Effect of Fe/Mn Ratio on the Catalytic Oxidation of Toluene over Porous -Al₂O₃ Supported Fe and Mn Bimetal Catalysts

Reflux-coprecipitation method is used to synthesize porous gamma-Al2O3 supported Fe and Mn bimetal catalysts, and then the as-obtained porous FexMny/Al2O3 with different Fe/Mn ratio are measured by BET, XRD, SEM, TEM, XPS, and H-2-TPR. Meanwhile, effects of Fe/Mn ratio on the adsorption and catalytic oxidation properties of toluene by the as-obtained porous FexMny/Al2O3 are experimentally studied in a micro fixed-bed reactor, and then the structure-activity relationship of the porous FexMny/Al2O3 catalysts for toluene removal are obtained. Finally, the adsorption and oxidation mechanism of toluene over these porous FexMny/Al2O3 is proposed based on the in-situ FTIR analysis. Results indicate the Fe/Mn ratio has a significantly influence on the toluene oxidation activity of the porous FexMny/Al2O3 catalysts, among which porous Fe1Mn2/gamma-Al2O3 exhibits the highest toluene conversion with T-90 of 238 degrees C as well as the lowest activation energy of 32.68 kJ/mol under WHSV of 80,000 mL/g(/)h. However, the porous Fe1Mn2/gamma-Al2O3 with different Fe/Mn ratios exhibit similar toluene adsorption capacities, and the Bangham model is well fitted with toluene adsorption over all these porous FexMny/Al2O3. In situ FTIR results reveal that adsorbed oxygen and lattice oxygen simultaneously react with the adsorbed toluene, which results in promoting the oxidation of methyl in toluene and facilitating the breakage of aromatic C = C to form CO2.