Catalytic Oxidation of Chlorobenzene over HSiW/CeO₂ as a Co-Benefit of NO _x Reduction: Remarkable Inhibition of Chlorobenzene Oxidation by NH₃

There is an urgent need to develop novel and high-performance catalysts for chlorinated volatile organic compound oxidation as a co-benefit of NO_x. In this work, HSiW/CeO₂ was used for chlorobenzene (CB) oxidation as a co-benefit of NO_x reduction and the inhibition mechanism of NH₃ was explored. CB oxidation over HSiW/CeO₂ primarily followed the Mars-van-Krevelen mechanism and the Eley-Rideal mechanism, and the CB oxidation rate was influenced by the concentrations of surface adsorbed CB, Ce⁴⁺ ions, lattice oxygen species, gaseous CB, and surface adsorbed oxygen species. NH₃ not only strongly inhibited CB adsorption onto HSiW/CeO₂, but also noticeably decreased the amount of lattice oxygen species; hence, NH₃ had a detrimental effect on the Mars-van-Krevelen mechanism. Meanwhile, NH₃ caused a decrease in the amount of oxygen species adsorbed on HSiW/CeO₂, which hindered the Eley-Rideal mechanism of CB oxidation. Hence, NH₃ significantly hindered CB oxidation over HSiW/CeO₂. This suggests that the removal of NO_x and CB over this catalyst operated more like a two-stage process rather than a synergistic one. Therefore, to achieve simultaneous NO_x and CB removal, it would be more meaningful to focus on improving the performances of HSiW/CeO₂ for NO_x reduction and CB oxidation separately.