The different impacts of SO2 and SO3 on Cu/zeolite SCR catalysts

Impact of sulfation and desulfation on NO reduction using Cu-chabazite SCR catalysts

“…SO 2 exposure has a drastic impact on the standard SCR of NO x at temperatures below 250 • C, with conversion decreasing by as much as 45% at 200 • C. This is significant at the lowest operating temperatures observed in marine diesel engines where exhaust temperatures can dip as low as 200 • C. Both aged samples exhibit less than 60% NO x conversion at this temperature, which is well below the conversion required to meet the MARPOL Tier II standards. Furthermore, the lower sulfur exposure temperature results in the most significant deactivation, which agrees with results obtained by Cheng et al [12] who found that NO x conversion decreases as the sulfur aging temperature is decreased, even for low levels of SO 2 exposure. Mild desulfation for only 10 min at 500 • C is not adequate to recover standard SCR performance, but after 30 min of desulfation at 600 • C the NO x conversion is comparable to a de-greened catalyst.…”

“…More recently, sulfur exposure has been studied on small-pore zeolites utilizing SO x concentrations of up to 200 ppm in simulated diesel exhaust, and it was found that SO x can have a significant impact on the NO x reduction activity of smallpore Cu-zeolite catalysts at evaluation temperatures below 300 • C [12][13][14]. The primary degradation mechanisms attributed to the presence of sulfur are the formation of ammonium sulfate at temperatures less than 300 • C and the adsorption of SO x on key sites active for SCR along with the formation of copper sulfate species.…”

“…Prior research has illustrated the sensitivity of Cu-zeolite SCR catalysts to the presence of sulfur in diesel exhaust [6][7][8][9][10], and it has been shown that desulfation can effectively be carried out on sulfated catalysts at temperatures above 600 • C under lean exhaust conditions [11,12]. More recently, sulfur exposure has been studied on small-pore zeolites utilizing SO x concentrations of up to 200 ppm in simulated diesel exhaust, and it was found that SO x can have a significant impact on the NO x reduction activity of smallpore Cu-zeolite catalysts at evaluation temperatures below 300 • C [12][13][14].…”

Pd supported on SnO2–MnO –CeO2 catalysts for low temperature CO oxidation

“…For practical implementation of a low temperature CO oxidation catalyst, the catalyst preferably maintain its initial activity against severe operating conditions, such as changing gas temperature, steam, high and low space velocities, and traces of SO 2 [22][23][24]. However, the effects of these conditions are rarely reported over Pd/CeO 2 based catalysts that are often synthesized via the aforementioned rather complex procedures [3,8,9,[11][12][13][14]21].…”

Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

“…VO x was supported onto the corresponding unique TiO 2 structure following the procedure reported in the literature272829303132. However, the supporting VO x catalyst up to 5 wt% resulted in the lower surface area of 105 m 2 g −1 with 0.19 ccg −1 because of the high calcination temperature at 773 K though the sample still contained large surface area.…”