Patent ID: 8763370

Claim:
An exhaust purification system of an internal combustion engine, the exhaust purification system comprising: an engine exhaust passage; an exhaust purification catalyst for reacting NO x contained in exhaust gas and reformed hydrocarbons arranged in the engine exhaust passage, wherein precious metal catalysts are carried and a basic layer is formed on the exhaust purification catalyst; an electronic control unit, wherein the electronic control unit is configured to control a vibration of a concentration of hydrocarbons flowing into the exhaust purification catalyst within a predetermined range of amplitude and within a predetermined range of period, and is configured to control the vibration of the concentration of hydrocarbons for a period longer than the predetermined range of period, wherein when the electronic control unit controls the vibration of the concentration of hydrocarbons within the predetermined range of amplitude and within the predetermined range of period, a reducing intermediate containing nitrogen and hydrocarbons is produced on the precious metal catalysts and held on the basic layer, the NO x contained in the exhaust gas is chemically reduced by the reducing intermediate held on the basic layer in the exhaust purification catalyst, and the exhaust purification catalyst has a property of chemically reducing the NO x that is contained in the exhaust gas without storing,or storing a fine amount of nitrates in the basic layer, and when the electronic control unit controls the vibration of the concentration of hydrocarbons for a period longer than the predetermined range of period, the exhaust purification catalyst has a property of storing the NO x that is contained in the exhaust gas when an air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst is lean and releasing the stored NO x when the air-fuel ratio of the inflowing exhaust gas becomes rich, and the electronic control unit is configured to selectively control the vibration of the concentration of the hydrocarbons flowing into the exhaust purification catalyst in accordance with a sulfur poisoning of the exhaust purification catalyst.