A kind of beta/mcm‑49 composite molecular sieve with core-shell structure and preparation method thereof

Abstract

The invention discloses a Beta / MCM-49 composite molecular sieve with a core-shell structure and a preparation method thereof. The Beta molecular sieve is taken as the core phase, and the MCM-49 molecular sieve is the shell layer. The size of the core phase is 0.3 to 3.0 [mu]m, and the preferable size is 0.7 to 2.0 [mu]m. The thickness of the shell layer is 0.1 to 6.0 [mu]m, and the preferable thickness is 0.3 to 5.0 [mu]m. The shell layer accounts for 35 to 90 % of the total weight of composite molecular sieve, and the preferable content of shell layer is 50 to 80%. The preparation method comprises the following steps: subjecting Beta molecular sieve to surface plasma modification, and then taking the modified Beta molecular sieve as the crystal nucleus to prepare the Beta / MCM-49 composite molecular sieve. The composite molecular sieve has a good core-shell cladding form and has a good application prospect in alkylation reaction between alkene and benzene.

Description

technical field [0001] The invention belongs to the field of preparation of inorganic materials, and in particular relates to a Beta / MCM-49 composite molecular sieve with a core-shell structure and a preparation method thereof. Background technique [0002] The topological type of MCM-49 molecular sieve is MWW, which belongs to the same type of molecular sieve material as MCM-22. MCM-49 and Beta molecular sieves are widely used in the production of cumene by alkylation of propylene and benzene. Compared with MCM-22 molecular sieve, MCM-49 has relatively good catalytic performance in the alkylation reaction of propylene and benzene, but they also have unique reaction advantages. Since MCM-49 and Beta molecular sieves have different catalytic properties, if the two molecular sieves are organically compounded, and the composite crystal is endowed with reasonable acid distribution and good shape selectivity, it can make full use of the selectivity of MCM-49 molecular sieve. Du...

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Problems solved by technology

The degree of compounding of the composite molecular sieve obtained by this method is not easy to control, and a large amount of Beta and Y type molecular sieves do not form a core-shell structure

[0006] The preparation of the above-mentioned composite molecular sieves is basically the improvement of the two-step crystallization method for synthesizing composite molecular sieves with a core-shell structure by means of chemical treatment, and there are still various deficiencies.

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