Exhaust gas purification device of internal combustion engine

摘要

A catalyst ( 22 ) suitable for reduction of the NO_x in an exhaust gas by ammonia in the presence of excess oxygen is arranged in the exhaust passage ( 18, 21 ) of an internal combustion engine. An aqueous urea solution is fed through a flow control valve ( 33 ) to the inside of the exhaust passage ( 21 ) upstream of the catalyst ( 22 ). When the temperature of the catalyst ( 22 ) is low, a large amount of the aqueous urea solution is fed to make the urea contained in the aqueous urea solution be stored in the catalyst ( 22 ). When the engine is accelerated and the temperature of the catalyst ( 22 ) rises, ammonia is released at a little at a time from the inside of the catalyst ( 22 ) and the NO_x in the exhaust gas is reduced by the released ammonia.