Mechanochemical redox-based synthesis of highly porous Co Mn1-O catalysts for total oxidation

A mechanochemical redox reaction between KMnO4 and CoCl2 was developed to obtain a CoxMn1–xOy catalyst with a specific surface area of 479 m2 g−1, which was higher than that obtained using a co-precipitation (CP) method (34 m2 g−1), sol-gel (SG) method (72 m2 g−1), or solution redox process (131 m2 g−1). During catalytic combustion, this CoxMn1–xOy catalyst exhibited better activity (T100 for propylene = ~200 °C) than the control catalysts obtained using the SG (325 °C) or CP (450 °C) methods. The mechanical action, mainly in the form of kinetic energy and frictional heating, may generate a high degree of interstitial porosity, while the redox reaction could contribute to good dispersion of cobalt and manganese species. Moreover, the as-prepared CoxMn1–xOy catalyst worked well in the presence of water vapor (H2O 4.2%, >60 h) or SO2 (100 ppm) and at high temperature (400 °C, > 60 h). The structure MnO2·(CoOOH)2.93 was suggested for the current CoxMn1–xOy catalyst. This catalyst could be extended to the total oxidation of other typical hydrocarbons (T90 = 150 °C for ethanol, T90 = 225 °C for acetone, T90 = 250 °C for toluene, T90 = 120 °C for CO, and T90 = 540 °C for CH4). Scale-up of the synthesis of CoxMn1–xOy catalyst (1 kg) can be achieved via ball milling, which may provide a potential strategy for real world catalysis.