Synthetic method of hydrotalcite

Abstract

The invention discloses a hydrotalcite synthesis method which comprises the following steps: preparing a reaction solution, namely preparing a metal salt solution and an alkali solution; ultrasonic reaction: conveying the prepared metal salt solution and alkali solution into an ultrasonic pipeline reactor for reaction to obtain hydrotalcite crystal nucleus; crystallization: heating and crystallizing the hydrotalcite crystal nucleus obtained by the ultrasonic reaction to obtain hydrotalcite; post-treatment: carrying out centrifugal washing, drying and grinding on the hydrotalcite to obtain hydrotalcite powder. According to the invention, the dispersity, the surface hydrophobicity and the compatibility with organic materials of hydrotalcite particles can be further improved, and hydrotalcite with good dispersity is synthesized; the hydrotalcite with small particle size and high crystallinity is prepared mainly by adjusting parameters such as the dosage of a modifier and the power of an ultrasonic pipeline reactor; the method is simple in process flow, simple and convenient to operate, low in equipment investment and low in production cost. Meanwhile, the process is easy to amplify, and large-scale production can be quickly realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation methods of inorganic functional materials, and particularly relates to a method for synthesizing hydrotalcite. Background Art

[0002] Hydrotalcite, also known as layered double hydroxide, is composed of metal ions and intercalated anions. Due to its properties such as acidity and basicity, particle size controllability, ion exchangeability, and flame retardant effect, it has a wide range of applications in medicine, flame retardants, catalysts, stabilizers, etc. A large number of hydroxyl groups exist on the surface of hydrotalcite, making it easy for particles to agglomerate.

[0003] Hydrotalcite is an inorganic functional new material and is often used as an additive for organic materials in applications. However, it is difficult for hydrotalcite to directly blend with organic materials. Therefore, some modifiers need to be added to improve the monodispersity, surface hydrophobicity of hydrotalcite particles, and compatibility with organic materials, so as to meet the application requirements.

[0004] Currently, there are mainly three methods for preparing modified hydrotalcite: nucleation-crystallization method, hydrothermal method, and calcination reduction method. The nucleation-crystallization method is to mix metal salt solution and alkali solution to form nuclei, and then use the constant temperature crystallization method to make the nuclei grow synchronously in the same environment. It has a wide application range, but is greatly affected by concentration and pH. The nucleation time is short and the crystallinity is not high, making it difficult to control. The hydrothermal method is to slowly drop the metal salt solution and alkali solution together and then crystallize in a high-pressure reactor. It has high purity and good crystallinity, but the conditions are relatively harsh and difficult to control. The calcination reduction method is to place the calcined hydrotalcite in a solution or air to restore the layered structure to obtain a new hydrotalcite, eliminating the intercalation competition of inorganic anions for organic anions. The calcination temperature is difficult to control. If the temperature is too high, spinel will be generated and the layered structure cannot be restored. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for synthesizing hydrotalcite to solve the above technical problems. By utilizing the super mixing and crystallization promoting performance of an ultrasonic tube reactor, a synthesis process of hydrotalcite is developed. The product obtained by this method has small particle size, good dispersibility, and high crystallinity.

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

[0007] A method for synthesizing hydrotalcite, comprising the following steps,

[0008] Reaction solution preparation: Prepare a metal salt solution and an alkali solution;

[0009] Ultrasonic reaction: Transport the prepared metal salt solution and alkali solution to an ultrasonic tube reactor for reaction to obtain an intermediate system containing hydrotalcite nuclei;

[0010] Crystallization: Heat-crystallize the intermediate system obtained from the ultrasonic reaction, and perform solid-liquid separation to obtain hydrotalcite;

[0011] Post-treatment: Wash, dry, and grind the hydrotalcite to obtain hydrotalcite powder.

[0012] Preferably, the metal salt solution is made by dissolving two or three of iron salt, aluminum salt, cobalt salt, nickel salt, magnesium salt, and zinc salt in deionized water, and the concentration of the metal salt solution is 0.1 mol / L - 10 mol / L.

[0013] Preferably, the metal salt solution is made by dissolving magnesium nitrate, aluminum nitrate, and zinc nitrate in deionized water.

[0014] Preferably, the metal salt solution is made by dissolving magnesium nitrate hexahydrate, zinc nitrate hexahydrate, and aluminum nitrate nonahydrate in deionized water, and the concentration of the metal salt solution is 0.2 mol / L - 1 mol / L.

[0015] Preferably, the molar ratio between the metal ions of the magnesium salt and / or the zinc salt and the aluminum salt is 2 - 4:1.

[0016] Preferably, the molar ratio between the metal ions of the magnesium salt, zinc salt, and aluminum salt is 1:1:1.

[0017] Preferably, the alkali solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, and ammonia water.

[0018] Preferably, during the ultrasonic reaction process, the power of the ultrasonic tube reactor is greater than 0 W.

[0019] Preferably, during the ultrasonic reaction process, the power of the ultrasonic tube reactor is 10 W - 30 W.

[0020] Preferably, a modifier is added during the washing process for modification, and the modifier is one or more of Span 60, Span 80, sodium stearate, and oleic acid.

[0021] This application has achieved beneficial technical effects:

[0022] Based on the nucleation-crystallization method, this invention utilizes the super mixing and crystallization-promoting performance of the ultrasonic tube reactor to develop a synthesis process for modified hydrotalcite. The products obtained by this method have small particle size, good dispersibility, and high crystallinity;

[0023] The present technical solution has the following advantages: 1. It can further improve the dispersibility, surface hydrophobicity of hydrotalcite particles, as well as the compatibility with organic materials, and synthesize hydrotalcite with good dispersibility. 2. It mainly prepares hydrotalcite with small particle size and high crystallinity by adjusting parameters such as the dosage of the modifier and the power of the ultrasonic pipe reactor. 3. The process flow of this process is simple, the operation is convenient, the equipment investment is small, and the production cost is low. At the same time, this process is easy to scale up and can quickly achieve large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure shows the contact angle diagram of the hydrotalcite product prepared in Example 1;

[0025] Figure 2 The figure shows the scanning electron microscope image of the hydrotalcite product prepared in Example 1;

[0026] Figure 3 The figure shows the contact angle diagram of the hydrotalcite product prepared in Example 2;

[0027] Figure 4 The figure shows the scanning electron microscope image of the hydrotalcite product prepared in Example 2;

[0028] Figure 5 The figure shows the contact angle diagram of the hydrotalcite product prepared in Example 3;

[0029] Figure 6 The figure shows the scanning electron microscope image of the hydrotalcite product prepared in Example 3;

[0030] Figure 7 The figure shows the contact angle diagram of the hydrotalcite product prepared in Example 4;

[0031] Figure 8 The figure shows the contact angle diagram of the hydrotalcite product prepared in Example 5;

[0032] Figure 9 The figure shows the scanning electron microscope image of the hydrotalcite product prepared in Example 5;

[0033] Figure 10 The figure shows the contact angle diagram of the hydrotalcite product prepared in Example 6;

[0034] Figure 11 The figure shows the scanning electron microscope image of the hydrotalcite product prepared in Example 6;

[0035] Figure 12 The figure shows the contact angle diagram of the hydrotalcite product prepared in Example 7;

[0036] Figure 13 The figure shows the scanning electron microscope image of the hydrotalcite product prepared in Example 7;

[0037] Figure 14The figure shows the contact angle diagram of the hydrotalcite product prepared in Example 8;

[0038] Figure 15 The figure shows the scanning electron microscope image of the hydrotalcite product prepared in Example 8;

[0039] Figure 16 The figure shows the contact angle diagram of the hydrotalcite product prepared in Example 9;

[0040] Figure 17 The figure shows the scanning electron microscope image of the hydrotalcite product prepared in Example 9;

[0041] Figure 18 The figure shows the contact angle diagram of the hydrotalcite product prepared in Example 10;

[0042] Figure 19 The figure shows the scanning electron microscope image of the hydrotalcite product prepared in Example 10;

[0043] Figure 20 The figure shows the contact angle diagram of the hydrotalcite product prepared in Example 11;

[0044] Figure 21 The figure shows the scanning electron microscope image of the hydrotalcite product prepared in Example 11;

[0045] Figure 22 The figure shows the XRD pattern of the magnesium-aluminum-zinc hydrotalcite prepared in Example 9 under an ultrasonic power of 35W;

[0046] Figure 23 The figure shows the FT-IR spectrum of the magnesium-aluminum-zinc hydrotalcite prepared in Example 9 under an ultrasonic power of 35W;

[0047] Figure 24 The figure shows the schematic process flow diagram of the present invention. Detailed Embodiments

[0048] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with its embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the protection scope of the present invention.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0050]

[0051] ​A hydrotalcite synthesis process based on an ultrasonic pipeline reactor in an embodiment of the present invention includes the following steps:

[0052] Reaction solution preparation: Prepare a metal salt solution and an alkali solution.

[0053] Ultrasonic reaction: Transport the prepared metal salt solution and alkali solution to an ultrasonic pipeline reactor for reaction to obtain an intermediate system containing hydrotalcite crystal nuclei. The ultrasonic pipeline reactor used is self-developed and has applied for Chinese Patent CN 202110953049.9.

[0054] Crystallization: Heat and crystallize the intermediate system obtained from the ultrasonic reaction, and perform solid-liquid separation to obtain hydrotalcite.

[0055] Post-treatment: Wash, dry, and grind the hydrotalcite to obtain hydrotalcite powder.

[0056] In one embodiment, the metal salt solution is made by dissolving two or three of iron salt, aluminum salt, cobalt salt, nickel salt, magnesium salt, and zinc salt in deionized water, and the concentration of the metal salt solution is 0.1 mol / L - 10 mol / L.

[0057] In one embodiment, the metal salt solution is made by dissolving magnesium nitrate, aluminum nitrate, and zinc nitrate in deionized water.

[0058] In one embodiment, the metal salt solution is made by dissolving magnesium nitrate hexahydrate, zinc nitrate hexahydrate, and aluminum nitrate nonahydrate in deionized water, and the concentration of the metal salt solution is 0.2 mol / L - 1 mol / L.

[0059] In one embodiment, the molar ratio between the metal ions of the magnesium salt and / or the zinc salt and the aluminum salt is 2 - 4:1.

[0060] In one embodiment, the molar ratio between the metal ions of the magnesium salt, zinc salt, and aluminum salt is 1:1:1.

[0061] In one embodiment, the alkali solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, and ammonia water.

[0062] In one embodiment, the concentration of the alkali solution is 1 mol / L - 2 mol / L.

[0063] In one embodiment, during the ultrasonic reaction process, the power of the ultrasonic pipeline reactor is greater than 0 W.

[0064] In one embodiment, during the ultrasonic reaction process, the delivery flow rate of the metal salt solution is the same as that of the alkali solution.

[0065] In one embodiment, the delivery flow rates of both the metal salt solution and the alkali solution are 50 mL / min - 70 mL / min.

[0066] In one embodiment, the delivery flow rates of both the metal salt solution and the alkali solution are 65 mL / min.

[0067] In one embodiment, during the ultrasonic reaction process, the power of the ultrasonic pipe reactor is 10 W - 30 W.

[0068] In one embodiment, during the washing process, a modifier is added for modification, and the modifier is one or more of Span60, Span 80, sodium stearate, and oleic acid.

[0069] In one embodiment, the solvents added during the washing process include one or more of deionized water, ethanol, and ethanol with a modifier added.

[0070] In one embodiment, the washing process is to perform centrifugation on the hydrotalcite three times in deionized water and once in ethanol.

[0071] In one embodiment, the washing process is to perform centrifugation on the hydrotalcite three times in deionized water and once in ethanol with a modifier added.

[0072] In one embodiment, the modifier is added to ethanol at a mass fraction of 5% - 7%.

[0073] In one embodiment, Span 60 at a mass fraction of 5% - 7% is added to ethanol as the modifier.

[0074] In one embodiment, Span 60 at a mass fraction of 1% - 10% is added to ethanol as the modifier.

[0075] In one embodiment, Span 80 at a mass fraction of 1% - 10% is added to ethanol as the modifier.

[0076] In one embodiment, Span 80 at a mass fraction of 5% - 7% is added to ethanol as the modifier.

[0077] In one embodiment, the amount of solution added during the centrifugal washing process is 1 / 5 - 1 / 3 of the centrifuge tube; it is based on the range of submerging the material but not exceeding 2 / 3 of the maximum capacity of the centrifuge tube; the specific operation is to add the solution into the centrifuge tube, submerge the material but not exceed 2 / 3 of the maximum capacity of the centrifuge tube, centrifuge under the set parameters. After centrifugation is completed, the material adheres to the tube wall, pour out the solution completely, and perform subsequent centrifugation. The operation method is the same as above.

[0078] In one embodiment, the crystallization process is carried out by oil bath heating for crystallization;

[0079] In one embodiment, the pH is adjusted to 9 - 13 during the crystallization process;

[0080] In one embodiment, the pH is adjusted by the amount of sodium hydroxide added;

[0081] In one embodiment, the temperature of the heating reaction for crystallization is 80°C - 120°C, and the heating duration is 1h - 8h;

[0082] In one embodiment, during the crystallization process, the heating duration is 6h;

[0083] In one embodiment, the ultrasonic frequency of the ultrasonic pipe reactor is 18kHz - 500kHz;

[0084] In one embodiment, the ultrasonic frequency of the ultrasonic pipe reactor is 18kHz - 60kHz;

[0085] In one embodiment, the hydraulic diameter of the pipe of the ultrasonic pipe reactor is 0.1mm - 50mm;

[0086] In one embodiment, the hydraulic diameter of the pipe of the ultrasonic pipe reactor is 30mm - 40mm;

[0087] In one embodiment, the residence time of the ultrasonic reaction is 5s - 15s;

[0088] In one embodiment, the temperature of the drying treatment is 60°C - 80°C;

[0089] In one embodiment, the time of the drying treatment is 0.5h - 48h;

[0090] In one embodiment, the time of the drying treatment is 24h.

[0091] In one embodiment, the hydrotalcite powder is prepared according to the following steps: Prepare a metal salt solution with a concentration of 0.75 mol / L, where the metal salts are formulated in equimolar amounts, each being 0.25 mol. Prepare a sodium hydroxide solution with a concentration of 1.75 mol / L. Feed the prepared metal salt solution and sodium hydroxide solution into an ultrasonic pipe reactor, and adjust the feeding flow rate and the ultrasonic pipe power to obtain hydrotalcite crystal nuclei with different particle sizes. Crystallize the crystal nuclei coming out of the ultrasonic pipe reactor in an oil bath for 6 h. Then, add a modifier Span80 with a mass fraction of 5%-7% during centrifugation. Dry and grind the centrifuged and modified sample to obtain the hydrotalcite powder.

[0092] In one embodiment, the concentration of the metal salt solution is 0.75 mol / L; the concentration of the alkali solution is 1.75 mol / L.

[0093] The technical solution of the present invention adopts the following preparation method:

[0094] 1. Preparation of reaction solution: First, prepare a certain concentration of magnesium nitrate, aluminum nitrate, and zinc nitrate dissolved in deionized water to form solution A (metal salt solution); dissolve sodium hydroxide in deionized water to prepare solution B (sodium hydroxide solution).

[0095] 2. Ultrasonic reaction: Feed the prepared multi-metal salt solution and sodium hydroxide solution into an ultrasonic pipe reactor for reaction, and adjust the feeding flow rate and ultrasonic power to obtain magnesium-aluminum-zinc hydrotalcite crystal nuclei.

[0096] 3. Oil bath crystallization: Crystallize the crystal nuclei coming out of the ultrasonic pipe reactor in an oil bath to obtain magnesium-aluminum-zinc hydrotalcite.

[0097] 4. Post-treatment: Centrifuge, wash, dry, and grind the hydrotalcite coming out of the ultrasonic pipe reactor to obtain the magnesium-aluminum-zinc hydrotalcite powder.

[0098] The present invention is based on the nucleation-crystallization method, and utilizes the super mixing of the ultrasonic pipe reactor and the ultrasonic-promoted crystallization ability to develop a continuous synthesis process for modified hydrotalcite. By controlling factors such as the type and content of metal particles, modifier concentration, modifier type, ultrasonic power, residence time, temperature, pH, etc., the controllable synthesis of modified hydrotalcite with a particle size of 50 nm - 2 μm, good dispersibility, and high crystallinity is achieved. Ultrasonic has a promoting effect on nucleation, and uses an ultrasonic microreactor to continuously produce hydrotalcite with regular crystal forms. At the same time, the continuous controllable synthesis of various multi-metal particle-containing hydrotalcites (such as ternary) can be realized.

[0099] The technical solution of the present invention will be introduced in detail with specific embodiments below.

[0100] Example 1

[0101] 1. Reaction solution preparation: Prepare a metal salt solution with a concentration of 0.75 mol / L and a sodium hydroxide solution with a concentration of 1.75 mol / L; the metal salt solution is made by dissolving magnesium nitrate hexahydrate, zinc nitrate hexahydrate, and aluminum nitrate nonahydrate in deionized water, and the molar ratio of each metal ion of the magnesium salt, zinc salt, and aluminum salt is 1:1:1. The amount of substance of a single metal salt is calculated according to the following formula: n = m / M (mass of salt / molar mass of salt).

[0102] 2. Ultrasonic reaction: The prepared metal salt solution and alkali solution in 1 are both fed into the ultrasonic tubular reactor at a rate of 65 mL / min, the reactor power is set to 35 W, the ultrasonic frequency is 20 kHz, the hydraulic diameter of the ultrasonic tubular reactor is 6 mm, the reaction residence time is 10 s, and the total feed flow rate is 130 mL / min.

[0103] 3. Oil bath crystallization: The crystal nuclei at the outlet of the ultrasonic tubular reactor are placed in a three-necked flask and crystallized in an oil bath at 100 °C for 6 h.

[0104] 4. Centrifugal drying: The hydrotalcite coming out of the ultrasonic tubular reactor is centrifuged three times with water and once with ethanol containing 5% Span80 modifier at a rotation speed of 8000 r / min for 15 min, and then placed in an oven at 60 °C for drying for 24 h. After drying, it is ground to obtain magnesium-aluminum-zinc hydrotalcite powder with a particle size of 84 nm.

[0105] Example 2

[0106] 1. Reaction solution preparation: Prepare a metal salt solution with a concentration of 0.75 mol / L and a sodium hydroxide solution with a concentration of 1.75 mol / L; the metal salt solution is made by dissolving magnesium nitrate hexahydrate, zinc nitrate hexahydrate, and aluminum nitrate nonahydrate in deionized water, and the molar ratio of each metal ion of the magnesium salt, zinc salt, and aluminum salt is 1:1:1. The amount of substance of a single metal salt is calculated according to the following formula: n = m / M (mass of salt / molar mass of salt).

[0107] 2. Ultrasonic reaction: The prepared metal salt solution and alkali solution in 1 are both fed into the ultrasonic tubular reactor at a rate of 65 mL / min, the reactor power is set to 15 W, the ultrasonic frequency is 20 kHz, the hydraulic diameter of the ultrasonic tubular reactor is 6 mm, the reaction residence time is 10 s, and the total feed flow rate is 130 mL / min.

[0108] 3. Oil bath crystallization: The crystal nuclei at the outlet of the ultrasonic tubular reactor are placed in a three-necked flask and crystallized in an oil bath at 100 °C for 6 h.

[0109] 4. Centrifugal drying: The hydrotalcite coming out of the ultrasonic tubular reactor was centrifuged with water three times and ethanol containing 5% Span80 modifier once, centrifuged at a speed of 8000 r / min for 15 min, placed in an oven at 60 °C and dried for 24 h, and then ground to obtain magnesium-aluminum-zinc hydrotalcite powder with a particle size of 71 nm.

[0110] Example 3

[0111] 1. Preparation of reaction solution: Prepare a metal salt solution with a concentration of 0.75 mol / L and a sodium hydroxide solution with a concentration of 1.75 mol / L; the metal salt solution is made by dissolving magnesium nitrate hexahydrate, zinc nitrate hexahydrate, and aluminum nitrate nonahydrate in deionized water, and the molar ratio of each metal ion of the magnesium salt, zinc salt, and aluminum salt is 1:1:1. The amount of substance of a single metal salt is calculated according to the following formula: n = m / M (mass of salt / molar mass of salt).

[0112] 2. Ultrasonic reaction: The metal salt solution and the alkali solution prepared in 1 were both fed into the ultrasonic tubular reactor at a rate of 65 mL / min, the power of the reactor was set to 0 W, the ultrasonic frequency was 20 kHz, the hydraulic diameter of the ultrasonic tubular reactor was 6 mm, the reaction residence time was 10 s, and the total feed flow rate was 130 mL / min.

[0113] 3. Oil bath crystallization: The crystal nuclei at the outlet of the ultrasonic tubular reactor were placed in a three-necked flask and crystallized in an oil bath at 100 °C for 6 h.

[0114] 4. Centrifugal drying: The hydrotalcite coming out of the ultrasonic tubular reactor was centrifuged with water three times and ethanol containing 5% Span80 modifier once, centrifuged at a speed of 8000 r / min for 15 min, placed in an oven at 60 °C and dried for 24 h, and then ground to obtain magnesium-aluminum-zinc hydrotalcite powder with a particle size of 95 nm.

[0115] Example 4

[0116] 1. Preparation of reaction solution: Prepare a metal salt solution with a concentration of 0.75 mol / L and a sodium hydroxide solution with a concentration of 1.75 mol / L; the metal salt solution is made by dissolving magnesium nitrate hexahydrate, zinc nitrate hexahydrate, and aluminum nitrate nonahydrate in deionized water, and the molar ratio of each metal ion of the magnesium salt, zinc salt, and aluminum salt is 1:1:1. The amount of substance of a single metal salt is calculated according to the following formula: n = m / M (mass of salt / molar mass of salt).

[0117] 2. Ultrasonic reaction: The prepared metal salt solution and alkali solution in 1 are both fed into the ultrasonic pipeline reactor at a rate of 65 mL / min. The reactor power is set to 35 W, the ultrasonic frequency is 20 kHz, the hydraulic diameter of the ultrasonic pipeline reactor is 6 mm, the reaction residence time is 10 s, and the total feed flow rate is 130 mL / min.

[0118] 3. Oil bath crystallization: The crystal nuclei from the outlet of the ultrasonic pipeline reactor are placed in a three-necked flask and crystallized in an oil bath at 100 °C for 6 h.

[0119] 4. Centrifugation and drying: The hydrotalcite from the ultrasonic pipeline reactor is centrifuged with water three times and ethanol containing 6% Span80 modifier once at a speed of 8000 r / min for 15 min, then placed in an oven at 60 °C for drying for 24 h. After drying, it is ground to obtain magnesium-aluminum-zinc hydrotalcite powder with a particle size of 1 μm.

[0120] Example 5

[0121] 1. Preparation of reaction solution: Prepare a metal salt solution with a concentration of 0.75 mol / L and a sodium hydroxide solution with a concentration of 1.75 mol / L; the metal salt solution is made by dissolving magnesium nitrate hexahydrate, zinc nitrate hexahydrate, and aluminum nitrate nonahydrate in deionized water, and the molar ratio of each metal ion of the magnesium salt, zinc salt, and aluminum salt is 1:1:1. The amount of substance of a single metal salt is calculated according to the following formula: n = m / M (mass of salt / molar mass of salt).

[0122] 2. Ultrasonic reaction: The prepared metal salt solution and alkali solution in 1 are both fed into the ultrasonic pipeline reactor at a rate of 65 mL / min. The reactor power is set to 0 W, the ultrasonic frequency is 20 kHz, the hydraulic diameter of the ultrasonic pipeline reactor is 6 mm, the reaction residence time is 10 s, and the total feed flow rate is 130 mL / min.

[0123] 3. Oil bath crystallization: The crystal nuclei from the outlet of the ultrasonic pipeline reactor are placed in a three-necked flask and crystallized in an oil bath at 100 °C for 6 h.

[0124] 4. Centrifugation and drying: The hydrotalcite from the ultrasonic pipeline reactor is centrifuged with water three times and ethanol containing 6% Span80 modifier once at a speed of 8000 r / min for 15 min, then placed in an oven at 60 °C for drying for 24 h. After drying, it is ground to obtain magnesium-aluminum-zinc hydrotalcite powder with a particle size of 2 μm.

[0125] Example 6

[0126] 1. Reaction solution preparation: Prepare a metal salt solution with a concentration of 0.75 mol / L and a sodium hydroxide solution with a concentration of 1.75 mol / L; the metal salt solution is made by dissolving magnesium nitrate hexahydrate, zinc nitrate hexahydrate, and aluminum nitrate nonahydrate in deionized water, and the molar ratio of each metal ion of the magnesium salt, zinc salt, and aluminum salt is 1:1:1. The amount of substance of a single metal salt is calculated according to the following formula: n = m / M (mass of salt / molar mass of salt).

[0127] 2. Ultrasonic reaction: Feed the metal salt solution and the alkali solution prepared in 1 into the ultrasonic pipe reactor at a rate of 65 mL / min each. The power of the reactor is set to 35 W, the ultrasonic frequency is 20 kHz, the hydraulic diameter of the ultrasonic pipe reactor is 6 mm, the reaction residence time is 10 s, and the total feed flow rate is 130 mL / min.

[0128] 3. Oil bath crystallization: Place the crystal nuclei at the outlet of the ultrasonic pipe reactor in a three-necked flask and crystallize in an oil bath at 100 °C for 6 h.

[0129] 4. Centrifugal drying: Centrifuge the hydrotalcite coming out of the ultrasonic pipe reactor three times with water and once with ethanol containing 7% Span80 modifier at a speed of 8000 r / min for 15 min, then place it in an oven at 60 °C and dry for 24 h. After drying, grind it to obtain magnesium-aluminum-zinc hydrotalcite powder with a particle size of 50 nm.

[0130] Example 7

[0131] 1. Reaction solution preparation: Prepare a metal salt solution with a concentration of 0.75 mol / L and a sodium hydroxide solution with a concentration of 1.75 mol / L; the metal salt solution is made by dissolving magnesium nitrate hexahydrate, zinc nitrate hexahydrate, and aluminum nitrate nonahydrate in deionized water, and the molar ratio of each metal ion of the magnesium salt, zinc salt, and aluminum salt is 1:1:1. The amount of substance of a single metal salt is calculated according to the following formula: n = m / M (mass of salt / molar mass of salt).

[0132] 2. Ultrasonic reaction: Feed the metal salt solution and the alkali solution prepared in 1 into the ultrasonic pipe reactor at a rate of 65 mL / min each. The power of the reactor is set to 15 W, the ultrasonic frequency is 20 kHz, the hydraulic diameter of the ultrasonic pipe reactor is 6 mm, the reaction residence time is 10 s, and the total feed flow rate is 130 mL / min.

[0133] 3. Oil bath crystallization: Place the crystal nuclei at the outlet of the ultrasonic pipe reactor in a three-necked flask and crystallize in an oil bath at 100 °C for 6 h.

[0134] 4. Centrifugal drying: The hydrotalcite obtained from the ultrasonic tubular reactor was centrifuged with water three times and ethanol containing 7% Span80 modifier once, centrifuged at a speed of 8000 r / min for 15 min, placed in an oven at 60 °C for drying for 24 h, and ground after drying to obtain magnesium-aluminum-zinc hydrotalcite powder with a particle size of 80 nm.

[0135] Example 8

[0136] 1. Preparation of reaction solution: Prepare a metal salt solution with a concentration of 0.75 mol / L and a sodium hydroxide solution with a concentration of 1.75 mol / L; the metal salt solution is made by dissolving magnesium nitrate hexahydrate, zinc nitrate hexahydrate, and aluminum nitrate nonahydrate in deionized water, and the molar ratio of each metal ion of magnesium salt, zinc salt, and aluminum salt is 1:1:1. The amount of substance of a single metal salt is calculated according to the following formula: n = m / M (mass of salt / molar mass of salt).

[0137] 2. Ultrasonic reaction: The prepared metal salt solution and alkali solution in 1 were both fed into the ultrasonic tubular reactor at a rate of 65 mL / min, the reactor power was set to 0 W, the ultrasonic frequency was 20 kHz, the hydraulic diameter of the ultrasonic tubular reactor was 6 mm, the reaction residence time was 10 s, and the total feed flow rate was 130 mL / min.

[0138] 3. Oil bath crystallization: The crystal nuclei from the outlet of the ultrasonic tubular reactor were placed in a three-necked flask and crystallized in an oil bath at 100 °C for 6 h.

[0139] 4. Centrifugal drying: The hydrotalcite obtained from the ultrasonic tubular reactor was centrifuged with water three times and ethanol containing 7% Span80 modifier once, centrifuged at a speed of 8000 r / min for 15 min, placed in an oven at 60 °C for drying for 24 h, and ground after drying to obtain magnesium-aluminum-zinc hydrotalcite powder with a particle size of 93 nm.

[0140] Example 9

[0141] 1. Preparation of reaction solution: Prepare a metal salt solution with a concentration of 0.75 mol / L and a sodium hydroxide solution with a concentration of 1.75 mol / L; magnesium nitrate hexahydrate, zinc nitrate hexahydrate, and aluminum nitrate nonahydrate are dissolved in deionized water, and the molar ratio of each metal ion of magnesium salt, zinc salt, and aluminum salt is 1:1:1. The amount of substance of a single metal salt is calculated according to the following formula: n = m / M (mass of salt / molar mass of salt).

[0142] 2. Ultrasonic reaction: The prepared metal salt solution and alkali solution in 1 are both fed into the ultrasonic pipe reactor at a rate of 65 mL / min. The power of the reactor is set to 35 W, with an ultrasonic frequency of 20 kHz. The hydraulic diameter of the ultrasonic pipe reactor is 6 mm, the reaction residence time is 10 s, and the total feed flow rate is 130 mL / min.

[0143] 3. Oil bath crystallization: The crystal nuclei from the outlet of the ultrasonic pipe reactor are placed in a three-necked flask and crystallized in an oil bath at 100 °C for 6 h.

[0144] 4. Centrifugation and drying: The hydrotalcite from the ultrasonic pipe reactor is centrifuged with water three times and ethanol once at a speed of 8000 r / min for 15 min, then placed in an oven at 60 °C and dried for 24 h. After drying, it is ground to obtain magnesium-aluminum-zinc hydrotalcite powder with a particle size of 67 nm.

[0145] Example 10

[0146] 1. Preparation of reaction solution: Prepare a metal salt solution with a concentration of 0.75 mol / L and a sodium hydroxide solution with a concentration of 1.75 mol / L; the metal salt solution is made by dissolving magnesium nitrate hexahydrate, zinc nitrate hexahydrate, and aluminum nitrate nonahydrate in deionized water, and the molar ratio of each metal ion of the magnesium salt, zinc salt, and aluminum salt is 1:1:1. The amount of substance of a single metal salt is calculated according to the following formula: n = m / M (mass of salt / molar mass of salt).

[0147] 2. Ultrasonic reaction: The prepared metal salt solution and alkali solution in 1 are both fed into the ultrasonic pipe reactor at a rate of 65 mL / min. The power of the reactor is set to 15 W, with an ultrasonic frequency of 20 kHz. The hydraulic diameter of the ultrasonic pipe reactor is 6 mm, the reaction residence time is 10 s, and the total feed flow rate is 130 mL / min.

[0148] 3. Oil bath crystallization: The crystal nuclei from the outlet of the ultrasonic pipe reactor are placed in a three-necked flask and crystallized in an oil bath at 100 °C for 6 h.

[0149] 4. Centrifugation and drying: The hydrotalcite from the ultrasonic pipe reactor is centrifuged with water three times and ethanol once at a speed of 8000 r / min for 15 min, then placed in an oven at 60 °C and dried for 24 h. After drying, it is ground to obtain magnesium-aluminum-zinc hydrotalcite powder with a particle size of 83 nm.

[0150] Example 11

[0151] 1. Reaction solution preparation: Prepare a metal salt solution with a concentration of 0.75 mol / L and a sodium hydroxide solution with a concentration of 1.75 mol / L; the metal salt solution is made by dissolving magnesium nitrate hexahydrate, zinc nitrate hexahydrate, and aluminum nitrate nonahydrate in deionized water, and the molar ratio of each metal ion of the magnesium salt, zinc salt, and aluminum salt is 1:1:1. The amount of substance of a single metal salt is calculated according to the following formula: n = m / M (mass of salt / molar mass of salt).

[0152] 2. Ultrasonic reaction: The prepared metal salt solution and alkali solution in 1 are both fed into the ultrasonic pipeline reactor at a rate of 65 mL / min. The power of the reactor is set to 0 W, the ultrasonic frequency is 20 kHz, the hydraulic diameter of the ultrasonic pipeline reactor is 6 mm, the reaction residence time is 10 s, and the total feed flow rate is 130 mL / min.

[0153] 3. Oil bath crystallization: The crystal nuclei at the outlet of the ultrasonic pipeline reactor are placed in a three-necked flask and crystallized in an oil bath at 100 °C for 6 h.

[0154] 4. Centrifugal drying: The hydrotalcite coming out of the ultrasonic pipeline reactor is centrifuged three times with water and once with ethanol at a speed of 8000 r / min for 15 min, then placed in an oven at 60 °C and dried for 24 h. After drying, it is ground to obtain magnesium-aluminum-zinc hydrotalcite powder with a particle size of 97 nm.

[0155] The present invention is based on the nucleation-crystallization method, and utilizes the super mixing of the ultrasonic pipeline reactor and the ultrasonic-promoted crystallization ability to develop a continuous synthesis process for modified hydrotalcite. By regulating factors such as the type and content of metal particles, the concentration of the modifier, the type of modifier, the ultrasonic power, the residence time, the temperature, and the pH, the controllable synthesis of modified hydrotalcite with a particle size of 50 nm - 2 μm, good dispersibility, and high crystallinity is realized. Ultrasonic has a nucleation-promoting effect, and a ultrasonic microreactor is used to continuously produce hydrotalcite with regular crystal forms. At the same time, the continuous controllable synthesis of various multi-metal-ion-containing hydrotalcites (such as ternary) can be realized.

[0156] The test methods of this application are X-ray Diffraction (XRD for short), Fourier Transform Infrared (FT-IR for short), field emission scanning electron microscope (scanning electronmicroscope, SEM for short), and contact angle.

[0157] As Figure 22As shown, for the zinc-magnesium-aluminum layered double hydroxide prepared under the condition of an ultrasonic power of 35 W, the characteristic peak of the hexagonal layered structure is narrow and sharp, and the crystallinity of the powder is good. It can be seen that this technical solution can effectively solve the problems of low crystallinity and difficult control existing in the prior art, such as the nucleation-crystallization method.

[0158] Such as Figure 23 As shown, for the zinc-magnesium-aluminum layered double hydroxide prepared under the condition of an ultrasonic power of 35 W, characteristic peaks appear at 551 cm -1 , 626 cm -1 , 826 cm -1 , 1384 cm -1 , 1621 cm -1 , 1763 cm -1 , and the infrared spectrum shifts, which are the characteristics of a blend system with a certain compatibility. It can be seen that this technical solution can synthesize layered double hydroxides with good dispersibility and good compatibility with organic materials, and the control method is simple and easy to implement.

[0159] Such as Figures 16 to 21 , as shown, the particle sizes of the layered double hydroxides measured at ultrasonic powers of 15 W and 35 W are both smaller than that at 0 W. It can be seen that the dispersion effect of the solution in the ultrasonic pipeline is better than that without ultrasonic. In this technical solution, the dispersion performance during the synthesis process can be effectively improved, so as to achieve the technical effects of smaller particle size and higher crystallinity of the layered double hydroxide by controlling the ultrasonic power.

[0160] Such as Figures 1 to 6 As shown, the contact angles measured at ultrasonic powers of 15 W and 35 W are greater than that at 0 W. Under the same modifier, the hydrophobicity is greatly improved, and the hydrophobicity is the best at a power of 15 W. In this technical solution, the surface hydrophobicity of the layered double hydroxide can be improved under ultrasonic process conditions; combined with such as Figures 16 to 19 , it can be seen that combined with the modifier under ultrasonic process conditions, the surface hydrophobicity of the layered double hydroxide can be effectively improved.

[0161] Such as Figures 7 to 15 As shown, under the state of the same addition amount of the modifier, the particle sizes of the layered double hydroxides prepared at ultrasonic powers of 15 W or 35 W are both smaller than that at 0 W. It can be seen that the dispersion effect of the solution in the ultrasonic pipeline is better than that without ultrasonic. In this technical solution, the dispersion performance during the synthesis process can be effectively improved, so as to achieve the technical effects of smaller particle size and higher crystallinity of the layered double hydroxide by adjusting the ultrasonic power. And compared with the example without adding the modifier, the hydrophobicity of the layered double hydroxide prepared by adding the modifier is stronger, especially when modified by combining the modifier under ultrasonic process conditions, a layered double hydroxide product with good hydrophobicity is obtained. And this process flow is simple, the operation is convenient, the equipment investment is small, and the production cost is low. At the same time, this process is easy to scale up and can quickly achieve large-scale production.

[0162] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as falling within the scope described in this specification.

[0163] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

[0164] The above has elaborated in detail the embodiments of a hydrotalcite synthesis and modification process based on an ultrasonic pipeline reactor provided by the present invention. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the core idea of the present invention. It should be pointed out that for those of ordinary skill in the technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for synthesizing hydrotalcite, characterized in that, it comprises the following steps, Reaction solution preparation: Prepare a metal salt solution and an alkali solution; Ultrasonic reaction: Transport the prepared metal salt solution and alkali solution to an ultrasonic tubular reactor for reaction to obtain an intermediate system containing hydrotalcite crystal nuclei; Crystallization: Heat and crystallize the intermediate system obtained from the ultrasonic reaction, and perform solid-liquid separation to obtain hydrotalcite; Post-treatment: Wash, dry, and grind the hydrotalcite to obtain hydrotalcite powder.

2. The method for synthesizing hydrotalcite according to claim 1, characterized in that, the metal salt solution is prepared by dissolving two or three of iron salt, aluminum salt, cobalt salt, nickel salt, magnesium salt, and zinc salt in deionized water, and the concentration of the metal salt solution is 0.1 mol / L - 10 mol / L.

3. The method for synthesizing hydrotalcite according to claim 2, characterized in that, the metal salt solution is prepared by dissolving magnesium nitrate, aluminum nitrate, and zinc nitrate in deionized water.

4. The method for synthesizing hydrotalcite according to claim 2, characterized in that, the metal salt solution is prepared by dissolving magnesium nitrate hexahydrate, zinc nitrate hexahydrate, and aluminum nitrate nonahydrate in deionized water, and the concentration of the metal salt solution is 0.2 mol / L - 1 mol / L.

5. The method for synthesizing hydrotalcite according to claim 3 or 4, characterized in that, the molar ratio between the metal ions of the magnesium salt and / or the zinc salt and the aluminum salt is 2 - 4:

1.

6. The method for synthesizing hydrotalcite according to claim 5, characterized in that, the molar ratio between the metal ions of the magnesium salt, zinc salt, and aluminum salt is 1:1:

1.

7. The method for synthesizing hydrotalcite according to claim 1, characterized in that, the alkali solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, and ammonia water.

8. The method for synthesizing hydrotalcite according to claim 1, characterized in that, during the ultrasonic reaction, the power of the ultrasonic tubular reactor is greater than 0 W.

9. The method for synthesizing hydrotalcite according to claim 1, characterized in that, during the ultrasonic reaction, the power of the ultrasonic tubular reactor is 10 W - 30 W.

10. The method for synthesizing hydrotalcite according to claim 1, characterized in that, during the washing process, a modifier is added for modification, and the modifier is one or more of Span 60, Span 80, sodium stearate, and oleic acid.

Images