Sulfur/water resistance and regeneration of MnOx-CeO2/TiO2 catalyst for low-temperature selective catalytic reduction of NOx

Abstract

Mn-based catalysts present a great prospect for application in selective catalytic reduction (SCR) of NOx with NH3 at low temperatures, due to their high low-temperature catalytic activity. However, poor resistance of Mn-based catalysts to SO2 and H2O restricts their industrial application. This paper investigates the SO2&H2O resistance of MnOx-CeO2/TiO2 catalyst and discusses the poisoning mechanism based on catalytic characterizations. The results indicate that MnOx-CeO2/TiO2 catalyst exhibit high tolerance to SO2 poisoning mainly because the surface sulfates are preferentially formed on Ce dopants so that protect the main active component (MnOx). Catalytic deactivation become more severe when SO2&H2O are simultaneously present, which implies that SO2&H2O exhibit a synergistic toxicity in poisoning catalyst. Interestingly, the presence of H2O can alleviate the formation of surface metal sulfates on catalyst to some extent, for the surface reactive oxygen species and the surface acid sites are preserved to fulfill the low temperature SCR reaction cycle. Thermal regenerations under different atmosphere (e.g., O2 and H2O) are conducted for the SO2 poisoned catalyst. Effective regeneration of the sulfated catalyst can be realized and their regeneration mechanisms are explored by utilization of several catalytic characterizations.