Nb₂O₅-modified Mn-Ce/AC catalyst with high ZnCl₂ and SO₂ tolerance for low-temperature NH₃-SCR of NO

Zinc salts and SO₂ would cause Mn-Ce/AC catalyst poisoning, reducing the service life of the catalyst. In this study, the effects of Nb₂O₅ on the tolerance of ZnCl₂ and SO₂ over Mn-Ce/AC catalyst were studied by the characterization results of BET, SEM, XRD, H₂-TPR, NH₃-TPD, TG and XPS. It indicated that doping Nb₂O₅ could effectively enhance the SCR performance and N₂ selectivity of Zn-Mn-Ce/AC catalyst. Meanwhile, Nb₂O₅ could significantly improve the SO₂ poisoning resistance of Zn-Mn-Ce/AC catalyst when sulfur dioxide was added into the reaction system. Nb₂O₅ could react with SO₂ in a preferential way to restrain the sulfuration of manganese and cerium oxides on the catalyst. More importantly, Nb₂O₅ reacted with SO₂ to form Nb sulfate and then formed a new acidic site on the Zn-Mn-Ce/AC catalyst surface, which promoted the adsorption of NH₃ and inhibited the adsorption of SO₂, then restricted the reaction between NH₃ and SO₂ and hindered the formation of ammonium sulfate channels.