Effect of Fe/Mn Ratio on the Catalytic Oxidation of Toluene over Porous γ-Al 2 O 3 Supported Fe and Mn Bimetal Catalysts

Reflux-coprecipitation method is used to synthesize porous γ-Al 2 O 3 supported Fe and Mn bimetal catalysts, and then the as-obtained porous Fe x Mn y /Al 2 O 3 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 Fe x Mn y /Al 2 O 3 are experimentally studied in a micro fixed-bed reactor, and then the structure–activity relationship of the porous Fe x Mn y /Al 2 O 3 catalysts for toluene removal are obtained. Finally, the adsorption and oxidation mechanism of toluene over these porous Fe x Mn y /Al 2 O 3 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 Fe x Mn y /Al 2 O 3 catalysts, among which porous Fe 1 Mn 2 /γ-Al 2 O 3 exhibits the highest toluene conversion with T 90 of 238 °C as well as the lowest activation energy of 32.68 kJ/mol under WHSV of 80,000 mL/g / h. However, the porous Fe 1 Mn 2 /γ-Al 2 O 3 with different Fe/Mn ratios exhibit similar toluene adsorption capacities, and the Bangham model is well fitted with toluene adsorption over all these porous Fe x Mn y /Al 2 O 3 . 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 CO 2 . Graphical Abstract