JPH03218914A - Production of high purity silica and ammonium fluorosilicate - Google Patents

Abstract

PURPOSE:To obtain high purity silica in a clean industrial process without requiring treatments on the reaction product by separating impurities from ammonium fluorosilicate obtained from clude silica and (acid) ammonium fluoride by used of the difference in solubilities, and then effecting the reaction of ammonium fluorosilicate with ammonia in a water-base medium. CONSTITUTION:Ammonium fluorosilicate is obtained by bringing clude silica into reaction with ammonium fluoride or acid ammonium fluoride in a water- based medium. The unreacted silica and impurities in the reaction mixture are separated from ammonium fluorosilicate solution by solid-liquid separation method, and the obtd. ammonia fluorosilicate is made to react with ammonia in a water-base medium. By this method, high purity silica can be obtained from a cheap source material without requiring treatments on the expensive reaction product and without causing byproduct of waste acid. It is preferable to recycle the ammonium fluoride obtained as the byproduct in the separation process of silica by the reaction with ammonia.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention uses crude silica consisting of a compound or mixture that can be used as a silica source as a raw material, and produces ammonium fluoride and/or acidic ammonium fluoride in an aqueous medium. The present invention relates to a method for producing high-purity silica, which comprises reacting to obtain ammonium fluorosilicate, and reacting this with ammonia in an aqueous medium. In addition, ammonium fluoride is obtained by reacting ammonium fluoride and/or acidic ammonium fluoride with an acid component in an aqueous medium using crude acid as a raw material, and this is then reacted with ammonia in an aqueous medium. The present invention relates to a method for producing high-purity silica. Furthermore, the present invention relates to a method for producing high-purity ammonium silicofluoride, which is characterized in that crude silica is used as a raw material and ammonium fluoride is reacted to obtain high-purity ammonium fluorosilicate.

Demand for high-purity silica is increasing as a functional material for quartz raw materials, ceramic raw materials, fillers, etc. High purity ammonium silicofluoride is useful as an intermediate in the production of high purity silica.

[Conventional technology]

Traditionally, silica has been produced by neutralizing sodium silicate with acid or ion exchange resin (wet method using sodium silicate as a raw material), but while this method is low cost, Because it is contaminated with metallic impurities such as sodium, aluminum, and iron, it cannot be used in fields that require high purity.

In addition, as a dry method, silicon tetrachloride is mixed in the presence of oxygen and hydrogen.
Although there is a method of high-temperature combustion, its use is limited due to the high cost, and the physical properties of the resulting silica are different from those of wet-process silica, which limits the control of physical properties.

Furthermore, as a method to obtain silica from silicofluoride, silica or silicate is treated with scorching heat and then reacted with ammonium fluoride.
A method of producing silica fluoride, ammonium silicofluoride, and/or silicon diaminotetrafluoride, volatilizing them, recovering them, and reacting the recovered product with ammonia to obtain silica and ammonium fluoride (US Pat. No. 1, No. 859.988, U.S. Pat. No. 1,959.749), a compound or mixture that can be used as a silica source is dissolved in a mixture of hydrofluoric acid and sulfuric acid, and the resulting solution is distilled to produce silicon. A method of recovering fluoride and obtaining silica from it (JP-A-62-15
No. 3111), a fluorine-containing phosphorus source such as phosphate rock is treated with an acid to obtain a silicon tetrafluoride-containing gas, and this gas is absorbed in water or an aqueous ammonium fluoride solution to produce a A known method is to obtain ammonium fluoride, use ammonium fluorosilicide in the case of hydrofluorosilicic acid, and obtain silica and ammonium fluoride from ammonium fluorosilicide and ammonia (European Patent No. 337.712). ing.

U.S. Patent Nos. 1,859,988 and 1,959,749
The method described in the publication has a long reaction process and a reaction temperature of 30°C.
The temperature is high, above 0°C, and there may be a problem with the material of the equipment.

The method described in JP-A-62-153111 uses expensive hydrofluoric acid and produces waste acid as a by-product due to the use of a considerable amount of sulfuric acid, so it cannot be called an industrial process.

The method described in European Patent No. 337.712 has no industrial merit unless it is incorporated into a wet phosphoric acid production plant, and the gasification purification method has problems with the loss of silicon tetrafluoride and hydrogen fluoride in the gas absorption process. Scaling of silica may cause operational problems, and equipment costs are also high.

[Problem to be solved by the invention]

As mentioned above, conventional methods for producing silica powder have various problems. Therefore, the present inventors conducted extensive research and completed the present invention in order to solve this problem. That is, the present inventors produced ammonium silicofluoride from crude silica and ammonium fluoride and/or acidic ammonium fluoride, separated the impurities in this reaction product by utilizing the solubility difference, and then produced the resulting product. We have found that high purity silica can be obtained by reacting the ammonium fluorosilicate with ammonia in an aqueous medium.

Furthermore, the ammonium fluoride used in the method of the present invention is
Ammonium fluoride produced by reacting ammonium fluorosilicate and ammonia in an aqueous medium can be recycled to the first reaction. Therefore, according to the method of the present invention, there is no need to treat expensive production raw materials or reaction by-products as in the conventional method, and the process is economical and clean due to the recycling use of inexpensive production raw materials and by-products. becomes.

An object of the present invention is to provide a method for producing silica with higher purity and various physical properties than crude silica at low cost.

Another object of the present invention is to provide a method for producing ammonium silicofluoride with high purity.

[Means for solving the invention]

The present invention involves reacting crude silica with ammonium fluoride and/or acidic ammonium fluoride in an aqueous medium to obtain ammonium fluorosilicate, and removing unreacted silica and impurities from the ammonium fluorosilicate solution in the reaction mixture. The present invention relates to a method for producing high-purity silica, which comprises reacting ammonium silicofluoride with ammonia in an aqueous medium to produce silica after solid-liquid separation. The present invention also provides ammonium fluorosilicate by reacting crude silica and ammonium fluoride and/or acidic ammonium fluoride and an acid component in an aqueous medium, and the ammonium fluorosilicate solution in the reaction mixture and the untreated ammonium fluoride silicate. After solid-liquid separation of the reacted silica and impurities, ammonium silicofluoride was added in an aqueous medium.
The present invention relates to a method for producing high-purity silica, which is characterized by producing silica by reacting with ammonia. Furthermore, the present invention
The present invention relates to a method for separating and refining ammonium fluorosilicate obtained in the first reaction step of this high-purity silica production process to produce high-purity frozen ammonium fluorosilicate.

The raw material crude silica used in the present invention refers to silica containing impurities (anhydrous silicic acid, hydrated silicic acid, silicic minerals, silica glass, etc.), compounds containing silica (silicates, etc.), or silica containing silica. It is a mixture. Examples include diatomaceous earth, silica stone, silica sand, rice husk ash, and silicate-containing minerals obtained as natural products. In addition, silica fuyum obtained by collecting dust from waste gas generated during the production of Huekou silicon, fly ash which is a byproduct from coal-fired power plants, blast furnace slag, silica process silica known as synthetic silica, and metallic silicon. , high-temperature combustion method silica of silicon tetrachloride, etc. The higher the silica content of crude silica, the more desirable it is, but it is usually 20% or more, preferably 50% or more, and more preferably 80% or more.

The ammonium fluoride used in the present invention may be a reagent, a powder available as an industrial chemical, or an aqueous solution. It is preferable to use ammonium chloride cyclically. As the aqueous medium, water or an inert organic solvent that does not react with the raw materials and products can also be used. An aqueous solution is preferred for handling.

The above-mentioned reaction between crude silica and ammonium fluoride is usually carried out under heating in an aqueous medium.

The reaction between silica and ammonium fluoride in an aqueous medium is shown by the following reaction formula.

Sio2+6NH4F (NH4)2S i F 6 +2 H20 +4 N
H3↑The amount of ammonium fluoride to be used depends on the reactivity of the crude silica used, but it is sufficient to use an amount sufficient to convert the silica contained in the raw material into silicofluoride. Usually, the molar ratio is 0.5 to 20, preferably 1 to 15, more preferably 2 to 12, relative to Sing in the crude silica. An excess of ammonium fluoride can increase the reaction rate with crude silica.

The reaction temperature varies depending on the pressure during the reaction and is not particularly limited, but is usually 50°C or higher, preferably 70°C or higher. Under normal pressure or reduced pressure, 50 to 110°C is preferable. Reaction pressure This is usually carried out under normal pressure or reduced pressure, but it is also possible to carry out under pressurized conditions while removing by-product ammonia.Normally, by-product ammonia is led out of the system and recovered through a cooler. If necessary, it can be absorbed into an aqueous solution or the like and recovered as ammonia water.This recovered ammonia water can be used as a raw material for the next reaction step.Also,
A method in which by-product ammonia gas is discharged from the reaction system by bubbling an inert gas into the reaction system is also applicable.

The reaction method can be either a batch method or a continuous method, and the reaction time varies depending on the reaction method and reaction conditions, and is not particularly limited, but is usually within 10 minutes to 50 hours, more preferably 1 to 50 hours.
It is 20 hours.

Furthermore, acidic ammonium fluoride can also be used instead of ammonium fluoride.

The reaction formula of silica and acidic ammonium fluoride in an aqueous medium is shown by the following reaction formula.

S102+3NH4・}{l:'2->(NH4)
2S iF 6+2H20 +3NH3↑S102+4
NH4・HF 2 −> (NH4)2S i F
6 +2H20+2N84F Can an industrial chemical be used as the acidic ammonium fluoride? It is also possible to use a deammoniation reaction product (see reaction formula below) obtained by heating and concentrating ammonium fluoride mother liquor in silica production.

2NH. F-1→NH.・HF2+ NH2↑The above reaction requires high-temperature conditions of 100°C or higher to increase the reaction rate, so usually the deammonation reaction rate is kept at about 20 to 80% and the mixture of ammonium fluoride and acidic ammonium fluoride is used. Alternatively, it may be used as a mixed slurry for reaction with crude silica.

Another method for obtaining acidic ammonium fluoride is a method in which ammonium fluoride is deammoniated using a cation exchange resin. That is, as shown below, acidic ammonium fluoride or a mixture of acidic ammonium fluoride and ammonium fluoride is obtained using a sulfonic acid type or carboxylic acid type ion exchange resin, and these are subjected to a reaction with crude silica. I can do it.

2NH. F +R - S 03H NH4・HF2+R-SO3NH. 3NH. F+R-SO3H NH.・HF, 10NH4F+R-SOzNHn (R-S
O. H, cation exchange resin) An acid component may be added to the system in which crude silica and ammonium fluoride are reacted. Acid components include hydrogen fluoride, hydrofluoric acid, hydrogen silicofluoride, hydrosilicic acid, sulfuric acid, hydrogen chloride, hydrochloric acid,
Examples include nitric acid and cation exchange resins. Preferred are hydrogen fluoride, hydrofluoric acid, hydrogen silicofluoride, hydrofluorosilicic acid, and cation exchange resins.

Hydrofluoric acid can be obtained by treating the by-product ammonium fluoride solution, which will be described later, with a cation exchange resin and deammonizing it as shown in the reaction formula below. Ammonium chloride can be recycled and is particularly preferred.

NH4F+R-SO. H HF+R-SO3NH. (R-SO3H; cation exchange resin) The reaction formula of crude silica, ammonium fluoride, and acid in an aqueous medium is shown by the following reaction formula.

In the case of hydrofluoric acid as the acid, S iO 2 + 5 NH 4 F + HF (
NH4)2S iFg +2H20+3NH2↑S i
0 2 + 2 N 8 4 F + 4 8 F (NH
4) 2S i Fa +2 H20When hydrosilicic acid is used as the acid, SiO2+6NH4F+H2SiFs -1→2(NH
4) 2S iF@+2H20+2NH3↑ In case of cation exchange resin as acid Si02+6NH4F+4R-SOsH -1→(N
H4) 2S iFa +4 R SOaNH. +2H
20 In case of sulfuric acid as acid S i02+6NH4F+2H2sO4(NH4)2S
i F s + 2 (NH4)2S o4+ 2
The reaction of H20 crude silica with acidic ammonium fluoride and fluorinated hydric acid is shown by the following formula.

S i02+2NH4・HF2+2HF −-→(NH
．． ) 2S i F6 + 2H20 The amount of acid varies slightly depending on the type of acid, with a molar ratio of 0. 1-6, preferably < +-s 0.
There are 5 to 2. Further, in the case of the above-mentioned reaction which does not produce ammonia, the reaction temperature is usually 100°C or less, and is carried out at 50 to 80°C depending on the crude silica or reaction conditions.

The method of obtaining ammonium fluorosilicate from crude silica described above can also be carried out by combining the above reaction methods.

Next, in the method of the present invention, ammonium silicofluoride obtained by the above method is reacted with ammonia in an aqueous medium,
Before this reaction, ammonium silicofluoride may be separated and purified.

In the separation and purification method, if there is an insoluble impurity in the aqueous medium in which ammonium fluorosilicate is dissolved under heat or at room temperature, this is separated into solid and liquid.

Ammonia may be added to this separated liquid to perform a reaction to obtain silica, but ammonium silifluoride can be further obtained by cooling the mother liquor in which ammonium silifluoride is dissolved or concentrating as necessary. Ammonium silicofluoride with good purity can be obtained by precipitating it as white crystals and filtering it.In order to obtain even higher purity silica, the white crystals of ammonium silicofluoride obtained by the above method are It can also be purified by crystallization, etc. The recrystallization method is the usual method of dissolving it in hot water, filtering it while hot, removing the filter residue, and crystallizing the solid content from the mother liquor. At this time, crystallization of ammonium silicofluoride tends to be more effective in purifying the crystallization under acidic conditions.

The purity of the obtained ammonium silicofluoride varies depending on the crude silica raw material or the reaction conditions, but it usually contains 10% by weight of metal impurities. 6 or less), the metal impurity is 100 to 1000 ppm or less, and in some cases 10 ppm.
Ammonium silicofluoride crystals with a diameter of less than m are obtained. especially,
In the case of crude silica having a metal impurity of 1000 ppm or less, ammonium fluorosilicate crystals having a metal impurity of lO to 100 ppm or less, and in some cases 1 ppm or less can be obtained.

Next, the ammonium silicofluoride obtained in this way is
React with ammonia in an aqueous medium to obtain nonoka.

What is the reaction between ammonium silicofluoride and ammonia? It is shown by the reaction formula.

(NH4)2S i Fa+4NHz+2H20-〉S
i O■+6 NH. F In this reaction, ammonia may be a gas or an aqueous solution. In either case, high purity ammonia gas or ammonia aqueous solution is used.

The reaction temperature is not particularly limited or is usually 0°C to 100°C.
, preferably within the range of room temperature to 80°C.

If it is carried out under pressure, the temperature may exceed 100°C.

The amount of ammonia to ammonium silicofluoride is stoichiometrically 4, but usually the molar ratio is 3 to 10, preferably 4 to 6, and either ammonia or excess is preferred. When adding an ammonia component, it is preferable to feed it continuously or in portions to the reaction system.

The addition time is not particularly limited, but is usually within the range of 5 minutes to 10 hours, more preferably 10 minutes to 5 hours.

It is also possible to prepare the ammonia component in advance and add ammonium silicate, or to add the ammonia component and ammonium silicate at the same time. After the addition of ammonia is completed, an aging reaction may be carried out for 15 minutes to 5 hours.

The produced silica is separated by a conventional solid-liquid separation method.
The high-purity silica of the present invention can be obtained by separating by filtration, centrifugation, etc., washing, and drying. Since the ammonium fluoride produced as a by-product during this solid-liquid separation is dissolved in the mother liquor from which the silica is separated, it is preferable to circulate this mother liquor to the first step for use.

Meanwhile, the separated silica wet cake is washed with pure water. If ammonia or the like remains in the wet cake, add an acid component if necessary to wash it, and then wash it with pure water. This acid component includes hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid,
Examples include inorganic acids such as hydrofluoric acid, hydrofluorosilicic acid, and carbonic acid, various organic acids, and ion exchange resins. Among these, inorganic acids are preferred.

The water and acid used for cleaning are substantially free of impurities (especially metal components)
Use one that does not contain. Note that cleaning with an acid component may be performed by adding an acid to the silica slurry before obtaining the silica wet cake.

Drying methods after washing include hot air drying, vacuum drying, spray drying, and
Applicable to flash drying, fluidized drying, etc. 20 as necessary
Drying and baking at 0°C or higher can also be applied.

In the production method of the present invention, a deammonification reaction proceeds by heating crude silica with ammonium fluoride,
Produces ammonium silicofluoride.

Impurities in crude silica are removed by utilizing the solubility difference between ammonium silicate and ammonium fluorosilicate in an aqueous medium, and high-purity silica is produced by reacting purified ammonium silica fluoride with ammonia in an aqueous medium. You can get it. The purity of the obtained silica varies depending on the raw material crude silica or the reaction conditions, but when crude silica is used, which usually has a metal impurity content of 10% by weight or less, the metal impurity content is 100 to 1000 ppm.
Hereinafter, silica of 10 ppm or less can be obtained depending on the case.

In particular, in the case of crude silica having metal impurities of 1000 ppm or less, silica with metal impurities of 10 to 100 ppm or less, and in some cases ippm or less, can be obtained.

Furthermore, the method of the present invention has the effect of modifying the physical properties of silica. The physical properties of silica can be modified to obtain silica with high activity and good dispersibility, for example, by changing the particle size, particle shape, specific surface area, ignition raw material, and amount of surface silanol groups.

In the method of the present invention, ammonium fluoride, which is produced as a by-product in the reaction of ammonium fluorosilicate and ammonia in an aqueous medium, can be recycled as a raw material for the first reaction, so the cost of raw materials and the cost of processing by-products are lower than in the prior art. It can be reduced. In other words, the method of the present invention does not require the treatment of expensive production raw materials and reaction by-products as in conventional methods, and enables an economical and clean industrial process by using inexpensive production raw materials and recycling by-products. provide. The reaction formulas described above are used to explain the present invention, and the present invention is not limited to these reaction formulas.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Note that 06 in the examples indicates weight %.

The metal impurity content and physical properties of silica were measured as follows.

fil Contains metal impurities! After decomposition with dihydrofluoric acid, a small amount of acid-added solution was subjected to ICP emission analysis.

(2) Specific surface area: Based on the BET method using nitrogen gas.

(3) Average particle diameter: Measured using a laser diffraction particle size distribution analyzer.

(4) Ignition loss: 95 for products heated and dried at 105°C
Weight loss was measured after treatment at 0°C for 1 hour.

(5) Dispersibility in water. The water slurry of IO% silica was shaken and then visually observed.

Good water dispersibility means that it does not settle out immediately after being dispersed in water, whereas poor water dispersibility means that it settles immediately in water.

Further, metal impurities in ammonium silicofluoride were measured by ICP emission spectrometry as described in (1) above for an aqueous solution.

Example 1 Silica fuyum (manufactured by Nippon Heavy Chemical Co., Ltd., trade name) was added as crude silica to a 1 liter Teflon container equipped with a stirring blade and a thermometer.
SF powder, SiO2 content 92.4%) 60g and 30
% ammonium fluoride aqueous solution was added thereto, and the mixture was heated and stirred in an oil bath at 120°C.

As the temperature of the reaction solution rose, distillation of water containing ammonia began, and while the distillate was absorbed into hydrochloric acid water, heating and stirring were continued for 7 hours until the temperature of the reaction solution reached 98°C. During this time, 60 g of ammonia was recovered outside the reaction system.

After cooling to room temperature, the precipitate was filtered and dried to obtain 150 g. The hot water soluble content in this solid content is filtered while hot to remove the filtrate, and recrystallized from the mother liquor to form crystals of ammonium silifluoride.
Obtained 0g.

36 g of ammonium fluorosilicate crystals were dissolved in 384 g of pure water, and 60 g of high-purity ammonia water (manufactured by Nissan Chemical Co., Ltd., 28% concentration) was added at room temperature, and the mixture was allowed to react for 30 minutes to produce silica. This was filtered, washed with water, and dried at 105°C to obtain 11g of silica powder.

The impurity analysis values (%) of the raw material silica fume and the obtained silica powder are shown below.

A1203 Fe203 Raw material 1.5 3.9 Product <0.01 <0.01 Example 2 By the same method as in Example 1, 10I! In a Teflon container, 600 g of diatom ± (trade name, Toa Kasei Co., Ltd., Toa Light, SiO2 content 77.4%) as crude silica and 24%
Add 7,400 g of ammonium fluoride aqueous solution and heat in a 120°C oil bath until the temperature of the reaction solution reaches 98°C.
Heating and stirring were continued for an hour.

During this time, 400 g of ammonia was collected outside the reaction system. The filtrate is removed by hot filtration, and the solid content from the mother liquor is purified by recrystallization to obtain ammonium silifluoride.
550 g of secondary crystals were obtained. Furthermore, 200 g of secondary crystals were obtained.

360 g of primary crystals were dissolved in 2020 g of pure water, and 170 g of gaseous ammonia was introduced over 3 hours at room temperature to generate silica.

Collect the mother liquor by filtering the resulting slurry under pressure? The cake was washed with water and dried at 105°C to obtain 110 g of silica powder.

Impurity analysis values of the raw material diatomaceous earth and the obtained silica powder (
%) is shown below.

A1203 Fe2e3CaO MgO Na2
0 raw materials 1.42 1.30 0.07 0
．． 25 0.42 Product <0.01 <0.1
<0.01 <0.01 <0.01 Example 3 Silica earth (manufactured by Toa Kasei Co., Ltd., trade name: Torlite) was added as crude silica to a 2L Teflon container equipped with a stirring blade and a thermometer.
Pressure filtration mother liquor of the silica production reaction slurry obtained in Example 2 (ammonium fluoride concentration about 18%) 1
Using 600 g, 100 g of crystals containing ammonium fluorosilicate as a main component were obtained in the same manner as in Example 1.

36 g of this crystal was dissolved in pure water, and 17 g of ammonia gas was introduced at room temperature for 25 minutes to generate silica. The resulting reaction slurry was filtered under reduced pressure, the cake was washed with water, and dried at 105°C to obtain 10 g of silica powder with good purity. The impurity analysis values of the raw material diatom and the obtained silica powder are shown below.

A120s FexOs CaO MgO raw material 1.42 1.30 0.07 0.25
Product <0.01 <0.1 <0.01 <
0.01 Example 4 In a 1-liter Teflon container equipped with a stirrer and a thermometer, 65 g of silica silica (manufactured by Shionogi & Co., Ltd., trade name: Carplex 80 Si○2 content 87.5%) and 3
Add 735 g of 0% ammonium fluoride aqueous solution,
The mixture was heated and stirred in an oil bath at °C.

As the temperature of the reaction solution increased, distillation of water containing ammonia began, and heating and stirring were continued for 9 hours until the temperature of the reaction solution reached 98°C. Analysis of the distillate revealed that 57 g of ammonia was recovered outside the reaction system.

Add 354 g of hot water to 264 g of the obtained reaction slurry and add 8
The filter cake was removed by filtration while hot at 0°C, 611 g of the filtrate was allowed to cool to room temperature, and 115 g of moist ammonium fluorosilicate crystals were obtained by centrifugation.

The crystals were dissolved in 565 g of pure water, 192 g of 25% aqueous ammonia was added at room temperature, and the mixture was reacted for 30 minutes to produce silica. This was filtered, washed with water, and dried at 105°C to obtain 36 g of silica powder. The impurity analysis values of the raw material crude silica and the obtained silica powder are shown below.

Metal impurities (ppm) AI Fe Ca Na raw material 143
7 146 50 2324 products 14
．． 2 6.7 0.7 4.0 2% nitric acid was added to the silica reaction slurry obtained in the same manner to adjust the pH to 1.
．． 2, and the impurity content of the silica obtained by filtering and drying is:
AI, Fe. Ca. Both Na contents were 5 ppm or less.

Example 5 In a 5L Teflon container equipped with a stirrer and a thermometer, silica powder (manufactured by Morimura Shoji, trade name: M20Si02) was added as crude silica.
60 g (content 99.8%) and 2680 g of 21045 ammonium fluoride aqueous solution were added, and the mixture was heated and stirred in an oil bath at 140°C.

As the temperature of the reaction solution increased, distillation of water containing ammonia began, and the reaction solution was heated and stirred for 6 hours at a temperature of 100°C. Analysis of the distillate revealed that 41 g of ammonia was recovered outside the reaction system.

After cooling the obtained reaction slurry to room temperature, it was filtered under reduced pressure to remove insoluble matter as a filtrate (20 g recovered as a dry product).
1964 g of filtrate was obtained. After adding 102 g of 25% ammonia water to this solution at room temperature, the mixture was reacted for 1 hour to produce silica. This was filtered, washed with water, and dried at 105°C to obtain 33 g of silica powder. The impurity analysis values, specific surface area, average particle diameter, and ignition loss of the raw material crude silica and the obtained silica powder are shown.

Metal impurities (ppm) AI Fe Ca Na raw material 50
．． 8 19.9 24.7 <1.0 product
<10.0 <10.0 <5.0 <1.0 Specific surface area Average particle size Loss on ignition (m”/g) (μm) (!%) Raw material
< 1 23.0 < 0.2 Product 1
80 11.0 7.0 Example 6 10j with a stirrer and thermometer? In a Teflon container, 420 g of silica sand (manufactured by Kyoritsu Ceramic Materials Co., Ltd., trade name MK Silica, Sin2 content 99.8%) as crude silica, 6480 g of 30% ammonium fluoride aqueous solution, and 46% hydrofluoric acid 3 were placed in a Teflon container.
04g was added thereto, and the mixture was heated and stirred in an oil bath at 140°C.

As the temperature of the reaction solution increased, distillation of water containing ammonia began, and the reaction solution was heated and stirred at a temperature of 101° C. for 10 hours. Analysis of the distillate revealed that 272 g of ammonia was recovered outside the reaction system.

2000 g of hot water was added to 4000 g of the obtained reaction slurry, and filtered while hot at 80° C. to remove 68 g of filtrate. After 5830 g of the obtained filtrate was allowed to cool to room temperature, the precipitated crystals were filtered off to obtain 914 g (wet) of ammonium fluorosilicate. 11g of hot air dried product of 14g of this wet crystal is
It was identified as ammonium silicofluoride by line diffraction. The metal impurity content is AI. ．． FeXCa1Na both 30pp
It was under mJJ. Ammonium silicofluoride crystals 900g
was dissolved in 2136 g of pure water, and 312 g of ammonia gas was introduced over 1 hour at 50°C to produce silica.

The obtained slurry was filtered under reduced pressure to collect 1920 g of filtrate, and the filter cake was washed with water, acid washed with dilute sulfuric acid, washed with water, and dried to obtain 239 g of silica powder. The impurity analysis values and physical property values of the raw material crude silica and the obtained silica powder are shown below.

Metal impurities (ppm) Water-dispersible AI FeCa Raw material 11 11 107 Unproducts 7 5 4 Good specific surface area Average particle size Loss on ignition (m2/g) (μm) (%) Raw material
<1 95 <0.2 product 48
14 7.2 The raw material silica sand immediately precipitates in water, but the silica modified by the method of the present invention did not immediately precipitate after being dispersed in water.

In addition, the contents of ammonia and fluorine components in the filtrate obtained by vacuum filtration are NH. It was 15.0% in terms of F and 15.5% in terms of F.

Example 7 In a 1 liter Teflon container equipped with a stirrer and a thermometer, silica sand (manufactured by Kyoritsu Ceramic Materials Co., Ltd., trade name: MK Silica) was added as crude silica.
60 g (Si02 content: 99.8%) and 740 g of a 30% ammonium fluoride aqueous solution were added, and the mixture was heated and stirred in an oil bath at 140°C.

As the temperature of the reaction solution rose, distillation of water containing ammonia began, and while 541 g of pure water was replenished midway through, the reaction solution was heated and stirred for 18 hours at a temperature of 90 to 104°C. Analysis of the distillate revealed that 57 g of ammonia was recovered outside the reaction system.

327 g of hot water was added to 273 g of the obtained reaction slurry.
Filter while hot at 0°C and filter dregs 1 0. 2 g was removed. 487 g of pure water was added to 513 g of the obtained hot solution, and 68 g of ammonia gas was added to this solution over 2 hours under water cooling.
was introduced to produce silica. Filter this, wash with water, 105
By drying at °C, 50 g of silica powder was obtained. The impurity analysis values and physical property values of the raw material crude silica and the obtained silica powder are shown below.

Metal impurities (ppm) AI Fe Ca Na raw material 1
1 11 107 4 products 5.4
8.1 1.0 0.3 Specific surface area Average particle size Water dispersibility Loss on ignition (m2/g) .
(μm) (%) Raw material <l 95
Not possible <0.2 product 150 15
Good 6.8 Example 8 In a 500 mf reactor equipped with a stirrer and a thermometer, silica silica (manufactured by Shionogi & Co., trade name:
Carbrex 80SiO2 content 87.5a6) 13g
and 30% ammonium fluoride aqueous solution (prepared from 45 g of reagent primary ammonium fluoride manufactured by Kanto Kagaku Co., Ltd. and 2 g of pure water IO)
147 g and 84 g of 70% sulfuric acid were mixed under water cooling. The temperature of the mixture rose from 22°C to 52°C. This mixed solution was heated and stirred in an oil bath at 130°C. The crude silica as a raw material was completely dissolved at 80°C. Heating was continued for 2 hours, and the reaction solution was concentrated while the distillate components were absorbed into 100 g of pure water, and crystals were precipitated. This was cooled to room temperature to obtain 150 g of concentrated slurry. The amount of absorbed liquid of the distillate component was 192 g, the pH of the liquid was 3 to 4, the fluorine component was 7 ppm in terms of F, and no silica was produced even when 25% aqueous ammonia was added. The crystals in the concentrated slurry were filtered under reduced pressure to obtain 69 g of wet crystals. This was purified by recrystallization using hot water to obtain 30 g of ammonium fluorosilicate in a wet state. Dry overnight at 105°C, dry product 25
I got g. This dried product was dissolved in 102 g of pure water, and 97 g of 25% ammonia water was added over 30 minutes under water cooling to generate silica. This was filtered under reduced pressure and washed with pure water, and the obtained silica cake was dried by heating at 105°C to obtain 8 g of silica powder. The impurity analysis value of the obtained silica powder is A
I, Fe, Ca, and Na were all 10 ppm or less.

Example 9 In a 1 liter Teflon container equipped with a stirrer and a thermometer, 127 g of acidic ammonium fluoride (reagent special grade, manufactured by Kanto Kagaku Co., Ltd.),
Add 319 g of pure water and 87 g of 46% hydrofluoric acid, and add NH.
37.9g (7.1% by weight) in terms of F. 122.
A solution containing 7g (23.0% by weight) was prepared.

To this solution, 60 g of silica sand (manufactured by Kyoritsu Ceramic Materials Co., Ltd., trade name: MK Silica, SiO2 content 99.8%) was added as crude silica at room temperature. (No exotherm was observed.) The mixed slurry solution was heated to 72-84°C in an oil bath for 1 hour. The reaction was filtered hot at 75° C. and 55 g was collected as a wet filter cake. The filtrate was allowed to cool to room temperature, and the precipitated crystals were filtered under reduced pressure to obtain 75 g of wet crystals of ammonium fluorosilicate. After drying the wet crystals at 105°C, they were identified as ammonium fluorosilicate by X-ray diffraction.

Further, when metal impurities were analyzed, they were found to be 10 ppm or less.

45 g of the obtained crystals were dissolved in water to make a 10% aqueous solution,
To this was added 170 g of 25% aqueous ammonia at room temperature over 10 minutes, and the mixture was allowed to react for an additional 10 minutes to produce silica. This was filtered under reduced pressure, washed with water, and dried at 105°C to obtain 15 g of primary silica powder. The impurity analysis values and physical property values of the raw material crude silica and the obtained silica powder are shown below.

Metal impurities (ppm) A120+ Fe20* CaO NaO raw material 11 11 107 4 products
1.0 3.0 2.10.3 Specific surface area Average particle size Water dispersibility Loss on ignition (m2/g) (
μm) (%) Raw material <l 95
Not allowed <0.2 product 185 14.
5 Good 7.2 Furthermore, 14 g of silica with good purity was recovered from the solution obtained by washing the filter cake with 200 g of pure water.

Example 10 1500 g of the filtrate obtained by vacuum filtration during silica synthesis recovered in Example 6 (15.0% by weight in terms of NH3, 15% in terms of F)
A 5% by weight solution of ammonium fluoride (approximately 3096%) was deammoniated using a cation exchange resin (trade name Amberlite 120B, manufactured by Organo), and a 10% solution of ammonium fluoride was prepared as a 10% hydrofluoric acid solution. I got g.

800 g of this 1O% hydrofluoric acid solution and the vacuum filtrate (approximately 30% ammonium fluoride solution) collected in Example 6 24
7g was placed in a 10L Teflon container equipped with a stirrer and a thermometer, and silica powder (trade name, manufactured by Morimura Shoji Co., Ltd.) was used as the crude silica.
60 g of M-20 (3iO■ content 99.8%) was added at room temperature. No fever was observed at room temperature. This was heated and stirred at 80-95°C for 1 hour in an oil bath. The resulting reaction slurry was filtered while hot at 80°C, and the filter residue was removed (9 g in weight after drying) and collected. After the filtrate was allowed to cool to room temperature, the precipitated crystals were filtered under reduced pressure and dried at 105°C to obtain 90 g of crystals containing ammonium fluorosilicate as the main component.

45 g of the obtained crystals were dissolved in 355 g of pure water, and 34 g of ammonia gas was introduced thereto over 1 hour while cooling with water to generate silica. This was filtered, washed with water, and dried at 105°C to obtain 14 g of silica powder.

The impurity analysis values of raw material crude silica are AC Fe, Ca, N
a All of them were below 5 ppm.

Example 11 In a 1 liter Teflon container equipped with a stirrer and a thermometer, silica sand (manufactured by Kyoritsu Ceramic Materials Co., Ltd., trade name: MK Silica) was added as crude silica.
26 g of S i0 2 content 99.8%), 397 g of the vacuum filtrate collected in Example 6 (composition equivalent to 30% ammonium fluoride aqueous solution) and 129 g of 8% hydrosilicofluoride acid (manufactured by Hashimoto Kasei Co., Ltd.) were added. (prepared from 40% reagent) and heated and stirred in an oil bath at 140''C.

As the temperature of the reaction solution increased, distillation of water containing ammonia began, and the reaction solution was heated and stirred for 8 hours at a temperature of 95 to 101°C. By analyzing the distillate, 1 3. was removed from the reaction system. 5
g of ammonia was recovered.

266 g of the obtained reaction slurry was treated in the same manner as in Example 6 to obtain 9 g of silica powder. The impurities and physical properties of the raw material crude silica are the same as in Example 6, and the metal impurities, l, Fe, and Ca of the obtained silica are all 10 ppm or less, the specific surface area is 60 m2/g, and the average particle size is 13 μm. , ignition loss7.
It was 0%.

Example 12 In a 0.51 Teflon container equipped with a stirrer and a thermometer, 30 g of silica sand (manufactured by Kyoritsu Ceramic Materials Co., Ltd., trade name: MK Silica, Si02 content 99.8%) as crude silica and 463 g of a 30% ammonium fluoride aqueous solution were added. Then, while heating in an oil bath, the pressure of the reaction system was reduced using a handy aspirator.

The reaction liquid temperature was 80°C and the absolute pressure was 320 mmHg, and the liquid began to boil, and was collected as a distillate from the system through a cooler.
Further, gas components were collected with 10% sulfuric acid, and the mixture was heated and concentrated at a liquid temperature of 77 to 82°C for 4 hours to recover 279 g of a distillate containing 17 g of NH2. 206g of reaction slurry was obtained, to which 294g of pure water was added and filtered while hot at 60°C to filter out unreacted silica and insoluble impurities.

170 g of 25% ammonia water was added to 478 g of the obtained filtrate at 50° C. over 30 minutes to generate silica.

The resulting slurry was filtered, washed with water, and dried at 105°C to obtain 14 g of silica powder. The metal impurities of the obtained silica are
The obtained silica had better physical properties than the raw material silica, with a specific surface area reaction of 35 m2/g and an average particle size of 14 μm, which were different from those of the raw material silica sand.

Claims (16)

[Claims] (1) Ammonium fluorosilicate is obtained by reacting crude silica with ammonium fluoride and/or acidic ammonium fluoride in an aqueous medium, and the ammonium fluorosilicate solution, unreacted silica, and impurities in the reaction mixture are solidified. A method for producing high-purity silica, which comprises, after liquid separation, reacting ammonium silicofluoride with ammonia in an aqueous medium to produce silica. (2) The method for producing high-purity silica according to claim 1, wherein crude silica and ammonium fluoride and/or acidic ammonium fluoride are reacted in an aqueous medium at a temperature of 50° C. or higher. (3) A claim in which ammonium silifluoride, unreacted silica, and impurities in the reaction mixture are separated by solid-liquid separation in a state in which ammonium fluorosilicate is dissolved in an aqueous medium, and then ammonium fluorosilicate is precipitated and separated. Item 1. The method for producing high-purity silica according to item 1. (4) Separation of ammonium silifluoride from unreacted silica and impurities in the reaction mixture is performed by solid-liquid separation in a state where ammonium silifluoride is dissolved in an aqueous medium, and then ammonium silifluoride is precipitated and separated; The method for producing high-purity silica according to claim 1, which comprises recrystallizing. (5) The method for producing high-purity silica according to claim 1, wherein the acidic ammonium fluoride or the mixture of acidic ammonium fluoride and ammonium fluoride is obtained by deammonizing ammonium fluoride with a cation exchange resin. . (6) The method for producing high-purity silica according to claim 1, wherein an acid component is added to the produced silica slurry or a silica cake obtained from the slurry to remove metal impurities and ammonia components. (7) The high-purity silica according to claim 1, wherein the ammonium fluoride produced when silica is obtained by reacting ammonium silicofluoride with ammonia is recycled to the step of reacting crude silica and ammonium fluoride in an aqueous medium. Production method. (8) Ammonium silicofluoride is obtained by reacting crude silica and ammonium fluoride and/or acidic ammonium fluoride and an acid component in an aqueous medium, and the ammonium silicofluoride solution in the reaction mixture and unreacted silica and A method for producing high-purity silica, which comprises, after solid-liquid separation of impurities, reacting ammonium silicofluoride with ammonia in an aqueous medium to produce silica. (9) High purity according to claim 8, wherein the acid component is at least one selected from hydrogen fluoride, hydrofluoric acid, hydrogen silicofluoride, hydrosilicic acid, sulfuric acid, and cation exchange resin. Method for producing silica. (10) The method for producing high-purity silica according to claim 8, wherein the acid component is an aqueous solution obtained by deammonizing ammonium fluoride and/or an acidic ammonium fluoride aqueous solution with a cation exchange resin. (11) A claim in which ammonium silifluoride, unreacted silica, and impurities in the reaction mixture are separated by solid-liquid separation in a state in which ammonium fluorosilicate is dissolved in an aqueous medium, and then ammonium fluorosilicate is precipitated and separated. Item 8. The method for producing high-purity silica according to item 8. (12) Separation of ammonium silifluoride from unreacted silica and impurities in the reaction mixture is performed by solid-liquid separation in a state where ammonium silifluoride is dissolved in an aqueous medium, and then ammonium silifluoride is precipitated and separated; The method for producing high-purity silica according to claim 8, which comprises recrystallizing. (13) The method for producing high-purity silica according to claim 8, wherein the acidic ammonium fluoride or the mixture of acidic ammonium fluoride and ammonium fluoride is obtained by deammonizing ammonium fluoride with a cation exchange resin. . (14) The method for producing high-purity silica according to claim 8, wherein an acid component is added to the produced silica slurry or a silica cake obtained from the slurry to remove metal impurities and ammonia components. (15) The high-purity silica according to claim 8, wherein ammonium fluoride produced when silica is obtained by reacting ammonium silicofluoride and ammonia is recycled to the step of reacting crude silica and ammonium fluoride in an aqueous medium. Production method. (16) Ammonium fluorosilicate is obtained by reacting crude silica with ammonium fluoride and/or acidic ammonium fluoride in an aqueous medium, and the ammonium fluorosilicate solution, unreacted silica, and impurities in the reaction mixture are solidified. A method for producing high-purity ammonium silicofluoride, which is characterized by liquid separation. (17) Ammonium silicofluoride is obtained by reacting crude silica and ammonium fluoride and/or acidic ammonium fluoride and an acid component in an aqueous medium, and the ammonium silicofluoride in the reaction mixture is combined with unreacted silica and impurities. A method for producing high-purity ammonium silicofluoride, characterized by solid-liquid separation of the components.