Regeneration of Aged Commercial Three-Way Catalysts Using CI-Containing Reagents

The present work is focused on applying washing treatments using Cl-containing reagents, such as di-chloroacetic acid (DCA) for the first time, and 1,2-di-chloropropane, DCP (0.1 M) solutions in regaining the activity and oxygen storage capacity (OSC) of an aged commercial Pd-based TWC. Segments extracted from an aged (56,000 km) commercial Pd/Rh-based (9:1) TWC after washing with DCA resulted in 100 % removal of Pb and about 43 % of P, while washing with DCP solution was ineffective in removing these specific contaminants. DCA-washing regeneration method was found to increase Pd surface concentration by four times compared to the aged TWC, whereas DCP-washing was considerably less effective than DCA in recovering Pd active sites. The OSC of the aged catalyst was significantly improved by the use of DCA-washing, whereas no improvement was observed by DCP-washing. Nevertheless, DCP-washing was found to be more effective in improving the performance of aged TWC towards CO oxidation. The removal of Pb is likely a reason for the DCA-washing being more effective in improving C₃H₆ and NO conversions and OSC.