Exhaust gas purification system for internal combustion engine

摘要

An object of the present invention is to prevent an excessive temperature rise of a precatalyst in the case where the precatalyst is provided in the exhaust passage upstream of an exhaust gas purification apparatus and has a heat capacity smaller than that of the exhaust gas purification apparatus, and reducing agent is added from a reducing agent addition valve toward an upstream end surface of the precatalyst. According to the present invention, the reducing agent addition valve is located in such a way that the reducing agent added through it reaches the precatalyst in a liquid state. In the case where the level of activity of the precatalyst is higher than a specific level at the time when the addition of reducing agent through the reducing agent addition valve is performed so as to supply the reducing agent to the precatalyst and the exhaust gas purification apparatus, the reducing agent is added more intensively than in the case where the level of activity of the precatalyst is not higher than the specific level.