Stabilized microporous crystalline material, the method of making the same, and the use for selective catalytic reduction of NOx

A method of selective catalytic reduction of nitrogen oxides in exhaust gas, said method comprising:

• at least partially contacting said exhaust gases with an article comprising a microporous crystalline material having building units of double-6-rings (d6r) and pore opening of 8-rings, wherein the material comprises a first metal chosen from alkali-earth group, rare-earth group, alkali group or mixtures thereof, and a second metal chosen from copper, iron or mixtures thereof,
• wherein the material has a molar silica to alumina ratio (SAR) from 3 to 12;
• and
• exhibits an NH3 adsorption capacity expressed as the molar NH3/Al ratio of 0.7 to 0.9.

A method of making a microporous crystalline material,

• said method comprising synthesizing a material having building units of double-6-rings (d6r) and pore opening of 8-rings, where the material has molar silica to alumina ratio (SAR) from 3 to 12, wherein the material exhibits an NH3 adsorption capacity expressed as the molar NH3/Al ratio of 0.7 to 0.9;
• mixing sources of sodium, potassium, alumina, silica, water and optionally an organic template to form a gel;
• heating the gel in a vessel at a temperature ranging from 80 to 200° C. to form a crystalline material;
• ammonium-exchanging said material;
• introducing a first metal chosen from alkali-earth group, rare-earth group, alkali group or mixtures thereof, and a second metal chosen from copper, iron or mixtures thereof, into said crystalline material by liquid-phase or solid ion-exchange, impregnation;
• and
• steaming said material at 400 to 800° C. in 1 to 100% steam for at least 0.1 hour.