Abstract: A mechanochemical redox reaction between KMnO₄ and CoCl₂ was developed to obtain a Co_xMn_1-xO_y 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 Co_xMn_1-xO_y catalyst exhibited better activity (T₁₀₀ for propylene= ~200 ℃) than the control catalysts obtained using the SG (325 ℃) or CP (450 ℃) 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 Co_xMn_1-xO_y catalyst worked well in the presence of water vapor (H₂O 4.2%, >60 h) or SO₂ (100 ppm) and at high temperature (400 ℃, >60 h). The structure MnO₂·(CoOOH)_2.93 was suggested for the current Co_xMn_1-xO_y catalyst. This catalyst could be extended to the total oxidation of other typical hydrocarbons (T₉₀=150 ℃ for ethanol, T₉₀ =225 ℃ for acetone, T₉₀=250 ℃ for toluene, T₉₀ =120 ℃ for CO, and T₉₀=540 ℃ for CH₄). Scale-up of the synthesis of Co_xMn_1-xO_y catalyst (1 kg) can be achieved via ball milling, which may provide a potential strategy for real world catalysis.

Key words: Mechanochemical synthesis, Solid-state synthesis, Porous metal oxide, Co_xMn_1-xO_y catalyst, Hydrocarbon combustion