Self-Protected CeO 2 –SnO 2 @SO 4 2– /TiO 2 Catalysts with Extraordinary Resistance to Alkali and Heavy Metals for NO x Reduction

Reducing the poisoning effect of alkali and heavy metals over ammonia selective catalytic reduction (NH 3 -SCR) catalysts is still an intractable issue, as the presence of K and Pb in fly ash greatly hampers their catalytic activity by impairing the acidity and affecting the redox properties of the catalysts, leading to the reduction in the lifetime of SCR catalysts. To address this issue, we propose a novel self-protected antipoisoning mechanism by designing SO 4 2– /TiO 2 superacid supported CeO 2 –SnO 2 catalysts. Owing to the synergistic effect between CeO 2 and SnO 2 and the strong acidity originating from the SO 4 2– /TiO 2 superacid, the catalysts show superior catalytic activity over a wide temperature range (240–510 °C). Moreover, when K or/and Pb are deposited on SO 4 2– /TiO 2 catalysts, the bond effect between SO 4 2– and Ti–O would be broken so that the sulfate in the bulk of SO 4 2– /TiO 2 superacid support would be induced to migrate to the surface to bond with K and Pb, thus prohibiting poisons from attacking the Ce–Sn active sites, and significantly boosting the resistance. Hopefully, this novel self-protection mechanism derived from the migration of sulfate in the SO 4 2– /TiO 2 superacid to resist alkali and heavy metals provides a new avenue for designing novel catalysts with outstanding resistance to alkali and heavy metals.