Influence of MnO2 crystal existing form on its catalytic performance for toluene oxidation

Abstract

A series of MnO2 catalysts with different crystal forms were synthesized by in situ self-doping of Mn induced by bridging interaction between Mn and carboxyl group under moderate medium, and applied to catalytic oxidation of toluene. XRD, SEM and TEM results show that the physical structure of the prepared catalyst is extremely sensitive to the ratio of Mn/CA. Only MnCA-4 catalyst has a special morphology with double crystal and a uniform mixture of rod-like and spherical structures, and some of them are hollow rod-like structures. Due to the interaction between different phase structures, the mixed MnCA-4 catalyst with dual crystal has the best catalytic performance of toluene oxidation, which can oxidize 90 % toluene at 228 °C. The characterization of H2-TPR, O2-TPD, and XPS proved that the strong interaction between different crystalline forms of manganese oxide led to the generation of more oxygen vacancies and Mn3+ species. In situ DRIFTS results show thatMnCA-4 catalyst has stronger ability to adsorb and activate toluene compared with MnCA-12 catalyst, which may be the main reason for its excellent catalytic oxidation performance of toluene. This study provides an effective strategy for designing high efficiency non-noble metal catalysts to construct interface engineering of different crystal types.