Achieving deep oxidation of toluene over CoMnOx catalyst: Insight into the collaboration of Co3O4 and MnOx via layered double hydroxides (LDHs) precursor template

CoMn-based metal oxides have been widely concerned for the total oxidation of volatile organic compounds due to their excellent redox capacity. The suitable molar ratio and calcination temperature in the hydrotalc-like precursor method can significantly affect the CoMn valence distribution and thus affect toluene catalysis. In this paper, CoMnAl-LDO (Layered double oxide) is synthesized via hydrotalc-like precursor method and the toluene oxidation performance is evaluated. Results show that larger specific surface area and higher oxygen mobility of as prepared sample make great contribution to the superior oxidation performance. More importantly, the existence of rich valence of Mn4+ and Co3+ can extremely break the CC of aromatic, and the formation of critical intermediate carbonates is easy, which can account for the enhanced low temperature activity and H2O resistance of the catalyst. Compared with the CoMn mixed metal oxides (Co3O4/MnO2, Co3O4/Mn2O3, Co3O4/Mn3O4) prepared with mechanical mixing method, Co1.5Mn1.5Al-500 achieves the best toluene conversion performance (T90 = 240 °C). In situ DRIFTS shows the reaction abides the Mars-van Krevelen (MVK) mechanism. This research expands the application to fabricate LDHs catalyst in the field of toluene oxidation and provides a novel reference for the design of CoMn-based bimetallic oxide catalysts.