Promotion of Fe and Co doped Mn-Ce/TiO2 catalysts for low temperature NH3-SCR with SO2 tolerance. (1st August 2019) - Wang, Fumei
Graphical abstract: Highlights: Fe and Co co-doped (Fe/Co = 2:4) Mn-Ce/TiO2 exhibited higher SCR activity and excellent SO2 resistance. Reversible inhibition happened owe to the formation of (NH4 )2 SO4 or NH4 HSO4 . Irreversible deactivation of Mn-Ce/TiO2 occurred by SO2 due to the formation of high thermally stable sulfated species. The uniform distribution of Fe and Co on the Mn-Ce/TiO2 surface stopped SO2 diffusing to the inner layer of catalyst. NH3 -SCR reaction over 2Fe4Co-MCT was mainly dominated by E-R mechanism in the presence of SO2 . Abstract: Fe and Co doped Mn-Ce/TiO2 catalysts for low temperature NH3 -SCR with SO2 resistance were investigated via in-situ DRIFTS, SO2 -TPD and FTIR. The activity results indicated that Fe and Co co-doped catalyst with an Fe/Co molar ratio of 2:4 (2Fe4Co-MCT) showed excellent SO2 resistance (98% NO conversion) at 200 °C when compared to the Mn-Ce/TiO2 catalyst. In-situ DRIFTS and SO2 -TPD results showed that SO2 reacted with NH3 to form (NH4 )2 SO4 or NH4 HSO4 as reversible deactivation blocking the active sites. Moreover, SO2 -TPD results further implied that irreversible deactivation of Mn-Ce/TiO2 occurred by SO2 due to the formation of thermal stable sulfated species (MnSO4, Ce(SO4 )2 or Ce2 (SO4 )3 ) to reduce active substances. The adsorption characteristics by in-situ DRIFTS revealed that more absorbed SO3, surface sulfite/sulfate and bulk-like sulfate species were formed on Mn-Ce/TiO2 catalyst, while Fe and Co addition to Mn-Ce/TiO2 significantly decreased the sulfur adsorption. The uniform distribution of Fe and Co on the Mn-Ce/TiO2 surface stopped SO2 diffusing to the inner layer of catalyst. In-situ DRIFTS also illustrated that the SCR reaction over 2Fe4Co-MCT catalysts mainly followed by Eley–Rideal (E–R) mechanism in the presence of SO2, which the adsorbed NH3 and NH4 + species reacted with gaseous NO species to produce unstable NH4 NO2 and then rapidly decomposed into N2 and H2 O.