Method for synthesizing flaky SAPO-34

Abstract

A method for synthesizing flaky SAPO-34 comprises the following steps: carrying out reduced pressure distillation on an SAPO-34 crystallization mother liquor, evaporating away a part of water, addingan aluminum source, a phosphorus source, a silicon source and fluoride, uniformly dispersing the added substances, adding the obtained solution into a kettle, and crystallizing the solution to obtaina crystal nucleus solution; sequentially adding the aluminum source, the silicon source, an organic amine template and the phosphorus source to deionized water, and fully dispersing the added substances to form an initial gel; and adding a crystal nucleus solution to the initial gel, uniformly dispersing the initial gel, adding the obtained solution to a high pressure reactor, crystallizing the solution, and centrifuging, washing, drying and calcining obtained crystals to obtain flaky SAPO-34 raw powder. The method effectively prolongs the MTO catalysis life of the SAPO-34 molecular sieve, andreuses a large amount of the crystallization mother liquor produced in the production process of the SAPO-34 molecular sieve.

Description

technical field [0001] The invention belongs to a method for synthesizing SAPO-34, in particular to a method for synthesizing flake-shaped SAPO-34 molecular sieves. Background technique [0002] In 1982, UCC developed a new class of phosphorus-containing molecular sieves——silicoaluminophosphate molecular sieves (SAPO), among which SAPO-34 showed good reactivity and ethylene-propylene selectivity to MTO. However, due to the rapid coking and deactivation of SAPO-34 molecular sieve in the MTO reaction, its application is greatly limited. By controlling the silicon distribution and silicon content of the SAPO-34 molecular sieve, the acid density and acid strength can be adjusted, and the traditional cubic block shape of SAPO-34 can be changed to form a stacked sheet-like layered shape, which is conducive to the rapid diffusion of the reaction product. Thereby improving the anti-coking ability of the catalyst. [0003] SAPO-34 molecular sieves are generally prepared by conventi...

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Problems solved by technology

[0004] In recent years, counterparts at home and abroad have conducted a lot of research on the reuse of crystallization mother liquor, but it is almost impossible to achieve zero discharge. If the mother liquor is directly reused in industry, on the one hand, the product performance will not be guaranteed, and on the other hand, it will not be able to achieve complete circulation. Some of them need to be discharged, but the mother liquor cannot be completely solved fundamentally.

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