Catalyst composition for use in a lean NOx trap and method of using

A lean NOx trap composition comprising:

• a support material;
• about 0.1 to about 10% by weight of washcoat of a ruthenium catalyst wherein the ruthenium catalyst is free of other precious metals;
• and
• about 5 to about 50% by weight of a NOx absorbent material comprising an alkaline earth metal;
• wherein the lean NOx trap composition has a storage efficiency of at least 70% at a temperature in a range of from about 400° C. to about 500° C., and a conversion efficiency of at least 50% at a temperature in a range of from about 300° C. to about 450° C.

A method of removing harmful gases from an automobile exhaust containing NOx, CO, and hydrocarbons, the method comprising:

• contacting a lean NOx trap composition with a first exhaust gas mixture, the first exhaust gas mixture comprising exhaust gases from an internal combustion engine operating in a fuel-lean condition, the lean NOx trap composition comprising:
• a support material;
• a ruthenium catalyst wherein the ruthenium catalyst is free of other precious metals;
• and
• a NOx absorbent material comprising an alkaline earth metal;
• wherein the lean NOx trap composition has a storage efficiency of at least 70% at a temperature in a range of from about 400° C. to about 500° C., and a conversion efficiency of at least 50% at a temperature in a range of from about 300° C. to about 450° C.;
• and
• contacting the lean NOx trap composition with a second exhaust mixture, the second exhaust gas mixture comprising exhaust gases from the internal combustion engine operating in a fuel-rich condition.