Search

Hierarchical Co 3 O 4 @MnOx material has been synthesized by in-suit growth of MnOx on the Co 3 O 4 and applied in catalytic oxidation of volatile organic compounds (VOCs). Results revealed that T 90 of acetone on the Co 3 O 4 @MnOx was 195 °C, which was 36 °C and 32 °C lower than that on the Co 3 O 4 and MnOx/Co 3 O 4 , respectively. The universality experiments demonstrated that T 90 of ethyl acetate and toluene on the Co 3 O 4 @MnOx were 200 °C and 222 °C, respectively. The above results indicated that Co 3 O 4 @MnOx catalyst presented a robust catalytic performance. Characterization results showed that high catalytic activity of the Co 3 O 4 @MnOx catalyst could be attributed to the improvement of low temperature reducibility, the enhancement of Co 3+ and adsorbed oxygen species resulted from the sufficient reaction between MnO 4 - and Co 2+ during secondary hydrothermal process. Furthermore, stability and water-resistance experiments showed the Co 3 O 4 @MnOx catalyst with high cycle and long-term stability, satisfied endurability to 5.5-10 vol. % water vapor at 210 °C., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The MnO x was immobilized on the CoAl mixed oxides (CoAlO) derived from hydrotalcites with various anions (CO 3 2- , Cl - , NO 3 - and SO 4 2- ) using the hydration and impregnation methods. The CoAlO oxides modified by KMnO 4 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 CO 3 2- and 30 h of hydration time (CoAlO-C-Mn-30) exhibited a promising catalytic activity (T 90  = 173 °C for acetone oxidation; T 90  = 175 °C for ethyl acetate), highly superior to CoAlO without KMnO 4 modification. The improvement in acetone and ethyl acetate catalytic oxidation was ascribed to the Co 3+ and surface adsorbed oxygen species. The increase of Co 3+ in the CoAlO-C-Mn-30 oxide thanked to the self-decomposition of KMnO 4 and reducibility of Co 2+ 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., (Copyright © 2018 Elsevier Ltd. All rights reserved.)