Multi-zoned catalytic trap and methods of making and using the same

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, said multi-zoned catalytic trap comprising a discrete bottom layer coated on a refractive carrier member and a discrete top layer overlying the top layer, said bottom layer comprising a refractory metal oxide support having dispersed thereon a platinum catalytic component and a rhodium catalytic component and optionally a palladium catalytic component;

• said top layer comprising a refractory metal oxide support having dispersed thereon a palladium catalytic component and optionally a platinum and/or rhodium catalytic component, said multi-zoned catalytic trap further comprising a discrete first zone overlying a corresponding first section of the top layer and a discrete second zone overlying a corresponding second section of the top layer, said discrete first zone comprising a layer of a palladium catalytic component and a NOx 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 superimposed on top of the first section of the top layer and said second zone comprising a layer of a NOx 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 superimposed on top of the second section of the top layer.

A method of manufacturing 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, said catalytic trap comprising a first zone, a second zone and, optionally, one or more intermediate zone disposed between the first zone and the second zone, said first zone comprising a first catalytic trap material coated on a refractory carrier member, said second zone comprising a second catalytic trap material coated on a refractory carrier member and said optional intermediate zones comprising one or more optional intermediate catalytic trap materials coated on one or more refractory carrier members, which comprises the steps of:

• (A) preparing the first catalytic trap material by dispersing onto a refractory metal oxide support 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 NOx 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 by impregnating the support with a solution of a precursor palladium compound, a precursor platinum compound, a precursor rhodium compound and a precursor NOx sorbent compound in a liquid vehicle;
• (B) coating the impregnated support resulting from step (A) onto a refractory carrier member;
• (C) drying and thereafter heating the coated refractory carrier member resulting from step (B);
• (D) preparing the second catalytic trap material by dispersing onto a refractory metal oxide support a palladium catalytic component in the amount of 0 to about 50 g/ft3, 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 NOx sorbent comprising one or more basic oxygenated compounds of one or more metals selected from the group consisting of alkaline earth metals and alkali metals by impregnating the support with a solution of a precursor palladium compound, a precursor platinum compound, a precursor rhodium compound and a precursor NOx sorbent compound in a liquid vehicle;
• (E) coating the impregnated support resulting from step (D) onto a refractory carrier member;
• (F) drying and thereafter heating the coated refractory carrier member resulting from step (E);
• (G) preparing the optional intermediate catalytic trap materials by dispersing onto a refractory metal oxide support a palladium catalytic component in the amount of 25 to about 75 g/ft3, 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 NOx sorbent comprising one or more basic oxygenated compounds of one or more metals selected from the group consisting of alkaline earth metals and alkali metals by impregnating the support with a solution of a precursor palladium compound, a precursor platinum compound, a precursor rhodium compound and a precursor NOx sorbent compound in a liquid vehicle;
• (H) coating the optional impregnated support resulting from step (G) onto one or more refractory carrier members;
• and
• (I) drying and thereafter heating the one or more coated refractory carrier members resulting from step (I).

A method of manufacturing 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, said multi-zoned catalytic trap being present in the form of a discrete bottom layer coated on a refractive carrier member and a discrete top layer overlying the top layer, said bottom layer comprising a refractory metal oxide support having dispersed thereon a platinum catalytic component and a rhodium catalytic component and optionally a palladium catalytic component and a NOx sorbent, said top layer comprising a refractory metal oxide support having dispersed thereon a palladium catalytic component and optionally a platinum and/or rhodium catalytic component and a NOx sorbent, said multi-zoned catalytic trap further comprising a discrete first zone and a discrete second zone, said first zone comprising a layer of a palladium catalytic component and a NOx sorbent superimposed on a corresponding first section of the top layer and said second zone comprising a layer of a NOx sorbent superimposed on top of a corresponding second section of the top layer, which comprises the steps of:

• (1) dispersing onto a refractory metal oxide support a platinum catalytic component and a rhodium catalytic component and optionally a palladium catalytic component and a NOx 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 by impregnating the support with a solution of a precursor platinum compound, a precursor rhodium compound and optionally a precursor platinum compound and a precursor NOx sorbent compound in a liquid vehicle;
• (2) coating the impregnated support resulting from step (1) onto a refractory carrier member;
• (3) drying and thereafter heating the refractory carrier member resulting from step (2) to provide a refractory carrier member containing a bottom layer of a coating of the platinum catalytic component, the rhodium catalytic component, the optional palladium catalytic component and the NOx sorbent;
• (4) dispersing onto a refractory metal oxide support a palladium catalytic component and optionally a platinum and/or rhodium catalytic component, and a NOx 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 by impregnating the support with a solution of a precursor palladium compound and optionally a precursor platinum and/or precursor rhodium compound and a precursor NOx sorbent compound in a liquid vehicle;
• (5) coating the impregnated support resulting from step (4) onto the bottom layer of the coated refractory member resulting from step (3);
• (6) drying and thereafter heating the refractory carrier member resulting from step (5) to provide a refractory carrier member containing a top layer of the palladium catalytic component, the optional platinum and/or rhodium catalytic component and the NOx sorbent overlying said bottom layer;
• (7) post-impregnating the discrete first zone of the layered refractory carrier member resulting from step (6) with a solution of a precursor palladium compound and a precursor of a NOx 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 a liquid vehicle;
• (8) post-impregnating the discrete second zone of the layered refractory carrier member resulting from step (6) with a solution of a precursor of a NOx 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 a liquid vehicle;
• and
• (9) drying and heating the post-impregnated layered refractive carrier member resulting from step (8).