Insight into SO2 poisoning mechanism of MnOx-CeO2/Ti-bearing blast furnace slag catalyst for low temperature NH3-SCR reaction

Abstract

Sulfur poisoning is an intractable challenge for NH₃-SCR catalyst. In this issue, the immanent reasons for MnO_x-CeO₂/Ti-bearing blast furnace slag catalyst deactivation resulting from SO₂ were elaborated by catalytic activity evaluation, BET, XRD, XPS, NH₃-TPD, H₂-TPR and in-situ DRIFTS analysis. Results showed that MnO_x-CeO₂/Ti-bearing blast furnace slag catalyst followed E-R reaction mechanism and performed 100 % NO conversion at 175 °C, whereas its sulfur resistance was unsatisfactory and the deactivation degree became more severe with SO₂ concentration increasing. SO₂ reacted with NH₃ to generate (NH₄)₂SO₄ and NH₄HSO₄ deposits, blocking catalyst pores and covering active sites. SO₂ also interacted with MnO_x-CeO₂ active components to form MnSO₄ and Ce₂(SO₄)₃, which restricted the electron transfers of Mn⁴⁺/Mnⁿ⁺ and Ce³⁺/Ce⁴⁺. Besides, the newly formed sulfur-containing acidic sites also competed with the original active sites for NH₃ adsorption, thereby hindering the SCR reaction. Physical purging could not realize regeneration of SO₂-poisoning catalyst, but hyperthermic treatment was an efficient solution.