Small-grain Y-type molecular sieve and preparation method thereof

Abstract

The invention discloses a small-grain Y type molecular sieve and a preparation method thereof. The small-grain Y type molecular sieve has the following properties: the mol ratio of SiO2 / A12O3 is more than 10 and less than 40; average grain diameter is 200 to 700 nm; relative crystallinity is above 100%; lattice constant is 2.430 to 2.450 nm; specific surface area is 850 to 1000 m2 / g; pore volume is 0.50 to 0.80 mL / g; the pore volume of secondary pores with a diameter of 1.7 to 10 nm is more than 50% of the total pore volume; and Na2O content is no more than 0.15 wt%. According to the preparation method, an NaY molecular sieve with a high Si / Al ratio, high crystallinity and good stability is used as a raw material, and caustic washing, ammonium exchange, hydrothermal treatment and treatment with a mixed solution of acid and ammonium salt are successively carried out so as to obtain the small-grain Y type molecular sieve. The small-grain Y type molecular sieve prepared in the invention is applicable as a cracking component of a light oil type hydrocracking catalyst and enables the catalyst to have good activity, heavy naphtha selectivity and excellent product nature.

Description

technical field [0001] The invention relates to a Y-type molecular sieve and a preparation method thereof, in particular to a small-grain Y-type molecular sieve and a preparation method thereof. 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, ...

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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

[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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