High-purity magnesium oxide and preparation method thereof

Abstract

The invention relates to the technical field of magnesium oxide, and provides high-purity magnesium oxide and a preparation method thereof.The preparation method of the magnesium oxide comprises the following steps that S1, a dispersing agent is added into ammonia water to be mixed, and a mixture is obtained; s2, adding a magnesium chloride solution into the mixture for reaction to obtain magnesium hydroxide; and S3, treating the magnesium hydroxide with an amino compound, and calcining to obtain the high-purity magnesium oxide. According to the technical scheme, the problem of low magnesium oxide purity in related technologies is solved.

Description

Technical Field

[0001] The present invention relates to the technical field, and specifically, to a high-purity magnesium oxide and a preparation method thereof. Background Art

[0002] As an important inorganic chemical product, magnesium oxide has indispensable applications in many fields. In the steel industry, high-purity magnesium oxide is a key raw material for producing high-quality refractory materials, which can significantly improve the high-temperature resistance and corrosion resistance of refractory materials, ensuring the smooth progress of high-temperature processes such as steelmaking; in the electronic field, it is widely used in the manufacture of electronic ceramics, semiconductor materials, etc., playing a key role in optimizing the performance of electronic components; in the pharmaceutical field, high-purity magnesium oxide can be used as an antacid, laxative, etc., and its purity and quality are directly related to the safety and effectiveness of drugs.

[0003] Currently, common methods for preparing magnesium oxide include liquid-phase precipitation method, sol-gel method, alcohol hydrolysis method, etc. Among them, the liquid-phase precipitation method has become the most industrially applicable magnesium oxide technology due to its characteristics such as cheap and easily available raw materials, simple process, stable product performance, and less environmental pollution. However, when preparing nanoparticles by the liquid-phase precipitation method, the problems of grain growth and aggregation inevitably occur, which will ultimately affect the purity of magnesium oxide. Summary of the Invention

[0004] The present invention provides a high-purity magnesium oxide and a preparation method thereof, which solve the problem of low purity of magnesium oxide in the related art.

[0005] The technical solution of the present invention is as follows: The present invention provides a preparation method of high-purity magnesium oxide, comprising the following steps: S1. Adding a dispersant to ammonia water and mixing to obtain a mixture; S2. Adding a magnesium chloride solution to the mixture for reaction to obtain magnesium hydroxide; S3. Treating the magnesium hydroxide with an amino compound and then calcining to obtain high-purity magnesium oxide; As a further technical solution, the dispersant includes one or two of polyethylene glycol and Tween.

[0006] As a further technical solution, the reaction temperature is 30 - 40 °C, and the reaction time is 25 - 35 min.

[0007] As a further technical solution, in step S2, adding a magnesium chloride solution to the mixture for reaction, centrifuging and washing thoroughly until there is no chloride ion, and drying at 120 °C for 2 h to obtain magnesium hydroxide.

[0008] As a further technical solution, the polyethylene glycol includes one or more of polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600, preferably polyethylene glycol 400.

[0009] The dispersant plays a very important role in the preparation process of magnesium hydroxide. The choice of the dispersant directly affects the dispersibility of the particles. Selecting a suitable dispersant can effectively achieve the dispersion of the particles and reduce the agglomeration phenomenon of the particles. An inappropriate dispersant will not only not improve the dispersibility of the particles, but also lead to an increase in the agglomeration phenomenon, resulting in the agglomeration and growth of magnesium hydroxide particles. The agglomerates will include impurities during the agglomeration process and are difficult to clean thoroughly, which will lead to a decrease in the purity of magnesium oxide. When the dispersant is preferably polyethylene glycol 400 in the present invention, the role of the dispersant can be better exerted, and the purity of magnesium hydroxide can be improved, laying a foundation for the subsequent calcination to produce high-purity and highly active magnesium oxide.

[0010] As a further technical solution, the amino compound includes one or more of γ-aminopropyltrimethoxysilane, N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid sodium salt, and tert-butylacrylamidesulfonic acid.

[0011] In the present invention, treating magnesium hydroxide with an amino compound can improve the activity of magnesium oxide. It was found during the experiment that all three amino compounds, γ-aminopropyltrimethoxysilane, N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid sodium salt, and tert-butylacrylamidesulfonic acid, can improve the activity and purity of magnesium oxide.

[0012] As a further technical solution, the amino compound is preferably γ-aminopropyltrimethoxysilane and N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid sodium salt. When the amino compound is composed of γ-aminopropyltrimethoxysilane and N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid sodium salt, the mass ratio of γ-aminopropyltrimethoxysilane to N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid sodium salt is 1 to 3:1.

[0013] In the present invention, the inventor found that when the amino compound is compounded by γ-aminopropyltrimethoxysilane and N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid sodium salt, the activity and purity of magnesium oxide can be further improved. Therefore, the ratio of the two was explored, and it was found that when the mass ratio of γ-aminopropyltrimethoxysilane to N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid sodium salt is 1 to 3:1, a synergistic effect can be achieved, and the effects of the two can be better exerted.

[0014] As a further technical solution, the amino compound is 4% to 6% of the mass of magnesium hydroxide.

[0015] As a further technical solution, in the magnesium chloride solution, Mg2+ The molar concentration is 1 to 2 mol / L.

[0016] As a further technical solution, the preparation process of the magnesium chloride solution includes the following steps: adding MgCl 2 ·6H 2 O into water and mixing evenly to obtain the magnesium chloride solution.

[0017] As a further technical solution, the mass concentration of the ammonia water is 25% to 28%.

[0018] As a further technical solution, the molar ratio of Mg 2+ in the magnesium chloride solution to NH 4 ＋ in the ammonia water is 1:2.5 to 3.5.

[0019] In the present invention, by limiting the molar ratio of Mg 2+ in the magnesium chloride solution to NH 4 ＋ in the ammonia water, it can ensure that the reaction is more complete, improve the degree of the reaction, and convert magnesium ions into magnesium hydroxide precipitation.

[0020] As a further technical solution, the calcination is first carried out at a heating rate of 10 to 20 °C / min to 400 °C for the first-stage calcination, and then at a heating rate of 25 °C / min to 700 °C for the second-stage calcination.

[0021] In the present invention, during the process of calcining magnesium hydroxide to form magnesium oxide, two-stage calcination is adopted. The first stage can remove the moisture and a small amount of impurities on the surface of magnesium hydroxide, and the second stage can fully decompose magnesium hydroxide into magnesium oxide. Through this calcination process, the activity of magnesium oxide can be better improved, so that it has better performance in application fields such as catalysis and adsorption. Moreover, by carrying out the calcination in two stages, it can avoid the huge thermal shock and pressure on the equipment caused by one-time high-temperature calcination, reduce the wear and damage of the equipment, extend the service life of the equipment, and also has a certain degree of safety.

[0022] As a further technical solution, the time for the first-stage calcination is 0.5 to 1 h, and the time for the second-stage calcination is 1.5 to 2 h.

[0023] The present invention also provides high-purity magnesium oxide prepared by the method for preparing high-purity magnesium oxide described above.

[0024] The working principle and beneficial effects of the present invention are as follows: In the present invention, during the preparation process of magnesium hydroxide, the addition of a dispersant can better disperse the reaction system, prevent the aggregation of magnesium hydroxide particles during formation, increase the specific surface area and purity of magnesium hydroxide, enhance the exchange and energy transfer with external substances, and lay a foundation for the subsequent calcination to produce high-purity and active magnesium oxide. Moreover, the dispersant can endow magnesium hydroxide with a more regular structure and more uniform particle size, which is more conducive to heat transfer during the calcination process of magnesium hydroxide and improves the activity of magnesium oxide. After the preparation of magnesium hydroxide, it is treated with an amino compound to modify the surface of magnesium hydroxide, making it easier to undergo lattice transformation and structural adjustment during calcination and improving the activity of magnesium oxide. Detailed implementation mode

[0025] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0026] In the following examples and comparative examples: The measurement method of iodine adsorption value (activity of magnesium oxide) is as follows: Weigh 2 ± 0.05 g of magnesium oxide sample and put it into a 200 mL stoppered glass bottle. Add 100 ± 2 mL of carbon tetrachloride solution containing 0.1 mol / L iodine, stopper the glass bottle, shake for 30 min, let it stand for 5 min, and then pipette 20 mL of the clear solution and place it into 50 mL of ethanol solution containing 0.03 mol / L potassium iodide. Titrate it with a 0.025 mol / L NaS 2 O 3 solution, and calculate the iodine adsorption value using the following formula; Iodine adsorption value = 2.5 × 127 × C × (V 1 - V 2 ); In the formula: C is the concentration of the NaS 2 O 3 solution, V 1 is the volume of the NaS 2 O 3 solution consumed for titrating 20 mL of iodine stock solution in mL, V 2 is the volume of the NaS 2 O 3 solution consumed for titrating 20 mL of iodine solution after contacting the magnesium oxide sample, 127 is the milligram number of iodine equivalent to 1 mL of 0.5 mol / L NaS 2 O 3 solution, and 2.5 is the conversion factor of 1 mg of iodine.

[0027] Example 1 A method for preparing high-purity magnesium oxide, comprising the following steps: S1. Add polyethylene glycol 400 to ammonia water with a mass concentration of 25% and mix to obtain a mixture; S2. Add a 1 mol / L magnesium chloride solution (preparation method: mix MgCl 2 ·6H 2 O and water) to the mixture and react at 30 °C for 35 min, then centrifuge and wash thoroughly until there is no chloride ion, and dry at 120 °C for 2 h to obtain magnesium hydroxide; the molar ratio of Mg 2+ in the magnesium chloride solution to NH 4 ＋ in the ammonia water is 1:2.5; S3. Add magnesium hydroxide to an ethanol solution, add γ-aminopropyltrimethoxysilane, stir at 35 °C for 40 min, and obtain an amino compound composite magnesium hydroxide through filtration and drying; wherein γ-aminopropyltrimethoxysilane is 4% of the mass of magnesium hydroxide; the mass ratio of magnesium hydroxide to ethanol is 1:15; S4. First heat the amino compound composite magnesium hydroxide to 400 °C at a heating rate of 10 °C / min and calcine for 1 h, then heat it to 700 °C at a heating rate of 20 °C / min and calcine for 2 h, and pulverize to obtain high-purity magnesium oxide with an average particle size of 15 nm; measurement results: purity 98.5%, iodine adsorption value 135 mgI / g.

[0028] Example 2 A method for preparing high-purity magnesium oxide, comprising the following steps: S1. Add polyethylene glycol 400 to ammonia water with a mass concentration of 25% and mix to obtain a mixture; S2. Add a 2 mol / L magnesium chloride solution (preparation method: mix MgCl 2 ·6H 2 O and water) to the mixture and react at 40 °C for 25 min, then centrifuge and wash thoroughly until there is no chloride ion, and dry at 120 °C for 2 h to obtain magnesium hydroxide; the molar ratio of Mg 2+ in the magnesium chloride solution to NH 4 ＋ in the ammonia water is 1:3.5; S3. Add magnesium hydroxide to an ethanol solution, add γ-aminopropyltrimethoxysilane, stir at 35 °C for 40 min, and obtain an amino compound composite magnesium hydroxide through filtration and drying; wherein γ-aminopropyltrimethoxysilane is 6% of the mass of magnesium hydroxide; the mass ratio of magnesium hydroxide to ethanol is 1:15; S4. First, heat the amino compound - magnesium hydroxide composite to 400 °C at a heating rate of 10 °C / min and calcine for 1 h, then heat it to 700 °C at a heating rate of 20 °C / min and calcine for 2 h, and then pulverize it to obtain high - purity magnesium oxide with an average particle size of 15 nm. Measurement results: purity 98.7%, iodine adsorption value 132 mgI / g.

[0029] Example 3 Compared with Example 1, the difference in this example is only that γ - aminopropyltrimethoxysilane is replaced with an equal amount of N,N - bis(2 - hydroxyethyl)-2 - aminoethanesulfonic acid sodium salt. Measurement results: purity 98.4%, iodine adsorption value 128 mgI / g.

[0030] Example 4 Compared with Example 1, the difference in this example is only that γ - aminopropyltrimethoxysilane is completely replaced with a mixture of γ - aminopropyltrimethoxysilane and N,N - bis(2 - hydroxyethyl)-2 - aminoethanesulfonic acid sodium salt with a mass ratio of 1:1. Measurement results: purity 99.2%, iodine adsorption value 141 mgI / g.

[0031] Example 5 Compared with Example 1, the difference in this example is only that γ - aminopropyltrimethoxysilane is completely replaced with a mixture of γ - aminopropyltrimethoxysilane and N,N - bis(2 - hydroxyethyl)-2 - aminoethanesulfonic acid sodium salt with a mass ratio of 2:1. Measurement results: purity 99.6%, iodine adsorption value 149 mgI / g.

[0032] Example 6 Compared with Example 1, the difference in this example is only that γ - aminopropyltrimethoxysilane is completely replaced with a mixture of γ - aminopropyltrimethoxysilane and N,N - bis(2 - hydroxyethyl)-2 - aminoethanesulfonic acid sodium salt with a mass ratio of 3:1. Measurement results: purity 99.3%, iodine adsorption value 143 mgI / g.

[0033] Example 7 Compared with Example 5, the difference in this example is only that N,N - bis(2 - hydroxyethyl)-2 - aminoethanesulfonic acid sodium salt is replaced with an equal amount of tert - butylacrylamide sulfonic acid. Measurement results: purity 99.0%, iodine adsorption value 140 mgI / g.

[0034] Example 8 Compared with Example 5, the difference in this example is only in step S4. In this example, step S4 is as follows: First, heat the amino compound - magnesium hydroxide composite to 700 °C at a heating rate of 20 °C / min and calcine for 3 h, and then pulverize it to obtain high - purity magnesium oxide with an average particle size of 15 nm. Measurement results: purity 98.9%, iodine adsorption value 138 mgI / g.

[0035] Example 9 Compared with Example 5, the difference in this example lies only in step S4. In this example, step S4 is as follows: First, heat the amino compound-magnesium hydroxide composite to 400 °C at a heating rate of 15 °C / min and calcine for 1 h, then heat it to 700 °C at a heating rate of 20 °C / min and calcine for 2 h, and then pulverize to obtain high-purity magnesium oxide with an average particle size of 15 nm; the measurement results are as follows: purity 99.5%, iodine adsorption value 156 mgI / g.

[0036] Example 10 Compared with Example 5, the difference in this example lies only in step S4. In this example, step S4 is as follows: First, heat the amino compound-magnesium hydroxide composite to 400 °C at a heating rate of 20 °C / min and calcine for 1 h, then heat it to 700 °C at a heating rate of 20 °C / min and calcine for 2 h, and then pulverize to obtain high-purity magnesium oxide with an average particle size of 15 nm; the measurement results are as follows: purity 99.2%, iodine adsorption value 152 mgI / g.

[0037] Example 11 Compared with Example 9, the difference in this example lies only in step S4. In this example, step S4 is as follows: First, heat the amino compound-magnesium hydroxide composite to 400 °C at a heating rate of 15 °C / min and calcine for 1 h, then heat it to 700 °C at a heating rate of 25 °C / min and calcine for 2 h, and then pulverize to obtain high-purity magnesium oxide with an average particle size of 15 nm; the measurement results are as follows: purity 99.7%, iodine adsorption value 162 mgI / g.

[0038] Example 12 Compared with Example 9, the difference in this example lies only in step S4. In this example, step S4 is as follows: First, heat the amino compound-magnesium hydroxide composite to 400 °C at a heating rate of 15 °C / min and calcine for 1 h, then heat it to 700 °C at a heating rate of 30 °C / min and calcine for 2 h, and then pulverize to obtain high-purity magnesium oxide with an average particle size of 15 nm; the measurement results are as follows: purity 99.3%, iodine adsorption value 158 mgI / g.

[0039] Example 13 Compared with Example 11, the difference in this example lies only in step S4. In this example, step S4 is as follows: First, heat the amino compound-magnesium hydroxide composite to 600 °C at a heating rate of 15 °C / min and calcine for 1 h, then heat it to 700 °C at a heating rate of 25 °C / min and calcine for 2 h, and then pulverize to obtain high-purity magnesium oxide with an average particle size of 15 nm; the measurement results are as follows: purity 99.1%, iodine adsorption value 151 mgI / g.

[0040] Comparative Example 1 A method for preparing high-purity magnesium oxide, comprising the following steps: S1. Add polyethylene glycol 400 to ammonia water with a mass concentration of 25% and mix to obtain a mixture; S2. Add 1 mol / L magnesium chloride solution (preparation method: mix MgCl 2 ·6H 2 O and water) to the mixture and react at 30 °C for 25 min, then centrifuge and wash thoroughly until there is no chloride ion, and dry at 120 °C for 2 h to obtain magnesium hydroxide; the molar ratio of Mg 2+ in the magnesium chloride solution to NH 4 ＋ in the ammonia water is 1:2.5; S3. First heat magnesium hydroxide to 400 °C at a heating rate of 10 °C / min and calcine for 1 h, then heat to 700 °C at a heating rate of 20 °C / min and calcine for 2 h, and then pulverize to obtain high-purity magnesium oxide with an average particle size of 15 nm; measurement results: purity 97.2%, iodine adsorption value 120 mgI / g.

[0041] In Examples 1 to 13 of the present invention, the iodine adsorption value can reach more than 128 mgI / g, which is higher than that of Comparative Example 1; the purity of magnesium oxide in Examples 1 to 13 is greater than 98.5%, indicating that the magnesium oxide prepared by the present invention has excellent purity and activity.

[0042] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing high-purity magnesium oxide, characterized in that: The following steps are involved: S1, adding a dispersant into aqueous ammonia and mixing to obtain a mixture; S2, adding magnesium chloride solution to the mixture to react to obtain magnesium hydroxide; S3, treating the magnesium hydroxide with an amino compound and then calcining it to obtain high-purity magnesium oxide.

2. The method for preparing high-purity magnesium oxide according to claim 1, characterized in that: The dispersant includes one or both of polyethylene glycol and Tween.

3. The method for preparing high-purity magnesium oxide according to claim 2, characterized in that: The amino compound includes one or more of γ-aminopropyltrimethoxysilane, sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate, and tert-butylacrylamidesulfonic acid.

4. The method for preparing high-purity magnesium oxide according to claim 1, characterized in that: The magnesium chloride solution contains Mg 2+ The molar concentration is 1~2mol / L.

5. The method for preparing high-purity magnesium oxide according to claim 1, characterized in that: The preparation process of the magnesium chloride solution comprises the following steps: adding MgCl2·6H2O into water and mixing evenly to obtain the magnesium chloride solution.

6. The method for preparing high-purity magnesium oxide according to claim 1, characterized in that: The mass concentration of the ammonia water is 25% to 28%.

7. The method for preparing high-purity magnesium oxide according to claim 1, characterized in that: The magnesium chloride solution contains Mg 2+ With ammonia NH4 ＋ The molar ratio is 1:2.5~3.

5.

8. The method for preparing high-purity magnesium oxide according to claim 1, characterized in that: In step S3, the calcination is firstly carried out by heating the temperature to 400°C at a heating rate of 10-20°C / min for a first stage of calcination and then by heating the temperature to 700°C at a heating rate of 25°C / min for a second stage of calcination.

9. The method for preparing high-purity magnesium oxide according to claim 8, characterized in that: In step S2, the first stage calcination time is 0.5-1 h, and the second stage calcination time is 1.5-2 h.

10. High-purity magnesium oxide prepared according to the method for preparing high-purity magnesium oxide according to any one of claims 1 to 9.