| 摘要 |
<p>A multi-zoned catalytic trap for conversion of NOx in an exhaust gas stream which emanates from an engine which is operated with periodic alternations between lean, and stoichiometric or rich, conditions. The catalytic trap comprises a first zone, a second zone and, optionally, one or more intermediate zones disposed between the first zone and the second zone. Each of the zones comprises a catalytic trap material coated on a refractory carrier member. In the first zone, the catalytic trap material comprises a refractory metal oxide support having dispersed thereon a palladium catalytic component in the amount of about 30 to about 300 g/ft3, a platinum catalytic component in the amount of 0 to about 100 g/ft3 and a rhodium catalytic component in the amount of 0 to about 10 g/ft3; and a NO¿x? sorbent comprising one or more basic oxygenated compounds of one or more alkaline earth metals and optionally, one or more basic oxygenated compounds of one or more alkali metals. In the second zone, the catalytic trap material comprises a refractory metal oxide support having dispersed thereon a palladium catalytic component in the amount of 0 to about 50 g/ft?3¿, a platinum catalytic component in the amount of about 10 to about 100 g/ft3 and a rhodium catalytic component in the amount of about 5 to about 20 g/ft3; and a NO¿x? sorbent comprising one or more basic oxygenated compounds of one or more metals selected from the group consisting of alkali metals and alkaline earth metals. In the optional zone(s), the catalytic trap material comprises a refractory metal oxide support having dispersed thereon a palladium catalytic component in the amount of about 25 to about 75 g/ft?3¿, a platinum catalytic component in the amount of about 5 to about 30 g/ft3 and a rhodium catalytic component in the amount of 0 to about 10 g/ft3; and a NO¿x? sorbent comprising one or more basic oxygenated compounds of one or more metals selected from the group consisting of alkali metals and alkaline earth metals.</p> |
