Unraveling the Unexpected Offset Effects of Cd and SO Deactivation over CeO-WO/TiO Catalysts for NO Reduction.

It is challenging for selective catalytic reduction (SCR) of NO by NH due to the coexistence of heavy metal and SO in the flue gas. A thorough probe into deactivation mechanisms is imperative but still lacking. This study unravels unexpected offset effects of Cd and SO deactivation over CeO-WO/TiO catalysts, potential candidates for commercial SCR catalysts. Cd- and SO-copoisoned catalysts demonstrated higher activity for NO reduction than a Cd-poisoned catalyst but lower than that for an SO-poisoned catalyst. In comparison to SO, Cd had more severe effects on acidic and redox properties, distinctly decreasing the SCR activity. After sulfation of Cd-poisoned catalysts, SO preferentially bonded with the surface CdO and released CeO active sites poisoned by CdO, thus reserving the highly active CeO-WO sites and maintaining a high activity. The sulfation of Cd-poisoned catalysts also provided more strong acidic sites, and the synergistic effects between the formed cerium sulfate and CeO contributed to the high-temperature SCR performance. This work sheds light on the deactivation mechanism of heavy metals and SO over CeO-WO/TiO catalysts and provides an innovative pathway for inventing high-performance SCR catalysts, which have great resistance to heavy metals and SO simultaneously. This will be favorable to academic and practical applications in the future.