One aspect of the invention relates to a particulate filter useful in treating exhaust from a diesel-power vehicle. The particulate filter comprises filter elements for removing particulate matter and an ammonia SCR catalyst. Ammonia can be produced during regeneration of an NOx adsorbant. The adsorbant can be contained in a separate device upstream of the particulate filter or be incorporated within the particulate filter. Another aspect of the invention relates to a method of cleaning exhaust comprising passing the exhaust over an NOx adsorber to adsorb a portion of NOx from the exhaust; passing the exhaust through a particulate filter to remove particulate matter from the exhaust; and removing a further portion of NOx from the exhaust by reducing it with ammonia over an ammonia SCR catalyst. Preferably, a catalyst contained within the adsorbant provides NO 2 for continuously regenerating the particulate filter.
1. A method of cleaning a diesel-powered vehicle's exhaust containing NOx and particulate matter, comprising:
adsorbing a portion of the NOx on an adsorbant;
filtering particulate matter from the exhaust using a filter downstream of the adsorbant;
treating the exhaust upstream of the particulate filter with a catalyst that increases a ratio between NO 2 and NO in the exhaust at a point downstream of the adsorbant as compared to a ratio between NO 2 and NO in the exhaust upstream of the adsorbent; and
reducing a portion of the remaining NOx by reaction with ammonia over an ammonia SCR catalyst contained within or downstream of the filter;
wherein particulate matter is trapped on the particulate filter at approximately the same rate at which trapped particulate matter is oxidized by NO 2 .
2. The method of claim 1 , wherein the catalyst is combined with the adsorbant.
3. The method of claim 1 , further comprising intermittently regenerating the adsorbant, wherein ammonia produced during the regeneration process reacts to reduce NOx over the ammonia SCR catalyst.