Preparation method of beta molecular sieve

Abstract

The invention discloses a preparation method of a beta molecular sieve. The method comprises the following steps: step 1, synthesizing initial gel: mixing a silicon source, an aluminum source, an alkaline metal source and water, and performing uniform stirring to synthesize the initial gel, wherein based on SiO2 of the silicon source, Al2O3 of the aluminum source, and Na2O of the alkaline metal source, molar ratios of raw materials for synthesizing the initial gel are as follows: SiO2 / Al2O3=(30-150):1, Na2O / SiO2=(0.03-0.35):1, and H2O / SiO2=(3.0-50.0):1; step 2, performing microwave treatment on the initial gel: adding a beta molecular sieve seed crystal into the initial gel prepared in the step 1, wherein a ratio of silicon to aluminum in the seed crystal is as follows: SiO2 / Al2O3=(20-100):1, and the adding amount is 3%-25% by mass of SiO2, performing uniform mixing, and performing microwave heating treatment to obtain crystallized precursor gel; and step 3, performing a crystallization reaction: performing a crystallization reaction on the crystallized precursor gel obtained in the step 2 by microwave heating to obtain the beta molecular sieve product, wherein the reaction temperature is 140-180 DEG C, and the reaction time is 4-20 h. According to the method provided by the invention, the molecular sieve obtained by the method has a smaller particle size, a rich pore structureand a relatively-smooth channel, thereby facilitating promoting catalytic cracking and isomerization.

Description

technical field [0001] The invention belongs to the technical field of catalytic chemistry, and in particular relates to a synthesis method of beta molecular sieves. Background technique [0002] β molecular sieve is a patented product USP3308069 researched and developed by Mobil Petroleum Company of the United States in 1967. The earlier reports that β molecular sieves have excellent catalytic performance are the follow-up patents EP0159846 and EP0159847 developed by Mobil Corporation for β molecular sieves, which disclose that β molecular sieves have excellent activity for hydrocarbon cracking and isomerization. Since the 1990s, with the understanding of the crystal structure of β molecular sieve, the research on the synthesis and catalytic performance of β molecular sieve has been carried out rapidly. Excellent catalytic performance in numerous catalytic reactions in petroleum refining and petrochemical processes such as wax and photocatalysis. Because it is the only hi...

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Problems solved by technology

However, since no organic template is added to the system, it is difficult to maintain the stability of the reaction system only by the structure-guiding effect of the seed crystals. As a result, the phase region of the synthesized β molecular sieve is very narrow, and it is difficult to control the actual reaction conditions, and it is easy to generate miscellaneous crystals

[0006] To sum up, conventional hydrothermal synthesis of β molecular sieves generally uses organic templates, and the production time is relatively long, especially due to the large amount of templates used, resulting in very high production costs, and the molecular sieve products need to be roasted to release templates in the later stage. , will cause damage to the product structure, and the removed template agent will also seriously pollute the environment

Now there is a technology for synthesizing β molecular sieves without adding additional organic templates. However, due to the conventional hydrothermal synthesis method, it is difficult to maintain the stability of the reaction system only by the structure-guiding effect of the seed crystals. As a result, the phase region of the synthesized β molecular sieves is very narrow. It is more difficult to control the actual reaction conditions, and it is easier to produce miscellaneous crystals

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