Abstract: The present invention provides a thermally stable catalyst for treating automobile exhaust by-products is provided. The catalyst of the invention comprises a first section that includes a precious metal present in a first concentration and a second section that includes a precious metal present in a second concentration. The catalyst of the invention is characterized by a unique precious metal concentration profile in which the first concentration of the precious metal is lower than the second concentration of the precious metal. When placed with an automobile exhaust system, the second section is positioned downstream of the first section. The present invention also provides a lean NOx trap utilizing the unique precious metal concentration profile. The NOx trap is found to possess improved NOx conversion performance relative to a NOx trap with the same total amount of precious metal deposited uniformly over the volume of the trap.

Abstract: A mechanical apparatus including a combustion engine, a conduit for transporting an exhaust stream away from the engine, a first catalytic NOx storage and conversion region disposed along the conduit, and a second catalytic NOx storage and conversion region disposed along the conduit at a location downstream from the first catalytic NOx storage and conversion region is disclosed. Each of the first catalytic NOx storage and conversion region and the second catalytic NOx storage and conversion region includes at least one catalytic metal configured to convert NOx to NO2 when the engine is supplied a lean air/fuel mixture, and at least one NOx adsorbing compound configured to adsorb NO2 for storage when the engine is supplied a lean air/fuel mixture, and wherein the one of the first and the second catalytic NOx storage and conversion regions has a lower concentration of catalytic metal than the other of the first and second catalytic NOx storage and conversion regions.

Abstract: A method of desulfating a catalytic NOx storage and conversion device is disclosed, wherein the method includes determining an amount of sulfur stored in the catalytic NOx storage and conversion device; determining an interval for exposing the catalytic NOx storage and conversion device to a rich exhaust stream based upon the determined amount of sulfur stored, wherein the interval is longer for lower amounts of sulfur stored and shorter for higher amounts of sulfur stored; and exposing the catalytic NOx storage and conversion device to the rich exhaust stream for the determined interval.

Abstract: The present invention provides a catalyst for use in a NOx trap that has reduced NOx release during rich purges, increased NO conversion efficiency under stoichiometric conditions, and improved sulfur tolerance. The catalyst of this embodiment includes a precious metal, an oxygen storage component in contact with the precious metal, and a NOx storage material. The oxygen storage component in contact with the precious metal is present in an amount that provides sufficient oxygen storage capacity to reduce the NOx release from the NOx trap during rich purges to less than 20% of the NOx that is stored in the NOx trap across the operating temperature window of the NOx trap, increase the NOx conversion efficiency under stoichiometric conditions to a value greater than 70%, and increase the sulfur tolerance of the NOx trap.

Abstract: A method of desulfating a catalytic NOx storage and conversion device is disclosed, wherein the method includes determining an amount of sulfur stored in the catalytic NOx storage and conversion device; determining an interval for exposing the catalytic NOx storage and conversion device to a rich exhaust stream based upon the determined amount of sulfur stored, wherein the interval is longer for lower amounts of sulfur stored and shorter for higher amounts of sulfur stored; and exposing the catalytic NOx storage and conversion device to the rich exhaust stream for the determined interval.

Abstract: The present invention provides a thermally stable catalyst for treating automobile exhaust by-products is provided. The catalyst of the invention comprises a first section that includes a precious metal present in a first concentration and a second section that includes a precious metal present in a second concentration. The catalyst of the invention is characterized by a unique precious metal concentration profile in which the first concentration of the precious metal is lower than the second concentration of the precious metal. When placed with an automobile exhaust system, the second section is positioned downstream of the first section. The present invention also provides a lean NOx trap utilizing the unique precious metal concentration profile. The NOx trap is found to possess improved NO storage capacity upon thermal aging relative to a NOx trap with the same total amount of precious metal deposited uniformly over the volume of the trap.

Abstract: A mechanical apparatus including a combustion engine, a conduit for transporting an exhaust stream away from the engine, a first catalytic NOx storage and conversion region disposed along the conduit, and a second catalytic NOx storage and conversion region disposed along the conduit at a location downstream from the first catalytic NOx storage and conversion region is disclosed. Each of the first catalytic NOx storage and conversion region and the second catalytic NOx storage and conversion region includes at least one catalytic metal configured to convert NOx to NO2 when the engine is supplied a lean air/fuel mixture, and at least one NOx adsorbing compound configured to adsorb NO2 for storage when the engine is supplied a lean air/fuel mixture, and wherein the one of the first and the second catalytic NOx storage and conversion regions has a lower concentration of catalytic metal than the other of the first and second catalytic NOx storage and conversion regions.

Abstract: The present invention provides a catalyst for use in a NOx trap that has reduced NOx release during rich purges, increased NO conversion efficiency under stoichiometric conditions, and improved sulfur tolerance. The catalyst of this embodiment includes a precious metal, an oxygen storage component in contact with the precious metal, and a NOx storage material. The oxygen storage component in contact with the precious metal is present in an amount that provides sufficient oxygen storage capacity to reduce the NOx release from the NOx trap during rich purges to less than 20% of the NOx that is stored in the NOx trap across the operating temperature window of the NOx trap, increase the NOx conversion efficiency under stoichiometric conditions to a value greater than 70%, and increase the sulfur tolerance of the NOx trap.

Abstract: A method is described for controlling lean and rich operation of an internal combustion engine coupled to a lean NOx trap. In one example, the termination of the lean air-fuel mixture is based on an oxygen storage capacity and temperature of the NOx trap. In another example, the level and duration of rich air-fuel ratio purging operation is also controlled based on the oxygen storage capacity of the NOx trap.

Abstract: A method is described for controlling lean and rich operation of an internal combustion engine coupled to a lean NOx trap. In one example, the termination of the lean air-fuel mixture is based on an oxygen storage capacity of the NOx trap. In another example, the level and duration of rich air-fuel ratio purging operation is also controlled based on the oxygen storage capacity of the NOx trap.