A kind of synthetic method of all silicon beta molecular sieve

Abstract

The invention discloses a synthesis method of an all-silicon beta molecular sieve. The method comprises the steps of: (1) mixing a silicon source, a fluorine-containing mineralizer, water, a template agent and an optional alkali source evenly to obtain a reaction mixture with an OH<->:SiO2:F:R:H2O mole ratio of (0.21-4):1:(0.1-5):(0.4-5):(2-50), wherein F represents the mole number of fluorine atoms in the reaction mixture, and R represents the mole number of the template agent; (2) transferring the reaction mixture obtained in step (1) into a pressureproof closed container, conducting crystallization for 0.5-30d under a temperature of 80-200DEG C and a self-generated pressure so as to obtain a crystallization product; and (3) recovering the crystallization product obtained in step (2). The synthesis method provided by the invention can synthesize the all-silicon beta molecular sieve with small particle size, uniform particle distribution and few skeleton defect under an alkaline condition.

Description

technical field [0001] The invention relates to a method for synthesizing all-silicon beta molecular sieves. Background technique [0002] β molecular sieve is a molecular sieve with BEA structure developed by R. Wadlinger in 1967, and its appearance is a symbol of high silicon molecular sieve research. β molecular sieve is a stacking fault intergrowth composed of several polymorphs with different structures but closely related, and it has a three-dimensional twelve-membered ring channel structure. Among them, the channels in the [100] and [010] directions are straight channels with a diameter of about 0.66×0.67 nanometers; the channels in the [001] direction are formed by the intersection of straight channels in the [100] and [010] directions. Yes, it is sinusoidal in shape, and its pore size is about 0.55×0.55 nanometers. [0003] Due to the high ratio of silicon to aluminum in the skeleton and the special three-dimensional twelve-membered ring pore structure, β molecula...

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Problems solved by technology

[0009] Although all-silicon β molecular sieves can be successfully prepared in neutral, alkaline or acidic fluorine-containing systems by using new templates, the synthesis of templates is complicated and the cost is high when using new templates. Therefore, new templates It is difficult to popularize the method in industrialization; the method of preparing all-silicon β molecular sieve under the neutral fluorine-containing system has problems such as high mold-to-silicon ratio, long synthesis cycle, and large particle size of the crystallized product; Molecular sieves also have the disadvantages of large particles and many skeleton defects, and the particle size distribution of the crystallization products of this method is uneven; Under the condition of HF, the corrosion of equipment is relatively serious, and considering the toxicity of HF, this method is not suitable for popularization.

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