New DOC for Light Duty Diesel DPF System 2007-01-1920
A new state of the art DOC (Diesel Oxidation Catalyst) having superior light-off and exothermic activity for forced regeneration compared to conventional Pt base passive DOC, was investigated for LDD application.
The DOC uses the latest Pt/Pd technology resulting cost effective DPF system. The newly developed DOC demonstrated improved catalytic activities from Pt only DOC in model gas or engine bench tests. In this study, DOC at early development stage showed excellent light-off activity in model gas and engine bench test compared to conventional Pt only DOC, however, it showed “extinction” phenomenon which is one of the deactivation mode while the post injection and it was observed when post injection operation was done at lower DOC inlet temperatures, e.g. below 250 C. Temperature profiles along diameter and length into DOC bed while active regeneration suggested extinction would be caused by fouling of supplied hydrocarbons derived from diesel fuel. Through the various approach to improve this phenomenon, the exothermic ability at low temperatures was greatly improved by using newly developed catalyst technologies. Furthermore, S tolerance of Pt/Pd DOC was investigated in this study since the largest concern to apply Pd contained DOC to diesel application was S poisoning. It was confirmed that the newly developed Pt/Pd DOC has acceptable S tolerance in model gas test which was designed considering practical driving conditions.