Process for the preparation of zeolites having CHA structure

1. A process for the preparation of zeolites having CHA framework structure and a composition comprising the molar ratio (n SiO 2 ):X 2 O 3 , wherein X is a trivalent element, and wherein n is at least 10, the process comprising:

(i) preparation of an aqueous solution containing:

at least one source for X 2 O 3 , wherein X is selected from Al, B, Ga, and a mixture of two or more,

at least one source for SiO 2 ,

at least one organic structure directing agent (SDA) other than Tetramethylammonium hydroxide (TMAOH) as a template for the CHA structure, and

Tetramethylammonium hydroxide (TMAOH),

wherein the SDA or mixtures thereof are employed in such amounts that the aqueous solution in (i) exhibits a molar ratio of SDA:TMAOH in the range of 0.01 to 5;

(ii) hydrothermal crystallization of the aqueous solution according to (i);

wherein the aqueous solution of (i) contains copper in an amount less than 0.005 Cu:((n SiO 2 )+X 2 O 3 ) where n is at least 10.

2. The process of claim 1 , wherein the aqueous solution subjected to hydrothermal crystallization according to (ii) is free of alkali and/or earth alkali metals.

3. The process of claim 1 , wherein the structure directing agent comprises a 1-adamantyltrimethylammonium compound or a mixture of a 1-adamantyltrimethylammonium compound and a benzyltrimethylammonium compound.

4. The process of claim 1 , wherein the pH of the aqueous solution obtained in (i) is in the range of 10 to 14.

5. The process of claim 1 , wherein the ratio of SDA:TMAOH is in the range of 0.7 to 3.

6. The process of claim 1 , wherein the at least one source for SiO 2 and the at least one source for X 2 O 3 are employed in such amounts that the aqueous solution obtained according to (i) exhibits a molar ratio of water relative to the sum of (n X 2 O 3 ) and SiO 2 , relative to the structure directing agent (SDA), optionally the sum of SDAs, and TMAOH

( q H 2 O):[( n SiO 2 )+X 2 O 3 ]:( s SDA):( t TMAOH)

wherein q is at least 10, n is 10 to 1000, s is 0.025 to 0.1 and t is 0.01 to 0.1.

7. The process of claim 1 , wherein the aqueous solution obtained according to (i) has a OH−/Si ratio in the range of 0.1 to 0.5.

8. The process of claim 1 , additionally comprising

(iii) separating the zeolitic material from the suspension obtained according to (ii);

(iv) drying the zeolitic material, separated according to (iii), at a temperature in the range of from 100 to 150° C.;

(v) calcining the zeolitic material, dried according to (iv), at a temperature in the range of from 300 to 750° C.

9. A process for the preparation of zeolites having CHA framework structure and a composition comprising the molar ratio (n SiO 2 ):X 2 O 3 , wherein X is a trivalent element, and wherein n is at least 10, the process comprising:

(i) preparation of an aqueous solution containing:

at least one source for X 2 O 3 , wherein X is selected from Al, B, Ga, and a mixture of two or more,

at least one source for SiO 2 ,

at least one organic structure directing agent (SDA) other than Tetramethylammonium hydroxide (TMAOH) as a template for the CHA structure, and

Tetramethylammonium hydroxide (TMAOH),

wherein the SDA or mixtures thereof are employed in such amounts that the aqueous solution in (i) exhibits a molar ratio of SDA:TMAOH in the range of 0.01 to 5;

(ii) hydrothermal crystallization of the aqueous solution according to (i);

wherein the aqueous solution of (i) contains copper in an amount less than 0.005 Cu:((n SiO 2 )+X 2 O 3 ) where n is at least 10

wherein X comprises Al.