Impact of NOx and NH3 addition on toluene oxidation over MnOx-CeO2 catalyst

An increasing number of industries remove toluene from flue gas by the existing NH3-selective catalytic reduction (NH3-SCR) units. A thorough probe into the impact of NOx and NH3 addition on toluene oxidation is imperative but still lacks a unified understanding. In this work, NH3-SCR reactants are found to inhibit the toluene oxidation process over the MnOx-CeO2 catalyst below 200 °C. The competitive adsorption between NH3-SCR reactants and toluene, the NO2 adsorption state, and carbon deposition are emphasized to play important roles in this deactivation. Within the NO2 adsorption states, only the adsorbed NO2 can enhance the toluene oxidation. The formed nitrate species (NO3-) on the surface is inactive. NO2 adsorption is the weakest among the reactants with the smallest adsorption energy of −0.42 eV, restricting its promotion on toluene oxidation. NO and N2O are both demonstrated to be inefficient to oxidize toluene. Meanwhile, MnOx-CeO2 catalyst suffers from serious acetonitrile and benzonitrile poisoning. The amount of nitrile species accounts for ~95% of total carbon deposition, while no simple substance carbon (C) can be generated from CO disproportionation. Special care should be considered towards the formation of environmentally hazardous benzamide in the off-gas from the simultaneous NOx and toluene removal process.