.16MnOx/meso-CeO2 sample possessed good thermal stability and water-resistant performance. Benzyl alcohol, benzoic acid, and maleic anhydride were proven to be the main intermediates of toluene combustion, hence, toluene combustion might take place through a sequence of toluene → benzyl alcohol and benzoic acid → maleic anhydride → carbon dioxide and water, which might obey the Eley−Rideal reaction mechanism. It is concluded that loading of Pt and MnOx enhanced the adsorbed oxygen and Mn2+ species concentration and low-temperature reducibility, thus promoting toluene combustion over 0.37Pt−0.16MnOx/meso-CeO2.