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Low Si/Al ratio ZSM-48 molecular sieve preparation method

A technology of molecular sieves and cations, applied in molecular sieves and base exchange compounds, chemical instruments and methods, inorganic chemistry, etc., can solve the problems of not being suitable for industrialization, limiting the wide application of catalytic reactions, and being difficult for industrial scale-up production

Active Publication Date: 2019-08-16
EAST CHINA UNIV OF SCI & TECH
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Problems solved by technology

Patent CN 103803576A discloses a method of using 12-crown ether-4 as template and ZSM-48 zeolite as seed crystal to synthesize ZSM-48 molecular sieve with low silicon-aluminum ratio, but there is a problem of high crown ether cost
Literature (Microporous and mesoporous materials, 2004, 68 (1-3): 97-104) reported that (CH 3 ) 3 N + (CH 2 ) n N + (CH 3 ) is a structure-directing agent, although the Si / Al ratio of the synthesized ZSM-48 molecular sieve is low, but because the template agent is relatively expensive and toxic, it is not easy for industrial scale-up production
[0004] At present, ZSM-48 molecular sieve is used as a catalyst, mainly facing the following problems (1) The Si / Al ratio of the synthesized ZSM-48 molecular sieve is high, even if the Si / Al ratio of the synthesized ZSM-48 molecular sieve is low, but the structure-oriented structure used for its synthesis (2) If a low-cost template is used, although the cost of the synthetic molecular sieve is reduced, the Si / Al ratio of the synthesized ZSM-48 molecular sieve is high and requires a long crystal (3) The ZSM-48 molecular sieve with high Si / Al ratio has less acid content per unit molecular sieve, which limits its wide application in catalytic reactions and is not suitable for industrialization

Method used

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  • Low Si/Al ratio ZSM-48 molecular sieve preparation method

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preparation example Construction

[0030] Specifically, the preparation method of the ZSM-48 molecular sieve of a kind of low Si / Al ratio provided by the present invention comprises the following steps:

[0031] In the first step, the silicon source, the alkali source and water are mixed to make OH in the resulting mixed solution 1 - / SiO 2 The ratio is between 0.01-1.0;

[0032] In the second step, the mixed solution 1 is mixed with a structure-directing agent (Structure-Directing Agent, SDA) to obtain a mixed solution 2;

[0033] The third step is to mix the mixed solution 2 with the aluminum source to obtain a precursor gel;

[0034] In the fourth step, the precursor gel is subjected to hydrothermal crystallization to obtain a sample (mixture);

[0035] The fifth step is to process the sample to obtain ZSM-48 molecular sieve.

[0036] The structure of the structure directing agent used in the preparation method provided by the present invention is shown in formula I,

[0037] (CH 3 ) 3 N + RX -

[...

Embodiment 1

[0061] Preparation of ZSM-48 molecular sieve M1

[0062] (1) Weigh 4.00g of sodium silicate, 0.56g of sodium hydroxide and 35.80g of secondary deionized water and stir evenly at room temperature, add 0.79g of H 2 SO 4 Adjust OH - / SiO 2 is 0.2;

[0063] (2) add 5.74g allyltrimethylammonium chloride in the solution of step (1) gained, stir again;

[0064] (3) Add 0.12g aluminum nitrate to the solution obtained in step (2), stir to form a homogeneous solution, wherein the mol ratio of each component is SiO 2 :Al 2 o 3 : Na 2 O: SDA: OH - :H 2 O=1:0.005:0.4:1:0.2:60;

[0065] (4) Transfer the obtained solution to a 100 mL hydrothermal kettle. Dynamic hydrothermal crystallization at 160°C for 24 hours;

[0066] (5) The mixture obtained in (4) was centrifuged, washed, and dried to obtain a molecular sieve powder M1 with a Si / Al ratio of 100, which was ZSM-48 molecular sieve by XRD analysis. Calcined at 600° C. for 10 h in an air atmosphere to obtain the final ZSM-48 mo...

Embodiment 2

[0068] Preparation of ZSM-48 molecular sieve M2

[0069] (1) Weigh 3.50g of sodium silicate, 0.39g of sodium hydroxide and 29.80g of secondary deionized water and stir evenly at room temperature, add 0.63g of H 2 SO 4 Adjust OH - / SiO 2 is 0.2;

[0070] (2) add 4.49g allyltrimethylammonium chloride in the solution of step (1) gained, stir again;

[0071] (3) Add 0.21g aluminum nitrate to the solution obtained in step (2), stir to form a homogeneous solution, wherein the molar ratio of each component is SiO 2 :Al 2 o 3 : Na 2 O: SDA: OH - :H 2 O=1:0.01:0.4:1:0.2:60;

[0072] (4) Transfer the obtained solution to a 100 mL hydrothermal kettle. Dynamic hydrothermal crystallization at 160°C for 48 hours;

[0073] (5) The mixture obtained in (4) was centrifuged, washed, and dried to obtain a molecular sieve powder M2 with a Si / Al ratio of 50, which was ZSM-48 molecular sieve by XRD analysis. Calcined at 600° C. for 10 h in an air atmosphere to obtain the final ZSM-48 mo...

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Abstract

The invention discloses a low Si / Al ratio ZSM-48 molecular sieve preparation method, which comprises: (1) treating raw materials to obtain a precursor gel; (2) carrying out hydrothermal crystallization on the precursor gel to obtain a sample; and (3) treating the sample to obtain a ZSM-48 molecular sieve, wherein the raw materials comprise a silicon source, an alkali source, a structure-directingagent (SDA), an aluminum source, an acid and water, the structure-directing agent has a structure represented by a formula I (CH3)3N<+>RX (formula I), R is C2-6 alkenyl or C2-5 alkyl, and X is selected from halogen or hydroxyl.

Description

technical field [0001] The invention relates to a preparation method of a molecular sieve, in particular to a preparation method of a low Si / Al ratio ZSM-48 molecular sieve. Background technique [0002] ZSM-48 molecular sieve is a new type of molecular sieve with high silicon-aluminum ratio developed by Mobil Company in the United States in the early 1980s. It has a one-dimensional ten-membered ring channel structure and is an orthorhombic crystal structure. The ideal channel diameter is Because of its high thermal stability, hydrothermal stability and adjustable acidity, it shows excellent catalytic performance in reactions such as shape-selective catalytic alkylation, hydroisomerization, and methanol-to-hydrocarbon reactions. [0003] Patent US 5075269 discloses a method for synthesizing ZSM-48 molecular sieves, using sodium silicate and silica sol as silicon sources, aluminum sulfate and sodium metaaluminate as aluminum sources, hexamethylammonium bromide as a templat...

Claims

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Application Information

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IPC IPC(8): C01B39/48
CPCC01B39/48C01P2002/72Y02P20/52
Inventor 朱卡克翟淼周兴贵
Owner EAST CHINA UNIV OF SCI & TECH
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