A method for preparing highly active magnesium oxide

Abstract

This invention provides a method for preparing highly active magnesium oxide, relating to the field of magnesium metal oxide synthesis. The preparation method includes the following steps: (1) adjusting the pH of magnesium chloride filtrate and adding hydrogen peroxide for oxidation; the magnesium chloride filtrate includes magnesium oxide, 5-ethyl-2(5H)-furanone, furfural, and water; (2) adding activated carbon, stirring, and filtering to obtain a mother liquor, adding ammonia water to the mother liquor, stirring, and filtering to obtain crude magnesium hydroxide product one; (3) adding crude magnesium hydroxide product one to water containing polypropylene glycol, washing with water, and filtering to obtain crude magnesium hydroxide product two; (4) washing, filtering, drying, grinding, sieving, and calcining the crude magnesium hydroxide product two to obtain the final product. This preparation method has low energy consumption and can prepare highly active magnesium oxide with excellent performance.

Description

Technical Field

[0001] This invention relates to the field of magnesium metal oxide synthesis, and more specifically to a method for preparing highly active magnesium oxide. Background Technology

[0002] Activated magnesium oxide (MgO) is an important raw material for preparing high-performance fine inorganic materials, electronic components, inks, and harmful gas adsorbents. It holds promise for development into cutting-edge materials for harsh conditions such as high temperature and high corrosion. It can also be used as a filler in paints, paper, and cosmetics; a filler and reinforcing agent in plastics and rubber; and an auxiliary material in various electronic materials. Activated magnesium oxide has a wide range of applications and is classified into many different types based on its application. It is primarily classified according to its iodine adsorption value, into three categories: high activity (120–180), medium activity (50–80), and low activity (19–43). In recent years, the demand for activated magnesium oxide has increased, but currently, most magnesium chloride production still uses traditional equipment and processes to produce activated magnesium oxide, leading to unstable product quality.

[0003] Currently, patents related to highly active magnesium oxide include CN114195410A, CN113149042A, CN106082289A, and CN112028093A. The processing methods in these patents all involve low-temperature calcination and grinding of the raw materials, followed by high-temperature calcination. These methods require 2-3 calcination cycles, resulting in significant energy consumption.

[0004] Given the high energy consumption of existing methods for preparing highly active magnesium oxide, it is essential to find a method that is both energy-efficient and yields highly active magnesium oxide. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by providing a method for preparing highly active magnesium oxide. This method has low energy consumption and can produce highly active magnesium oxide with excellent performance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a method for preparing magnesium oxide, comprising the following steps:

[0008] (1) Adjust the pH of the magnesium chloride filtrate and add hydrogen peroxide to oxidize it; the magnesium chloride filtrate includes magnesium oxide, 5-ethyl-2(5H)-furanone, furfural and water;

[0009] (2) Add activated carbon, stir, and filter to obtain mother liquor. Add ammonia water to the mother liquor, stir, and filter to obtain crude magnesium hydroxide product 1.

[0010] (3) Add crude magnesium hydroxide product one to water containing polypropylene glycol, wash with water, filter, and obtain crude magnesium hydroxide product two;

[0011] (4) The crude magnesium hydroxide is washed with water, filtered, dried, ground, sieved and calcined to obtain the product.

[0012] Further, by weight percentage, the magnesium oxide filtrate comprises 20.5-40.5% magnesium chloride, 0.5%-3% 5-ethyl-2(5H)-furanone, 1%-5% furfural, 55%-75% water, and the balance being impurities.

[0013] Preferably, the magnesium oxide filtrate comprises, by weight percentage, 20.5-40.5% magnesium chloride, 0.5%-2.43% 5-ethyl-2(5H)-furanone, 1.82%-3.01% furfural, 55%-75% water, and the balance being impurities.

[0014] Furthermore, the temperature of the magnesium oxide filtrate in step (1) is 70-90℃; and the pH is 2-4.

[0015] Further, in step (1), the volume ratio of hydrogen peroxide to magnesium oxide filtrate is (0.04-0.1):1; the oxidation time is 4-6 hours and the temperature is 50-80℃.

[0016] Further, in step (2), the amount of ammonia water used is to be added dropwise until the pH of the mother liquor is 11-13; the stirring time is 0.5-1h, and the stirring temperature is room temperature to 40℃.

[0017] Further, in step (3), the average molecular weight of the polypropylene glycol is 400, and the amount added is 0.1-0.5% of the weight of the crude magnesium hydroxide; the weight ratio of the crude magnesium hydroxide to water is 1:(1-4); the water washing time is 5-10 min, and the water washing temperature is room temperature to 60°C.

[0018] Furthermore, the number of water washings in step (4) is more than 2 times; the weight ratio of water to crude magnesium hydroxide used in a single water washing is 1:(1-4), and the time is 5-10 minutes.

[0019] Furthermore, the drying temperature in step (4) is 80-110℃, and the moisture content of the crude magnesium hydroxide obtained after drying is 0.1-0.5wt%; the mesh size of the sieve used for sieving is 100-200 mesh.

[0020] Furthermore, the calcination temperature in step (4) is 550-700℃ and the time is 1-3h.

[0021] Preferably, the calcination temperature in step (4) is 650°C and the time is 1.5h.

[0022] Furthermore, the present invention provides magnesium oxide prepared by the above-described preparation method.

[0023] The technical effects achieved by this invention are:

[0024] 1. Hydrogen peroxide is used for oxidation in this invention because hydrogen peroxide has a good oxidation effect, does not introduce other ions, and can be easily removed in subsequent processing.

[0025] 2. The activated carbon used in this invention is waste activated carbon, which is used to adsorb the oily substance generated in magnesium hydroxide filtrate under acidic conditions, facilitating subsequent filtration. This reuse of waste activated carbon realizes its secondary value and promotes the rational utilization of resources.

[0026] 3. In this invention, the recrystallization of solid magnesium hydroxide uses a reverse precipitation method. Traditional processes typically involve adding ammonia to the magnesium hydroxide filtrate to precipitate the solid magnesium hydroxide. This method, however, involves adding the magnesium hydroxide filtrate dropwise to the ammonia solution to precipitate the solid magnesium hydroxide. The magnesium hydroxide particles produced by this reverse precipitation method are smaller, resulting in better washing in subsequent washing steps. During calcination, the organic matter is fully calcined, leading to higher activity and content of the resulting highly active magnesium oxide.

[0027] 3. In this invention, a small amount of polypropylene glycol is added to the pure water during the first water washing of magnesium hydroxide solid. The purpose of this is to use the low molecular weight polypropylene glycol to cause the hydrophilic organic matter in the magnesium hydroxide to aggregate and separate from the magnesium hydroxide solid. After filtration, the content of organic matter and chloride ions in the obtained magnesium hydroxide solid is greatly reduced. Subsequent two water washes remove the polypropylene glycol from the magnesium hydroxide. The final magnesium hydroxide has a low organic matter content, and high-activity magnesium oxide can be obtained by calcination at a lower temperature. This reduces energy consumption.

[0028] 4. The present invention discloses a method for producing highly active magnesium oxide. Through a targeted process, magnesium hydroxide waste generated in the ethyl maltol process is processed into high-quality magnesium oxide followed by magnesium chloride filtrate. This filtrate is subsequently treated as wastewater and is now used as a raw material for highly active magnesium oxide, transforming it into a high-value, highly active magnesium oxide product. On the one hand, this method effectively solves the problem of magnesium hydroxide waste generated in the production of high-quality magnesium oxide, which is difficult to treat effectively and requires significant time and money to be spent on wastewater treatment, increasing the burden on the company. On the other hand, the magnesium hydroxide waste generated in the production of high-quality magnesium oxide is an extremely inexpensive raw material, and the resulting highly active magnesium oxide has high product value, meeting the magnesium oxide demand in high-end fields and demonstrating outstanding economic value. Detailed Implementation

[0029] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0030] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention.

[0031] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0032] It is worth noting that the raw materials used in this invention are all commercially available products, and therefore their sources are not specifically limited.

[0033] Example 1

[0034] The main components of the magnesium chloride filtrate used in Example 1 are shown in Table 1:

[0035] Table 1. Composition of Magnesium Chloride Filtrate

[0036]

[0037]

[0038] For the magnesium chloride filtrate in Table 1, follow these steps.

[0039] Pour 1L of magnesium chloride filtrate into a beaker, add sulfuric acid to adjust the pH of the magnesium hydroxide filtrate to about 3, and add 50 ml of hydrogen peroxide for oxidation; oxidize for 5 hours, keeping the solution temperature at 60℃ during oxidation.

[0040] After oxidation, 0.5g of activated carbon was added and stirred for 15 minutes, then filtered. The mother liquor after oxidation was added dropwise to ammonia water while stirring, maintaining the pH of the mixture at 12 during the addition. Magnesium hydroxide solid precipitated. Filtered. 291.83g of crude magnesium hydroxide was obtained. Crude magnesium hydroxide was poured into 720mL of pure water containing 1.0g of polypropylene glycol with an average molecular weight of 400, washed with water at room temperature for 10 minutes, and filtered after the first wash to obtain 290.00g of crude magnesium hydroxide.

[0041] The crude magnesium hydroxide product II was poured into 660 mL of pure water and washed for 10 min. After the second washing, it was filtered to obtain 289.01 g of crude magnesium hydroxide product III.

[0042] The crude magnesium hydroxide product III was poured into 660 mL of pure water, washed with water for 10 min, washed three times, filtered, and 289.03 g of crude magnesium hydroxide product IV was obtained.

[0043] The crude magnesium hydroxide was dried, and the moisture content of the magnesium hydroxide after drying was 0.2%. The sample was then ground and sieved through a 120-mesh sieve.

[0044] The crude magnesium hydroxide, after sieving, was calcined in a rotary tube furnace at 650°C for 1.5 hours. After calcination, 196.00 g of highly active magnesium oxide was obtained.

[0045] The prepared magnesium oxide was tested, and the results are shown in Table 2.

[0046] Table 2. Properties of the prepared highly active magnesium oxide

[0047]

[0048]

[0049] Example 2

[0050] The main components of the magnesium chloride filtrate used in Example 2 are shown in Table 3:

[0051] Table 3. Composition of Magnesium Chloride Filtrate

[0052] Serial Number Components weight percentage 1 magnesium chloride content 20.5％ 2 Water content 75.0％ 3 5-Ethyl-2(5H)-furanone 0.50％ 4 furfural 3.01％ 5 Other impurities 0.99％

[0053] For the magnesium chloride filtrate in Table 3, follow these steps.

[0054] Pour 1L of magnesium chloride filtrate into a beaker, add sulfuric acid to adjust the pH of the magnesium hydroxide filtrate to about 3, and add 50 ml of hydrogen peroxide for oxidation; oxidize for 5 hours, keeping the solution temperature at 60℃ during oxidation.

[0055] After oxidation, 0.5g of activated carbon was added and stirred for 15 minutes, then filtered. The mother liquor after oxidation was added dropwise to ammonia water while stirring, maintaining the pH of the mixture at 12 during the addition. Magnesium hydroxide solid precipitated. Filtered. 171.45g of crude magnesium hydroxide was obtained. Crude magnesium hydroxide was poured into 720mL of pure water containing 0.86g of polypropylene glycol with an average molecular weight of 400, washed with water at room temperature for 10 minutes, and filtered after one wash to obtain 170.37g of crude magnesium hydroxide.

[0056] The crude magnesium hydroxide product II was poured into 660 mL of pure water and washed for 10 min. After the second washing, it was filtered to obtain 169.28 g of crude magnesium hydroxide product III.

[0057] The crude magnesium hydroxide product III was poured into 660 mL of pure water, washed for 10 min, washed three times, filtered, and 169.20 g of crude magnesium hydroxide product IV was obtained.

[0058] The crude magnesium hydroxide was dried, and the moisture content of the magnesium hydroxide after drying was 0.2%. The sample was then ground and sieved through a 120-mesh sieve.

[0059] The crude magnesium hydroxide, after sieving, was calcined in a rotary tube furnace at 650°C for 1.5 hours. After calcination, 118.84 g of highly active magnesium oxide was obtained.

[0060] The prepared magnesium oxide was tested, and the results are shown in Table 4.

[0061] Table 4. Properties of the prepared highly active magnesium oxide

[0062] Serial Number Components content 1 Iodine uptake value <![CDATA[161.09mgI2 / gMgO <!-- 4 -->]]> 2 magnesium oxide content 89.07％ 3 Chloride ion content 0.08％ 4 Bulk density 0.21g / mL 5 Water content 0.03％

[0063] Example 3

[0064] The main components of the magnesium chloride filtrate used in Example 3 are shown in Table 5:

[0065] Table 5. Composition of Magnesium Chloride Filtrate

[0066] Serial Number Components weight percentage 1 magnesium chloride content 40.50％ 2 Water content 55.00％ 3 5-Ethyl-2(5H)-furanone 2.43％ 4 furfural 1.82％ 5 Other impurities 0.25％

[0067] For the magnesium chloride filtrate in Table 5, follow the steps below.

[0068] Take 1L of magnesium chloride filtrate into a beaker, add sulfuric acid to adjust the pH of the magnesium hydroxide filtrate to about 3, add 50 mL of hydrogen peroxide for oxidation; oxidize for 5 hours, keeping the solution temperature at 60℃ during oxidation.

[0069] After oxidation, 0.5g of activated carbon was added and stirred for 15 minutes, then filtered. The mother liquor after oxidation was added dropwise to ammonia water while stirring, maintaining the pH of the mixture ≥ 12 during the addition. Magnesium hydroxide solid precipitated. Filtered. 358.35g of crude magnesium hydroxide was obtained. Crude magnesium hydroxide was poured into 720mL of pure water containing 0.36g of polypropylene glycol with an average molecular weight of 400, washed with water at room temperature for 10 minutes, and filtered after the first wash to obtain 358.01g of crude magnesium hydroxide.

[0070] The crude magnesium hydroxide product II was poured into 660 mL of pure water and washed for 10 min. After the second washing, it was filtered to obtain 357.89 g of crude magnesium hydroxide product III.

[0071] The crude magnesium hydroxide product III was poured into 660 mL of pure water, washed for 10 min, washed three times, filtered, and 356.98 g of crude magnesium hydroxide product IV was obtained.

[0072] The crude magnesium hydroxide was dried, and the moisture content of the magnesium hydroxide after drying was 0.2%. The sample was then ground and sieved through a 120-mesh sieve.

[0073] The crude magnesium hydroxide, after sieving, was calcined in a rotary tube furnace at 650°C for 1.5 hours. After calcination, 234.37 g of highly active magnesium oxide was obtained.

[0074] The prepared magnesium oxide was tested, and the results are shown in Table 6.

[0075] Table 6. Properties of the prepared highly active magnesium oxide

[0076] Serial Number Components content 1 Iodine uptake value <![CDATA[154.66mgI2 / gMgO]]> 2 magnesium oxide content 88.92％ 3 Chloride ion content 0.09％ 4 Bulk density 0.22g / mL 5 Water content 0.04％

[0077] This application obtains highly active magnesium oxide and magnesium hydroxide filtrate through oxidation, recrystallization, water washing, drying, and calcination, which can be reused to create secondary value and further improve the economic benefits of this method.

[0078] Comparative Example 1 (Unoxidized)

[0079] The magnesium chloride filtrate used in Comparative Example 1 was the same as that used in Example 1. Comparative Example 1 was operated according to the following steps:

[0080] Take 1 L of magnesium chloride filtrate, add 0.5 g of activated carbon and stir for 15 min, filter, then add the filtrate dropwise to ammonia water while stirring, maintaining the pH of the mixture at 12 during the addition. Magnesium hydroxide solid precipitates. Filter. 292.15 g of crude magnesium hydroxide I is obtained; pour crude magnesium hydroxide I into 720 mL of pure water, wash with water at room temperature for 10 min, after one wash, filter to obtain 292.00 g of crude magnesium hydroxide II;

[0081] The crude magnesium hydroxide product II was poured into 660 mL of pure water and washed at room temperature for 10 min. After the second washing, it was filtered to obtain 291.56 g of crude magnesium hydroxide product III.

[0082] The crude magnesium hydroxide product III was poured into 660 mL of pure water and washed for 10 min. After three washes, it was filtered to obtain 291.23 g of crude magnesium hydroxide product IV.

[0083] The crude magnesium hydroxide was dried, and the moisture content of the magnesium hydroxide after drying was 0.2%. The sample was then ground and sieved through a 120-mesh sieve.

[0084] The crude magnesium hydroxide, after sieving, was calcined in a rotary tube furnace at 650°C for 1.5 hours. After calcination, 190.95 g of highly active magnesium oxide was obtained.

[0085] The prepared magnesium oxide was tested, and the results are shown in Table 7.

[0086] Table 7 Properties of the prepared highly active magnesium oxide

[0087] Serial Number Components content 1 Iodine uptake value <![CDATA[107.61mgI2 / gMgO]]> 2 magnesium oxide content 87.69％ 3 Chloride ion content 0.13％ 4 Bulk density 0.25g / mL 5 Water content 0.07％

[0088] Comparative Example 2 (Original Process in the Workshop)

[0089] The magnesium chloride filtrate used in Comparative Example 2 was the same as that used in Example 1. Comparative Example 2 was operated according to the following steps:

[0090] Pour 1 L of magnesium chloride filtrate into a beaker and add it dropwise to ammonia water while stirring. Maintain the pH of the mixture at 12 during the addition. Solid magnesium hydroxide precipitates. Filter. 291.54 g of crude magnesium hydroxide is obtained.

[0091] The crude magnesium hydroxide was dried, and the moisture content of the magnesium hydroxide after drying was 0.6%. The sample was then ground and sieved through a 120-mesh sieve.

[0092] The crude magnesium hydroxide, after sieving, was calcined in a rotary tube furnace at 800℃ for 2 hours. After calcination, 195.05 g of active magnesium oxide was obtained.

[0093] The prepared magnesium oxide was tested, and the results are shown in Table 8.

[0094] Table 8. Properties of the prepared highly active magnesium oxide

[0095] Serial Number Components content 1 Iodine uptake value <![CDATA[57.69mgI2 / gMgO]]> 2 magnesium oxide content 90.13％ 3 Chloride ion content 0.76％ 4 Bulk density 0.46g / mL 5 Water content 0.09％

[0096] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing magnesium oxide, characterized in that: Includes the following steps: (1) Adjust the pH of the magnesium chloride filtrate and add hydrogen peroxide for oxidation; the magnesium chloride filtrate includes magnesium oxide, 5-ethyl-2(5H)-furanone, furfural and water; the temperature of the magnesium oxide filtrate is 70-90℃; the pH is 2-4; the volume ratio of hydrogen peroxide to magnesium oxide filtrate is (0.04-0.1):1; the oxidation time is 4-6h and the temperature is 50-80℃; (2) Add activated carbon, stir, and filter to obtain mother liquor. Add ammonia water to the mother liquor, stir, and filter to obtain crude magnesium hydroxide product 1. (3) Add crude magnesium hydroxide product one to water containing polypropylene glycol, wash with water, filter, and obtain crude magnesium hydroxide product two; the average molecular weight of the polypropylene glycol is 400, and the amount added is 0.1-0.5% of the weight of crude magnesium hydroxide product one; the weight ratio of crude magnesium hydroxide product one to water is 1:(1-4); the washing time is 5-10 min, and the washing temperature is room temperature to 60℃; (4) The crude magnesium hydroxide is washed with dihydrate, filtered, dried, ground, sieved and calcined to obtain the product; The magnesium oxide filtrate comprises, by weight percentage, 20.5-40.5% magnesium chloride, 0.5%-3% 5-ethyl-2(5H)-furanone, 1%-5% furfural, 55%-75% water, and the balance being impurities.

2. The preparation method according to claim 1, characterized in that: In step (2), the amount of ammonia water used is to be added dropwise until the pH of the mother liquor is 11-13; the stirring time is 0.5-1h, and the stirring temperature is room temperature to 40℃.

3. The preparation method according to claim 1, characterized in that: The number of water washes in step (4) is more than 2; the weight ratio of water to crude magnesium hydroxide used in a single water wash is 1:(1-4), and the time is 5-10 min.

4. The preparation method according to claim 1, characterized in that: The drying temperature in step (4) is 80-110℃, and the water content of the crude magnesium hydroxide obtained after drying is 0.1-0.5 wt%; the mesh size of the sieve used for sieving is 100-200 mesh.

5. The preparation method according to claim 1, characterized in that: The calcination temperature in step (4) is 550-700℃ and the time is 1-3h.

6. Magnesium oxide prepared by the preparation method according to any one of claims 1-5.

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