Exhaust gas control apparatus for internal combustion engine

An exhaust gas control apparatus for an internal combustion engine, the exhaust gas control apparatus comprising:

• a NOx purification catalyst which is disposed in an exhaust passage of the internal combustion engine and is formed to carry a first catalyst metal on a first catalyst carrier;
• an oxidation catalyst which is disposed downstream of the NOx purification catalyst in the exhaust passage and is formed to carry second catalyst metals including a base metal on a second catalyst carrier;
• an air introduction apparatus that introduces air into the exhaust passage downstream of the NOx purification catalyst and upstream of the oxidation catalyst in the exhaust passage;
• a temperature detector that detects a temperature of the oxidation catalyst;
• and a controller that, when the temperature of the oxidation catalyst detected by the temperature detector is a predetermined temperature or lower, adjusts an air amount introduced into the exhaust passage by the air introduction apparatus to control an air-fuel ratio of the exhaust gas flowing into the oxidation catalyst to a more fuel lean air-fuel ratio than a stoichiometric air-fuel ratio, and
• when the temperature of the oxidation catalyst detected by the temperature detector exceeds the predetermined temperature, adjusts the air amount introduced into the exhaust passage by the air introduction apparatus to control the air-fuel ratio of the exhaust gas flowing into the oxidation catalyst to the stoichiometric air-fuel ratio.