Local ammonia storage and ammonia inhibition in a monolithic copper-beta zeolite SCR catalyst
Journal article, 2012

Selective catalytic reduction of NO with NH3 was studied on a Cu-beta zeolite catalyst, with specific focus on the distributed NH3 capacity utilization and inhibition. In addition, several other relevant catalyst parameter distributions were quantified including the SCR zone, or catalyst region where SCR occurs, and NO and NH3 oxidation. We show that the full NH3 capacity (100% coverage) is used within the SCR zone for a range of temperatures. By corollary, unused NH3 capacity exists downstream of the SCR zone. Consequently, the unused capacity relative to the total capacity is indicative of the portion of the catalyst unused for SCR. Dynamic NH3 inhibition distributions, which create local transient conversion inflections, are measured. Dynamic inhibition is observed where the gas phase NH3 and NO concentrations are high, driving rapid NH3 coverage buildup and SCR. Accordingly, we observe dynamic inhibition at low temperatures and in hydrothermally aged states, but predict its existence very near the catalyst front in higher conversion conditions where we did not specifically monitor its impact. While this paper addresses some general distributed SCR performance parameters including Oxidation and SCR zone, our major new contributions are associated with the NH3 capacity saturation within the SCR zone and dynamic inhibition distributions and the associated observations. These new insights are relevant to developing accurate models, designs and control strategies for automotive SCR catalyst applications.



reduction catalyst


Distributed reactions



selective reduction

NH3 capacity

diesel exhaust





nox storage

no(x) storage

NH3 inhibition

alumina catalysts


Xavier Auvray

Chalmers, Chemical and Biological Engineering, Chemical Reaction Engineering

W. P. Partridge

Oak Ridge National Laboratory

J. S. Choi

Oak Ridge National Laboratory

J. A. Pihl

Oak Ridge National Laboratory

A. Yezerets

Cummins Inc.

K. Kamasamudram

Cummins Inc.

N. W. Currier

Cummins Inc.

Louise Olsson

Chalmers, Chemical and Biological Engineering, Chemical Reaction Engineering

Competence Centre for Catalysis (KCK)

Applied Catalysis B: Environmental

0926-3373 (ISSN) 1873-3883 (eISSN)

Vol. 126 144-152

Areas of Advance


Materials Science

Subject Categories

Chemical Sciences



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