JPS59195519A - Manufacture of hexachlorodisilane - Google Patents

Abstract

PURPOSE:To manufacture hexachlorodisilane (Si2Cl6) in high yield by cooling and condensing a mixed gas of polychlorosilane obtained by chlorination of a powdered alloy contg. Si etc. with gaseous Cl, and separating by distillation. CONSTITUTION:A mixed gas having 3-70mol% concn. obtained by mixing gaseous Cl C and an inert gas I such as He, Ne, Ar, and Xe is supplied into a chlorination reactor 10 contg. a finely powdered Si alloy, such as Ca-Si, Mg-Si, and Fe-Si, or metallic Si, having 5-300 meshes, and gaseous Si2Cl6, mixed with SiCl4, octachlorotrisilane, and decachlorotetrasilane, is obtained by a solid-gas reaction by heating at 130-600 deg.C. Then the mixed gas is introduced into a condenser 50 to cool, condense, and liquefy, and then introduced into a distillation tower 70. The SiCl4 and Si2Cl6 are taken out separately as distillates from the top of the tower, and the higher chlorides are introduced into a cracker 90 from the bottom of the tower for cracking higher b.p. fractions, reacted therein with Cl, and converted into SiCl4 and Si2Cl6, which are recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hexachlorodisilane by chlorinating silicon or silicon alloys.

In recent years, with the development of the electro-distribution industry, the demand for silicon for semiconductors such as polycrystalline silicon or amorphous silicon has increased rapidly.

Polychlorosilane 5inC12n represented by formula (1)
-1-2 (n≧2) (1) has recently become particularly important as a raw material for producing silicon for semiconductors.

Of course, these can be thermally decomposed as they are to produce amorphous silicon, etc. (Belgium Patent Specification No. 889)
No. 523) and further reduced to a polysilane represented by formula (II), 5 inHzn+z (n≧2
') (If) It is common to thermally decompose this to produce silicon for semiconductors.

Therefore, polysilanes, especially disilane Si2. H6 is monosilane SiH4 when forming a shear amorphous silicon film by thermal decomposition or glow discharge decomposition.
The film formed on the substrate has advantages such as a much higher deposition rate and excellent electrical properties compared to the previous method, and it will be used as a raw material for semiconductors for solar cells and photosensitive drums in the future. A significant increase in demand is expected (Japanese Unexamined Patent Publication No. 83929/1983).

The method for producing hexachlorodisilane itself is publicly known, and usually involves chlorinating particles of an alloy of metal and silicon, such as calcium silicon, magnesium silicon, or ferrosilicon, at high temperatures, or chlorinating silicon particles themselves at high temperatures. (U.S. Patent No. 260)
No. 2728, No. 2621111).

However, in this case, it is impossible to selectively produce only hexachlorodisilane, which is the target product, and usually a considerable amount of silicon tetrachloride (
Avoid producing a significant amount of by-products such as n=1 in the general formula (+), octachlorotrisilane (also n=3), and higher chlorides (hereinafter, those with n≧3 are simply referred to as higher chlorides). I couldn't. That is, the yield of hexachlorodisilane and the by-product rate of silicon tetrachloride and higher chlorides are determined by the chlorination reaction temperature, the chlorine gas concentration in the reactor, the reaction time (in the case of continuous reaction, reaction contact time or residence time), Although it can vary depending on various factors such as the reaction type (fluidized bed or fixed bed), under normal conditions the yield of hexachlorodisilane based on silicon (number of moles of silicon in the hexachlorodisilane produced * 100/ The number of moles of silicon charged was about 25 to 35 at most.

Of the above factors, the two factors that have the greatest effect on the yield are the chlorination reaction temperature and chlorine gas concentration. The by-product rate of silicon (n = 1) is high, and conversely, if this is lowered, the by-product rate of higher chlorides (n≧3.) is high, and in any case, hexachlorodisilane (n = It was difficult to significantly increase only the selectivity of 2).

In particular, the production of a large amount of higher chlorides higher than octachlorotrisilane as a by-product not only reduces the yield of hexachlorodisilane, but also makes disposal difficult and impairs operational safety, so it is extremely important. (These higher chlorides easily form white solids that can ignite on impact in the presence of water.)

The present invention has been made in view of these points, and includes:
The first objective is to provide a method for producing hexachlorosifuran that produces hexachlorosifurane in high yield.

In addition, the second purpose is that it is difficult to handle and
An object of the present invention is to provide a method for producing hexachlorosifuran in which the amount of by-product waste of higher chlorides with n≧3, which poses many safety problems, is reduced to a large dJ.

Other objects of the invention will become apparent from the description below.

The above object of the present invention is to chlorinate particles of an alloy of metal and silicon such as calcium silicon, magnesium silicon, or ferrosilicon at a high temperature, or to chlorinate the silicon particles themselves at a high temperature to obtain the formula (1). Polychlorosilane mixed gas (produced gas) expressed by the % formula % (1)
The product gas is cooled and condensed, and the resulting condensate is distilled to produce silicon tetrachloride (n = i), hexachlorodisilane (n = 2) and octachlorotrisilane (n
= 3) The above higher chlorides are separated, and the higher chlorides are reacted with chlorine again to convert into silicon tetrachloride and hexachlorodisilane, which is treated in the same manner as the above generated gas to recover hexachlorodisilane. A method for producing hexachlorodisilane, characterized by: ” is achieved.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a flow sheet showing one example of a preferred form for carrying out the present invention.

The chlorination reactor IO can effectively carry out solid-gas reactions, and
Any type, such as a fixed bed type, fluidized bed type, or powder stirring bed type, may be used as long as it is equipped with cooling and/or heating means and the reaction temperature can be controlled.

That is, it may be of a vertical tank type, or of various types such as a horizontal groove type, cylindrical type, or U-shape. In particular, the latter type is more preferable in terms of operability and ease of taking out the solid residue after the reaction is completed. Note that the stirring means provided in the reaction vessel includes propeller type, turbine type, paddle type, spiral type, double spiral type, and Sufu IJ.

- There are different types of stirrers, but the latter two types are
Since it also has a powder transport function, it is particularly suitable for continuous operations in which particles are continuously supplied and continuously extracted.

Metal particles such as Calcium 7 Licon, which are the raw materials charged into the chlorination reactor, usually have a specific gravity of 2 to 5 and a particle size of 5 to 300.
Sand grains of mesh size are preferably used, but they may also be a mixture or a mixture of other metals such as manganese and the like.

In the case of large particles, it is preferable to crush them to a suitable particle size before use.

Chlorine gas C is supplied to the reactor through piping 20,
The chlorine gas C to be sent to the reactor is normally sold in cylinders, etc., and is treated with concentrated sulfuric acid, silica gel, etc., thoroughly dehydrated, and then used as is without further purification. You can. However, in order to keep the reaction rate within an easily controllable range and accurately control the reaction heat, chlorine gas was not used.
Dilute with a gas inert to the reaction system such as helium, neon, argon, xenon, nitrogen, silicon tetrachloride, etc., and have a chlorine content of 1 to 90 mol, preferably 3 to 70 mol%.
It is desirable to use a chlorine-containing gas of about 100%.

The chlorine-containing gas may be supplied to the lower or middle part of the fixed bed according to a conventional method, and the gas may be raised to -J2 in the fixed bed to perform a solid-gas reaction, but the speed of this reaction may is very fast, so for example, if a horizontal reactor is used and the bed height is not very large, gas may be supplied to the surface of the fixed layer and the reaction may be carried out while flowing the gas along the surface of the fixed layer. Hexachlorodisilane is produced at a rate high enough for practical use.

The chlorination reaction temperature is 130° to 400°C, preferably 15°C when a silicon alloy such as calcium silicon is used as the raw material.
The temperature is 0° to 350°C, and when silicon itself is used, the temperature is 300° to 600°C, preferably 300° to 500°C.

After the reaction is completed, the hexachlorodisilane gas generated flows out of the reactor 10 as a high-temperature gas mixed with by-product gases such as silicon tetrachloride, octachlorotrisilane, and decachlorotetrasilane, and is led to the condenser 50 through the pipe 40. , where it is cooled and condensed.

For this purpose, a multi-tubular condenser may be used as the condenser 50, and the generated gas may be cooled and condensed by indirect heat exchange operation through the multi-tubular walls, and more preferably,
The generated gas and a cooling medium (hereinafter referred to as refrigerant) may be brought into direct contact to perform a direct heat exchange operation, thereby cooling and condensing the gas.

In the case of the former indirect heat exchange operation, water, sodium chloride brine, ethylene glycol brine, ammonia, fluorocarbons, methylene chloride, silicone oil, etc. can be used as the refrigerant.

In the case of the latter direct heat exchange operation, the refrigerant used is one that is non-aqueous (or does not contain water) and does not react with the polychlorosilane generated gas and chlorine.

Examples include chlorofluorocarbons, methylene chloride, silicone oil, etc., but particularly preferred are the use of condensed polychlorosilane production liquid itself or silicon tetrachloride itself as a refrigerant.

In the case of the latter direct heat exchange operation, the condensate of the product gas (hereinafter referred to as the product condensate) flows out of the condenser together with the refrigerant, but the product condensate and the refrigerant are not miscible. If there is, the two can be easily separated into two phases and dispersed simply by allowing the effluent to stand still in a settler, and if they are miscible, they can be fractionated by means such as distillation, which will be described later. can.

Note that the temperature of the refrigerant is not particularly limited, but it is preferably at least a temperature at which the produced polychlorosilane does not solidify, and in fact, -50 to 50°C is desirable.

If by-product fine particles such as calcium chloride, iron chloride, etc. (or sublimed particles that can be condensed by cooling) are mixed in the produced condensate as solid substances, they should be separated before the distillation process. It is preferable to remove it. The separation is easily carried out by conventional solid-liquid separation operations such as filtration, centrifugation, sedimentation, and the like.

The produced condensate is sent to a distillation column 70 through a pipe 60, where it is distilled under normal pressure or reduced pressure and separated into the king of higher grade compounds such as silicon tetrachloride, hexachlorodisilane, and octachlorotrisilane. Silicon tetrachloride and hexachlorodisilane are distilled off from the top of the column, and higher chlorides are taken out as bottom residue from the bottom of the column. Note that unreacted chlorine is also distilled out as a low-boiling component, which can be recycled to the reactor 10 through the pipe 80 together with a portion of silicon tetrachloride.

The distillation column may be a packed column filled with Raschig rings, Burl saddle rings, etc., or a bubble cap column with 2, ε
It doesn't matter if it's something special.

The higher chloride discharged from the can can be used in its original size or in an amount of 2 to 20 parts, preferably 5 parts per 1 part of the higher chloride.
It is diluted with ~15 parts of an inert diluent, such as silicon tetrachloride, and sent to the high-boiling decomposer 90 via piping 100. By using a diluent such as silicon tetrachloride, the reaction can be made mild and precisely controlled.

The high boiling point decomposer 90 can be of a tubular type, a stirring type, etc., as long as it can effectively carry out a gas-liquid reaction, is equipped with cooling and/or heating means, and can control the reaction temperature within a desired range. It may be of any type, such as a layered type.

For example, in the case of a tubular reactor, this is an empty column (empty tube).
Alternatively, it is preferable to fill it with a filler such as α-alumina beads, Raschig rings, Burl saddle rings, etc. to make gas-liquid contact more effective. Further, as a modified type of empty tower, it is possible to use a wet wall tower or a bubble tower. In addition, as a mode of gas-liquid contact, both may be brought into contact in cocurrent flow, or may be brought into contact in countercurrent flow.

In the high boiling point decomposer, the higher chlorides react again with chlorine supplied through the pipe 100 (hereinafter referred to as lowering reaction) and are converted into silicon tetrachloride and hexachlorosilane.

The reaction temperature between higher chlorides and chlorine (lowering reaction temperature) is 2
50° to 600°C, preferably 300° to 500°C1
More preferably, the temperature is 350° to 450°C. If the reaction temperature is less than 250°C, the reaction will not proceed effectively, and if it exceeds 600°C, the conversion rate to silicon tetrachloride will increase.
The conversion rate of hexachlorodisilane becomes very small.

The amount of chlorine gas supplied to the higher chloride is 0.1 to 1.5 parts by weight, preferably 0.3 to 0.7 parts by weight per 1 part by weight of the higher chloride.

If this is less than 0.1 part by weight, the lowering reaction will not proceed sufficiently, and if it exceeds 1.5 parts by weight, the conversion rate to silicon tetrachloride will be low and the recovery rate of hexachlorodisilane will decrease, so it is preferable. do not have.

Note that the chlorine gas used for the lowering reaction is in the reactor 10.
It is possible to use a device similar to that introduced in .

That is, chlorine, which is normally sold in cylinders, can be treated with concentrated sulfuric acid, silica gel, etc., sufficiently dehydrated, and then used as is without further purification. However, in order to keep the reaction idle and to keep it within a range that can be easily controlled, and to accurately control the reaction heat, chlorine gas is not used as it is, and reaction systems such as helium, neon, argon, xenochloride, nitrogen, silicon tetrachloride, etc. It is desirable to dilute with an inert gas.

Although the reaction rate of the lowering reaction itself in the present invention is thought to be very high, even when it is a gas-liquid reaction, the solubility of chlorine gas in higher chlorides is considerably high (10
(It is estimated that there is a degree of In addition, in practice, the temperature is 250°C or higher, especially 350°C.
When the lowering reaction is carried out at ~450°C, a considerable portion of the higher chloride is vaporized at this temperature, so the lowering reaction is essentially a reaction between the vaporized higher chloride gas and chlorine gas. It is presumed that most of the reaction takes place as a gas phase reaction.

As described above, silicon tetrachloride and hexachlorodisilane obtained by the lowering reaction flow out of the high-boiling decomposer as a mixture (mixed gas under normal reaction conditions).
This can be treated in the same manner as the produced gas to separate the silicon tetrachloride and hexachlorodisilane, and hexachlorodisilane can be recovered. In a preferred embodiment, as shown in the figure, the mixed gas of silicon tetrachloride and hexachlorodisilane is introduced into the condenser 50 through the pipe 110, and is combined with the generated gas from the reactor 10. It is possible to treat it.

Note that even if the lowered mixed gas still contains silane chlorides higher than hexachlorodisilane, such as octachlorotrisilane and decachlorotetrasilane, which have not been completely lowered, the above-mentioned Through treatment, these higher silane chlorides are condensed in the condenser 50, sent to the distillation station 70 via the piping 60, and circulated as the bottoms to the high boiling point decomposer again. It is then reduced to silicon tetrachloride or hexachlorodisilane.

In addition, high-boiling components such as tar that cannot be lowered by the lowering reaction and some of the above-mentioned octachlorotrisilane (this is a purge component) are discharged from the bottom of the boiling decomposer to the pipe 120. be done.

As described above, the present invention reduces the amount of by-product of silicon tetrachloride by reducing the reaction conditions such as the chlorine gas concentration and reaction temperature for reacting with silicon alloy particles or silicon particles, and also reduces the amount of by-product of silicon tetrachloride. By lowering the higher chlorides using chlorine gas and recovering them as hexachlorodisilane, we can greatly reduce the generation of higher chlorides, which have many handling safety issues, and reduce the amount of hexachlorodisilane, the target component. It has the remarkable effect of being able to greatly increase the yield.

Hereinafter, the present invention will be specifically explained with reference to Examples. In addition,
In the following Examples and Comparative Examples, the purity of polychlorosilane was determined by the gas chromatography method, and the S+ content was determined by the colorimetric method.

Example 1 A 21 separable flask set in an oil bath was used as a chlorination reactor, and commercially available calcium silicon (manufactured by Nippon Heavy Chemical Co., Ltd., 48 to 200 mesohydrium, Si content: 6 durgon) was charged into the flask. The temperature was raised to 200°C, and 250 Nml of dried chlorine gas (purity 98%) was added in argon at a flow rate of 200 Nme/min.
/min was mixed and introduced into the above reactor, and a chlorination reaction was performed for 10 hours.

The produced gas is cooled to 0°C and condensed to produce condensate (1) 1
5 8.5 17 were collected.

The silicon content in the produced condensate was 1.1 mol, which corresponded to a reaction rate of 85% (based on Si atoms).

Next, the produced condensate was distilled under normal pressure using a Widow distillation apparatus to obtain 2.4 g of silicon tetrachloride a (purity 99.4% by weight, 0.3659-mol) and 59.9 g of hexachlorodisilane. 8 17 (purity 988 wt% 0.2 1 8 g-mol, yield 33, 3% (S
(i atomic standard)), the pot residue of higher chloride of 7 or more runs was 35,3.9.

From the top of the high-boiling fraction decomposer (a glass tube with an inner diameter of 13 mm and a length of 55 Q mm filled with α-alumina beads),
400 g of silicon tetrachloride was added to the pot residue of the above higher chloride (35.39 g).
The mixed solution diluted to The residence time of the residual diluted liquid in the column was approximately 7 seconds).The reaction product flows out from the bottom of the decomposer as a gas, so it is cooled to 0°C and condensed to produce condensate (n) 442 , 3 jJ were collected. The resulting liquid was distilled again under normal pressure using the Widsea distillation apparatus to obtain 412.3 g of silicon tetrachloride (purity 99, open type 5).

net production amount: 0.072 g-mol'), hexachlorodisilane: 24. Og (M298%, 0.
0874 El-mol), 2 g of pot residue was obtained.

The total weight of hexachlorodisilane obtained by distillation of the product condensates (1) and (II) was 83.8.9 (purity 98
Si, 0.305 g-mol), Si-based yield 46
．． Section 7).

Examples 2 to 3 34.0 g and 36.2 g of the distillation still residue of the product condensate (1) obtained in the same manner as in Example 1 were heated to a high boiling point decomposer at a reaction temperature of 300°C and 500°C, respectively. The same experiment as in Example 1 was conducted except for the following changes.

The results are shown in Table 1.

Examples 4 to 6 The distillation bottoms of the product condensate (1) obtained in the same manner as in Example 1 were each diluted with 200 I of silicon tetrachloride to increase the bottom concentration of the diluted feed solution, and Chlorine gas supply amount for lowering reaction is 150ON+nl/hr, 3000Nrne/h
r, 450 ONm7! /hr.

The same experiment as in Example 1 was conducted except that the flow rate was changed to 75ONml/hr.

The results are shown in Table 1.

Examples 7 to 8 Using the same apparatus as in Example 1, the produced condensate (+ ) are separated by distillation to give 52.7% of each hexachlorodisilane.
jj.

36.0g (purity 98% by weight) and 27.3g of higher chloride residue from octachlorotosu/ran, respectively.
fJ, 29,7, r was obtained, and a lowering reaction was performed in the same manner as in Example 1.

The results are shown in Table 1.

/ Comparative Example 1 The amount of hexachlorodisilane obtained by distilling the condensate (1) produced in Example 1 was 59.89 (purity 98% by weight), which was a yield of 33.3% (Si atoms). standards).

The results are shown in Table 2.

Comparative Examples 2 to 3 Produced condensate (1) obtained in the same manner as in Example 1, using the same apparatus as in Example 1, except that the calcium silicon chlorination reaction temperature was changed to 250°C and 150°C, respectively. was separated by distillation to obtain hexachlorodisilane.

The results are shown in Table 2.

It is clear that in the first stage reaction alone, the yield of the produced condensate is very low even if the reaction conditions are variously changed.

[Brief explanation of drawings]

FIG. 1 is a flow route diagram showing a preferred embodiment of the present invention. Patent applicant Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] (1) Calcium silicon, magnesium silicon
By chlorinating particles of silicon or an alloy of metal such as ferrosilicon and silicon at high temperature, or by chlorinating silicon particles themselves at high temperature, polychlorosilane expressed by formula (1) % formula % (1) can be produced. Mixed gas (produced gas)
The product gas is cooled and condensed, and the resulting condensate is distilled to produce silicon tetrachloride ('n = 1), hexachlorodisilane (n = 2), and octachlorotrisilane (n = 3). It is characterized by separating into higher chlorides, reacting the higher chlorides with chlorine again to convert them into silicon tetrachloride and hexachlorodisilane, and recovering hexachlorodisilane by treating this in the same manner as the above-mentioned generated gas. A method for producing hexachlorodisilane.