Development of Ultra-Low Synergized PGM as Diesel Oxidation Catalyst for Heavy-Duty Applications

Stricter regulatory standards are continuously adopted worldwide to control heavy duty emissions, and at the same time, fuel economy requirements have significantly lowered exhaust temperatures. The net result is a significant increase in Precious Group Metal (PGM) usage with current Diesel Oxidation Catalyst (DOC) technology. Therefore, the design and development of synergized precious metal (SPGM) in which ultra-low PGM is synergized with mixed metal oxide (MMO) to achieve highly beneficial emission performance improvement, is necessary. The presence of MMO in SPGM is responsible for NO oxidation to NO₂ which is critical for the passive regeneration of the downstream filter and SCR function.

This paper presents an initial study outlining the development of MMOs for application in modern DOCs and addresses some specific challenges underlying this application. Lab and flow reactor data in this study demonstrated SPGM DOCs thermal resistance and sulfur poisoning resistance. In addition, SPGM DOC with reduced PGM levels indicated the increase of NO₂ production at T>250 °C compared to OEM benchmarks. This paper outlines the results of engine dyno, transient dyno and on-road testing of SPGM DOCs versus OEM DOCs. The engine testing indicated high level of NO₂ production at significantly reduced PGM levels. On-road testing showed no change or deterioration of the system performance after the switch to SPGM for a heavy duty DOC and filter system. Field data logging during on-road testing showed identical exotherms for the same active regeneration calibration, which results in equivalent DPF regeneration. Disclosed SPGM for on-road heavy-duty applications is consistent with sufficient CO and HC conversion and superior warmed up NO₂ make. Specific challenges remain in the development of the SPGM DOC which is under investigation based on formulation and mechanism of mixed metal oxides.