Impact of Oil-derived Sulfur and Phosphorus on Diesel NOx Storage Reduction Catalyst - JCAP II Oil WG Report 2006-01-3312

Emission regulations for diesel-powered vehicles have been gradually tightening. Installation of after-treatment devices such as diesel particulate filters (DPF), NOx storage reduction (NSR) catalysts, and so on is indispensable to satisfy rigorous limits of particulate matter (PM) and nitrogen oxides (NOx). Japan Clean Air Program II Oil Working Group (JCAPII Oil WG) has been investigating the effect of engine oil on advanced diesel after-treatment devices. First of all, we researched the impact of oil-derived ash on continuous regeneration-type diesel particulate filter (CR-DPF), and already reported that the less sulfated ash in oil gave rise to lower pressure drop across CR-DPF [1].

In this paper, impact of oil-derived sulfur and phosphorus on NSR catalyst was investigated using a 4L direct injection common-rail diesel engine with turbo-intercooler. This engine equipped with NSR catalyst meets the Japanese new short-term emission regulations. The test was carried out through the steady state operating condition at medium load and speed. In order to accelerate the influence of sulfur, S purge is cancelled, which is fuel injection control for the recovery from sulfur poisoning. During test duration of 200 hours, NOx conversion ratio of the catalyst was deteriorated mainly by sulfur poisoning from both fuel and oil. On the other hands, catalyst analysis revealed that phosphorus was much less than sulfur on the catalyst surface, resulting that the catalyst degradation by oil-derived phosphorus wasn't recognized.