JPS59184720A - Manufacture of polychloro silane - Google Patents

Abstract

PURPOSE:To increase the reaction yield, and to prevent the loss caused by scattering the particles of staring materials and the product by specifying the introducing condition of a chlorine-contg. gas into the particle-fixed layer of a reactor when an alloy of metal and Si, and Si particles are chlorinated at a high temp. CONSTITUTION:An alloy of a metal such as calcium silicon, magnesium silicon, ferrosilicon and Si or Si particles are charged into a reactor having a stirrer for mixing powder to form a fixed layer. The thicknesss of the layer can be chosen at will if the layer has a certain degree of thickness so as to be easily mixed by the stirrer. A chlorine-contg. gas is introduced in such a condition that the fixed layer is not fluidized and particles are not accompanied. The fixed layer is mixed continuously or intermittently by above-mentioned stirrer to carry out chlorination by a solid-gas reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polychlorosilanes by chlorinating silicon alloy particles such as calcium silicon or silicon particles themselves with a chlorine-containing gas.

Polychlorosilanes are compounds represented by the following general formula (1). It is obtained by bringing silicon particles into contact with a chlorine-containing gas at a high temperature, usually 150° C. or higher, to perform a gas-solid reaction to chlorinate the resulting gas and condense the resulting gas.

The product of the above reaction is a synthetic liquid that is liquid at room temperature and contains various polychlorosilanes corresponding to n=1.2.3, . The content ratio of various polychlorosilanes in the synthesis liquid can of course vary depending on the reaction conditions such as the reaction temperature, the concentration of chlorine gas introduced, and the residence time, but it is usually tetrachlorosilane (silicon tetrachloride) (n-1 ), hexachlorodisilane (n-2), and octachlorotrisilane (n=3) account for most of its composition. Each of these polychlorosilanes can be easily separated into each component by distilling the chlorinated synthetic solution described in Section 2 under normal pressure or reduced pressure, but in addition to being used as is as a raw material for semiconductors, each of them can be further processed. By reducing with a suitable reducing agent, monosilane, disilane, trisilane, etc., which are important raw materials for manufacturing semiconductor silicon such as polycrystalline silicon and amorphous silicon, can be obtained.

However, as mentioned above, polyhalosilanes are produced by bringing silicon particles or alloy particles of metal and silicon, such as calcium silicon, magnesium silicon, or ferrosilicon, into contact with chlorine gas at high temperature to perform a gas-solid reaction and chlorinate them. In this case, the raw materials for the reaction, such as calcium solicon, solidify, resulting in problems such as significantly lowering the reaction yield and making it difficult to remove the solid residue after the reaction is completed. Furthermore, probably because the solid residue has an extremely low bulk specific gravity, it expands to a volume three times that of the charged raw material particles, which often causes problems such as damage to the reactor wall. Such damage was solved in the laboratory by using a glass tube with a diameter of about 2 cm as a reactor, filling it with a small amount of calcium silicon particles, and carefully proceeding with the reaction by introducing chlorine gas very little at a time. Even in cases where this is completely unavoidable, it can become a huge problem for scaled, industrial-scale equipment.

In order to solve this problem, conventionally, the gas-solid reaction was carried out using (i
Attempts have been made to use a) a fixed bed with a low bed height, that is, an extremely thin bed, or a) a fluidized bed.

However, (i) if the former fixed layer method is adopted, the layer must be extremely thin, which naturally results in poor volumetric efficiency of the reactor and extremely low productivity (yield) of polyhalosilanes. There was a drawback. Therefore, an extremely large reactor was required, and raw materials such as calcium solicon particles had to be fed frequently. In addition, if the fluidized bed method described in (11) later is adopted, such drawbacks will be solved, but
Since the flow rate of gas to fluidize the particles and form a fluidized bed is enormous, as the reaction progresses, the calcium silicon particles, etc., which are the raw materials that are pulverized, or the generated calcium chloride particles, etc. This has disadvantages in that it scatters out of the system along with the contained gas, causing large losses, and that the process becomes extremely complicated due to operations such as collection and treatment of the fine powder.

The present invention has been made to solve these drawbacks, and its gist is to chlorinate particles of alloys of metal and silicon, such as calcium silicon, magnesium silicon, or ferrosilicon, at high temperatures. In a method for producing polychlorosilanes by chlorinating the particles themselves at high temperatures, the particles are charged into a reactor equipped with a powder stirring means to form a fixed bed, and the fixed bed does not fluidize, causing The polyester is chlorinated by introducing a chlorine-containing gas in such a manner that particles are not entrained and stirring the fixed layer continuously or intermittently by operating the stirring means to cause a solid-gas reaction. Method of packaging chlorosilanes.

exists in

The present invention will be explained in detail below.

The polychlorosilanes that are the target substances in the present invention are compounds represented by the following general formula (1), and among them, 5inC1zh+z (n is an integer of n≧1) (1) Particularly preferred examples include Examples include I.lachlorosilane (silicon tetrachloride), hexachlorodisilane, octachloro-1-lysilane, and decachlorotetrasilane.

The present invention provides for preparing such polychlorosilanes by a reaction known per se, using a specific reactor and under specific conditions, i.e. an alloy of metals such as calcium silicon, magnesium silicon or ferrosilicon with silicon. It is obtained by chlorinating the particles or silicon particles themselves by bringing them into contact with a chlorine-containing gas at a high temperature, usually 150° C. or higher, to carry out a gas-solid reaction.

The reactor used in the present invention is equipped with a powder stirring means, and the layer of particles of calcium silicon, etc. charged therein is
Any type of liquid may be used as long as it can be stirred continuously or intermittently. That is, the reaction container may be of a vertical cassette type, or of a horizontal groove type, cylindrical type, or U-shaped equal volume type. 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. Stirring means provided in the reaction vessel include propeller type, turbine type, paddle type, spiral type (especially double Il!!! spiral type),
There are various types of stirrers such as screw type, but the latter two types also have the function of transporting powder, so they are particularly suitable for continuous operations in which particles are continuously supplied and continuously extracted. It is.

Specifically, for example, a stirred tank type reactor can be used as a reactor of this type, but a groove type stirring device, a kneading device, etc., which are commonly used as a material stirring type dryer, can also be used as a base for the reaction. It can be suitably used as a reactor by modifying its detailed design to provide various functions necessary for the reactor.

Next, the operation of the present invention will be explained.

The metal particles such as calcium silicon, which are the raw materials used in the present invention, have a typical specific gravity of 2 to 5 and a particle size of 5 to 300 m e s.
A sand grain-like material having a size of about 300 yen is preferably used, but it may also be a mixture or a mixture of other metals such as manganese and the like. If the particles are large, crush them and
It is preferable to use the particles with a suitable particle size.

Prior to the reaction, particles of calcium silicon or the like as a raw material are charged in a layered manner into a reactor equipped with a powder stirring means as described above to form a fixed layer of the particles. The thickness of the fixed layer can be set to any layer height as long as the fixed layer can be easily stirred when the powder stirring means is operated.

As the reaction progresses, the volume of the fixed bed expands as described above, so it is desirable to provide a space above the reactor that is twice the height of the bed or more.

The chlorine gas that should be sent to the reactor is usually sold filled in a container, etc., and after sufficiently dehydrating it by treating it with concentrated sulfuric acid or silica gel, it can be used as is without further purification. You can. However, in order to keep the reaction rate within an easily controllable range and precisely control the reaction heat, chlorine gas is not used as is.
It is desirable to dilute with a gas inert to the reaction system, such as helium, neon, argon, xenon, nitrogen, silicon tetrachloride, etc., to obtain a chlorine-containing gas with a chlorine content of 1 to 90 mo1%, preferably 3 to 70 mo1%. .

The chlorine-containing gas is supplied to the lower or middle part of the fixed bed according to a conventional method, and the gas is caused to rise in the fixed bed and solidify.
A gas reaction may be carried out, but the speed of this reaction is extremely fast. For example, if a horizontal reactor is used and the bed height is not very large, gas is supplied to the surface of the fixed bed. Even if the reaction is carried out without flowing gas along the surface, polychlorosilane is produced at a rate sufficiently high for practical use.

The mode of dregs feeding is such that the fixed bed is not fluidized by the gas,
In addition, it is necessary that the particles forming the fixed layer are not entrained in the gas. To achieve this, the gas flow rate must be controlled within an appropriate range by considering the solid-gas contact method, particle size (more precisely, particle size distribution), particle density, gas density, etc. Specifically, the gas flow rate in the fixed bed is below the fluidization start rate Umf, and the gas velocity at the product outlet from the reactor is
The terminal velocity of the particles may be lower than the terminal velocity of the particles. The above-mentioned fluidization start speed and final particle speed can be easily calculated from chemical engineering empirical formulas if physical property data of the particle system are given, but of course they may also be determined by experimental measurement.

As a matter of course, if the gas flow rate is controlled to be equal to or lower than the above Umf, the possibility that the particles will be entrained in the gas and dissipated can be substantially ignored.

The reaction temperature is at least 100°C, preferably 150°C.
C or more is required, so it is necessary to heat at the start of the reaction, but since this reaction is a strongly exothermic reaction, once the reaction has started, the reaction system is maintained at the desired reaction temperature. Therefore, a cooling operation must be performed to remove a large amount of the generated reaction heat.

The reaction is carried out while the fixed bed is mechanically stirred continuously or intermittently by operating the stirring means.

Since the purpose of this stirring is to cause the reaction product to expand the deposit smoothly, a very low stirring speed is sufficiently effective, and there is no need for the stirring speed to be so high as to cause dust scattering. For example, when using a tank reactor with an inner diameter of 30 cm, a stirring blade with a diameter slightly smaller than the inner diameter is used.
It is sufficient to rotate it gently at a speed of about 30 r, p, m or less. Depending on the case, stirring of about 1 r, p, m may be enough to achieve the purpose of the present invention.

Further, as shown in Examples below, sufficient effects can usually be obtained even if stirring is performed intermittently.

The reaction product is discharged from the reactor as a high-temperature gas, and is led to a cooler where it is cooled and condensed to obtain a liquid mixture of various polychlorosilanes. If necessary, it is of course possible to distill the mixture to separate it into individual components.

As mentioned above, in the present invention, the solid-gas reaction is carried out while stirring the fixed bed continuously or intermittently, so that the raw material, such as calcium silicon particles, and the product, such as calcium chloride particles, are always kept in a suitable state. It is homogenized so that the reaction takes place uniformly throughout the fixed layer. Therefore, it is possible to substantially prevent the occurrence of a local overheating phenomenon called a so-called pot spot.

In addition, the enormous volume expansion that occurs as the reaction progresses and is three times that of the fixed bed at the start of the reaction is effectively pushed up and released into the space above the reactor by stirring the fixed bed. Therefore, excessive expansion pressure is not applied to the inner wall of the reactor, and damage to the reactor is therefore completely prevented.

In addition, in the past, unreacted calcium silicon, etc. solidified in the fixed bed, hindering the smooth progress of the reaction and reducing the reaction yield, and making it difficult to remove the solid product after the reaction was completed. However, this phenomenon never occurred.

On the other hand, in the present invention, the chlorine-containing gas is fed into the reactor in a manner in which the fixed bed does not fluidize and particles are not entrained in the gas, so the reaction is not carried out as in the case where a fluidized bed is used. There is no drawback that calcium silicon particles, etc., which become fine as the process progresses, are entrained in the gas and dissipated out of the system.

Hereinafter, the present invention will be explained in more detail with reference to Examples, but these are merely examples, and it is understood that the technical scope of the invention as defined in Article 70 of the Patent Act is interpreted to be limited thereby. should not be done.

(Example-1) Using the reaction apparatus shown in Fig. 1, Calcilla, IA
An experiment was conducted to produce polychlorosilanes by chlorinating SiJcon particles.

Dry chlorine gas is supplied from 10 to the cylinder through a conduit.
20 to the flow meter 30. Here, the flow rate is controlled to a predetermined value. Silicon tetrachloride for dilution is supplied from a tank 50 to a conduit 7 using a metering pump 6o.
0 to the evaporator 80. The silicon tetrachloride vaporized in the evaporator is mixed with the chlorine gas sent through the conduit 40 in the evaporator. Mixing ratio is salt complete gas 100
560 parts by weight of silicon tetrachloride for serious illness,
The chlorine-containing mixed gas sent to the reactor 1o has a composition of 30 mo1% chlorine gas and 70 mo1% silicon tetrachloride.

The reactor 100, as shown in FIGS. 2(a) and (b),
Upper middle 40 cm, depth 50 cm, length 150 cm
It is a ribbon mixer type with a U-shaped cross section, and is equipped with an agitator with a variable speed consisting of spiral ribbon blades 101, and a heat medium 105 in a jacket 1o3.
can be heated in circulation.

Note that 90' is a raw material gas inlet, and 110' is a produced gas outlet.

Prior to the reaction, sufficiently dried 8 to 4
3 m e s h calcium silicon particles 34
Kg was charged to form a fixed layer with a thickness of about 9 cm, and then nitrogen gas was flowed for 30 minutes to completely purge the air in the system.

After the reactor temperature was set to 250 °C using the heating medium 105, the chlorine-containing mixed gas was mixed at 9.6 Kg/llr.
It was supplied to the top of the fixed bed at a flow rate of . After the reaction has started, the reaction temperature is set to 200'C, and the above stirring step 1 is continued.
'1! 10 r at a rate of 5 minutes per hour,
The fixed bed was stirred by running rotation at speeds of p, m.

The gas containing the produced polychlorosilanes discharged from the reactor passes through conduit 110 to condenser 12
0, where the cooled and condensed polychlorosilanes were stored in a receiver 140 via a conduit 130. Incidentally, non-condensable components such as unreacted chlorine were extracted from the upper part of the receiver 140 to the outside through a conduit 150.

As described above, silicon tetrachloride 95.6% by weight (hereinafter simply expressed as %), hexachlorodisilane 2.8%
, octachlorotrisilane and higher boiling components 1.
Mixed composition 911 of polychlorosilanes consisting of 5%
Kg was obtained. In other words, the yield of higher boiling components than hexachlorodisilane based on the raw material calcium silicon is 4
It was 0%.

After the reaction was completed, the reactor was opened and the interior was inspected to find that the raw material calcium silicon had almost completely reacted.

Furthermore, the volume of solid residue in the reactor, which was thought to be mainly composed of calcium chloride, was about three times the amount of calcium silicon charged. Furthermore, no damage to the inner wall of the reactor was observed.

The amount of solid particles entrained in the gas discharged from the reactor was negligible throughout the reaction operation, especially in the latter stages of the reaction.

(Comparative Example-1) An experiment was conducted using the same apparatus as in Example-1 and under the same conditions as in Example-I, except that stirring was not performed.

As a result, a mixed composition 899 consisting of 99.8% silicon tetrachloride, 1.7% hexachlorodisilane, 0.5% octachlorotrisilane and higher boiling components
Kg was obtained. The yield of high-boiling components higher than hexachlorodisilane was as low as 20% based on the charged calcium silicon.

After the reaction was completed, the reactor was opened and the interior was inspected to find that what appeared to be calcium silicon had solidified in a considerable portion of the interior of the fixed layer, and it was extremely difficult to remove this unreacted residue.

[Brief explanation of drawings]

FIG. 1 is a flow sheet diagram showing a preferred embodiment for carrying out the present invention. FIG. 2 shows an example of a reactor, with FIG. 2(a) being a front view thereof and FIG. 2(b) being a side view thereof. Patent applicant Mitsui Toatsu Chemical Co., Ltd. Broom II21 No. 212]

Claims (1)

[Claims] (1) Powder agitation in a method for producing polychlorosilanes by chlorinating particles of alloys of metal and silicon such as calcium silicon, magnesium silicon, or ferrosilicon, or by chlorinating silicon particles themselves at high temperatures. The above-mentioned particles are charged into a reactor equipped with a means to form a fixed bed, the chlorine-containing gas is fed in such a manner that the fixed bed is not fluidized and the particles are not entrained, and the above-mentioned stirring means is operated to form a fixed bed. A method for producing polychlorosilanes, which comprises chlorinating a solid-gas reaction while continuously or intermittently stirring a fixed bed.