a b s t r a c tThis bench reactor study investigates the impact of gaseous sulfur on the NO x reduction activity of Cuchabazite SCR (Cu-CHA) catalysts at SO 2 concentrations representative of marine diesel engine exhaust. After 2 h of 500 ppm SO 2 exposure at 250 and 400 • C in the simulated diesel exhaust gases, the NO x reduction activity of the sulfated Cu-CHA SCR catalysts is severely degraded at evaluation temperatures below 250 • C; however, above 250 • C the impact of sulfur exposure is minimal. EPMA shows that sulfur is located throughout the washcoat and along the entire length of the sulfated samples. Interestingly, BET measurements reveal that the sulfated samples have a 20% decrease in surface area. Furthermore, the sulfated samples show a decrease in NO x /nitrate absorption during NO exposure in a DRIFTS reactor which suggests that Cu sites in the catalyst are blocked by the presence of sulfur. SO 2 exposure also results in an increase in NH 3 storage capacity, possibly due to the formation of ammonium sulfate species in the sulfated samples. In all cases, lean thermal treatments as low as 500 • C reverse the effects of sulfur exposure and restore the NO x reduction activity of the Cu-CHA catalyst to that of the fresh condition.

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Small-pore Cu-chabazite SCR catalysts with high NOx conversion at low temperatures are of interest for marine diesel engines with exhaust temperatures in the range of 150 to 300℃. Unfortunately, fuels for marine diesel engines can contain a high level of sulfur of up to 1.5% by volume, which corresponds to a SO 2 level of 500 ppm in the exhaust gases for an engine operating with an A/F ratio of 50:1. This high level of SO 2 in the exhaust may have detrimental effects on the NOx performance of the Cu-chabazite SCR catalysts. In the present study, a bench-flow reactor is used to investigate the effects of sulfur poisoning on the NOx performance of Cu-chabazite SCR catalysts. The SCR catalysts were exposed to simulated diesel exhaust gas stream consisted of 500 ppm SO 2 , 5% CO 2 , 14% O 2 , 5% H 2 O with N 2 as the balance gas at 150, 200, 250 and 300℃ for 2 hours at a GHSV of 30,000 h-1. After sulfur poisoning the low-temperature NOx performance of the SCR catalyst is evaluated over a temperature range of 150-300℃ to determine the extent of the catalyst deactivation. Desulfation is also carried out at 600 and 700℃ for 30 minutes to determine whether it is possible to recover the NOx performance of the sulfur-poisoned SCR Catalysts.