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Combined experimental and kinetic modeling study of the bi-modal NOx conversion profile on commercial Cu-SAPO-34 catalyst under standard SCR conditions

Paper ID Volume ID Publish Year Pages File Format Full-Text
45530 46416 2015 9 PDF Available
Title
Combined experimental and kinetic modeling study of the bi-modal NOx conversion profile on commercial Cu-SAPO-34 catalyst under standard SCR conditions
Abstract

•We model bi-modal NOx reduction profile for Cu-SAPO-34 under standard SCR conditions.•The redox activity of the catalyst significantly enhances under SCR conditions.•The rate of NO oxidation increases by orders of magnitude under SCR conditions.•We develop a method to determine washcoat diffusivity of NH3 in Cu-zeolite catalyst.

Bi-modal NOx conversion profile has been consistently reported for selective catalytic reduction (SCR) of NOx with NH3 on certain Cu-exchanged zeolite catalysts under the so-called standard SCR conditions, with two distinct NOx conversion peaks located around 250 and 450 °C. However, the nature of this practically important phenomenon remained unexplained. In this work, we have used a combination of experimental studies and kinetic modeling to characterize and de-convolute several side reactions, allowing us to quantitatively reconstruct the overall bi-modal conversion profile. In particular, we have shown that the first peak can be represented as a competition between the standard SCR reaction and parasitic NH3 oxidation. The subsequent increase in the NOx conversion can be attributed to the onset of in-situ NO oxidation to NO2 that enhances NOx reduction via fast SCR reaction route. Specifically, our modeling study indicates that NO oxidation reaction accelerates by orders of magnitude under the standard SCR conditions and becomes the governing step for NO reduction at high temperature.

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Keywords
Diesel emission control; Chabazite zeolite (CHA); Selective catalytic reduction; Ammonia; NH3 SCR.
First Page Preview
Combined experimental and kinetic modeling study of the bi-modal NOx conversion profile on commercial Cu-SAPO-34 catalyst under standard SCR conditions
Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 165, April 2015, Pages 27–35
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis