Fabrication of homogeneous and highly dispersed CoMn catalysts for outstanding low temperature catalytic oxidation performance

Abstract

A series of homogeneous and highly dispersed CoMnO_x bimetallic oxides with different ratios were prepared through pyrolysis of CoMn-MOF-71, which was applied to the catalytic oxidation of toluene. Notably, the effect of Co/Mn molar ratio on the catalytic activity of toluene oxidation was systematically investigated. After calcination, the samples consisted of many uniformly distributed nanoparticles, which could be seen from the TEM images. In particular, the Co₁Mn₁O_x alloy catalyst exhibited superior low temperature catalytic oxidation performance. The complete conversion temperature of toluene (T₁₀₀) was 180 °C, which is a relatively low temperature in the field of toluene oxidation. Through a series of characterizations, it was concluded that the different molar ratios of cobalt and manganese could obviously change the surface atomic ratio of Co³⁺/Co²⁺ and (Mn⁴⁺ + Mn³⁺)/Mnⁿ⁺. Simultaneously, we discovered that an appropriate amount of manganese improved the catalytic performance with an increase in the surface atomic ratio of (Mn⁴⁺ + Mn³⁺)/Mnⁿ⁺. In addition, lots of surface chemically adsorbed oxygen would speed up the catalytic oxidation of toluene. Furthermore, no significant decrease in the catalytic performance was observed over 14 h on the Co₁Mn₁O_x sample, which indicated that it exhibited excellent stability for toluene oxidation. Therefore, it showed potential as a metal-oxide catalyst in the elimination of toluene.