Insights into the superior performance of mesoporous MOFs-derived Cu[sbnd]Mn oxides for toluene total catalytic oxidation

Abstract

A novel approach is developed to synthesize a series of flower like CuMn oxides catalysts for toluene removal with high efficiency. The optimal catalyst (i.e., 1Cu1Mn-450 prepared by calcination of Cu1Mn1-ptcda MOFs with Cu/Mn molar ratio of 1:1 by 450 °C) maintains 100% toluene removal for 54 h in the presence of steam (5.0 Vol%) at 210 °C. Besides, 1Cu1Mn-450 displays superior catalytic activity at high WHSV and high toluene concentrations. The relationships between textural, structural, and toluene catalytic performance are analyzed by various characterization techniques. Due to strong low-temperature reducibility, mobility of active oxygen, high average oxidation states (AOS) of Mn, mobility of active oxygen, as well as oxygen storage capacity at low temperatures, 1Cu1Mn-450 exhibits excellent activity and stability of toluene oxidation. The toluene oxidation was in the following pathway of toluene → alkoxide → benzoate → phenolate → maleic anhydride → short-chain carboxylates → CO2 and H2O. The breakage of CO in benzoate or CC in benzene ring is proved to be the rate-controlled step according to in situ DRIFTS. These findings can provide a feasible method to desigin transition metal oxide catalysts for large-scale industrial applications.