Nh3 abatement with greater selectivity to n2

An emissions treatment system comprising:

• a SCR/ASC catalyst;
• and
• a component for introducing a nitrogenous reductant into the system upstream of the SCR/ASC catalyst,
• wherein the SCR/ASC catalyst comprises a first catalyst coating and a second catalyst coating,
• the first catalyst coating comprising a blend of 1) Pt on a support, and 2) a molecular sieve, wherein the molecular sieve is not a metal exchanged molecular sieve, wherein the molecular sieve is present in an amount of up to about 2 g/in3 relative to the weight of the first catalyst coating;
• and
• the second catalyst coating comprising an SCR catalyst,
• wherein the second catalyst coating does not comprise a platinum group metal, and
• wherein the first and second catalyst coatings are configured such that exhaust gas contacts the second catalyst coating before contacting the first catalyst coating.