JPH0222004B2 - - Google Patents

Description

[Detailed description of the invention]

In this invention, hydrogen chloride (hereinafter referred to as HCl) is not substantially contained in the mixed gas produced after the reaction, so there is no need for a separation and recovery process for HCl, and moreover, the yield of trichlorosilane is increased. This invention relates to a method for producing trichlorosilane. In general, silicon for semiconductors (hereinafter referred to as Si), which is used in large quantities in the field of electronics industry, is trichlorosilane (hereinafter referred to as SiHCl ₃ ).
It is produced by depositing Si produced by the reaction between SiH2 and hydrogen (hereinafter referred to as _H2 ) on an electrically heated Si rod, but in this case approximately 70% of the _SiHCl3 supplied to the reaction silicon tetrachloride (hereinafter referred to as SiCl ₄
) occurs. Although it is not impossible to use this by-produced SiCl ₄ as a raw material for the production of Si for semiconductors by the above-mentioned Si precipitation reaction, in this case the reaction rate is slow and the reaction efficiency is low.
It is only used in very limited demand fields, and currently it is used in the production of SiHCl ₃ , which is a raw material for Si for semiconductors, as shown below. That is, as shown in the flow sheet of the conventional method of producing SiHCl ₃ from SiCl ₄ in Fig. 1,
SiHCl ₃ is produced by mixing raw material gases SiCl ₄ and H ₂ in a predetermined ratio in a mixed evaporator A and introducing the mixture into a reactor B.
In this reactor B, SiHCl 3 is synthesized through the reaction of SiCl ₄ + H ₂ → SiHCl ₃ + HCl, and the main components of this result are SiCl ₄ , SiHCl _{3 ,} HCl, and
A reaction mixture consisting of H ₂ is introduced into a condenser C,
A mixed liquid consisting of SiCl ₄ and SiHCl ₃ as condensed components,
It is separated into a mixed gas consisting of non-condensable components H ₂ and HCl, and the condensed mixture is distilled into SiHCl 3 and SiHCl ₃ in distillation column D.
It is produced by separating _SiCl4 .
In this case, the SiCl ₄ separated in the distillation column D is recycled and reused as a raw material, while the non-condensable mixed gas is sent to the scrubber E, where it is mixed with an aqueous HCl solution.
HCl aqueous solution is separated into _H2 and HCl aqueous solution in neutralization tower F.
The H ₂ is converted to NaCl and recycled as raw material through the dryer G and compressor H. In this way, in the conventional manufacturing method of SiHCl ₃ ,
Because HCl is produced as a by-product, equipment such as scrubbers, neutralization towers, and H ₂ dryers are not only required, but also the corrosion and aging of these equipment due to HCl is significant.
Furthermore, it has various problems such as the need to treat the waste to make it harmless. Therefore, from the above-mentioned viewpoint, the present inventors conducted research to solve various problems caused by HCl, which is produced as a by-product during the production of SiHCl ₃ , and found that the main components are SiCl ₄ , _SiHCl3 , HCl,
A reaction mixture gas consisting of H 2 and H ₂ is generated under specific conditions, and this reaction mixture gas is introduced into a reactor in which metal Si is present. HCl in mixed gas
When reacting with the metal Si, components other than HCl do not cause undesirable reactions.
They found that SiHCl ₃ is synthesized, and as a result, there is no HCl present in the resulting mixed gas after the reaction, so there is no need to process HCl, and the yield of SiHCl ₃ also increases. This invention was made based on the above knowledge, and the raw material mixed gas consisting of a mixture of SiCl ₄ and H ₂ at a relative molar ratio of 4:1 to 1:40 is transferred to a cylinder or activated carbon. Introduced into the first reactor filled with a catalyst such as or precious metal, and in this reactor,
The reaction is carried out at a temperature within the temperature range of 500 to less than 900°C, and the main components are SiCl ₄ , SiHCl ₃ ,
Generates a reaction mixture gas consisting of HCl and H ₂ ,
If it is necessary to increase the yield of SiHCl ₃ in the final product mixed gas, a predetermined amount of HCl is mixed therein, and then the reaction mixture gas is made to exist with metal Si forming a fixed bed or a fluidized bed. In this second reactor, the HCl in the reaction mixture gas is
and the metal Si to synthesize SiHCl ₃ , and finally, the main components of this result are SiCl ₄ and
From the generated mixed gas consisting of SiHCl ₃ and H ₂
Separate SiHCl ₃ , while SiCl ₄ , which was similarly separated,
It is characterized by the recycling and reuse of H 2 and H ₂ as raw materials. Next, the reason why the manufacturing conditions are limited as described above in the method of the present invention will be explained below. (a) Relative molar ratio of raw material mixed gas This relative molar ratio determines the reaction efficiency in the first reactor using the reaction formula: SiCl ₄ +H ₂ →SiHCl ₃ +HCl and the separation efficiency in the condensation treatment in the subsequent process. If the molar ratio of SiCl ₄ /H ₂ exceeds 4/1, the amount of H ₂ will become too small, and the progress of the above reaction will be extremely slow. On the other hand, if the molar ratio of SiCl ₄ /SiHCl ₃ is less than 1/40, the amount of SiCl ₄ will be relatively too small, and the separation efficiency in the subsequent condensation step will be significantly reduced. . (b) Reaction temperature of the first reactor If the temperature is less than 500°C, the proportion of SiHCl ₃ in the reaction mixture gas is low and it is not efficient.
On the other hand, if the temperature exceeds 900℃, not only will it be necessary to take measures against high temperatures in the reactor, but it will also increase energy costs.If the temperature rises further, some of the generated SiHCl ₃ will be reduced to H ₂ or thermally decomposed. This causes Si to precipitate.
The temperature was set at 500-900°C. (c) Reaction temperature of the second reactor In the second reactor, the reaction temperature in the reaction mixture gas is
HCl, and if necessary add to this mixed
Reaction formula: Si + 3HCl→
SiHCl ₃ + H ₂ is reacted to synthesize SiHCl ₃ , and the reaction is carried out to completely eliminate HCl. However, if the temperature is less than 400℃, the above reaction is insufficient; on the other hand, if the temperature is less than 700℃, When the temperature exceeds ℃, the reaction of Si + 3HCl → SiHCl ₃ + H ₂
Since the reaction of 4HCl → SiCl ₄ + 2H ₂ takes precedence and results in a decrease in the yield of SiHCl ₃ , the temperature was lowered to 400 °C.
The temperature was set at ~700℃. In addition, FIG. 2 shows a flow sheet of the SiHCl ₃ manufacturing method of the present invention, but as is clear from a comparison with the flow sheet of the conventional SiHCl ₃ manufacturing method shown in FIG. In the method of this invention, the second reactor I is provided, and the scrubber E, neutralization tower F, and
The feature is that the installation of _H2 dryer G is unnecessary. Next, the method of the present invention will be specifically explained using examples. Embodiment 1 FIG. 3 shows a schematic cross-sectional view of an apparatus for implementing the present invention. SiCl ₄ and H ₂ were added to the mixed evaporator at 400 mol/hour and 800 mol/hour, respectively (mole ratio 1:
The raw material mixed gas introduced at the ratio of 2) is heated to an internal temperature of 890°C by an electrically heated graphite resistor 1 hanging from the ceiling of the furnace. The mixture was introduced into the furnace through the supply port 2 at a flow rate of 12 cm/sec. On the other hand, the reaction mixture gas discharged from the discharge port 3 of the first reactor B and introduced into the bottom part from the supply port 5 of the second reactor I through the conduit 4 is
_SiCl4 : 25.4%, _SiHCl3 : 7.9%, HCl: 7.9%,
It had a composition containing 58.8% H ₂ , and its temperature had reached 770°C due to natural cooling. Further, while the reaction mixture gas passes through the metal Si fixed layer 6 whose temperature is adjusted and maintained at 400° C. in the second reactor I by the cooling tube (which may also be used for heating) 10, Since HCl in the reaction mixed gas reacts with the metal Si to form SiHCl ₃ , there is no HCl in the generated mixed gas discharged from the outlet 7 of the second reactor I, and SiCl ₄ :26.1
%, SiHCl ₃ : 10.8%, H ₂ : 63.1%. The results are shown in Tables 1 and 2 as Method 1 of the present invention, together with the measurement results of the component yields of the reaction mixed gas and the produced mixed gas. The resulting mixed gas is introduced into a condenser and thoroughly cooled.
The condensed component consisting of SiCl ₄ and SiHCl ₃ and the non-condensed component of H ₂ are separated, and the condensed component is further introduced into a distillation column to separate SiHCl ₃ , while simultaneously separated SiCl ₄ and the above-mentioned H2 and _H2 were recycled for reuse as raw materials. Example 2 The introduction ratio of SiCl ₄ and H ₂ to the mixed evaporator, the temperature inside the first reactor and its form (presence or absence of the catalyst layer 9 made of activated carbon and/or noble metal in FIG. 3), Whether or not HCl is added to the reaction mixture gas from the lower inlet 8 of the first reactor and its amount, the temperature of the reaction mixture gas near the supply port of the second reactor, and the temperature of the metal Si layer of the second reactor. and its shape

【table】

【table】

【table】

[Table] Methods 2 to 2 of the present invention were carried out under the same conditions as in Example 1, except that the conditions (fixed bed or fluidized bed made of metal Si grains with a particle size of 42 mesh or less) were changed to the conditions shown in Table 1.
14 was carried out, and the component composition and component yield of the reaction mixed gas and produced mixed gas discharged from the first reactor and the second reactor, respectively, were measured. The measurement results are also shown in Table 2. From the results shown in Tables 1 and 2, the first
By introducing the reaction mixture gas discharged from the reactor into the second reactor where metal Si is present and causing a reaction, HCl is contained in the generated mixture gas discharged from the second reactor. It is clear that there is almost no SiHCl 3 present and the yield of SiHCl ₃ is increased. As mentioned above, according to the method of the present invention, since HCl is not present in the generated mixed gas, HCl is not contained in the non-condensable components separated in the condensation process, and therefore the scrubber and neutralization tower, and _H2
There is no need for equipment such as a dryer, and industrially useful effects such as an increase in the yield of SiHCl ₃ are brought about.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing a conventional method for producing SiHCl ₃ , FIG. 2 is a flow sheet showing a method for producing SiHCl ₃ according to the present invention, and FIG. 3 is a schematic cross-sectional view showing an apparatus for implementing the present invention. In the drawings, A... mixed evaporator, B... (first) reactor, C
...Condenser, D... Distillation tower, E... Scrubber, F
...Neutralization tower, G... _H2 dryer, H...Compressor, I...Second reactor, 1...Electric heating type graphite resistor, 6...Metal Si layer, 8...Reaction mixed gas fart
a lower inlet of the first reactor for adding HCl;
9... Catalyst layer, 10... Cooling/heating tube.

Claims (1)

[Claims] 1. A raw material mixed gas consisting of a mixture of silicon tetrachloride and hydrogen at a relative molar ratio of 4:1 to 1:40 is introduced into a first reactor, and the first reactor At,
The reaction is carried out at a temperature within the range of 500 to less than 900° C. to produce a reaction mixture consisting of silicon tetrachloride, trichlorosilane, hydrogen chloride, and hydrogen as major components, and the reaction mixture is subsequently subjected to a second reaction. 2 reactor, and in this second reactor, the hydrogen chloride in the reaction mixture gas is reacted with the metal silicon at a temperature within the range of 400 to 700°C in the presence of metal silicon. A method for producing trichlorosilane, which is characterized in that trichlorosilane is synthesized by using the same method, and finally trichlorosilane is separated from the resulting mixed gas whose main components are silicon tetrachloride, trichlorosilane, and hydrogen. . 2 A raw material mixed gas consisting of a mixture of silicon tetrachloride and hydrogen at a relative molar ratio of 4:1 to 1:40 is introduced into the first reactor, and in this first reactor,
The reaction is carried out at a temperature within the range of 500 to less than 900° C. to produce a reaction mixture consisting of silicon tetrachloride, trichlorosilane, hydrogen chloride, and hydrogen as major components, and subsequently to the reaction mixture, For the purpose of increasing the yield of trichlorosilane, hydrogen chloride is mixed and introduced into a second reactor, and in this second reactor, in the presence of metal silicon, at a temperature within the range of 400 to 700 ° C. Trichlorosilane is synthesized by reacting the hydrogen chloride in the reaction mixture gas with the metal silicon, and finally, the resulting mixture consists of silicon tetrachloride, trichlorosilane, and hydrogen as main components. A method for producing trichlorosilane, which comprises separating trichlorosilane from a gas.