Zsm-5/silicalite-1 core-shell molecular sieves with shell-oriented epitaxial intergrowth

Abstract

The invention relates to a ZSM-5 / silicalite-1 core-shell molecular sieve with shell orientation and epitaxial symbiosis, which mainly overcomes the need for repeated growth to form a dense shell in the conventional core-shell molecular sieve preparation technology, and the use of shell raw materials and template agents Waste defects, and there are still phenomena such as non-epitaxial co-growth, non-oriented growth and inhomogeneity of the shell, resulting in poor mechanical strength of the shell and poor activity and stability of the catalyst. In the present invention, the core-shell molecular sieve containing epitaxial symbiotic dense shell is prepared in the shell molecular sieve crystallization system and under suitable reaction conditions after pretreating the weakly alkaline aqueous solution of the core-phase zeolite material, which is effectively used for the selection of aromatic hydrocarbons. Shape disproportionation, shape-selective transalkylation and shape-selective methylation reactions can generate a large number of useful p-xylene isomers. Through the deployment of core and shell components, the catalyst has high catalytic activity, large aromatics processing capacity, and integrated machinery The characteristics of high strength, less application loss and high selectivity of p-xylene products can be used in industrial production more efficiently.

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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