Preparation method of fluorine-containing MFI zeolite membrane

Abstract

The invention provides a preparation method of a fluorine-containing MFI zeolite membrane, which is characterized by comprising an ultra-thin synthetic liquid containing fluoride (MF), wherein the molar ratio is 1SiO2: 0.05-1.5MF: 0.05-0.5TPABr: 0.05-0.5TPAOH: 200-2000H2O, and a layer of continuous dense fluorine-containing MFI zeolite membrane is formed on the surface of a porous tubular supporting body coated with fluorine-containing MFI zeolite crystal seeds by using a secondary growth hydrothermal method. The pervaporation test is carried out for the prepared MFI zeolite membrane in an ethanol / water (5 / 95wt%) system at the temperature of 60 DEG , and the permeation flux and the separation factor can be respectively up to 2.85kg / m2. h and 68. The method has mild conditions of preparation process, and simple and fast operation step, and greatly reduces the contents of a silicon source and a template agent in the synthetic liquid, thereby greatly reducing the preparation cost of the membrane, and obviously improving the permeability of the MFI zeolite membrane; and the fluorine-containing MFI zeolite membrane has wide application prospects in the fields of the separation of liquid such as organic matter / water mixture, gas separation, membrane reactors and the like.

Description

technical field [0001] The invention provides a preparation technology for synthesizing a fluorine-containing MFI zeolite molecular sieve membrane material and its recovery application in a low-concentration organic matter / water mixture, belonging to the field of molecular sieve membrane material preparation and application. Background technique [0002] Zeolite molecular sieve membrane is a new type of microporous inorganic membrane material developed in recent years. Because of its good chemical and mechanical stability, it can meet the requirements of high flux, high selectivity, heat resistance and solvent resistance. People pay attention to it, and it has quickly become the most promising research hotspot in the field of membrane separation. In particular, the MFI zeolite molecular sieve membrane has an excellent pore structure. It has two cross-linked pore systems, one is a linear channel in the b-axis direction with a pore size of 0.53×0.56nm, and the other is a sinus...

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Problems solved by technology

[0004] Tavolaro et al. (Desalination, 147 (2002) 333) used sodium fluoride to replace the alkali in the synthesis solution, and successfully prepared VS-1 molecular sieve membrane on the tubular alumina support, but the content of silicon source and template agent in the synthesis sol was relatively low. High (the molar component ratio of the synthetic solution is 0.5VOSO 4 -10NaF-1.25TPABr-10SiO 2 -330H 2 O), and it needs to be crystallized at 170°C for 6 days, and the preparation steps are complicated and cumbersome

Gualtieri et al. (Microp.Mesop.Mater., 111 (2008) 604) utilize hydrofluoric acid to neutralize tetrapropylammonium hydroxide (synthetic liquid molar composition 3TPAOH: 25SiO 2 : 975H 2 (0: 100EtOH: 3HF), the TPA-MFI zeolite molecular sieve membrane was successfully prepared on porous glass and alumina sheet support under neutral conditions, but it needs to be prepared in a thicker (H 2 O / SiO 2 =39) in the synthetic sol at 100°C for 120 hours to form a layer of TPA-MFI molecular sieve membrane on the surface of the support, and the seed layer is easy to fall off during the hydrothermal synthesis so that a dense molecular sieve layer cannot be formed

[0005] In the existing literature reports, researchers generally post-treat molecular sieves or molecular sieve membranes with fluorine to obtain molecular sieve membranes with higher activity, but lattice defects often occur to varying degrees while deskeletal aluminum and non-skeleton fragments, resulting in no improvement in the structure and performance of molecular sieves

In the preparation of MFI zeolite molecular sieve membrane in a fluorine-containing system, the content of silicon source and template agent in the synthetic sol used is high, the synthesis time is long, and the preparation cost is high. More importantly, the synthesized MFI zeolite molecular sieve membrane crystal The fluorine element has not been detected in the framework to enter the framework

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