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

摘要

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-nMnO(x)/meso-CeO2 (m = 0 - 0.39 wt%, n = 0-1.21 wt%) catalysts after calcination at 500 degrees C in air. It is found that the as-obtained catalysts displayed an ordered mesoporous architecture with surface areas of 95-108 m(2)/g. The 0.37Pt- 0.16MnO(x)/meso-CeO2 sample exhibited the best catalytic performance for toluene combustion (T50 % =162 degrees C and T90 % =171 degrees 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- 0.16MnO(x)/meso-CeO2 sample was lower than those (63 - 75 kJ/mol) obtained over the other samples. Furthermore, the 0.37Pt - 0.16MnO(x)/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 - 0.16MnO(x)/meso-CeO2.