Ceria–tungsten–tin oxide catalysts with superior regeneration capacity after sulfur poisoning for NH3-SCR process

Abstract

Nowadays, there exists a trade-off between high-temperature thermal stability and low-temperature catalytic activity for metal oxide catalysts for the NH₃-SCR reaction, which restricts the practical application of metal oxide catalysts on diesel vehicles for NO_x emission control. In this work, we systematically investigated the relationship between catalytic performance and thermal durability over a novel Ce–W–Sn ternary oxide (CeWSnO_x) catalyst by varying the calcination temperature over the range 500–900 °C. Instead of thermal deactivation, the NH₃-SCR performance of the CeWSnO_x catalyst was significantly improved by roasting treatment at temperatures as high as 800 °C. Additionally, in situ SO₂ poisoning led to the loss of the low-temperature activity for the optimized CeWSnO_x-800 catalyst. The superior thermal stability of the CeWSnO_x-800 catalyst and the poor thermal stability of the formed sulfates, however, made full thermal regeneration of the sulfur-poisoned catalyst feasible below 700 °C. The anti-sintering characteristics, SO₂ poisoning mechanism and thermal regeneration capacity after SO₂ poisoning of the CeWSnO_x-800 catalyst were explored in detail by different characterization methods. We expect that this study can shed some light on the development of Ce-based catalysts for NO_x removal from diesel exhaust possessing high thermal stability, catalytic activity and SO₂ tolerance.