A modified Y-type molecular sieve and its preparation method

Abstract

The invention discloses a modified Y-type molecular sieve and a preparation method thereof. The preparation method comprises: (1) carrying out ammonium salt ion exchange in an ammonium salt solution by using NaY zeolite as raw powder to achieve a Na2O weight content of less than 3.0%; (2) carrying out hydrothermal treatment on the Y molecular sieve obtained in the step (1); (3) carrying out sodium ion exchange on the Y molecular sieve obtained in the step (2) in a sodium salt solution; and (4) carrying out ammonium hexafluorosilicate dealuminzation silicon supplementing treatment on the Y molecular sieve obtained in the step (3), filtering, drying, and calcining to obtain the final modified Y-type molecular sieve. According to the present invention, with the method, the high-silicon and high-crystallinity modified Y molecular sieve being rich in mesoporous structure can be obtained.

Description

technical field [0001] The invention relates to a modified Y-type molecular sieve and a preparation method thereof, in particular to a modified Y-type molecular sieve rich in mesoporous structure with high silicon and high crystallinity and a preparation method thereof. Background technique [0002] Hydrocracking technology has many advantages such as strong feedstock adaptability, flexible production scheme, high selectivity of target products and good product quality, and plays an important role in the process of crude oil lightening and clean fuel production. For the hydrocracking process, its core is a hydrocracking catalyst, which is a typical dual-function catalyst, and its active center is composed of a hydrogenation center and a cracking center. The hydrogenation active center of the hydrocracking catalyst usually exists in the form of active metal sulfides of Group VI and Group VIII in the periodic table of elements, and the cracking active center of the hydrocracki...

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Problems solved by technology

[0003] Chinese patent CN96120016.2 discloses a Y-type molecular sieve with high silicon crystallinity and its preparation method. 4 NaY is used as the reaction raw material. First, ammonium hexafluorosilicate is used to dealuminate silicon, then perform hydrothermal treatment, and finally treat with aluminum salt solution. The obtained Y molecular sieve maintains a high degree of crystallinity while deeply dealuminated. However, The pore volume of the obtained modified Y molecular sieve should be low, which is not conducive to the contact and reaction of macromolecular reactants;

[0004] U.S. Patent No. 4,036,739 discloses a hydrocracking method, which discloses a method for modifying Y-type molecular sieves. At a temperature of 315 to 899 ° C, and at least 0.5 psi water vapor is contacted for a period of time to obtain modified Y The unit cell constant of the molecular sieve is 2.440~2.464nm; the treated Y molecular sieve is subjected to ammonium exchange to obtain an intermediate with a sodium content of less than 1%; then, a modified Y molecular sieve with a unit cell constant less than 2.440nm is obtained. The process is relatively harsh, so that the crystallinity of the obtained modified Y molecular sieve is severely damaged, and the crystallinity is low, which affects its performance

[0005] The existing Y-type molecular sieve modification technology has the problems of dealumination depth, silicon-aluminum ratio, secondary pore volume and crystallinity. When the dealumination depth increases, the silicon-aluminum ratio increases, and the secondary pore structure increases, the crystallinity tend to be more destructive; vice versa

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