Patent ID: 6216449
Filing Date: 2001-04-17
Classification: B01D,F01N,F02D,Y02T

Abstract:
A process for assessing performance of a bifunctional nitrogen oxide storage catalyst placed in an exhaust gas stream, which bifunctional catalyst stores both nitrogen oxide and oxygen, the process comprising:a) exposing the catalyst to an exhaust gas stream in an initial lean phase resulting from a lean air/fuel ratio, during which nitrogen oxides are stored;b) afterward exposing the catalyst to an exhaust gas stream in a rich phase resulting from a rich air/fuel ratio, during which nitrogen oxides are desorbed and converted, wherein the rich phase extends beyond a time required for complete desorption of the nitrogen oxides and until at least a portion of rich exhaust gas breaks through the catalyst;c) measuring a time interval .DELTA.t.sub.1 from a beginning of the rich phase until the breakthrough of rich exhaust gas through the catalyst;d) afterward exposing the nitrogen oxide storage catalyst to an exhaust gas stream in a lean phase resulting from a lean air/fuel ratio, during which nitrogen oxides are stored, wherein the lean phase extends at least until a portion of oxygen in the exhaust gas breaks through the catalyst;e) measuring a time interval .DELTA.t.sub.2 from a beginning of the lean phase until the breakthrough of at least a portion of oxygen through the catalyst;f) optionally repeating steps b) through e) over several cycles; andg) separately assessing the oxygen storage function of the catalyst, and the nitrogen oxide storage function of the catalyst, based on the measured time intervals .DELTA.t.sub.1 and .DELTA.t.sub.2.