High ammonia storage capacity SCR catalysts

A process for preparing a catalyst for selective catalytic reduction of nitrogen oxide comprising:

• (1) providing a substrate comprising an inlet end, an outlet end, a substrate axial length extending from the inlet end to the outlet end, and a plurality of passages defined by internal walls of the substrate extending therethrough;
• (2) preparing a first mixture comprising water and a 12-membered ring pore zeolitic material comprising a first metal which is one or more of copper and iron, wherein the 12-membered ring pore zeolitic material comprises the first metal in an amount of z1 weight-%, calculated as the weight of the first metal, calculated as CuO and Fe2O3, divided by the weight of the 12-membered ring pore zeolitic material comprising the first metal;
• (3) disposing the first mixture obtained in (2) on the surface of the internal walls of the substrate provided in (1), over x % of the substrate axial length from the inlet end toward the outlet end of the substrate, wherein x ranges from 10 to 75;
• (4) drying the mixture-treated substrate obtained in (3), obtaining the substrate having a first coating disposed thereon;
• optionally calcining;
• (5) preparing a second mixture comprising water and a 8-membered ring pore zeolitic material comprising a second metal which is one or more of copper and iron, wherein the 8-membered ring pore zeolitic material comprises the second metal in an amount of z2 weight-%, calculated as the weight of the second metal, calculated as CuO and Fe2O3, divided by the weight of the 8-membered ring pore zeolitic material comprising the second metal;
• (6) disposing the second mixture obtained in (5) on the substrate having a first coating disposed thereon obtained in (4) over y % of the substrate axial length from the outlet end toward the inlet end of the substrate, wherein y ranges from 25 to 90;
• (7) drying the mixture-treated substrate obtained in (6), obtaining the substrate having the first coating and a second coating disposed thereon;
• and
• (8) calcining the substrate having the first coating and the second coating disposed thereon obtained in (7), obtaining the catalyst;
• wherein the ratio z1:z2 ranges from 0.5:1 to 0.95:1.

A catalyst for selective catalytic reduction of nitrogen oxide comprising:

• a substrate comprising an inlet end, an outlet end, a substrate axial length extending from the inlet end to the outlet end, and a plurality of passages defined by internal walls of the substrate extending therethrough, and
• a coating disposed on the surface of the internal walls of the substrate, which surface defines the interface between the internal walls and the passages,
• wherein the coating comprising a 12-membered ring pore zeolitic material comprising a first metal which is one or more of copper and iron, and the 12-membered ring pore zeolitic material comprises the first metal in an amount of z weight-%, calculated as the weight of the first metal, calculated as CuO and Fe2O3, divided by the weight of the 12-membered ring pore zeolitic material comprising the first metal,
• wherein the coating further comprises a 10-membered ring pore zeolitic material comprising a second metal which is one or more of copper and iron, wherein the 10-membered ring pore zeolitic material comprises the second metal in an amount of y weight-%, calculated as the weight of the second metal, calculated as CuO and Fe2O3, divided by the weight of the 10-membered ring pore zeolitic material comprising the second metal;
• and
• wherein y ranges from 0.5 to 9 and y<z.