Nitrous oxide removal catalysts for exhaust systems
A nitrous oxide (N 2 O) removal catalyst composite is provided, comprising a N 2 O removal catalytic material on a substrate, the catalytic material comprising a rhodium (Rh) component supported on a ceria-based support, wherein the catalyst composite has a H 2 -consumption peak of about 100° C. or less as measured by hydrogen temperature-programmed reduction (H 2 -TPR). Methods of making and using the same are also provided.
1. An emissions treatment system for treatment of an internal combustion engine exhaust stream including hydrocarbons, carbon monoxide, and nitrogen oxides, the emission treatment system comprising:
an exhaust conduit in fluid communication with the internal combustion engine via an exhaust manifold;
a treatment catalyst; and
a N 2 O removal catalyst composite comprising a N 2 O removal catalytic material on a substrate, the catalytic material comprising a rhodium (Rh) component supported on a ceria-based support, wherein the catalytic material has a H 2 -consumption peak of about 100° C. or less as measured by hydrogen temperature-programmed reduction (H 2 -TPR) and is effective to decompose at least a portion of nitrous oxide (N 2 O) in the exhaust stream to nitrogen (N 2 ) and oxygen (O 2 ) or to reduce at least a portion of the N 2 O to N 2 and water, N 2 and carbon dioxide (CO 2 ), or N 2 , water, and CO 2 under conditions of the exhaust stream.
2. The emissions treatment system of claim 1 , wherein the treatment catalyst comprises a precious metal on a high surface area refractory metal oxide support that is effective to oxidize hydrocarbons and/or carbon monoxide under conditions of the exhaust stream.
3. The emissions treatment system of claim 2 , wherein the treatment catalyst comprises a nitrogen oxides treatment catalyst selected from the group consisting of a three-way conversion (TWC) catalyst, a lean NOx trap (LNT), and a Selective Catalytic Reduction (SCR) catalyst.
4. The emissions treatment system of claim 3 , wherein the N 2 O removal catalyst composite is located downstream of the nitrogen oxides treatment catalyst.
5. The emissions treatment system of claim 3 , wherein the system is zoned and the nitrogen oxides treatment catalyst is in a front, upstream zone and the N 2 O removal catalyst composite is in a back, downstream zone.
6. The emissions treatment system of claim 3 , wherein the system is layered and the nitrogen oxides treatment catalyst is in an outer layer and the N 2 O removal catalytic material of the catalyst composite is in an inner layer.
7. The emissions treatment system of claim 3 , wherein the system is layered and the nitrogen oxides treatment catalyst is in an inner layer and the N 2 O removal catalytic material of the N 2 O catalyst composite is in an outer layer.
8. A method for treating exhaust gases comprising contacting a gaseous stream comprising hydrocarbons, carbon monoxide, and nitrogen oxides with a N 2 O removal catalyst composite comprising a N 2 O removal catalytic material on a substrate, the catalytic material comprising a rhodium (Rh) component supported on a ceria-based support, wherein the catalytic material has a H 2 -consumption peak of about 100° C. or less as measured by hydrogen temperature-programmed reduction (H 2 -TPR) and is effective to decompose at least a portion of nitrous oxide (N 2 O) in the exhaust stream to nitrogen (N 2 ) and oxygen (O 2 ) or to reduce at least a portion of the N 2 O to N 2 and water, N 2 and carbon dioxide (CO 2 ), or N 2 , water, and CO 2 under conditions of the exhaust stream.
9. The method of claim 8 , wherein N 2 O removal activity of the catalytic material after aging at 750° C. for 20 hours with 10 weight % water is higher than N 2 O removal activity of fresh catalytic material.