Sulfur Management of NOx Adsorber Technology for Diesel Light-duty Vehicle and Truck Applications

Abstract

Sulfur poisoning from engine fuel and lube is one of the most recognizable degradation mechanisms of a NO x adsorber catalyst system for diesel emission reduction. Even with the availability of 15 ppm sulfur diesel fuel, NO x adsorber will be deactivated without an effective sulfur management. Two general pathways are currently being explored for sulfur management: (1) the use of a disposable SO x trap that can be replaced or rejuvenated offline periodically, and (2) the use of diesel fuel injection in the exhaust and high temperature de-sulfation approach to remove the sulfur poisons to recover the NO x trapping efficiency. The major concern of the de-sulfation process is the many prolonged high temperature rich cycles that catalyst will encounter during its useful life. It is shown that NO x adsorber catalyst suffers some loss of its trapping capacity upon high temperature lean-rich exposure. With the use of a disposable SO x trap to remove large portion of the sulfur poisons from the exhaust, the NO x adsorber catalyst can be protected and the numbers of de-sulfation events can be greatly reduced.Spectroscopic techniques, such as DRIFTS and Raman, have been used to monitor the underlying chemical reactions during NO x trapping/ regeneration and de-sulfation periods, and provide a fundamental understanding of NO x storage capacity and catalyst degradation mechanism using model catalysts. This paper examines the sulfur effect on two model NO x adsorber catalysts. The chemistry of SO x /base metal oxides and the sulfation product pathways and their corresponding spectroscopic data are discussed.

Influence of Potassium Doping on the Activity and the Sulfur Poisoning Resistance of Soot Oxidation Catalysts

“…This result indicates the preferential sulfatization of potassium in comparison to cerium and manganese, as no peaks corresponding to manganese or cerium sulfate were observed. This finding is also in agreement with literature data on SO 2 storage on alkali metal containing compounds [18,19].…”

SOx storage and release kinetics for ceria-supported platinum

“…One strategy is to prevent SO x from reaching the NSC by including a, so-called, sulfur trap upstream the NSC in the aftertreatment system. Two different types of upstream sulfur traps have been proposed earlier, i.e., disposable [3] and regenerable [5]. Here, the latter is considered to be used under continuously lean conditions.…”

Desulfurization Effects on a Light-Duty Diesel Vehicle NOx Adsorber Exhaust Emission Control System

“…Tests have shown that NACs suffer a loss in conversion efficiency when exposed to high-temperature, lean-rich conditions. This loss becomes greater as temperature increases [4]. Emissions before desulfurization at 300 hours showed a steep increase in NO x .…”