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Development of Advanced Ultra-Low PGM DOC for BS VI DOC+CDPF+SCR System
Abstract:
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 advanced DOC with ultra-low PGM to achieve highly beneficial emission performance improvement is necessary. The advanced DOC is synergized PGM (SPGM) with Mixed Metal Oxide (MMO). 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 outlines the development of MMO for application in modern DOCs and addresses some specific challenges underlying this application. Lab and flow reactor data demonstrates MMO by itself owns great oxidation properties with high surface area available for NO oxidation reaction. In addition, SPGM DOC with reduced PGM levels indicated thermal resistance and sensitivity to type of hydrocarbon in gas stream. This paper summaries the results of engine dyno and on-road testing of SPGM DOC versus OEM DOCs. The engine testing indicated high level of NO2 production at significantly reduced PGM levels. On-road testing on DOC/CDPF/SCR system showed no change or deterioration of the system performance after the switch OEM DOC to SPGM DOC. Field data logging during on-road testing showed identical exotherms for both systems and great NOX conversion and enough NO2 formation when ultra-low SPGM used as advanced DOC. Specific challenges remain in the development of the SPGM DOC which is under investigation based on formulation and mechanism of MMO.