Exhaust gas purification system for internal combustion engine

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

• a filter provided in an exhaust passage of an internal combustion engine to trap particulate matter in exhaust gas;
• an oxidation catalyst provided in said exhaust passage upstream of said filter or supported on said filter;
• a fuel supplier that is configured to supply fuel to the exhaust gas upstream of said oxidation catalyst;
• and
• a controller comprising at least one processor configured to:
• determine, after fuel is supplied to a fuel tank of said internal combustion engine, a cetane number of said fuel used in the internal combustion engine after the supply of fuel;
• and
• perform a temperature raising process, which is a process of raising a temperature of said filter by heat of oxidation reaction of fuel in said oxidation catalyst, by supplying fuel to the exhaust gas through said fuel supplier when the temperature of the exhaust gas flowing into said oxidation catalyst exceeds a specific threshold temperature that is determined on the basis of the cetane number of the fuel, said threshold temperature being set lower when the cetane number of the fuel is low than when the cetane number of the fuel is high, wherein
• when a quantity of heat generated in said oxidation catalyst per unit time is smaller than a specific value while said temperature raising process is being performed, said controller suspends the temperature raising process in progress, and resumes said temperature raising process later on when the temperature of the exhaust gas flowing into said oxidation catalyst exceeds an updated threshold temperature higher than said specific threshold temperature.