Magnesium carbonate crystal prepared based on hexamethylenetetramine and preparation method thereof

Abstract

The invention discloses a magnesium carbonate crystal prepared based on hexamethylenetetramine and a preparation method thereof, and belongs to the technical field of magnesium carbonate materials. The preparation method comprises the following steps: dissolving urea and magnesium chloride, adding hexamethylenetetramine, oscillating in water bath ultrasonic to fully react, then transferring the reaction system into a hydrothermal reaction kettle to perform hydrothermal reaction, and washing and drying a reactant to obtain magnesium carbonate crystals. According to the invention, magnesium chloride and urea are taken as raw materials, hexamethylenetetramine is taken as an additive, the nucleation-growth process is directionally regulated by the hexamethylenetetramine additive, and an optimized reaction process is adopted, so that the magnesium carbonate crystal with high purity, good crystallinity and an excellent pore structure is successfully synthesized; the prepared magnesium carbonate crystal has an optimized porous structure. According to the structure, the mass transfer efficiency is effectively improved, diffusion and transmission of substances in the material are facilitated, and the preparation method is simple and has wide application potential.

Description

Technical Field

[0001] This invention belongs to the field of magnesium carbonate material technology, specifically relating to a magnesium carbonate crystal based on hexamethylenetetramine and its preparation method. Background Technology

[0002] Anhydrous magnesium carbonate, naturally occurring as magnesite, possesses excellent properties such as thermal insulation, high-temperature resistance, and high thermal conductivity, making it an important inorganic chemical material. It is suitable for the preparation of polymer materials, functional ceramics and glasses, friction materials, carbon anodes, and other materials. It is also used as a food additive, a template for synthesizing porous carbon and other hierarchical structural materials, a carrier for pharmaceuticals and adsorbents, and a refining agent for light metal alloys. Furthermore, due to its environmentally friendly characteristics, anhydrous magnesium carbonate has also demonstrated significant application value in halogen-free flame retardants, optical materials, and water treatment, attracting considerable attention in the field of new materials.

[0003] The application properties of magnesium carbonate (such as rubber reinforcement, ceramic raw material, flame retardancy, etc.) are highly dependent on its microstructure (such as spherical, plate-like, and needle-like forms) and crystal structure (crystal form, such as trihydrate, pentahydrate, anhydrous form, and basic magnesium carbonate with various compositions). Existing research shows that magnesium carbonate exhibits significant polymorphism, and a rich variety of morphologies can be obtained by controlling the synthesis conditions. The formation of specific crystal forms and target morphologies is subject to complex synergistic influences from synthesis parameters such as reactant concentration and molar ratio, reaction temperature, system pH, type and amount of additives, reaction mode (such as stirring rate and feeding sequence), and aging time and conditions. However, how to accurately and repeatedly synergistically control the directional synthesis of specific target crystal forms and desired microstructures to meet the key requirements of different high-performance applications (such as optimizing dispersibility in polymer matrices, enhancing the barrier properties of composite materials, and preparing high-purity specific crystal form raw materials for electronic ceramics, etc.) remains a core technological challenge in the field of magnesium carbonate material preparation. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a magnesium carbonate crystal based on hexamethylenetetramine and its preparation method. Using magnesium chloride and urea as raw materials and hexamethylenetetramine as an additive, magnesium carbonate crystals with high purity, good crystallinity, mechanical stability, and excellent pore structure were successfully synthesized. The prepared magnesium carbonate crystals have an optimized hierarchical porous structure. This structure effectively promotes mass transfer efficiency, facilitates the diffusion and transport of substances within the material, and the preparation method is simple.

[0005] This invention is achieved through the following technical solution: In a first aspect, the present invention discloses a method for preparing magnesium carbonate crystals based on hexamethylenetetramine. Urea and magnesium chloride are dissolved, hexamethylenetetramine is added and the mixture is vibrated in a water bath under ultrasonic conditions to allow it to react fully. The reaction system is then transferred to a hydrothermal reactor for hydrothermal reaction. The reactants are washed and dried to obtain magnesium carbonate crystals.

[0006] Furthermore, the mass ratio of urea to magnesium chloride is 3:1~3.

[0007] Furthermore, the solvent used to dissolve urea and magnesium chloride is water, ethanol, or a mixture of water and ethanol.

[0008] Furthermore, the volume ratio of water to ethanol in the mixture of water and ethanol is 1:1 to 3.

[0009] Furthermore, the mass ratio of hexamethylenetetramine, urea, and magnesium chloride is 1:2~4:1~2.

[0010] Furthermore, the water bath ultrasonic conditions are 24~28℃, 15~30min, and 40~55kHz.

[0011] Furthermore, the conditions for the hydrothermal reaction are: 160~180℃, 3~4h.

[0012] In a second aspect, the present invention discloses magnesium carbonate crystals prepared by the aforementioned preparation method.

[0013] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention utilizes magnesium chloride and urea as raw materials, and hexamethylenetetramine as an additive. By directionally controlling the nucleation-growth process through the hexamethylenetetramine additive and employing an optimized reaction process, magnesium carbonate crystals with high purity, good crystallinity, and excellent pore structure were successfully synthesized. The prepared magnesium carbonate crystals possess an optimized porous structure. This structure effectively promotes mass transfer efficiency, facilitates the diffusion and transport of substances within the material, and the preparation method is simple, possessing broad application potential. Attached Figure Description

[0014] Figure 1 The images show the XRD patterns of magnesium carbonate crystals prepared in Examples 1-3. Figure 2 A scanning electron microscope image of the magnesium carbonate crystals prepared in Example 1; Figure 3 A scanning electron microscope image of the magnesium carbonate crystals prepared in Example 2; Figure 4 A scanning electron microscope image of the magnesium carbonate crystals prepared in Example 3; Figure 5 The image shows a scanning electron microscope (SEM) image of the magnesium carbonate crystals prepared in Comparative Example 1. Detailed Implementation

[0015] The present invention is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods not specifically described in the following examples are generally performed under conventional conditions or as recommended by the manufacturer.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. All reagents and materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions.

[0017] Example 1 Weigh 6g of urea and 4.06g of magnesium chloride into a beaker, add 45mL of water, and sonicate in a water bath at 25℃ for 25min at 60kHz until completely dissolved. Add 0.665g of hexamethylenetetramine and sonicate in a water bath until fully dissolved. Then transfer the solution from the beaker to a polytetrafluoroethylene reactor and hydrothermally react at 180℃ for 3h. After the reaction, the separated solid is thoroughly washed in deionized water, centrifuged 5 times, and dried at 90℃ for 12h to obtain magnesium carbonate crystals. The XRD pattern of the magnesium carbonate crystals is shown below. Figure 1 As shown; a scanning electron microscope image of the magnesium carbonate crystals prepared in Example 1 is shown. Figure 2 As shown, by Figure 2 It can be seen that the magnesium carbonate crystals prepared in Example 1 exhibit a nanoflower-like structure with good dispersibility and filling properties; the porosity is 0.15%, and the specific surface area is 8.2 g / m². 2 The crystallinity is 68%.

[0018] Example 2 Weigh 6g of urea and 4.06g of magnesium chloride into a beaker, add a mixed solvent of water and ethanol (volume ratio of water to ethanol 1:2), and sonicate in a water bath at 25℃ for 25min at 60kHz until completely dissolved. Add 0.665g of hexamethylenetetramine and sonicate in a water bath until fully dissolved. Then transfer the solution from the beaker to a polytetrafluoroethylene reactor and hydrothermally react at 180℃ for 3h. After the reaction, the separated solid is thoroughly washed in deionized water, centrifuged 5 times, and dried at 90℃ for 12h to obtain magnesium carbonate crystals. The XRD pattern of the magnesium carbonate crystals is shown below. Figure 1 As shown, the corresponding peaks in the XRD gradually become sharper, and the full width at half maximum (FWHM) peaks narrower, indicating that the obtained product is a well-crystallized magnesium carbonate crystal with the peak shape of basic magnesium carbonate. This shows that the magnesium carbonate crystals prepared using hexamethylenetetramine as an additive possess the characteristics of both basic and anhydrous magnesium carbonate. The scanning electron microscope image of the magnesium carbonate crystals prepared in Example 2 is shown below. Figure 3 As shown, by Figure 3 It can be seen that the magnesium carbonate crystals prepared in Example 2 have a layered cake-like structure with some unformed textured spherical structures on the surface, resulting in a large specific surface area. The porosity is 0.24%, and the specific surface area is 6.2 g / m². 2 The crystallinity is 72%.

[0019] Example 3 6g of urea and 4.06g of magnesium chloride were weighed into a beaker, and anhydrous ethanol was added. The mixture was sonicated in a water bath at 25℃ for 25 min at 60kHz until completely dissolved. Then, 0.665g of hexamethylenetetramine was added and sonicated in a water bath until fully dissolved. The solution was then transferred to a polytetrafluoroethylene reactor and hydrothermally reacted at 180℃ for 3 h. After the reaction, the separated solid was thoroughly washed in deionized water, centrifuged 5 times, and dried at 90℃ for 12 h to obtain magnesium carbonate crystals. The XRD pattern of the magnesium carbonate crystals is shown below. Figure 1 As shown in the figure; the peaks in Example 3 gradually become sharper and the half-width peaks narrower, indicating that the obtained product is a well-crystallized magnesium carbonate crystal with the peak shape of basic magnesium carbonate. This shows that the magnesium carbonate crystals prepared using hexamethylenetetramine as an additive possess the characteristics of both basic and anhydrous magnesium carbonate. The magnesium carbonate crystals prepared in Example 3 have a textured spherical structure with a surface texture similar to lamellae, a porosity of 0.12%, and a specific surface area of ​​7.9 g / m². 2 The crystallinity is 82%.

[0020] Comparative Example 1 Weigh 6g of urea and 4.06g of magnesium chloride into a beaker, add 35mL of water, and sonicate in a water bath at 25℃ for 30min at 55kHz until completely dissolved. Then transfer the solution from the beaker to a polytetrafluoroethylene reactor and hydrothermally react at 180℃ for 3h. After the reaction, the separated solid is thoroughly washed in deionized water, centrifuged 5 times, and dried at 90℃ for 12h to obtain magnesium carbonate crystals. The scanning electron microscope image of the magnesium carbonate crystals prepared in Example 2 is shown below. Figure 5 As shown. The magnesium carbonate crystals prepared in Comparative Example 1 had a porosity of 0.05%, a specific surface area of ​​35.24 m² / g, and a crystallinity of 52%.

Claims

1. A method for preparing magnesium carbonate crystals based on hexamethylenetetramine, characterized by, Dissolving urea and magnesium chloride, adding hexamethylenetetramine, oscillating in water bath ultrasonic to make it fully react, then transferring the reaction system to hydrothermal reaction kettle to carry out hydrothermal reaction, washing and drying the reactants to obtain magnesium carbonate crystal.

2. The method of claim 1, wherein the magnesium carbonate crystal is prepared based on hexamethylenetetramine. The mass ratio of urea to magnesium chloride is 3:1-3.

3. The method of claim 1, wherein the magnesium carbonate crystal is prepared based on hexamethylenetetramine. The solvent for dissolving urea and magnesium chloride is water, ethanol or mixture of water and ethanol.

4. The method for preparing the magnesium carbonate crystal based on hexamethylenetetramine of claim 3, characterized in that, The volume ratio of water to ethanol in the mixture of water and ethanol is 1:1-3.

5. The method of claim 1, wherein the magnesium carbonate crystal is prepared based on hexamethylenetetramine. The mass ratio of hexamethylenetetramine, urea and magnesium chloride is 1:2-4:1-2.

6. The method for preparing magnesium carbonate crystals based on hexamethylenetetramine according to claim 1, characterized in that, The water bath ultrasonic condition is 24-28℃, 15-30min, 40-55kHz.

7. The method of claim 1, wherein the magnesium carbonate crystal is prepared based on hexamethylenetetramine. The hydrothermal reaction condition is 160-180℃, 3-4h. 8.A magnesium carbonate crystal prepared by the preparation method in any one of claims 1-7.

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