How Cu-SSZ-13 Oxidation Activity Affects the Extent of Sulfur Poisoning
Yu-Ren Chen, University of Virginia
Cu-SSZ-13 is an effective catalyst for selective catalytic reduction (SCR) reactions, but sulfur poisoning remains a problem. A mild hydrothermal aging pretreatment has been reported to alleviate the catalyst’s sulfur poisoning problem, which was explained by a decrease in the relative amount of ZCuOH. Our experimental data show that although a mild hydrothermal aging pretreatment protects the catalyst from SO2 poisoning in the absence of water, it does not from SO3 poisoning. Through this observation and analyzing the temperature and the O2 concentration effects during SO2 exposures, we concluded that SO2 oxidation is the root of sulfur poisoning in the absence of water and deactivation depends on oxidation activity, which is a function of the Cu species. In terms of the sulfur exposure in the presence of water, the catalyst’s deactivation trend still depends on its oxidation activity. However, the presence of water also leads to further deactivation than in its absence. The water effect is apparent under conditions where catalytic oxidation activity is relatively weak, and becomes less significant as the oxidation activity increases.