JPS6217012A - Production of silicon tetrachloride - Google Patents

Abstract

PURPOSE:To produce easily high-purity SiCl4 by allowing the ashes obtained by burning biomass silicate to react with a Cl2-contg. carbon compd. CONSTITUTION:The following mixture is allowed to react with each other at 400-1,100 deg.C in the inert or reducing atmosphere which consists of both the ashes obtained by burning biomass silicate consisting of vegetable contg. silica content such as rice hull and straw or a carbonization-treated product obtained by subjecting the silicic acid biomass to the carbonization treatment and a Cl2-contg. carbon compd. (e.g. CCl4) or a mixture of Cl2 and C-contg. compd. (e.g. CO).

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for producing silicon tetrachloride using silicate biomass such as rice husk and/or rice straw as a raw material.

[Prior art]

Silicon tetrachloride (SiC14) is a substance with a boiling point of 56.8°C, and is a substance that can be purified to ultra-high purity by applying precision distillation technology.

Silicon tetrachloride is trichlorosilane 0ISiC13),
Silane (SiH4), silicon metal (Si), silica (S
It is an extremely useful substance that can be easily converted into various silicon derivatives such as nitride + ion (Si3i4) and silicon carbide (SiC), and is widely used in various fields. For example, among these derivatives, trichlorosilane is a silicone rubber.

Organic silicon materials such as silicone grease, Si metal are used as amorphous silicon raw materials used as semiconductors and solar cell materials, and silica is used as optical fiber materials.

Silicon products used in the electronics industry and silicone used in the organosilicon industry are required to be of high purity, but in order to obtain such high purity silicon products, the following methods have traditionally been used: Such methods are commonly used. That is, silica sand.

Minerals with high silicon purity, such as silica stone and quartz powder, are used as raw materials and are reduced to metallic silicon in the presence of a carbon material as a reducing agent in an electric furnace heated to over 2000℃. Trichlorosilane is produced by reacting silicon with hydrogen chloride, and the trichlorosilane is purified to high purity by rectification. Various silicon products are obtained using this high purity trichlorosilane as a raw material. Furthermore, when obtaining higher purity silicon products such as those used in electronic materials, quartz is used as a silicon raw material.

By the way, it is difficult to stably secure the above-mentioned high-purity silicon raw materials into the future, and therefore, it is necessary to search for, secure, and use new silicon resources that can be stably supplied as resources and provide high-purity silicon products. Although it is necessary to develop a treatment process, no effective process has been found so far.

〔the purpose〕

In view of the above-mentioned circumstances in the field of manufacturing high-purity silicon products, the inventors of the present invention have conducted extensive research into searching for new silicon resources and developing treatment processes. We discovered that straw, bamboo leaves, corn leaves, persimmons, etc. contain large amounts of silica, and that they are extremely effective as silicon resources.As a result of intensive research into the development of a treatment process, we have developed the present invention. It has been completed.

〔composition〕

That is, according to the present invention, silicic acid biomass is used as a raw material,
A method for producing silicon tetrachloride is provided, which comprises subjecting the silicon tetrachloride to a combustion treatment or carbonization treatment, and reacting the resulting treatment product with a chlorine-containing carbon compound or a mixture of chlorine and a carbon-containing compound.

The silicic acid biomass used in the present invention refers to plants containing silica (silicic acid plants) or their leaves, stems, etc., such as rice husks and straw, bamboo leaves, corn leaves, etc. Includes stems, etc.

Conventionally, when chlorinating SiO2 in minerals, carbonaceous substances such as coke and charcoal are mixed with SiO2 powder and subjected to chlorination treatment with pure chlorine gas, but in this case, the surface area of the carbonaceous substance , physical properties such as pore distribution have a major influence on chlorination reactivity. The chlorination treatment temperature used in the present invention is usually about 400 to 1100°C, and the chlorinating agent is a chlorine-containing carbon compound such as carbon tetrachloride, tetrachloroethylene, or phosgene, or chlorine and -carbon oxide, A mixture with a carbon-containing compound such as hydrocarbon, carbon chloride, or chlorinated hydrocarbon is used, and the combination and type thereof are not particularly limited. Therefore, in the reaction system, carbon is not in a solid state but in a gaseous state combined with chlorine or in C01CH
SiO in the sample to be supplied as a gas such as 4
The contact with 2 is better than with solid carbon. Furthermore, the inventors' research has shown that when a conventional solid consisting of a mixture of Si02 and carbon is brought into contact with pure chlorine gas to perform a chlorination reaction, the chlorine does not directly react with Si02, but instead reacts with chlorine. It was found that the carbon reacted to form carbon chloride, which reacted with SiO2.

Based on these facts, in the chlorination reaction of SiO2.

Rather than the conventional method of reacting a mixture of SiO2 and solid carbon with pure chlorine gas, it is possible to combine gaseous chlorine-containing carbon compounds such as chlorine carbide with chlorine, or chlorine, and carbon oxides, hydrocarbons, etc. It has been found that it is more efficient to react the gas mixture with the carbon-containing compound directly with the SiO2.

As a treatment method for silicic acid biomass for chlorination,
Two methods can be adopted: combustion treatment and carbonization treatment. When silicic acid biomass is burned, the carbon is total < Si0
Although not included in 2, in the present invention, a chlorine-containing carbon compound or a mixture of chlorine and a carbon-containing compound is used as a chlorinating agent, so the conversion rate of Si02 to silicon tetrachloride is lower than that of the conventional method. The conversion rate was higher than that obtained when pure chlorine gas was applied to a mixture of SiO2 and carbon.

When performing carbonization treatment on silicic acid biomass.

It is sufficient to perform heat treatment while avoiding complete combustion of silicic acid biomass, and the heat treatment temperature at that time is usually 200 to 1100°C.
It is. In this case, various heat treatment atmospheres can be used, but generally an inert atmosphere or a reducing atmosphere is used, such as nitrogen, argon, hydrogen, -
Carbon oxide, steam, combustion waste gas, etc. can be used alone or in the form of a mixture, and air etc. can be used in low temperature heat treatment. By such carbonization treatment, the organic matter in the silicic acid biomass is carbonized, and a carbonization treatment product containing silicon and carbon components is obtained. In this case, the mixing ratio of silica and carbon can be adjusted by adjusting the carbonization conditions. The silicon content and carbon contained in the carbonization product are derived from substances in the same biological system, so
It can be assumed that the silicon content and carbon are mixed on a molecular level, and moreover, each is an ultrafine particle. Therefore, the carbonized product is considered to be a substance that is highly chlorinated in terms of physical properties such as surface area and pore distribution. From these points, in the case of the present invention,
The chlorination temperature and reaction time can be significantly lower and shorter than in conventional chlorinations using mixtures of SiOz and solid carbon.

In the present invention, silicon tetrachloride is obtained as a gaseous product, but this silicon tetrachloride can be easily made to a high purity by rectification. For example, when rice husk is fluidized at 800℃, the resulting ash composition (
%) is generally SiO2: 96.65, C: 0
．． 96, p2o5: 0.12, K2O and Na20
: 0.80. Cao: 0.46, MnO: 0
．． 10. MgO: 0.08, Fe203: 0.
15, Al2O3: 0.59. Therefore, when rice husk or rice straw is chlorinated, in addition to silicon content, phosphorus and
Iron and aluminum become volatile chlorides, others remain in the reaction residue. Since the obtained volatile chlorides have different boiling points, high purity silicon tetrachloride can be easily separated and recovered by precision distillation.

〔effect〕

Silicic acid biomass such as rice and wheat chaff and straw used as raw materials in the present invention can be obtained every year through rice cultivation, wheat cultivation, etc., unlike silica mineral resources such as silica stone and silica sand. Moreover, since it is agricultural waste, there is no particular problem in supplying the raw material. Furthermore, the silicon tetrachloride obtained by the present invention can be easily made to a high purity by precision distillation. The method can be said to be a silicon product manufacturing technology that will be effective in the future.

〔Example〕 Next, the present invention will be explained in more detail with reference to examples.

Example Rice hulls were carbonized at 900'C for 1 hour in a nitrogen stream to obtain a carbonized product. This contained 37.5% by weight silicon, calculated as SiO2.

Next, this carbonized product was heated in a carbon tetrachloride stream with 6
Chlorination treatment was performed at 00 to 900°C for 5 to 180 minutes.

The conversion rate of silicon to 5iC14 in this chlorination treatment is shown in Table 1 in relation to the reaction temperature. For comparison, Table 2 shows the results of a chlorination experiment of carbonized rice husks using pure chlorine gas as the chlorination agent.

Furthermore, for comparison, chlorination of a commercially available mixture of Si02 and carbon at a weight ratio of 1:1 and SiC was performed using pure chlorine gas, and the results are shown in Tables 3 and 4, respectively. As can be seen from the reaction results shown in Tables 1 to 4,
According to the present invention, by using rice husks as a raw material and converting the silicon contained therein into 5iC14, a higher conversion rate can be obtained than when using other raw materials, and furthermore, it is possible to obtain a higher conversion rate than when using other raw materials. A higher conversion rate can be obtained by using carbon tetrachloride as an agent than by using pure chlorine gas. In addition, when the silica content in rice husks is chlorinated according to the present invention, the reaction is rapid,
With C, a conversion rate comparable to that obtained in 180 minutes can already be obtained in 5 minutes. On the other hand, 900℃,
At the 10 minute condition, the SiO2/carbon mixture was 1% by weight.
and SiC showed a conversion rate of only 10% by weight.

Table-1 Table-2 Table-3 Table-4 Patent applicant: Director of the Agency of Industrial Science and Technology, etc. Designated agent: Director of Hokkaido Industrial Development Testing Institute, Agency of Industrial Science and Technology, Goto Totabe

Claims (2)

[Claims] (1) A method for producing silicon tetrachloride, which comprises burning silicic acid biomass and reacting the obtained ash with a chlorine-containing carbon compound or a mixture of chlorine and a carbon-containing compound at 400 to 1100°C. (2) After carbonizing silicic acid biomass, the resulting carbonized product is reacted with a chlorine-containing carbon compound or a mixture of chlorine and carbon-containing compound at 400 to 1100°C. Production method.