Method for preparing small-grain Y-type molecular sieve

Abstract

The invention discloses a preparation method of a small-grain Y-type molecular sieve. The method adopts NaY type molecular sieve raw material with high silicon-aluminum ratio, high crystallinity and good stability, and sequentially undergoes alkali washing, ammonium exchange, dealumination of silicon, hydrothermal treatment, and treatment with a mixed solution of acid and ammonium salt to obtain The small-grain Y-type molecular sieves obtained higher SiO 2 / A1 2 o 3 While the molar ratio is high, the proportion of secondary pores is high, and the stability of the Y-type molecular sieve is maintained. The molecular sieve has a high specific surface area and a high crystallinity. The Y-type molecular sieve obtained by the invention is suitable as a cracking component of a hydrocracking catalyst for medium oil, and can make the catalyst have good activity, medium oil selectivity and excellent product properties.

Description

technical field [0001] The invention relates to a preparation method of a Y-type molecular sieve, in particular to a preparation method of a small-grain Y-type molecular sieve. Background technique [0002] Y-type molecular sieve is currently the most common cracking active component in the field of heavy oil cracking. The crystal grain is generally about 1000nm. After the reaction, the product is also difficult to diffuse out, so its cracking activity and selectivity of the target product are restricted. Compared with conventional Y-type molecular sieves, small-grain Y-type molecular sieves have a larger outer surface area and more active centers on the outer surface, which is conducive to improving the cracking capacity of macromolecular hydrocarbons, and thus has superior catalytic performance. At the same time, reducing the grain size of the Y-type molecular sieve can also improve the utilization rate of active sites on the inner surface. In general, the diffusion of r...

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Problems solved by technology

[0004] The method for preparing fine-grained Y-type molecular sieves proposed in CN1081425A is to precrystallize the NaY synthesis solution at 80°C to 180°C for 1 to 10 hours, then add the directing agent after cooling to room temperature, and then add the directing agent at 80°C to 100°C. Continue to crystallize for 5 to 25 hours, the process steps are more complicated and difficult to control, and the hydrothermal stability of the fine-grained Y-type molecular sieve obtained is poor

CN1382632A discloses a super-stabilizing method of small-grain Y-type zeolite, which is obtained by contacting the dry gas of silicon tetrachloride with small-grain NaY zeolite and washing it. The stability is poor, and the inventive method adopts gas-phase dealumination to supplement silicon to process molecular sieves, which makes the thermal and hydrothermal stability of the product worse, and the activity is low

[0014] At present, due to the poor hydrothermal stability and unstable structure of small-grain NaY molecular sieves, small-grain Y-type molecular sieves with complete structure, high crystallinity and many secondary pores cannot be obtained after subsequent modification.

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