JP2864617B2 - Process for producing hydrosilicofluoric acid, ammonium silicofluoride and high-purity silica - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention uses a crude silica as a raw material, and reacts it with ammonium fluoride and / or ammonium acid fluoride to obtain a reaction product containing ammonium silicofluoride. The present invention relates to a method for producing hydrosilicofluoric acid, ammonium silicofluoride and high-purity silica from a gas containing silicon tetrafluoride obtained by acid decomposition of the product. High-purity silica is useful as various functional materials such as a quartz raw material, a ceramic raw material, and a filler, and hydrosilicofluoric acid and ammonium silicofluoride are useful as synthetic intermediates of high-purity silica.

(Prior Art) Conventionally, as a method for producing silica powder, a method of neutralizing sodium silicate with an acid or an ion exchange resin (a silicate method) is generally used. , Al, Fe
Therefore, it cannot be used in a field where high purity is required because metallic impurities and anionic components such as are mixed. As a dry method, there is a method in which silicon tetrachloride is burned at high temperature in the presence of oxygen and hydrogen.However, special production equipment is required, and the cost is high, so the application is limited. different.

In addition, when silica is obtained by reacting ammonia in an aqueous medium using hydrofluoric acid and / or ammonium silicofluoride as a raw material, ammonium byproduct by-product has low industrial utility and is co-produced. We face the problem of disposing of it as industrial waste rather than its advantages.

Still further, a method is disclosed in which a compound or a mixture usable as a silica source is dissolved in a mixed solution of hydrofluoric acid and sulfuric acid, and a solution obtained by distilling the obtained solution is used to obtain silica from fluoride of silicon. However, this method is not an economical industrial process because expensive hydrofluoric acid is used in this method.

(Problems to be Solved by the Invention) In view of the above-mentioned problems of the prior art, the present inventors have conducted intensive research on a method for producing high-purity silica, and as a result, completed the present invention. That is, the present invention relates to a method for producing crude silica and ammonium fluoride (NH ₄ F) and / or acidic ammonium fluoride (NH ₃ .HF ₂ ).
Is a method for producing hydrosilicofluoric acid (H ₂ SiF ₆ ), ammonium silicofluoride ((NH ₄ ) ₂ SiF ₆ ) and high-purity silica using acid components as raw materials. A reaction product containing ammonium silicofluoride obtained by the reaction is used as an intermediate, and a gas containing silicon tetrafluoride obtained by acid decomposition of the reaction product is absorbed into water, ammonium fluoride solution or aqueous ammonia. Hydrofluorosilicic acid, ammonium silicofluoride and high-purity silica can be obtained, and the obtained hydrosilicofluoric acid and ammonium silicofluoride can be reacted with ammonia to obtain high-purity silica.

Ammonium fluoride and / or ammonium acid fluoride used in the present invention is a by-product when silica is obtained by reacting hydrosilicofluoric acid and / or ammonium silicofluoride with ammonia in an aqueous medium. This can be used cyclically. Also, the ammonia component recovered in the deammonification reaction can be reused as a raw material for producing silica. Therefore, according to the method of the present invention, it is not necessary to treat expensive production raw materials and industrially excessive by-products as in the conventional method, and an economical industrial process is realized by recycling inexpensive production raw materials and by-products. High-purity silica useful as various functional materials can be supplied at low cost.

(Means for Solving the Problems) The present invention comprises the following three steps (A) to (C): (A) a deammonia reaction between crude silica and ammonium fluoride and / or ammonium acid fluoride to form a silica A step of obtaining a reaction product containing ammonium fluoride; and (B) a step of acid-decomposing the product or, after adding silica to the product, acid-decomposing to obtain a gas containing silicon tetrafluoride. (C) a step of absorbing the gas into water or an ammonium fluoride solution, and a method for producing hydrosilicofluoric acid and / or ammonium silicofluoride.

The present invention further comprises the following three steps (A) to (C) and the following step (D). (D) Hydrofluoric acid and / or fluorinated silicon obtained in step (C) Reacting ammonium with ammonia in an aqueous medium, and a method for producing high-purity silica.

Furthermore, the present invention is characterized in that the gas containing silicon tetrafluoride obtained in the two steps (A) and (B) is reacted with ammonia in an aqueous medium in the step (C). The present invention relates to a method for producing high-purity silica.

 The above production method of the present invention is exemplified by the following reaction formula.

(A) deammoniation step crude _{SiO 2 + 6NH 4 F → (} NH 4) 2 SiF 6 + 4NH 3 + 2H 2 O A-1 crude _{SiO 2 + 3NH 3 · HF 2} → (NH 4) 2 SiF 6 + NH 3 + 2H 2 OA- 2 (B) Acid decomposition step In the case of sulfuric acid and phosphoric acid as the acid, (NH ₄ ) ₂ SiF ₆ + 2H ₂ SO ₄ → SiF ₄ + 2HF + 2NH ₄ HSO ₄ B-1 (NH ₄ ) ₂ SiF ₆ + 2H ₃ PO ₄ → _{SiF 4 + 2HF + 2NH 4 H} 2 PO 4 B-2 (NH 4) 2 SiF 6 + 1 / 2SiO 2 + 2H 2 SO 4 → 3 / 2SiF 4 + 2NH 4 HSO 4 + 2H 2 O B-3 (NH 4) 2 SiF 6 + NH 4 F + 3H ₂ SO ₄ → SiF ₄ + 3HF ++ 3NH ₄ HSO ₄ B-4 (C) Gas absorption process SiF ₄ + 2HF → H ₂ SiF ₆ C-1 SiF ₄ + 2 / 3H ₂ O → 2 / 3H ₂ SiF ₆ +1/3 SiO ₂ C -2 SiF ₄ + 2NH ₄ F → (NH ₄ ) ₂ SiF ₆ C-3 (D) Silica production process SiF ₄ + 4NH ₃ + 2H ₂ O → SiO ₂ + 4NH ₄ F D-1 H ₂ SiF ₆ + 6NH ₃ + 2H ₂ O → state of _{SiO 2 + 6NH 4 F D-} 2 (NH 4) 2 SiF 6 + 4NH 3 + 2H 2 O → SiO 2 + 6NH 4 F D-3 above reaction formula present invention Is an example of a manufacturing method of the present invention is not intended to be of course limited to these reaction formulas.

In the production method of the present invention, first, in step (A), ammonia produced by the reaction of raw silica with ammonium fluoride and / or ammonium acid fluoride is removed out of the system (recoverable), and the silica is removed. Generate ammonium bromide. The obtained reaction product containing ammonium silicofluoride contains impurities in crude silica, but is reacted with an acid component in the acid decomposition step (B) (if necessary, a silica source is added). Impurities in the crude silica remain in the liquid layer, and the silicon component is gasified and purified as a gas containing silicon tetrafluoride. The silicon tetrafluoride-containing gas is usually composed of a mixture of silicon tetrafluoride containing water and hydrogen fluoride, and is absorbed by water or an ammonium fluoride solution in the gas absorption step of step (C) to form a silicon fluoride. It is recovered as hydroic acid and / or hydrosilicofluoric acid, but is directly absorbed with aqueous ammonia (reaction formula D-1).
High-purity silica can be obtained at once.

In the silica production step (D), the recovered hydrosilicofluoric acid and / or ammonium silicofluoride is reacted with ammonia in an aqueous medium to obtain high-purity silica.

The by-product ammonium fluoride in the silica production process is recovered as a mother liquor after the silica is separated, and can be recycled as a raw material in the first deammonification process.

 Next, the production method of the present invention will be described in detail.

In the deammonification step (A), the crude silica used as a raw material refers to a compound or mixture containing silica, that is, a substance that can be used as a silica source. Specific examples thereof include diatomaceous earth, silica stone, silica sand, rice husk ash, and silicate-containing minerals obtained as natural products. Mullite, zircon, etc. can also be used, and furthermore, silica fume, which is known as synthetic silica, obtained by collecting waste gas generated during ferrosilicon production, fly ash, blast furnace slag, silica, a by-product from a coal-fired power plant, Examples include soda silica, but are not limited to these. As the coarse silica, the higher the silica content, the better, usually 20% or more, preferably 50% or more, and more preferably 80% or more. In addition to the above silica content, the types of impurities, silica physical properties, and silica reactivity In consideration of the availability, the price, etc., it may be appropriately selected according to the intended use of the high-purity silica.

The ammonium fluoride used may be a solid or a solution that can be injected as a reagent or an industrial chemical, but may be a hydrofluoric acid and / or a by-product fluorine obtained by separating silica from a reaction product of ammonium silicofluoride and aqueous ammonia. It is desirable to recycle the ammonium halide mother liquor. In this case, the mother liquor may contain other components, such as excess ammonia and metallic impurities, and the mother liquor can be diluted or concentrated as necessary.

Ammonium acid fluoride can also be used as a raw material, and industrial chemicals and the like may be used in the same manner as described above, but a deammonification reaction product obtained by heating and concentrating an ammonium fluoride mother liquor in silica production (see the following reaction formula) should be used. Is desirable.

NH ₄ F → 1 / 2NH ₃・ HF ₂ + 1 / 2NH ₃ ↑ Since the above reaction requires high temperature conditions of 100 ° C or higher to increase the reaction rate, usually the deammonia reaction rate is limited to about 20 to 80%, What is necessary is just to provide to the reaction with the crude silica as a mixed solution or a mixed slurry of ammonium fluoride and ammonium acid fluoride.

The reaction between the crude silica and ammonium fluoride and / or ammonium acid fluoride is usually performed in an aqueous medium under heating conditions, but a solid-phase reaction may be performed as a dry method.

As the aqueous medium, water or a mixed system of water and an organic solvent inert to raw materials and products can be used, but an aqueous system is preferable for handling reasons.

The chemical equivalent of NH ₄ F / SiO ₂ = 6 is used as the molarity of the raw material used, but the molar ratio varies depending on the purity, reactivity, and target reaction rate of the raw silica, and the NH ₄ F / SiO ₂ molar ratio is usually It is carried out in the range of 1 to 10, preferably in the molar ratio of 3 to 8. When the molar ratio exceeds 6, excess NH ₄ F remains in the reaction system, and when the molar ratio is less than 6, unreacted SiO ₂ remains.

The reaction is usually carried out under heating conditions, preferably at 50 ° C or higher,
More preferably, it is carried out at a temperature of 80 ° C. or higher. The pressure in the reaction system is often around normal pressure or under reduced pressure, but it may be carried out under pressurized conditions while removing NH ₃ gas by-produced. The reaction method may be a batch method in which the raw materials are premixed or one raw material is charged and the other is added in the heating and concentration of the raw material mixture, or both the raw materials are simultaneously added to the reaction system and the product is continuously extracted. It is also possible to carry out in a continuous manner. Although the reaction time cannot be unconditionally determined by other conditions, it is usually several minutes to several tens of hours, preferably within 10 hours, more preferably within 5 hours.

As the reaction proceeds, ammonia is taken out of the system and recovered as a gas or aqueous ammonia, and at the same time, the silica in the reaction slurry is converted into system ammonium fluoride.

The recovered ammonia is usually recovered as ammonia water, and can be circulated and used in a silica production process described later.

The deammonification reaction product depends on the raw material composition, the reaction rate, and the concentration, but the raw material SiO ₂ , the raw NH ₄ F, the generated (NH ₄ ) ₂ SiF ₆ ,
This is a water slurry in which by-product NH ₃ and impurities in the crude silica are mixed.

When using ammonium acid fluoride or a mixture thereof with ammonium fluoride as the raw material, the raw material molar ratio is NH ₃ .H
The molar ratio is usually in the range of 0.5 to 5, preferably 1.5 to 4, although F ₂ / SiO ₂ = 3 is equivalent. The reaction proceeds at a considerably lower temperature than when ammonium fluoride is used as a raw material, and the reaction temperature may be around room temperature. However, to increase the reaction rate, it is desirable to carry out the reaction under heating conditions, preferably at 50 ° C. or higher.

The reaction method is the same as that for ammonium fluoride, and the reaction conditions are the same as described above.

In the following acid decomposition step (B), the reaction product containing ammonium silicofluoride obtained in step (A) is reacted with an acid component to obtain a gas containing silicon tetrafluoride. Requires low volatility, and usually uses sulfuric acid and / or phosphoric acid which can be obtained relatively inexpensively, but of course is not limited thereto.

For the purpose of promoting the reaction, it is desirable that the acid component has a high concentration, and when sulfuric acid is used, it is usually at least 20% by weight, preferably 50% by weight.
Above, more preferably, a concentration of 65% by weight or more is used. When phosphoric acid is used, the concentration is preferably 10% by weight or more, preferably 20% by weight or more in terms of P ₂ O ₅ concentration.

The acid component does not necessarily need to be of high purity.
The presence of volatile or decomposable impurities that evaporate with the silicon fluoride containing gas is undesirable and its content is limited.

The gas component generated in the acid decomposition step (B) is mainly composed of silicon tetrafluoride and hydrogen fluoride, and its composition depends on the composition of the ammonium silicofluoride mixture as the raw material, the type of the acid component, and the acid decomposition reaction. different.

For example, as shown in the above reaction formula B-1, high-temperature conditions are required for decomposing ammonium silicofluoride without the coexistence of silica, but if the reaction rate is 100%, the gas composition HF / SiF ₄ =
When the reaction is carried out in the presence of a sufficient amount of silica in the case of the formula B-3, silicon tetrafluoride gas is selectively generated.

In addition, when the acid decomposition reaction and gas recovery are quantitatively performed using an equimolar mixture of ammonium silicofluoride and ammonium fluoride in the formula B-4, the gas composition HF / SiF
₄ = 3.

The boiling point of silicon fluoride, which is a gas component, is about -96 ° C, and the boiling point of hydrogen fluoride is 19 ° C. Fluorine fluoride gas is more expensive, and on the other hand, more severe acid decomposition reaction conditions (high temperature, increased vacuum) are required to achieve a high recovery rate of hydrogen fluoride gas.

Therefore, for the purpose of increasing the fluorine component recovery rate in the step (B), it is more advantageous to add silica to recover the fluorine component as silicon tetrafluoride.

In the gas absorption step of the step (C) of the present invention, the gas containing silicon tetrafluoride is recovered as water hydrofluoric acid and / or ammonium silicofluoride by absorbing it with water or an ammonium fluoride solution.

For example, when the gas composition HF / SiF ₄ = 2 (Formula C-1), hydrosilicofluoric acid is obtained by water absorption, and the gas composition is Si
For F ₄ only (Formula C-2), to obtain a hydrosilicofluoric acid while not accompanied by-production of the silica to. Actually the gas composition is HF / SiF ₄
= 0 to 2 (that is, intermediate between the formulas B-1 and B-2) in many cases.

When the gas containing silicon tetrafluoride is absorbed by the ammonium fluoride solution, if the gas composition is only SiF ₄ and a sufficient amount of ammonium fluoride is present (formula C-3), the silicon fluoride is used. Although it is recovered as an ammonium fluoride solution, in fact, the gas composition fluctuates and the amount of ammonium fluoride in the absorbing solution can be arbitrarily set, so that it is recovered as a mixture of hydrosilicofluoric acid and ammonium silicofluoride. Often.

The above-mentioned water or ammonium fluoride absorbing liquid may contain other components such as ammonia, hydrogen fluoride or ammonium acid fluoride within a range not departing from the object of the present invention.

Still another embodiment of the gas absorption step is to directly absorb silicon tetrafluoride-containing gas with an aqueous solution containing ammonia to directly obtain high-purity silica (formula D-1).

Hydrofluoric acid and / or ammonium silicofluoride obtained in the gas absorption step of step (C) can be converted from non-volatile or low-volatile impurities by gasification as a gas containing silicon tetrafluoride. Since it is purified, it is a high-purity product containing substantially no metallic impurities.

In the process for producing high-purity silica of the present invention, in addition to the method of directly absorbing high-purity silica by directly absorbing the silicon tetrafluoride-containing gas with an aqueous solution containing ammonia, the process (D) includes the process (C). High-purity silica is obtained from the hydrosilicofluoric acid and / or ammonium silicofluoride obtained in the gas absorption step, and the ammonia used in the step (D) is gaseous or aqueous ammonia; , 5-28
% Reagent or industrial ammonia water may be used, but the ammonia component recovered in the deammonification step of the present invention may be recycled.

This step (D) is carried out in an aqueous medium and usually uses water, but may of course contain an organic solvent or various additives. Ammonia and an aqueous medium having good purity within a range for obtaining high-purity silica are used.

The molar ratio of ammonia is stoichiometrically NH ₃ / H ₂ SiF ₆ = 6
(See formula D-2), NH ₃ / (NH ₄ ) ₂ SiF ₆ = 4 (see formula D-3), but the molar ratio of ammonia to fluorine content in hydrosilicofluoric acid and / or ammonium silicofluoride The NH ₃ / F molar ratio is usually about 0.3 to 2.0, preferably about 0.5 to 1.5, and more preferably about 0.7 to 1.2.

It is desirable that the increase the yield of the silica is in slight excess of ammonia (eg, 1.1 to 1.5 in NH ₃ / F molar ratio),
On the other hand, when the by-product ammonium fluoride mother liquor is circulated, it is not preferable to use an excessively large amount of ammonia.

Reaction conditions are selected according to the desired silica properties.

The reaction type can be a batch type or a continuous type. As a raw material addition method, a method in which an ammonia component is added to an aqueous medium of hydrofluoric acid and / or ammonium silicofluoride, and conversely, an ammonia component is added. Is added in advance and other components are added, furthermore, a method in which hydrofluoric acid and / or ammonium silicofluoride and an ammonia component are added simultaneously, and a combination of the above methods.

In the method (1), silica is generated in the acidic pH range at the start of the reaction, and relatively dense and fine silica particles are obtained.

In this method, silica is generated in a high pH range, and relatively coarse silica particles can be obtained.

In the method (1), silica particles can be grown under a constant pH condition by controlling the feed rate of the raw material to the reaction system.

The reaction of hydrosilicofluoric acid and / or ammonium silicofluoride with ammonia in an aqueous medium is usually carried out at a temperature in the range of 0 to 100 ° C., particularly when the reaction is started at around room temperature and the heat of reaction is 10 to 50 ° C. The reaction is often carried out with a slight increase in temperature, but may be carried out at a high temperature of 80 ° C. or higher in some cases.

The above reaction is usually carried out at about normal pressure, but may be carried out under pressure at a temperature of 100 ° C. or higher or under reduced pressure.

Although the reaction time cannot be uniformly defined depending on the reaction type, addition method, other reaction conditions, and the like, it is usually about 1 minute to 10 hours, and an aging time can be provided as necessary.

The silica concentration in the reaction system is usually in the range of about 0.5 to 13%, preferably 1 to 10%, more preferably 2 to 7%.
It is. If the silica concentration is too low, the production efficiency of the silica particles decreases, and if it is too high, the reaction control becomes difficult.

In the above reaction, additives other than the raw materials, for example, various salts (ammonium fluoride, ammonium chloride, ammonium sulfate, etc.), binders (PVA, celluloses), surfactants and the like can be coexistent in the reaction system.

A silica slurry is obtained by selecting these reaction conditions, i.e., starting material type and molar ratio, reaction type, addition method, pH, temperature, time, silica concentration, additives and the like.

Since the silica slurry obtained by the reaction coexists with the ammonium fluoride solution or slurry produced as a by-product, the silica cake is usually obtained by a solid-liquid separation operation such as filtration under reduced pressure, filtration under pressure, and centrifugation. Since this cake contains a small amount of ammonium fluoride in the form of mother liquor adherence, it is removed by washing or the like. At this time, the coexisting ammonia component can be removed by acid washing, hot water extraction, or the like.

The wet silica obtained in the above treatment is dried at a temperature of about 50 to 200 ° C. by hot air drying, vacuum drying, fluidized drying, spray drying, etc., and is fired at a high temperature of 500 ° C. or more, and even 900 ° C. or more as necessary. .

In addition, after removing water by spray drying or the like of the silica slurry in advance, it is possible to remove coexisting ammonium fluoride and the like by washing with water, but the manufacturing process becomes complicated.
It is not advantageous in terms of the purity of the obtained silica.

The hydrosilicofluoric acid, ammonium silicofluoride, and high-purity silica obtained by the production method of the present invention contain substantially no metallic impurities and have an impurity content of 10 as metal oxides.
0 ppm or less, preferably 10 ppm or less, more preferably 1 ppm
And the anion component is extremely small.

Hereinafter, the present invention will be described in more detail with reference to examples.
The percentages in the examples are% by weight.

Example 1 (A) 0.72 kg of diatomaceous earth (trade name: TOALITE, silica purity: 83.0%, manufactured by Toa Kasei Co., Ltd.) as crude silica in 10 stirred reactors equipped with a thermometer and a 30% aqueous ammonium fluoride solution
7.4 kg was added and stirred in a 130 ° C. oil bath. Distillation of water containing ammonia started with the rise of the reaction temperature, and the mixture was heated and stirred for 5 hours until the liquid temperature reached 98 ° C., and the reaction slurry 3.
8 kg was obtained. 4.3 kg of a distillate containing 0.64 kg of ammonia was recovered outside the reaction system.

(B) The obtained reaction slurry is a mixture containing ammonium diafluoride as a main component, and 4.27 kg of a mixed slurry obtained by adding 0.47 kg of the above diatomaceous earth is added to 4.13 kg of 95% sulfuric acid over 2 hours. The reaction temperature is 80 ° C in a 115 ° C oil bath under reduced pressure.
While stirring.

(C) The generated silicon tetrafluoride-containing gas was absorbed in 4.0 kg of pure water to obtain 6.5 kg of an aqueous solution of hydrosilicofluoric acid in which silica was partially deposited. The supernatant of the hydrosilicofluoric acid aqueous solution in which silica was allowed to settle by standing was partially used as a sample for analysis, and the remainder was used as an intermediate material for silica production.

The analytical value of hydrosilicofluoric acid in the supernatant was 21.5% (however, F1
7.0%, Si 4.7%).

(D) 2.2 kg of 25% ammonia water with 3.2 kg of the above hydrosilicofluoric acid
For 30 minutes at room temperature to obtain a silica slurry. This was filtered under reduced pressure to recover 4.3 kg of a mother liquor containing ammonium fluoride.

The composition of the recovered mother liquor was determined by chemical analysis (NH ₃ content 10.8%,
(F content: 10.7%), it contained 0.896 kg of ammonium fluoride and 0.10 kg of ammonia.

The filtered silica cake was washed with a large amount of pure water and dried with hot air to obtain 0.30 kg of silica powder.

The analytical values of the crude silica used as a raw material and the obtained high-purity silica of the present invention are shown below.

Raw material (%) Product (ppm) Fe ₂ O ₃ 1.4 2.3 Al ₂ O ₃ 4.4 <1.0 CaO 0.3 <1.0 Example 2 (A) 60 g of diatomaceous earth was added to a stirred reactor equipped with a thermometer.
And 1000 g of a mother liquor of ammonium fluoride as a by-product during the production of silica obtained in Example 1 (D), and the mixture was heated and stirred in a 130 ° C. oil bath. The mixture was heated and concentrated for 5 hours until the reaction temperature reached 98 ° C. to obtain 400 g of a slurry.

(B) 95% sulfuric acid 43%
0 g in a 170 ° C oil bath until the liquid temperature reaches 98 ° C.
The mixture was stirred under heating for an hour to obtain a reaction slurry.

(C) 15% of the generated mixed gas of silicon tetrafluoride and hydrogen fluoride
Absorbed in 630 g of aqueous ammonia to form silica.

The obtained silica slurry was subjected to post-treatment in the same manner as in Example 1 to obtain 53 g of silica powder.

The analytical values of the raw crude silica and the obtained silica powder are shown below.

Raw material (%) Product (ppm) Fe ₂ O ₃ 1.42 <1 Al ₂ O ₃ 1.30 <1 CaO 0.07 <1 NaO ₂ 0.42 <1 Example 3 (A) In two stirred reactors equipped with a thermometer, As coarse silica, 70 g of silicate method silica (trade name: Nip Seal manufactured by Nippon Silica Co., Ltd.), 171 g of ammonium acid fluoride and 399 g of water were added, and the mixture was stirred at room temperature for 30 minutes, and then the liquid temperature became 98 ° C in an oil bath at 130 ° C. Until stirring for 5 hours to obtain a reaction slurry.

(B) To the obtained deammonification reaction slurry, 35 g of the crude silica used in the step (A) was added, and this was continuously supplied to 410 g of 95% sulfuric acid heated and stirred at 80 ° C. under reduced pressure.

(C) The generated silicon tetrafluoride-containing gas was absorbed into 540 g of a 20% ammonium fluoride solution to obtain a slurry of ammonium silicofluoride. The precipitated ammonium silicofluoride was collected by filtration to obtain 130 g of white crystals. X-ray diffraction and elemental analysis confirmed that it was ammonium silicofluoride. The impurity analysis value (ppm) is shown below.

Fe ₂ O ₃ <1 Al ₂ O ₃ <1 CaO <1 NaO ₂ <1 (D) Dissolve 35 g of the obtained ammonium silicofluoride in 315 g of pure water and blow in 20 g of gaseous ammonia for 30 minutes under ice-cooling.
Fine silica was formed.

 The analytical values (ppm) of the obtained silica powder are shown below.

Fe ₂ O ₃ <1 Al ₂ O ₃ <1 CaO <1 NaO ₂ <1 Example 4 (A) Silica method silica (trade name, manufactured by Nippon Silica Co., Ltd.) was used as crude silica in 10 stirred reactors equipped with a thermometer. 900 g of nip seal) and 10 kg of a silica mother liquor containing ammonium fluoride by-produced during the production of silica obtained in Example 1 (D),
Stirred in oil bath at ℃. Distillation of ammonia-containing water was started as the reaction temperature was increased, and the mixture was heated and stirred for 5 hours until the liquid temperature reached 98 ° C. to obtain a reaction slurry.

(B) 60% of the obtained ammonium silicofluoride mixture 6.1 kg
The mixture was added to 51 kg of a phosphoric acid solution over 3 hours, and heated and stirred for 5 hours while maintaining the reaction temperature at 90 ° C. in a 130 ° C. oil bath under reduced pressure.

(C) The generated gas containing silicon tetrafluoride was absorbed by 16 kg of a 20% ammonium fluoride solution to obtain 62 kg of a mixed solution of hydrofluoric acid and ammonium silicofluoride.

(D) 4.5 kg of the above mixed solution was added to 4.5 kg of about 15% ammonia water recovered in Example 1 (A).
Each was continuously supplied into a stirring reactor, and the obtained silica reaction slurry was continuously extracted.

The obtained slurry was subjected to solid-liquid separation by a filter press, washed with a large amount of pure water, extracted a silica cake, and dried with hot air to obtain 0.4 kg of silica powder.

 The analytical values (ppm) of the obtained silica powder are shown below.

Fe ₂ O ₃ <1 Al ₂ O ₃ <1 CaO <1 NaO ₂ <1 Example 5 2000 g of the silica mother liquor obtained in Example 1 (D) was heated and concentrated in an oil bath at 170 ° C. in a 5 stirred vessel. Mixed solution of ammonium fluoride and ammonium fluoride with NH ₃ / F molar ratio of 0.9
830 g was obtained. This product corresponds to a mixture composition of 269 g of NH ₃ and 57 g of NH ₃ .HF ₂ .

(A) To 10 stirred reactors equipped with a thermometer, 120 g of silica fume (manufactured by Nippon Heavy Industries, Ltd.) as crude silica and 830 g of the above-mentioned mixed solution of ammonium fluoride and ammonium fluoride were added, and an oil bath at 130 ° C. With stirring. As the reaction temperature rises, the distillation of water containing ammonia starts, and the liquid temperature rises to 98.
The mixture was heated and stirred for 5 hours until the temperature reached ℃, to obtain a reaction slurry.

(B) 860 g of the obtained ammonium silicofluoride mixture was added to sulfuric acid 47
The mixture was added to 11.5 kg of a 60% phosphoric acid solution containing 0 g, and heated and stirred for 5 hours while maintaining the reaction temperature at 80 ° C. in a 120 ° C. oil bath under reduced pressure.

(C) The generated silicon tetrafluoride-containing gas was absorbed in pure water to obtain 900 g of hydrosilicofluoric acid in which 30 g of silica was precipitated.

The concentration of hydrosilicofluoric acid obtained by filtering off silica was 21.9%.

(D) The obtained hydrosilicofluoric acid was treated in the same manner as in (D) of Example 1 to obtain 80 g of silica powder.

 The analytical values (ppm) of the obtained silica powder are shown below.

Fe ₂ O ₃ <1 Al ₂ O ₃ <1 CaO <1 NaO ₂ <1

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshito Yuri, 638 Sasakura, Funaka-cho, Nigane-gun, Toyama Prefecture Inspector, Nissan Chemical Industry Co., Ltd. , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C01B 33/10 C01B 33/18

Claims (12)

(57) [Claims] 1. A reaction product containing ammonium silicofluoride by the following three steps (A) to (C): (A) a deammonia reaction of crude silica with ammonium fluoride and / or ammonium acid fluoride; (B) obtaining a gas containing silicon tetrafluoride by acid decomposition of the product, and (C) absorbing the gas into water or an ammonium fluoride solution. To produce hydrosilicofluoric acid and / or ammonium silicofluoride. 2. An ammonium fluoride obtained by reacting hydrofluoric acid and / or ammonium silicofluoride with ammonia in an aqueous medium as the ammonium fluoride in the step (A). 2. A process for producing hydrosilicofluoric acid and / or ammonium silicofluoride according to claim 1. 3. The following three steps (A) to (C): (A) a reaction product containing ammonium silicofluoride by deammonifying crude silica with ammonium fluoride and / or ammonium acid fluoride; (B) a step of adding silica to the product and subjecting it to acid decomposition to obtain a gas containing silicon tetrafluoride, and (C) a step of absorbing the gas into water or an ammonium fluoride solution. A method for producing hydrosilicofluoric acid and / or ammonium silicofluoride, comprising: 4. Ammonium fluoride obtained by reacting hydrosilicofluoric acid and / or ammonium silicofluoride with ammonia in an aqueous medium as the ammonium fluoride in the step (A) of claim 3 The method for producing hydrosilicofluoric acid and / or ammonium silicofluoride according to claim 3, wherein 5. The following three steps (A) to (C): (A) a reaction product containing ammonium silicofluoride by subjecting the crude silica to a deammonification reaction with ammonium fluoride and / or ammonium acid fluoride; (B) a step of acid-decomposing the product to obtain a gas containing silicon tetrafluoride, and (C) a step of reacting the gas with ammonia in an aqueous medium. A method for producing high-purity silica. 6. An ammonium fluoride obtained by reacting hydrofluoric acid and / or ammonium silicofluoride with ammonia in an aqueous medium as the ammonium fluoride in the step (A). The method for producing high-purity silica according to claim 5, which is used. 7. The following three steps (A) to (C): (A) a reaction product containing ammonium silicofluoride by subjecting the crude silica to a deammonification reaction with ammonium fluoride and / or ammonium acid fluoride; (B) adding silica to the product and subjecting it to acid decomposition to obtain a gas containing silicon tetrafluoride; and (C) reacting the gas with ammonia in an aqueous medium. A method for producing high-purity silica, characterized in that: 8. The ammonium fluoride in the step (A) according to claim 7, wherein ammonium fluoride obtained by reacting hydrosilicofluoric acid and / or ammonium silicofluoride with ammonia in an aqueous medium. The method for producing high-purity silica according to claim 7, which is used. 9. The following four steps (A) to (C): (A) a reaction product containing ammonium silicofluoride by subjecting the crude silica to a deammonification reaction with ammonium fluoride and / or ammonium acid fluoride; (B) a step of acid-decomposing the product to obtain a gas containing silicon tetrafluoride; (C) absorbing the gas in water or an ammonium fluoride solution to obtain hydrosilicofluoric acid and / or Or a step of obtaining ammonium silicofluoride; and (D) a step of reacting the obtained hydrosilicofluoric acid and / or ammonium silicofluoride with ammonia in an aqueous medium. Law. 10. An ammonium fluoride obtained by reacting hydrosilicofluoric acid and / or ammonium silicofluoride with ammonia in an aqueous medium as the ammonium fluoride in the step (A). The method for producing high-purity silica according to claim 9, which is used. 11. The following four steps (A) to (D): (A) A reaction product containing ammonium silicofluoride by subjecting a crude silica to a deammonification reaction with ammonium fluoride and / or ammonium acid fluoride. (B) adding silica to the product and subjecting it to acid decomposition to obtain a gas containing silicon tetrafluoride; (C) absorbing the gas into water or an ammonium fluoride solution to obtain (D) reacting the obtained hydrosilicofluoric acid and / or ammonium silicofluoride with ammonia in an aqueous medium. A method for producing high-purity silica. 12. An ammonium fluoride obtained by reacting hydrofluoric acid and / or ammonium silicofluoride with ammonia in an aqueous medium as the ammonium fluoride in the step (A). 12. The method for producing high-purity silica according to claim 11, which is used.