Structural Effect of Cu-Mn/Al2O3 Catalysts on Enhancing Toluene Combustion Performance: Molecular Structure of Polyols and Hydrothermal Treatment

This study presents a series of Cu-Mn/Al2O3 catalysts prepared by the polyol method to improve the toluene combustion process. The catalytic activity evaluation results showed that the different polyols have a great influence on catalyst activity, in which the catalyst prepared with glycerol through a hydrothermal reaction at 90 °C displayed the highest catalytic activity. The lowest T90 and T50 values could be achieved by CMA-GL-90 with 260 and 237 °C, respectively. Moreover, the XRD and BET results showed that the hydrothermal treatment was more favorable with Cu-Mn crystal formation, and an abundance of mesopores remained in all catalysts with a high specific surface area from 94.37 to 123.03 m2·g−1. The morphology analysis results by SEM and TEM indicated that employing glycerol coupled with hydrothermal treatment at 90 °C could enhance the formation of CuMn2O4 spinel. The toluene catalytic combustion mechanism of Cu-Mn/Al2O3 catalysts was discussed based on XPS and H2-TPR, and a high atomic ratio of Mn3+ could be obtained with 51.03%, and the ratio of Oads/Olatt also increased to 2.85 in CMA-GL-90. The increase in Mn3+ species and oxygen vacancies on the surface of catalysts exhibited excellent activity and stability for toluene combustion. These findings offer valuable insights for optimizing the design and application of Cu-Mn/Al2O3 catalysts in addressing the catalytic oxidation reactions of organic volatile compounds.