The improved sulfur resistance derived from the dual protection of Ti species over Cu/SAPO-34 catalysts during NH3-SCR

In this work, Cu/SAPO-34 was prepared by liquid ion exchange, which was further loaded with Ti-species (Cu/ SAPO-34-Ti) via the hydrolysis of tetrabutyl titanate. Most of these Ti-species were presented as TiO2 on the surface of Cu/SAPO-34, giving rise to enhanced acidity, redox property, and enriched chemical oxygen species of the catalysts. DRIFTS experiments evidenced that the SO2-induced Cu/SAPO-34 deactivation (loss of DeNOx activity) originated from the formation of surface ammonium sulfate and the sulfation of ZCuOH. The surface TiO2 species could inhibit the adsorption of SO2 and the SO2-ZCuOH reactions, and while adsorbed more reactant gases to weaken the competitive adsorption. The sulfur-phobicity of TiO2 could inhibit the adsorption and deposition of SO2 on Cu/SAPO-34 surface, and reduce the decomposition temperature of ammonium sulfates. Meanwhile, the surface TiO2 layers also decelerated the SO2-ZCuOH reactions and therefore preserved the reactive phases to a certain extent. As a consequence, the modification of Ti species greatly improved the SO2 resistance of Cu/SAPO-34-Ti, which could be readily regenerated via thermal treatments after SO2 poisoning.