阅读说明：本技术 一种多孔锂铝水滑石的合成方法 (Method for synthesizing porous lithium-aluminum hydrotalcite ) 是由 李军 董明哲 罗清龙 刘忠 聂国亮 李�权 郭敏 张慧芳 吴志坚 于 2021-09-24 设计创作，主要内容包括：本发明公开了一种多孔锂铝水滑石的制备方法,通过将含有锂盐和铝盐溶液与形貌调控剂,沉淀剂混合溶液进行常压水热反应,然后经过过滤、洗涤、干燥后即可得到多孔锂铝水滑石材料。该方法具有制备工艺简单,不使用高压反应釜,常压即可操作,制备的锂铝水滑石具有介孔、大孔结构,比表面积大,结晶片层结构稳定,形貌规整,利于与其他介质如水、气接触的特点,可应用于卤水提锂、催化、水体有害磷氟吸附等领域。本发明公开的锂铝水滑石材料制备过程简单,常压下即可生产,比表面积大,反应活性高,具有广阔的应用前景。(The invention discloses a preparation method of porous lithium-aluminum hydrotalcite, which comprises the steps of carrying out normal-pressure hydrothermal reaction on a mixed solution containing a lithium salt solution, an aluminum salt solution, a morphology regulating agent and a precipitator, and then filtering, washing and drying to obtain the porous lithium-aluminum hydrotalcite material. The method has the characteristics of simple preparation process, no use of a high-pressure reaction kettle, operation at normal pressure, mesoporous and macroporous structures of the prepared lithium-aluminum hydrotalcite, large specific surface area, stable structure of a crystalline lamellar layer, regular appearance and contribution to contact with other media such as water and gas, and can be applied to the fields of lithium extraction from brine, catalysis, adsorption of harmful phosphorus and fluorine in water and the like. The lithium-aluminum hydrotalcite material disclosed by the invention is simple in preparation process, can be produced under normal pressure, is large in specific surface area and high in reaction activity, and has a wide application prospect.)

1. A synthesis method of porous lithium aluminum hydrotalcite is characterized by comprising the following steps:

carrying out hydrothermal reaction on a mixed solution containing lithium ions, aluminum ions, a precipitating agent and a morphology regulating agent, washing the solid obtained after the reaction with water, and drying to obtain a product, namely the porous lithium-aluminum hydrotalcite;

the concentration of lithium ions in the mixed solution is 0.3-1.2 mol/L;

the concentration of aluminum ions in the mixed solution is 0.15-0.40 mol/L;

the precipitator is an alkaline precipitator, and the amount of the precipitator is 1-20: 1 of the molar ratio of hydroxide radicals to aluminum ions in the precipitator;

the morphology regulator is one or more of oleylamine, octadecylamine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, dodecyl imidazoline, polyethyleneimine, polyacrylamide, lauryl sodium sulfate, sodium dodecyl benzene sulfonate, hexadecyl trimethyl ammonium bromide, span-60, span-80, tween-60, potassium alkyl phosphate and sodium stearate, and the molar ratio of the dosage of the morphology regulator to the aluminum ions is 1: 1-80;

the pressure of the hydrothermal reaction is normal pressure, the reaction temperature is 85-95 ℃, and the reaction time is 12-24 hours.

2. The method for synthesizing porous lithium aluminum hydrotalcite according to claim 1, wherein the precipitant is added to the reaction system at a single time during the initial period of the reaction or at a constant rate during the reaction.

3. The method for synthesizing porous lithium aluminum hydrotalcite according to claim 1, wherein the aluminum ions are derived from one or more of aluminum nitrate, aluminum chloride and aluminum sulfate.

4. The method for synthesizing porous lithium aluminum hydrotalcite according to claim 1, wherein the lithium ions are derived from one or more of lithium chloride, lithium sulfate and lithium nitrate.

5. The method for synthesizing porous lithium aluminum hydrotalcite according to claim 1, wherein the alkaline precipitant is one or more of urea, ammonia water, sodium hydroxide and potassium hydroxide.

6. The method for synthesizing porous lithium aluminum hydrotalcite according to claim 1, wherein when the alkaline precipitant is a precipitant containing urea, the alkaline precipitant is added at one time during the initial stage of the reaction; when the alkaline precipitant is ammonia water, the alkaline precipitant is gradually added at a certain speed in the reaction process.

7. The method for synthesizing porous lithium aluminum hydrotalcite according to claim 1, wherein the solid product obtained by the reaction is washed with water, and the washing process is carried out with deionized water at 80-90 ℃.

8. The method for synthesizing porous lithium aluminum hydrotalcite according to claim 1, wherein the drying temperature is 40-80 ℃ and the drying time is 12-24 hours.

9. The method for synthesizing the porous lithium aluminum hydrotalcite according to claim 1, wherein the molecular weight of polyethyleneimine is 300 to 10000, and the solution concentration is 50%; the polymerization degree of the polyacrylamide is 800-1000 ten thousand.

10. The application of the porous lithium aluminum hydrotalcite prepared by the synthesis method according to claim 1 in the lithium element extraction process, in particular as an adsorbent.

Technical Field

The invention belongs to the technical field of inorganic chemistry, and particularly relates to a synthesis method of porous lithium-aluminum hydrotalcite.

Background

The hydrotalcite layered double hydroxide is a compound which is assembled by a main body laminate with positive charge consisting of divalent metal ions and trivalent metal ions, interlayer anions and water molecules through the interaction of non-covalent bonds, belongs to an anionic layered compound, has exchangeability and is an inorganic material with a layered structure. The specific molecular formula can be expressed as [ M_1-x ²⁺M³⁺(OH)₂]^x+[A_x/n]ⁿmH₂And O. The hydrotalcite has the characteristics of variable types and proportions of main layer plate elements, adjustable interlaminar anions, controllable grain size and thickness and the like, and has various appearance changes and uniform layer plate element distribution. Due to their unique structure, special properties and wide application, they are widely used in the fields of catalysis, energy, biology, medicine and materials. Lithium aluminum hydrotalcite has a crystalline aluminum hydroxide structure similar to brucite, with one-third of the octahedral metal cation vacancies, i.e., the Al3+ ions, accounting for only two-thirds of the octahedral cation vacancies. When the vacancies in the aluminum hydroxide layer are filled with Li +, lithium aluminum hydrotalcite is formed, giving excess positive charge for interlayer anion neutralization. The synthesis, structure and properties of lithium aluminum based hydrotalcite have been widely studied. Lithium aluminum hydrotalcite in catalyst, waste water treatment adsorbent and CO₂Has wide application prospect in the aspects of trapping, metal corrosion and protection, lithium ion batteries and the like. Methods for synthesizing lithium aluminum hydrotalcite are numerous, such as lithium salt or LiOH intercalation into aluminum hydroxide by coprecipitationThe synthesis is carried out by a precipitation method, a hydrothermal method, a mechanochemical method and the like. The common industrial synthesis mode is that aluminum hydroxide and lithium hydroxide are hydrothermally synthesized and then are dripped into a mixed solution of aluminum salt and lithium salt through hydrochloric acid neutralization or a precipitator for coprecipitation, the crystallization form of the method is not easy to control, and the adsorption or catalytic performance of a finished product is poor due to the accumulation of the shape.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for synthesizing porous lithium aluminum hydrotalcite, which has the advantages of simple synthesis conditions, easy production, regular appearance of the product lithium aluminum hydrotalcite, higher specific surface area and wide application prospect.

The invention is realized by the following technical scheme:

a synthesis method of porous lithium aluminum hydrotalcite comprises the following steps:

carrying out hydrothermal reaction on a mixed solution containing lithium ions, aluminum ions, a precipitating agent and a morphology regulating agent, washing the solid obtained after the reaction with water, and drying to obtain a product, namely the porous lithium-aluminum hydrotalcite;

the concentration of lithium ions in the mixed solution is 0.3-1.2 mol/L;

the concentration of aluminum ions in the mixed solution is 0.15-0.40 mol/L;

the precipitator is an alkaline precipitator, and the amount of the precipitator is 1-20: 1 of the molar ratio of hydroxide radicals to aluminum ions in the precipitator;

the morphology regulator is one or more of oleylamine, octadecylamine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, dodecyl imidazoline, polyethyleneimine, polyacrylamide, lauryl sodium sulfate, sodium dodecyl benzene sulfonate, hexadecyl trimethyl ammonium bromide, span-60, span-80, tween-60, potassium alkyl phosphate and sodium stearate, and the molar ratio of the dosage of the morphology regulator to the aluminum ions is 1: 1-80;

the pressure of the hydrothermal reaction is normal pressure, the reaction temperature is 85-95 ℃, and the reaction time is 12-24 hours.

In the above technical scheme, the precipitant can be added at one time at the initial stage of the reaction, or can be added into the reaction system at a certain speed in the reaction process.

In the technical scheme, the aluminum ions are from one or more of aluminum nitrate, aluminum chloride and aluminum sulfate.

In the technical scheme, the lithium ions are one or more of lithium chloride, lithium sulfate and lithium nitrate.

In the technical scheme, the alkaline precipitator is one or more of urea, ammonia water, sodium hydroxide and potassium hydroxide.

In the technical scheme, when the alkaline precipitator is a precipitator containing urea or ammonia water, the alkaline precipitator is added at one time in the initial reaction stage; when the precipitant does not contain urea, the precipitant is gradually added at a certain speed in the reaction process. When the precipitator is urea or ammonia water, the precipitator is added at one time, gradually decomposes in the heating process, releases ammonia, and plays a role of gradual precipitation; the precipitant, ammonia when added dropwise, changes the reaction too quickly.

In the technical scheme, the solid product obtained by the reaction is washed by water, and the washing process adopts deionized water at the temperature of 80-90 ℃ for washing. The higher temperature deionized water is used for washing the crystal particles which can be washed to remove salt, and the cleaning capability is stronger compared with the low temperature water.

In the technical scheme, the drying temperature is 40-80 ℃ and the drying time is 12-24 hours in the drying process.

In the technical scheme, the molecular weight of the polyethyleneimine is 300-10000, and the solution concentration is 50%; the polymerization degree of the polyacrylamide is 800-1000 ten thousand.

The porous lithium aluminum hydrotalcite is applied to the extraction process of lithium elements.

The porous lithium aluminum hydrotalcite is applied as an adsorbent in the process of extracting lithium elements.

The invention has the advantages and beneficial effects that:

the invention synthesizes the lithium aluminum hydrotalcite with regular crystallization form and porous structure through the function of the morphology regulator. Can be applied to the recycling of lithium resources in salt lakes and seawater; adsorbing phosphorus and fluorine elements in the wastewater; the catalyst has the characteristics of porous structure, higher specific surface area, thinner lamella and the like, and has wide application prospect.

The preparation method provided by the invention is simple and safe, the porous lithium aluminum hydrotalcite material is obtained by a hydrothermal method under normal pressure, the product has a mesoporous and macroporous structure, the specific surface area is high, the morphological structure is regular, the morphological control agent can promote the crystallization of the lithium aluminum hydrotalcite, and the yield is improved. Suitable as an adsorbent or catalytic material.

In the prior art, hydrotalcite with the morphology is generally synthesized in a pressurized reaction kettle. In the application, a surfactant with a certain concentration is used for forming a critical micelle in a solution, the critical micelle has a function of regulating and controlling the morphology in the crystallization process of the lithium-aluminum hydrotalcite, and generally, different types of surfactants for controlling crystallization are different in type and concentration, so that how to determine the type of the surfactant for controlling the crystallization morphology of the lithium-aluminum hydrotalcite and the concentration range of the surfactant in the solution are key factors.

Drawings

FIG. 1 is a representation of porous lithium aluminum hydrotalcite prepared in example 1 of the present invention, wherein a) is a scanning electron micrograph; b) is an XRD pattern.

FIG. 2 is a representation of porous lithium aluminum hydrotalcite prepared in example 2 of the present invention, wherein a) is a scanning electron micrograph; b) is an XRD pattern.

FIG. 3 is a representation of porous lithium aluminum hydrotalcite prepared in example 3 of the present invention, wherein a) is a scanning electron micrograph; b) is an XRD pattern.

FIG. 4 is a representation of porous lithium aluminum hydrotalcite prepared in example 4 of the present invention, wherein a) is a scanning electron micrograph; b) is an XRD pattern.

FIG. 5 is a representation of porous lithium aluminum hydrotalcite prepared in example 5 of the present invention, wherein a) is a scanning electron micrograph; b) is an XRD pattern.

For a person skilled in the art, other relevant figures can be obtained from the above figures without inventive effort.

Detailed Description

In order to make the technical solution of the present invention better understood, the technical solution of the present invention is further described below with reference to specific examples.

Example 1

A preparation method of porous lithium-aluminum hydrotalcite,

the method comprises the following steps:

adding anhydrous lithium chloride (13.4g), aluminum chloride hexahydrate (36.2g), sodium dodecyl sulfate (10g) and urea (90g) into 500ml of deionized water, stirring for 60min, fully dissolving to prepare a mixed solution, transferring the mixed solution into a 1000ml four-neck flask, carrying out normal-pressure hydrothermal reaction at 88 ℃ for 24 hours to obtain a precipitate, centrifugally washing the precipitate with the deionized water at 85 ℃, and then drying the precipitate in a forced air drying oven at 70 ℃ for 12 hours to obtain the porous lithium-aluminum hydrotalcite.

Fig. 1 is (a) a scanning electron microscope image and (b) an XRD image of the lithium aluminum hydrotalcite material prepared with sodium dodecyl sulfate as a morphology controlling agent in example 1. From the figure (a), it can be seen that the lithium aluminum hydrotalcite synthesized by the method provided in the present invention has a flower-shaped structure formed by the aggregation of hydrotalcite crystals and forms hierarchical channels.

FIG. 1(b) is an X-ray diffraction pattern of the porous lithium aluminum hydrotalcite material prepared in example 1. From this figure, it can be seen that the characteristic peaks ((002), (004), etc.) of the porous lithium aluminum hydrotalcite material are identical to those of the common hydrotalcite.

Example 2

A preparation method of porous lithium-aluminum hydrotalcite,

the method comprises the following steps:

adding anhydrous lithium chloride (13.4g), aluminum chloride hexahydrate (36g), octadecylamine (6g) and urea (90g) into 500ml of deionized water, stirring for 60min, fully dissolving to prepare a mixed solution, transferring the mixed solution into a 1000ml four-neck flask, carrying out normal-pressure hydrothermal reaction at the reaction temperature of 90 ℃ for 24 hours to obtain a precipitate, carrying out centrifugal washing on the precipitate by using deionized water at the temperature of 85 ℃, and then placing the precipitate in a forced air drying oven to dry for 12 hours at the temperature of 70 ℃ to obtain the porous lithium-aluminum hydrotalcite.

Fig. 2 is (a) a scanning electron microscope image and (b) an XRD image of the lithium aluminum hydrotalcite material prepared with octadecylamine as a morphology controlling agent in example 2. From the figure (a), it can be seen that the lithium aluminum hydrotalcite synthesized by the method provided in the present invention has a flower-shaped structure formed by the aggregation of hydrotalcite crystals and forms hierarchical channels.

FIG. 2(b) is an X-ray diffraction pattern of the porous lithium aluminum hydrotalcite material prepared in example 2. From this figure, it can be seen that the characteristic peaks ((002), (004), etc.) of the porous lithium aluminum hydrotalcite material are identical to those of the common hydrotalcite.

Example 3

A preparation method of porous lithium-aluminum hydrotalcite,

the method comprises the following steps:

adding anhydrous lithium chloride (13.4g), aluminum chloride hexahydrate (36g), sodium dodecyl benzene sulfonate (15g) and urea (90g) into 500ml of deionized water, stirring for 60min, fully dissolving to prepare a mixed solution, transferring the mixed solution into a 1000ml four-neck flask, carrying out normal-pressure hydrothermal reaction at the reaction temperature of 90 ℃ for 24 hours to obtain a precipitate, centrifugally washing the precipitate by using the deionized water at the temperature of 85 ℃, and then drying the precipitate in a forced air drying oven at the temperature of 70 ℃ for 12 hours to obtain the porous lithium-aluminum hydrotalcite.

Fig. 3 is (a) a scanning electron microscope image and (b) an XRD image of the lithium aluminum hydrotalcite material prepared with sodium dodecyl sulfate as a morphology controlling agent in example 3. From the figure (a), it can be seen that the lithium aluminum hydrotalcite synthesized by the method provided in the present invention has a flower-shaped structure formed by the aggregation of hydrotalcite crystals and forms hierarchical channels.

FIG. 3(b) is an X-ray diffraction pattern of the porous lithium aluminum hydrotalcite material prepared in example 3. From this figure, it can be seen that the characteristic peaks ((002), (004), etc.) of the porous lithium aluminum hydrotalcite material are identical to those of the common hydrotalcite.

Example 4

A preparation method of porous lithium-aluminum hydrotalcite,

the method comprises the following steps:

adding anhydrous lithium chloride (13.4g), aluminum chloride hexahydrate (36g), polyacrylamide (0.5g) and urea (90g) into 500ml of deionized water, stirring for 60min, fully dissolving to prepare a mixed solution, transferring the mixed solution into a 1000ml four-neck flask, carrying out normal-pressure hydrothermal reaction at the reaction temperature of 90 ℃ for 24 hours to obtain a precipitate, centrifugally washing the precipitate by using the deionized water at the temperature of 85 ℃, and then drying the precipitate in a forced air drying oven at the temperature of 70 ℃ for 12 hours to obtain the porous lithium-aluminum hydrotalcite.

Fig. 4 is (a) a scanning electron microscope image and (b) an XRD image of the lithium-aluminum hydrotalcite material prepared with polyacrylamide as a morphology controlling agent in example 4. From the figure (a), it can be seen that the lithium aluminum hydrotalcite synthesized by the method provided in the present invention has a flower-shaped structure formed by the aggregation of hydrotalcite crystals and forms hierarchical channels.

FIG. 4(b) is an X-ray diffraction pattern of the porous lithium aluminum hydrotalcite material prepared in example 1. From this figure, it can be seen that the characteristic peaks ((002), (004), etc.) of the porous lithium aluminum hydrotalcite material are identical to those of the common hydrotalcite.

Example 5

A preparation method of porous lithium-aluminum hydrotalcite,

the method comprises the following steps:

adding anhydrous lithium chloride (13.4g), aluminum chloride hexahydrate (36.8g), polyethyleneimine (5g) and urea (90g) into 500ml of deionized water, stirring for 60min, fully dissolving to prepare a mixed solution, transferring the mixed solution into a 1000ml four-neck flask, carrying out normal-pressure hydrothermal reaction at the reaction temperature of 90 ℃ for 24 hours to obtain a precipitate, centrifugally washing the precipitate with the deionized water at the temperature of 85 ℃, and then drying the precipitate in a forced air drying oven at the temperature of 70 ℃ for 12 hours to obtain the porous lithium-aluminum hydrotalcite.

Fig. 5 is (a) a scanning electron microscope image and (b) an XRD image of the lithium-aluminum hydrotalcite material prepared by using polyethyleneimine as a morphology control agent in example 5. From the figure (a), it can be seen that the lithium aluminum hydrotalcite synthesized by the method provided in the present invention has a flower-shaped structure formed by the aggregation of hydrotalcite crystals and forms hierarchical channels.

FIG. 5(b) is an X-ray diffraction pattern of the porous lithium aluminum hydrotalcite material prepared in example 1. From this figure, it can be seen that the characteristic peaks ((002), (004), etc.) of the porous lithium aluminum hydrotalcite material are identical to those of the common hydrotalcite.

TABLE 1 specific surface area and mean pore diameter

Examples of the invention	Specific surface area (m)2/g)	Average pore diameter (nm)
			Example one	11.9	3.8
Example two	33.1	3.8
			Example three	78.5	3.4
Example four	4.4	3.8
			Example five	93.0	31.3

Relational terms such as "first" and "second," and the like, may be used solely to distinguish one element from another element having the same name, without necessarily requiring or implying any actual such relationship or order between such elements.

The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.