New insights into the deactivation mechanism of V(2)O(5)-WO(3)/TiO(2) catalyst during selective catalytic reduction of NO with NH(3): synergies between arsenic and potassium species

Synergies between arsenic (As) and potassium (K) species in the deactivation of V(2)O(5)-WO(3)/TiO(2) catalyst were investigated. Both arsenic oxide and potassium species presented a serious poisoning impact on catalyst activities, and the extent of poisoning of (As + K) was much stronger than their single superposition. The intrinsic reasons were explored and analyzed by N(2) physisorption, XPS, H(2)-TPR, NH(3)-TPD, NH(3)-DRIFTS and in situ FTIR. Results indicated that BET surface area decreased due to the formation of a dense arsenic coating on the catalyst surface. V–OH active sites were destroyed by arsenic and As–OH acid sites were newly generated. After potassium species were added to arsenic-poisoned catalyst, K(+) further neutralized the As–OH acid sites, and the amount and stability of both Lewis and BrØnsted acid sites decreased more greatly. Potassium also reacted with intermediate NH(2)(−) when the temperature was elevated to higher than 250 °C, which resulted in more NH(3) consumption and NH(3)-SCR reaction inhibition. The extent of deactivation was related to the potassium species when both poisons reacted on the catalyst, and the influence sequence followed AsKS < AsKN < AsKC. As(2)O(3) + K(2)SO(4) presented the weakest impact among these three poisoned catalysts due to the resistance of SO(4)(2−) to arsenic.