| 摘要 |
The present invention relates to a process for the preparation of zeolites having CHA framework structure and a composition comprising the molar ratio (n SiO2):X2O3, 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 X2O3, wherein X is selected from Al, B, Ga, and a mixture of two or more, and at least one source for SiO2, at least one organic structure directing agent (SDA) other than Tetramethylammonium hydroxide (TMAOH), acting 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 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 YO2)+X2O3) where n is in the range of 10 to 50.
;The present invention also relates to the zeolitic materials obtainable and/or obtained by this process as well as to a zeolitic material as such, having framework structure CHA, having a composition comprising the molar ratio (n SiO2):X2O3, wherein X is a trivalent element and n is at least 10, and wherein the crystal size, as determined from Scanning Electron Microscopy, is greater than 1 micrometer and wherein the chabazite framework is phase-pure having an impurity of other zeolitic frameworks, such as RUT as determined by X-ray Diffraction, of less than 5%. |
