JPS6362452B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing silicon tetrachloride, and more particularly to a method for producing silicon tetrachloride in which pellets containing silicon dioxide, silicon carbide, and carbon as raw materials are reacted with chlorine at high temperature. .

Silicon tetrachloride (SiCl ₄ ) is not only useful as a raw material for the synthesis of fine silica, synthetic quartz, silicon nitride, and various other organic silicon compounds, but also important as a raw material for silicon for solar cells and semiconductors. It is.

Various methods for producing SiCl ₄ have been proposed in the past.

For example, (1) a method of reacting metal 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 carbon.

and so on. Methods (1) and (2) have the disadvantage of high raw material costs, resulting in high costs. Also(3)
Method (2) uses inexpensive silica stone as a silicon source, so it is economically advantageous in terms of raw materials compared to methods (1) and (2), but the reaction rate is very slow and the reaction temperature is high. There were flaws. In addition, as an improvement method of method (3), a fluidized bed reactor contains 49 to 98% by weight of carbon, 1 to 49% by weight of silicon dioxide, and 0.5 to 0.5 to 100% of silicon carbide.
It is present in a proportion of 10% by weight at a temperature of 1454℃ or higher,
It has been proposed to react with chlorine. No. 3,173,758). However, this method also had the drawback of requiring a high temperature of 1454°C or higher to increase the reaction rate.

The present invention solves these drawbacks and uses silicon dioxide as a raw material in a method for producing silicon tetrachloride by reacting silicon dioxide, carbon, and chlorine at high temperatures.
Carbon and silicon carbide, respectively, per 100 parts by weight
This is a method for producing silicon tetrachloride, characterized in that pellets containing 30 to 60 parts by weight and 10 to 20 parts by weight are charged into a reactor and reacted at a temperature of 1000°C or higher.

The present invention will be explained in detail below.

Examples of silicon dioxide include silica stones such as white silica stone, Sababa silica stone, and opal silica stone, and by-product dust and Aerosil, which are discharged when manufacturing silicon-based alloys such as ferrosilicon in an electric furnace.

Examples of carbon include coke, anthracite, charcoal, and carbon black.

The composition ratio of silicon dioxide and carbon in the pellet containing silicon dioxide, carbon and silicon carbide is preferably 30 to 60 parts by weight of carbon per 100 parts by weight of silicon dioxide. Outside this range, the consumption of silicon dioxide and carbon becomes unbalanced and is not appropriate.

Moreover, the composition ratio of silicon dioxide and silicon carbide is preferably 1 to 20 parts by weight of silicon carbide to 100 parts by weight of silicon dioxide. If the amount is less than this, the effect will be small. Moreover, if the number is larger than this, it becomes uneconomical.

Silicon dioxide and carbon are rolled crusher,
It is preferable to use the particles after pulverizing them with a pulverizer such as a pulverizer, a vibration mill, a jet mill, etc., and having an average particle size of 200 μm or less. Furthermore, it is preferable to use silicon carbide after pulverizing it to a size of 500 μm or less.

In this method, powders of silicon dioxide, carbon, and silicon carbide are mixed in a mixer such as a universal mixer, a kneader, or a vibrating mill. To make these raw materials into pellets, a binder may be used without or with a binder, but if a binder is used, the binder may be water, a water-soluble binder such as polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose molasses, etc. ,
A caking agent such as tar or pitch is added, and this is processed using a conventional molding method such as a briquette machine, a compression molding machine such as a disk pelleter, a rolling molding machine such as a pan-shaped granulator, or an extrusion molding machine. Just mold it. The shape of the pellets is preferably one with little irregularity, such as a dice, cylinder, or sphere, and the appropriate size is about 1/2 or less of the narrowest part of the part through which the pellets pass, such as the reactor or supply chute.

As the chlorine, in addition to chlorine, a chlorine-containing gas such as phosgene is used.

Reactors for carrying out these reactions are broadly classified into fixed bed type and fluidized bed type, but in the present invention, fixed bed type is preferred.

In addition, there are methods of carrying out the reaction in a batch type and a continuous type in a fixed bed type reactor, and either method can be applied in the present invention.

In the batch type, there is a method in which only the reactor filled with pellets is reacted, and in a method in which raw materials are replenished according to the consumed raw materials, in the continuous type, pellets are fed from the top and chlorine-containing gas is continuously supplied from the bottom. There are methods such as supplying the reactor directly, discharging the reaction product gas from the upper part, and extracting the reaction residue from the lower part, but it is necessary to have an apparatus to which these methods can be applied.

The reactor material may be any material that can be used in a high-temperature chlorine atmosphere, and specific examples include graphite.

The reaction can be carried out at a temperature of 1000°C or higher, preferably 1100 to 1450°C. If the temperature is less than 1000°C, the reaction rate will not be sufficient, and if it exceeds 1450°C, it will not only become thermally uneconomical but also shorten the life of the furnace.

As explained above, the present invention is a method for producing silicon tetrachloride in which powders of silicon dioxide, carbon, and silicon carbide are pelletized, the pellets are filled into a reactor, and the pellets are reacted at high temperatures.According to the present invention, the reaction rate is This has the effect of producing a product with improved chlorine content, low unreacted chlorine content, and less phosgene generation.

EXAMPLES The present invention will be explained in more detail below with reference to Examples.

Example 1 Silica stone with an average particle size of 30 μm (SiO ₂ content of 90% or more) and coke with an average particle size of 160 μm were mixed so that 100 parts by weight of silica stone and 40 parts by weight of coke were mixed in a vibrating mill for 1 hour and averaged. The particle size was 50μ.

Then, for 100 parts by weight of this pulverized mixture,
22 parts by weight of water and 3.5 parts by weight of silicon carbide of 35 μm or less were added and mixed for 5 minutes in a kneader.

This was made into pellets of 10 mmφ x 10 mm using a disc pelleter, and dried for 24 hours in a dryer at a temperature of 180°C. After drying, this was filled into a reactor with a reaction volume of 5, and chlorine was supplied from the bottom at a rate of 22/min.
The reaction was carried out at 1300°C.

Although the pellets decreased with the reaction, the pellets were fed from the top of the reactor so that the pellet level remained constant.

The reaction continued in this way for 3 days, during which time the amount of unreacted chlorine in the generated gas was less than 0.2%.
No formation of phosgene was observed.

Comparative Example Pellets were made in the same manner as in Example 1, except that silicon carbide was not added. This reaction volume is 5
chlorine was supplied from the bottom at a rate of 22 times per minute, and the reaction was carried out at a temperature of 1300°C.

Although the pellets decreased with the reaction, the pellets were fed from the top of the reactor so that the pellet level remained constant.

The reaction was continued in this manner for 24 hours, during which time the amount of unreacted chlorine in the produced gas was 0.2 to 5.0%, and the amount of phosgene was 1.02 to 11.5%.

Example 2 Example 1 except that silicon carbide was changed to 6.5 parts by weight
I made pellets in the same way. This reaction volume is 5
chlorine was supplied from the bottom at a rate of 35 per minute, and the reaction was carried out at a temperature of 1300°C.

Although the pellet level decreased with the reaction, the pellets were fed from the top of the reactor so that the pellet level remained constant.

In this way, the reaction was continued for 3 days, during which time the unreacted chlorine in the generated gas was less than 0.2%.
No formation of phosgene was observed.

Claims (1)

[Claims] 1. In a method for producing silicon tetrachloride by reacting silicon dioxide, carbon, and chlorine at high temperatures, carbon and silicon carbide are added in amounts of 30 to 60 parts by weight and 1 to 20 parts by weight, respectively, per 100 parts by weight of silicon dioxide as raw materials. Fill the reactor with pellets containing the following proportions and set the temperature to 1000
A method for producing silicon tetrachloride, characterized in that the reaction is carried out at a temperature of ℃ or higher.