Exhaust gas control apparatus for internal combustion engine

摘要

A SO x trap catalyst 12, an oxidation catalyst 13, a particulate filter 14, an aqueous urea supply valve 17, and a NO x selective reduction catalyst 16 are arranged in order from upstream to downstream in an engine exhaust passage. It is determined whether a discharge concentration of hydrogen sulfide H 2 S will become equal to or greater than a preset maximum concentration DNO when SO x is released from the SO x trap catalyst 12. If it is estimated that the discharge concentration of the hydrogen sulfide H 2 S will become equal to or greater than the maximum concentration DNO when SO x is released, an adsorbed ammonia amount adsorbed on the NO x selective reduction catalyst 16 is reduced before SO x is released so that the discharge concentration of the hydrogen sulfide H 2 S is less than the maximum concentration DNO when SO x is released.