Modification method of small-grain NaY-type molecular sieve

Abstract

The invention discloses a modification method of a small-grain NaY-type molecular sieve. According to the invention, the NaY-type molecular sieve raw material with relatively high silica-to-alumina ratio, high crystallinity and good stability is adopted. Through sequential steps of alkali wash, ammonium exchange, hydrothermal treatment, and acid and ammonium salt mixed solution treatment, the obtained small-grain Y-type molecular sieve has relatively high SiO2 / A12O3 molar ratio as well as relatively high secondary pore proportion. Also, the stability of the Y-type molecular sieve is maintained. The molecular sieve has relatively high specific surface area and relatively high crystallinity. The Y-type molecular sieve provided by the invention is suitable to be used as a cracking component of a light oil hydrocracking catalyst. With the Y-type molecular sieve, the catalyst has the advantages of good activity, good heavy naphtha selectivity and excellent product quality.

Description

technical field [0001] The invention relates to a modification method of a NaY type molecular sieve, in particular to a modification method of a small grain NaY type molecular sieve. Background technique [0002] Y-type molecular sieve is the most common cracking active component in the field of heavy oil cracking. The grain size is generally about 1000nm, the grain size is relatively large, the channel is relatively long, the diffusion resistance is large, and it is difficult for macromolecules to enter the channel for reaction. The product after the reaction is also difficult to diffuse out, so its cracking activity and the selectivity of the target product are restricted. Compared with the conventional Y-type molecular sieve, the small-grained Y-type molecular sieve has a larger external surface area and more active centers on the external surface, which is conducive to improving the cracking capacity of macromolecular hydrocarbons, so it has more superior catalytic react...

AI Technical Summary

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.

Images