JPS62171912A - Production of silicon tetrachloride - Google Patents

Abstract

PURPOSE:To produce silicon tetrachloride in high yield, by chlorinating a mixture of a carbonization product of silicon accumulated biomass with a siliceous raw material. CONSTITUTION:A mixture of a carbonization product of a silicon accumulated biomass, e.g. chaff, rice straw, etc., with a siliceous raw material, e.g. quartzite, etc., is chlorinated. The silicon accumulated biomass means a plant containing silica or parts thereof, e.g. leaves, stems, etc., and includes chaff of rice plant, wheat or barley, etc., leaves of bamboo grass, leaves or stems, etc., of corn or scouring rush. The siliceous raw material means a silicon-containing inorganic material and examples thereof include various kinds of ash containing silicon, e.g. burned ash of the silicon accumulated biomass, quartz sand, etc., in addition to the quartzite. The reaction temperature of the above-mentioned mixture with the chlorine is 400-1,100 deg.C. Any methods for fixed bed, moving bed, etc., may be applied to the reaction.

Description

[Detailed description of the invention] It is.

[Prior art]

Silicon tetrachloride (SiCQ4) is used as a raw material for the synthesis of various organosilicon compounds, as well as fine silica,
It is used as a synthetic raw material for high-purity artificial quartz, silicon nitride, silicon carbide, etc. There are three existing methods for producing silicon tetrachloride:

(1) A method in which silicon tetrachloride is produced as a by-product in the process of producing trichlorosilane by chlorinating metallic silicon powder with HCβ. (2) A method of reacting ferrosilicon, silicon carbide, etc. with chlorine. (3) A method in which a mixture of siliceous raw materials such as silica stone and carbon is reacted with chlorine.

In method (1), silicon tetrachloride is obtained as a by-product during the trichlorosilane manufacturing process, and therefore silicon tetrachloride depends on the amount of trichlorosilane demanded.

Furthermore, in order to produce metallic silicon, which is a raw material, a large amount of electricity is required to reduce silica stone at 2000° C. or higher in an electric furnace, resulting in high raw material costs. Method (2) requires a large amount of electricity to produce ferrosilicon and silicon carbide, so the raw material cost is high. In method (3), the raw material cost is low, but the reactivity of the mixture of silica stone and carbon with chlorine is low, and the present inventors found that among the conventional techniques for producing silicon tetrachloride, the raw material cost is low. In an inexpensive method of chlorinating a mixture of silica stone and carbon, ash etc. obtained after combustion treatment of silica stone and silicon-accumulating biomass are added to the treated product obtained by carbonization treatment in a professional atmosphere. The inventors have discovered that silicon tetrachloride can be produced in high yield by mixing appropriate amounts of siliceous raw materials and chlorinating the mixture, and have completed the present invention.

The silicon-accumulating biomass used in the present invention refers to plants containing silica (silicon-accumulating plants), or their leaves, stems, etc. Includes leaves and stems. In addition, siliceous raw materials refer to inorganic substances containing silicon, including silica and various ash containing silicon, such as combustion ash of silicon-accumulating biomass.

Examples include silica sand.

Conventionally, when chlorinating SiOZ in silicic raw materials, carbonaceous substances such as coke and charcoal are mixed with powder of silicic raw materials and subjected to chlorination treatment with chlorine gas, but in this case, Physical properties such as surface area and pore distribution of carbonaceous materials,
Furthermore, chemical properties such as chemical adsorption (chemical reactivity) between this carbonaceous material and chlorine have a large influence on chlorination reactivity. The inventors used conventional methods. As a result of using a carbonized product obtained by carbonizing silicon-accumulated biomass in an inert gas atmosphere instead of carbonaceous substances such as coke and charcoal, , %Si from Si02 to 5iCQ4
02 is included. The present inventors found that when this ash was mixed with the carbonization product of silicon-integrated biomass and subjected to a chlorination reaction in the same way as the natural mineral silica stone, when other carbonaceous materials were used -3= It was also found that the conversion rate to SiCρ4 was dramatically improved.

Carbonized carbon is preferred.

The silicic acid content and carbon content in the carbide of silicon-accumulating biomass vary depending on the raw material used, but in the case of rice husk, the silicic acid content (SiO□) is 30 to 50% by weight, and the carbon content (C) is 30 to 50% by weight. The carbon content is 50 to 70% by weight, and the carbon content exists in a highly active state for the chlorination reaction.

In the siliceous raw material that is chlorinated in the presence of carbide of the silicon-integrated biomass, the SiO2 contained therein
The forms are amorphous, cristobalite, tridymite,
Although quartz may be used, amorphous Si02 is preferable.

When ash is obtained by burning silicon-integrated biomass, the combustion temperature is in the range of 500 to 1100°C, and any combustion type may be used, such as a fluidized bed or a fixed chamber bed. In high-temperature combustion, Si02 in the ash crystallizes, so it is preferable to
Temperatures between 00°C and less than 900°C are optimal.

The method of mixing the carbide of silicon-integrated biomass and the silicic raw material may be wet or dry, and any method can be applied.

The reaction temperature of the above mixture and chlorine is 400 to 1100
℃, preferably 600 to 1000℃ is optimum. In addition, the reaction can be carried out in either fixed bed or fluidized bed, and external heating may be used, but by using an appropriate amount of treatment, the heat generated by the chlorination reaction can be utilized, and the reaction temperature is easy to control.

The chlorine gas used in the present invention may be pure chlorine or chlorine diluted with an inert gas containing no oxygen.

Second, it is silicon-integrated biomass.
Rice husks, rice straw, etc. are waste materials, and since they can be used effectively, silicon tetrachloride can be produced economically.

〔Example〕

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

Example 1 Put 1 g of rice husks into an alumina porcelain bowl 1, with an inner diameter of 3
Heat treatment was carried out in a nitrogen stream in a horizontal electric furnace equipped with a c+n quartz reaction tube. The inside of the reaction tube was sufficiently replaced with nitrogen gas, and then flowed at ffoom Q /mj,n,
The temperature was raised to 700°C at a heating rate of 13.3°C/rn i,n and held for 2 hours to obtain 386 mg of carbide.

This carbide contained 45.2 wt% of SiO2. Next, using the same reactor, 1 g of rice husks was burned in air at 800° C. for 1 hour to obtain white ash. SiO2 in this ash was 95.8 wt%. The following two carbides and ash were ground to 100 mesh in an alumina mortar, and then thoroughly mixed in equal weight portions in an alumina mortar. 54.3 mg of the obtained mixture (Si02 content: 70.0%) was accurately weighed, filled into a quartz glass basket, and placed in a quartz spring thermobalance. This mixture was heated to 900° C. and held in argon gas, then the argon gas was changed to chlorine gas, and the mixture was held in chlorine gas for 1 hour, and the thermogravimetric change during that time was measured. In this case, the flow rates of argon gas and chlorine gas were 1.00++Ω/mj.

After 1 hour of reaction, the chlorine gas was immediately replaced with argon gas and the temperature was lowered. The sample weight after reaction was 1.6.9 mg. The amount of carbon in the sample after reaction was measured by the weight loss due to red heat in air, and the amount of SiOZ was measured by the weight loss due to reaction with HF, and the reaction rate was calculated using the following formula: B: Sj in the sample after reaction,
02 weight The production of SjCΩ4 was confirmed by blowing the gas at the outlet of the thermobalance into water to produce Sj,02 gel.

As a result of the above, the conversion rate of SiO2 to 5jCQ4 in the sample was 65.9%.

Comparative Examples 1 to 3 Next, chlorination experiments were conducted using only the carbide shown in Example 1 and only the ash. The procedure is the same as in Example 1. Also,
Commercially available activated carbon (110°C1) with a surface area of 1220♂/g was added to the ash.
The chlorination experiment was also performed on a sample (Sj02 content: 49.0 wt%) in which equal weights of Sj02 (vacuum dried for 24 hours) were mixed.
%Met.

In addition, 5iCQ4 of SiO2 contained in the rice husk ash of the equal weight mixture of rice husk carbide and rice husk ash in Example 1
The conversion rate was found to be 63.1%. This conversion rate is higher than the conversion rate (32.6%) when activated carbon is used as the carbon material, and the catalytic effect of rice husk charcoal when chlorinating siliceous raw materials is clear. be.

Example 2 Next, instead of rice husk ash, purity 97.7% and particle size 1
A chlorination experiment was conducted using natural silica sand of 00 megh or less. The experimental method was the same as in Example 1.

The conversion rate of SiO,2 to 5iCQ4 in natural silica sand alone and in a mixture of equal amounts of natural silica sand and activated carbon is both 0%.
However, in an equal weight mixture of natural silica sand and rice husk carbide, it was 27.9%, and of this, Sj in the natural silica
The conversion rate of o2 to Sj and CQ4 was 5.7%.

From this value, it is clear that rice husk carbide exhibits a catalytic effect on the chlorination reaction of siliceous raw materials.

Next, the above experimental results are summarized in the following table.

Procedural amendment (spontaneous) February 21, 1985 Director-General of Nango Agency Uga Renbu Tono 1, Indication of the case Patent application No. 014592 of 1985
No. 2, Title of the invention Process for producing silicon tetrachloride 3, Relationship to the case of the person making the amendment Patent applicant address 1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo Name (1)
14) D eyewear - etc. 8, Correction details Page 8, line 18 1 Reaction rate = □X100 (%)''.

Claims (1)

[Claims] (1) A method for producing silicon tetrachloride, which comprises chlorinating a mixture of a carbonization product of silicon-integrated biomass and a siliceous raw material.