ASC with platinum group metal in multiple layers

1. A catalytic article for treating an exhaust gas stream containing particulate matter, hydrocarbons, CO, and ammonia, the article comprising:

a. a substrate having an inlet end and an outlet end defining an axial length;

b. a first catalyst coating including: 1) a platinum group metal distributed on a molecular sieve, and 2) a base metal distributed on a molecular sieve;

c. a second catalyst coating including: 1) a platinum group metal distributed on a molecular sieve, and 2) a base metal distributed on a molecular sieve,

wherein the first coating includes a higher platinum group metal loading than the second coating.

2. The catalytic article of claim 1 , wherein

a. the first catalyst coating covers the entire axial length of the substrate; and

b. the second catalyst coating covers the entire axial length of the substrate and overlaps the first catalyst coating.

3. The catalytic article of claim 1 , wherein the molecular sieve in the first and/or second coating comprises a zeolite.

4. The catalytic article of claim 1 , wherein the base metal in the first and/or second coating comprises copper, iron, or a combination thereof.

5. The catalytic article of claim 1 , wherein the first coating and second coating each comprise platinum distributed on a zeolite and copper distributed on a zeolite.

6. The catalytic article of claim 1 , wherein first coating comprises a platinum group metal loading of about 0 g/ft 3 to about 10 g/ft 3 ; or about 1 g/ft 3 to about 5 g/ft 3 .

7. The catalytic article of claim 1 , wherein the second coating comprises a platinum group metal of about 0 g/ft 3 to about 5 g/ft 3 ; or about 1 g/ft 3 to about 3 g/ft 3 .

8. The catalytic article of claim 1 , wherein the weight ratio of platinum group metal in the first coating to the platinum group metal in the second coating is from about 20:1 to about 1:1; about 10:1 to about 1:1; about 6:1 to about 1:1; about 3:1 to about 1:1; or about 3:0.5 to about 1:1.

9. The catalyst article of claim 1 , wherein the substrate comprises an extruded SCR.

10. An emissions treatment system comprising:

a. a diesel engine emitting an exhaust stream including particulate matter, NOx, and carbon monoxide;

b. an SCR catalyst;

c. a catalytic article (“the ASC”) downstream of the SCR catalyst, the catalytic article comprising:

i. a substrate having an inlet end and an outlet end defining an axial length;

ii. a first catalyst coating including: 1) a platinum group metal distributed on a molecular sieve, and 2) a base metal distributed on a molecular sieve;

iii. a second catalyst coating including: 1) a platinum group metal distributed on a molecular sieve, and 2) a base metal distributed on a molecular sieve.

11. The system of claim 10 , wherein the SCR catalyst is close-coupled with the ASC.

12. The system of claim 10 , wherein the SCR catalyst and the ASC catalyst are located on a single substrate, and the SCR catalyst is located on an inlet side of the substrate and the ASC catalyst is located on the outlet side of the substrate.

13. A method of reducing emissions from an exhaust stream, comprising contacting the exhaust stream with the catalyst article of claim 1 .

14. A catalytic article for treating an exhaust gas stream containing particulate matter, hydrocarbons, CO, and ammonia, the article comprising:

a. a substrate having an inlet end and an outlet end defining an axial length;

b. a first catalyst coating including: 1) a platinum group metal distributed on a molecular sieve, and 2) a base metal distributed on a molecular sieve;

c. a second catalyst coating including: 1) a platinum group metal distributed on a molecular sieve, and 2) a base metal distributed on a molecular sieve,

wherein the substrate comprises an extruded SCR.