LNT-SCR system optimized for thermal gradient

摘要

In an exhaust aftertreatment system, two LNTs having differing compositions are configured in series downstream from an inline fuel reformer. The downstream LNT is adapted for desulfation at higher temperatures than the upstream LNT. During desulfation, the system develops temperature gradients with the temperatures increasing in the direction of exhaust flow. The ordering of the LNTs is designed utilize these gradients. In a preferred embodiment, the system also includes two SCR catalysts having different compositions. The SCR catalyst with a composition adapted to tolerate higher temperatures is located nearer the downstream end of the system.