SCR Deactivation Study for OBD Applications 2012-01-1076
Selective catalytic reduction (SCR) catalysts will be used to
reduce oxides of nitrogen (NOx) emissions from internal
combustion engines in a number of applications. Southwest Research
Institute® (SwRI)® performed an Internal Research & Development
project to study SCR catalyst thermal deactivation. The study
included a V/W/TiO₂ formulation, a Cu-zeolite formulation and an
Fe-zeolite formulation. This work describes NOx timed
response to ammonia (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 diesel emissions fluid (DEF) injection rate, could be used as an
on-board diagnostic (OBD) metric. The objective of this study was
to evaluate the feasibility and practicality of this OBD approach.
While these experiments showed a noticeable trend with aging, there
were also observations and considerations that suggest this
approach may be reasonable as a catalyst-aging evaluation test
method, but impractical for OBD purposes.