The effect of synergy between Cr2O3-CeO2 and USY zeolite on the catalytic performance and durability of chromium and cerium modified USY catalysts for decomposition of chlorinated volatile organic compounds

Abstract

The chromium and cerium modified USY zeolite catalysts (Cr2O3-CeO2-USY) were prepared by impregnation method and investigated in terms of catalytic decomposition of dichloromethane (DCM), trichloroethylene (TCE) and 1,2-dichloroethane (DCE). The results show that there are two types of active sites in the catalysts. The acidic site is the active center for dehydrochlorination of CVOCs, and the metallic xoide is the center providing active oxygen species for CVOCs deeper oxidation. The interaction between Cr2O3 and CeO2 species optimizes the concentration ratio of strong acid sites to weak acid sites and improves the mobility of oxygen species over Cr2O3-CeO2-USY catalysts, which is beneficial to the dehydrochlorination and deeper oxidation of chlorinated volatile organic compounds (CVOCs), respectively. Cr2O3-CeO2-USY catalyst with 17.5wt.% loading of Cr2O3 (17.5Cr2O3-12.5CeO2-USY) presents better catalytic performance for CVOCs decomposition along with higher selectivity to HCl and CO2 formation, which can be due to the higher percentage of strong acidity, more accessible oxygen species, and the stronger synergy between Cr2O3-CeO2 and USY zeolite. In addition, the stronger interaction between Cr2O3 and CeO2, along with the synergy between Cr2O3-CeO2 and USY zeolite over 17.5Cr2O3-12.5CeO2-USY results in less coke deposit, slight HCl attack on the catalysts and improved resistance to chlorination of active components. Therefore, 17.5Cr2O3-12.5CeO2-USY shows the better durability and structure stability during the long term exposure to DCE.