Sulfur Poisoning Impacts on SCR over Cu-SAPO-34
William Epling, University of Houston
Sulfur poisoning is still a durability issue for base metal/zeolite selective catalytic reduction (SCR) catalysts used for abatement of NOx. Most studies have used SO2 as the S poison. However, as diesel oxidation catalysts (DOCs) are employed upstream of the SCR catalyst, it is likely that some of the SO2 is oxidized into SO3. Therefore, investigating the impact of SO3 on Cu/zeolite SCR catalyst is also critical.
Literature reveals that all zeolite-based SCR catalysts are susceptible to sulfation with low temperature SO3 exposure. Major sulfation modes most likely involve formation of (NH4)HSO4, (NH4)2SO4 or CuSO4. It has been proposed that SO2 and SO3 have different sulfur poisoning mechanisms; however, a detailed mechanism has not been determined. In this study, we have investigated the poisoning effects of SO2 and SO3 on the SCR reaction over a Cu-SAPO-34 catalyst.