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A kinetic model for sulfur poisoning and regeneration of Cu/SSZ-13 used for NH3-SCR

Paper ID Volume ID Publish Year Pages File Format Full-Text
45169 46401 2016 13 PDF Available
Title
A kinetic model for sulfur poisoning and regeneration of Cu/SSZ-13 used for NH3-SCR
Abstract

•Sulfur poisoning and regeneration of NH3-SCR over Cu/SSZ-13 were studied.•A kinetic model was developed that describes the poisoning and regeneration well.•In the model, SO2 was adsorbed on the sites containing copper.•Precursors for ammonium sulfates were added to the model to describe the increased NH3 storage.•Reaction steps where the NH3-sulfur species decomposed to form SO2 were important for the model.

In this study, we have developed a multi-site kinetic model that describes the sulfur poisoning and gradual sulfur removal over Cu/SSZ-13 used for NH3-SCR. Sulfur poisoning was conducted under SCR conditions and thereafter, repeated SCR experiments were conducted to examine the effect of such poisoning and the subsequent gradual removal of sulfur. In addition, the effect of sulfur poisoning was examined on NH3 TPD and ammonia oxidation experiments. The following sites were used in the kinetic model: copper in the six-membered rings as described by S1Cu, copper in the larger cages with S2 and S3 as a site where physisorbed ammonia can attach. Further, ammonia was also adsorbed on the Brönsted sites, represented by S1Brön in the model, but in order not to further complicate the model, small amounts of ammonia storage on Brönsted sites were also lumped into S2. In the model, SO2 was adsorbed on the sites containing copper, which are S1Cu and S2. It should be noted that S1Cu and S2 represents hydrated copper sites. Interestingly, we observed experimentally that ammonia storage was larger after sulfur poisoning compared to before, which is why we added ammonia storage and desorption to the S1Cu–SO2 and S2–SO2 sites. However, ammonia was already adsorbing on the copper site; thus, these steps did not result in increased storage. Consequently, reaction steps were added where additional ammonia was adsorbed to form S1Cu–SO2–(NH3)2 and S2–SO2–(NH3)2 species, which could be interpreted as precursors to ammonium sulfates. Another aspect that must be addressed in the model is the observation in the literature that SO2 is more easily desorbed in SO2 + NH3 + O2 TPD than SO2 + O2 TPD. Reversible reaction steps were therefore added whereby the S1Cu–SO2–NH3 and S2–SO2-NH3 species were decomposed to form SO2. A final reaction step was incorporated into the model to describe the SCR reaction with ammonia attached to the sulfur sites. The developed model could well describe the sulfur poisoning and gradual regeneration during repeated SCR experiments. In addition, the model well described the NH3 TPD and NH3 oxidation before and after sulfur poisoning.

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Keywords
Kinetic model; Ammonia-SCR; Sulfur poisoning; Cu/SSZ-13; Cu-zeolites
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A kinetic model for sulfur poisoning and regeneration of Cu/SSZ-13 used for NH3-SCR
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 183, April 2016, Pages 394–406
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