Reversible and irreversible deactivation of Cu-CHA NH^sub 3^-SCRcatalysts by SO^sub 2^ and SO^sub 3

Sulfur oxides are a common source for the deactivation of Cu-exchanged CHA zeolite based catalysts used for NOx reduction in diesel exhausts by selective catalytic reduction with NH3 (NH3-SCR). Since water and possible formation of SO3 affect the deactivation of Cu-CFIA catalysts, the deactivation i...

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Bibliographic Details
Published inApplied catalysis. B, Environmental Vol. 226; p. 38
Main Authors Hammershøi, Peter S, Jangjou, Yasser, Epling, William S, Jensen, Anker D, Janssens, Ton VW
Format Journal Article
LanguageEnglish
Published Amsterdam Elsevier BV 15.06.2018
Subjects
Activation energy
Air pollution control
Ammonia
Catalysis
Catalysts
Deactivation
Energy
Exhaust systems
Exhausts
Nitrogen oxides
Oxides
Regeneration
Selective catalytic reduction
Studies
Sulfates
Sulfur
Sulfur dioxide
Sulfur oxides
Sulfur trioxide
Zeolites
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Summary:Sulfur oxides are a common source for the deactivation of Cu-exchanged CHA zeolite based catalysts used for NOx reduction in diesel exhausts by selective catalytic reduction with NH3 (NH3-SCR). Since water and possible formation of SO3 affect the deactivation of Cu-CFIA catalysts, the deactivation in the presence of SO2 or a mixture of SO2 and SO3 was studied by measuring the SCR activity in wet and dry gas at 200 and 550 °Celsius. The estimated 5-content in the catalysts before and after 4 h regeneration at 550 °Celsius in NO, NH3, 02 and H2O was related to the deactivation. The deactivation can be divided into two parts: a reversible deactivation that is restored by the regeneration treatment, and an irreversible part. The irreversible deactivation does not affect the activation energy for NH3-SCR and display a 1:1 correlation with the S-content, consistent with deactivation by Cu-sulfate formation. The reversible deactivation results in a lower activation energy and a deactivation that is larger than expected from the S-content. The presence of 503 at 200 °Celsius leads to higher reversible and irreversible deactivation, but has no significant impact at 550 °Celsius. Furthermore, the irreversible deactivation is always higher when exposed at 200 °Celsius than at 550 °Celsius, and in wet conditions, compared to a dry feed. The deactivation is predominantly reversible, making regeneration at 550 °Celsius a realistic approach to handle S-poisoning in exhaust systems.
ISSN:0926-3373
1873-3883