JPH0353247B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing silicon tetrachloride, more specifically, a method for producing silicon tetrachloride in which silicon-containing ore, carbonaceous material, and chlorine are reacted at high temperatures. Regarding improvements.

Silicon tetrachloride is fine silica, high purity synthetic quartz,
It is not only useful as a raw material for the synthesis of silicon nitride or various organic silicon compounds, but is also important as a raw material for silicon for solar cells or silicon for semiconductors.

[Conventional technology]

Conventionally, as a method for producing silicon tetrachloride, for example, the following method is known.

(1) A method of reacting metallic silicon or silicon-iron alloy with chlorine or hydrogen chloride.

(2) A method of reacting silicon carbide with chlorine.

(3) A method of reacting chlorine with a mixture of silica stone and carbonaceous material.

[Problems to be Solved by the Invention] The methods (1) and (2) have the disadvantage that the cost of raw materials is high, which increases the cost. On the other hand, method (3) uses inexpensive silica stone as a silicon source, so (1)
Although it is economically advantageous compared to methods (2) and (2),
The drawbacks were that the reaction rate was slow and the reaction temperature was high. As a way to solve this problem, there is a method of using opal silica as silica stone and pelletizing a mixture of it and carbonaceous material (Japanese Patent Laid-Open No. 58-217421
(No. Publication), equivalent equipment is required to pelletize.

As a result of various studies on how to increase the reaction rate without pelletizing a mixture of opalescent silica stone and carbonaceous material, the present inventor found that it was sufficient to add a small amount of silicon carbide, and completed the present invention. It has been reached.

[Means for solving problems]

That is, in producing silicon tetrachloride by reacting a silicon-containing ore, a carbonaceous material, and chlorine at high temperature, the present invention uses opal silica stone as the silicon-containing ore, and This is a method for producing silicon tetrachloride, characterized in that 1 to 20 parts by weight of silicon carbide is added.

The present invention will be explained in more detail below.

First, to explain the raw materials, opalescent silica stone consists of 30-50% cristobalite phase by weight.
It contains about 5 to 20% of tridymite phase, and the remainder is mainly amorphous. In Japan, for example, there is one produced on Iwo Jima. If a highly amorphous or α-quartz-based material such as silica flower or Sababa silica is used instead of opalescent silica, it will be expensive or the reaction rate to silicon tetrachloride will be low. becomes worse. On the other hand, the carbonaceous material and chlorine may be the same as before, and the carbonaceous material may be coke, etc.
Anthracite, charcoal, carbon black, etc. can be used, and as the chlorine, in addition to chlorine, a chlorine-containing gas such as phosgene can be used. Silicon carbide may be obtained by, for example, reacting coke and silica sand at a high temperature, and does not need to be a special material. Regarding particle size, for opalescent silica and carbonaceous materials, the average particle size is
The thickness is preferably 500μ or less, and preferably 10mm or less for silicon carbide. For pulverization, a pulverizer such as a roll crusher, pulverizer, or vibrating mill is used.

The supply ratio of these raw materials is
The carbon material is stoichiometrically preferably 30 to 60 parts by weight with respect to 100 parts by weight, but the silicon carbide needs to be 1 to 20 parts by weight, preferably 5 to 15 parts by weight. If it is less than 1 part by weight, the silicon tetrachloride concentration in the produced gas will be less than 10% by volume, resulting in a poor reaction rate, and if it is added in excess of 20 parts by weight, there will be no significant improvement in the reaction rate; Since expensive silicon carbide is used, it is uneconomical.
Regarding the amount of chlorine, it is sufficient that it is stoichiometric with the silicon content in the opal silica stone. Specifically, the flow rate is higher than that at which unreacted chlorine is 1% or less, there is no scattering of the mixed powder, and reaction is possible. It is desirable to have a flow rate that does not increase the pressure inside the vessel.

There are no particular limitations on the reactor, and it may be of either a continuous type or a batch type. The continuous type is one in which, for example, a mixture of opalescent silica, carbonaceous material, and silicon carbide is continuously supplied from the upper part, chlorine is continuously supplied from the lower part, and the reaction product gas is taken out from the upper part. The reaction equipment is preferably made of a material that can withstand a high temperature chlorine atmosphere, such as graphite. The reaction temperature is 1000~
Preferably 1600℃, more preferably 1100-1450
It is ℃. If the temperature is less than 1000°C, the reaction rate will not be sufficient, and if it exceeds 1600°C, it will not only become thermally uneconomical but also shorten the life of the reactor.

〔Example〕

Hereinafter, a more specific explanation will be given with reference to Examples and Comparative Examples.

Example Opal silica with an average grain size of 30μ (40% cristobalite phase, 10% tridymite phase, 50% amorphous)
A mixture of 100 parts by weight, 40 parts by weight of coke with an average particle size of 50μ, and 9.1 parts by weight of silicon carbide with an average particle size of 30μ was filled into a reactor with a volume of 400ml, and heated at 1300℃ while supplying chlorine at 80ml per minute from the bottom. Made it react. As a result of gas chromatography analysis of the reaction product gas 5 hours after the start of the reaction, it was found that carbon monoxide by volume.
66.6%, chlorine 0.2%, and silicon tetrachloride 33.2%.

Comparative Example 1 A reaction was carried out in the same manner as in Example except that silicon carbide was removed from the mixed raw materials, and the resulting gas was analyzed. The results were 5.7% carbon monoxide, 85.7% chlorine, 3.8% phosgene, and 4.8% silicon tetrachloride.

Comparative Example 2 A reaction was carried out in the same manner as in Example except that Sababa silica stone (main component α-quartz) having an average particle size of 30 μm was used instead of opal silica stone, and the resulting gas was analyzed. As a result, carbon monoxide was 14.3%, chlorine was 74.2%, phosgene was 2.5%, and silicon tetrachloride was 8.4%.

〔Effect of the invention〕

According to the present invention, the reaction rate is improved and silicon tetrachloride can be produced in high yield without pelletizing opalescent silica stone and carbonaceous material.

Claims (1)

[Claims] 1. When producing silicon tetrachloride by reacting a silicon-containing ore, a carbonaceous material, and chlorine at high temperatures, an opalescent silica stone is used as the silicon-containing ore, and 1 to 100 parts by weight of silicon carbide is added to 100 parts by weight of the opal silica stone. 20
A method for producing silicon tetrachloride, which comprises adding parts by weight.