Mitigation of Platinum Poisoning of Cu-Zeolite SCR Catalysts

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 degrees 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 degrees 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.