| abstract |
A catalytic trap ( 10 ) for the treatment of exhaust generated by lean-burn or partial lean-burn engines is resistant to deactivation by high temperature, lean operating conditions aging. The catalytic trap ( 10 or 10 ′) comprises a carrier member ( 12 or 12/12 ′) on which is coated a catalytic trap material ( 20 ), optionally in discrete layers ( 20 a , 20 b ) comprising a NO x sorbent and a refractory metal oxide support on which is dispersed a palladium catalytic component in an amount of at least 25 g/ft 3 Pd up to about 300 g/ft 3 Pd. A platinum and/or a rhodium catalytic component may also be present. The NO x sorbent may be one or more basic oxygenated compounds of an alkali metal and/or an alkaline earth metal, e.g., of cesium and/or barium. A method of making includes applying the NO x sorbent by a post-dipping technique. A method of use includes alternating lean and stoichiometric or rich periods of operation and optionally oxidizing hydrocarbons in the exhaust prior to contacting the exhaust with the catalytic trap ( 10 ). |