CN104030330B - Method for preparing high-purity aluminum hydroxide through induced crystallization - Google Patents

Abstract

The invention belongs to the field of high-purity alumina materials and provides a method for inducing crystallization to prepare high-purity aluminum hydroxide. The method adopts the aluminum-containing double salt generated by the reaction of high-purity aluminum, electronic-grade organic base and high-purity water. By adding seeds to induce crystallization, the aluminum-containing double salt is decomposed to obtain aluminum hydroxide and organic base, and the obtained aluminum hydroxide is filtered. Washing and drying produce high-purity aluminum hydroxide crystals with high purity and consistent crystal form, and the organic base can be recycled. The method has the advantages of short process flow, easy-to-obtain raw materials, high product quality, low cost and no pollution. The purity of the obtained aluminum hydroxide powder is more than or equal to 99.999%, and the contents of impurities such as Fe, Si and Na are all less than 3ppmw. The product high-purity aluminum hydroxide is especially suitable for high-purity alumina, LED sapphire, luminescent materials and other fields.

Description

A method for preparing high-purity aluminum hydroxide by induced crystallization

technical field

The invention belongs to the field of chemical product preparation, and in particular relates to a method for preparing high-purity aluminum hydroxide with consistent crystal forms through induced crystallization technology. More specifically, the present invention relates to a method that uses high-purity aluminum foil to react with electronic-grade organic bases and high-purity water to generate aluminum-containing double salts. Through seed crystal-induced crystallization, the aluminum-containing double salts decompose to generate aluminum hydroxide crystals and organic bases, which will be obtained The aluminum hydroxide is filtered, washed, and dried to prepare high-purity aluminum hydroxide crystals with consistent crystal forms, which is a method for recycling organic bases.

Background technique

Crystallization is a kind of crystallization from liquid (solution or melt) or gaseous raw materials, which belongs to the unit operation of heat and mass transfer process. Macroscopically, the crystallization process is a complex phase transition process from gas, liquid or solid phase to solid phase. Microscopically, it is a process of arranging many atoms, ions, molecules or molecular groups into a regular three-dimensional periodic array. A result of mass transfer between complex multiphase systems. According to the characteristics of liquid-solid equilibrium, the crystallization operation can not only obtain solid solutes from solutions, but also separate high-purity or ultra-pure crystals from solutions with considerable impurities or multi-component mixtures. Crystal morphology, size and purity not only play an important role in crystal growth, but also determine the application of the product crystal. But crystal growth is a complex process that is easily affected by many factors. In order to obtain specific crystals, artificial factors can be used to control the growth process of crystals, that is, induced crystallization. Induced crystallization is a general term for strengthening and controlling the crystallization process by analyzing the crystallization mechanism, controlling the factors affecting the crystallization process, forming a specific physical and chemical environment, and regulating the two important steps of nucleation and crystal growth. Induced crystallization technology is mainly used for material purification and functionalization and has become one of the main development directions.

High-purity aluminum hydroxide has a wide range of applications. Aluminum hydroxide has the functions of flame retardancy, smoke elimination and filling, and can be used as a flame retardant. High-purity aluminum hydroxide can be used to prepare high-purity alumina, and then to prepare sapphire and so on. The purity and crystal form of aluminum hydroxide crystals play a decisive role in its application fields.

At present, the main process for preparing high-purity aluminum hydroxide is alkoxide hydrolysis, including active aluminum alkoxide method and choline method.

(1) The aluminum alcohol method is a Japanese Sumitomo patented technology, which is carried out in two steps. First, aluminum and isopropanol and other organic alcohols are reacted to form aluminum alcohol salts, which become high-purity aluminum alcohol salts after rectification to remove excess organic alcohols. Finally, it is hydrolyzed to obtain aluminum hydroxide. Its disadvantages are: the process route is long, the reaction of alcohol and aluminum must be carried out under anhydrous conditions, and the reaction of aluminum and alcohol will be greatly inhibited in the presence of water. In addition, processes such as rectification and recovery of organic alcohol and membrane filtration of impurities are required, and the investment in equipment is large.

(2) The choline method is that aluminum and choline react to generate a double salt. Under supersaturated conditions, the choline double salt of aluminum is hydrolyzed to generate aluminum hydroxide and emit hydrogen. Both Chinese patent CN02108991.4 and Chinese patent 200510028367.5 disclose this method. However, high-purity choline needs to be separated and refined by choline chloride ion exchange, and the purity of choline is difficult to guarantee. Therefore, the acquisition of high-purity choline determines the product quality and cost.

Contents of the invention

The object of the present invention is to aim at the above-mentioned deficiencies existing in the existing high-purity aluminum hydroxide production process, and to provide a method for preparing high-purity aluminum hydroxide by induced crystallization, which can produce high-purity aluminum hydroxide with consistent crystal form, It can also shorten the technological process, reduce costs, and be environmentally friendly.

A new method for preparing high-purity aluminum hydroxide by induced crystallization proposed by the present invention is realized through the following technical solutions:

A method of inducing crystallization to prepare high-purity aluminum hydroxide, which uses high-purity aluminum foil to react with electronic-grade organic bases and high-purity water to generate aluminum-containing double salts, and induces crystallization through seed crystals to decompose aluminum-containing double salts to generate aluminum hydroxide crystals and organic bases. The obtained aluminum hydroxide is filtered, washed, and dried to prepare high-purity aluminum hydroxide crystals with consistent crystal forms, and the organic base is recycled, including the following steps:

(1) Add high-purity aluminum foil to the mixed solution of electronic-grade organic base and high-purity water, so that the concentration of organic base after mixing is 0.1mol/L～3mol/L, and stir to react;

(2) adding high-purity aluminum hydroxide seed crystals into (1) mixed reaction system in stages;

(3) performing solid-liquid separation on the heterogeneous system that has been reacted in (2), to obtain solid powder and a mixed solution;

(4) washing the solid powder obtained in (3) with high-purity water, and then drying the solid.

According to the method for preparing high-purity aluminum hydroxide by induced crystallization, the purity of the high-purity aluminum foil is above 99.999%, and the thickness of the aluminum foil is less than or equal to 40 μm.

According to the method for preparing high-purity aluminum hydroxide by induced crystallization, the electronic-grade organic base is one or a mixture of tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide.

According to the method for preparing high-purity aluminum hydroxide by induced crystallization, the amount of high-purity aluminum hydroxide seed crystals added is 10% to 100% of the weight of the product aluminum hydroxide.

According to the method for preparing high-purity aluminum hydroxide by induced crystallization, the temperature of the reaction system in step (2) is 50-95° C., and the reaction time is 1-8 hours.

According to the method for preparing high-purity aluminum hydroxide by induced crystallization, the concentration of the electronic-grade organic base is 0.1 mol/L-3 mol/L, which is recycled.

According to the method for preparing high-purity aluminum hydroxide by inducing crystallization, the aluminum hydroxide filtration is centrifugal separation or vacuum filtration.

According to the method for preparing high-purity aluminum hydroxide by induced crystallization, the drying temperature of aluminum hydroxide is 100-250°C.

According to the method for preparing high-purity aluminum hydroxide by inducing crystallization, the resistivity of high-purity water is ≥15MΩ·cm.

The present invention aims at the deficiencies of the prior art, by reacting high-purity aluminum foil with electronic-grade organic base and high-purity water to generate aluminum-containing double salt, and through crystal seed-induced crystallization, the aluminum-containing double salt decomposes to generate aluminum hydroxide crystals and organic base. The obtained aluminum hydroxide is filtered, washed, and dried to prepare high-purity aluminum hydroxide crystals with consistent crystal forms.

The basic principle of the new method of the present invention is as follows:

Hydrolysis reaction: Al+ROH+3H ₂ O→R[Al(OH) ₄ ]+1.5H ₂

Induced crystallization:

The technological process characteristics of new method of the present invention are as follows:

1. Short process: Compared with the aluminum alcohol method, this process directly reacts high-purity aluminum and water, and the mother liquor is recycled, which greatly shortens the process flow, and the mother liquor does not need to be purified by distillation.

2. Raw materials are easy to obtain: Compared with the choline method, the high-purity special-effect organic base used in this project is easy to obtain and can be easily purchased in the market, and its purity is high. All metal ions are less than 10ppb, which ensures product quality.

3. Low cost: This process realizes the direct reaction of aluminum and water to produce high-purity aluminum hydroxide. The operating conditions of the equipment are mild. Due to the recycling of the catalyst, the consumption is very small, so the overall cost is lower than that of the aluminum alcohol method and the choline method.

4. Pollution-free: The main raw materials in the process are water and aluminum, and the products are aluminum hydroxide and hydrogen, and a large amount of hydrogen produced can be recycled. There is no waste residue, waste water, or exhaust gas discharge.

Compared with the prior art, the induced crystallization process for preparing high-purity aluminum hydroxide provided by the present invention has the following advantages:

(1) By inducing crystallization, the product has high purity (99.999%), and the contents of Fe, Si, Na and other elements are all less than 3ppm. Moreover, the crystal forms are all alpha aluminum hydroxide.

(2) The cost is low, the requirements for the production process are low, and the operating conditions are mild.

(3) The organic base can be recycled, the consumption is very little, and the production cost is low.

(4) Short process: Compared with the aluminum alcohol method, this process directly reacts aluminum and water, and the mother liquor is recycled, which greatly shortens the process flow, and the mother liquor does not need to be purified by rectification.

(5) Pollution-free: the main raw materials in the process are water and aluminum, and the products are aluminum hydroxide and hydrogen, and a large amount of hydrogen produced can be recycled. There is no waste residue, waste water, or exhaust gas discharge.

Description of drawings

Fig. 1 is a process flow diagram of the present invention;

Fig. 2 is the SEM photograph of aluminum hydroxide seed crystal;

Fig. 3 is the XRD phase analysis of aluminum hydroxide crystal seed;

Fig. 4 is the SEM photo of induced crystallization product;

Figure 5 is the XRD phase analysis of the induced crystallization product.

detailed description

The outstanding advantages and innovations of the present invention will be further described through the embodiments of the present invention below in conjunction with the accompanying drawings, but the present invention is not limited thereto.

Example 1

Take 300mL of organic base in a polytetrafluoroethylene reactor with a concentration of 3mol/L, set the stirrer speed at 240rpm, and the reaction temperature at 70°C, add 5g of aluminum foil for hydrolysis reaction, and add gibbsite seed crystals at the same time Inducing crystallization, the amount of seed crystals added was 1.45 g, and the reaction crystallization time was 1 hour. Use a high-speed centrifuge to separate the generated Al(OH) ₃ from the reaction reagents, wash the solid powder with high-purity water until the washing liquid is neutral, and put it in a drying oven at 100°C for drying. The product aluminum hydroxide has a mass of 14.4g and a crystal form of α-Al(OH) ₃ . The results of its impurity content are shown in Table 1.

Table 1 Induced crystallization product purity analysis

Impurities Fe Si Na Mg Ni Ti Zn Cu C ppm 2 2 1 0.2 0.1 0.1 0.2 ----- -----

Example 2

Take 10mL of organic base (3mol/L) and 290mL of high-purity water in a polytetrafluoroethylene reactor, the stirring speed is 240rpm, the reaction temperature is 95°C, add 5g of aluminum foil for hydrolysis reaction, and at the same time add gibbsite seed crystals to induce crystallization , the seed crystal addition amount is 14.4g, and the reaction crystallization time is 8 hours. After the reaction, use a vacuum pump to perform suction filtration, and wash the crystals with high-purity water until the washing liquid is neutral, and then place them in a drying oven at 250° C. for drying. The product aluminum hydroxide has a mass of 15.0g and a crystal form of α-Al(OH) ₃ . The results of its impurity content are shown in Table 2.

Table 2 Induced crystallization product purity analysis

crystal form Impurities Fe Si Na Mg Ni Ti Zn Cu C OtherOther α-Al(OH) ₃ ppm 1 1 0.5 0.1 0.1 0.1 0.1 ----- ----- 1

Example 3

Take 100mL of organic base (3mol/L) and 200mL of high-purity water in a polytetrafluoroethylene reactor, the stirring speed is 240rpm, the reaction temperature is 90°C, add 5g of aluminum foil for hydrolysis reaction, and at the same time add gibbsite seed crystals to induce crystallization , the seed crystal addition amount is 14.4g, and the reaction crystallization time is 4 hours. After the reaction, use a vacuum pump to perform suction filtration, and wash the crystals with high-purity water until the washing liquid is neutral, and then place them in a drying oven at 250° C. for drying. The product aluminum hydroxide has a mass of 14.5g and a crystal form of α-Al(OH) ₃ . The results of its impurity content are shown in Table 3.

Table 3 Induced crystallization product purity analysis

crystal form Impurities Fe Si Na Mg Ni Ti Zn Cu C OtherOther α-Al(OH) ₃ ppm 2 2 1 0.5 0.1 0.1 0.2 ----- ----- 1

Example 4

Take 50mL of organic base (3mol/L) and 200mL of high-purity water in a polytetrafluoroethylene reactor, the stirring speed is 240rpm, the reaction temperature is 80°C, add 5g of aluminum foil for hydrolysis reaction, and at the same time add gibbsite seed crystals to induce crystallization , the seed crystal addition amount is 7.222g, and the reaction crystallization time is 3 hours. After the reaction, use a vacuum pump to perform suction filtration, and wash the crystals with high-purity water until the washing liquid is neutral, and then place them in a drying oven at 250° C. for drying. The product aluminum hydroxide has a mass of 14.8g and a crystal form of α-Al(OH) ₃ . The results of its impurity content are shown in Table 4.

Table 4 Induced crystallization product purity analysis

crystal form Impurities Fe Si Na Mg Ni Ti Zn Cu C OtherOther α-Al(OH) ₃ ppm 1.5 2 1 0.5 0.1 0.1 0.2 ----- ----- 1

Example 5

Take 50mL of organic base (3mol/L) and 200mL of high-purity water in a polytetrafluoroethylene reactor, the stirring speed is 240rpm, the reaction temperature is 50°C, add 5g of aluminum foil for hydrolysis reaction, and at the same time add gibbsite seed crystals to induce crystallization , the seed crystal addition amount is 7.2g, and the reaction crystallization time is 5 hours. After the reaction, use a vacuum pump to perform suction filtration, and wash the crystals with high-purity water until the washing liquid is neutral, and then place them in a drying oven at 250° C. for drying. The product aluminum hydroxide has a mass of 14.8g and a crystal form of α-Al(OH) ₃ . The results of its impurity content are shown in Table 5.

Table 5 Induced crystallization product purity analysis

crystal form Impurities Fe Si Na Mg Ni Ti Zn Cu C OtherOther α-Al(OH) ₃ ppm 1 2 1 0.5 0.1 0.1 0.2 ----- ----- 1

Claims (2)

1. A method for preparing high-purity aluminum hydroxide by induced crystallization, characterized in that: Use high-purity aluminum foil to react with electronic-grade organic base and high-purity water to form aluminum-containing double salt. Through seed crystal-induced crystallization, aluminum-containing double salt decomposes to form aluminum hydroxide crystals and organic base. The obtained aluminum hydroxide is filtered and washed. Drying and preparing high-purity aluminum hydroxide crystals with consistent crystal forms, and recycling of organic bases, includes the following steps: (1) Add high-purity aluminum foil to the mixed solution of electronic-grade organic base and high-purity water, so that the concentration of organic base after mixing is 0.1mol/L-3mol/L, and stir to react; the purity of the high-purity aluminum foil is 99.999% Above, the thickness of the aluminum foil is ≤40 μm; the electronic-grade organic base is one or a mixture of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and the electronic-grade organic base The concentration is 0.1mol/L～3mol/L, and it can be recycled; (2) Add high-purity aluminum hydroxide seed crystals into (1) mixed reaction system in stages, the amount of high-purity aluminum hydroxide seed crystals added is 10% to 100% of the weight of the newly crystallized aluminum hydroxide product, and the temperature of the reaction system is 50～95℃, the reaction time is 1～8 hours; (3) Separating the multiphase system after the reaction in (2) into solid and liquid, and centrifuging or vacuum filtering to obtain solid powder and mixed solution; (4) Wash the solid powder obtained in (3) with high-purity water, and then dry the solid at a temperature of 100-250°C; The resistivity of the high-purity water is ≥15MΩ·cm. 2. a kind of induced crystallization as claimed in claim 1 prepares the method for high-purity aluminum hydroxide, it is characterized in that getting the organic base of 300mL in polytetrafluoroethylene reactor, concentration is 3mol/L, and agitator rotating speed is set to be 240rpm , the reaction temperature is 70°C, add 5g aluminum foil for hydrolysis reaction, and add high-purity aluminum hydroxide seed crystals to induce crystallization at the same time, the amount of seed crystals added is 1.45g, the reaction crystallization time is 1 hour, and the generated Al(OH) ₃ Separate from the reaction reagent, wash the solid powder with high-purity water until the washing liquid is neutral, put it in a drying oven at 100°C for drying, the product aluminum hydroxide has a mass of 14.4g, and the crystal form is α-Al(OH) ₃ , the impurity content results are shown in Table 1: Table 1 Purity analysis of induced crystallization products Impurities Fe Si Na Mg Ni Ti Zn Cu C other ppm 2 2 1 0.2 0.1 0.1 0.2 blank blank 1 .