Preparation method of fibrous mordenite

Abstract

The invention provides a preparation method of fibrous mordenite. The preparation method comprises the following steps: (1) mixing alkaline silica sol, sodium hydroxide, sodium metaaluminate, strontium chloride hexahydrate and deionized water according to a certain proportion; (2) stirring until the materials are uniformly mixed, putting the mixture into a high-pressure reaction kettle, and crystallizing at the crystallization temperature of 150-200 DEG C for 24-120 hours; and (3) after the reaction, taking out, cooling, carrying out suction filtration, and drying to obtain the fibrous mordenite. The morphology of the mordenite can be controlled by adding strontium chloride, and the obtained zeolite is high in crystallinity and can be used for large-scale production. The growth of mordenite in the b-axis direction is controlled, the grain width is controlled to be 20-100 nanometers, and the micron-size length is kept in the c-axis direction. The mordenite obtained by the method is not only beneficial to the application of the mordenite in catalysis and adsorption, but also beneficial to the operation advantages of the mordenite in the preparation processes of separation, filtration and the like, so that the mordenite has very good application potential.

Description

Technical Field

[0001] The present invention belongs to the field of utilization of inorganic materials, and particularly relates to a method for preparing fibrous mordenite. Background Art

[0002] From the development process of zeolite molecular sieves, whether it is from natural zeolites to synthetic zeolites, low-silica zeolites to high-silica zeolites, or from silica-alumina zeolites to aluminophosphate zeolites, heteroatom molecular sieves and nano-molecular sieves, and then to molecular sieves with inorganic templates instead of organic templates, researchers have been committed to discovering and creating more molecular sieves with excellent properties, so that they can better serve the chemical industry, agriculture, construction industry, and environmental protection, and play a greater role.

[0003] The synthesis of mordenite molecular sieves has been an interesting research direction for research scholars for decades. Because of its good catalytic activity and thermal stability, it has become one of the important zeolites in industry and can be used as a solid acid catalyst in refining and petrochemical catalytic processes. Mordenite has a wide range of applications in petrochemical fields such as catalytic cracking, hydrocracking, hydroisomerization, oligomerization, transalkylation, and the conversion of methanol and acetone to olefins.

[0004] In order to synthesize new mordenite molecular sieves with low cost, environmental protection, energy saving, and better performance, research scholars have adopted methods such as changing different raw material ratios, crystallization time, and temperature, or using organic templates or introducing metal heteroatoms, etc. The morphology of the molecular sieve greatly affects the accessibility of micropores. Therefore, molecular sieves with nanometer size are more conducive to diffusion. Researchers have great interest in controlling the morphology and size of mordenite molecular sieves. Therefore, many mordenites with different morphologies and different crystal sizes such as needle-like, disk-like, spherical, rod-like, columnar, and prismatic have been synthesized so far. Summary of the Invention

[0005] Aiming at the above deficiencies existing in the prior art, the purpose of the present invention is to provide a method for preparing fibrous mordenite, which prepares fibrous mordenite by controlling the silicon-aluminum ratio and the type of base.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A method for preparing fibrous mordenite, comprising the following steps:

[0007] (1) Mix alkaline silica sol, sodium hydroxide, sodium aluminate, strontium chloride hexahydrate and deionized water in a certain proportion;

[0008] (2) After stirring until evenly mixed, place it in a high-pressure reaction kettle and carry out crystallization at a crystallization temperature of 150-200 °C for a crystallization time of 24-120 h;

[0009] (3) After the reaction, take out the product, cool it, filter it by suction, and dry it to obtain fibrous mordenite.

[0010] Further, in step (1), the molar ratio of Na:Sr:Al:Si:H₂O is 0.1 - 0.8:0.03:0.08:1:30.

[0011] Further, in step (2), the crystallization temperature is 170 °C.

[0012] Further, in step (2), the crystallization time is 72 h.

[0013] Further, in step (3), the drying conditions are: drying at 80 °C for 12 h.

[0014] Further, the fiber diameter of the fibrous mordenite is 20 nm.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The synthesis process of the present invention is simple. By adding strontium chloride to control the morphology of mordenite, the obtained product presents a network material woven by strip-shaped fibers, and has high crystallinity, which can be used for large-scale production.

[0017] 2. Due to the special morphology of the mordenite in the present invention, the grain width in the b-axis direction is 20 - 100 nanometers, which can significantly improve the mass transfer and diffusion problems of mordenite, and thus improve the catalytic reaction effect of mordenite; while the length in the c-axis direction remains in the micron size, which is beneficial to the operation advantages of the molecular sieve in the preparation processes such as separation and filtration, so it has good application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 XRD patterns of the mordenite obtained in Examples 1 - 4 and the XRD standard PDF#80 - 0642 of mordenite (PDF#80 - 0642: Figure 1 vertical line; ◆: quartz);

[0019] Figure 2 SEM image of the mordenite obtained in Example 1;

[0020] Figure 3 SEM image of the mordenite obtained in Example 2;

[0021] Figure 4 SEM image of the mordenite obtained in Example 3;

[0022] Figure 5 SEM image of the mordenite obtained in Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0023] The method of the present invention will be described in detail below in conjunction with specific embodiments and the accompanying drawings.

[0024] I. Preparation method of fibrous mordenite

[0025] Example 1

[0026] A preparation method of fibrous mordenite comprises the following steps:

[0027] 1) After 0.1 mol of NaOH and 20 mol of water are mixed and dissolved, 1 mol of alkaline silica sol is added. After stirring evenly, 0.08 mol of sodium aluminate is added;

[0028] 2) After the above mixed gel is stirred evenly, 0.0333 mol of strontium chloride hexahydrate is added;

[0029] 3) After stirring for 1 h, the mixed gel is transferred to a polytetrafluoroethylene reaction kettle and left to react at 170 °C for 72 hours;

[0030] 4) After the reaction is completed and the reaction kettle is cooled, the reaction product is taken out, washed with water and filtered. The filter cake is dried at 80 °C for 12 h to obtain a sample.

[0031] Example 2

[0032] A preparation method of fibrous mordenite comprises the following steps:

[0033] 1) After 0.3 mol of NaOH and 20 mol of water are mixed and dissolved, 1 mol of alkaline silica sol is added. After stirring evenly, 0.08 mol of sodium aluminate is added;

[0034] 2) After the above mixed gel is stirred evenly, 0.0333 mol of strontium chloride hexahydrate is added;

[0035] 3) After stirring for 1 h, the mixed gel is transferred to a polytetrafluoroethylene reaction kettle and left to react at 150 °C for 120 hours;

[0036] 4) After the reaction is completed and the reaction kettle is cooled, the reaction product is taken out, washed with water and filtered. The filter cake is dried at 80 °C for 12 h to obtain a sample.

[0037] Example 3

[0038] A preparation method of fibrous mordenite comprises the following steps:

[0039] 1) After 0.5 mol of NaOH and 20 mol of water are mixed and dissolved, 1 mol of alkaline silica sol is added. After stirring evenly, 0.08 mol of sodium aluminate is added;

[0040] 2) After the above mixed gel is stirred evenly, 0.0333 mol of strontium chloride hexahydrate is added;

[0041] 3) After stirring for 1 h, transfer the mixed gel into a polytetrafluoroethylene reaction kettle and let it stand and react at 200 °C for 24 h;

[0042] 4) After the reaction is completed, cool the reaction kettle, take out the reactant, wash it with water and filter it. The filter cake is dried at 80 °C for 12 h to obtain the sample.

[0043] Example 4

[0044] A preparation method of fibrous mordenite is as follows:

[0045] 1) After 0.8 mol of NaOH and 20 mol of water are mixed and dissolved, add 1 mol of alkaline silica sol, stir evenly and then add 0.08 mol of sodium aluminate;

[0046] 2) After the above mixed gel is stirred evenly, add 0.0333 mol of strontium chloride hexahydrate;

[0047] 3) After stirring for 1 h, transfer the mixed gel into a polytetrafluoroethylene reaction kettle and let it stand and react at 170 °C for 72 h;

[0048] 4) After the reaction is completed, cool the reaction kettle, take out the reactant, wash it with water and filter it. The filter cake is dried at 80 °C for 12 h to obtain the sample.

[0049] II. Sample testing

[0050] (1) XRD testing

[0051] Figure 1 The XRD testing was carried out on the fibrous mordenite prepared in Examples 1-4. It can be seen from the figure that mordenite can be obtained in all four examples, but the sample is mixed with quartz phase.

[0052] (2) SEM testing

[0053] Figures 2 - 5 The SEM testing was respectively carried out on the fibrous mordenite prepared in Examples 1-4. From Figure 2 it can be seen that the mordenite prepared in Example 1 is about 20 nm in the b-axis direction and the size in the c-axis direction remains in the micron level; the size in the b-axis direction of the mordenite obtained in Examples 2 and 3 is similar to that in Example 1, but the purity of the fibrous crystals is lower than that of the sample in Example 1; the mordenite obtained in Example 4 is changed from fibrous to flaky, and the thickness of the flake is about 20 nm.

[0054] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention rather than limitations. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing fibrous mordenite, characterized in that: The steps include: (1) mixing alkaline silica sol, sodium hydroxide, sodium aluminate, strontium chloride hexahydrate and deionized water in a certain proportion; (2) After stirring until the mixture is uniform, the mixture is placed in a high pressure reactor and crystallized at a crystallization temperature of 150 to 200° C. for a crystallization time of 24 to 120 hours; (3) After the reaction is completed, the zeolite is taken out, cooled, filtered and dried to obtain fibrous mordenite.

2. The method for preparing fibrous mordenite according to claim 1, characterized in that: In step (1), the molar ratio of Na:Sr:Al:Si:H2O is 0.1-0.8:0.03:0.08:1:

30.

3. The method for preparing fibrous mordenite according to claim 1, characterized in that: In step (2), the crystallization temperature is 170°C.

4. The method for preparing fibrous mordenite according to claim 1, characterized in that: In step (2), the crystallization time is 72 hours.

5. The method for preparing fibrous mordenite according to claim 1, characterized in that: In step (3), the drying conditions are: drying at 80° C. for 12 hours.

6. The method for preparing fibrous mordenite according to claim 1, characterized in that: The fibrous mordenite fiber has a diameter of 20 nm.

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