EXHAUST PURIFICATION APPARATUS FOR INTERNAL COMBUSTION ENGINE

摘要

In an internal combustion engine, inside of an engine exhaust passage, a hydrocarbon feed valve (15) and an exhaust treatment catalyst (13) are arranged. On a substrate (45) of the exhaust treatment catalyst (13), a coat layer comprised of at least two layers of a top coat layer (46) and a bottom coat layer (47) is formed. The top coat layer (46) is comprised of an exhaust purification catalyst for reacting NO x contained in exhaust gas and reformed hydrocarbons, while the bottom coat layer (47) is comprised of an NO x absorption catalyst. The concentration of hydrocarbons which flows into the exhaust treatment catalyst (13) is made to vibrate within a predetermined range of amplitude and within a predetermined range of period. Due to this, NO x contained in exhaust gas and NO x desorbed from the NO x absorption catalyst (47) are reduced in the exhaust purification catalyst (46).