A Promising Monolithic Catalyst for Advanced VOCs Oxidation by Graphene-Doped α-MnO2 Loaded on Cordierite Honeycomb

A high-activity, low-cost, and easy-to-prepare monolithic catalyst is crucial for the industrial catalytic combustion of volatile organic compounds (VOCs) in a cost-effective manner. In this study, a highly efficient monolithic catalyst, designated as 4GM/COR, was developed by loading 4% graphene-doped α-MnO2 (4GM) catalyst onto pre-etched cordierite (COR) blocks using a straightforward “ball-milling-assisted impregnation” method. The anchoring force of the cordierite pores, generated through oxalic acid etching, enables the uniform and robust loading of powdered 4GM onto COR, preventing detachment under high temperatures or high gas flow rates. The loading rate, specific surface area, and concentrations of Mn3+ and surface-lattice and absorbed oxygen species in the monolithic catalyst increase with impregnation times from 2 to 4, indicating that catalytic activity is optimized through repeated impregnation. Catalytic performance tests demonstrated that the 4-4GM/COR exhibited the highest activity, achieving 90% degradation of toluene at 200 °C under both dry and humid (relative humidity is 85%) conditions. Furthermore, the 4-4GM/COR maintains high catalytic stability and activity even at a large GHSV of 6000 h−1. To conclude, the 4-4GM/COR monolithic catalyst developed in this study not only represents a promising option for industrial applications but also serves as an important reference for the synthesis of monolithic catalysts.