Method for synthesizing heteroatomic ZSM-5 molecular sieve and application thereof

Abstract

The invention provides a method for synthesizing a heteroatomic ZSM-5 molecular sieve. The method comprises the steps of (a) adding a gallium source and an aluminum source into a templating agent, then adding sodium hydroxide, and then mixing with a silicon source to form a sol-gel system; (2) crystallizing for 48-80 hours; (3) filtering, drying and roasting to remove the organic templating agent; and (4) carrying out ion exchange on molecular sieve powder by using an ammonium hydroxide solution to obtain the hydrogen-type molecular sieve. According to the synthesis method provided by the invention, the molecular sieve, which is synthesized directly from the inexpensive silicon source, gallium source, aluminum source, mineralizer and organic templating agent, is unnecessary to be subjected to subsequent micropore aperture adjustment. The synthesized heteroatomic ZSM-5 molecular sieve belongs to an MFI structure and no heterophase crystal systems appear. Compared with a conventional ZSM-5 molecular sieve, the heteroatomic ZSM-5 molecular sieve synthesized by the method provided by the invention has the advantages that biomass and polyethylene are rapidly pyrolyzed under the catalytic action of the heteroatomic ZSM-5 molecular sieve, the yield of monocyclic aromatic hydrocarbon is not reduced and the selectivity of benzene, toluene and p-xylene in aromatic hydrocarbon is improved by about 80%.

Description

technical field [0001] The invention belongs to the field of petrochemical industry, and in particular relates to a preparation method and application of molecular sieves for catalyzing fast pyrolysis reactions. Background technique [0002] At present, the global fossil fuel reserves are decreasing sharply, and people are turning their research focus to non-petroleum synthetic liquid fuels to alleviate the shortage of crude oil and natural gas. For example, catalytic fast pyrolysis (CFP) technology is used to convert biomass or waste plastics into liquid fuels. Lignocellulosic biomass or waste plastics are rapidly pyrolyzed to generate small molecular weight organic compounds, and then further reactions such as olefin aromatization, hydrogen transfer, and alkylation occur on molecular sieves, and finally generate aromatics, low-carbon olefins, alkanes, and charcoal. and other organic chemicals. Through catalytic activity evaluation experiments, the researchers found that ...

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Problems solved by technology

However, the disadvantages of the above methods are that the subsequent treatment process is complicated, it is difficult to precisely control the pore size regulation, and it is easy to block some micropore channels to reduce the catalytic activity.

[0004] In addition, patent CN1169953A is about the synthesis of silicon-gallium MFI molecular sieves for methanol aromatization, which does not improve the selectivity of p-xylene in the product; patent CN101722033A uses multi-step crystallization to synthesize molecular sieves with core-shell structure, and hydrothermal The process is more complicated

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