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Method for preparing mesoporous molecular sieve

A mesoporous molecular sieve, said technology, applied in the field of preparation of mesoporous molecular sieve MCM-48, can solve the problems of harsh preparation conditions, difficult operation, long hydrothermal crystallization time, etc., and achieve the effect of improving hydrothermal stability

Inactive Publication Date: 2008-01-30
EAST CHINA UNIV OF SCI & TECH
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  • Abstract
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Problems solved by technology

[0005] Kim et al. proposed adding NaCl during the hydrothermal preparation process to improve the hydrothermal stability of MCM-48 molecular sieves (J.M.Kim, S.K.Kim, R.Ryoo.Synthesis of MCM-48 single crystals.Chem.Commun.(1998) 259 ), though this method can improve the hydrothermal stability of MCM-48, because the preparation condition of MCM-48 molecular sieve is harsher, as interrupting the hydrothermal crystallization process of MCM-48 molecular sieve, may not be able to obtain MCM-48 molecular sieve
In addition, this method also has defects such as difficult operation and longer hydrothermal crystallization time.
Jun et al. propose to adopt the method of hydrothermal post-treatment to improve the hydrothermal stability of MCM-48 molecular sieve (S.Jun, J.M.Kim, R.Ryoo, Y.S.Ahn, M.H.Han.Hydrothermal stability ofMCM-48 improved by post-synthesis Restructuring in salt solution.Micopor.Mesopor.Mater.41(2000)119), although it has achieved success in improving the hydrothermal stability of MCM-48 molecular sieves, its operation process is also complicated and additional hydrothermal treatment time is required , not conducive to industrial production

Method used

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  • Method for preparing mesoporous molecular sieve
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  • Method for preparing mesoporous molecular sieve

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preparation example Construction

[0024] The preparation method of said mesoporous molecular sieve MCM-48 of the present invention comprises the steps:

[0025] (1) First put tetraethylsilicate and water in a container, then add sodium hydroxide and sodium fluoride to the container in turn, stir for 30 to 40 minutes, at a temperature of 30°C to 40°C Then, add hexadecyltrimethylammonium bromide to the container, and stir for 1 hour to obtain a reaction mixture (when preparing mesoporous molecular sieve MCM-48 doped with transition metals or rare earth elements, add ten Precursors containing transition metals or rare earth elements are added before hexaalkyltrimethylammonium bromide, such as water-soluble salts containing transition metals or rare earth elements);

[0026] The molar ratio of tetraethylsilicate, sodium hydroxide, cetyltrimethylammonium bromide, water and sodium fluoride is 1:0.25:0.65:60:0.1~0.2;

[0027] (2) Transfer the reaction mixture obtained from step (1) into a polytetrafluoroethylene cup...

Embodiment 1

[0030] First, put 10 ml of tetraethyl silicate and 50 ml of water in a container, then add 0.9 g of sodium hydroxide and 0.18 g of sodium fluoride to the container in turn, stir for 30-40 minutes, and Under the condition of 30° C. to 40° C., 10.6 g of cetyltrimethylammonium bromide was added into the container, and stirred for 1 hour to obtain a reaction mixture. The obtained reaction mixture was transferred into a polytetrafluoroethylene cup, and the hydrothermal crystallization reaction was carried out at 120°C. After 16 hours, the product obtained from the hydrothermal crystallization reaction was suction-filtered, washed until neutral, and dried. The raw powder was calcined at 550° C. for 6 hours to obtain the target product (mesoporous molecular sieve MCM-48).

[0031] Hydrothermal stability test of mesoporous molecular sieve MCM-48: Mix 0.1 gram of the above-prepared MCM-48 powder and 100 ml of deionized water, and filter out the product after continuous reflux at 100 °C...

Embodiment 2

[0033] Ammonium fluoride is used as a fluoride salt to prepare MCM-48 with high hydrothermal stability:

[0034] Except that 0.16 g of ammonium fluoride was used instead of sodium fluoride in Example 1, other preparation and hydrothermal stability test conditions were the same as in Example 1.

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Abstract

The invention relates to a method for preparing meso-porous molecular sieve MCM-48, including the main steps of: firstly in turn placing silicon source, alkali source, template agent and water soluble fluorine salt in a vessel, then making hydrothermal crystallization reaction at 0.1MPa, and finally washing, drying and baking the resultant to obtain the target matter. As compared with existing techniques, its remarkable advantage is that the prepared MCM-48 has good hydrothermal stability (i.e. pore canals does not collapse in 100 deg.C water for 72 hours), shortening the preparing cycle of the MCM-48 molecular sieve. Besides, the invention has the advantages of simple and easy-to-operate whole preparing process, excellent reaction repeatability, wide application range, etc.

Description

technical field [0001] The invention relates to a preparation method of a molecular sieve, in particular to a preparation method of a mesoporous molecular sieve MCM-48. Background technique [0002] For a long time, microporous zeolite molecular sieves have been widely used in the field of industrial catalysis, but their too small pore size limits the diffusion of macromolecular reactants. Therefore, researchers have been working on finding a class of large pore size molecular sieves for many years. In 1992, Mobil successfully developed the M41S series of mesoporous molecular sieves, thus solving this problem. [0003] M41S series mesoporous molecular sieves include MCM-41 molecular sieve with one-dimensional hexagonal structure, MCM-48 molecular sieve with three-dimensional cubic structure and MCM-50 molecular sieve with layered instability. The pore size range of this type of molecular sieve is between 2 and 10 nanometers, and they have the following main excellent charac...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B39/04
Inventor 张金龙邵耀锋王灵芝陈锋
Owner EAST CHINA UNIV OF SCI & TECH