Accelerating the Low-Temperature Catalytic Oxidation of Acetone over Al-Substituted Mn–Al Oxides by Rate-Limiting Step Modulation

In order to enhance the catalytic activity and improve the stability of Mn–Al oxides in acetone oxidation, it is interesting to have found that modulating and accelerating the rate-limiting step by Al substitution rather than just mixing of Mn and Al is crucial for hydrocarbon efficient catalytic destruction. Here, a series of Mn–Al oxides with different Al substitution ratios were prepared by a scalable and facile hydrothermal-redox strategy. The reaction rate, selectivity, and stability of the representative α-MnO2 catalyst in acetone oxidation can be remarkably promoted by simple replacing of the partial framework Mn with Al, which changes the rate-limiting step from acetic acid dissociation to ethanol decomposition accelerated by H2O molecules. Among them, MnAl0.5 displays the best catalytic performance with 90% of acetone converted at just 165 °C and a remarkable CO2 yield. DFT results suggest that the py and px orbitals of the O element take part in the formation of the carbonyl group when the intermediate of removing H* from ethanol reacts with the hydroxyl group of H2O. The dxz orbital of Mn with p-electron of Al plays a vital role in the rate-limiting step. The work provides new insights into engineering catalysts for industrial VOC efficient and economical mineralization.