Poisoning Effect of SO2 on Honeycomb Cordierite- Based Mn–Ce/Al2O3Catalysts for NO Reduction with NH3 at Low Temperature

Honeycomb cordierite-based Mn–Ce/Al2O3 catalysts were prepared by the impregnation method and used for low-temperature selective catalytic reduction (SCR) of NOx with NH3, with and without SO2 and/or H2O in a homemade fixed-bed tubular reactor. The catalyst reached nearly 80% NOx conversion at 100 ◦C in the absence of SO2. However, SO2 reduces the catalytic activity (80% to 72%) of the honeycomb cordierite-based Mn–Ce/Al2O3 catalysts under identical conditions. This finding demonstrated that the catalyst exhibited high activity at low temperature and excellent SO2 resistance in the presence of 50 ppm SO2. The fresh and sulfated honeycomb cordierite-based Mn–Ce/Al2O3 catalysts were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), N2 adsorption–desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetry and differential thermal analysis (TG-DTA), and Fourier transform infrared (FT-IR) spectroscopy. Characterization results indicated that the deactivation by SO2 was primarily the result of the deposition of ammonium hydrogen sulfate and sulfated CeO2 on the catalyst surface during the SCR process. The formed sulfates depressed the catalytic activity via the blocking of pores and the occupation of active sites. Additionally, the competitive adsorption between SO2 and NH3 always decreased the catalytic activity.