| abstract |
In an internal combustion engine, a NOx selective reduction catalyst (15) is disposed in an engine exhaust passageway, and an oxidation catalyst (12) is disposed in the engine exhaust passageway upstream of the NOx selective reduction catalyst (15). At the starting of the engine, HC is fed to the oxidation catalyst (12) from a HC supply valve (28) and by the resultant oxidation reaction heat of HC, the NOx selective reduction catalyst (15) is heated. In this stage, the temperature of the NOx selective reduction catalyst (15) is raised to that falling in the HC desorption temperature range in which HC is desorbed from the NOx selective reduction catalyst (15). |