Ozone catalytic oxidation of benzene over AgMn/HZSM-5 catalysts at room temperature: Effects of Mn loading and water content

Abstract

The effects of Mn loading and water content on AgMn/HZSM-5 (AgMn/HZ) catalysts were investigated in the ozone catalytic oxidation (OZCO) of benzene in a continuous air flow at room temperature. The catalytic activity is closely related to the Mn loading, and the AgMn/HZ catalyst with 2.4 wt% Mn (AgMn/HZ(2.4)) had the highest activity and stability in benzene oxidation as a result of its large surface area and high MnOx dispersion. Temperature-programmed desorption of the used catalysts demonstrated that 2.4 wt% was also the optimal Mn loading for suppressing the accumulation of benzene and HCOOH over the catalyst surface after benzene oxidation. For AgMn/HZ catalysts with Mn loadings ≤ 2.4 wt%, O3 decomposition to active oxygen species (O*) plays the most important role in benzene oxidation; however, benzene activation is the crucial step for benzene oxidation by O3 over AgMn/HZ catalysts with Mn loadings > 2.4 wt%. The AgMn/HZ(2.4) catalyst was then used to perform OZCO of benzene in a humid stream. Compared with dry gas, water vapor greatly enhanced the activity and stability of the AgMn/HZ(2.4) catalyst, and 0.1–0.2 vol% was the optimal water content for benzene oxidation.