CN103159238B - Nano-size layered composite hydroxide and step-by-step precipitation preparation method thereof - Google Patents

Abstract

The invention provides a nanometer-sized layered composite hydroxide and its step-by-step precipitation preparation method. Its preparation uses metal soluble salts and alkalis as raw materials, and the metal ions constituting the LDH laminates are separately precipitated through step-by-step precipitation reactions. , and generate LDH in the second precipitation process. Due to the high activity of the hydroxide prepared by the first step of precipitation reaction, LDH can nucleate and grow rapidly during the second step of precipitation, so that the thickness of the obtained LDH sheet is relatively thin, with a laminate thickness of 5~15nm and a length of 50~ 150nm, and the BET specific surface area is 140-280m ² /g, much larger than the specific surface area of ordinary LDH. The method overcomes the disadvantage of small specific surface area in the preparation of LDH by the co-precipitation method. The preparation method adopted in the present invention is simple, does not require high temperature and high pressure, does not require special equipment, has abundant sources of raw materials, and is low in cost. The layered composite hydroxide can be widely used in the fields of adsorption separation, catalysis, polymer materials and the like.

Description

A kind of nano-sized layered composite hydroxide and its preparation method by step-by-step precipitation

Field

The invention relates to the field of inorganic non-metallic functional materials and their preparation, in particular to a nano-layered composite hydroxide and a preparation method thereof.

Background technique

Layered Double Hydroxides (LDH) is a kind of anionic layered clay, its chemical formula is [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^x+ (A ^n- _x/n ).mH ₂ O, where M ²⁺ and M ³⁺ represent divalent and trivalent metal cations respectively, x represents the change of the content of metal elements, and ^An- represents interlayer anions. LDHs have attracted extensive attention in recent years due to their unique two-dimensional layered structure and the exchangeability of interlayer anions. The unique properties of LDH make it widely used in the fields of catalysis, adsorption, ion exchange and polymer additives (flame retardants, thermal stabilizers and other functional additives).

The specific surface area of a material has an important influence on its application performance, and generally the larger the specific surface area, the better the application performance. LDH usually has a flaky structure with a small specific surface area. Its Brunauer-Emmett-Teller (BET) specific surface area is about 20-80 m ² /g, which greatly limits its application. Traditional preparation methods, such as single drop method, double drop method, nucleation/crystallization isolation method, uniform precipitation method, hydrothermal method, etc., can usually only obtain hexagonal or irregular sheet-shaped LDH microparticles with a thickness of about 20-100 nm. crystal, and there is a serious agglomeration phenomenon, and the BET specific surface area is small. Documents Zhou Jiabin, Yan Siliang, Yu Jiaguo, Shu Zhan, Journal of Hazardous materials, 2011, 192(3), 1114-1121 prepared BET specific surface area of about 64.9m ² /g LDH by uniform precipitation method. Literature Wang Qiang, Wu Zhihuai, Tay Hui Huang, Chen Luwei, Liu Yan Chang Jie, Zhong Ziyi, Luo Jizhong, Borgna Armando, Catalysis Today, 2011, 164(1), 198-203 prepared BET specific surface area by co-precipitation method 114 m ² /g of LDH. Literature Zhao Yun, Li Feng, Zhang Rui, Evans, David G., Duan Xue, Chemistry of Materials, 2002, 14, 4286 prepared LDH with a small particle size and a thickness of about 20 nanometers by using the nucleation/crystallization isolation method , BET specific surface area is about 80m ² /g. Since the thickness of LDH flakes prepared by these methods is usually greater than 20nm, the length is greater than 150nm, and their BET specific surface area is usually less than 120m ² /g, their application properties are greatly limited.

Contents of the invention

The purpose of the present invention is to provide a nano-layered composite hydroxide and its preparation method. The layered composite hydroxide has the characteristics of nano-scale size and large specific surface, and can be used for adsorption and separation, catalysis, and polymer materials. and other fields.

This method uses soluble salts and alkalis that constitute LDH as raw materials to precipitate the soluble salts step by step, and simultaneously generates LDH during the second precipitation reaction process to prepare a product with a thickness of about 5-15nm, a length of about 50-150nm, and a specific surface area. 140-280m ² /g layered composite hydroxide.

The layered composite hydroxide provided by the invention has a general chemical formula:

M ⁺ _x M ²⁺ _1-y-0.5x-2z M ³⁺ _y M ⁴⁺ _z (OH) ₂ (A ^n- ) _y/n mH ₂ O, (1)

Among them, 0≤x≤0.4, 0≤y≤0.7, 0≤z≤0.5, 0≤y+0.5x+2z≤1, y and z cannot be 0 at the same time, m is the number of interlayer crystal water molecules, 0.4≤m ≤1; M ⁺ is a monovalent metal ion Li ⁺ , M ²⁺ is a divalent metal ion Mg ²⁺ , Zn ²⁺ , Ni ²⁺ , Co ²⁺ , Ca ²⁺ , Fe ²⁺ , Mn ²⁺ , Cd Any one or more of ²⁺ , Pd ²⁺ , Pt ²⁺ , Be ²⁺ , Cu ²⁺ , preferably Mg ²⁺ , Zn ²⁺ , Ni ²⁺ , Co ²⁺ , Fe ²⁺ , Cu ² One or more of ⁺ , more preferably one or more of Mg ²⁺ , Zn ²⁺ , Ni ²⁺ , Co ²⁺ ; M ³⁺ is trivalent metal ion Al ³⁺ , Co ³⁺ , Ti ³⁺ , Fe ³⁺ , Cr ³⁺ , Ga ³⁺ , Ni ³⁺ , V ³⁺ , Mn ³⁺ , Rh ³⁺ , Ir ³⁺ , Ru ³⁺ , La ³⁺ , Sc ³⁺ , In Any one or more of ³⁺ , preferably one or more of Al ³⁺ , Co ³⁺ , Fe ³⁺ , Cr ³⁺ , Ni ³⁺ , more preferably Al ³⁺ , Co ³⁺ , One or more of Fe ³⁺ ; M ⁴⁺ is any one of tetravalent metal ions Sn ⁴⁺ , Ti ⁴⁺ , Zr ⁴⁺ ; ^An- is Cl ^- , Br ^- , ClO ₄ ^- , NO ₃ ^- , ClO ₃ ^- , CO ₃ ^2- , SO ₄ ^2- , SO ₃ ^2- , S ₂ O ₃ ^2- , CrO ₄ ^2- and other inorganic anions or oxalate, malonate, terephthalate , dodecylsulfonate and other organic anions, preferably CO ₃ ^2- or NO ₃ ^- .

The thickness of the nano-layered composite hydroxide is about 5-15nm, the length is about 50-150nm, and the specific surface area is 140-280m ² /g, while the average specific surface area of ordinary LDH is about 80m ² /g, which is higher than that of ordinary LDH. The specific surface area is more than 80% larger. It can be used in adsorption separation, catalysis, polymer materials and other fields.

The specific preparation steps of the large specific surface nano LDH provided by the present invention are as follows:

A: Prepare an aqueous solution with a concentration of 0.05-1.5mol/L soluble metal salt. The soluble metal salts are LiCl, MgCl ₂ , ZnCl ₂ , NiCl ₂ , CaCl ₂ , FeCl ₂ , BeCl ₂ , CuCl ₂ , AlCl ₃ , CoCl ₃ , FeCl ₃ , CrCl ₃ , GaCl ₃ , NiCl ₃ , VCl ₃ , LiNO ₃ , Mg(NO ₃ ) ₂ , Zn(NO ₃ ) ₂ , Ni(NO ₃ ) ₂ , Ca(NO ₃ ) ₂ , Fe(NO ₃ ) ₂ , Be(NO ₃ ) ₂ , Cu(NO ₃ ) ₂ , Al(NO ₃ ) ₃ , Co(NO ₃ ) ₃ , Fe(NO ₃ ) ₃ , Cr(NO ₃ ) ₃ , Ga(NO ₃ ) ₃ , Ni(NO ₃ ) ₃ , V(NO ₃ ) _3. Zr(NO ₃ ) ₄ , Li ₂ SO ₄ , MgSO ₄ , ZnSO ₄ , NiSO ₄ , FeSO ₄ , CuSO ₄ , Al ₂ (SO ₄ ) ₃ , Co ₂ (SO ₄ ) ₃ , Ti ₂ (SO ₄ ) ₃ , Fe ₂ (SO ₄ ) ₃ , Cr ₂ (SO ₄ ) ₃ , Ga ₂ (SO ₄ ) ₃ , Ni ₂ (SO ₄ ) ₃ , V ₂ (SO ₄ ) ₃ , Sn(SO ₄ ) ₂ , One of Ti(SO ₄ ) ₂ and Zr(SO ₄ ) ₂ . MgCl ₂ , ZnCl ₂ , NiCl 2 _, CuCl ₂ , AlCl ₃ , CoCl ₃ , FeCl ₃ , Mg(NO ₃ ) ₂ , Zn(NO ₃ ) ₂ , Ni(NO ₃ ) ₂ , Cu(NO ₃ ) ₂ , Al(NO ₃ ) ₃ , Co(NO ₃ ) ₃ , Fe(NO ₃ ) ₃ , MgSO ₄ , ZnSO ₄ , NiSO 4 , FeSO ₄ , CuSO ₄ , Al ₂ ( _{SO 4 ) 3} , Co ₂ ( One of SO ₄ ) ₃ . More preferably MgCl ₂ , NiCl ₂ , AlCl ₃ , CoCl ₃ , FeCl ₃ , Mg(NO ₃ ) ₂ , Ni(NO _{3 ) 2 , Al(NO 3} ) ₃ , Co(NO ₃ ) ₃ , Fe(NO ₃ ) ₃ , Fe(NO 3 ) 2 ₃ ) One of ₃ .

B: Prepare an alkaline solution with a molar concentration of 0.05 to 5 mol/L. The molar amount of the alkali in the alkaline solution is 0.9n to 1.1n times the molar amount of the metal ion added in step A, where n is the valence state of the metal ion. The alkali is one of NaOH, KOH and ammonia water. The alkali solution is mixed with the salt solution prepared in step A to form a hydroxide precipitate, and the precipitate is left to age for 10-60 minutes, referred to as B slurry.

C: According to the target LDH to be prepared, select the soluble salt of the metal required to form the LDH laminate together with the metal ions in step A, add it to the B slurry, dissolve it and mix it evenly to obtain two or more and Conforms to the metal ion mixture that constitutes the LDH laminate, referred to as C slurry, and the ratio of the sum of the molar amounts of monovalent and divalent metal elements to the sum of the molar amounts of trivalent and tetravalent metal elements is 0.5 to 6:1.

The soluble metal salts are LiCl, MgCl ₂ , ZnCl ₂ , NiCl ₂ , CaCl ₂ , FeCl ₂ , BeCl ₂ , CuCl ₂ , AlCl ₃ , CoCl ₃ , TiCl ₃ , FeCl ₃ , CrCl ₃ , GaCl ₃ , NiCl ₃ , VCl ₃ , SnCl ₄ , TiCl ₄ , ZrCl ₄ , LiNO ₃ , Mg(NO ₃ ) ₂ , Zn(NO ₃ ) ₂ , Ni(NO ₃ ) ₂ , Ca(NO ₃ ) ₂ , Fe(NO ₃ ) ₂ , Be(NO ₃ ) ₂ , Cu(NO ₃ ) ₂ , Al(NO ₃ ) ₃ , Co(NO ₃ ) ₃ , Ti(NO ₃ ) ₃ , Fe(NO ₃ ) ₃ , Cr(NO ₃ ) ₃ , Ga(NO ₃ ) ₃ , Ni(NO ₃ ) ₃ , V(NO ₃ ) ₃ , Sn(NO ₃ ) ₄ , Ti(NO ₃ ) ₄ , Zr(NO ₃ ) ₄ , Li ₂ SO ₄ , MgSO ₄ , ZnSO ₄ , NiSO ₄ , FeSO ₄ , CuSO ₄ , Al ₂ (SO ₄ ) ₃ , Co ₂ (SO ₄ ) ₃ , Ti ₂ (SO ₄ ) ₃ , Fe ₂ (SO ₄ ) ₃ , Cr ₂ (SO ₄ ) _3. One of Ga ₂ (SO ₄ ) ₃ , Ni ₂ (SO ₄ ) ₃ , V ₂ (SO ₄ ) ₃ , Sn(SO ₄ ) ₂ , Ti(SO ₄ ) ₂ , Zr(SO ₄ ) ₂ or more. MgCl ₂ , ZnCl ₂ , NiCl ₂ , CuCl ₂ , AlCl ₃ , CoCl ₃ , FeCl ₃ , LiNO ₃ , Mg(NO ₃ ) ₂ , Zn(NO ₃ ) ₂ , Ni(NO ₃ ) ₂ , Cu (NO ₃ ) ₂ , Al(NO ₃ ) ₃ , Co(NO ₃ ) ₃ , Fe(NO ₃ ) ₃ , MgSO ₄ , ZnSO _{4 , NiSO 4} , FeSO ₄ , CuSO _{4 ,} Al ₂ (SO ₄ ) ₃ , One or more of Co ₂ (SO ₄ ) ₃ , Ti(SO ₄ ) ₂ . More preferably MgCl ₂ , NiCl ₂ , AlCl ₃ , CoCl ₃ , FeCl ₃ , Mg(NO ₃ ) ₂ , Ni(NO ₃ ) 2 , Al(NO 3 ) ₃ , Co(NO ₃ ) ₃ , Fe(NO ₃ ) ₃ , Fe(NO 3 ) 2 ₃ ) One or more of ₃ .

D: Prepare an alkaline solution with a molar concentration of 0.05-2.5mol/L, referred to as D solution. The alkaline solution is a mixed solution of alkali and sodium salt Na _n A ^n- , and the molar amount of alkali in the alkaline solution is C slurry 1 to 12 times the molar weight of the added metal ions, and the ratio of A ^n- to the sum of the molar weights of trivalent and tetravalent metal elements in the C slurry is 1 to 6.

Described alkali is one or more in NaOH, KOH, ammoniacal liquor, ammonium carbonate, ammonium bicarbonate, hexamethylenetetramine, urea, is preferably NaOH, ammoniacal liquor, hexamethylenetetramine, urea A ^n- in the sodium salt is Cl ^- , Br ^- , ClO ₄ ^- , NO ₃ ^- , ClO ₃ ^- , CO ₃ ^2- , SO ₄ ^2- , SO ₃ ^2- , S ₂ Any one of inorganic anions such as O ₃ ^2- , CrO ₄ ^2- or organic anions such as oxalate, malonate, terephthalate, and dodecylsulfonate, preferably CO ₃ ^2- or NO ₃ ^- .

E: Under nitrogen protection, 60-110 ° C and stirring conditions, add solution D to C slurry to precipitate the metal salt in C slurry, and react with the hydroxide precipitate prepared in step B to form LDH, and then at 60 Continue to react at ~140°C for 1-24 hours, cool to room temperature, filter, wash and dry the precipitate to obtain LDH with large specific surface.

Wherein the adding speed of D solution is determined according to the pH value of D solution, when its pH value is less than 11, can directly one-time add D solution; The pH value of the slurry is controlled at not more than 10, so as to avoid the strong alkali from dissolving the metal hydroxide in the C slurry too quickly, and the D solution is added dropwise within 4 to 16 hours.

In step E, if the prepared carbonate-type LDH does not need nitrogen protection.

The invention adopts soluble salt and alkali as raw materials, respectively precipitates the metal ions constituting the LDH laminate through the step-by-step precipitation reaction, and generates LDH in the second step precipitation process. Due to the high activity of the hydroxide prepared by the first step of precipitation reaction, LDH can nucleate and grow rapidly during the second step of precipitation, so that the thickness of the LDH sheet is relatively thin and the length is less than 150nm. The method overcomes the disadvantage of small specific surface area in the preparation of LDH by the co-precipitation method.

Accompanying drawing is the X-ray diffractogram, infrared spectrogram and scanning electron microscope figure of the LDH prepared in embodiment 1. The X-ray diffraction pattern shows that the prepared sample has typical characteristic diffraction peaks of LDH; the infrared spectrum shows that the interlayer anion of LDH is carbonate; the scanning electron microscope shows that the prepared LDH has a sheet-like structure, and the thickness of the LDH sheet is about 5 ~ 15nm, the length is about 50-150nm.

The advantages of the present invention are that the preparation method of the present invention is simple and convenient, does not require high temperature and high pressure, does not require special equipment, has abundant sources of raw materials, and is low in cost. In the present invention, the metal ions constituting the LDH laminates are precipitated separately through the step-by-step precipitation method. The thickness of the LDH laminates generated during the reaction process is about 5-15nm, the length is about 50-150nm, and the BET specific surface area is greater than 140m ² /g , can be widely used in adsorption separation, catalysis, polymer materials and other fields.

Description of the drawings:

Fig. 1 is the X-ray diffraction diagram of the layered composite hydroxide prepared in Example 1.

Fig. 2 is the infrared spectrogram of the layered composite hydroxide prepared in Example 1.

3 is a scanning electron micrograph of the layered composite hydroxide prepared in Example 1.

Detailed ways:

The present invention will be further described below in the form of examples, but this does not constitute a limitation to the protection scope of the present invention.

Example 1:

Step A: Weigh 18.75g Al(NO ₃ ) ₃ .9H ₂ O into 100.25g deionized water, and prepare a solution with a concentration of about 0.5mol/L.

Step B: Weigh 6g of NaOH and add it to 75g of deionized water to prepare an alkaline solution, mix the alkaline solution with the Al(NO ₃ ) ₃ solution prepared in step A under stirring conditions to form aluminum hydroxide precipitate, and then leave it to age for 10 minute.

Step C: Weigh 1.92g Mg(NO ₃ ) ₂ .6H ₂ O into 10 g of the aluminum hydroxide precipitation slurry prepared in step B, and mix evenly to completely dissolve Mg(NO ₃ ) ₂ .6H ₂ O.

Step D: Weigh 2.4g of urea and 0.54g of Na ₂ CO ₃ into 40ml of deionized water to prepare an alkaline solution.

Step E: Add the alkali solution prepared in step D directly to the mixture prepared in step C under stirring at 80°C, and then continue to stir and react at 100°C for 24 hours. After the reaction, cool the slurry to room temperature, and the precipitate Wash by centrifugation until the pH value is less than 8, and dry the sample in an oven at 100°C for 12 hours to obtain the LDH product. Elemental analysis shows that the chemical composition formula of the product is: Mg _0.75 Al _0.25 (OH) ₂ (CO ₃ ) _0.125 · 0.68H ₂ O, and BET analysis shows that its specific surface area is 230m ² /g.

Example 2:

Steps A and B are the same as in Example 1.

Step C: Weigh 2.56g Mg(NO ₃ ) ₂ .6H ₂ O into 10 g of the aluminum hydroxide precipitation slurry prepared in step B, and mix evenly to completely dissolve Mg(NO ₃ ) ₂ .6H ₂ O.

Step D: Weigh 3.3g of urea and 0.54g of Na ₂ CO ₃ into 40ml of deionized water to prepare an alkaline solution.

Step E: Add the alkali solution prepared in step D directly to the mixture prepared in step C at 90°C with stirring, then continue to stir and react at 100°C for 20 hours, cool the slurry to room temperature after the reaction, and remove the precipitate Wash by centrifugation until the pH value is less than 8, and dry the sample in an oven at 100°C for 12 hours to obtain the LDH product. Elemental analysis shows that the chemical composition formula of the product is: Mg _0.8 Al _0.2 (OH) ₂ (CO ₃ ) _0.1 ·0.63H ₂ O, and BET analysis shows that its specific surface area is 177m ² /g.

Example 3:

Steps A and B are the same as in Example 1.

Step C: Weigh 0.641g Mg(NO ₃ ) ₂ .6H ₂ O and 0.727g Ni(NO ₃ ) ₂ .6H ₂ O into 10g of the aluminum hydroxide precipitation slurry prepared in step B, mix evenly, and make Mg( NO ₃ ) ₂ .6H ₂ O and Ni(NO ₃ ) ₂ .6H ₂ O were completely dissolved.

Step D: Weigh 1.6g of urea and 0.2g of Na ₂ CO ₃ into 40ml of deionized water to prepare an alkaline solution.

Step E: Add the alkali solution prepared in step D directly to the mixture prepared in step C at 95°C with stirring, then continue to stir and react at 100°C for 10 hours, cool the slurry to room temperature after the reaction, and remove the precipitate Wash by centrifugation until the pH value is less than 8, and dry the sample in an oven at 100°C for 12 hours to obtain the LDH product. Elemental analysis shows that the chemical composition formula of the product is: Mg _0.33 Ni _0.33 Al _0.33 (OH) ₂ (CO ₃ ) _0.165 · 0.63H ₂ O, and BET analysis shows that its specific surface area is 193m ² /g.

Example 4:

Steps A, B, and C are the same as in Example 1.

Step D: Weigh 0.6g NaOH and 0.54g Na ₂ CO ₃ into 40ml deionized water to prepare an alkaline solution.

Step E: Add the alkali solution prepared in step D to the mixture prepared in step C dropwise within 6 hours under stirring at 90°C, then continue the reaction at 100°C for 10 hours, and cool the slurry to At room temperature, the precipitate was centrifuged and washed until the pH value was less than 8, and the sample was dried in an oven at 100°C for 12 hours to obtain the LDH product. Elemental analysis shows that the chemical composition formula of the product is: Mg _0.75 Al _0.25 (OH) ₂ (CO ₃ ) _0.125 · 0.61H ₂ O, and BET analysis shows that its specific surface area is 180.7m ² /g.

Example 5:

Steps A and B are the same as in Example 1.

Step C: Weigh 0.6895g LiNO ₃ and add it to 26.7g of the aluminum hydroxide precipitation slurry prepared in step B, and mix evenly to completely dissolve LiNO ₃ .

Step D: Weigh 0.4g NaOH and 1g NaNO ₃ and add them into 40ml deionized water to prepare an alkaline solution.

Step E: Add the alkali solution prepared in step D to the mixture prepared in step C dropwise within 8 hours under nitrogen atmosphere, 95°C and stirring, then continue to stir and react at 100°C for 10 hours, after the reaction Cool the slurry to room temperature, centrifuge and wash the precipitate until the pH value is less than 8, and dry the sample in an oven at 100°C for 12 hours to obtain the LDH product. Elemental analysis shows that the chemical composition formula of the product is: Li _0.34 Al _0.66 (OH) ₂ (NO ₃ ) _0.34 ·0.55H ₂ O, and BET analysis shows that its specific surface area is 174m ² /g.

Embodiment 6:

Step A: Weigh 25.64g of Mg(NO ₃ ) ₂ .6H ₂ O into 174.36g of deionized water to prepare a solution with a concentration of about 0.5mol/L.

Step B: Weigh 8g of NaOH and add it to 92g of deionized water to prepare an alkali solution, mix the alkali solution with the Mg(NO ₃ ) ₂ solution prepared in step A under stirring conditions to form a magnesium hydroxide precipitate, and then let it stand for aging 20 minutes.

Step C: Weigh 2.01g Ti(SO ₄ ) ₂ ·9H ₂ O into 30g of the magnesium hydroxide precipitation slurry prepared in step B, and mix evenly to completely dissolve Ti(SO ₄ ) ₂ ·9H ₂ O.

Step D: Weigh 3g of urea and 1.06g of Na ₂ CO ₃ into 50ml of deionized water to prepare an alkaline solution.

Step E: Add the alkali solution prepared in step D directly to the mixture prepared in step C at 60°C with stirring, then continue to stir and react at 80°C for 24 hours, cool the slurry to room temperature after the reaction, and remove the precipitate Wash by centrifugation until the pH value is less than 8, and dry the sample in an oven at 100°C for 12 hours to obtain the LDH product. Elemental analysis shows that the chemical composition formula of the product is: Mg _0.66 Ti _0.34 (OH) ₂ (CO ₃ ) _0.34 ·0.68H ₂ O, and BET analysis shows that its specific surface area is 167m ² /g.

Embodiment 7:

Steps A and B are the same as in Example 6.

Step C: Weigh 1.488g Zn(NO ₃ ) ₂ .6H ₂ O and 1.876g Al(NO ₃ ) ₃ .9H ₂ O into 15g of the magnesium hydroxide precipitation slurry prepared in step B, mix evenly, and make Zn( NO ₃ ) ₂ .6H ₂ O and Al(NO ₃ ) ₃ .9H ₂ O were completely dissolved.

Step D: Weigh 4.2g of urea and 0.4g of Na ₂ CO ₃ into 60ml of deionized water to prepare an alkaline solution.

Step E: Add the alkali solution prepared in step D directly to the mixture prepared in step C at 85°C with stirring, then continue to stir and react at 100°C for 12 hours, cool the slurry to room temperature after the reaction, and remove the precipitate Wash by centrifugation until the pH value is less than 8, and dry the sample in an oven at 100°C for 12 hours to obtain the LDH product. Elemental analysis shows that the chemical composition formula of the product is: Mg _0.33 Zn _0.33 Al _0.33 (OH) ₂ (CO ₃ ) _0.165 · 0.66H ₂ O, and BET analysis shows that its specific surface area is 196m ² /g.

Claims (3)

1. prepare a method for nano-scale stratiform complex hydroxide, concrete preparation process is as follows:

A: prepare the aqueous solution that a kind of concentration is 0.05 ~ 1.5mol/L soluble metallic salt;

Described soluble metallic salt is LiCl, MgCl ₂, ZnCl ₂, NiCl ₂, CaCl ₂, FeCl ₂, BeCl ₂, CuCl ₂, AlCl ₃, CoCl ₃, FeCl ₃, CrCl ₃, GaCl ₃, NiCl ₃, VCl ₃, LiNO ₃, Mg (NO ₃) ₂, Zn (NO ₃) ₂, Ni (NO ₃) ₂, Ca (NO ₃) ₂, Fe (NO ₃) ₂, Be (NO ₃) ₂, Cu (NO ₃) ₂, Al (NO ₃) ₃, Co (NO ₃) ₃, Fe (NO ₃) ₃, Cr (NO ₃) ₃, Ga (NO ₃) ₃, Ni (NO ₃) ₃, V (NO ₃) ₃, Zr (NO ₃) ₄, Li ₂sO ₄, MgSO ₄, ZnSO ₄, NiSO ₄, FeSO ₄, CuSO ₄, Al ₂(SO ₄) ₃, Co ₂(SO ₄) ₃, Ti ₂(SO ₄) ₃, Fe ₂(SO ₄) ₃, Cr ₂(SO ₄) ₃, Ga ₂(SO ₄) ₃, Ni ₂(SO ₄) ₃, V ₂(SO ₄) ₃, Sn (SO ₄) ₂, Ti (SO ₄) ₂, Zr (SO ₄) ₂in one;

B: preparation volumetric molar concentration is the basic solution of 0.05 ~ 5mol/L, and in basic solution, the molar weight of alkali is 0.9n ~ 1.1n times of added metal ion molar weight in steps A, n is the valence state of metal ion; The salts solution that this basic solution and steps A are prepared is mixed and generates precipitation of hydroxide, still aging 10 ~ 60min will be precipitated, be called for short B slurries; Described alkali is the one in NaOH, KOH and ammoniacal liquor;

C: according to target LDH to be prepared, choose the soluble salt jointly forming the metal needed for LDH laminate with the metal ion in steps A, join in B slurries, make it dissolve and mix, obtain containing two kinds and above and meet the metal ion mixed solution forming LDH laminate, be called for short C slurries, and the ratio making wherein monovalence, divalent metal element molar weight sum and trivalent, tetravalent metal elements molar weight sum is 0.5 ~ 6:1;

Described soluble metallic salt is LiCl, MgCl ₂, ZnCl ₂, NiCl ₂, CaCl ₂, FeCl ₂, BeCl ₂, CuCl ₂, AlCl ₃, CoCl ₃, TiCl ₃, FeCl ₃, CrCl ₃, GaCl ₃, NiCl ₃, VCl ₃, SnCl ₄, TiCl ₄, ZrCl ₄, LiNO ₃, Mg (NO ₃) ₂, Zn (NO ₃) ₂, Ni (NO ₃) ₂, Ca (NO ₃) ₂, Fe (NO ₃) ₂, Be (NO ₃) ₂, Cu (NO ₃) ₂, Al (NO ₃) ₃, Co (NO ₃) ₃, Ti (NO ₃) ₃, Fe (NO ₃) ₃, Cr (NO ₃) ₃, Ga (NO ₃) ₃, Ni (NO ₃) ₃, V (NO ₃) ₃, Sn (NO ₃) ₄, Ti (NO ₃) ₄, Zr (NO ₃) ₄, Li ₂sO ₄, MgSO ₄, ZnSO ₄, NiSO ₄, FeSO ₄, CuSO ₄, Al ₂(SO ₄) ₃, Co ₂(SO ₄) ₃, Ti ₂(SO ₄) ₃, Fe ₂(SO ₄) ₃, Cr ₂(SO ₄) ₃, Ga ₂(SO ₄) ₃, Ni ₂(SO ₄) ₃, V ₂(SO ₄) ₃, Sn (SO ₄) ₂, Ti (SO ₄) ₂, Zr (SO ₄) ₂in one or more;

D: preparation volumetric molar concentration is the basic solution of 0.05 ~ 2.5mol/L, and be called for short solution D, this basic solution is alkali and sodium salt Na _na ^n-mixing solutions, in basic solution, the molar weight of alkali is 1 ~ 12 times of added metal ion molar weight in C slurries, and A ^n-be 1 ~ 6 with the ratio of trivalent in C slurries and tetravalent metal elements molar weight sum;

Described alkali is one or more in NaOH, KOH, ammoniacal liquor, volatile salt, bicarbonate of ammonia, hexamethylenetetramine, urea; A in described sodium salt ^n-for Cl ^-, Br ^-, ClO ₄ ^-, NO ₃ ^-, ClO ₃ ^-, CO ₃ ^2-, SO ₄ ^2-, SO ₃ ^2-, S ₂o ₃ ^2-, CrO ₄ ^2-any one in inorganic anion or oxalic acid root, malonate, p-phthalic bridge, the organic anion of dodecyl sodium sulfonate root;

E: under nitrogen protection, 60 ~ 110 DEG C and agitation condition, solution D is joined in C slurries, make the metal salt precipitate in C slurries, and react with precipitation of hydroxide prepared by step B and generate LDH, at 60 ~ 140 DEG C, reaction 1 ~ 24 hour is continued after dropwising, be cooled to room temperature, by throw out filtration, washing, drying, obtain large specific surface LDH;

In step e, the speed that adds of solution D is determined according to the pH value of solution D, when its pH value is less than 11, can add directly disposable for solution D; When the pH value of solution D is greater than 11, then the adding speed the pH value of C slurries should be made to control be not more than 10 of solution D, make the too fast dissolving of the metal hydroxides in C slurries to avoid highly basic; General solution D dropwised in 4 ~ 16 hours; If that preparation is carbonate form LDH, without the need to nitrogen protection;

The large specific surface LDH that step e obtains, its chemical general formula is: M ⁺ _xm ²⁺ _1-y-0.5x-2zm ³⁺ _ym ⁴⁺ _z(OH) ₂(A ^n-) _y/nmH ₂o, wherein 0≤x≤0.4,0≤y≤0.7,0≤z≤0.5,0≤y+0.5x+2z≤1, y, z can not be 0, m is simultaneously interlayer crystalline water molecules number, 0.4≤m≤1; M ⁺for monovalent metallic ion Li ⁺, M ²⁺for divalent-metal ion Mg ²⁺, Zn ²⁺, Ni ²⁺, Co ²⁺, Ca ²⁺, Fe ²⁺, Be ²⁺, Cu ²⁺in any one or multiple, M ³⁺for trivalent metal ion Al ³⁺, Co ³⁺, Ti ³⁺, Fe ³⁺, Cr ³⁺, Ga ³⁺, Ni ³⁺, V ³⁺in any one or multiple, M ⁴⁺for quadrivalent metallic ion Sn ⁴⁺, Ti ⁴⁺, Zr ⁴⁺in any one; A ^n-for Cl ^-, Br ^-, ClO ₄ ^-, NO ₃ ^-, ClO ₃ ^-, CO ₃ ^2-, SO ₄ ^2-, SO ₃ ^2-, S ₂o ₃ ^2-, CrO ₄ ^2-any one in inorganic anion or oxalic acid root, malonate, p-phthalic bridge, the organic anion of dodecyl sodium sulfonate root; This LDH laminate thickness is 5 ~ 15nm, length is 50 ~ 150nm, and specific surface area is 140 ~ 280m ²/ g.

2. the preparation method of nano-scale stratiform complex hydroxide according to claim 1, is characterized in that:

Soluble metallic salt described in steps A is MgCl ₂, ZnCl ₂, NiCl ₂, CuCl ₂, AlCl ₃, CoCl ₃, FeCl ₃, Mg (NO ₃) ₂, Zn (NO ₃) ₂, Ni (NO ₃) ₂, Cu (NO ₃) ₂, Al (NO ₃) ₃, Co (NO ₃) ₃, Fe (NO ₃) ₃, MgSO ₄, ZnSO ₄, NiSO ₄, FeSO ₄, CuSO ₄, Al ₂(SO ₄) ₃, Co ₂(SO ₄) ₃in one;

Soluble metallic salt described in step C is MgCl ₂, ZnCl ₂, NiCl ₂, CuCl ₂, AlCl ₃, CoCl ₃, FeCl ₃, LiNO ₃, Mg (NO ₃) ₂, Zn (NO ₃) ₂, Ni (NO ₃) ₂, Cu (NO ₃) ₂, Al (NO ₃) ₃, Co (NO ₃) ₃, Fe (NO ₃) ₃, MgSO ₄, ZnSO ₄, NiSO ₄, FeSO ₄, CuSO ₄, Al ₂(SO ₄) ₃, Co ₂(SO ₄) ₃, Ti (SO ₄) ₂in one or more;

Alkali described in step D is the one in NaOH, ammoniacal liquor, hexamethylenetetramine, urea, described A ^n-for CO ₃ ^2-or NO ₃ ^-.

3. the preparation method of nano-scale stratiform complex hydroxide according to claim 1, is characterized in that:

Soluble metallic salt described in steps A is MgCl ₂, NiCl ₂, AlCl ₃, CoCl ₃, FeCl ₃, Mg (NO ₃) ₂, Ni (NO ₃) ₂, Al (NO ₃) ₃, Co (NO ₃) ₃, Fe (NO ₃) ₃in one;

Soluble metallic salt described in step C is for being MgCl ₂, NiCl ₂, AlCl ₃, CoCl ₃, FeCl ₃, Mg (NO ₃) ₂, Ni (NO ₃) ₂, Al (NO ₃) ₃, Co (NO ₃) ₃, Fe (NO ₃) ₃in one or more.