Method for synthesizing magnesium-aluminum hydrotalcite

Abstract

This invention discloses a method for synthesizing magnesium aluminum hydrotalcite, comprising the following steps: (1) mixing magnesium oxide, magnesium bicarbonate, aluminum hydroxide, and sodium hydroxide, then adding an ethanol aqueous solution for wetting and grinding; (2) gradually increasing the temperature while grinding, and then maintaining the temperature for reaction; (3) after the reaction is completed, restoring to room temperature, filtering, washing with water, and drying to obtain magnesium aluminum hydrotalcite. The magnesium aluminum hydrotalcite obtained by this invention has high crystallinity, small particle size and good particle size dispersion, high purity, no impurities, and high yield.

Description

Technical Field

[0001] This invention relates to a method for synthesizing magnesium aluminum hydrotalcite, belonging to the field of hydrotalcite technology. Background Technology

[0002] Hydrotalcite compounds, also known as layered bimetallic hydroxides, are anionic layered compounds. A typical hydrotalcite is magnesium aluminum carbonate hydrotalcite, which has good thermal stability, flame retardancy, and UV resistance, and is widely used in plastics, rubber, glass and other fields.

[0003] Methods for preparing hydrotalcite compounds include coprecipitation, ion exchange, hydrothermal methods, calcination recovery, and nucleation / crystallization separation. However, existing technologies have certain shortcomings: In coprecipitation, nucleation and crystallization occur simultaneously, resulting in a wide particle size distribution and irregular particle size, as well as generating a large amount of byproducts and wastewater, leading to high costs; ion exchange is complex and time-consuming; hydrothermal methods generate a large amount of wastewater and have low yields; calcination recovery requires high-temperature calcination, resulting in large equipment investments and complex processes; nucleation / crystallization separation requires specially designed equipment, increasing the complexity of the process, and requires strict control of the reaction concentration, as excessively high concentrations significantly reduce the purity of the hydrotalcite. Summary of the Invention

[0004] To address at least one problem existing in the prior art, the present invention provides a method for synthesizing magnesium aluminum hydrotalcite, which yields magnesium aluminum hydrotalcite with high crystallinity, small particle size and good particle size dispersion, high purity, no impurities, and high yield.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for synthesizing magnesium aluminum hydrotalcite, comprising the following steps:

[0006] (1) Mix magnesium oxide, magnesium bicarbonate, aluminum hydroxide and sodium hydroxide, then add an ethanol aqueous solution to moisten and grind for 20-30 minutes;

[0007] (2) Continue grinding, gradually increase the temperature, and keep warm to complete the reaction;

[0008] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed with water, and dried to obtain magnesium aluminum hydrotalcite.

[0009] Preferably, in step (1), magnesium oxide, magnesium bicarbonate, aluminum hydroxide, and sodium hydroxide are mixed in a molar ratio of 2:1:1:3.

[0010] Preferably, in step (1), the amount of ethanol aqueous solution added is 1 to 2 times the weight of magnesium oxide.

[0011] Preferably, in step (1), the mass fraction of the ethanol aqueous solution is 70-80%, which is beneficial to improving the particle size uniformity of the product during grinding.

[0012] Preferably, in steps (1) and (2), the grinding speed is 300-500 r / min.

[0013] Preferably, in step (2), the temperature is gradually increased to 75-85°C and the reaction is maintained for 1-1.5 hours.

[0014] In step (2), the rate of gradual heating is 0.5 to 1 °C / min.

[0015] Preferably, in step (3), the water is washed 2 to 3 times, and the amount of pure water used each time is 2 to 3 times that of the ethanol aqueous solution.

[0016] Preferably, in step (3), the drying temperature is 90-100℃ for 6-8 hours.

[0017] Preferably, in step (3), the product is ground during the drying process, once every 2 to 3 hours, to avoid drying agglomeration, which helps to improve the crystallinity of the product and further improve the particle size uniformity of the product.

[0018] Preferably, in step (1), the purity of magnesium oxide is ≥98%.

[0019] Preferably, in step (1), the purity of magnesium bicarbonate is ≥98%.

[0020] Preferably, in step (1), the purity of aluminum hydroxide is ≥99%.

[0021] The beneficial effects of this invention are as follows: The method for synthesizing magnesium-aluminum hydrotalcite of this invention uses magnesium oxide, magnesium bicarbonate, aluminum hydroxide, and sodium hydroxide as raw materials. It does not require carbon dioxide to provide a carbonate source. Under suitable grinding and temperature conditions, magnesium oxide, magnesium bicarbonate, and aluminum hydroxide are all converted into hydrotalcite, achieving maximum atom economy. Simultaneously, it produces fewer byproducts, has high yield, low cost, and stable product quality. The magnesium-aluminum hydrotalcite of this invention has high crystallinity and good particle size uniformity, high purity, and is free of impurities. The preparation of this invention is simple and convenient. The grinding and lubrication method of this invention uses an ethanol-water solution, which on the one hand helps improve the particle size uniformity of the product, and on the other hand helps dissolve byproducts and impurities, facilitating product filtration. Detailed Implementation

[0022] To provide a clearer and more complete description of the present invention, specific embodiments are described below, but these are not intended to limit the invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents, instruments, and components used, unless otherwise specified, are all commercially available products.

[0023] The magnesium oxide used in this invention has a purity of ≥98%; the magnesium bicarbonate has a purity of ≥98%; and the aluminum hydroxide has a purity of ≥99%.

[0024] Example 1

[0025] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0026] (1) Mix 40.3g of magnesium oxide, 73.15g of magnesium bicarbonate, 39g of aluminum hydroxide and 40.3g of sodium hydroxide, then add 40.3g of 75wt% ethanol aqueous solution to moisten and grind. The grinding speed is 400r / min and the grinding time is 25min.

[0027] (2) Continue grinding at a speed of 400 r / min, gradually increase the temperature to 80℃ at a rate of 0.5-1℃ / min, and keep the temperature for 1.5h.

[0028] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed twice with water, each time using 80.6g of pure water, and then dried at 95℃ for 6 hours. The mixture is ground once every 2 hours to obtain 147.96g of magnesium aluminum hydrotalcite.

[0029] Example 2

[0030] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0031] (1) Mix 60.45g of magnesium oxide, 109.725g of magnesium bicarbonate, 58.5g of aluminum hydroxide and 90g of sodium hydroxide, then add 60.45g of 75wt% ethanol aqueous solution to moisten and grind. The grinding speed is 400r / min and the grinding time is 25min.

[0032] (2) Continue grinding at a speed of 400 r / min, gradually increase the temperature to 80℃ at a rate of 0.5-1℃ / min, and keep the temperature for 1.5h.

[0033] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed twice with water, each time using 120.9g of pure water, and then dried at 95℃ for 6 hours. The mixture is ground once every 2 hours to obtain 223.12g of magnesium aluminum hydrotalcite.

[0034] Example 3

[0035] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0036] (1) Mix 80.6g of magnesium oxide, 146.3g of magnesium bicarbonate, 78g of aluminum hydroxide and 120g of sodium hydroxide, then add 80.6g of 75wt% ethanol aqueous solution to moisten and grind. The grinding speed is 400r / min and the grinding time is 25min.

[0037] (2) Continue grinding at a speed of 400 r / min, gradually increase the temperature to 80℃ at a rate of 0.5-1℃ / min, and keep the temperature for 1.5h.

[0038] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed twice with water, each time using 161.2g of pure water, and then dried at 95℃ for 6 hours. The mixture is ground once every 2 hours to obtain 298.45g of magnesium aluminum hydrotalcite.

[0039] Example 4

[0040] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0041] (1) Mix 40.3g of magnesium oxide, 73.15g of magnesium bicarbonate, 39g of aluminum hydroxide and 40.3g of sodium hydroxide, then add 40.3g of 70wt% ethanol aqueous solution to moisten and grind. The grinding speed is 400r / min and the grinding time is 25min.

[0042] (2) Continue grinding at a speed of 400 r / min, gradually increase the temperature to 80℃ at a rate of 0.5-1℃ / min, and keep the temperature for 1.5h.

[0043] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed twice with water, each time using 80.6g of pure water, and then dried at 95℃ for 6 hours. The mixture is ground once every 2 hours to obtain 146.83g of magnesium aluminum hydrotalcite.

[0044] Example 5

[0045] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0046] (1) Mix 40.3g of magnesium oxide, 73.15g of magnesium bicarbonate, 39g of aluminum hydroxide and 40.3g of sodium hydroxide, then add 40.3g of 80wt% ethanol aqueous solution to moisten and grind. The grinding speed is 400r / min and the grinding time is 25min.

[0047] (2) Continue grinding at a speed of 400 r / min, gradually increase the temperature to 80℃ at a rate of 0.5-1℃ / min, and keep the temperature for 1.5h.

[0048] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed twice with water, each time using 80.6g of pure water, and then dried at 95℃ for 6 hours. The mixture is ground once every 2 hours to obtain 147.32g of magnesium aluminum hydrotalcite.

[0049] Example 6

[0050] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0051] (1) Mix 40.3g of magnesium oxide, 73.15g of magnesium bicarbonate, 39g of aluminum hydroxide and 40.3g of sodium hydroxide, then add 60.45g of 75wt% ethanol aqueous solution to moisten and grind. The grinding speed is 500r / min and the grinding time is 20min.

[0052] (2) Continue grinding at a speed of 300 r / min, gradually increase the temperature to 85°C at a rate of 0.5-1°C / min, and keep the temperature for 1 hour.

[0053] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed twice with water, each time using 181g of pure water, and then dried at 100℃ for 8 hours. The mixture is ground every 3 hours to obtain 146.68g of magnesium aluminum hydrotalcite.

[0054] Example 7

[0055] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0056] (1) Mix 40.3g of magnesium oxide, 73.15g of magnesium bicarbonate, 39g of aluminum hydroxide and 40.3g of sodium hydroxide, then add 80.6g of 75wt% ethanol aqueous solution to moisten and grind. The grinding speed is 300r / min and the grinding time is 30min.

[0057] (2) Continue grinding at a speed of 300 r / min, gradually increase the temperature to 85°C at a rate of 0.5-1°C / min, and keep the temperature for 1.2 h.

[0058] (3) After the reaction is complete, return to room temperature, filter, wash with water 3 times, each time using 200g of pure water, and then dry at 90℃ for 7 hours. Grind once every 2 hours to obtain 147.84g of magnesium aluminum hydrotalcite.

[0059] Example 8

[0060] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0061] (1) Mix 80.6g of magnesium oxide, 146.3g of magnesium bicarbonate, 78g of aluminum hydroxide and 120g of sodium hydroxide, then add 120.9g of 80wt% ethanol aqueous solution to moisten and grind. The grinding speed is 400r / min and the grinding time is 25min.

[0062] (2) Continue grinding at a speed of 400 r / min, gradually increase the temperature to 80℃ at a rate of 0.5-1℃ / min, and keep the temperature for 1.5h.

[0063] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed with water 3 times, each time using 302.25g of pure water, and then dried at 90℃ for 8 hours. The mixture is ground once every 3 hours to obtain 297.78g of magnesium aluminum hydrotalcite.

[0064] Comparative Example 1

[0065] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0066] (1) Mix 40.3g of magnesium oxide, 73.15g of magnesium bicarbonate, 39g of aluminum hydroxide and 40.3g of sodium hydroxide, then add 40.3g of 75wt% pure water to moisten and grind. The grinding speed is 400r / min and the grinding time is 25min.

[0067] (2) Continue grinding at a speed of 400 r / min, gradually increase the temperature to 80℃ at a rate of 0.5-1℃ / min, and keep the temperature for 1.5h.

[0068] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed twice with water, each time using 80.6g of pure water, and then dried at 95℃ for 6 hours. The mixture is ground once every 2 hours to obtain 145.89g of magnesium aluminum hydrotalcite.

[0069] Unlike Example 1, Comparative Example 1 used pure water to wet the grinding process.

[0070] Comparative Example 2

[0071] A method for synthesizing magnesium aluminum hydrotalcite.

[0072] The specific synthesis steps are as follows:

[0073] (1) Mix 40.3g of magnesium oxide, 73.15g of magnesium bicarbonate, 39g of aluminum hydroxide and 40.3g of sodium hydroxide, then add 40.3g of 65wt% ethanol aqueous solution to moisten and grind. The grinding speed is 400r / min and the grinding time is 25min.

[0074] (2) Continue grinding at a speed of 400 r / min, gradually increase the temperature to 80℃ at a rate of 0.5-1℃ / min, and keep the temperature for 1.5h.

[0075] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed twice with water, each time using 80.6g of pure water, and then dried at 95℃ for 6 hours. The mixture is ground once every 2 hours to obtain 146.55g of magnesium aluminum hydrotalcite.

[0076] Unlike Example 1, Comparative Example 2 used a 65wt% aqueous ethanol solution for wetting and grinding.

[0077] Comparative Example 3

[0078] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0079] (1) Mix 40.3g of magnesium oxide, 73.15g of magnesium bicarbonate, 39g of aluminum hydroxide and 40.3g of sodium hydroxide, then add 40.3g of 85wt% ethanol aqueous solution to moisten and grind. The grinding speed is 400r / min and the grinding time is 25min.

[0080] (2) Continue grinding at a speed of 400 r / min, gradually increase the temperature to 80℃ at a rate of 0.5-1℃ / min, and keep the temperature for 1.5h.

[0081] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed twice with water, each time using 80.6g of pure water, and then dried at 95℃ for 6 hours. The mixture is ground once every 2 hours to obtain 147.39g of magnesium aluminum hydrotalcite.

[0082] Unlike Example 1, Comparative Example 3 used an 85 wt% aqueous ethanol solution to wet the grinding process.

[0083] Comparative Example 4

[0084] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0085] (1) Mix 40.3g of magnesium oxide, 73.15g of magnesium bicarbonate, 39g of aluminum hydroxide and 40.3g of sodium hydroxide, then add 40.3g of 75wt% ethanol aqueous solution to moisten and grind. The grinding speed is 250r / min and the grinding time is 25min.

[0086] (2) Continue grinding at a speed of 400 r / min, gradually increase the temperature to 80℃ at a rate of 0.5-1℃ / min, and keep the temperature for 1.5h.

[0087] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed twice with water, each time using 80.6g of pure water, and then dried at 95℃ for 6 hours. The mixture is ground once every 2 hours to obtain 147.53g of magnesium aluminum hydrotalcite.

[0088] Unlike Example 1, the grinding speed of Comparative Example 4 was 250 r / min.

[0089] Comparative Example 5

[0090] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0091] (1) Mix 40.3g of magnesium oxide, 73.15g of magnesium bicarbonate, 39g of aluminum hydroxide and 40.3g of sodium hydroxide, then add 40.3g of 75wt% ethanol aqueous solution to moisten and grind. The grinding speed is 550r / min and the grinding time is 25min.

[0092] (2) Continue grinding at a speed of 400 r / min, gradually increase the temperature to 80℃ at a rate of 0.5-1℃ / min, and keep the temperature for 1.5h.

[0093] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed twice with water, each time using 80.6g of pure water, and then dried at 95℃ for 6 hours. The mixture is ground once every 2 hours to obtain 145.24g of magnesium aluminum hydrotalcite.

[0094] Unlike Example 1, the grinding speed of Comparative Example 5 was 550 r / min.

[0095] Comparative Example 6

[0096] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0097] (1) Mix 40.3g of magnesium oxide, 73.15g of magnesium bicarbonate, 39g of aluminum hydroxide and 40.3g of sodium hydroxide, then add 40.3g of 75wt% ethanol aqueous solution to moisten and grind. The grinding speed is 400r / min and the grinding time is 25min.

[0098] (2) Continue grinding at a speed of 400 r / min, gradually increase the temperature to 80℃ at a rate of 2-5℃ / min, and keep the temperature for 1.5h.

[0099] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed twice with water, each time using 80.6g of pure water, and then dried at 95℃ for 6 hours. The mixture is ground once every 2 hours to obtain 142.54g of magnesium aluminum hydrotalcite.

[0100] Unlike Example 1, the heating rate of Comparative Example 6 was 2–5 °C / min.

[0101] Comparative Example 7

[0102] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0103] (1) Mix 40.3g of magnesium oxide, 73.15g of magnesium bicarbonate, 39g of aluminum hydroxide and 40.3g of sodium hydroxide, then add 40.3g of 75wt% ethanol aqueous solution to moisten and grind. The grinding speed is 400r / min and the grinding time is 25min.

[0104] (2) Continue grinding at a speed of 400 r / min, gradually increase the temperature to 80℃ at a rate of 0.5-1℃ / min, and keep the temperature for 1.5h.

[0105] (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed twice with water, each time using 80.6g of pure water, and then dried at 95℃ for 6 hours to obtain 148.48g of magnesium aluminum hydrotalcite.

[0106] Unlike Example 1, the drying process in Comparative Example 7 did not involve grinding.

[0107] Comparative Example 8

[0108] A method for synthesizing magnesium aluminum hydrotalcite, the specific synthesis steps are as follows:

[0109] (1) Mix 40.3g of magnesium oxide, 29.26g of magnesium bicarbonate, 31.2g of aluminum hydroxide and 32g of sodium hydroxide, then add 40.3g of 75wt% ethanol aqueous solution to moisten and grind. The grinding speed is 400r / min and the grinding time is 25min.

[0110] (2) Continue grinding at a speed of 400 r / min, gradually increase the temperature to 85°C at a rate of 0.5 to 1°C / min, and keep the temperature for 1 hour.

[0111] (3) Then introduce carbon dioxide and continue the reaction for 2 hours;

[0112] (4) After the reaction is complete, return to room temperature, filter, wash with water 3 times, each time using 200g of pure water, and then dry at 90℃ for 7 hours. Grind once every 2 hours to obtain magnesium aluminum hydrotalcite, and obtain 111.35g of magnesium aluminum hydrotalcite.

[0113] Unlike Example 1, in Comparative Example 8, the molar ratio of magnesium oxide, magnesium bicarbonate, aluminum hydroxide, and sodium hydroxide was 5:1:2:4. No grinding was performed during the drying process, and carbon dioxide was introduced to provide a carbonate source.

[0114] Effect Example

[0115] The magnesium aluminum hydrotalcites prepared in Examples 1 to 8 and Comparative Examples 1 to 8 were measured and analyzed for particle size, particle size dispersibility, crystallinity, and purity. The results are shown in Table 1.

[0116]

[0117] The results of the above examples and comparative examples show that the synthesis method of the present invention yields high magnesium-aluminum hydrotalcite with few byproducts, achieving maximum atom economy. According to Table 1, the magnesium-aluminum hydrotalcite synthesized by the present invention has high crystallinity, particle size less than 0.2 micrometers, good particle size dispersibility, uniform and neat particle size distribution, high purity, and no impurities.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for synthesizing magnesium aluminum hydrotalcite, characterized in that, Includes the following steps: (1) Mix magnesium oxide, magnesium bicarbonate, aluminum hydroxide and sodium hydroxide, then add an ethanol aqueous solution to moisten and grind for 20-30 minutes; (2) Continue grinding, gradually increase the temperature to 75~85℃, and keep the reaction at this temperature for 1~1.5h; (3) After the reaction is complete, the temperature is restored to room temperature, filtered, washed with water, and dried to obtain magnesium aluminum hydrotalcite; The mass fraction of the ethanol aqueous solution is 70-80%; The magnesium oxide, magnesium bicarbonate, aluminum hydroxide, and sodium hydroxide are mixed in a molar ratio of 2:1:1:

3. In step (1), the grinding speed is 300~500 r / min; In step (3), the product is ground during the drying process, once every 2-3 hours; In step (2), the rate of gradual heating is 0.5~1℃ / min.

2. The method for synthesizing magnesium aluminum hydrotalcite according to claim 1, characterized in that, In step (1), the amount of the ethanol aqueous solution added is 1 to 2 times the weight of magnesium oxide.

3. The method for synthesizing magnesium aluminum hydrotalcite according to claim 1, characterized in that, In step (2), the grinding speed is 300~500 r / min.

4. The method for synthesizing magnesium aluminum hydrotalcite according to claim 1, characterized in that, In step (3), wash with water 2 to 3 times; each time the amount of pure water used is 2 to 3 times that of the ethanol aqueous solution.

5. The method for synthesizing magnesium aluminum hydrotalcite according to claim 1, characterized in that, In step (3), the drying temperature is 90~100℃, and the drying time is 6~8h.

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