INTERNAL COMBUSTION ENGINE EXHAUST AIR PURIFICATION DEVICE

摘要

In an internal combustion engine, an NO x selective reduction catalyst (15) is arranged in the engine exhaust passage, and the amount of deposition of the HC deposited at the NO x selective reduction catalyst (15) is estimated. When the estimated HC deposition amount exceeds a predetermined allowable deposition amount, the NO x selective reduction catalyst (15) is raised in temperature to make the deposited HC desorb from the NO x selective reduction catalyst (15), and thereby the NO x selective reduction catalyst (15) from HC poisoning is restored.