JPH01197310A - Production of silicon tetrachloride - Google Patents

Abstract

PURPOSE:To increase the efficiency of the reaction between silica and chlorine and to easily obtain pure silicon tetrachloride, by drying the gel obtd. by mixing carbon powder with colloidal silica soln. or sodium silicate soln. and by reacting with chlorine. CONSTITUTION:The colloidal silica soln. or sodium silicate soln. is mixed with carbon fine powder, gelatinized and reacted with chlorine after drying. As the colloidal silica soln., the colloidal silica soln. recovered from hot water contg. silicic acid, synthetic colloidal silica soln., etc., are exemplified. The sodium silicate soln. means an aq. soln. of sodium silicate having formula Na2 O.nSiO2 (n=0.5-4.0) and the sodium silicate soln. contg. >= about 20-40wt.% SiO2 is pref. As carbon fine powder, fine powder of carbon black, petroleum coke, active carbon, charcoal, etc., can be used. The colloidal silica soln. or sodium silicate soln. and carbon fine powder are generally mixed in the C/SiO2 molar ratio of about 1.0-10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing silicon tetrachloride, in particular, using a colloidal silica solution or a sodium silicate solution as a starting material and gelling it together with fine carbon powder. The present invention relates to a method for efficiently producing silicon tetrachloride by reacting the silicon tetrachloride with chlorine.

[Prior Art and Problems to be Solved by the Invention] Generally, silicon tetrachloride is widely used as a raw material for high-purity silicon for semiconductors, Aerosil, quartz glass, and the like. However, the currently industrialized manufacturing method for silicon tetrachloride is
Metal silicon and silicon carbide are used as starting materials, and there are various problems such as the need for a lot 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, St, etc. with chlorine, but these raw materials SiC, FeS
i, St is an intermediate product obtained from silicon dioxide (silica; Sing), 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, this method requires a reaction temperature of 1000°C.
As mentioned above, since the temperature is substantially 1200 to 1300''C, a special reactor that can withstand this temperature is required, and there is a problem in that it is difficult to select the material of the reactor.

In order to lower this reaction temperature, similar raw materials are used to produce POCl3, BCj'+, AsCj! A method of reacting with chlorine in the presence of a catalyst such as
This is disclosed in Publication No. 7, Publication No. 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 for obtaining silicon tetrachloride by chlorinating carbonized ash of organic silicon-containing plants.

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

[Means for Solving the Problems] Therefore, the present inventor solved the problems of the above-mentioned conventional technology and developed a method for producing silicon tetrachloride by directly using silica as a starting material and efficiently reacting it with chlorine. I did as much research as possible.

As a result, the objective can be achieved by using a colloidal silica solution or a sodium silicate solution as a raw material, mixing this with fine carbon powder in advance to form a gel, and reacting the dried gel with chlorine. They discovered this and completed the present invention.

That is, the present invention provides a method for producing silicon tetrachloride, which is characterized by mixing a Colloid 1 silica solution or a sodium silicate solution with fine carbon powder to gel it, then drying it, and then reacting it with chlorine. It is something to do.

In the method of the present invention, various colloidal silica solutions can be used as the starting material. For example, there is a colloidal silica solution recovered from silicic acid-containing hot water. Moreover, among these, those containing 1 to 50% by weight of 5iOz having a particle size of 50 to 800 in a solvent such as water, methanol, ethanol, propatool, butanol, acetone, etc. 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 Na, O.n S 102 (n = 0.5-4.
0) means an aqueous solution of sodium silicate represented by 2
Those containing 0 to 40% by weight of 5in2 can be suitably used.

On the other hand, 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, specifically carbon black or petroleum coke.

Powder (fine powder) such as activated carbon and 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 SiO□ 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 is more than 10, the carbon particles will be wasted, which is not preferred, as this will cause an increase in cost.

In the method of the present invention, this colloidal silica solution or sodium silicate solution 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. In addition, during or after mixing, the mixture is heated appropriately to a temperature of 50 to 100 % if the solvent is water, for example.
The mixture of the colloidal silica solution or the sodium silicate solution and the fine carbon powder is gelled by heating the mixture with C or adding an alcohol such as methanol or ethanol or an acid such as hydrochloric acid, acetic acid or nitric acid to the mixture.

In the present invention, this gelled material is further dried using a drying means such as hot air. This drying may be carried out at a temperature and 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,
The temperature is preferably about 0 to 150°C.

Furthermore, the dried gel is pulverized into fine particles using a ball mill or the like, if necessary. This pulverization is carried out using equipment capable of peptizing the gel to a suitable particle size, e.g.
It is sufficient to continue until the thickness reaches ~0.1 μm, and the time is 20 to 30 minutes.
Approximately 0 minutes and room temperature is sufficient.

This atomization of the dried gel is for efficiently carrying out the next reaction with chlorine, and may be omitted depending on the state of the gel after drying or the means of chlorination.

In the method of the present invention, silicon tetrachloride is produced by reacting the dry gel prepared as described above with chlorine. This reaction with chlorine can be carried out under various conditions, but
Generally 700-1300°C1 Preferably 800-1
The dry gel is brought into contact with chlorine gas at a temperature of 1,000°C. If the reaction temperature is less than 700°C, the reaction rate will be slow, and if the reaction temperature is lower than 1300°C.
If the amount exceeds 100%, equipment corrosion due to chlorine will occur, resulting in inconveniences such as the need to prepare special equipment.

The above reaction in the method of the present invention is as follows: 510g+2C+2C1□→S i Cfa + 2
Since colloidal silica and carbon particles are uniformly mixed through gelation, the efficiency of the reaction with chlorine is improved, and pure silicon tetrachloride can be easily obtained.

〔Example〕

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

Example 1 In a colloidal silica aqueous solution containing 20 wt% SiO□,
Petroleum coke powder with a particle size of 74 μm or less is C/5i0
2 was added so that the molar ratio of 2 to 2 was 2.5, and while stirring and mixing at room temperature, 50-t% methanol was added to this aqueous colloid solution, and the mixture was heated to 60°C and continued stirring. Two to three minutes after the start of stirring, the solution became viscous and gelation began. After stirring for about 30 minutes, the silica-carbon gelled product was dried with hot air at 110°C for 5 hours.

This was processed using a ball mill (manufactured by Fritsche, P-5 type) for 60 min.
It was crushed (pulverized) for minutes to form fine particles. 5iO of this fine particle
The z concentration was 56%.

Next, 1.040 g of these fine particles were collected as a reaction sample on an alumina board (100 mm (length) x 15 mm (width) x 10 mm (height)), and the alumina board was placed in a quartz glass reaction tube (1000 mm (length) )x3.om
m (inner diameter)). Thereafter, the inside of the system was evacuated and purged with argon gas, and the temperature was raised to 900° C. while flowing argon gas.

After the temperature was raised, the argon gas was switched to chlorine gas, and the alumina board containing the sample was moved into a furnace that had reached 900° C. while flowing chlorine gas at a flow rate of 100 SCCM.

When the gas produced by the reaction was reacted with an aqueous solution of caustic soda, a gel-like solid of S i Oz was produced.

Furthermore, the production of silicon tetrachloride was confirmed by gas chromatography, and no other silicon compounds were detected.

After reacting under these conditions for 1 hour, the alumina board was taken out of the furnace, and chlorine gas was switched to argon gas for cooling and purging.

The weight of the sample after the reaction was 0.300 g, and S i
The O concentration was 28%. Furthermore, the reaction rate was calculated from the following formula based on the weight of the sample before and after the reaction and the Sing concentration in the sample, and was found to be 85%.

Reaction rate (%) of 5i02 = (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: SiO□ concentration in the sample before the start of the reaction (wt%) y:
Sing concentration in sample after reaction start (wt%) Example 2 In Example 1, the molar ratio of C/SiOz was 5.
A sample was prepared in the same manner as in Example 1, except that it was set to 0. The SiO□ concentration of this sample was 41%. Next, 1.054 g of this sample was taken out onto an alumina board and chlorinated under the same conditions as in Example 1.

The weight of the sample after the reaction was 0.420 g, and 5iO
t1 degree was 4.7%. Also, at this time, 5iOt
The reaction rate was 95%.

Example 3 Carbon black with an average particle size of 0.5 μm was stirred and mixed into a colloidal silica aqueous solution so that the molar ratio of C/SiO□ was 2.5, and a sample was prepared in the same manner as in Example 1. did. The S i O concentration of this sample was 61%. 1.037 g of this sample was separated onto an alumina board,
Chlorination was carried out under the same conditions as in Example 1.

The weight of the sample after the reaction was 0.174 g, 5i
Ot1 degree was 24%. Also, at this time S i
O! The reaction rate was 93%.

Example 4 Petroleum coke powder with a particle size of 74 μm or less was added to water glass (sodium silicate aqueous solution) containing 30 wt% SiO□.
/SiO2 was added so that the molar ratio was 2.5, and 30 ppm of an anionic surfactant was added to make the petroleum coke powder and water compatible.

While stirring the mixture at room temperature, an equivalent amount of hydrochloric acid to neutralize the sodium ions was added to form a gel. After washing this gelled product with water, it was dried with hot air at 110°C for 5 hours.
It was crushed in a ball mill for 60 minutes in the same manner as in Example 1, and used as a sample. The S i Oz concentration of this sample was 53%.

1.035 g of this sample was taken out onto an alumina board and chlorinated under the same conditions as in Example 1.

The weight of the sample after the completion of the reaction was 0.239 g, and the weight of the sio
! The concentration was 36%. Further, the Stow reaction rate at this time was 84%.

Example 5 A sample was prepared under the same conditions as in Example 4, except that the molar ratio of C/SiO□ was set to 5.0.

The SiO□ concentration of this sample was 37%. This sample 1
．． 017 g was taken out onto an alumina board and chlorinated under the same conditions as in Example 1.

The weight of the sample after the completion of the reaction was 0.388 g, and the weight of the sample was 0.388 g.
□Concentration was 7%. Further, the reaction rate of SiO□ at this time was 93%.

Comparative Example 1 A colloidal silica aqueous solution was spray-dried, and the resulting powder was ground in a ball mill for 20 minutes. The average particle size of this silica powder was about 1.0 μm.

Petroleum coke powder with a particle size of 74 μm or less was added to this silica powder so that the molar ratio of C/SiO2 was 2.5, and the mixture was pulverized and mixed in the ball mill for 60 minutes to prepare a sample. The SiO□ concentration of this sample was 57%. 1.053 g of this sample was taken out on an alumina board and used as Example 1.
Chlorinated under the same conditions.

The weight of the sample after the completion of the reaction was 0.478 g, and S i
The O concentration was 46%. Also, at this time S i
The reaction rate of Oz was 63%.

Comparative Example 2 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 so that the molar ratio of C/SiO□ was 2.5, and the mixture was ground and mixed in a ball mill for 60 minutes to prepare a sample. And so.

The Sing concentration of this sample was 58%. This sample 1
．． 083 g was fractionated onto an alumina board and chlorinated under the same conditions as in Example 1.

The weight of the sample after the reaction was 1.029 g, S
The iO concentration was 56%. Also, at this time, Si
The reaction rate of O□ was 8%.

The results of each of the above Examples and Comparative Examples are summarized in Table 1.

〔Effect of the invention〕

According to the method of the present invention, colloidal silica is used as a starting material and is combined with fine carbon powder to form a gel, so that silica and carbon can be mixed uniformly. Since it is reacted with chlorine, chlorination can be efficiently carried out at low temperatures without using a catalyst. Therefore, according to the method of the present invention, high quality silicon tetrachloride containing no impurities can be obtained in high yield.

As described above, the silicon tetrachloride produced by the method of the present invention is of high quality and is therefore used in the semiconductor industry and the electronic industry.

It can be effectively used as a raw material for the glass industry, etc., or as a raw material for trichlorosilane and monosilane, which have higher added value.

Patent applicant: Idemitsu Kosan Co., Ltd.

Claims (1)

[Claims] (1) A method for producing silicon tetrachloride, which comprises mixing a colloidal silica solution or a sodium silicate solution with fine carbon powder to form a gel, then drying this, and then reacting it with chlorine.