A typical diesel exhaust emission control system for meeting the
US EPA 2010 regulations includes one or more platinum-group metal
(PGM)-containing catalysts, located upstream of an SCR unit.
However, as was previously reported in literature, under certain
operating conditions PGM elements can get transferred onto the
downstream SCR catalyst, resulting in the loss of its NOx
conversion efficiency. In the same studies, the effect of Pt
poisoning was found to be mitigated by catalyst treatment at 850°C,
presumably due to Pt volatilization and migration.
In the present study, we have explored the process of Pt
poisoning mitigation, and identified that the recovery can take
place at lower temperatures, reducing the risk of hydrothermal
damage to the catalyst. We have also proven that the performance
recovery, observed upon treatment at 700°C, was induced by Pt
sintering, rather than by volatilization, thus minimizing the risk
of secondary poisoning via Pt redistribution across the SCR system.
These findings pave the way for the practical rejuvenation of
zeolite-based SCR catalysts, deactivated through Pt
contamination.