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

Toluene 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 (T-50% = 226 degrees C, T-90% = 240 degrees C), with its activation energy (E-a = 104.3 kJ/mol) being lower than that of the support (E-a = 269.8 kJ/mol). This is attributed to a strong metal-support interaction, as evidenced by H-2-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. (c) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.