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Kinetic modeling of sulfur poisoning and regeneration of lean NOx traps

Paper ID Volume ID Publish Year Pages File Format Full-Text
47139 46462 2010 11 PDF Available
Title
Kinetic modeling of sulfur poisoning and regeneration of lean NOx traps
Abstract

Sulfur poisoning and regeneration of lean NOx traps were investigated using experiments and kinetic modeling. A commercial Pt, Rh and barium containing NOx storage catalyst was used. The catalyst also contained oxygen storage material. First the oxygen storage capacity (OSC) was investigated using steps with oxygen and hydrogen. The OSC was substantial with a total use of all hydrogen (1%) for about 20 s. The results were similar at the three investigated temperatures (300, 400 and 500 °C), indicating that it is a low activation barrier connected with the process. Further, no effect was observed when adding 15 ppm SO2 to the feed. Since no SO2 was observed in the outlet it is possible that SO2 is adsorbed during the lean period and then reduced to form H2S in the rich period (not measured). Further, the NOx storage was found to decrease during SO2 exposure, and the decrease was linear and dose dependent. In addition, we investigated different regeneration strategies. When using 500 ppm H2 for 60 min at 700 °C the regeneration was poor. However, when adding 5% CO2 to the 500 ppm H2 the regeneration was increased drastically. Further, the regeneration was decreased when decreasing the temperature to 600 °C, and further decreased when using 500 °C. In addition, it was beneficial with increasing the hydrogen concentration. The kinetic model contains three sub-models: (i) NOx storage and regeneration, (ii) oxygen storage and reduction and (iii) sulfur poisoning and sulfur regeneration. It was crucial to add NOx storage on two sites; barium and alumina. The NOx adsorbed on alumina is more loosely bound. Further, in the model formation of sulfates were added on both components. This was important in order to describe the rate of the sulfur deactivation. If sulfur was adsorbed only on barium the deactivation would have been too rapid. The model could describe the experimental features well.

Graphical abstractA kinetic model is developed that can describe the sulfur poisoning and regeneration of lean NOx traps. In the figure NOx storage cycles is shown after sulfur regeneration at different temperatures.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights▶ Kinetic model for sulfur poisoning of lean NOx traps. ▶ Kinetic model for sulfur regeneration of lean NOx traps. ▶ CO2 increases sulfur regeneration rate. ▶ Different SO2 regeneration strategies were investigated.

Keywords
Catalyst deactivation; Kinetic modeling; Lean NOx traps; NOx storage; SO2; Sulfur poisoning and regeneration
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 100, Issues 1–2, 11 October 2010, Pages 31–41
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us