Evolution of VO on TiO-ZSM-5 Composite Supports upon K Poisoning and Its Effects on Ultralow Temperature NH-SCR.

Compared with VO/TiO, vanadia catalysts supported on TiO-ZSM-5 composite support possess excellent resistance to potassium poisoning in the selective catalytic reduction of NO by NH (NH-SCR). Appropriate addition of ZSM-5 (10 wt %) enhances the low-temperature activity of NH-SCR with more than 80% NO conversion at 175-450 °C, as the combination of TiO and ZSM-5 is conducive to the formation of more low-valent (polymeric) VO preferentially deposited on TiO. Compared with VO/TiO, the composite support catalysts effectively shield VO as the main active species from K poisoning by preferential ion-exchange of K with Brønsted acid sites (Si-O(H)-Al) of ZSM-5.