ZSM-5/silicalite-1 core-shell molecular sieve for shell layer with oriented epitaxial intergrowth

Abstract

The invention relates to a ZSM-5 / silicalite-1 core-shell molecular sieve for a shell layer with oriented epitaxial intergrowth. The ZSM-5 / silicalite-1 core-shell molecular sieve mainly solves the disadvantage of waste of using raw materials and a template agent of the shell layer due to multiple repeated growth for forming a compact shell layer in a conventional core-shell molecular sieve preparation technology; meanwhile, the ZSM-5 / silicalite-1 core-shell molecular sieve solves the problems of poor mechanical strength of the shell layer and poor activity and stability of a catalyst caused by the phenomenons of non-epitaxial intergrowth, non-oriented growth, nonuniformity and the like of the shell layer. According to the invention, after pretreatment of a core-phase zeolite material with an alkalescent aqueous solution, the core-shell molecular sieve containing the compact shell layer with epitaxial intergrowth is prepared in a molecular sieve crystallization system of the shell layer under the condition of proper reaction; the core-shell molecular sieve is effectively applied in shape-selective disproportination of aromatic hydrocarbon, shape-selective transalkylation and shape-selective methylation reaction so as to generate a large number of useful paraxylene isomers; and through the allocation of composition of a core and a shell, the catalyst has the characteristics of high catalytic activity, large processing amount of the aromatic hydrocarbon, high mechanical strength of integration, low application loss and high selectivity to paraxylene products, and can be applied in industrial production with higher efficiency.

Description

technical field [0001] The invention relates to a ZSM-5 / silicalite-1 core-shell molecular sieve with oriented epitaxial intergrowth of the shell layer. Background technique [0002] In the traditional toluene disproportionation or alkylation reaction process, the products obtained on the ZSM-5 molecular sieve catalyst with mesoporous channels (10-membered oxygen ring) are usually only mixed xylenes composed of thermodynamic equilibrium, and the para-isomers with high added value are only a small part of it. In the long-term research on the modification of the outer surface of the non-selective molecular sieve, it was found that the modification of the outer surface of the core-phase molecular sieve by the core-shell molecular sieve aims to maintain the high stability and catalytic activity of the molecular sieve to the maximum extent. Silicalite-1 is composed of pure silica with the same MFI framework structure as ZSM-5. It is connected by silicon-oxygen tetrahedrons. It ha...

AI Technical Summary

Problems solved by technology

[0006] One of the technical problems to be solved by the present invention is to overcome the defect that the conventional core-shell molecular sieve preparation technology requires multiple repeated growths to form a dense shell, and there is a waste of shell raw materials and templates.

[0007] The second technical problem to be solved by the present invention is to overcome the phenomenon of non-epitaxial co-growth, non-oriented growth and unevenness of the shell in the conventional core-shell molecular sieve preparation technology, resulting in poor mechanical strength of the shell and poor activity and stability of the catalyst.

This method epitaxially co-existed and oriented growth uniform silicalite-1 shell on the surface of the core phase ZSM-5, the shell has good mechanical strength, and the activity and stability of the catalyst are good, which solves the problem of the catalytic effect of the core-shell molecular sieve and the preparation process of the catalyst. The matching problem of various synthesis parameters

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