Patent ID: 8683784

Claim:
An exhaust purification system of an internal combustion engine, the exhaust purification system comprising: a hydrocarbon feed valve for feeding hydrocarbons arranged inside an engine exhaust passage; and an exhaust purification catalyst, downstream of the hydrocarbon feed valve, for reacting NO x contained in exhaust gas and hydrocarbons which are injected from the hydrocarbon feed valve and are partially oxidized, wherein a precious metal catalyst is carried on the exhaust purification catalyst, a basic layer is formed on the exhaust purification catalyst, a top coat layer comprised of a hydrocarbon partial oxidation catalyst is formed on a bottom coat layer comprised of the exhaust purification catalyst, and the exhaust purification catalyst has a property of: chemically reducing the NO x contained in the exhaust gas when hydrocarbons are injected from the hydrocarbon feed valve at predetermined feed intervals while maintaining an air-fuel ratio of an exhaust gas flowing into the exhaust purification catalyst lean, and of being increased in a storage amount of NO x contained in the exhaust gas when the feed intervals of the hydrocarbons are longer than the predetermined feed intervals, and at the time of engine operation, a first NO x purification method that injects hydrocarbons from the hydrocarbon feed valve at said predetermined feed intervals while maintaining the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst lean so as to remove the NO x contained in the exhaust gas and a second NO x purification method that switches the air-fuel ratio of the exhaust gas that flows to the exhaust purification catalyst from lean to rich by intervals longer than said predetermined feed intervals to remove the NO x are selectively used in accordance with an operating state of an engine.