Mechanistic Insights into Potassium Poisoning of V ₂ O ₅ –MoO ₃ /TiO ₂ Catalysts in the Synergistic Catalytic Control of NO x and Chlorinated Organics

Vanadium-based catalysts are widely considered for the synergistic removal of NO x and chlorinated organics in waste incineration and sintering flue gases, where alkali metals can accumulate and compromise catalytic stability and emission safety. Herein, experiments and DFT calculations were combined to elucidate the effect of potassium on the multipollutant conversion efficiency, synergistic reaction mechanism, and toxic byproduct formation over a V 2 O 5 –MoO 3 /TiO 2 catalyst. Potassium species preferentially neutralized Brønsted acid sites and reduced the availability of surface hydroxyl groups, thereby weakening NH 3 activation and chlorinated organic adsorption/activation. DFT calculations further revealed that K 2 O adsorption at the V–Mo interfacial site hindered interfacial electron transfer and lattice oxygen activation, suppressing Mars-van Krevelen deep oxidation. Consequently, potassium deposition decreased NO x conversion and chlorinated organic oxidation by 20% and 90% at 350 °C compared to V 2 O 5 –MoO 3 /TiO 2, respectively, and promoted the formation of incomplete oxidation products, including chloromethane and benzaldehyde. Our findings demonstrate that alkali poisoning not only lowers catalytic activity but also redirects reaction pathways toward secondary byproduct formation, highlighting the need to design alkali-tolerant catalysts that preserve acid-redox coupling under alkali-rich flue-gas conditions.