Patent ID: 8707681

Claim:
An exhaust purification system of an internal combustion engine wherein an exhaust purification catalyst for reacting NO x contained in exhaust gas and reformed hydrocarbons to produce a reducing intermediate containing nitrogen and hydrocarbons is arranged in an engine exhaust passage, a precious metal catalyst is carried on an exhaust gas flow surface of the exhaust purification catalyst and a basic exhaust gas flow surface part is formed around the precious metal catalysts, the exhaust purification catalyst has a property of producing the reducing intermediate and reducing NO x contained in exhaust gas by a reducing action of the produced reducing intermediate if a concentration of hydrocarbons flowing into the exhaust purification catalyst is made to vibrate within a predetermined range of amplitude and within a predetermined range of period and has a property of being increased in storage amount of NO x which is contained in exhaust gas if a vibration period of the hydrocarbon concentration is made longer than said predetermined range, at the time of engine operation, to reduce NO x contained in the exhaust gas in the exhaust purification catalyst, the concentration of hydrocarbons flowing into the exhaust purification catalyst is made to vibrate within said predetermined range of amplitude and within said predetermined range of period, and, when a stored SO x should be released from the exhaust purification catalyst, an air-fuel ratio of the exhaust gas which flows into the exhaust purification catalyst is lowered to a targeted rich air-fuel ratio to make the reducing intermediate built up on the exhaust purification catalyst desorb in the form of ammonia and the desorbed ammonia is used to make the exhaust purification catalyst release the stored SO x .