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

Sulfur poisoning is an intractable challenge for NH3-SCR catalyst. In this issue, the immanent reasons for MnOx- 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 MnOx-CeO2/Ti- bearing blast furnace slag catalyst followed E-R reaction mechanism and performed 100 % NO conversion at 175 degrees 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 MnOx-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.