A method for controllably preparing a porous structure-like hydrotalcite

Abstract

The present invention belongs to the technical field of preparation of hydrotalcite-like compounds, and specifically relates to a method for controllable preparation of a hydrotalcite-like compound with a porous structure. In the nucleation and growth stages of LDH, SMA with a low molecular weight and a high anhydride content is added, so that LDH laminar plates with different hydrophobicities can be disorderly stacked during the sedimentation process, thus avoiding the problems that the hydrotalcite prepared by the template method is prone to exfoliation and the original structure of the hydrotalcite-like compound is easily damaged by the alkali etching method. The stacking method adopted by the present invention can obtain a hydrotalcite-like compound with a porous structure on the surface by control.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of hydrotalcite-like compounds, and particularly relates to a controllable preparation method of a hydrotalcite-like compound with a porous structure. Background Art

[0002] Hydrotalcite is a kind of layered double hydroxides with a layered structure, which is composed of a positively charged metal hydroxide layer and interlayer balancing anions. Hydrotalcite-like compounds can be calcium-aluminum hydrotalcite, nickel-iron hydrotalcite, magnesium-strontium-iron hydrotalcite, magnesium-iron hydrotalcite, etc. LDHs not only have a stable layered structure, a high aspect ratio, a large specific surface area and rich interlayer interfaces, but also have good biocompatibility, and are widely used in the fields of catalysis, adsorption, medicine, etc.

[0003] Due to the strong covalent bond action in the hydrotalcite layer board and a weak interaction force in the interlayer, that is, the interlayer guest anions and the main layer board are connected by weak chemical bonds such as electrostatic attraction, hydrogen bonds or van der Waals forces, the hydrotalcite-like compound layer boards are closely stacked, and the prepared hydrotalcite-like compound usually has no pores on the surface, which limits its application. At present, the preparation of porous hydrotalcite mostly adopts the template method. For example, Chinese Patent with publication number CNN114848897A discloses a porous hydroxyapatite-hydrotalcite composite material, its preparation method and application, which is prepared by in-situ growth on the surface of other porous materials, but the hydrotalcite obtained by this method has a poor binding force with the surface of the porous material and is easy to peel off from the surface of the porous material. Chinese Patent with publication number CN113299490A discloses a preparation method of a porous structure nickel-titanium-aluminum hydrotalcite supercapacitor electrode material, which is to carry out alkali etching on hydrotalcite powder in an NaOH solution to obtain a hydrotalcite-like compound with a porous nanostructure, but this method is easy to damage the original structure of the hydrotalcite-like compound.

[0004] Therefore, it is necessary to provide a controllable preparation method of a porous hydrotalcite-like compound to solve the above problems. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a controllable preparation method of a hydrotalcite-like compound with a porous structure.

[0006] Specifically, it is realized through the following technical solutions:

[0007] 1. A controllable preparation method of a hydrotalcite-like compound with a porous structure, characterized by including the following steps:

[0008] S1: In a mixed metal salt solution containing divalent metal ions and trivalent metal ions, use an alkali solution to adjust the pH value during the reaction process so that the pH value of the system does not exceed 10;

[0009] Further, the divalent metal ions in the divalent metal ion salt are divalent metal ions capable of forming hydroxides, specifically Mg 2+ , Co 2+ , Ni 2+ , Zn 2+ , Cu 2+ , Mn 2+ , Ca 2+ ; The trivalent metal ions in the trivalent metal ion salt are trivalent metal ions capable of forming hydroxides, specifically Al 3+ , Fe 3+ , Co 3+ , Cr 3+ , Ga 3+ ; The anion in the mixed metal salt solution is NO 3- , and the molar ratio of divalent metal ions to trivalent metal ions is (2 - 5):(1 - 3); The mass ratio of the trivalent metal ion salt to the SMA is 1:(1 - 5);

[0010] Further, the reaction temperature is 25 - 80 °C, and the alkaline solution is one of sodium hydroxide solution or potassium hydroxide solution;

[0011] S2: Add SMA to the mixed solution after the reaction in S1, and stir magnetically for 6 - 48 h;

[0012] The SMA has a molecular weight of 5500 and a maleic anhydride content of 42%;

[0013] S3: Add a certain amount of solvent to the mixed solution after the reaction in S2, and continue to stir for 0.5 - 3 h;

[0014] Further, the organic solvent is a water-soluble solvent, specifically one of methanol, ethanol, propanol, and N,N-dimethylacetamide; The volume ratio of the LDH mixed solution to the solvent is 1 - 0.2:1;

[0015] S4: Pour out the supernatant, and place the precipitate obtained by centrifugation in an oven at 60 °C to dry, then the porous layered double hydroxide is obtained.

[0016] In summary, the beneficial effects of the present invention are as follows: During the nucleation and growth stages of LDH, SMA with a low molecular weight and a high anhydride content is added. The SMA undergoes ring-opening under alkaline conditions to obtain an SMA salt with the property of being soluble in water but insoluble in solvents. Utilizing this property, after the aging of LDH (at this time, part of the SMA enters the LDH lamellar space as an interlayer anion, and part of the SMA salt exists in the aging solution), a water-soluble solvent is added to precipitate part of the SMA salt from the aqueous solution, and the precipitated SMA deposits on the surface of LDH. On the one hand, since the organically modified hydrotalcite has a certain hydrophobic property, while the SMA salt has a hydrophilic property, the SMA salt deposited on the surface of LDH plays a role in hydrophilic modification, which can regulate the hydrophobicity of the hydrotalcite-like material. On the other hand, the more the SMA salt precipitates, more SMA salt deposits on the surface of LDH, and under the action of gravity, LDH settles in the solution, enabling the disordered stacking of LDH lamellae with different hydrophobicities during the sedimentation process, thereby generating a porous structure, and controlling the formation of a hydrotalcite-like material with a porous structure on the surface. This avoids the problems in the prior art that the template method for preparing hydrotalcite is prone to exfoliation and the alkali etching method is prone to damaging the original structure of the hydrotalcite-like material. Description of the Drawings

[0017] Figure 1 It is an X-ray diffraction experimental pattern; among them, (a) is the pattern of Example 1, (b) is the pattern of Example 2, (c) is the pattern of Example 3, and (d) is the pattern of Example 4.

[0018] Figure 2 It is an infrared experimental pattern; among them, (a) is the pattern of Example 1, (b) is the pattern of Example 2, (c) is the pattern of Example 3, and (d) is the pattern of Example 4.

[0019] Figure 3 It is a comparison diagram of the mixed system solution before and after adding acetone in Example 1.

[0020] Figure 4 It is a SEM image of the porous hydrotalcite-like material prepared in Example 1.

[0021] Figure 5 It is a SEM image of the porous hydrotalcite-like material prepared in Example 2.

[0022] Figure 6 It is a SEM image of the porous hydrotalcite-like material prepared in Example 3.

[0023] Figure 7 It is a SEM image of the porous hydrotalcite-like material prepared in Example 4.

[0024] Figure 8 It is a SEM image of the comparative experiment.

[0025] Figure 9 It is a SEM image of Sample 1.

[0026] Figure 10 SEM image of Sample 2.

[0027] Figure 11 SEM image of Sample 3.

[0028] Figure 12 SEM image of Sample 4. Detailed implementation manners

[0029] The following further elaborates on the detailed implementation manners of the present invention. However, the present invention is not limited to these implementation manners. Any improvement or substitution based on the basic spirit of this embodiment still falls within the scope protected by the claims of the present invention.

[0030] Example 1

[0031] (1) Take 0.025 mol of Mg(NO3)2·6H2O and 0.0125 mol of Al(NO3)3·9H2O and pour them into beaker A1, then add 50 ml of deionized water to dissolve. Add a magnetic stirrer, insert the pH meter into the three-necked flask B1, adjust the temperature in the three-necked flask B1 to 80 °C, adjust the rotation speed of the magnetic stirrer to 500 rpm, and then use sodium hydroxide to adjust the pH value during the reaction. If the pH is less than 10, add sodium hydroxide to keep the pH value of the system around 10. After dropping, add 23.5 g of SMA and stir for another 6 h;

[0032] (2) After the above steps are completed, add 30 ml of acetone to the mixed system solution, stir for 2 h, remove the supernatant to obtain the sediment, and place the sediment in an oven at 60 °C to dry. The obtained product is the porous hydrotalcite-like nanomaterial.

[0033] Example 2

[0034] (1) Take 0.025 mol of Cu(NO3)2·6H2O and 0.0375 mol of Fe(NO3)3·9H2O and pour them into beaker A1, then add 50 ml of deionized water to dissolve. Add a magnetic stirrer, insert the pH meter into the three-necked flask B1, at room temperature, adjust the rotation speed of the magnetic stirrer to 500 rpm, and then use sodium hydroxide to adjust the pH value during the reaction. If the pH is less than 10, add sodium hydroxide to keep the pH value of the system around 10. After dropping, add 15 g of SMA and stir for 48 h;

[0035] (2) After the above steps are completed, add 150 ml of ethanol to the mixed system solution, stir for 0.5 h, remove the supernatant to obtain the sediment, and place the sediment in an oven at 60 °C to dry. The obtained product is the porous hydrotalcite-like nanomaterial.

[0036] Example 3

[0037] (1) Take 0.0625 mol of Ni(NO3)2·6H2O and 0.0125 mol of Fe(NO3)3·9H2O and pour them into beaker A1, then add 50 ml of deionized water to dissolve. Add a magnetic stir bar, insert a pH meter into the three-neck flask B1, adjust the temperature in the three-neck flask B1 to 60 °C, adjust the rotation speed of the magnetic stir bar to 500 rpm, and then use potassium hydroxide to adjust the pH value during the reaction. If the pH is less than 10, supplement potassium hydroxide to keep the pH value of the system around 10 all the time. After dropping, add 15 g of SMA and stir for another 12 h;

[0038] (2) After the above steps are completed, add 100 ml of methanol to the mixed system solution, stir for 1 h, remove the supernatant to obtain a sediment, and put the sediment into an oven at 60 °C to dry. The obtained product is a porous hydrotalcite-like nanomaterial.

[0039] Example 4

[0040] (1) Take 0.0625 mol of Zn(NO3)2·6H2O and 0.0375 mol of Fe(NO3)3·9H2O and pour them into beaker A1, then add 50 ml of deionized water to dissolve. Add a magnetic stir bar, insert a pH meter into the three-neck flask B1, adjust the temperature in the three-neck flask B1 to 70 °C, adjust the rotation speed of the magnetic stir bar to 500 rpm, and then use potassium hydroxide to adjust the pH value during the reaction. If the pH is less than 10, supplement potassium hydroxide to keep the pH value of the system around 10 all the time. After dropping, add 15 g of SMA and stir for another 12 h;

[0041] (2) After the above steps are completed, add 80 ml of N,N-dimethylacetamide to the mixed system solution, stir for 3 h, remove the supernatant to obtain a sediment, and put the sediment into an oven at 60 °C to dry. The obtained product is a porous hydrotalcite-like nanomaterial.

[0042] I. Performance Test of Hydrotalcite-like Compounds

[0043] 1. Perform X-ray diffraction experiments (XRD) on the products prepared in Examples 1-4, and obtain XRD patterns as Figure 1As shown, it can be seen from the figure that the characteristic diffraction peaks of hydrotalcite-like materials appear near the diffraction angles 2θ = 5°, 11.8°, 20.8°, 34.1°, 45.9° and 60.4° / 61.6° for the following several polymer-modified hydrotalcite-like nanocomposites, which respectively correspond to the characteristic peaks of (003), (006), (009), (012), (015), (110) and (113) of hydrotalcite-like materials. Compared with traditional hydrotalcite, the (003) peak of the polymer-modified hydrotalcite-like nanocomposite prepared in this invention shifts towards a lower angle, indicating that SMA has successfully intercalated into the LDH interlayer.

[0044] 2. Infrared spectroscopy experiments were respectively carried out on the products prepared in Examples 1 - 4, as Figure 2 shown. A hydroxyl stretching vibration peak appears near 3500 cm-1; the vibration peak of C-H is near 3000 cm-1; the stretching vibration peaks of carboxyl groups are at 1544 cm-1 and 1408 cm-1; the vibrations of the benzene ring are at 1495 cm-1 and 1454 cm-1; the bending deformation vibration of interlayer water molecules is near 1650 cm-1; the vibration peaks of different metal bonds M-O-M on the layer board are below 1000 cm-1, further proving that SMA has successfully intercalated into the LDH interlayer.

[0045] 3. The mixed system solution of Example 1 and an organic solvent were added dropwise and stirred for a period of time, and the solution conditions were compared. As Figure 3 shown, sedimentation occurred in the mixed system solution with the addition of an organic solvent after stirring for a period of time, while this phenomenon did not occur in the mixed system solution without addition after standing for a period of time, proving that the addition of an organic solvent will cause SMA salt to deposit on the surface of LDH, thus causing LDH to settle from the solution.

[0046] 4. The products prepared in Examples 1 - 4 were respectively placed under a scanning electron microscope for observation, and the obtained SEM images are shown in Figures 4 - 7; it can be seen from the SEM images that the LDH synthesized by this method all has a porous structure on the surface.

[0047] II. Comparative Experiments

[0048] The method of Example 2 was used to prepare porous structure hydrotalcite-like materials, with the difference that the obtained aging solution was directly centrifuged, and the precipitate obtained by centrifugation was thoroughly washed with the same solvent and observed with a scanning electron microscope, as Figure 8 shown.

[0049] It can be known from the experiment that solvent treatment of the precipitate after centrifugation cannot obtain hydrotalcite with open pores on the surface, but pores generated by the stacking of hydrotalcite particles.

[0050] III. Screening Experiments

[0051] 1. Sample Preparation and Experimental Method

[0052] Sample 1: The porous structure hydrotalcite-like compound was prepared by the method of Example 2, except that the type of metal cation was different, and the divalent metal ion was Ni. 2+ , and observed by scanning electron microscope, the SME image is as Figure 9 shown.

[0053] Sample 2: The porous structure hydrotalcite-like compound was prepared by the method of Example 2, except that the amount of solvent used was different, and the content of ethanol was 50 ml. Observed by scanning electron microscope, the SME image is as Figure 10 shown.

[0054] Sample 3: The porous structure hydrotalcite-like compound was prepared by the method of Example 2, except that the stirring time after adding the solvent was 3 h. Observed by scanning electron microscope, the SME image is as Figure 11 shown.

[0055] Sample 4: The LDH electromagnetic shielding film was prepared by the method of Example 2, except that the type of solvent was different, and the solvent used was DMAc. Observed by scanning electron microscope, the SME image is as Figure 12 shown.

[0056] It can be seen from the experimental results that Sample 1, Sample 2, Sample 3 and Sample 4 respectively changed the divalent metal ion to Ni 2+ , reduced the amount of solvent used, increased the mechanical stirring time after adding the solvent, and changed the type of solvent, and all could obtain the LDH with a surface porous structure, but the pore size and pore density were different.

Claims

1. A controllable preparation method of a porous structure hydrotalcite-like compound, characterized in that, It includes the following steps: S1: In a mixed metal salt solution containing divalent metal ions and trivalent metal ions, use an alkali solution to adjust the pH value during the reaction so that the pH value of the system does not exceed 10; S2: Add SMA to the mixed solution after the reaction in S1 and stir magnetically for 6 - 48 h; The divalent metal ion is Mg 2+ , Co 2+ , Ni 2+ , Zn 2+ , Cu 2+ , Mn 2+ , Ca 2+ or one or more of them; the trivalent metal ion is Al 3+ , Fe 3+ , Co 3+ , Cr 3+ , Ga 3+ or one or more of them; the anion in the mixed metal salt solution is NO3 - , the molar ratio of the divalent metal ion to the trivalent metal ion is (2 - 5):(1 - 3); the mass ratio of the trivalent metal ion salt to the SMA is 1:(1 - 5); the molecular weight of the SMA is 5500 and the maleic anhydride content is 42%; S3: Add a certain amount of organic solvent to the mixed solution after the reaction in S2 and continue to stir for 0.5 - 3 h; The organic solvent is one of methanol, ethanol, propanol, and N,N - dimethylacetamide; the volume ratio of the mixed solution to the solvent is 1 - 0.2:1; S4: Pour off the supernatant, place the precipitate obtained by centrifugation in an oven at 60 °C to dry, and thus obtain porous hydrotalcite - like material.

2. The controllable preparation method of a porous structure hydrotalcite-like compound according to claim 1, characterized in that, In step S1, the reaction temperature is 25 - 80 °C, and the alkali solution is one of sodium hydroxide solution or potassium hydroxide solution.

3. A porous structure hydrotalcite-like compound prepared by the controllable preparation method of a porous structure hydrotalcite-like compound according to claim 1 or 2.

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