Synthesizing method of large-diameter Beta molecular sieve

Abstract

The invention discloses a synthesizing method of a large-diameter Beta molecular sieve. The method comprises the following steps: dissolving a template agent R, inorganic base, a silicon source, an aluminum source and water; adding one or a plurality of accelerants including dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate to obtain gel; pre-crystallizing gel under a negative pressure condition to obtain a pre-crystallized sample; and then processing the sample by crystallizing, roasting, ammonia exchange and separating to obtain the large-diameter Beta molecular sieve. With the adoption of the method, the large-diameter Beta molecular sieve with high specific area and high crystalline can be synthesized and is high in hydrothermal stability and has a good application prospect in the fields such as the field of automobile exhaust gas purification and catalyzing and the field of isomerization catalyzing.

Description

technical field [0001] The invention relates to the field of synthesis of Beta molecular sieves, in particular to a method for synthesizing large-diameter Beta molecular sieves. technical background [0002] Beta molecular sieves were first synthesized by Mobil in 1967. Because of their good thermal stability, moderate acidity and hydrophobicity, they are widely used in hydrocarbon hydrocracking, hydroisomerization, alkane aromatization, alkylation and alkanes. It exhibits excellent catalytic performance in the group transfer reaction and so on. [0003] Scientific researchers are constantly trying to synthesize Beta molecular sieves and study the application of Beta molecular sieves, but the particle size of Beta molecular sieves currently synthesized is generally small. [0004] Patent CN106698455A discloses a synthetic method of nano-Beta molecular sieve, which synthesizes high-crystallinity Beta molecular sieve without other crystal impurities by introducing macroporous...

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Problems solved by technology

[0004] Patent CN106698455A discloses a synthetic method of nano-Beta molecular sieve, which synthesizes high-crystallinity Beta molecular sieve without other crystal impurities by introducing macroporous carbon, but the Beta molecular sieve grains synthesized by this method are less than 100 nanometers, resulting in The solid-liquid separation of molecular sieve slurry is difficult, and the Beta molecular sieve with small crystal grains has a large external specific surface area and poor hydrothermal stability. These factors seriously restrict the industrial production and large-scale application of Beta molecular sieves.

[0005] Patent US5164169 discloses a synthetic method of a large-diameter Beta molecular sieve. This patent uses a compound containing tetraethylammonium cations as a structure-directing agent, and a tertiary amine compound is used as a chelating agent to synthesize a large-diameter Beta molecular sieve. The above-mentioned tertiary amine compounds are poisonous, the water solubility of these compounds is not good, they are very volatile, and they are easy to damage the environment in the process of industrial production

The amount of expensive tetraethylammonium cationic structure-directing agent R and environmentally unfriendly tertiary amine chelating agent X in this patent is respectively: R / SiO 2 =0.3~1.0,X / SiO 2 =0.2~0.8, the dosage is relatively large, which increases the burden of industrial production from both economic and environmental aspects

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