Comparative Study of DOC Volume and PGM Loading on Exotherm and HC Slip during Active DPF Regeneration

The diesel oxidation catalyst (DOC) is one of the major components of a diesel after treatment system. Earlier, DOCs were majorly used to oxidise un-burnt HC and CO from the exhaust gas to keep these pollutants within legislation limits. As legislative norms evolved towards becoming more stringent, the technology and chemistry of after-treatment catalysts have also advanced simultaneously. For Diesel Engines to meet BSVI emission norm, the DOC has a vital role to play. Apart from oxidizing un-burnt THC and CO, now it has to perform additional functions of converting NOx to NO2 to achieve desired NO2/NOx ratio for better DeNOx in the SCR and also give efficient exotherm across it when the cat burner fuel is injected during DPF Regeneration with minimal HC slip.

In this paper, two DOCs having different PGM loadings and volumes are evaluated for their exothermal efficiencies and corresponding THC slips. These DOCs are zonal coated and have different split of Pt:Pd ratios across its length. This study primarily entails in determining whether PGM loading or DOC volume is detrimental factor for exothermal efficiency and HC slip across the DOC. Tests with different post injection quantities at different exhaust mass flows were done to study the effect.