Enhanced catalytic performance for VOCs oxidation on the CoAlO oxides by KMnO4 doped on facile synthesis

Abstract

The MnOx was immobilized on the CoAl mixed oxides (CoAlO) derived from hydrotalcites with various anions (CO32−, Cl−, NO3− and SO42−) using the hydration and impregnation methods. The CoAlO oxides modified by KMnO4 were calcined in air at 300 °C to obtain stable oxides, which could be used as catalysts for VOCs (acetone and ethyl acetate) oxidation. CoAlO with CO32− and 30 h of hydration time (CoAlO-C-Mn-30) exhibited a promising catalytic activity (T90 = 173 °C for acetone oxidation; T90 = 175 °C for ethyl acetate), highly superior to CoAlO without KMnO4 modification. The improvement in acetone and ethyl acetate catalytic oxidation was ascribed to the Co3+ and surface adsorbed oxygen species. The increase of Co3+ in the CoAlO-C-Mn-30 oxide thanked to the self-decomposition of KMnO4 and reducibility of Co2+ in the CoAlO oxide during the hydration process. This was also confirmed by XRD and XPS characterization, which showed that Mn cations were enriched on the catalyst surface in the valences of +3 and +4. The catalytic activity of the catalyst remained unchanged in four cycles in the presence of 5.5 vol.% water vapor, which indicated a great potential for industrial application.