NOx catalyst for internal combustion engine exhaust and means of controlling its recovery from SOx poisoning when necessary

摘要

A storage-reduction type NOx catalyst (42) absorbs NOx when the exhaust air-fuel mixture is poor and releases NOx to form N2 using a reducing agent (17) when the air-fuel mixture is rich. When the point of recovery from SOx poisoning is reached, a reducing agent is supplied intermittently to release the SOx deposited and recover the catalyst whilst ensuring the catalyst is not overheated In addition, there are means of correcting the quantity of reducing agent used on the basis of a response time for the NOx catalyst temperature relative to the supply of reducing agent. The quantity of reducing agent is corrected by modifying the period during which the reducing agent is supplied to the NOx catalyst. The response time for the NOx catalyst temperature refers to the time between the supply of the reducing agent and the raising of the catalyst temperature as a result. The reducing agent is supplied intermittently, based on a catalyst temperature and the temperature of the exhaust gases passing through the catalyst. An Independent claim is also included for a process for operating such a device.