Preparation method of nano-ZSM-5 molecular sieve

Abstract

The invention relates to a preparation method of a nano-ZSM-5 molecular sieve, which belongs to the field of preparation of zeolite molecular sieve catalysts. The preparation method can solve the problem that the existing synthesis technology has the defects of easy emergence of mixed crystal phase, high cost, environmental pollution and easy loss of features of nanomaterials. The method is as follows: adding pre-crystallized crystal seeds into a gel system of the template-free synthetic nano-ZSM-5 molecular sieve, carrying out crystallization for 24 hours at the temperature of 160-180 DEG C,cooling to room temperature, carrying out centrifugal filtration on products, washing, drying and baking. The prepared nano-ZSM-5 molecular sieve is highly concentrated nanoscale crystals without themixed crystal phase; and the method has the advantages of low cost and environmental protection.

Description

technical field [0001] The invention belongs to the field of preparation of zeolite molecular sieve catalysts, in particular to a preparation method of nanometer ZSM-5 molecular sieves. Background technique [0002] ZSM-5 molecular sieve is one of the most important molecular sieve catalytic materials at present because of its suitable pore structure, adjustable acid center, good thermal stability and hydrothermal stability, and outstanding shape-selective catalysis. It is used in catalytic fields such as petroleum processing, petrochemical industry, coal chemical industry and fine chemical industry. However, since ZSM-5 molecular sieve belongs to medium-pore zeolite, its pore size is small, and the diffusion resistance of molecules with large dynamic size increases in its pore channels, which limits its application in macromolecular catalytic reactions to a certain extent. At present, there are two main methods to solve this problem. One is to introduce a mesoporous struct...

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Problems solved by technology

[0005] The purpose of the present invention is to provide a method for preparing nanometer ZSM-5 molecular sieves, by introducing precrystallized seeds into a gel system without templates to prepare nanometer ZSM-5 molecular sieves with different silicon-aluminum ratios to solve the problem of existing nanometer ZSM-5 molecular sieves. The synthesis method of ZSM-5 molecular sieve has the problem of inability to prepare pure phase nano-ZSM-5 molecular sieve with high crystallinity due to the presence of miscellaneous crystal phases such as mordenite in the synthesis method without templates, and the use of a large number of organic amine compounds as templates. The cost is high and the toxicity is high, and the problem of nano molecular sieve grains growing due to sintering will also occur during the high-temperature calcination process of removing the template agent

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