Unraveling the Unexpected Offset Effects of Cd and SO₂ Deactivation over CeO₂-WO₃/TiO₂ Catalysts for NO_x Reduction

Abstract

It is challenging for selective catalytic reduction (SCR) of NO x by NH 3 due to the coexistence of heavy metal and SO 2 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 2 deactivation over CeO 2 -WO 3 /TiO 2 catalysts, potential candidates for commercial SCR catalysts. Cd-and SO 2 -copoisoned catalysts demonstrated higher activity for NO x reduction than a Cd-poisoned catalyst but lower than that for an SO 2 -poisoned catalyst. In comparison to SO 2 , Cd had more severe effects on acidic and redox properties, distinctly decreasing the SCR activity. After sulfation of Cd-poisoned catalysts, SO 4 2− preferentially bonded with the surface CdO and released CeO 2 active sites poisoned by CdO, thus reserving the highly active CeO 2 -WO 3 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 2 contributed to the high-temperature SCR performance. This work sheds light on the deactivation mechanism of heavy metals and SO 2 over CeO 2 -WO 3 /TiO 2 catalysts and provides an innovative pathway for inventing high-performance SCR catalysts, which have great resistance to heavy metals and SO 2 simultaneously. This will be favorable to academic and practical applications in the future.

Time-resolved in situ DRIFTS study on NH3-SCR of NO on a CeO2/TiO2 catalyst

“…3, which was dominated by characteristic peaks of TiO 2 . The diffraction peaks at 28.6°, 33.1°, 47.5°and 56.3°were attributed to anatase TiO 2 , 26 while the typical peaks of the fluorite structure were not observed. Several broad peaks at 31-28°, 34-32°and 48-47°belonged to cubic CeO 2 species, 20 which was consistent with TEM results.…”

Unraveling the interactions of reductants and reaction path over Cu-ZSM-5 for model coal-gas-SCRviaa transient reaction study

“…Additionally, the band at 1690 cm −1 was from N 2 O 4 species. 33,37 Fig. 6a and f exhibit relatively strong signals at 1690 cm −1 , indicating that the presence of CO could lead to NO 2 formation.…”

Rationally Tailored Redox Properties of a Mesoporous Mn–Fe Spinel Nanostructure for Boosting Low-Temperature Selective Catalytic Reduction of NOx with NH3

“…The in situ DRIFTS results of NO + O 2 co-adsorption on the prepared Mn 0.5 Fe 2.5 O 4 catalysts are displayed in Figure . For the Mn 0.5 Fe 2.5 O 4 -S catalyst, the surface of the catalyst is mainly covered by four kinds of nitrate species, including adsorbed NO 2 (1609 cm –1 ), monodentate nitrate (1546 and 1527 cm –1 ), bidentate nitrate (1584, 1278, 1024, and 993 cm –1 ), and bridging nitrate (1227 cm –1 ). ,− It should be pointed out that the intensity of all peaks become weak gradually as the temperature increases. The peaks at 1024, 1278, and 1527 cm –1 disappear at 200 °C, suggesting that these nitrates are weakly adsorbed species.…”