Identifying the promotional mechanism for the activity and SO2 resistance of Ce-doped K-OMS-2 for the low-temperature SCR of NO with NH3

Mn-based catalysts for the low-temperature selective catalytic reduction (SCR) of NOx by NH3 can be strongly deactivated due to the generation of MnSO4 derived from upstream SO2 and H2O. In this study, a catalyst architecture based on a Ce-doped manganese oxide octahedral molecular sieve (Ce-OMS-2) was successfully synthesized to promote NH3-SCR activity and enhance SO2 tolerance at low temperatures. We investigated the role of Ce and its specific octahedral molecular sieve structure on the anti-SO2 poisoning effect of Ce-OMS-2. Maintaining the manganese oxide octahedral molecular sieve structure with polyvalent manganese species and active oxygen species and the charge transfer between Mn and Ce via the Ce-O-Mn bond in the Ce-OMS-2 catalyst are found to be the key factors for the realization of excellent NH3-SCR activity and SO2 tolerance. In-depth in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) show that the number of Brønsted acid sites in Ce-OMS-2 can also favor SO2 resistance. This study provides new insight into the mechanism for de-NOx activity and SO2 tolerance on Ce-OMS-2 catalyst and is beneficial for the design of anti-SO2 NH3-SCR catalysts.