JPS58217421A - Manufacture of silicon tetrachloride - Google Patents

Abstract

PURPOSE:To improve the yield of silicon tetrachloride, by pulverizing silicon- bearing ore contg. specified amounts of cristobalite phase and tridymite phase and carbon to a specified grain size, mixing them, pelletizing the mixture to form pellets having a specified molar ratio of SiO2/C, and using the pellets as a starting material for silicon-bearing ore and carbon. CONSTITUTION:Silicon-bearing ore is reacted with carbon and chlorine to manufaucture silicon tetrachloride. Silicon-bearing ore consisting of 30-50wt% cristobalite phase, 5-20wt% tridymite phase and the balance amorphous phase is used as said silicon-bearing ore. The silicon-bearing ore and carbon each are pulverized so that the grain size of the resulting powder is made <=100mum and >=90% of the powder has <=50mum grain size, and they are mixed and pelletized to form pellets having 2-3 molar ratio of SiO2/C. The pellets are used as a starting material for said silicon-bearing ore and carbon.

Description

[Detailed description of the invention] The present invention relates to improvements in a method for producing silicon tetrachloride.

Silicon tetrachloride is useful as a raw material for synthesizing fine silica, high-purity synthetic quartz, silicon nitride, silicon tetracarbide, or various organosilicon compounds.

As for the manufacturing method of silicon tetrachloride,
(2) A method of manufacturing by reacting chlorine or hydrogen chloride with ferrosilicon (2) A method of reacting chlorine with silicon carbide,
(3) There are methods such as applying chlorine to a mixture of silica stone and carbon, but method (3) in particular involves adding a pyrogenic substance such as silicon or silicon carbide to it since it is a slightly endothermic reaction. A method has been taken to do so.

Methods (1) and (2) have the drawback of high raw material costs and high costs. Although method (3) has low raw material costs, the reaction temperature is high and the reactivity is low, making it impractical. One of the reasons for this is that the reaction of s 1o 2 /c7tt2 (1) is not an exothermic reaction, and therefore a sufficient temperature cannot be applied to the reaction in a fluidized bed reactor.

Therefore, a method of blending metallic silicon or silicon carbide as an additive for imparting an exothermic reaction has been considered, but like methods (1) and (2), there is no increase in cost. According to the findings of the present inventor, when using a fixed bed or a moving bed for the apparatus in method (3), if the raw material is pelletized, it becomes easier to charge the raw material into the reactor, and the tetrachloride produced by the reaction with chlorine There is an advantage that the gas and JICL collection can be performed completely so that the silicon gas passes through the raw material layer. However, in order to make pellets with a certain degree of strength, binders such as pitch, molasses, polyvinyl alcohol, and carboxymethylcellulose Na salt must be added and molded, resulting in the problem of impurities being mixed into the silicon chloride produced. There is a store entry that will further increase the cost.

Furthermore, if silicon dioxide such as silica flour or Aerosil is used instead of the raw material silica stone, the reactivity is excellent, but it is expensive and has a high bulk specific gravity, so the productivity of pellets is low, so it cannot be used industrially.

The present invention aims to solve these drawbacks, and is a method for producing silicon tetrachloride using silica stone and carbon as raw materials and reacting them with chlorine. A silicon-containing ore having a mineral composition in which the phase is 5 to 20% by weight and the remainder is amorphous and carbon are each adjusted to have a particle size of 100μ or less, and that the particle size of 50μ or less contains 90% by weight or more. , further comprising blending the silica stone and carbon in a molar ratio of 2 to 6, forming pellets in the presence of a binder, filling the pellets into a reactor, and supplying chlorine. This is a method of manufacturing silicon.

The present invention will be explained in more detail below.

In the present invention, a specific silica stone and carbon are blended in a powdery molar ratio of 2 to 3, and then made into pellets using water as a binder, which is then charged into a reactor and co-supplied with chlorine to form silicon tetrachloride. This is the way to do it.

The specific silica stone used in the present invention is cristobalite phase 3
It has an amorphous mineral composition with a tridymite phase of 0 to 50 weight and a tridymite phase of 5 to 20 weight, and is available domestically as opalescent silica.

These silica stones and carbon are each crushed separately to a predetermined particle size, and the particle size is less than 100μ and more than 50μ.
It is preferable to make it into a fine powder so that it contains 90 weight -1 ts or more. This is because the product pulverized in this way has good reactivity.

Carbon is preferably coke, carbon black, etc.
The material is not limited to this, and anthracite or the like can also be used.

The molar ratio of silica stone and carbon is set to 2 to 6, and this is to ensure that silica stone is reduced.

As the binder, known binders can be used, and specific examples include water pitch, molasses, polyl-1-nyl alcohol, carboxymethyl cellulose Na salt, etc. However, substances other than water are preferred since they are contained as impurities in silicon chloride. do not have.

Among these, water is preferred because it is inexpensive, provides the necessary strength when made into pellets, and is convenient to handle.

When water is used as a binder, the amount added is between 5 and 25 parts of the mixture of silica and carbon. Outside these ranges, the strength required for the present invention cannot be obtained.

In order to make pellets from the above-mentioned raw material mixture, pellets can be formed using a molding machine such as a disk pelleter in the presence of a binder, which is strong enough to be used on a moving bed or the like.

By filling the pellets obtained in this way into a reactor, supplying chlorine, and allowing the reaction to occur at a temperature of 1,000 to 1,600°C, silicon tetrachloride can be obtained in a high yield.

The present invention will be further explained below with reference to the drawings, which are longitudinal sectional views of a moving bed reactor used in embodiments of the present invention.

First, as shown in the drawing, the moving bed reactor 1 is a vertical reactor equipped with a heating section equipped with a heater 2 in the center.
Pellets are supplied from a pellet supply lower from the upper side, and a discharge port 6 for reacted raw materials is provided from the lower part.

The sides of the center of the furnace are covered with heat insulating material 4 to prevent heat radiation.

Pellets are filled into such a device and heated to a temperature of 1000 to 13
By heating to 00 DEG C. and supplying chlorine from the chlorine supply port 5, silicon tetrachloride can be obtained at a high yield.

The present invention will be further explained below with reference to Examples.

Examples Commercially available opal silica stones shown in Tables 1 and 2 were crushed to a particle size of 100μ or less and 90% by weight or less of 50μ or less, using a disc pelleter (non-ferrous) using water as a binder. Diameter 10TnA (manufactured by Nipaudal Co., Ltd.)
A pellet of 10 times was prepared and dried at a temperature of 150° for 4 hours.

For comparison, the same procedure was carried out except that the silicon-containing ore was changed. These conditions and results are shown in Table 3.

The strength was measured by dropping naturally from a height of 1 m.
It was checked whether or not the 0 pellets disintegrated.

The particle size of all the powders was adjusted to 100 μm or less, with 90% or more of 50 μm or less, but the synthetic silica was used as it was commercially available.

Table 1 Mineral composition (%) of silicon-containing ores Part 2
Table: Chemical analysis values of silicon-containing ore (related) The above pellets were charged into the moving bed chlorination furnace shown in the drawing and heated to 1.000°.
Chlorine was introduced at a reaction temperature of C to 1,3006 C, and the resulting silicon tetrachloride was condensed in a trap at 10 DEG C., and the amount of electricity used per 11 cg was calculated and used as a measure of reactivity. The results are shown in Table 4.

Table 4 4. Explanation of drawings The drawing is a longitudinal sectional view of an apparatus used in an embodiment of the present invention.

1 is a moving bed reactor, 2 is a heating heater, 3 is a depth sensor, 4 is a heat insulator, 5 is a chlorine supply port, 6 is a reacted raw material outlet,
7 raw material pellet input port and 8 generated gas outlet are shown.

Patent applicant: Denki Kagaku Kogyo Co., Ltd.

Claims (1)

[Claims] Silicon-containing ore, carbon and chlorine are reacted to produce tetrachloride.”
In producing iron, a silicon-containing ore with a cristobalite phase of 30 to 50q6 and a tridymite phase of 5 to 20%, the balance being amorphous, and carbon each having a particle size of 100
1. A method for producing silicon tetrachloride, which comprises using a powder having a particle size of 9o or less of 50μ or less, which is further mixed, and a pellet having a molar ratio of 5102 and C of 2 to 6 is used.