A Multi-Site Kinetic Model for NH3-SCR over Cu/SSZ-13

Louise  Olsson, Chalmers University

A Multi-Site Kinetic Model for NH3-SCR over Cu/SSZ-13

Louise Olsson1,*, Kurnia Wijayanti1, Kirsten Leistner1, Ashok Kumar2, Saurabh Y. Joshi2, Krishna Kamasamudram2, Neal W. Currier2, Aleksey Yezerets2

1 Chemical Engineering; Competence Centre for Catalysis, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
2 Cummins Inc., 1900 McKinley Avenue, MC 50183, Columbus, IN 47201, USA

We have developed a kinetic model for ammonia-SCR over a well-characterized Cu/SSZ-13 catalyst [1]. In order to describe the ammonia adsorption and desorption, ammonia oxidation and standard SCR over a broad temperature range three sites were needed. The physical interpretation of these three sites is: copper in the six-membered rings (S1), copper in the large cages (S2) and physisorbed sites (S3). In addition, ammonia is also stored on Bronsted acid sites, but in order not to complicate the model further, it was lumped together in the S1 sites. We propose that ammonia oxidation occurs primarily over the S2 sites and ammonia SCR over S1 sits. However, in order to describe the whole temperature range it was necessary to add the reactions on both sites. To conclude, the three-site model developed was capable of well describing the experimental features for ammonia adsorption and desorption, ammonia oxidation as well as SCR and N2O formation over a large temperature interval (100 to 600°C).

Reference
[1] L. Olsson, K. Wijayanti, K. Leistner, A. Kumar, S. Joshi, K. Kamasamudram, N.W. Currier and A. Yezerets, Submitted., (2014).

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