JPH01234317A - Production of silicon tetrachloride - Google Patents

Abstract

PURPOSE:To efficiently obtain silicon tetrachloride, by reacting colloidal silica soln., sodium silicate soln. or powdered material contg. silicon dioxide, and carbon fine powder with chlorine in the presence of potassium compd., as catalyst. CONSTITUTION:The targeted silicon tetrachloride is obtd. by reacting colloidal silica soln., sodium silicate soln. or powdered material contg. silicon dioxide and carbon powder with chlorine in the presence of the catalyst consisting of potassium compd. As the colloidal silica soln. to be used, there are, for example, colloidal silica soln. recovered from hot water contg,. silici acid, synthetic colloidal silica soln., etc., of these solns., the soln. contg. 1-50wt.% SiO2 having 50-800Angstrom particle size, in a solvent such as water, methanol, ethanol, propanol, butanol, acetone can be suitably used. As the potassium compd. used as catalyst, inorg. acid salt (e.g., KHSO4), org. acid salt (e.g., CH3COOK), org. potassium compd. (e.g., C2H5OK), the compd. contg. fluorine atom (e.g. KF, sulfide (e.g., K2S), etc., are exemplified.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing silicon tetrachloride, and more specifically to an efficient production of silicon tetrachloride used in the semiconductor industry, electronic industry, glass industry, etc. Regarding the law.

[Prior Art and Problems to be Solved by the Invention] Silicon tetrachloride is used as a raw material for high-purity silicon for semiconductors, Aerosil, quartz glass, and the like. However, currently industrialized methods for producing silicon tetrachloride use metallic silicon or silicon carbide as starting materials, and there are various problems such as the need for a large amount of energy.

Conventionally known methods for producing silicon tetrachloride include, for example, JP-A-48-66097 and JP-A-50-9595.
In the methods disclosed in Japanese Patent Publication No. 53-6297, etc., silicon tetrachloride is obtained by reacting SiC, FeSi, Si, etc. with chlorine, but these raw materials SiC, FeS
i, Si is an intermediate product obtained from silicon dioxide (silica; 5in2), and therefore the amount of energy required to produce silicon tetrachloride was large.

Also, Japanese Patent Application Laid-Open No. 58-217421, No. 59-500
No. 17, No. 60-65711, etc. disclose a method in which a mixture of silica powder and carbon powder is used as a raw material to form pellets, and the mixture is reacted with chlorine. However, in this method, the reaction temperature is i o o
Since the temperature is substantially 1200 to 1300° C., a special reactor that can withstand this temperature is required, and it is difficult to select the material for the reactor.

In order to lower this reaction temperature, POCffi3 and BCl3. A method of reacting with chlorine in the presence of a catalyst such as As C113 was disclosed in JP-A-61.
This method is disclosed in JP-A-26507, JP-A-5B-55329, and the like. However, in this method, phosphorus and boron from the catalyst are contained in the silicon tetrachloride product.

It could not be used as a semiconductor material because it could be contaminated with arsenic and other substances.

Furthermore, Japanese Patent Application Laid-open No. 58-99116 and 62-170
Publications No. 12 and the like disclose a method of obtaining silicon tetrachloride by chlorinating the carbonization method of organic silicon-containing plants.

However, these methods still have low manufacturing efficiency and lack practicality.

[Means to solve the problem]

Therefore, the present inventors have conducted extensive research in order to solve the above problems of the prior art and develop a method for producing silicon tetrachloride by directly using silica as a starting material and efficiently reacting it with chlorine.

As a result, a colloidal silica solution or a sodium silicate solution is used as a raw material, and this is mixed in advance with fine carbon powder to form a gel, and this gel is dried, or silicon dioxide-containing substance powder is mixed with fine carbon powder. It has been found that the above object can be achieved by reacting the mixture with chlorine in the presence of a specific catalyst.

The present invention was completed based on this knowledge. That is, the present invention provides a method for producing silicon tetrachloride, which is characterized by reacting a colloidal silica solution, a sodium silicate solution, or a silicon dioxide-containing substance powder, and a fine carbon powder with chlorine in the presence of a catalyst consisting of a potassium compound. This is what we provide.

In the method of the invention, the starting material used is either a colloidal silica solution, a sodium silicate solution or a powder of a silicon dioxide-containing substance. Here, various types of colloidal silica solutions can be used. For example, there is a colloidal silica solution recovered from silicic acid-containing hot water, a monometallic colloidal silica solution, and the like. Among these, SiO with a particle size of 50 to 800 particles in a solvent such as water, methanol, ethanol, propatool, butanol, acetone, etc.
Those containing 1 to 50% by weight of z can be suitably used.

Here, colloidal silica recovered from silicic acid-containing hot water is colloidal silica dissolved in hot water gushing out from hot springs or geothermal power generation, etc., and is amorphous ultrafine particles. This property makes it ideal as a starting material for the method of the present invention. In addition, the sodium silicate solution used as another starting material has the formula NagO-n S fog (n = 0.5-4.
It means an aqueous solution of sodium silicate (sodium silicate) represented by 0), and a solution containing 20 to 40% by weight of SiO□ can be suitably used.

In the method of the present invention, when a colloidal silica solution or a sodium silicate solution as described above is used as a starting material, it can be mixed with fine carbon powder as it is and reacted with chlorine; It is preferable to mix this with a gel to form a gel, dry this, and then react with chlorine. Here, the fine carbon powder to be mixed with the colloidal silica solution or the sodium silicate solution may be any carbon source that reacts with the oxygen atoms of the silica source, and specifically carbon black, petroleum coke, and activated carbon.

Powder (fine powder) such as charcoal can be used. The carbon particle size of this fine carbon powder should be such that it can be mixed with the colloidal silica solution or sodium silicate solution in a solvent to form a gel, and that it can be sufficiently contacted with the colloidal silica solution or sodium silicate solution. Good to have. Specifically, a diameter of 74 μm or less (diameter of 200 mesh passes or less), preferably 10 μm or less is used. If the particle size is large, contact with the silica source will be insufficient and the reaction rate will be slow, which is undesirable.

The above-mentioned colloidal silica solution or sodium silicate solution and carbon fine powder generally have a molar ratio of SiO2 and C (C/Si
O□) is 1.0 to 10. Preferably, the ratio is 2.0 to 5.0.

If the molar ratio between the two is less than 1.0, the reaction will not proceed sufficiently, and if this ratio exceeds 10, the carbon particles will be wasted, which is undesirable as it will cause an increase in cost.

In the method of the present invention, when this colloidal silica solution or sodium silicate solution is used as a starting material, these and fine carbon powder are mixed in the presence or absence of a solvent. For this mixing, a colloidal silica solution or a sodium silicate solution and a fine carbon powder may be added to a separately prepared solvent, or a colloidal silica solution or a sodium silicate solution and a fine carbon powder may be mixed. Afterwards, a solvent may be added and mixed by stirring. Furthermore, the colloidal silica solution or the sodium silicate solution and the above-mentioned fine carbon powder may be placed in a stirring tank or the like, and the mixture may be thoroughly stirred and mixed. Further, during or after mixing, the mixture is heated appropriately, for example, when the solvent is water, it is heated to 50 to 100°C, or an alcohol such as methanol or ethanol or hydrochloric acid is added to the mixture.

The mixture of colloidal silica solution or sodium silicate solution and fine carbon powder is gelled by adding an acid such as acetic acid or nitric acid.

In the present invention, it is preferable to further dry this gelled product using a drying means such as hot air. This drying can be carried out at a temperature and for a time that can sufficiently reduce the solvent, preferably at a temperature higher than the boiling point of the solvent, for example, when the solvent is water, about 80 to 150°C.

In the method of the present invention, a powder of a silicon dioxide-containing substance may be used as a starting material, but in this case, it is preferable to thoroughly mix it with fine carbon powder before reacting it with chlorine.

゛Here, the silicon dioxide-containing substance powder specifically includes silica stone, silica flour (a substance containing a large amount of SiOz, which is produced as a by-product during the production of metal silicon, ferrosilicon, etc.),
Fly ash (flue during pulverized coal combustion).

Ash particles containing SiO□ collected from dust collectors, etc.).

Silica sol, silica, silicate carbonized plant (rice).

It is a carbide obtained by carbonizing rice husks and straw of wheat, bamboo leaves, corn leaves and stalks at 300 to 1300'C, and includes SiO□, amorphous carbon, etc.). These silicon dioxide-containing substance powders are
The smaller the particle size is, the more preferable it is, but it is usually preferable to have a particle size of 50 μm or less. In particular, amorphous silica powder with a diameter of 50 μm or less obtained by spray-drying colloidal silica is preferred.

In the present invention, when using the above-mentioned silicon dioxide-containing substance powder, the silicon dioxide-containing substance powder and carbon fine powder are added so that C/SiOz (molar ratio) = 2.0 to 5.0. It is preferable that the powder be thoroughly ground and mixed using a ball mill or the like, so that the particle size of the resulting powder is about 5.0 to 0.1H.

In the method of the present invention, the above-mentioned (1) colloidal silica solution or sodium silicate solution is mixed with fine carbon powder to form a gel, and then dried gel or (1) a mixture of silicon dioxide-containing material powder mixed with fine carbon powder is formed. , a potassium compound as a catalyst is added, and if necessary, especially in the case of a dry gel, it is ground into fine particles using a ball mill or the like. This pulverization uses a device that can peptize the gel.
It is sufficient to carry out the process until a suitable particle size is obtained, for example, 5.0 to 0.1 μm, and the time is about 20 to 300 minutes, and the temperature is room temperature.

Here, the potassium compound used as a catalyst is K
HS O-, K z SO4, K HCO3, K
2 Inorganic acid salts such as CO3゜KNO, CH, C00K
.

Organic acid salts such as KHC, H, O,, C, H, 0, etc., alkoxides and phenoxides such as C2H, OK, C, H, OK, organic potassium compounds such as K Cz Hs, K Cb Hs, etc. ,KF,KHFz,KCl,,
KBr.

Halides such as Kl, K z O, K OH, K
Examples include oxygen-containing metals such as zO3, sulfides such as K2S, cyanides such as KCN, and thiocyanides such as KSON. In addition, hydrides such as KH, nitrides such as KN, KNH2, KBH, etc.

A boride such as KB can also be used.

The particle size of these catalysts is not particularly limited, but is generally 5.
It is preferable to adjust the thickness to 0 μm or less.

These catalysts are usually 0.0% relative to SiO□ in the raw material.
It is added in a proportion of 0.01 to 20% by weight, preferably 0.1 to IO% by weight.

After adding the catalyst, it is also possible to pulverize the raw material mixture together with the raw material mixture, but this is to ensure that the next reaction with chlorine is carried out efficiently. Depending on the means of chlorination, it may be omitted.

In the method of the present invention, silicon tetrachloride is produced by reacting a mixture of the dry gel or silicon dioxide-containing material powder and fine carbon powder prepared as described above with chlorine in the presence of a potassium compound as a catalyst. do. This reaction with chlorine can be carried out under various conditions, but it is generally
The dry gel or mixture is brought into contact with chlorine gas in the presence of potassium at a temperature of ~300°C, preferably 800 to 1000°C. If the reaction temperature is less than 700°C, the reaction rate will be slow, and if the reaction temperature exceeds 1300°C, equipment corrosion due to chlorine will occur, resulting in disadvantages such as the need for special equipment.

The above reaction in the method of the present invention is expressed as SiO□+2C+2C2□→5iC14+2CO, but because colloidal silica and carbon particles are uniformly mixed by gelation, or because silicon dioxide-containing material powder has high activity, chlorine and The efficiency of the reaction is improved, and pure silicon tetrachloride can be easily obtained.

[Examples] Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example I Petroleum coke powder (74 μm or less) was added to a colloidal silica aqueous solution containing 20 wt% of Sing so that C/Si○2 (mole ratio) = 2.5, and methanol was added to the colloidal aqueous solution while stirring and mixing at room temperature. Add 50wL% to
The mixture was heated to 60°C and stirring was continued.

Two to three minutes after the start of stirring, the solution became viscous and began to gel. After stirring for about 30 minutes, add 1 silica-carbon gel.
It was dried with hot air at 10°C for 5 hours.

To this, KH3O was added as a catalyst to SiO□ at 10-
The mixture was added to a concentration of 1%, mixed and crushed in a ball mill for 60 minutes.

1.040g of the sample obtained here was placed in an alumina boat (
The sample was divided into 100 mm (length) x 15 mm (width) x 10 mm (height). At this time, 5iOzl1 degree was 51%.

Quartz glass reaction tube (1, OOOmm (length) x 30m
The above alumina boat was set at a diameter of m (diameter)), the system was evacuated, the inside of the system was purged with argon gas, and the temperature was raised to 900°C while flowing argon gas. Next, switch the argon gas to chlorine gas and
The alumina boat containing the sample was placed at a flow rate of 9
It was moved into the furnace where the temperature reached 00°C.

After reacting under these conditions for 1 hour, the alumina boat was taken out of the furnace, the chlorine gas was replaced with argon gas, and the reactor was cooled and purged. The weight of the sample after the reaction was completed was 0.1788, and the SiO□ concentration was 1.3%.

In addition, the reaction rate was calculated using the following formula based on the weight of the sample before and after the reaction and the Sing concentration in the sample, and it was found to be 99%.
Met.

Sigh reaction rate (%) = (1-by/ax) X
100a: Weight of the sample before the start of the reaction (g) b: Weight of the sample after the start of the reaction (g) X: Sing concentration in the sample before the start of the reaction (wt%) y:
5iCh concentration (wt%) in the sample after the start of the reaction Example 2 Colloidal silica was spray-dried, and the obtained amorphous silica powder (10 to 30 μm) and carbon powder (74a
m or less) was added so that C/SiO (mole ratio) = 2.5, and furthermore, KHSO3 was added as a catalyst so that it was 10 wt% with respect to SiO□, and 60
Mix and disintegrate for minutes.

1.041 g of the obtained sample was fractionated into an alumina boat. At this time, the SiO□ concentration and degree were 54%.

Using the above sample, 1.
Time chlorination was carried out. The weight of the sample after the reaction is 0.2
The weight was 73 g, and the S i Oz'a degree was 29%. Further, the reaction rate calculated from the above formula was 86%.

Example 3 To the silica-carbon gelled product prepared in the same manner as in Example 1, 10 wt% of KOH was added to SiOz as a catalyst.
The mixture was mixed and crushed using a ball mill for 60 minutes.

1.065 g of the obtained sample was fractionated into an alumina boat. The SiO2 concentration at this time was 54%.

Using the above sample, 1.
Time chlorination was carried out. The weight of the sample after the reaction is 0.1
The weight was 87 g, and the S i Oz concentration was 5.6%. Moreover, the reaction rate calculated from the above formula was 98%.

Example 4 A silica-carbon gelled product prepared in the same manner as in Example 1 was added with KH3O as a catalyst at a ratio of 1.0 to SiO2.
Add it to make up wt%, mix for 60 minutes in a ball mill,
Disintegrated.

1.033 g of the obtained sample was fractionated into an alumina boat. The SiO□ concentration at this time was 55%.

Using the above sample, chlorination was carried out under the same conditions and operations as in Example 1. The weight of the sample after the reaction is 0.254g
and the 5iOz concentration was 23%. Further, the reaction rate calculated from the above formula was 90%.

Comparative example 1 Raw material preparation method except that no catalyst was added.

The same operations as in Example 1 were performed for both the chlorination method. The weight of the sample before the start of the reaction was 1.040 g, and the SiO□ concentration was 56%. The weight of the sample after the reaction starts is 0.300
g, and the S i Oz concentration was 28%. Also,
The SiO□ reaction rate determined from the above formula was 85%.

Comparative example 2 Raw material preparation method except that no catalyst was added.

The same operation as in Example 2 was performed for both the chlorination method. The weight of the sample before the start of the reaction was 1.053 g, and the SiO□ concentration was 57%. On the other hand, the weight of the sample after the start of the reaction is 0.
The weight was 478 g, and the SiO□ concentration was 46%. Further, the S i Oz reaction rate determined from the above formula was 63%.

Comparative Example 3 Petroleum coke powder with a particle size of 74 μm or less was added to quartz sand powder with an average particle size of 1.5 μm at a molar ratio of C/SiO□ of 2.
．． 5 and pulverized and mixed in a ball mill for 60 minutes to prepare a sample.

The SiO□ concentration of this sample was 58%. This sample 1
．． 083 g was fractionated into an alumina boat and chlorinated under the same conditions as in Example 1.

The weight of the sample after the reaction was 1.029 g, S,
1 Ozfi degree was 56%. Also, at this time, Si
The reaction rate of n. was 8%.

The results of Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Table 1.

(The following is a blank space) [Effects of the Invention] According to the method of the present invention, not only a colloidal silica solution or a sodium silicate solution but also a powder of a silicon dioxide-containing substance such as an amorphous silica powder is used as a starting material, and the process can be efficiently carried out at low temperatures. Reacts with chlorine to produce silicon tetrachloride in high yield.

As described above, silicon tetrachloride produced by the method of the present invention is inexpensive and of high quality, so it can be used as a raw material for the semiconductor industry, electronic industry, glass industry, etc., or as a raw material for the high added value trichlorosilane and monosilane. It can be effectively used as a raw material.

Patent applicant: Idemitsu Kosan Co., Ltd.

Claims (4)

[Claims] (1) A method for producing silicon tetrachloride, which comprises reacting a colloidal silica solution, a sodium silicate solution, or a silicon dioxide-containing substance powder, and a fine carbon powder with chlorine in the presence of a catalyst made of a potassium compound. (2) Tetrachlorination characterized by mixing a colloidal silica solution or a sodium silicate solution with fine carbon powder to gel it, then drying it, and then reacting it with chlorine in the presence of a catalyst consisting of a potassium compound. Silicon manufacturing method. (3) Mixing silicon dioxide-containing substance powder and carbon fine powder,
A method for producing silicon tetrachloride, which is then reacted with chlorine in the presence of a catalyst made of a potassium compound. (4) Potassium compound as a catalyst is added to SiO in the raw material.
The manufacturing method according to any one of claims 1 to 3, wherein _2 is present in a proportion of 0.01 to 20% by weight.