JP2005047785A - Method for producing high purity aluminum fluoride - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing high purity aluminum fluoride which has no problems such as yield down, equipment corrosion and the like and by which high purity aluminum fluoride can be produced with an industrial advantage. <P>SOLUTION: Hydrofuluoric acid is reacted with aluminum hydroxide by adding and dissolving aluminum hydroxide in a hydrofuluoric acid solution. Aluminum fluoride is produced by depositing aluminum fluoride as a hydrate from the obtained reaction solution. The pure reaction equivalent ratio based on pure hydrofuluoric acid which is denoted as Al(OH)<SB>3</SB>/6HF and which omits impurity acids except hydrofuluoric acid from total acids reacted with aluminum hydroxide in raw material hydrofuluoric acid is calculated. The value of the pure reaction equivalent ratio at a reaction system between hydrofuluoric acid and aluminum fluoride is controlled to be in the range: 0.90<Al(OH)<SB>3</SB>/6HF<1.05. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing aluminum fluoride of high purity industrially advantageously by reacting aluminum hydroxide with hydrofluoric acid and using a wet method.

  Aluminum fluoride is an inorganic solid substance whose anhydride is widely used in many fields as a flux for aluminum electrolytic refining, coating for welding rods, ceramics and other chemicals, organic fluoride synthesis catalyst, etc. As the production method, a dry production method in which hydrogen fluoride gas and aluminum hydroxide are reacted (see JP-A-11-335,118), and hydrofluoric acid and aluminum hydroxide are reacted to form a supersaturated solution of aluminum fluoride. And a wet process for depositing aluminum fluoride from this solution (see Japanese Patent Publication Nos. 02-62,492, JP 07-2517, and JP 11-92,137). This has the advantage that a product having a relatively high purity can be obtained compared to the dry process.

However, in recent years, new applications such as refractories that require strict control of the casting speed, for example, have been developed, have a relatively large specific surface area, a low content of unreacted aluminum oxide, and higher purity. There is a demand for aluminum fluoride, and there are cases where it is not possible to cope with it by a wet process, and in order to produce high purity aluminum fluoride by this wet process, a reaction equivalent ratio [Al (OH) ₃ / If [6HF] is lowered, the amount of aluminum that reacts with fluorine decreases and the yield decreases (yield decrease), and the corrosion problem (equipment corrosion) occurs in the metal part of the manufacturing facility.

Japanese Patent Laid-Open No. 11-335,118 Japanese Patent Publication No. 02-62,492 Japanese Patent Application Laid-Open No. 07-2,517 Japanese Patent Laid-Open No. 11-92,137

Therefore, the present inventor has found that there is no problem such as a decrease in yield and equipment corrosion, and as a result of earnestly examining a method for industrially producing high-purity aluminum fluoride, hydrofluoric acid and water. The reaction equivalent ratio when reacting with aluminum oxide is not based on the total acid content that reacts with aluminum hydroxide in the raw material hydrofluoric acid so far, but impurities other than hydrofluoric acid are excluded from this total acid content. Based on the pure hydrofluoric acid content (pure HF acid content), the pure reaction equivalent ratio [Al (OH) ₃ / 6HF] calculated based on this pure HF acid content is 0.90 <Al (OH) It has been found that this object can be achieved by controlling within the range of _{3 /} 6HF <1.05, and the present invention has been completed.

  Therefore, an object of the present invention is to provide a method for producing high-purity aluminum fluoride that is free from problems such as yield reduction and equipment corrosion, and that can produce high-purity aluminum fluoride industrially advantageously. There is.

That is, in the present invention, aluminum hydroxide is added and dissolved in a hydrofluoric acid aqueous solution to react hydrofluoric acid and aluminum hydroxide, and aluminum fluoride is converted into a hydrate from the obtained reaction solution. Pure hydrofluoric acid content (pure HF acid content), which is a method for producing aluminum fluoride to be deposited, and excluding impurity acids other than hydrofluoric acid from the total acid content of raw material hydrofluoric acid that reacts with aluminum hydroxide The pure reaction equivalent ratio [Al (OH) ₃ / 6HF] based on this pure HF acid content was calculated, and the pure reaction equivalent ratio of the reaction system of hydrofluoric acid and aluminum hydroxide was 0.90 <Al This is a method for producing high-purity aluminum fluoride, which is controlled within the range of (OH) ₃ /6HF<1.05.

  In the present invention, the hydrofluoric acid used as a raw material is not particularly limited, and the hydrofluoric acid concentration (HF concentration) is 50 similarly to the hydrofluoric acid conventionally used in this type of wet manufacturing method. ˜350 g / L, preferably 150 to 250 g / L, more preferably 180 to 200 g / L, which are inevitably mixed during the production of hydrofluoric acid and react with aluminum hydroxide. Impurity acids other than hydrofluoric acid (silicic acid, sulfuric acid, and phosphoric acid) are allowed to be about 2% by weight, preferably about 1% by weight, based on the total acid content that reacts with aluminum hydroxide.

  In addition, the aluminum hydroxide used as one of the raw materials should have a purity of 90% by weight or more, preferably 98% by weight or more, and more preferably 99% by weight or more. When the purity of aluminum hydroxide used as a raw material is lower than 90% by weight, impurities derived from aluminum hydroxide increase, making it difficult to produce intended high-purity aluminum fluoride.

In the present invention, when hydrogen hydroxide is added and dissolved in a hydrofluoric acid aqueous solution to react hydrofluoric acid with aluminum hydroxide, pure hydrogen fluoride in hydrofluoric acid used as a raw material is used. Pure reaction equivalent ratio [Al (OH) ₃ / 6HF] based on acid content (pure HF acid content) is 0.90 <Al (OH) ₃ /6HF<1.05, preferably 0.91 ≦ Al (OH) _It is necessary to control within the range of _{3 /} 6HF ≦ 1.04.

  Here, the pure hydrofluoric acid content (pure HF acid content) is the total acid content that reacts with aluminum hydroxide in the raw hydrofluoric acid to the impurity acid content other than hydrofluoric acid, that is, hydrofluoric acid. Is a pure hydrofluoric acid content (pure HF acid content) excluding an acid content mainly composed of silicofluoric acid, sulfuric acid and phosphoric acid, which is inevitably mixed during the production of the resin, and is generally determined as follows. .

That is, first, potassium nitrate is added to a sample of raw hydrofluoric acid so as to be supersaturated to completely precipitate silicic acid and purify nitric acid equivalent to the silicic acid. Next, titration with an aqueous sodium hydroxide solution quantifies all the acid content (HF, H ₂ SO ₄ , H ₃ PO ₄ , HNO ₃ (H ₂ SiF ₆ )) present in the sample, Minute (T.HF; g / L).
Next, the sample is completely dissolved potassium silicofluoride acid heated are precipitated, titrated with sodium hydroxide solution, to calculate the SiO ₂ from spent sodium hydroxide, which SiO ₂ minutes (SiO ₂ ; g / L). Here, the reason why the silicon hydrofluoric acid content (H ₂ SiF ₆ ) is displayed as SiO ₂ content is to facilitate calculation of the reaction equivalent ratio of hydrofluoric acid that reacts with aluminum hydroxide.

Next, the sample is heated to vaporize and remove hydrofluoric acid and silicic acid, and on the other hand, titrate with an aqueous sodium hydroxide solution to determine the total amount of sulfuric acid and phosphoric acid. (TH ₂ SO ₄ ; g / L). On the other hand, phosphoric acid is quantified by the molybdenum blue method, and the sulfuric acid and phosphoric acid are quantified.

The pure HF acid content (HF) used in determining the pure reaction equivalent ratio [Al (OH) ₃ / 6HF] of hydrofluoric acid and aluminum hydroxide is the following reaction formula: Main reaction 3HF + Al (OH ₃ ) → AlF ₃ + 3H ₂ O
Side reaction (a) 3H ₂ SO ₄ + 2Al (OH) ₃ → Al ₂ (SO ₄ ) ₃ + 6H ₂ O
(b) H ₃ PO ₄ + Al (OH) ₃ → AlPO ₄ + 3H ₂ O
(c) H ₂ SiF ₆ + 2Al (OH) ₃ → 2AlF ₃ + SiO ₂ + 4H ₂ O
Based on the above, the equivalent of the SiO ₂ minute and sulfuric acid / phosphoric acid content (TH ₂ SO ₄ ) reacting with sodium hydroxide is converted to HF, the HF conversion factor of SiO ₂ is 2, and the sulfuric acid / phosphoric acid content is It is set to 0.408 and is calculated from the following calculation formula.
Pure HF acid content (HF) =
Total acid content (T.HF)-{SiO ₂ min (SiO ₂ ) x 2 + sulfuric acid / phosphoric acid content (TH ₂ SO ₄ ) x 0.408}
Here, since the molecular weight of phosphoric acid is the same as that of sulfuric acid and the side reaction of phosphoric acid is smaller than other side reactions, phosphoric acid is treated as a part of sulfuric acid.

Next, based on the pure HF acid content (HF) of the raw material hydrofluoric acid thus obtained, the pure reaction equivalent ratio [Al (OH) ₃ with aluminum hydroxide to be reacted with this raw material hydrofluoric acid. / 6HF] is determined within the range of 0.90 <Al (OH) ₃ /6HF<1.05, preferably, when the concentration of the impurity acid contained in the raw hydrofluoric acid is high at this time It is preferable to make correction so that the impurity acid content is low and the impurity acid content is high when the concentration is low. By performing this correction, there is an advantage that both quality and manufacturing cost can be optimized.

Specifically, the correction of the reaction equivalent ratio [Al (OH) ₃ / 6HF] in the reaction system described above is based on the silicic acid content (H ₂ SiF ₆ minutes) in the impurity acid content in the raw hydrofluoric acid. Compared to the total sulfuric acid and phosphoric acid content (TH ₂ SO ₄ min) of sulfuric acid and phosphoric acid, silicic acid (H ₂ SiF ₆ min) with higher impurity concentration or sulfuric acid and phosphoric acid content (TH ₂ SO ₄ min) In the case of silicic acid content (H ₂ SiF ₆ minutes), the following correction formula (1), and in the case of sulfuric acid / phosphoric acid content (TH ₂ SO ₄ minutes), the following correction formula (2) Is done.
y = 1.05-0.0075x (1)
y = 1.05-0.0060x (2)
[However, in the correction equations (1) and (2), y represents the pure reaction equivalent ratio [Al (OH) ₃ / 6HF] in the reaction system, and x represents the content of silicofluoric acid in the raw hydrofluoric acid ( H ₂ SiF ₆ minutes) or sulfuric acid / phosphoric acid content (TH ₂ SO ₄ minutes) concentration (g / L in terms of HF 200 g / L). ]
These correction equations (1) and (2) are both obtained experimentally, and by correcting based on these correction equations (1) and (2), higher-purity aluminum fluoride Can be manufactured.

In the present invention, the peak temperature of the reaction system after dissolution of aluminum hydroxide is controlled in the range of 100 ± 2 ° C., preferably in the range of 101 ± 1 ° C. The peak temperature of this reaction system is preferably controlled in the range of 170 to 200 g / L of hydrofluoric acid concentration (HF concentration) in the reaction system, depending on the liquid temperature of the hydrofluoric acid aqueous solution before dissolution of aluminum hydroxide. The temperature of the reaction system due to the reaction heat generated by the reaction between hydrofluoric acid and aluminum hydroxide should be taken into account in consideration of the temperature of the hydrofluoric acid aqueous solution before dissolution of aluminum hydroxide. Thus, the hydrofluoric acid concentration (HF concentration) of the reaction system is determined. By controlling the peak temperature of the reaction system within a range of 100 ± 2 ° C., it is possible to prevent hydrogen fluoride from evaporating from the reaction system and change the pure reaction equivalent ratio [Al (OH) ₃ / 6HF]. It is possible to prevent a decrease in the purity of the produced aluminum fluoride.

  Furthermore, in the present invention, the addition of aluminum hydroxide to the hydrofluoric acid aqueous solution is preferably performed within 50 minutes, more preferably within 30 minutes, before the reaction system reaches the peak temperature. When the addition time of the aluminum hydroxide exceeds 50 minutes, the precipitation rate of the produced aluminum fluoride is increased, the precipitation time is shortened, and the generation of fine particles increases.

  In the present invention, if the stirring of the reaction system is continued after the addition of aluminum hydroxide to the hydrofluoric acid aqueous solution, the liquid temperature of the reaction system gradually rises to the boiling point or near the boiling point, and reaches the peak temperature. . Thereafter, when stirring is further continued, aluminum fluoride produced in the reaction system and dissolved in the reaction solution gradually becomes a hydrate and precipitates from the reaction solution. In this reaction, the time between peak temperatures from the peak temperature in the exothermic reaction after the addition of aluminum hydroxide to the hydrofluoric acid aqueous solution to the peak temperature in the precipitation reaction in which the produced aluminum fluoride hydrate precipitates is Usually, 2 to 5 hours, preferably 3 to 4 hours. When the time between the peak temperatures is shorter than 2 hours, the generation of fine particles increases and the yield decreases. On the other hand, when the time between the peak temperatures is longer than 5 hours, corrosion of the apparatus starts to become a problem.

The reaction solution (slurry) obtained by reacting hydrofluoric acid and aluminum hydroxide in this manner and precipitating aluminum fluoride hydrate from the reaction system is then filtered, centrifuged, etc. After removing the adhering water by the above means, it can be dried and calcined according to a conventional method to obtain anhydrous aluminum fluoride.
Here, about the reaction liquid temperature at the time of making the reaction liquid (slurry) of the aluminum fluoride hydrate which precipitated in the reaction system transfer to a filtration process from a reaction system, it is 30-30 degrees C or less normally, Preferably it is 30-40 degrees C If the slurry is kept in the reaction system to a temperature lower than 30 ° C., the particle size becomes smaller due to stirring in the reaction system, which causes troubles such as clogging of the filter cloth in the filtration process. In addition, when the temperature is higher than 50 ° C., there arises a problem that corrosion of equipment such as a classifier is accelerated in the next process.

  According to the production method of the present invention, there are no problems such as a decrease in yield and equipment corrosion, and high-purity aluminum fluoride can be produced industrially advantageously.

  Hereinafter, preferred embodiments of the present invention will be described in detail based on examples and comparative examples.

[Examples 1 to 10]
Hydrofluoric acid having the composition shown in Table 1 was used as the raw material hydrofluoric acid, and the raw material aluminum hydroxide to be reacted with the hydrofluoric acid was produced by the Bayer method, and the water content was 8% by weight. Aluminum was used.
About raw material hydrofluoric acid, it adjusts to the hydrofluoric acid density | concentration (HF density | concentration) shown in Table 1 according to the liquid temperature, and shows in Table 1 according to the liquid temperature of raw material hydrofluoric acid in a reaction tank. Hydrofluoric acid adjusted to hydrofluoric acid concentration (HF concentration) was charged in the amount shown in Table 1.
The raw material charge was 2 tHF / day per batch, and was based on a reaction equivalent ratio of 1.00 and an aluminum hydroxide charge of 8% by weight of 2,826 kg.

Next, the reaction tank charged with hydrofluoric acid was corrected using the correction formula (1) or (2) shown in Table 2, and the pure reaction equivalent ratio [Al (OH) ₃ / 6HF] is added to the above aluminum hydroxide with stirring over the addition time shown in Table 2 to cause a neutralization exothermic reaction. The reaction liquid (slurry) contained was extracted from this reaction tank when it reached the temperature shown in Table 2, and transferred to the filtration tank of the next filtration step.

The reaction liquid (slurry) extracted from the reaction tank and transferred to the filtration tank is freed of adhering water by centrifugal dehydration, subsequently dried at 250 to 350 ° C. for 5 to 10 minutes, and then 250 to 400. It was calcined at 2 ° C. for 2 hours to obtain anhydrous aluminum fluoride.
About the obtained anhydrous aluminum fluoride of each Example 1-10, the composition and yield which were measured with the following analysis method are shown in Table 3.

(1) Analysis of “H ₂ O + LOI”: Burning loss method The sample is heated in an electric furnace at 500 ° C. for 1 hour, and the weight loss is calculated.
(2) Analysis of “SiO ₂ ”: JIS R9301-3-5
(3) Analysis of “Fe ₂ O ₃ ”: JIS R9301-3-6
(4) Analysis of “F”: EDTA titration method After dissolving the sample in potassium hydroxide solution, add potassium silicate solution to precipitate aluminum as aluminum silicate, and add lead acetate solution to the filtrate obtained by filtration The excess lead in the filtrate obtained by precipitating fluorine as lead chlorofluoride (PbClF) and filtered is titrated with an EDTA2Na standard solution to obtain the weight% of F.
(5) Analysis of “ALF ₃ ”:
Calculated from the analytical value of F obtained in (3) above.

[Comparative Example 1]
The reaction between hydrofluoric acid and aluminum hydroxide was replaced with the pure reaction equivalent ratio [Al (OH) ₃ / 6HF] of the present invention, and the total acid content (T-HF) in the hydrofluoric acid aqueous solution was used as a standard. Anhydrous aluminum fluoride was produced in the same manner as in Example 3 except that the reaction equivalent ratio [Al (OH) _{3 /} T-HF] calculated at 1.05 was used.
Table 4 shows the yield and composition of the anhydrous aluminum fluoride obtained in Comparative Example 1.

[Comparative Example 2]
Anhydrous aluminum fluoride was produced in the same manner as in Example 6 except that the pure reaction equivalent ratio [Al (OH) _{3 /} 6HF] 1.05 in the reaction between hydrofluoric acid and aluminum hydroxide was 1.05. went.
Table 4 shows the yield and composition of the anhydrous aluminum fluoride obtained in Comparative Example 2.

[Comparative Example 3]
Anhydrous aluminum fluoride was produced in the same manner as in Example 10 except that the pure reaction equivalent ratio [Al (OH) _{3 /} 6HF] was 0.90 in the reaction between hydrofluoric acid and aluminum hydroxide. went.
Table 4 shows the yield and composition of the anhydrous aluminum fluoride obtained in Comparative Example 3.

According to the method of the present invention, the pure reaction equivalent ratio [Al (OH) ₃ / 6HF] calculated based on the pure HF acid content from the total acid content standard so far is set to 0.90 <Al (OH) ₃ / By controlling within the range of 6HF <1.05, there are no problems such as yield reduction and equipment corrosion, and high-purity aluminum fluoride can be produced industrially advantageously. High-purity aluminum fluoride required in many fields such as refining fluxes, welding rod coatings, ceramics and other chemicals, and organic fluoride synthesis catalysts can be provided at low cost.

Claims (7)

Aluminum fluoride is added to and dissolved in an aqueous hydrofluoric acid solution to react hydrofluoric acid with aluminum hydroxide, and aluminum fluoride is precipitated from the resulting reaction solution as a hydrate. A pure hydrofluoric acid content (pure HF acid content) obtained by removing impurities other than hydrofluoric acid from the total acid content that reacts with aluminum hydroxide in the raw hydrofluoric acid. The pure reaction equivalent ratio [Al (OH) ₃ / 6HF] based on the acid content was calculated, and the pure reaction equivalent ratio of the reaction system of hydrofluoric acid and aluminum hydroxide was 0.90 <Al (OH) ₃ / 6HF. <The manufacturing method of the high purity aluminum fluoride characterized by controlling within the range of 1.05. The reaction equivalent ratio [Al (OH) ₃ / 6HF] in the reaction system is lowered when the concentration of the impurity acid contained in the raw hydrofluoric acid is high, and the concentration of the impurity acid is low. The method for producing high-purity aluminum fluoride according to claim 1, wherein the high-purity aluminum fluoride is corrected to be sometimes high. The reaction equivalent ratio [Al (OH) ₃ / 6HF] in the reaction system is corrected by adding the sulfuric acid content (H ₂ SiF ₆ minutes), sulfuric acid and phosphoric acid to the impurity acid content in the raw hydrofluoric acid. · comparing the phosphate content (TH ₂ SO ₄ minutes), based on the higher silicofluoride acid content of the impurity concentration (H ₂ SiF ₆ minutes) or sulfuric acid and phosphoric acid content (TH ₂ SO ₄ minutes), silicofluoride acid In the case of the minute (H ₂ SiF ₆ minutes), the following correction formula (1) is performed. In the case of the sulfuric acid / phosphoric acid content (TH ₂ SO ₄ minutes), the correction formula (2) is performed. The manufacturing method of high-purity aluminum fluoride of description.
y = 1.05-0.0075x (1)
y = 1.05-0.0060x (2)
[However, in correction formulas (1) and (2), y represents the reaction equivalent ratio [Al (OH) ₃ / 6HF] in the reaction system, and x represents the content of silicon hydrofluoric acid (H ₂ SiF ₆ minutes) or sulfuric acid / phosphoric acid content (TH ₂ SO ₄ minutes) concentration (HF / 200g / L equivalent g / L). ]   The method for producing high-purity aluminum fluoride according to any one of claims 1 to 3, wherein the peak temperature of the reaction system after dissolution of aluminum hydroxide is controlled to 100 ± 2 ° C.   The reaction system peak temperature after dissolution of aluminum hydroxide is controlled by adjusting the hydrofluoric acid concentration (HF concentration) of the reaction system to 170 to 200 g / in accordance with the liquid temperature of the hydrofluoric acid aqueous solution before dissolution of aluminum hydroxide. The manufacturing method of the high purity aluminum fluoride of Claim 4 performed by adjusting in the range of L.   The method for producing high-purity aluminum fluoride according to any one of claims 1 to 5, wherein aluminum hydroxide is added to the hydrofluoric acid aqueous solution within 50 minutes.   The high purity according to any one of claims 1 to 6, wherein the time required from the peak temperature of the reaction system after dissolution of aluminum hydroxide to the precipitation peak temperature of aluminum fluoride hydrate is controlled within a range of 3 to 4 hours. A method for producing aluminum fluoride.