Modulation mechanism of Mn-O strength in α-MnO2 catalyst for high-efficiency catalytic combustion of propane

Abstract

The cleavage of C-H with high energy impedes the catalytic combustion of propane. Herein, α-MnO2 with modulation of Mn-O strength by changing the calcination temperature was applied in propane catalytic combustion. α-MnO2 calcinated at 350 °C (α-MnO2-350) exhibited superior performance (T20=150 °C, T90= 220 °C) in propane oxidation due to the synergistic effect of oxygen vacancies (OVs) and Lewis acidity. Density functional theory (DFT) calculations revealed that the lowest o-vacancy formation energy on α-MnO2-350 (Evo=0.74 eV) with its lowest Mn-O strength prompted the existence of abundant OVs and propane oxidation. Moreover, the highest Lewis acidity in α-MnO2-350 displayed the strongest propane adsorption, promoting the activation of C-H. The mineralization of propane on α-MnO2-350 dropped steeply after 68 h while could recover to 90 % in long-term water vapor stability test owing to the H2O adsorbed at OVs and the carbonaceous intermediates adsorbed at the Lewis acid sites.