JPH051207B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Purpose of the Invention [Field of Industrial Application] The present invention is intended to be used as a raw material for producing disilane, which has recently attracted particular attention as a special gas for producing raw materials for silicon-based semiconductors, amorphous silicon, etc. , relates to an extremely useful method for producing silicon hexachloride.

[Conventional technology]

Silicon hexachloride can be thermally decomposed in a hydrogen stream to produce polycrystalline silicon or single crystal silicon, or it can be used to produce polycrystalline silicon or single crystal silicon, which has excellent heat resistance, abrasion resistance, corrosion resistance, etc.
For the production of SiC, Si ₃ N ₄ chemical vapor deposition films or powders,
Furthermore, as it has features not found in conventional silicon chlorides for the synthesis of organosilicon compounds, demand for it can be expected to increase significantly in the future.

The manufacturing method of silicon hexachloride is usually carried out by reacting silicon alloys such as ferrosilicon, calcium silicon, magnesium silicon, etc. or metallic silicon with chlorine at high temperature (U.S. Patent No.
2602728, 2621111).

Conventionally, a fixed bed reactor or a fluidized bed reactor has been used to carry out the above reaction, but since it is a solid-gas reaction that generates an extremely large amount of heat, it is necessary to control the reaction conditions suitable for the production of silicon hexachloride. The process was difficult, and the situation was too unfinished to be carried out on an industrial scale.

That is, if the reaction conditions cannot be controlled to suitable conditions, silicon tetrachloride or higher silicon chloride higher than silicon octachloride will be produced in addition to silicon hexachloride, and the yield of silicon hexachloride will be significantly reduced.

[Problem that the invention seeks to solve]

Conventionally, the reaction between silicon alloy or metallic silicon (hereinafter referred to as silicon raw material) and chlorine was carried out by filling a fixed bed reactor with silicon raw material and then reacting it with chlorine at high temperature. I had the following problem.

(1) Since the reaction is exothermic, temperature distribution occurs within the reactor during the reaction, making it difficult to control the temperature uniformly.

(2) Due to volume expansion due to by-product chlorides such as iron chloride and calcium chloride, which are produced during the reaction, the reaction residue solidifies, making it difficult to remove the reaction residue after the reaction.

(3) The reaction rate of silicon raw material is low.

Therefore, fixed bed reactors have various problems in implementation on an industrial scale, such as the size of the reactor being limited.

Some of the above problems can be improved to some extent by using a fluidized bed reactor. For example, it becomes easier to maintain temperature uniformity. However, even in a fluidized bed reactor, (1) a large gas flow rate is required for fluidization, and a large amount of equipment and utilities are required.

(2) Fine powdered chlorides such as iron chloride and calcium chloride that are produced as by-products flow out of the reactor together with silicon chloride along with the large amount of gas flow required for fluidization, making it difficult to separate them. In addition, the particles cause clogging of pipes, etc.

(3) The reaction rate of chlorine is low, and removal of unreacted substances or by-products requires a large amount of cost.

It had such drawbacks that it could not be said to be industrially suitable.

In view of the above-mentioned problems with fixed bed and fluidized bed reactors, there are problems related to controllability of reaction temperature, handling of residues, and blockage of piping, etc. that occur when producing silicon hexachloride on a large scale. As a result of intensive research to explain the above, the present inventors invented a method for producing silicon hexachloride, which is characterized by using a vibrating reactor when producing silicon hexachloride by reacting a silicon raw material with chlorine. I applied for a patent (Patent application 1986-
151297).

Thereafter, the present inventors completed the present invention as a result of intensive research in order to establish a method that allows easy reaction temperature control, has a high chlorine reaction rate, and does not cause problems with clogging of pipes, etc.

(B) Structure of the invention [Means for solving the problems] The present invention provides a vibratory reactor in which a partition plate is provided in the reaction gas phase when producing silicon hexachloride by reacting a silicon raw material with chlorine. This is a method for producing silicon hexachloride, characterized in that the reaction is carried out using.

The method of the present invention using a vibratory reactor first vibrates the reactor itself at high speed to transmit vibration to the silicon raw material in the reactor, thereby causing movement of the silicon raw materials among themselves.
Mixing is caused, and the gas phase is drawn in under appropriate vibration conditions, creating a fluidized state that includes the generation of bubbles like a normal fluidized bed method, increasing the effective contact area between the silicon raw material and the chlorine in the gas phase, It makes it easier for the reaction to occur.

In addition, from the standpoint of removing a large amount of reaction heat, the flow of the silicon raw material in the method of the present invention allows for good heat transfer between the silicon raw materials or between the silicon raw material and the wall of the cooling medium such as an external jacket. , efficient heat removal can be performed. Therefore, the reaction amount of chlorine can be increased, making it possible to efficiently produce silicon hexachloride.

Furthermore, unlike in the case of a fixed bed reactor, reaction residues do not solidify and there is very little adhesion to the vessel walls. Also, there are no problems caused by the large amounts of gas required for fluidization, as in the case of fluidized bed reactors.

Furthermore, the present invention uses a vibrating reactor provided with a partition plate in the reaction gas phase, so that
This prevents the chlorine supplied to the gas phase from passing through the gas phase of the reaction system and being discharged, promoting the diffusion of chlorine into the silicon raw material, making it easy to appropriately control the reaction temperature, and increasing the reaction rate. This makes it possible to further improve the

That is, in the reaction between the silicon raw material and chlorine, the state of diffusion of chlorine into the silicon raw material layer governs the reactivity. Therefore, in order to increase the reaction rate of chlorine, it is effective to take measures such as increasing the linear velocity of chlorine supply and spraying it onto the silicon raw material layer, but on the other hand, this leads to non-uniformity of the reaction temperature. However, if a vibrating reactor is used as in the present invention and a partition plate is provided in the reaction gas phase, even if the linear velocity of chlorine supply is slowed down, the chlorine reaction rate is high and a more uniform reaction temperature can be maintained. has become clear. Moreover, although the reason for this is not clear, it can significantly reduce the frequency of clogging of the chlorine supply port by metal chloride or fine particles of silicon raw material, which was a problem when using conventional methods or a simple vibration reactor. was confirmed.

[Reaction raw material]

Examples of the silicon alloy, which is one of the silicon raw materials in the present invention, include calcium silicon, magnesium silicon, ferrosilicon, etc., and ferrosilicon is particularly preferable. The silicon content in the silicon alloy is preferably 30% by weight or more, although it depends on the type. If it is less than 30% by weight, alloying elements other than silicon in the silicon alloy will also be chlorinated, so the chlorine consumption rate may become large.

The silicon raw material may be used alone or as a mixture, and may contain other metals such as aluminum and manganese.

It is more preferable to use a silicon alloy because the reaction temperature can be lowered and silicon hexachloride can be obtained in a higher yield.

It is usually preferable to use a silicon raw material in the form of particles, and in the case of large particles, it is preferable to crush them to a suitable particle size before use. Particle size is preferably 5-300
The number of meshes is preferably 20 to 200 meshes. If it exceeds 5 meshes, the reactivity with chlorine may decrease, and if it is less than 300 meshes, it may be entrained in reaction product gas or inert gas supplied to the reaction system, causing blockages in piping, etc. There are cases.

The chlorine used in the present invention is not particularly limited, but it is usually preferable to use well-dried chlorine gas, for example, a cylinder filled product or one passed through a desiccant may be used.

Chlorine may be used alone or diluted with a diluent gas. Any gas that does not react with silicon hexachloride may be used as the diluent gas, such as _N2 ,
Examples include He, Ar, and silicon tetrachloride.

The reaction ratio between the silicon raw material and chlorine is not particularly limited, and the optimal ratio varies depending on the particle size of the silicon raw material, the vibration conditions of the vibratory reactor, the reaction temperature, the partition plate, etc. It is preferably 2 to 50/hr per unit amount (Kg) of silicon raw material present. 2
If the reaction time is less than 50/hr, the reaction time will be too long and it cannot be said to be preferable, and if it exceeds 50/hr, there may be a large amount of unreacted chlorine.

When chlorine is supplied to the reaction system together with diluent gas, the ratio of diluent gas/chlorine gas is preferably in the range of 0 to 5, from the viewpoint of easy control of reaction heat, etc., and usually 1 or less is sufficient.

[Reactor]

The vibrating reactor in which a partition plate is provided in the reaction gas phase of the present invention is composed of a reactor main body, a partition plate, and an oscillation device that vibrates the reactor.

The shape of the reactor main body is not critical as long as it can be equipped with an oscillation device, and for example, it may be vertical or horizontal. The reactor body may be provided with an external jacket for cooling or heating, and may also be provided with fins, coils, etc. inside the reactor to improve heat transfer. Also, it is acceptable if the interior is made up of shelves. The main body of the reactor is usually equipped with a pipe for supplying a silicon raw material and chlorine as reaction raw materials, a pipe for supplying the produced silicon chloride containing silicon hexachloride, and a pipe for discharging the residue after the reaction.

The partition plate is installed in the reaction gas phase inside the reactor body, and its material is not particularly limited as long as it is not attacked by chlorine and can withstand the reaction temperature, but it is usually made of stainless steel, heat-resistant plastic, etc. is used.

The shape of the partition plate may be any shape as long as it can obstruct the flow of air in the gas phase in the reactor and thereby promote the diffusion of chlorine into the silicon raw material, but it may have any shape that does not come into contact with the gas phase. A suitable material is one that is in contact with the inner wall of the reactor and whose shape matches the cross section of the gas phase (cross section taken perpendicular to the direction of air flow; the same applies hereinafter) so that at least the upper part of the gas phase can be closed off. ing. The size of the partition plate should be at least one third of the cross-sectional area of the gas phase (cross-sectional area when cut perpendicular to the direction of airflow) from the top of the reactor, or up to the extent that it touches the silicon raw material layer. It is desirable that the partition plate be able to close the space of the silicon raw material layer, and if the thickness of the silicon raw material layer is large, the size may be such that the gas phase portion is completely closed off, or in other words, the partition plate may be large enough to sink into the silicon raw material layer. In particular, it is desirable to provide a partition plate with a size that is two-thirds of the cross-sectional area of the gas phase section or a size that allows a slight gap with the silicon raw material layer in the vibration state.
If the above-mentioned blockage area is less than one-third, chlorine gas may pass through and be discharged without participating in the reaction.

It is usually desirable to install the partition plate just before the produced gas outlet pipe so that the gas flow in the reaction gas phase is blocked and a gas flow retention area is efficiently formed. Further, when a plurality of chlorine supply ports are provided in the reactor, it is also possible to partition each supply port by providing a partition plate. In this case, more detailed operational management such as changing the amount of chlorine supplied or the temperature of the heating medium becomes possible in accordance with each compartment. Of course, even if there are a plurality of chlorine supply ports, one partition plate may be provided immediately before the reaction product gas outlet piping.

The partition plate can be attached to the reactor body by means such as welding, screwing, or clamping with flanges.

The oscillator can be any device that causes vibration in the reactor, and for example, as described in the Chemical Equipment Handbook (edited by the Chemical Industry Association, published June 15, 1970), page 844, it is industrially unbalanced. Examples include a weight type presentation device, an eccentric shaft, a crank type oscillation device, an electromagnetic type oscillation device, etc.

The vibration conditions of the oscillation device in the reaction of the present invention are:
Gives sufficient vibration to the silicon raw material, makes it in a good fluid state, and enables sufficient control of temperature distribution.
In addition, considering the appropriate equipment cost of the oscillator and the ease of selecting flexible tubes for connecting chlorine, generated gas, and heat medium piping to the reactor, the frequency
400-3600cpm and amplitude 0.5-30mm are preferred;
More preferably, the frequency is 1000 to 1800 cpm and the amplitude is 1 to 10 mm.

The direction of vibration may be linear, circular, elliptical, torsional, or turning, and may be horizontal or vertical.

It is usually desirable for a vibrating reactor to be provided with a vibration isolator for elastic support between the vibrating reactor and the support base.
Vibration isolators include steel coil springs, plate springs, air springs, etc., and rubber tubes, metal and resin bellows type flexible tubes, metal A coiled pipe made of resin or the like is used.

[Reaction method]

A concrete explanation of the reaction method of the present invention is as follows, for example.

A silicon raw material is supplied to a vibrating reactor having a partition plate in the reaction gas phase, and heated to a predetermined temperature while being vibrated by a vibration generator.

The shape, installation position, etc. of the partition plate are preferably as described above.

The amount of silicon raw material supplied to the reactor is not particularly limited, but is preferably 20 to 80% by volume, more preferably 30 to 60% by volume of the reactor. If it is less than 20% by volume, the volumetric efficiency may deteriorate, and if it exceeds 80% by volume, the mixing state of the silicon raw material will deteriorate.
Therefore, temperature control may become difficult.

The vibration conditions for the oscillation device are preferably as described above.

The reaction temperature varies depending on the type of silicon raw material, but
100-500°C is preferred. If it is less than 100°C, the reaction rate of chlorine tends to be low, and if it exceeds 500°C, it may lead to a decrease in the yield of silicon hexachloride. For example, when the silicon raw material is ferrosilicon or calcium silicon, the temperature is 120 to 250℃, and when the silicon material is metal silicon, the temperature is 300℃.
~500°C is preferred.

Methods of controlling the reaction temperature include passing a cooling fluid through the reactor jacket, controlling the temperature of the reactor wall using an electric heater, etc. However, if the method can effectively remove the amount of heat generated by the reaction, then Any method is fine.

After raising the temperature to a predetermined temperature, chlorine is supplied to the reactor together with diluent gas if necessary. The feed rate of chlorine is preferably as described above. The completion of the reaction can be determined by measuring the unreacted chlorine concentration in the waste gas led to the waste gas outlet pipe outside the reaction system, and when the chlorine concentration exceeds a predetermined value, the chlorine All you have to do is stop the supply.

The product containing silicon hexachloride produced by the reaction as described above is usually guided in a gaseous state from the produced gas outlet pipe of the reactor to a cooling pipe, and is obtained as a produced liquid after cooling.

The present invention can be carried out not only in batch reactions but also in continuous reactions. In the case of a continuous reaction, a device for continuously supplying a silicon raw material and a device for continuously discharging reaction residue may be installed in a vibrating reactor. In this case, the flow direction of the silicon raw material and chlorine in the reactor may be cocurrent or countercurrent.

The produced liquid contains silicon tetrachloride, silicon octachloride, etc. in addition to silicon hexachloride, and is purified by distillation or the like to obtain silicon hexachloride.

[Examples and comparative examples]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited by the Examples.

Example A batch-type stainless steel vibratory reactor (horizontal type) 1 of 150 mmφ x 150 mm as shown in Fig. 1 has a diameter of 60 mm from the top of the inside of the reactor body, matching the vertical cross-sectional shape of the inside of the reactor body. A semi-cylindrical partition plate 27 having a length and a thickness of 5 mm was attached just before the generated gas outlet, and Ferrosilicon 4 (silicon content 50% by weight,
40 meshes, average particle size d ⁵⁰ = 230 μm) 35
I prepared Kg. The volume of Ferrosilicon 4 was approximately 50% by volume of the reactor body. From dilution gas supply pipe 9
While N ₂ gas was flowing at 200/hr, the reactor 1 was vibrated by the oscillator 2 at a frequency of 1650 cpm and an amplitude of 3 mm, and heated by the external jacket 10 to 160°C. Then add _N2 gas to 30
/hr, and average chlorine from chlorine supply pipe 8 while controlling the maximum reaction temperature to 160℃.
The reaction was carried out at 350/hr. The diameter of the chlorine supply pipe is 16mmφ, and the line continuity of chlorine is approximately 0.5m/sec.
However, the reaction rate of chlorine was almost 99-99.9%.
The reaction was terminated when the chlorine reaction rate reached 95%.

The total flow rate of chlorine supplied was 28.2 ^m3 . still,
Temperatures were measured at four equally spaced locations in the length direction of the reactor within the silicon raw material layer, and the difference between the highest and lowest temperatures among the four locations was mostly within 5°C.

The generated gas and unreacted gas generated by the reaction are passed through the generated gas outlet pipe 21 to a sedimentation type dust collector 22.
After removing the accompanying fine powder, it was passed through the inner tube of the cooling tube 23 and cooled with a 0° C. refrigerant that communicated with the outer tube, and a product liquid 25 was obtained in the product liquid receiver 24.

The total amount of product liquid obtained was 71.6 kg, and its composition was 57.2% by weight of silicon hexachloride, 41.3% by weight of silicon tetrachloride, and 1.5% by weight of higher chlorides (silicon octachloride or higher). The ferrosilicon reaction residue in reactor 1 was in the form of powder and could be easily taken out.
Analysis of this reaction residue revealed that the main component was ferric chloride (anhydrous), with other unreacted ferrosilicon,
Metal chlorides such as aluminum chloride were present due to impurities in the raw material ferrosilicon.

The amount of unreacted ferrosilicon was 7.5 kg, and the reaction rate of ferrosilicon was 78.6%. Reactor 1
There was almost no residue adhering to the inner wall of the reactor, and no signs of clogging of the chlorine supply pipe 8, the produced gas outlet pipe 21, etc. were observed.

Comparative Example A test was carried out using the reactor shown in Figure 1, without cutting the partition plate, and using the same vibration conditions, ferrosilicon charge amount, chlorine and _N2 gas supply amounts, and maximum reaction temperature as in the example. The response rate is 90-95% from the beginning
It was low. After that, the reaction was stopped once, the diameter of the chlorine supply pipe 8 was replaced with one of 6 mmφ, and the reaction was carried out again under the same conditions except that the linear velocity of chlorine was set to about 3.4 m/sec. The reaction rate of chlorine was 98 ~ Since the improvement was 99.9%, the reaction was continued intermittently. Chlorine reaction rate is 90
%, the reaction was considered complete. However, when the temperature was measured at four locations as in the example, the difference between the highest temperature and the lowest temperature was about 10 to 20°C. Moreover, the chlorine supply pipe port gradually showed a tendency to blockage, and during the reaction,
I had to remove it twice and clean it. A total of ^26.5m3 of chlorine was supplied, and a total of 26.5m3 of produced liquid was produced.
62.5Kg, its composition is silicon hexachloride 54.8% by weight, silicon tetrachloride 43.4% by weight higher chloride (silicon octachloride or higher)
It was 1.8% by weight. Unreacted ferrosilicon
10.3Kg, and the reaction rate of ferrosilicon was 70.5%.

(c) Effects of the invention The present invention chlorinates the silicon raw material while fluidizing it by applying mechanical vibration to the reactor itself.
By increasing the effective contact area with chlorine and installing a partition plate in the gas phase of the reactor, the rate at which chlorine passes through and is discharged is reduced, and at the same time, the diffusion of chlorine into the silicon raw material layer is promoted. This makes it possible to increase the reaction rate of chlorine and to perform a uniform reaction throughout the reactor. Therefore, in combination with the characteristics of the vibration reactor, it synergistically facilitates control of the reaction temperature and reduces the reaction heat. This made it possible to stably operate this reaction on an industrial scale with a large value. In addition, it solves the problem of clogging of piping, especially in chlorine supply pipes due to metal chlorides and fine particles of silicon raw materials, and it is easy to process after the reaction, making it possible to efficiently produce silicon hexachloride with high yield. I can do it.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of an example of an apparatus for carrying out the method of the present invention. DESCRIPTION OF SYMBOLS 1... Reactor, 2... Oscillator (unbalanced weight type), 4... Ferrosilicon, 7... Silicon raw material supply pipe, 8... Chlorine supply pipe, 13... Reaction residue discharge pipe, 21... ...Produced gas outlet pipe, 23...Cooling pipe,
25...Produced liquid, 27...Partition plate.

Claims (1)

[Claims] 1. When producing silicon hexachloride by reacting a silicon alloy or metal silicon with chlorine, the reaction is carried out using a vibrating reactor provided with a partition plate in the reaction gas phase. Production method.