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Preparation method of heteroatom MFI molecular sieve nanosheet

A technology of heteroatoms and nanosheets is applied in the field of preparation of heteroatom MFI molecular sieve nanosheets, which can solve problems such as unfavorableness and achieve the effects of avoiding precipitation, simple and easy synthesis process, and good parallelism.

Pending Publication Date: 2021-04-09
NANKAI UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Moreover, we found in our research that due to its strong complexation, fluorine is easy to complex with heteroatoms in the synthesis system, and its addition is unfavorable for the synthesis of some heteroatom molecular sieves

Method used

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  • Preparation method of heteroatom MFI molecular sieve nanosheet
  • Preparation method of heteroatom MFI molecular sieve nanosheet
  • Preparation method of heteroatom MFI molecular sieve nanosheet

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preparation example Construction

[0040] The present invention provides a kind of preparation method of heteroatom MFI molecular sieve nano sheet, and its concrete steps are:

[0041] (1) Weighing the structure directing agent, silicon source and water according to the raw material ratio of each reactant, mixing and stirring, forming a synthetic sol without adding alkali metal;

[0042] (2) Weigh the heteroatom precursor in the required proportion, add it into the above-mentioned synthetic sol after dissolving, stir and age at 25-90° C. for 1-100 hours, and prepare the synthetic mother liquor;

[0043] (3) adding an acid reagent to the above synthetic mother liquor, adjusting its pH value in the range of 7.0 to 9.5, and continuing to stir at 25 to 90°C for 1 to 24 hours;

[0044] (4) Put the synthetic mother liquor obtained in step (3) into a reaction kettle, and conduct hydrothermal crystallization at 80-180° C. for 24-300 hours;

[0045] (5) The mixture obtained by hydrothermal crystallization is subjected ...

Embodiment 1

[0059] Synthesis method: Add 15g tetrapropylammonium hydroxide (25%) and 35g ethyl orthosilicate to 50mL water respectively, stir at 80°C for 2 hours, then add 1.7g tetrabutyl titanate, and continue stirring at 80°C for 12 hours , and then adjust the pH value of the synthesis system at about 8.5 with 1mol / L sulfuric acid, continue to stir at 80°C for 12 hours, then put it into a polytetrafluoroethylene-lined reactor, crystallize at 95°C for 7 days, and then cool to room temperature , washed with deionized water, and dried at 80°C to obtain the final product.

[0060] figure 1 is the XRD spectrum of the obtained product. It can be seen that the obtained sample has a characteristic diffraction peak of the MFI structure and has a high degree of crystallinity. figure 2 It is the UV-Vis spectrum of the obtained sample, and there is an obvious absorption peak at 220nm, indicating that Ti element enters the molecular sieve framework. image 3 is the FTIR spectrum of the obtained s...

Embodiment 2

[0062] Synthesis method: referring to the method of Example 1, adjust the pH value of the synthesis system to 7.5, 8, 8.5, 9, 9.5 and not adjust the pH value respectively. The crystallization temperature is 110°C, the crystallization time is 12 days, 10 days, 6 days, 4 days, 2 days and 2 days respectively, and the titanium source is tetrabutyl titanate. After the crystallization is completed, the sample is filtered, washed and dried to obtain the final product. The results show that the obtained products are all MFI molecular sieve nanosheets containing heteroatom Ti, and the thickness of the nanosheets of the obtained products can be adjusted by adjusting the pH value of the system. The specific results are shown in Table 1 below. Figure 5 It is the SEM photo of the obtained sample 1, it can be seen that the sample is an ultra-thin nanosheet with a thickness of about 30 nm.

[0063] Table 1. Effect of pH value of synthesis system on heteroatom MFI molecular sieve nanosheets...

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Abstract

The invention discloses a preparation method of a heteroatom MFI molecular sieve nanosheet. The method is characterized by comprising the steps of stirring and hydrolyzing a certain amount of an organic template agent, a silicon source and a certain amount of water, adding a heteroatom-containing precursor, aging at the temperature of 25-90 DEG C for 1-100 hours, adding a certain amount of an acidic reagent to adjust the pH value of the synthesis system, continuing stirring at the temperature of 25-90 DEG C for 1-12 hours, finally completing crystallization at the temperature of 80-180 DEG C, and obtaining the nanosheet with the thickness of 20-300nm. The preparation method is simple in step and high in product yield, the crystallinity can reach 90% or above, and especially the crystallization process can be completed at the low temperature of 100 DEG C or below and under the normal pressure. Meanwhile, according to the method, the thickness of the heteroatom MFI molecular sieve nanosheet can be effectively regulated and controlled within the range of 20-300nm by controlling the pH value of the aging and synthesis system. In addition, generation of heteroatoms outside the framework can be effectively avoided due to the low pH value.

Description

technical field [0001] The invention belongs to the technical field of preparation of molecular sieves, in particular to a preparation method of heteroatom MFI molecular sieve nanosheets. Background technique [0002] MFI molecular sieve is a kind of microporous zeolite molecular sieve composed of double ten-membered ring intersecting channels. Its typical representative is ZSM-5 molecular sieve, a silica-alumina molecular sieve with MFI topology. This type of molecular sieve has been widely used in catalysis, adsorption Separation, ion exchange and other fields. Heteroatom MFI molecular sieves can be prepared by introducing heteroatoms (titanium Ti, tin Sn, iron Fe, gallium Ga, boron B, niobium Nb, zirconium Zr, tantalum Ta, etc.) Performance, such as titanium silicon molecular sieve TS-1, can further broaden the application range of this type of molecular sieve. [0003] However, the microporous structure of MFI molecular sieve itself will have a large diffusion resistan...

Claims

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Application Information

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IPC IPC(8): C01B39/06C01B39/04B01J29/89
CPCC01B39/06C01B39/04B01J29/89C01P2004/20C01P2004/64C01P2004/62C01P2004/61C01P2002/72C01P2002/84C01P2004/03B01J2229/183Y02P20/52
Inventor 武光军代卫炯邰文姝戴卫理关乃佳李兰冬
Owner NANKAI UNIV
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