Patent ID: 7877984

Claim:
A method for maintaining oxidation of NO to NO2 in an oxidation catalytic converter arranged in a vehicle comprising an internal combustion engine, which in operation emits exhaust gases to an exhaust gas aftertreatment system comprising the oxidation catalytic converter, comprising: delivering a predetermined quantity of hydrocarbon to the exhaust gas aftertreatment system over at least one predetermined time interval, the quantity of hydrocarbon being delivered to the exhaust gas aftertreatment system through a fragmented injection with a fragmentation frequency in an interval 0.01 to 0.5 Hz, an injection period in an interval 1 to 10 seconds , and the fragmented injection is at an opening frequency of about 10-100 Hz; and using a shorter injection period at a higher fragmentation frequency to substantially maintain oxidation of NO to NO2 in the exhaust gas aftertreatment system at a level that prevailed immediately prior to the time interval for the hydrocarbon injection.