Low-temperature toluene oxidation on Ag/CexZr1-xO2 monolithic catalysts: Synergistic catalysis of silver and ceria-zirconia

摘要

? 2022 The Combustion InstituteToluene is one of the main volatile organic compounds (VOCs) from industrial emissions, its control through catalytic combustion becomes more imperative to meet the stringent regulations. In this study, a series of Ag/CexZr1-xO2 monolithic catalysts with different Ce/Zr ratios were prepared to investigate catalytic performance of Ag-loaded catalysts for toluene oxidation. The results show that Ag/Ce0.5Zr0.5O2 catalyst with the optimal Ce/Zr ratio of 1:1 exhibits the highest catalytic performance (T50% = 226 °C, T90% = 240 °C), with its activation energy (Ea = 104.3 kJ/mol) being lower than that of the support (Ea = 269.8 kJ/mol). This is attributed to a strong metal-support interaction, as evidenced by H2-TPR, Raman, XPS and HRTEM, which reveal an apparent enhancement on redox ability and oxygen vacancy formation. In situ DRIFT spectra indicate a fast formation of benzaldehyde, benzoate and maleiz anhydride as key intermediates from toluene oxidation over Ag-loaded catalyst. Besides, XPS and kinetic analyses indicate that toluene oxidation paths over CeZrO2 and Ag/CeZrO2 mainly follow MvK and L-H mechanisms, respectively. This work would provide an important understanding of Ag-CeZrO2 synergistic catalysis on the monolithic catalyst as a potential industrial model.