The effect of KCl on the simultaneous removal of NO and toluene on CeO2-TiO2 catalyst: insights from experimental and DFT studies

KCl species released from co-firing of organic solid waste or biomass in coal-fired boilers inevitably jeopardize the removal performance and property of deNO_x and toluene oxidation catalysts. Herein, the effect of KCl on the typical CeO₂/TiO₂ catalyst in the simultaneous deNO_x and toluene oxidation scenario was investigated in this paper. The optimal removal efficiencies of NO_x and toluene for the fresh CeO₂/TiO₂ catalyst were 96.3 % and 96.4 % at 400 °C, whereas after KCl poisoning the removal efficiencies decreased to 57.10 % and 15.5 %, respectively. Through comprehensive characterization techniques and theoretical calculations, the KCl poisoning mechanism was further investigated. The findings revealed that physically, KCl covered the surface active sites, caused particle clustering and affected the TiO₂ lattice. Chemically, KCl reduced the adsorption capacity of ammonia and decreased the surface acidity. Meanwhile, the electron transfer on the catalyst was also inhibited due to KCl bonding with CeO and TiO, hindering the conversion of reactive O/Ce species and inhibiting oxygen vacancy formation. The ratio of active Ce³⁺ was depressed, leading to difficulty in Ce³⁺/Ce⁴⁺ valence cycling. This work solidifies guidance for the development of simultaneous deNO_x and toluene oxidation in rich KCl-containing environments.