The Diesel Particulate and NOx Reduction System (DPNR) is an effective technology as a diesel after-treatment system, which can reduce particulate matter (PM) and nitrogen oxides (NOx) simultaneously. However, it requires desulfurization control since the DPNR catalyst is poisoned by sulfur components in the exhaust gas from the fuel and lubricant. Desulfurization control causes some degree of fuel penalty and thermal deterioration of the DPNR catalyst because it requires control of rich air fuel ratio and high temperature simultaneously.
In this paper, we investigated a new system with a sulfur trap catalyst which can trap sulfur components included in the exhaust gas as sulfates (Sulfur trap DPNR). In this system, desulfurization control is not performed because the sulfur poisoning of the DPNR catalyst is drastically suppressed by the sulfur trap catalyst. In the present DPNR, periodic desulfurization control is required. However, it is shown that the Sulfur trap DPNR has a high NOx conversion efficiency of 80% after 40,000km is driven without the desulfurization.
It is expected that the durability performance of DPNR with a sulfur trap catalyst will be further improved and the desulfurization and replacement of sulfur trap catalyst is not required throughout the useful life by improvements of a sulfur trap catalyst and reduction of sulfur components in fuel and lubricant. Consequently, substantial improvement of the DPNR catalyst can be expected if the DPNR catalyst can be designed without having to consider sulfur poisoning, desulfurization performance and thermal deterioration caused by desulfurization control. The possibility of Sulfur trap DPNR resulting in lower NOx is shown by this research.