SCR Deactivation Kinetics for Control, Aging and OBD Applications – Part 1

Gordon  Bartley, Southwest Research Institute

PART 1 – SCR catalysts will be used to reduce NOx emissions from IC engines in a number of applications. SwRI is performing an Internal Research & Development Project to study SCR catalyst thermal deactivation. The study includes a V/W/TiO2 formulation, a Cu-zeolite formulation and a Fe-zeolite formulation.

Part 1 of the work describes NH3 storage capacity measurement data as a function of aging time and temperature. Addressing one objective of the work, these data may be used in model-based control algorithms to calculate the current NH3 storage capacity based on time and temperature history. The model-based control then uses the calculated value for effective DEF control and prevention of excessive NH3 slip. Addressing a second objective of the work, accelerated thermal aging of catalysts may be achieved by elevating temperatures above normal operating temperatures. Time and temperature correlations use the Arrhenius equation, which requires a formulation-specific deactivation energy value. The NH3 storage capacity data are used to calculate a deactivation energy value (Ed) for each of the three formulations.
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PART 2 – SCR catalysts will be used to reduce NOx emissions from IC engines in a number of applications. SwRI is performing an Internal Research & Development Project to study SCR catalyst thermal deactivation. The study includes a V/W/TiO2 formulation, a Cu-zeolite formulation and a Fe-zeolite formulation.

Part 2 of the work describes NOx timed response to NH3 transients as a function of thermal aging time and temperature. It has been proposed that the response time of NOx emissions to NH3 transients effected by changes in DEF injection rate, could be used as an OBD metric. The third objective of the current work evaluates the feasibility and practicality of this OBD approach.

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