Preparation method for hollow micro-mesoporous ZSM-5 molecular sieve

Abstract

The invention relates to a preparation method for a hollow micro-mesoporous ZSM-5 molecular sieve. The preparation method comprises the following steps: dispersing a template agent into a pH regulatorso as to obtain a dispersion A of the template agent, then dissolving an aluminum source into the dispersion A so as to obtain a uniformly-mixed solution B, then adding a silicon source so as to obtain a gel C, wherein the molar ratio of Al2O3 to SiO2 to M2O to R to H2O is 1: (8-200): (20-60): (10-20): (200-1000), M represents Na or K, R represents the template agent with a structural formula which is described in the specification, and in the structural formula, R is CH3(CH2)n, n has a value range of 1 to 6, and X- is Br- or Cl-; subjecting the gel C to evaporation and concentration so as toobtain a gel D, wherein the mass of the gel D accounts for 50% to 60% of the mass of the gel C; crystallizing the gel D in a temperature range of 180 DEG C to 220 DEG C for 1 to 3 d, and carrying outcooling to a room temperature; and filtering a product obtained in the step (3), and carrying out washing, drying and calcining so as to obtain the hollow micro-mesoporous ZSM-5 molecular sieve.

Description

technical field [0001] The invention belongs to the field of ZSM-5 molecular sieves, in particular to a method for preparing hollow microporous mesoporous ZSM-5 molecular sieves. Background technique [0002] Zeolite molecular sieve is a class of important inorganic materials widely used in modern chemical fields such as catalysis, adsorption, and separation; Mobil Corporation of the United States synthesized ZSM-5 molecular sieve (US3702886) for the first time in 1972; Its ordered three-dimensional pore structure, large specific surface area, high hydrothermal stability, adjustable acid center and exchangeable cations and other excellent properties have become one of the most widely used catalyst molecular sieve raw powders in industry. [0003] With the continuous development of the industrial process and the continuous improvement of industrial demand, the requirements for the performance of zeolite molecular sieves are getting higher and higher, such as reactants, interm...

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Problems solved by technology

[0005] Conventional ZSM-5 molecular sieves only contain micropores, and their mass transfer and diffusion capabilities are limited, which not only leads to a decrease in the yield of low-carbon olefins, but also forms coke to block the pores and cause catalyst deactivation; therefore, people have been working to improve the ZSM-5 molecular sieve Diffusion and mass transfer performance; Patent CN103447076A reports the preparation of microporous and mesoporous ZSM-5 / SiO2 catalysts with macroporous-mesoporous SiO2 as the carrier, which effectively avoids the use of binders to block the pores. In the catalytic cracking reaction of n-octane, The maximum yields of ethylene and propylene reached 42.5% and 35.7% respectively; Patent CN103071522A synthesized microporous and mesoporous ZSM-5 molecular sieves by adding two organic templates, and applied it to the catalytic cracking of C4-C6 mixed hydrocarbons to produce low-carbon olefins reaction, the prepared microporous mesoporous ZSM-5 molecular sieve has the advantages of good catalytic activity, high diene yield and long catalyst life; the above research results show that: multi-level porous ZSM-5 molecular sieve can significantly improve catalytic performance; The technical defects of the synthesis method of the porous and mesoporous ZSM-5 molecular sieve are relatively complex, the preparation conditions of high temperature and high pressure are harsh, the synthesis efficiency of a single reactor is low, and a large amount of synthetic waste liquid is discharged, which greatly limits the industrial production and production of the microporous and mesoporous ZSM-5 molecular sieve. application; therefore, it is of great significance to develop new green and sustainable molecular sieve synthesis methods

[0006] Usually, the cost of these synthetic ZSM-5 zeolites is very high, which is unfavorable for industrial applications; therefore, how to develop a new type of cheap organic template to synthesize ZSM-5 zeolites is of great significance

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