阅读说明：本技术 一种镁铝水滑石制备方法 (Preparation method of magnesium-aluminum hydrotalcite ) 是由 刘志启 吴青山 赵鹏程 潘敬伟 周自圆 李娜 刘丽芳 于 2021-07-12 设计创作，主要内容包括：本发明公开了一种镁铝水滑石制备方法,包括以下步骤：S1、取用镁源和铝源,将镁源和铝源加入至转化剂溶液中配成混合浆料,其中转化剂溶液中,溶质为含氧酸钠盐的混合物或含氧酸钠盐和钠碱的混合物；S2、将混合浆料在设定温度搅拌反应一段时间；S3、反应结束后进行抽滤、洗涤、干燥得到镁铝水滑石。本发明操作步骤简单,所制备的镁铝水滑石产物具有粒径分布小、副产物少、纯度高、形貌规整、不含难除去的阴离子等特点。(The invention discloses a preparation method of magnesium-aluminum hydrotalcite, which comprises the following steps: s1, taking a magnesium source and an aluminum source, adding the magnesium source and the aluminum source into a transforming agent solution to prepare a mixed slurry, wherein in the transforming agent solution, a solute is a mixture of oxygen-containing acid sodium salt or a mixture of the oxygen-containing acid sodium salt and sodium base; s2, stirring and reacting the mixed slurry at a set temperature for a period of time; and S3, after the reaction is finished, carrying out suction filtration, washing and drying to obtain the magnesium-aluminum hydrotalcite. The preparation method has simple operation steps, and the prepared magnesium-aluminum hydrotalcite product has the characteristics of small particle size distribution, few byproducts, high purity, regular appearance, no anion which is difficult to remove and the like.)

1. The preparation method of the magnesium-aluminum hydrotalcite is characterized by comprising the following steps:

s1, taking a magnesium source and an aluminum source, adding the magnesium source and the aluminum source into a transforming agent solution to prepare a mixed slurry, wherein:

the ratio of the amount of the magnesium source to the amount of the aluminum source is 1: 1-4: 1;

in the transforming agent solution, the solution is water, the solute is any one or two of a mixture A and a mixture B which are mixed according to any proportion, the mixture A is formed by mixing sodium carbonate and sodium metaaluminate according to any proportion, the mixture B is formed by mixing sodium bicarbonate and sodium metaaluminate according to any proportion, and the mass fraction of the transforming agent solution is 5-20%;

the solid content of the finally prepared mixed slurry is 5-10 percent; wherein the molar ratio relationship among the magnesium source, the aluminum source and the transforming agent solution is 1:1: 1-4: 1:2, the molar ratio of carbonate or bicarbonate radical in the transforming agent to sodium metaaluminate is 5: 1-12: 1, and the molar ratio in the transforming agent isOrThe amount of the substance(s) of (a) is 2 times the amount of the aluminum source substance(s);

s2, stirring and reacting the mixed slurry obtained in the step S1 at a set temperature for a period of time;

and S3, after the reaction is finished in the step S2, carrying out suction filtration to obtain a reactant, and washing and drying the reactant to obtain the magnesium-aluminum hydrotalcite.

2. The method of claim 1, wherein in step S1, the magnesium source is one or two of magnesium hydroxide and magnesium oxide mixed at any ratio.

3. The method of claim 1, wherein in step S1, the aluminum source is one or two of aluminum hydroxide and aluminum oxide mixed at any ratio.

4. The method for preparing the magnesium-aluminum hydrotalcite of claim 1, wherein in the step S2, the mixed slurry is added into a hydrothermal reaction kettle for stirring reaction, and the hydrothermal time of the hydrothermal reaction kettle is 1-10 h, so that the temperature of the hydrothermal reaction kettle reaches the set temperature of 120-200 ℃.

5. The method for preparing the magnesium-aluminum hydrotalcite of claim 1 or 4, wherein the stirring speed of the hydrothermal reaction kettle is controlled to be 200 to 700r/min during the stirring reaction in the step S2.

6. The method of claim 1, wherein in step S3, the reactants are washed with deionized water three times or more.

7. The method for preparing magnesium aluminum hydrotalcite according to claim 1, wherein the drying is performed at a temperature of 60 to 90 ℃ in step S3.

8. The method of claim 1, wherein in step S1, the mass fraction of the transforming agent solution is 9.7%.

9. The method of claim 1, wherein in step S1, the molar ratio of the magnesium source to the aluminum source to the conversion agent solution is 2.5:1: 2.

10. The method of claim 1, wherein in step S1, the transforming agent is added to the magnesium-aluminum hydrotalciteThe amount of the substance(s) isOr1/11 for the amount of substance(s).

Technical Field

The invention relates to the field of inorganic material preparation methods, in particular to a preparation method of magnesium-aluminum hydrotalcite.

Background

Magnesium aluminum hydrotalcite (MgAl-LDH for short) is a very typical layered anionic compound, and LDHs has very common application in the aspects of polymer stability, flame retardance, medical carriers, water treatment and the like due to the special layered structure and strong anion exchange capacity of the LDHs.

The number of hydrotalcites formed naturally is now small (mainly concentrated in the Wularshan mountain and Norway) and mostly occurs in the form of spinels, and it is difficult to separate these impurities to obtain purer hydrotalcites. Therefore, the hydrotalcite synthesized by manpower to obtain high-purity hydrotalcite becomes the first choice. Although the synthesis methods of hydrotalcite are numerous, the relevant literature summarizes that the main methods for preparing magnesium-aluminum hydrotalcite are coprecipitation method, hydrothermal method, ion exchange method, and the like. The coprecipitation method is the most commonly used method, and has the greatest advantage that the hydrotalcite can be obtained by adjusting the ratio of divalent to trivalent ions, but since the coprecipitation method is used, the pH value and temperature of the reaction need to be carefully controlled, and the synthesized hydrotalcite has non-uniform particles and large particle size.

In the prior art, in a patent (application number 201210273420.8) of "a preparation method of magnesium-aluminum hydrotalcite" applied by wangli, et al, soluble magnesium salt and aluminum salt are respectively used as a magnesium source and an aluminum source in the preparation process, so that anions which are difficult to remove, such as chloride ions, nitrate ions and the like, are introduced into an experimental system, and the purity of the obtained magnesium-aluminum hydrotalcite is not high.

In the prior art, in a patent (application number 200710018710.7) of 'a method for preparing nano magnesium-aluminum hydrotalcite and equipment thereof' applied in guo xiaucai et al, water and sodium hydroxide are required to be added every 20min in the process of preparing hydrotalcite, the operation steps are relatively complicated, and soluble magnesium salt and aluminum salt are adopted as a magnesium source and an aluminum source in the preparation process, so that anions which are difficult to remove exist in the product and are difficult to remove, and the purity is not high.

In the prior art, a patent (application number 201110027316.6) of a new method for preparing magnesium aluminum hydrotalcite, such as dried plum, and the like, needs to continuously drop magnesium salt by ammonia water in the preparation process to obtain magnesium hydroxide, so that raw materials are difficult to obtain.

In the prior art, Wang Xiaoka et al used magnesium oxide, aluminum hydroxide and CO in the patent of a magnesium-aluminum hydrotalcite and a method for preparing the same (application No. 201611262309.3)₂And the catalyst is used for catalyzing and preparing the hydrotalcite, but the purity of the magnesium-aluminum hydrotalcite prepared by the method is not high, and a plurality of byproducts are generated.

Disclosure of Invention

The invention aims to provide a preparation method of magnesium-aluminum hydrotalcite, and aims to solve the problems of complex operation, high raw material cost and low purity of prepared finished products in the preparation method of magnesium-aluminum hydrotalcite in the prior art.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the preparation method of the magnesium-aluminum hydrotalcite is characterized by comprising the following steps:

s1, taking a magnesium source and an aluminum source, adding the magnesium source and the aluminum source into a transforming agent solution to prepare a mixed slurry, wherein:

the ratio of the amount of the magnesium source to the amount of the aluminum source is 1: 1-4: 1;

in the transforming agent solution, the solution is water, the solute is any one or two of a mixture A and a mixture B which are mixed according to any proportion, the mixture A is formed by mixing sodium carbonate and sodium metaaluminate according to any proportion, the mixture B is formed by mixing sodium bicarbonate and sodium metaaluminate according to any proportion, and the mass fraction of the transforming agent solution is 5-20%;

the solid content of the finally prepared mixed slurry is 5-10% (solid content formula:(ii) a Wherein the molar ratio relationship among the magnesium source, the aluminum source and the transforming agent solution is 1:1: 1-4: 1:2, the molar ratio of carbonate or bicarbonate radical in the transforming agent to sodium metaaluminate is 5: 1-12: 1, and the molar ratio in the transforming agent isOrThe amount of the substance(s) of (a) is 2 times the amount of the aluminum source substance(s);

s2, stirring and reacting the mixed slurry obtained in the step S1 at a set temperature for a period of time;

and S3, after the reaction is finished in the step S2, carrying out suction filtration to obtain a reactant, and washing and drying the reactant to obtain the magnesium-aluminum hydrotalcite.

In the further step S1, the magnesium source is one or two of magnesium hydroxide and magnesium oxide mixed at any ratio, wherein magnesium hydroxide is preferred.

In the further step S1, the aluminum source is one or two of aluminum hydroxide and aluminum oxide mixed at an arbitrary ratio, and among them, aluminum hydroxide is preferred.

In a further step S2, the mixed slurry is added into a hydrothermal reaction kettle for stirring reaction, wherein the hydrothermal time of the hydrothermal reaction kettle is 1-10 hours, so that the temperature of the hydrothermal reaction kettle reaches a set temperature of 120-200 ℃, and the optimal value is 140 ℃.

In the step S2, the stirring speed of the hydrothermal reaction kettle is controlled to be 200-700 r/min, wherein the stirring speed is 500r/min as an optimal value.

In a further step S3, the reactant is washed three times or more with deionized water, wherein the number of washes is the optimum value.

In a further step S3, the drying is carried out at a temperature of 60 to 90 ℃, wherein 80 ℃ is the most preferable value.

In the further step S1, the mass fraction of the conversion agent solution was 9.7%.

In a further step S1, the molar ratio between the magnesium source, the aluminum source and the transforming agent solution is 2.5:1: 2.

In a further step S1, in the conversion agentThe amount of the substance(s) isOr1/11 for the amount of substance(s).

The invention relates to a brand-new method for synthesizing ultrapure magnesium aluminum hydrotalcite, and the reaction expression (taking sodium bicarbonate and sodium metaaluminate as transforming agents as examples) of the invention is as follows:

Mg(OH)₂+Al(OH)₃+NaAlO₂+NaHCO₃+H₂O→Mg₆Al₂(OH)₁₆CO₃·4H₂O+ Na₂CO₃

or the following steps:

MgO+Al(OH)₃+ NaHCO₃+H₂O→Mg₆Al₂(OH)₁₆CO₃·4H₂O+ Na₂CO₃

wherein sodium carbonate or sodium bicarbonate provides an alkaline environment for the reaction. The double hydrolysis of metaaluminate and carbonate or bicarbonate radical further ensures the alkaline condition of the system, and simultaneously, the aluminum source of the reaction can be used as the aluminum source because of containing aluminum element. Meanwhile, because anions (chloride ions, sulfate ions and the like) which are difficult to remove are not introduced, the purity of the product is high.

Compared with the prior art, the invention has the advantages that:

the method has the characteristics of simple operation steps, small particle size distribution of the prepared magnesium-aluminum hydrotalcite product, few byproducts, high purity, regular appearance, no anion which is difficult to remove and the like. The magnalium hydrotalcite prepared by the invention has the advantages of wide raw material source, low cost, simple operation in the synthetic process, environmental protection and accordance with the concept of green chemistry.

Drawings

Figure 1 is an XRD pattern of various embodiments of the invention.

FIG. 2 is an SEM photograph of example 1 of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided to explain the principles of the invention and its practical application to thereby enable others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated.

The preparation method of the magnesium-aluminum hydrotalcite comprises the following main operation steps:

example 1

1. In this example 1, aluminum hydroxide was used as the aluminum source in an amount of 24.5g, magnesium hydroxide was used as the magnesium source in an amount of 53.80g, sodium bicarbonate and sodium metaaluminate were used as the solute in the conversion agent solution in an amount of 52.75g and 4.89g, respectively, and 780ml of deionized water was added to prepare a mixed slurry having a magnesium-aluminum ratio of 2.5:1 and a solid content of 10%.

2. Adding the slurry into a 2L reaction kettle, adjusting the revolution number to 320r/min, and heating to 140 ℃ for reaction for 4 h.

3. After the reaction is finished, the mixed solution is filtered and washed for three times, and dried for 10 hours at 85 ℃.

Example 2

The process was the same as in example 1 except that the Mg/Al ratio was 3:1 and the hydrothermal temperature was 160 ℃.

1. In this example 2, aluminum hydroxide was used as an aluminum source in an amount of 24.5g, magnesium hydroxide was used as a magnesium source in an amount of 63.49g, sodium bicarbonate and sodium metaaluminate were used as solutes in a conversion agent solution in an amount of 52.75g and 4.89g, respectively, and 880ml of deionized water was added to prepare a mixed slurry having a ratio of magnesium to aluminum of 3:1 and a solid content of 10%.

2. Adding the slurry into a 2L reaction kettle, adjusting the revolution number to 320r/min, and heating to 160 ℃ for reaction for 4 hours.

3. After the reaction is finished, the mixed solution is filtered and washed for three times, and dried for 10 hours at 85 ℃.

Example 3

The process is the same as in example 1 except that the slurry has a solids content of 8%.

1. In this example 3, aluminum hydroxide was used as the aluminum source in an amount of 24.5g, magnesium hydroxide was used as the magnesium source in an amount of 53.80g, sodium bicarbonate and sodium metaaluminate were used as the solute in the conversion agent solution in an amount of 52.75g and 4.89g, respectively, and 978ml of deionized water was added to prepare a mixed slurry having a ratio of magnesium to aluminum of 2.5:1 and a solid content of 10%.

2. Adding the slurry into a 2L reaction kettle, adjusting the revolution number to 320r/min, and heating to 140 ℃ for reaction for 4 h.

3. After the reaction is finished, the mixed solution is filtered and washed for three times, and dried for 10 hours at 85 ℃.

Example 4

The process is the same as example 1, except that the magnesium source is replaced by magnesium oxide and the conversion agent is replaced by sodium bicarbonate.

1. In this example 4, aluminum hydroxide was used as an aluminum source in an amount of 19.5g, magnesium oxide was used as a magnesium source in an amount of 25g, sodium bicarbonate was used as a solute in the conversion agent solution in an amount of 42g, and 450ml of deionized water was added to prepare a mixed slurry having a magnesium-aluminum ratio of 2.5:1 and a solid content of 10%.

2. Adding the slurry into a 2L reaction kettle, adjusting the revolution number to be 500r/min, and heating to 140 ℃ for reaction for 4 h.

3. After the reaction is finished, the mixed solution is filtered and washed for three times, and dried for 10 hours at 85 ℃.

XRD tests are respectively carried out on the products in the above examples 1-4, and as can be seen from figure 1, XRD diffraction peaks of the products obtained in the above examples 1 and 4 are consistent with standard spectrograms of No. 14-0196 magnesium aluminum hydrotalcite issued by the International centre for diffraction data, and correspond to (003), (006) and (009) crystal planes respectively at 11 degrees, 22 degrees and 34 degrees, the base line is stable, the characteristic peak patterns are sharp and are symmetrically distributed, and the better purity of the synthesized crystal planes is indicated. And no obvious impurity peak exists, which indicates that the synthesized hydrotalcite has high purity; as can be seen from the SEM image of FIG. 2, the magnalium hydrotalcite synthesized by the method of the invention has uniform and regular micro-morphology and is in a hexagonal flaky shape. Based on this comparison, example 1 is the best method for preparing magnesium aluminum hydrotalcite.

The embodiments of the present invention are described only for the preferred embodiments of the present invention, and not for the limitation of the concept and scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the design concept of the present invention shall fall into the protection scope of the present invention, and the technical content of the present invention which is claimed is fully set forth in the claims.