Selective catalytic reduction of NO by NH3 over CuO–CeO2 in the presence of SO2

Abstract

SO₂-induced deactivation of selective catalytic reduction of NO over CuO–CeO₂ was studied. In the case of reaction under low O₂ concentration of 1.0 vol%, SO₂ severely deactivated the catalyst at 240 °C with a surface S atomic concentration as low as 1.34%. However, the deactivated catalyst could be reactivated during online NO reduction under 5.0 vol% O₂ without decreasing the surface S concentration of the catalyst, which could be attributed to the involvement of NO₂ in the reactions. NO₂ could promote the NO removal through three reaction routes: fast SCR reaction, reaction between NO₂ and NH₃, and reaction between NO₂ and NH₄⁺. Especially under conditions of 10% O₂, the reaction between NO₂ and NH₃/NH₄⁺ induced the formation of extra NH_X<3 species which promoted the decomposition of surface-deposited sulfate to SO₂ with the assistance of Ce₂O₃, further suppressed the accumulation of sulfate on the catalyst surface, and finally suppressed the SO₂-induced catalyst deactivation.