Effectiveness of Desulfation Protocols on Dynamometer Aged LNT-SCR Systems

Rachel  Snow, Ford Motor Company

LNT-SCR systems were aged using two different desulfation protocols. Aging consisted of three modes, including sulfur exposure, desulfation (deSOx), and DPF regeneration conditions. Evaluations on an engine dynamometer at the end of 50,000 mile equivalent aging found significant differences in aftertreatment components performance, yet nearly equal overall system NOx conversion.

LNT NOx conversion was significantly lower for the case where maximum temperatures reached only 730°C, as opposed to the more severe aging where temperatures reached 800°C. NOx conversion over the SCR was higher for the 730°C maximum temperature aging, resulting in nearly equal overall system gross NOx conversion for the two systems.

Differences in component performance may have resulted from loss of catalytic oxidation/reduction function on the DOC/LNT, separation of PM from the storage sites on the LNT, and/or poisoning of the catalysts from either HC and/or sulfur. The sulfur release characteristics as a function of desulfation protocol and catalyst aging is also examined.

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