Exhaust gas purification system for internal combustion engine and method for exhaust gas purification

An exhaust gas purification system for an internal combustion engine, comprising:

• a catalyst disposed in an exhaust passage of the internal combustion engine;
• a supplemental fuel valve that supplies supplemental fuel, used for the internal combustion engine, to the exhaust passage;
• and
• an electronic control unit comprising a program on a computer readable medium which when executed:
• determines a deceleration of the internal combustion engine based on a presence or absence of a main fuel injection;
• based on the determination of the deceleration, executes a particulate matter catalyst regeneration with a first target intake air volume;
• and
• based on the determination of the deceleration, executes a sulfur poisoning recovery with a second target intake air volume, the second target intake air volume being smaller than the first target intake air volume.