Zeolitic material having framework type CHA and comprising a transition metal and one or more of potassium and cesium
A zeolitic material having framework type CHA, comprising a transition metal M and an alkali metal A, and having a framework structure comprising a tetravalent element Y, a trivalent element X and O, wherein the transition metal M is a transition I metal of groups 7 to 12 of the periodic table, A is one or more of K and Cs, Y is one or more of Si, Ge, Ti, Sn and Zr, and X is one or more of Al, B, Ga and In. A process for preparing such a zeolitic material. Use of such a zeolitic material.
1. A zeolitic material having framework type CHA, comprising a transition metal M and an alkali metal A, and having a framework structure comprising a tetravalent element Y, and a trivalent element X and O,
wherein the transition metal M is a transition metal of groups 7 to 12 of a periodic table, A is one or more of K and Cs, Y is Si, and X is Al;
wherein M comprises Cu;
wherein the zeolitic material having framework type CHA further comprises Na.
2. The zeolitic material of claim 1 , comprising M in an amount in a range of from 0.5 to 7.5 weight-%, calculated as elemental M and based on a total weight of the zeolitic material, and wherein M further comprises Fe.
3. The zeolitic material of claim 1 , comprising A in an amount in a range of from 0.05 to 5 weight-%, calculated as elemental A and based on a total weight of the zeolitic material.
4. The zeolitic material of claim 1 , wherein in the framework structure, a molar ratio of Y relative to X, calculated as YO 2 :X 2 O 3 , is in a range of from 3:1 to 20:1.
5. The zeolitic material of claim 1 , wherein at least 98 weight-% of the zeolitic material consist of M, A, Y, X, O, H, and Na, and wherein at least 98 weight-% of the framework structure consist of Y, X, O, and H.
6. The zeolitic material of claim 1 , having one or more of the following characteristics:
a total amount of acid sites in a range of from 2.0 to 3.2 mmol/g, wherein the total amount of acid sites is defined as a total molar amount of desorbed ammonia per mass of the zeolitic material determined according to a temperature programmed desorption of ammonia; wherein the zeolitic material has an amount of medium acid sites in a range of from 1.0 to 1.7 mmol/g, wherein the amount of medium acid sites is defined as an amount of desorbed ammonia per mass of the zeolitic material determined according to the temperature programmed desorption of ammonia in a temperature range of from 250 to 450° C.;
a peak having a maximum in a range of from 210 to 205 nm, determined according to UV-Vis spectroscopy; and
a peak having a maximum in a range of from 1,945 to 1,950 cm −1 , a peak having a maximum in a range of from 2,245 to 2,250 cm −1 , a peak having a maximum in a range of from 1,925 to 1,930 cm −1 , a peak having a maximum in a range of from 1,870 to 1,880 cm −1 , and a peak having a maximum in a range of from 1,805 to 1,810 cm −1 , determined according to NO adsorption via FT-IR at a pressure of 1,000 Pa.
7. A process for preparing the zeolitic material according to claim 1 , the process comprising
(i) providing a zeolitic material having framework type CHA in its ammonium form, the zeolitic material comprising an alkali metal A, and having a framework structure comprising a tetravalent element Y, and a trivalent element X and O, wherein A is one or more of K and Cs, Y is one or more of Si, and X is Al;
wherein M comprises Cu;
wherein the zeolitic material provided having framework type CHA further comprises Na;
(ii) subjecting the zeolitic material having framework type CHA in its ammonium form to ion exchange conditions, comprising bringing the zeolitic material having framework type CHA in its ammonium form in contact with a solution comprising ions of a transition metal M of groups 7 to 12 of the periodic table, obtaining a mixture comprising a zeolitic material having framework type CHA, comprising a transition metal M and an alkali metal A, and having a framework structure comprising a tetravalent element Y, and a trivalent element X and O; and
(iii) separating the zeolitic material having framework type CHA from the mixture.
8. The process of claim 7 , wherein the providing a zeolitic material having framework type CHA in its ammonium form comprises:
(i.1) preparing a synthesis mixture comprising water, a source of Y, a source of X, and a source of A;
(i.2) subjecting the synthesis mixture to hydrothermal crystallization conditions comprising heating the synthesis mixture to a temperature in a range of from 150 to 200° C. and keeping the synthesis mixture at a temperature in the range of from 150 to 200° C. under autogenous pressure, obtaining a mother liquor comprising a zeolitic material having framework type CHA which comprises A;
(i.3) separating the zeolitic material obtained from (i.2) from the mother liquor;
(i.4) subjecting the zeolitic material obtained from (i.3) to ion exchange conditions, comprising bringing a solution comprising ammonium ions in contact with the zeolitic material obtained from (i.3), obtaining a zeolitic material having framework type CHA in its ammonium form.
9. The process of claim 8 , wherein Y is Si and the source of Y comprises one or more of silica and a silicate, wherein X is Al and the source of X comprises one or more of alumina and an aluminum salt, and wherein the source of A comprises one or more of a halide of A, a nitrate of A, and a hydroxide of A.
10. The process of claim 8 , wherein the synthesis mixture prepared further comprises a seed crystal material comprising a zeolitic material having framework type CHA.
11. The process of claim 8 , wherein the solution comprising ammonium ions according to (i.4) has an ammonium concentration in the range of from 1 to 5 mol/l.
12. The process of claim 7 , wherein the solution comprising ions of a transition metal M is an aqueous solution comprising a dissolved salt of the transition metal M.
13. The process of claim 7 , further comprising
(iv) calcining the zeolitic material obtained from (iii), obtaining the zeolitic material having framework type CHA, comprising a transition metal M and an alkali metal A, and having a framework structure comprising a tetravalent element Y, and a trivalent element X and O.
14. A zeolitic material obtained by the process according to claim 7 .
15. A catalyst, comprising the zeolitic material according to claim 1 .