US Patent 11946428 Systems and methods for reducing aftertreatment system NOx emissions

A controller for an aftertreatment system coupled to an engine is configured to: in response to receiving an engine shutdown signal, determine an estimated amount of ammonia stored on a selective catalytic reduction (SCR) catalyst included in the aftertreatment system; in response to determining that the estimated amount of ammonia stored in the SCR catalyst is less than an ammonia storage threshold, cause flow of a heated gas towards the SCR catalyst; cause insertion of reductant into an exhaust gas flowing through the aftertreatment system; and in response to determining that the estimated amount of ammonia stored in the SCR catalyst is equal to or greater than the ammonia storage threshold, cause shutdown of the engine.