Patent ID: 7718150

Claim:
A lean NO x trap system for remediating a NO x emission in an exhaust system of a vehicle having an exhaust stream and capable of operation during one or more lean periods and one or more rich periods, the system comprising: a first trap connected to the exhaust system of the vehicle, the first trap having a first substrate supporting a first quantity of platinum and a first quantity of rhodium, the first quantity of rhodium including a zero amount; a second trap connected to the exhaust system of the vehicle, the second trap having a second substrate supporting a second quantity of platinum and a second quantity of rhodium; the first trap being positioned upstream of the second trap relative to a direction of the exhaust stream; the second quantity of rhodium being greater than or equal to the first quantity of rhodium; when compared to the first trap, the second trap having a higher overall NO x conversion at a first temperature and a lower overall NO x conversion at a second temperature greater than the first temperature.