Preparation method of sodium magnesium triphosphate crystal material

Abstract

The invention relates to a preparation method of a Na3Mg3 (PO4) 3 crystal material. A brand-new, simple and energy-saving preparation method, namely a sol-gel-roasting method, is used. The method takes sodium phytate as a phosphorus source and a sodium source and magnesium chloride hexahydrate as a magnesium source, and is low in price and environment-friendly. The sodium phytate solution and the magnesium chloride hexahydrate solution are isometrically mixed and uniformly stirred according to the raw material ratio of 1: 1, and react for 4-6 hours at low temperature to be converted into a clear solution from an opaque sol state, and meanwhile, a large number of regular gel particles are generated at the bottom. The Na3Mg3 (PO4) 3 crystal can be obtained by carrying out suction filtration and washing on the Na3Mg3 (PO4) 3 with distilled water and then roasting at 600 DEG C for 4 hours, so that the problems that the preparation of the sodium magnesium triphosphate is difficult and the industrial production cannot be realized at present are solved.

Description

Technical Field

[0001] The invention belongs to the field of material research and relates to a method for preparing a sodium magnesium phosphate crystal material. Background Art

[0002] Na3Mg3(PO4)3 is composed of sodium ions (Na + ), magnesium ion (Mg 2+ ) and phosphate ions (PO4 3- ) in which the ions are interconnected by strong chemical bonds to form a stable crystal structure. This compound is usually white or light-colored powder at room temperature and has good chemical and thermal stability. In addition, due to the presence of magnesium ions and phosphate ions, Na3Mg3(PO4)3 also has certain alkalinity and adsorption properties, which make it possible to be used in environmental purification, catalytic reactions and other fields.

[0003] In the field of materials science, Na3Mg3(PO4)3 can be used to prepare high-performance ceramic materials, electronic components, and optical materials. Its stable crystal structure and excellent physical and chemical properties enable these materials to maintain good performance under extreme conditions. In recent years, researchers have found that Na3Mg3(PO4)3 crystals can be used as photocatalytic materials. Na3Mg3(PO4)3 can reduce carbon dioxide (CO2) to carbon monoxide (CO) under simulated sunlight. This technology not only helps to reduce the content of CO2 in the atmosphere and alleviate the greenhouse effect, but also converts waste gas into valuable resources and increases the added value of industrial waste gas. In addition, Na3Mg3(PO4)3 can be used as a catalyst or catalyst carrier to participate in a variety of chemical reactions. The presence of alkaline sites and phosphate ions on its surface makes the compound show excellent activity and selectivity in acid-base catalysis, redox reactions, etc. As a compound with unique chemical composition and properties, Na3Mg3(PO4)3 shows broad application prospects in many fields such as environmental purification, catalytic reactions, and materials science. With the continuous development of science and technology, the research on Na3Mg3(PO4)3 will become more in-depth and its application fields will continue to expand.

[0004] However, there are few technical reports on the chemical synthesis of Na3Mg3(PO4)3, and there are only two related documents. The synthesis method and its crystal structure were first reported in Acta Cryst. (1997). C53, 1733-1735. The researchers placed a mixture of Na2HPO4 and MgSO4·7H2O in a silver tube with a diameter of 3mm and a length of 5cm, and then placed it in an autoclave and heated it to 873K, with an internal pressure of 100MPa. After heat treatment, the temperature was lowered at 1K / 20min, and the crystal product was checked with an electronic microprobe. The preparation is very complicated and has no industrial application value. In addition, a Na3Mg3(PO4)3 / MgO photocatalytic material, preparation method and use, patent number CN110980681A discloses the use of grinding and roasting technology to prepare Na3Mg3(PO4)3 crystals, because its product is affected by factors such as raw material ratio, contact area, roasting conditions, etc., resulting in poor purity and crystallinity. It has been reported that these two methods still face many challenges in practical application, cannot be mass-produced with high quality, and have not formed a set of mature, efficient, and repeatable preparation processes. Therefore, the research on the preparation method of Na3Mg3(PO4)3 crystals is particularly urgent. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a simple, green and environmentally friendly method for preparing Na3Mg3(PO4)3 crystal material.

[0006] The technical solution of the present invention is to prepare Na3Mg3(PO4) crystalline material by a sol-gel-calcination method, comprising the following steps:

[0007] Step 1, preparation of sol: First, prepare an organic phosphorus source (sodium phytate) and a magnesium source (magnesium sulfate, magnesium citrate, magnesium carbonate, magnesium nitrate, magnesium silicate) into aqueous solutions of a certain concentration, mix the two at a certain temperature, adjust the pH value to 7-14, and stir evenly to obtain a white sol.

[0008] Step 2, sol-gel conversion: The sol obtained in step (1) is reacted at a certain temperature. As the reaction time increases, the upper opaque white sol gradually drops, and a clear liquid is obtained at the upper part. After the reaction is completed, the sol becomes completely clear, and a large number of regular, transparent gel particles are generated at the bottom.

[0009] Step 3, washing and drying: the gel particles obtained in step 2 are washed with distilled water for 3 to 4 times, and regular, opaque gel particles are obtained after drying.

[0010] Step 4, high temperature calcination: The gel particles obtained in step 3 are placed in a tubular furnace and calcined to finally obtain Na3Mg3(PO4)3 crystals.

[0011] Preferably, the calcination atmosphere is air or nitrogen atmosphere.

[0012] Preferably, sodium phytate is used as the organic phosphorus source and sodium source, magnesium chloride hexahydrate is used as the magnesium source, and the molar ratio of the phosphorus source to the magnesium source is 1:1.

[0013] Preferably, the initial concentration of the phosphorus source and the magnesium source is 0.1 mol / l.

[0014] Preferably, during the experimental operation, the phosphorus source is dripped into the magnesium source and the dripping is completed within 1 minute.

[0015] Preferably, the starting materials are mixed at room temperature and stirred for 1 min until the mixture is uniform.

[0016] Preferably, the pH of the mixed solution is adjusted to 11.8

[0017] Preferably, the low temperature reaction temperature is 5°C and the reaction time is 5h.

[0018] Preferably, the calcination temperature is 600°C.

[0019] Preferably, the calcination time is 4 hours.

[0020] The beneficial effects achieved by the present invention are: The present invention uses a new preparation method, namely the sol-gel-calcination method, which is not only convenient and simple to operate, but also pollution-free and resource-saving. The prepared Na3Mg3(PO4)3 crystal has extremely high crystallinity, has a broad application prospect, has low requirements on production equipment, and is suitable for industrial mass production.

[0021] The innovative features of the present invention are: This study took advantage of the fact that the organic phosphorus source sodium phytate reacts easily with magnesium chloride hexahydrate to form a sol, and used the sol-gel conversion method to prepare a material with uniform particle size distribution as a reaction precursor at a relatively low temperature. By calcining in a tubular furnace at different atmospheres and temperatures, high-purity sodium trimagnesium phosphate crystalline materials were successfully synthesized. At the same time, by optimizing the experimental conditions, extra-large spindle-shaped sodium trimagnesium phosphate crystals were obtained.

[0022] The study found that the time taken to prepare sodium trimagnesium phosphate by mixing at room temperature is much shorter than that by heating. The main reason is that its sol state is unstable and it is very easy to complete the process of sol aggregation to form transparent gel particles. Since heating can make the gel state more stable, thereby prolonging the sol-gel transition process, the precursor particles will grow further under longer reaction time to form an ultra-large spindle-shaped structure with a length of 3-6mm. After being calcined at 600℃ in a tubular furnace, the spindle shape remains intact and is transformed into an ultra-large sodium magnesium triphosphate crystal. This study successfully prepared sodium trimagnesium phosphate crystal materials of different particle sizes under different experimental conditions, solving the technical problem that the current production conditions of sodium trimagnesium phosphate crystals are complex and cannot be industrialized. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The OM diagrams of the precursors and Na3Mg3(PO4)3 synthesized in Example 1 and Example 7 are shown on the left, and the OM diagram of Na3Mg3(PO4)3 synthesized in Example 7 is shown on the right.

[0025] Figure 2 The precursors synthesized in Examples 1 and 7 were calcined at 300°C for 4h and had XRD spectra of Na3Mg3(PO4)3.

[0026] Figure 3 Schematic diagram of the sol-gel reaction in Example 19.

[0027] Figure 4 This is the SEM image of Na3Mg3(PO4)3 prepared in Example 19.

[0028] Figure 5 The precursors synthesized in Example 13 and Example 19 were calcined at 300°C for 4 hours and the XRD spectrum of Na3Mg3(PO4)3.

[0029] Figure 6 XRD spectra of the precursors synthesized in Example 25 and Example 31 after calcination at 300°C and Na3Mg3(PO4)3.

[0030] Figure 7 This is a flow chart of preparing sodium magnesium phosphate crystals by the sol-gel-calcination method in Example 31.

[0031] Figure 8 This is the XRD spectrum of Na3Mg3(PO4)3 synthesized in Comparative Example 2. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below through embodiments.

[0033] Example 1

[0034] Use 0.1mol / l sodium phytate solution and 0.1mol / l magnesium chloride hexahydrate solution in equal volumes as starting materials. At room temperature, add 20L of sodium phytate solution to an equal volume of magnesium chloride hexahydrate solution. The addition is completed within 1 hour. The pH is measured to be 11.8. Place it in a reactor and stir for 1 minute until the mixed solution is uniform. Place the reactor at 5°C for low temperature reaction for 4-6 hours to generate a large number of regular transparent gel particles. After filtering and washing the particles three times with distilled water, dry them at 80°C for 12 hours to obtain a white powder, which is used as a reaction precursor. The precursor is placed in a quartz boat and calcined in an air atmosphere at 300°C in a tube furnace for 4 hours.

[0035] Embodiment 2-6

[0036] In Examples 2-6, the concentrations of the magnesium source were 0.2 mol / l, 0.3 mol / l, 0.4 mol / l, 0.5 mol / l, and 0.6 mol / l, respectively, and the other reaction conditions were the same as in Example 1.

[0037] Example 7

[0038] Use 0.1mol / l sodium phytate solution and 0.1mol / l magnesium chloride hexahydrate solution in equal volumes as starting materials. At room temperature, add 20L of sodium phytate solution to an equal volume of magnesium chloride hexahydrate solution. The addition is completed within 1 hour. The pH value is measured to be 11.8. Place it in a reactor and stir for 1 minute until the mixed solution is uniform. Place the reactor at 5°C for low temperature reaction for 4-6 hours to generate a large number of regular transparent gel particles. After filtering and washing the particles three times with distilled water, dry them at 80°C for 12 hours to obtain a white powder, which is used as a reaction precursor. The precursor is placed in a quartz boat and calcined in an air atmosphere at 600°C in a tube furnace for 4 hours.

[0039] Figure 1 The OM diagrams of the precursor and Na3Mg3(PO4)3 obtained by calcining the precursor at 600°C in air atmosphere for 4 hours. The left one is the OM diagram of the precursor, and the right one is the OM diagram of Na3Mg3(PO4)3.

[0040] The precursor was calcined in a tube furnace at 300℃ in air atmosphere for 4h and 600℃ in air atmosphere for 4h to obtain powders, which were tested by XRD. The XRD patterns were as follows: Figure 2 ,Depend on Figure 2 It can be seen that the precursor obtained in this example is an amorphous product after being calcined at 300°C for 4 hours in an air atmosphere. After increasing the calcination temperature to 600°C, the crystallinity increases and the product is Na3Mg3(PO4)3 crystals.

[0041] Examples 8-12

[0042] The magnesium source concentrations in Examples 8-12 were 0.2 mol / l, 0.3 mol / l, 0.4 mol / l, 0.5 mol / l, and 0.6 mol / l, respectively, and the other reaction conditions were the same as in Example 7.

[0043] Example 13

[0044] Use 0.1mol / l sodium phytate solution and 0.1mol / l magnesium chloride hexahydrate solution in equal volumes as the starting material. At room temperature, add 20L of sodium phytate solution to an equal volume of magnesium chloride hexahydrate solution. The addition is completed within 1 hour. The mixed solution is placed in a reactor and heated to 80°C. Use a stirrer to stir for 1 hour, n = 300r / min. After the reaction is completed, place the reactor at 5°C for low-temperature reaction for 3-5 days to generate a large number of regular transparent gel particles. The particles are filtered and washed three times with distilled water and dried at 80°C for 12 hours to obtain a white powder, which is used as a reaction precursor. The precursor is placed in a porcelain boat and calcined in an air atmosphere at 300°C in a muffle furnace for 4 hours.

[0045] Embodiment 14

[0046] The magnesium source concentrations in Examples 14-18 were 0.2 mol / l, 0.3 mol / l, 0.4 mol / l, 0.5 mol / l, and 0.6 mol / l, respectively, and the other reaction conditions were the same as in Example 13.

[0047] Embodiment 19

[0048] Use 0.1mol / l sodium phytate solution and 0.1mol / l magnesium chloride hexahydrate solution in equal volumes as the starting material. At room temperature, add 20L of sodium phytate solution to an equal volume of magnesium chloride hexahydrate solution. The addition is completed within 1 hour. The mixed solution is placed in a reactor and heated to 80°C. Use a stirrer to stir for 1 hour, n = 300r / min. After the reaction is completed, place the reactor at 5°C for low temperature reaction for 3-5 days to generate a large number of regular transparent gel particles. The particles are filtered and washed three times with distilled water and dried at 80°C for 12 hours to obtain a white powder, which is used as a reaction precursor. The precursor is placed in a porcelain boat and calcined in an air atmosphere at 600°C in a muffle furnace for 4 hours.

[0049] Figure 3 Schematic diagram of the sol-gel reaction in Example 19.

[0050] Figure 4 This is the SEM image of Na3Mg3(PO4)3 prepared in Example 19.

[0051] The precursor was calcined in a muffle furnace at 300°C in air atmosphere for 4 h and 600°C in air atmosphere for 4 h to obtain powders, which were tested by XRD. The results are as follows: Figure 5 As shown by Figure 5 It can be seen that the crystallinity of the product after calcination at 300°C for 4 hours in an air atmosphere is poor, while the white powder obtained by further increasing the calcination temperature to 600°C has extremely high crystallinity, which is Na3Mg3(PO4)3 crystal.

[0052] Examples 20-24

[0053] The magnesium source concentrations in Examples 20-24 were 0.2 mol / l, 0.3 mol / l, 0.4 mol / l, 0.5 mol / l, and 0.6 mol / l, respectively, and the other reaction conditions were the same as in Example 19.

[0054] Embodiment 25

[0055] Use 0.1mol / l sodium phytate solution and 0.1mol / l magnesium chloride hexahydrate solution in equal volumes as starting materials. At room temperature, add 20L sodium phytate solution to an equal volume of magnesium chloride hexahydrate solution. The addition is completed within 1 hour. The pH is measured to be 11.8. The mixed solution is placed in a reactor and heated to 80°C. Stir with a stirrer for 1 hour, n=300r / min. After the reaction is completed, place the reactor at 5°C for low temperature reaction for 3-5 days to generate a large number of regular transparent gel particles. The particles are filtered and washed three times with distilled water and dried at 80°C for 12 hours to obtain a white powder, which is used as a reaction precursor. The precursor is placed in a quartz boat and calcined in a nitrogen atmosphere at 300°C in a tube furnace for 4 hours.

[0056] Examples 26-30

[0057] The magnesium source concentrations in Examples 26-30 were 0.2 mol / l, 0.3 mol / l, 0.4 mol / l, 0.5 mol / l, and 0.6 mol / l, respectively, and the other reaction conditions were the same as in Example 25.

[0058] Embodiment 31

[0059] Use 0.1mol / l sodium phytate solution and 0.1mol / l magnesium chloride hexahydrate solution in equal volumes as starting materials. At room temperature, add 20L sodium phytate solution to an equal volume of magnesium chloride hexahydrate solution. The addition is completed within 1 hour. The pH is measured to be 11.8. The mixed solution is placed in a reactor and heated to 80°C. Stir with a stirrer for 1 hour, n=300r / min. After the reaction is completed, place the reactor at 5°C for low temperature reaction for 3-5 days to generate a large number of regular transparent particles. The particles are filtered and washed three times with distilled water and dried at 80°C for 12 hours to obtain a white powder, which is used as a reaction precursor. The precursor is placed in a quartz boat and calcined in a nitrogen atmosphere at 600°C in a tube furnace for 4 hours.

[0060] Figure 7This is a flow chart of preparing sodium trimagnesium phosphate by the sol-gel assisted roasting method in Example 31.

[0061] The powders obtained by calcining the precursor at 300℃ in nitrogen atmosphere for 4h and 600℃ in nitrogen atmosphere for 4h were subjected to XRD test respectively, and the XRD patterns were as follows: Figure 6 ,Depend on Figure 6 It can be seen that the crystallinity of the product after calcination at 300°C for 4 hours in a nitrogen atmosphere is poor, while after further increasing the calcination temperature to 600°C, the white powder obtained has extremely high crystallinity and is Na3Mg3(PO4)3 crystal.

[0062] Examples 32-36

[0063] The magnesium source concentrations in Examples 32-36 were 0.2 mol / l, 0.3 mol / l, 0.4 mol / l, 0.5 mol / l, and 0.6 mol / l, respectively, and the other reaction conditions were the same as in Example 31.

[0064] In order to more comprehensively demonstrate the innovation and technical effects of the present invention in the field of material synthesis, a series of comparative examples will be set up below to compare and analyze the technical solution of the present invention with the prior art. Through comparison, it is intended to clarify the significant advantages of the present invention in solving specific technical problems, improving material performance or optimizing synthesis methods. "

[0065] Comparative Example 1

[0066] The synthesis method and its crystal structure were first reported in Acta Cryst. (1997). C53, 1733-1735. The researchers placed a mixture of Na2HPO4 and MgSO4·7H2O in a silver tube with a diameter of 3mm and a length of 5cm, and then placed it in an autoclave and heated it to 873K with an internal pressure of 100MPa. After heat treatment, the temperature was cooled at 1K / 20min, and the crystal product was checked with an electronic microprobe. Finally, sodium trimagnesium phosphate crystal material was obtained. However, it has the disadvantages of harsh reaction conditions, high energy consumption, and inability to be mass-produced.

[0067] Comparative Example 2

[0068] Patent No. CN110980681A reports the use of grinding and roasting technology to prepare Na3Mg3(PO4)3 crystals. The later stage is similar to the present invention in the synthesis route, and both use the roasting method, but the preparation method of the precursor is very different. The purity of the product during the grinding process of this method is greatly reduced due to the influence of factors such as raw material ratio, raw material particle size, and contact area. The present invention uses the sol-gel method to prepare the reaction precursor, and this technical solution shows significant advantages in terms of product yield, purity, crystallinity, etc. Figure 8 This is the XRD spectrum of sodium magnesium phosphate in Comparative Example 2.

[0069] By comparing the above comparative examples with the technical solution of the present invention, it is found that the preparation method of the present invention is simpler and more efficient, the reaction conditions are milder, and the energy consumption and production cost are reduced. At the same time, the present invention reduces the generation of harmful by-products and improves the environmental protection during the synthesis process.

Claims

1. A method for preparing Na3Mg3(PO4)3 crystalline material, characterized in that: The following steps are involved: (1) Preparation of sol: First, an organic phosphorus source (sodium phytate) and a magnesium source (magnesium sulfate, magnesium citrate, magnesium carbonate, magnesium nitrate, magnesium silicate) are respectively prepared into aqueous solutions of a certain concentration, the two are mixed at a certain temperature, the pH value is adjusted to 7-14, and a white sol is obtained after stirring evenly. (2) Sol-gel conversion: The sol obtained in step (1) is reacted at a certain temperature. As the reaction time increases, the upper opaque white sol gradually drops, and a clear liquid is obtained at the upper part. After the reaction is completed, the sol becomes completely clear, and a large number of regular, transparent gel particles are generated at the bottom. (3) Washing and drying: The gel particles obtained in step (2) are washed with distilled water for 3 to 4 times and dried to obtain regular, opaque gel particles. (4) High temperature calcination: The gel particles obtained in step (3) are placed in a tubular furnace and calcined to finally obtain Na3Mg3(PO4)3 crystals.

2. The method for preparing a Na3Mg3(PO4)3 crystalline material according to claim 1, characterized in that: The phosphorus source used in step (1) is sodium phytate, and the magnesium source is magnesium sulfate, magnesium citrate, magnesium carbonate, magnesium nitrate, magnesium silicate, etc.

3. The method for preparing a Na3Mg3(PO4)3 crystalline material according to claim 1, characterized in that: In step (1), sodium hydroxide or aqueous ammonia is used to adjust the pH value.

4. The method for preparing a Na3Mg3(PO4)3 crystalline material according to claim 1, characterized in that: The molar ratio of the phosphorus source to the magnesium source used in step (1) is 1:1 to 10:

1.

5. The method for preparing a Na3Mg3(PO4)3 crystalline material according to claim 1, characterized in that: The mixing temperature of the phosphorus source and the magnesium source in step (1) is 25-120°C.

6. The method for preparing a Na3Mg3(PO4)3 crystalline material according to claim 1, characterized in that: The mixing and stirring time of the phosphorus source and the magnesium source in step (1) is 10s to 6h.

7. The method for preparing a Na3Mg3(PO4)3 crystalline material according to claim 1, characterized in that: In step (2), the reaction temperature is -5 to 25° C., and the reaction time is 2 h to 30 days.

8. The method for preparing a Na3Mg3(PO4)3 crystalline material according to claim 1, characterized in that: The drying temperature in step (3) is 50-80°C.

9. The method for preparing a Na3Mg3(PO4)3 crystalline material according to claim 1, characterized in that: In step (4), the calcination atmosphere is air or nitrogen, and the calcination temperature is 300-800°C.

10. The method for preparing a Na3Mg3(PO4)3 crystalline material according to claim 1, characterized in that: The calcination time in step (4) is 2 to 8 hours.

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