A metal ion-enhanced amino acid-intercalated hydrotalcite composite aerogel and its preparation method

Abstract

This invention relates to the field of aerogel technology and discloses a metal ion-reinforced amino acid intercalated hydrotalcite composite aerogel and its preparation method, comprising the following steps: (1) mixing calcined magnesium aluminum hydrotalcite, amino acids, and water, and carrying out a hydrothermal reaction to obtain an amino acid intercalated hydrotalcite hydrogel; (2) immersing the amino acid intercalated hydrotalcite hydrogel in a metal ion solution to obtain a metal ion-reinforced amino acid intercalated hydrotalcite hydrogel; (3) performing solvent replacement on the metal ion-reinforced amino acid intercalated hydrotalcite hydrogel, followed by supercritical drying to obtain a composite aerogel. The composite aerogel of this invention can effectively reduce the brittleness of materials, thereby improving the mechanical strength of the composite aerogel.

Description

Technical Field

[0001] This invention relates to the field of aerogel technology, and in particular to a metal ion-enhanced amino acid intercalated hydrotalcite composite aerogel and its preparation method. Background Technology

[0002] Aerogels possess a continuous porous network structure and are among the lightest known solids. This porous structure endows them with a combination of properties, including low density, high porosity, efficient thermal insulation, low dielectric constant, and large specific surface area. Due to these excellent properties, aerogels have significant application prospects in fields such as chemistry, optics, power, aerospace, and life sciences.

[0003] Hydrotalcite has attracted widespread attention due to its excellent thermodynamic properties, large specific surface area, and superior flame retardancy. Because of the strong chemical bonds within the hydrotalcite layers and the weak bonds between anions in the interlayer regions, it possesses inherent anion exchange capacity. Various guest materials can be intercalated into the interlayer regions of hydrotalcite through methods such as ion exchange, post-calcination recombination, and repeated intercalation to control desired physicochemical properties. However, the interaction between the intercalated guest material and the hydrotalcite host material is usually weak, resulting in low mechanical strength and a tendency for brittle fracture and fragmentation. Therefore, there is an urgent need to provide a composite aerogel with excellent mechanical strength. Summary of the Invention

[0004] In view of this, the present invention provides a metal ion-reinforced amino acid intercalated hydrotalcite composite aerogel and its preparation method, so as to solve the problem of poor mechanical strength of existing intercalated hydrotalcite composite materials.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] On one hand, the present invention provides a method for preparing a metal ion-enhanced amino acid intercalated hydrotalcite composite aerogel, comprising the following steps:

[0007] (1) The calcined magnesium aluminum hydrotalcite, amino acids and water were mixed and subjected to a hydrothermal reaction to obtain an amino acid intercalated hydrotalcite hydrogel.

[0008] (2) The amino acid intercalated hydrotalcite hydrogel is soaked in a metal ion solution to obtain a metal ion-enhanced amino acid intercalated hydrotalcite hydrogel.

[0009] (3) The metal ion-enhanced amino acid intercalated hydrotalcite hydrogel is subjected to solvent replacement and then supercritical drying to obtain composite aerogel.

[0010] Preferably, the mass ratio of the calcined magnesium aluminum hydrotalcite to the amino acid is 1:0.5-2.

[0011] Preferably, the concentration of the calcined magnesium aluminum hydrotalcite is 30-100 mg / mL.

[0012] Preferably, the mixed concentration of the amino acids is 15-200 mg / mL.

[0013] Preferably, the amino acid includes one or more of alanine, glycine, threonine, histidine, and sarcosine.

[0014] Preferably, the hydrothermal reaction is carried out at a temperature of 100-160°C for 6-24 hours.

[0015] Preferably, the concentration of the metal ion solution is 0.05-0.5 mol / L.

[0016] Preferably, the metal ions in the metal ion solution include one or more of calcium ion solution, aluminum ion solution and zirconium ion solution.

[0017] Preferably, the soaking time is 24-48 hours.

[0018] Preferably, the solvent replacement involves impregnating the metal ion-enhanced amino acid intercalated hydrotalcite hydrogel in an organic solvent.

[0019] Preferably, the volume ratio of the metal ion-reinforced amino acid intercalated hydrotalcite hydrogel to the organic solvent is 1:10-20.

[0020] Preferably, the organic solvent includes one or more of ethanol, methanol, isopropanol and acetone.

[0021] Preferably, the immersion is performed 3-6 times, with each immersion lasting 6-12 hours.

[0022] Preferably, the supercritical drying pressure is 9-9.8 MPa, the temperature is 35-40℃, and the time is 0.5-1.5 h.

[0023] Preferably, the method for preparing the calcined magnesium aluminum hydrotalcite is as follows: the magnesium aluminum hydrotalcite is heat-treated to obtain the calcined magnesium aluminum hydrotalcite.

[0024] Preferably, the heat treatment includes a first stage heat treatment and a second stage heat treatment.

[0025] Preferably, the temperature of the first stage heat treatment is 200-300℃ and the time is 0.5-2h.

[0026] Preferably, the temperature of the second stage heat treatment is 400-500℃ and the time is 8-10h.

[0027] On the other hand, the present invention also provides a metal ion-enhanced amino acid intercalated hydrotalcite composite aerogel prepared by the method described in any one of the above-mentioned methods.

[0028] This invention provides a composite aerogel and its preparation method, which have the following advantages compared with the prior art:

[0029] The metal ion-reinforced amino acid intercalated hydrotalcite composite aerogel of the present invention combines a rigid crystalline phase (magnesium aluminum hydrotalcite) and a flexible amorphous phase (amino acid) into a gel via a hydrothermal method, and strengthens the network through calcium ion crosslinking. The resulting organic-inorganic composite aerogel can effectively reduce the brittleness of the material and thus improve the mechanical strength of the composite aerogel.

[0030] In addition, the supercritical drying method used in this invention allows the replacement solvent to penetrate more uniformly into the metal ion-reinforced amino acid intercalated hydrotalcite hydrogel, thereby better displacing the original solvent in the metal ion-reinforced amino acid intercalated hydrotalcite hydrogel. This helps to form a uniformly distributed and smaller pore structure during the drying process, making the prepared composite aerogel denser and harder, with higher mechanical strength. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the aerogels prepared in Examples 1-3 of the present invention;

[0033] Figure 2 This is a schematic diagram showing the compressive strength of the aerogels prepared in Examples 1-3 of the present invention. Detailed Implementation

[0034] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments below are merely illustrative and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the later embodiments, conditions and methods known in the art can be used for processing.

[0035] In one aspect of the present invention, a method for preparing a metal ion-reinforced amino acid-intercalated hydrotalcite composite aerogel is provided, comprising the following steps:

[0036] (1) The calcined magnesium aluminum hydrotalcite, amino acids and water were mixed and subjected to a hydrothermal reaction to obtain an amino acid intercalated hydrotalcite hydrogel.

[0037] (2) The amino acid intercalated hydrotalcite hydrogel is soaked in a metal ion solution to obtain a metal ion-enhanced amino acid intercalated hydrotalcite hydrogel.

[0038] (3) The metal ion-enhanced amino acid intercalated hydrotalcite hydrogel is subjected to solvent replacement and then supercritical drying to obtain composite aerogel.

[0039] In this invention, calcined magnesium aluminum hydrotalcite, amino acids and water are first mixed and subjected to a hydrothermal reaction to obtain an amino acid intercalated hydrotalcite hydrogel.

[0040] In some embodiments of the present invention, the mass ratio of the calcined magnesium aluminum hydrotalcite to the amino acids is 1:0.5-2, for example, it can be 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, etc.; the mixed concentration of the calcined magnesium aluminum hydrotalcite is 30-100 mg / mL, for example, it can be 30 mg / mL, 40 mg / mL, 50 mg / mL, 60 mg / mL, 70 mg / mL, 80 mg / mL, 90 mg / mL, 100 mg / mL, etc.; the mixed concentration of the amino acids is 15-200 mg / mL, for example, it can be 15 mg / mL, 20 mg / mL, 50 mg / mL, 80 mg / mL, 100 mg / mL, 120 mg / mL, 150 mg / mL, 180 mg / mL, 200 mg / mL, etc.; the amino acids include one or more of alanine, glycine, threonine, histidine, and sarcosine.

[0041] In some embodiments of the present invention, the temperature of the hydrothermal reaction is 100-160°C, for example, 100°C, 120°C, 140°C, 160°C, etc.; the time of the hydrothermal reaction is 6-24h, for example, 6h, 12h, 18h, 24h, etc.

[0042] The reactions involved in this invention are all carried out in an air environment. By mixing calcined magnesium aluminum hydrotalcite, amino acids and water, a hydrothermal reaction is carried out. By limiting the ratio of calcined magnesium aluminum hydrotalcite to amino acids, the concentration of calcined magnesium aluminum hydrotalcite and the concentration of amino acids, the calcined magnesium aluminum hydrotalcite can be recrystallized to form magnesium aluminum hydrotalcite, and amino acids are intercalated in the magnesium aluminum hydrotalcite to form a hydrogel.

[0043] In some embodiments of the present invention, the method for preparing the calcined magnesium-aluminum hydrotalcite is as follows: The magnesium-aluminum hydrotalcite is heat-treated to obtain the calcined magnesium-aluminum hydrotalcite. The heat treatment includes a first-stage heat treatment and a second-stage heat treatment. The temperature of the first-stage heat treatment is 200-300℃, for example, 200℃, 250℃, 300℃, etc., and the time is 0.5-2 hours, for example, 0.5 hours, 1 hour, 1.5 hours, 2 hours, etc. The temperature of the second-stage heat treatment is 400-500℃, for example, 400℃, 450℃, 500℃, etc., and the time of the second-stage heat treatment is 8-10 hours, for example, 8 hours, 9 hours, 10 hours, etc. It should be noted that the present invention does not specifically limit the particle size of the magnesium-aluminum hydrotalcite, and its particle size has no impact on the present invention.

[0044] This invention utilizes the "memory effect" of hydrotalcite, meaning that when calcined hydrotalcite is immersed in a solution containing specific anions, its originally damaged layered structure exhibits a certain degree of self-repair ability, restoring to an ordered layered structure. Specifically, in this invention, magnesium aluminum hydrotalcite is calcined to transform into calcined magnesium aluminum hydrotalcite, which is then recrystallized in an environment of air and amino acid solution to obtain amino acid intercalated hydrotalcite hydrogel.

[0045] In this invention, after obtaining the amino acid intercalated hydrotalcite hydrogel, it is soaked in a metal ion solution to obtain a metal ion-reinforced amino acid intercalated hydrotalcite hydrogel.

[0046] In some embodiments of the present invention, the concentration of the metal ion solution is 0.05-0.5 mol / L, for example, it can be 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc., where the concentration of the metal ion solution refers to the concentration of metal ions in the solution; the metal ions in the metal ion solution include one or more of calcium ions, aluminum ions, and zirconium ions; the soaking time is 24-48 hours, for example, it can be 24 hours, 30 hours, 36 hours, 40 hours, 48 ​​hours, etc., and the soaking process can be carried out in a mold or any container, without special limitation. The present invention effectively enhances the mechanical properties of amino acid intercalated hydrotalcite hydrogels by soaking them in divalent, trivalent, or tetravalent metal ion solutions.

[0047] In this invention, after obtaining a metal ion-enhanced amino acid intercalated hydrotalcite hydrogel, solvent replacement is performed, followed by supercritical drying to obtain a composite aerogel.

[0048] In some embodiments of the present invention, the solvent replacement involves immersing the metal ion-reinforced amino acid intercalated hydrotalcite hydrogel in an organic solvent. Specifically, solvent replacement can completely remove the original solvent (water) from the metal ion-reinforced amino acid intercalated hydrotalcite hydrogel to facilitate subsequent supercritical drying.

[0049] In some embodiments of the present invention, the volume ratio of the metal ion-reinforced amino acid intercalated hydrotalcite hydrogel to the organic solvent is 1:10-20, for example, 1:10, 1:15, 1:20, etc.; the organic solvent includes one or more of ethanol, methanol, isopropanol, and acetone; the number of impregnations is 3-6 times, for example, 3, 4, 5, 6 times, etc., and the impregnation time for each time is 6-12 hours, for example, 6 hours, 8 hours, 10 hours, 12 hours, etc. Through multiple impregnations, the water in the amino acid intercalated hydrotalcite hydrogel can be completely replaced.

[0050] In some embodiments of the present invention, the pressure of the supercritical drying is 9-9.8 MPa, for example, 9 MPa, 9.2 MPa, 9.4 MPa, 9.6 MPa, 9.8 MPa, etc., the temperature is 35-40℃, for example, 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, etc., and the time is 0.5-1.5h, for example, 0.5h, 1h, 1.5h, etc.

[0051] This invention employs supercritical drying, which allows organic solvents to penetrate more uniformly into the metal ion-reinforced amino acid-intercalated hydrotalcite hydrogel. This facilitates the better displacement of the original solvent within the hydrogel, contributing to the formation of a uniformly distributed and smaller pore structure. The resulting composite aerogel is denser and harder, thus improving its mechanical properties. Research has shown that other drying methods (such as freeze-drying) cannot produce the composite aerogel of this invention.

[0052] On the other hand, the present invention also provides a metal ion-reinforced amino acid intercalated hydrotalcite composite aerogel prepared by any of the methods described above. This composite aerogel is prepared using the methods described above, and thus possesses all the features and advantages of the methods described above.

[0053] This invention combines metal ions, a rigid crystalline phase (magnesium aluminum hydrotalcite), and a flexible amorphous phase (amino acids) to synthesize a composite aerogel with an organic-inorganic hybrid cross-linked structure, which can effectively reduce the brittleness of the material, increase the degree of crystallinity, and thus improve the mechanical strength of the composite aerogel.

[0054] The technical solutions of this invention will be clearly and completely described below with reference to specific embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Example 1

[0055] This embodiment provides a method for preparing a metal ion-reinforced amino acid-intercalated hydrotalcite composite aerogel, the specific steps of which are as follows:

[0056] (1) Under air atmosphere, magnesium aluminum hydrotalcite (Mg / Al LDH) was subjected to a first stage heat treatment at 250℃ for 1 h, and then subjected to a second stage heat treatment at 450℃ for 10 h to obtain calcined magnesium aluminum hydrotalcite (Mg / Al LDO).

[0057] (2) Mg / Al LDO and sarcosine were added to ultrapure water at a mass ratio of 1:2, stirred and mixed, and then hydrothermally reacted at 100℃ for 10h to obtain amino acid intercalated hydrotalcite hydrogel, wherein the mixed concentration of Mg / Al LDO was 60mg / mL and the mixed concentration of sarcosine was 120mg / mL.

[0058] (3) The amino acid intercalated hydrotalcite hydrogel was placed in a mold and soaked in a 0.05 mol / L calcium ion solution for 24 h to obtain a metal ion reinforced amino acid intercalated hydrotalcite hydrogel.

[0059] (4) The metal ion-reinforced amino acid intercalated hydrotalcite hydrogel was impregnated in 10 times its volume of ethanol for solvent replacement, and the impregnation was repeated 3 times, each time for 12 hours. Then, the impregnated gel was subjected to supercritical drying at 40°C and 9.8 MPa for 1 hour to obtain a composite aerogel, such as... Figure 1 As shown in the left-hand image. Example 2

[0060] This embodiment provides a method for preparing a metal ion-reinforced amino acid-intercalated hydrotalcite composite aerogel, the specific steps of which are as follows:

[0061] (1) Magnesium aluminum hydrotalcite (Mg / Al LDH) was subjected to a first-stage heat treatment at 250℃ for 0.5h in an air atmosphere, and then subjected to a second-stage heat treatment at 450℃ for 10h to obtain calcined magnesium aluminum hydrotalcite (Mg / Al LDO).

[0062] (2) Mg / Al LDO and threonine were added to ultrapure water at a mass ratio of 2:1, stirred and mixed, and then hydrothermally reacted at 140℃ for 10h to obtain amino acid intercalated hydrotalcite hydrogel, wherein the mixed concentration of Mg / Al LDO was 60mg / mL and the mixed concentration of threonine was 30mg / mL.

[0063] (3) The amino acid intercalated hydrotalcite hydrogel was placed in a mold and soaked in a 0.1 mol / L aluminum ion solution for 24 h to obtain a metal ion reinforced amino acid intercalated hydrotalcite hydrogel.

[0064] (4) The metal ion-reinforced amino acid intercalated hydrotalcite hydrogel was impregnated in 10 times its volume of ethanol for solvent replacement, and the impregnation was repeated 3 times, each time for 12 hours. Then, the impregnated gel was subjected to supercritical drying at 35°C and 9.5 MPa for 1 hour to obtain a composite aerogel, such as... Figure 1 As shown in the middle image. Example 3

[0065] This embodiment provides a method for preparing a metal ion-reinforced amino acid-intercalated hydrotalcite composite aerogel, the specific steps of which are as follows:

[0066] (1) Under air atmosphere, magnesium aluminum hydrotalcite (Mg / Al LDH) was subjected to a first stage heat treatment at 250℃ for 1 h, and then subjected to a second stage heat treatment at 450℃ for 10 h to obtain calcined magnesium aluminum hydrotalcite (Mg / Al LDO).

[0067] (2) Mg / Al LDO and glycine were added to ultrapure water at a mass ratio of 1:1, stirred and mixed, and then hydrothermally reacted at 140℃ for 10h to obtain amino acid intercalated hydrotalcite hydrogel, wherein the mixed concentration of Mg / Al LDO was 80mg / mL and the mixed concentration of glycine was 80mg / mL.

[0068] (3) The amino acid intercalated hydrotalcite hydrogel was placed in a mold and soaked in a 0.05 mol / L zirconium ion solution for 24 h to obtain a metal ion reinforced amino acid intercalated hydrotalcite hydrogel.

[0069] (4) The metal ion-reinforced amino acid intercalated hydrotalcite hydrogel was impregnated in 10 times its volume of isopropanol for solvent replacement, and the impregnation was repeated 3 times, each time for 12 hours. Then, the impregnated gel was subjected to supercritical drying at 40°C and 9.8 MPa for 1.5 hours to obtain a composite aerogel, such as... Figure 1 As shown in the diagram on the right.

[0070] The compressive strength of the composite aerogels prepared in Examples 1-3 was tested in this invention, such as... Figure 2 As shown, the composite aerogels prepared in Examples 1-3 correspond to the composite aerogels prepared from left to right. They can withstand 606 times, 1176 times, and 666 times their own weight, respectively, indicating that the composite aerogels prepared in this invention have good mechanical properties.

[0071] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a metal ion-reinforced amino acid-intercalated hydrotalcite composite aerogel, characterized in that, Includes the following steps: (1) The calcined magnesium aluminum hydrotalcite, amino acids and water were mixed and subjected to a hydrothermal reaction to obtain an amino acid intercalated hydrotalcite hydrogel. (2) The amino acid intercalated hydrotalcite hydrogel is immersed in a metal ion solution to obtain a metal ion-reinforced amino acid intercalated hydrotalcite hydrogel; the metal ions in the metal ion solution include one or more of calcium ions, aluminum ions and zirconium ions. (3) The metal ion-reinforced amino acid intercalated hydrotalcite hydrogel was subjected to solvent replacement and then supercritical drying to obtain a composite aerogel. The method for preparing the calcined magnesium aluminum hydrotalcite is as follows: Magnesium aluminum hydrotalcite is heat-treated to obtain calcined magnesium aluminum hydrotalcite. The heat treatment includes a first-stage heat treatment and a second-stage heat treatment. The temperature of the first stage of heat treatment is 200-300℃, and the time is 0.5-2h; The second stage of heat treatment is carried out at a temperature of 400-500℃ for 8-10 hours.

2. The preparation method of the metal ion-reinforced amino acid intercalated hydrotalcite composite aerogel according to claim 1, characterized in that, The mass ratio of the calcined magnesium aluminum hydrotalcite to the amino acid is 1:0.5-2; The concentration of the calcined magnesium aluminum hydrotalcite is 30-100 mg / mL; The mixed concentration of the amino acids is 15-200 mg / mL; The amino acids include one or more of alanine, glycine, threonine, histidine, and sarcosine.

3. The preparation method of the metal ion-reinforced amino acid intercalated hydrotalcite composite aerogel according to claim 1, characterized in that, The hydrothermal reaction is carried out at a temperature of 100-160℃ for 6-24 hours.

4. The preparation method of the metal ion-reinforced amino acid intercalated hydrotalcite composite aerogel according to claim 1, characterized in that, The concentration of the metal ion solution is 0.05-0.5 mol / L.

5. The preparation method of the metal ion-reinforced amino acid intercalated hydrotalcite composite aerogel according to claim 1, characterized in that, The soaking time is 24-48 hours.

6. The method for preparing the metal ion-reinforced amino acid intercalated hydrotalcite composite aerogel according to claim 1, characterized in that, The solvent replacement involves immersing the metal ion-enhanced amino acid intercalated hydrotalcite hydrogel in an organic solvent.

7. The method for preparing the metal ion-reinforced amino acid intercalated hydrotalcite composite aerogel according to claim 6, characterized in that, The volume ratio of the metal ion-enhanced amino acid intercalated hydrotalcite hydrogel to the organic solvent is 1:10-20. The organic solvent includes one or more of ethanol, methanol, isopropanol, and acetone; The immersion is repeated 3-6 times, with each immersion lasting 6-12 hours.

8. The method for preparing the metal ion-reinforced amino acid intercalated hydrotalcite composite aerogel according to claim 1, characterized in that, The supercritical drying process is carried out at a pressure of 9-9.8 MPa, a temperature of 35-40℃, and a time of 0.5-1.5 h.

9. A metal ion-enhanced amino acid intercalated hydrotalcite composite aerogel prepared by the method of any one of claims 1-8.

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