Construction dual active sites on confined ordered mesoporous CeWTi catalyst by CuSO4 modification for enhancing SO2 tolerance during low temperature NH3-SCR process

Abstract

The full exposure of the active center is an important reason for the superior performance, and the excellent anti-SO₂ poisoning ability is a key factor to ensure the service life for the low temperature NH₃-SCR catalyst. In this study, the strategy of evaporation-induced self-assembly (EISA) was chosen to directly confined CuSO₄ to the framework structure of ordered mesoporous CeWTiOx (CWT-OM) catalyst. Metal sulfate plays a dual role in low temperature activity and sulfur resistance. When the temperature reached 220 °C, the NO conversion of ordered mesoporous CuSO₄/CeWTiOx (CuCWT-OM) catalyst reached about 90 %. Introduce 100 ppm SO₂ 17.5 h under 260 °C, the conversion of CuCWT-OM catalyst can keep the above 80 %. The introduction of CuSO₄ increased the acidity of CWT-OM catalyst, inhibited the sulfate formed by the reaction of SO₂ with active species, and ensured the number of active sites in the reaction. In addition, the Cu-Ce interface effect accelerates the electron transfer frequency between the active species, stimulates the production of adsorbed NO₂, and promotes the conversion of NO at low temperature. Furthermore, the interface confined effect and the framework confined effect make the active species Cu and Ce firmly confined in the ordered mesoporous framework structure, and reduce the action of SO₂ on the active components. In addition, SO₄²⁻ is more likely to react with W species, protecting the main active species Ce and inhibiting its acidification. This work provides a new feasible idea for improving the low temperature activity and anti-SO₂ poisoning stability of Ce based catalyst.