JPH01313315A - Production of trichlorosilane - Google Patents

Abstract

PURPOSE:To obtain trichlorosilane smoothly and with high efficiency even at a reaction temp. in a low temp. range of 300 deg.C or below by carrying out a heterogeneous phase reaction between liquid or gaseous SiCl4 and Si and H2 or H2 plus HCl in the presence of Cu and/or Cu compd., etc., and a heteropolyacid. CONSTITUTION:Trichlorosilane(HSiCl3) is obtd. by a reaction as expressed by the formula between SiCl4 and Si and H2 or H2 plus HCl. In this case, SiCl4 is used in the form of liquid or gas, and the reaction is carried out in a heterogeneous phase of gas-liquid-solid or gas-solid. Said heterogeneous phase reaction is proceeded in the presence of Cu and/or Cu compd., a molten salt of aluminium halide such as AlCl3 with NaCl, etc., and a heteropolyacid. Said heteropolyacid consists primarily of an oxide of Mo and/or W being expressed by the formula II or III. Said reaction is proceeded smoothly and effectively even in a low temp. range so low as ca.300 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a process for producing trichlorosilane from silicon tetrachloride and hydrogen.

BACKGROUND OF THE INVENTION With the recent development of the electronics industry, the demand for polycrystalline silicon, monosilane gas, etc. has increased rapidly, and it is expected that the demand will continue to increase in the future. Here, trichlorosilane is used in the largest quantity as a raw material for the above-mentioned silicon materials.For example, high-purity polycrystalline silicon is produced by thermal decomposition of trichlorosilane, and currently high-purity polycrystalline silicon is Most crystalline silicon is manufactured using this method. Recently, a method for producing monosilane by disproportionation reaction of trichlorosilane has been put into practical use, and the demand for trichlorosilane will become extremely important in the future. However, in these methods, trichlorosilane is consumed and a large amount of silicon tetrachloride is produced as a by-product. For example, in the production of high purity polycrystalline silicon by thermal decomposition of trichlorosilane, about 60% of trichlorosilane is Silicon chloride is produced as a by-product, and in the production of monosilane by disproportionation of trichlorosilane, silicon tetrachloride is produced as a by-product in an amount substantially three times the mole of monosilane.

It is known that this by-produced silicon tetrachloride can be used as a raw material for Aerosil, etc., thereby reducing the production price of trichlorosilane. For example, by converting silicon tetrachloride to trichlorosilane, the production of monosilane by disproportionation of trichlorosilane can be done by converting it back to trichlorosilane and reusing it as a raw material in the above method. This resulted in a process for producing monosilane with hydrogen, and this process has recently been put into practical use. Therefore, the technology of converting silicon tetrachloride into trichlorosilane is extremely useful, and in particular, it is extremely important from the economic point of view of the process to be able to do this at low cost, simply, and efficiently.

Conventionally, the following method is known as a method for converting silicon tetrachloride into trichlorosilane.

(1) A method for producing trichlorosilane by reacting silicon tetrachloride and hydrogen at 1000°C or higher.

(2) Soo' silicon tetrachloride, hydrogen and metallic silicon
A method for producing trichlorosilane by reacting near c.

(3) A method of producing trichlorosilane by reacting silicon tetrachloride, hydrogen, metallic silicon, and hydrogen chloride at around 500°C.

Regarding method (1), for example, Japanese Patent Application Laid-Open No. 57-371
In No. 1, trichlorosilane was obtained at a yield of about 60% by spraying hydrogen and silicon tetrachloride onto a heating element at the above temperature at 1100 to 1600''C.

In addition, in JP-A-57-156318, the first stage is 900
The molar ratio of hydrogen and silicon tetrachloride at a temperature of °C is Hz/
5iC14-2 to obtain trichlorosilane with a yield of 25%. In JP-A-59-45920, trichlorosilane is obtained by reacting silicon tetrachloride with hydrogen in plasma. In JP-A No. 60-81010, silicon tetrachloride and hydrogen are reacted in a temperature range of 1200 to 1400 DEG C. to obtain trichlorosilane with a yield of about 30%.

Method (2) can be said to be a thermally advantageous method since the reaction proceeds at a relatively low temperature compared to method (1). or(
Method (3), in which hydrogen chloride gas is used to advance the reaction more effectively than method (2), has similar characteristics, including the natural age of death. For methods (2) and (3), it is effective to use a catalyst, and for example, in JP-A-56-73617, using copper powder as a catalyst, Trichlorosilane was obtained by performing a fluidized bed reaction at 600°C. Further, in JP-A-58-11042, trichlorosilane is obtained by conducting a reaction using a catalyst supported with copper or with copper and nickel supported.

In these methods, for example, method (1) allows trichlorosilane to be obtained with a fairly high conversion rate of silicon tetrachloride, but in particular, in order to obtain trichlorosilane with a yield of 30% or more, a temperature of 1000 °C or more is required. Since the reaction takes place at a high temperature, the amount of heat required for this is true. In addition, because it is a high-temperature reaction, silicon chloride severely corrodes the reactor, etc., and undesirable high-molecular-weight silicon chlorides are inevitably produced as by-products.Therefore, it is still far from practical use. It is something.

On the other hand, methods (2) and (3) are useful methods for producing trichlorosilane from a thermodynamic point of view, and as mentioned above, they are by-products that are produced in the method for producing monosilane by disproportionation of trichlorosilane. The production of trichlorosilane from silicon tetrachloride can be said to be a very useful method, especially since method (2) essentially produces monosilane from metallic silicon and hydrogen. Although the yield of trichlorosilane is high in method (3), hydrogen chloride does not participate in the conversion of silicon tetrachloride to trichlorosilane, and trichlorosilane is essentially synthesized from metallic silicon. It happens. Therefore, from the perspective of reusing silicon tetrachloride, it is somewhat less useful than method (2), but it also has the advantage of increasing the yield of trichlorosilane, and by using a small amount of hydrogen chloride. It is desirable to make use of these characteristics.

Furthermore, a process that combines these methods (2) and (3) is also known (Japanese Patent Application Laid-open No. 36318/1983). Method 2) is the best, and from the perspective of producing trichlorosilane, method (3) is also an excellent method and is difficult to discard.In other words, method (2) or (3) is
It is also highly economical, and method (2) in particular is currently being put into practical use as the preferred method.

However, in method (2), the reaction temperature is usually 50°C.
The reaction is carried out at a temperature of 0 to 600°C, and at a low temperature of about 300°C, the reaction hardly progresses, and there are no examples of substantial production of trichlorosilane. When producing trichlorosilane continuously, a gas-solid phase fluidized bed apparatus is used. However, in this case, since the process is carried out at a high temperature of 500 to 600°C, the raw material chlorinated silane is highly corrosive in the high temperature range, and corrosion of the equipment is a major problem when producing trichlorosilane industrially. Therefore, it has many drawbacks that need to be further resolved for industrialization, such as a decrease in the selectivity of trichlorosilane due to the formation of high molecular weight chlorosilanes, and the use of a large amount of heat.

Problems to be Solved by the Invention An object of the present invention is to discover a catalyst that has a higher reaction activity than conventional catalysts when producing trichlorosilane through the reaction of silicon tetrachloride, metal silicon, and hydrogen.
The object of the present invention is to provide an extremely economically advantageous method that can produce trichlorosilane extremely effectively even in the reaction temperature range below .degree. C. and that does not volatilize catalyst components even in gas phase reactions.

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned problems, the inventors of the present invention have found that the present inventors have succeeded in producing polycrystalline silicon by thermal decomposition of trichlorosilane or disproportionally distributing trichlorosilane in the presence of a specific catalyst. The present inventors have discovered an extremely economical method for effectively utilizing silicon tetrachloride by converting silicon tetrachloride, which is a by-product in the production of monosilane by chemical reaction, into trichlorosilane, and have completed the present invention.

That is, the present invention provides a method for producing trichlorosilane by reacting silicon tetrachloride and metallic silicon with hydrogen or hydrogen and hydrogen chloride, in which the silicon tetrachloride is in a liquid or gaseous state and the reaction system is in a gas-liquid state. Trichlorosilane, characterized in that it is a heterogeneous phase reaction of one solid or gas and one solid, and the heterogeneous reaction is carried out in the presence of a metal steel and/or a copper compound, a molten salt of aluminum halide, and a heteropolyacid. This is a manufacturing method.

The present invention will be explained in detail below.

The conversion of silicon tetrachloride into trichlorosilane carried out in the present invention is basically expressed by the following formula % formula % (1). This reaction is an equilibrium reaction, and the higher the temperature, the higher the Hz/5iC1, the higher the molar ratio, and the higher the reaction pressure, the more it progresses to the right. Regarding the temperature, 300℃
If the temperature is higher than that, the equilibrium composition will not be significantly favorable to trichlorosilane, and the excess heat will have a greater economic impact.Therefore, if possible, In this case, it is economical to carry out the process at a low temperature of 400°C or less.There is no known example of producing trichlorosilane at a low temperature of around 300°C, but in the present invention, By carrying out the above reaction in the presence of metallic copper, a heteropolyacid, and a molten salt consisting of an aluminum halide and an alkali metal halide, it is possible to produce trichlorosilane in good yield even at a low temperature of about 300°C. Naturally, it is also possible to adopt a method of increasing the yield of trichlorosilane by adding hydrogen chloride gas into the reaction system of the present invention.

The effectiveness of the molten aluminum halide salt used in the present invention will now be described.

It is naturally assumed that aluminum halide is effectively involved in the reaction in the present invention. However, many of these aluminum halides are highly volatile even at normal reaction temperatures and even lower temperatures, so even if they are added to the reaction system, they will volatilize from within the system and will not react effectively. For example, aluminum chloride and aluminum bromide have the disadvantage that they do not act on the reaction depending on the reaction form.
These aluminum halides easily volatilize at temperatures below 200°C, and in solid-gas flow reactions, these aluminum halides
Even if the reaction is carried out at 0°C or lower, it is difficult to use it effectively.These drawbacks can be overcome by making aluminum halide into a molten salt with an alkali metal as in the present invention, and as a result, the above-mentioned reaction is less The effect of aluminum halide was not inhibited and the volatilization of aluminum halide was completely suppressed, making the reaction extremely efficient.

The purity of the metallic silicon used in the present invention is not particularly limited, and it may be a low-purity product of about 98% of metallurgical silicon or a high-purity silicon; from an economic point of view, the former is sufficient. It is preferable to use this because good results can be obtained, and although the form of metal silicon does not matter, it is recommended to use it in the form of a powder with a large surface area from the viewpoint of reaction rate.

Of course, it is also possible to use it in other forms such as granules.

The metal copper used in the present invention is not particularly limited, and usually reprinted electrolytic copper is used, but other reduced copper can also be used. There is no need to worry too much about purity, and its form does not matter, but from the viewpoint of reaction rate it is preferable to use it in powder form, which has a large surface area.Of course, it can also be used in other forms such as granules. It is. Furthermore, copper compounds include copper chlorides, sulfates, nitrates, etc.
It is preferable to use chloride in view of the reaction type.

The molten salt used in the present invention is obtained by mixing aluminum halide and an alkali metal halide in a specified ratio and heating and melting the mixture. At this time, the ratio of aluminum halide to alkali metal halide can be arbitrarily determined, but preferably the molar ratio of aluminum halide to alkali metal halide is 5=
A ratio of 1 to 1:5 is recommended. If there is too much of one of the compounds, it is difficult to obtain a preferable melting state.However, in the present invention, these compositions are not limited to thermal theory, and the melting temperature is the temperature at which the above-mentioned mixture melts. It is good if it exists and is not particularly limited.

Next, the aluminum halides used in the present invention are aluminum fluorides, chlorides, bromides and iodides,
Preferably, it is recommended to use aluminum chloride from the viewpoint of economy and corrosion resistance of equipment. The present invention can also be carried out using a molten salt formed from one or more of these aluminum halides.

Furthermore, the alkali metal halides used in the molten salt with aluminum halide in the present invention include fluorides, chlorides, bromides, and iodides of metals represented by Li, Na, Rb, Cs, and Fr in the element symbol. It is. More preferably, chlorides such as sodium chloride and potassium chloride are recommended from the viewpoints of economy and corrosion resistance. It is also possible to provide the present invention using one or more of these.

The heteropolyacid used in the present invention is mainly composed of oxides of molybdenum and/or tungsten, and is a compound represented by the general formula %. However, here Ml, FI2
represents a metal element, Ml is 2% Si, Co
%Cr, Mn, Ni, etc., and this metal element is usually called a central atom or a heteroatom. Further, M2 is generally a metal atom such as V.

Also, for boat fishing, a takes a value of 1 or 2, b takes a value of O or l, C takes an integer around 10 to 20, d takes an integer around 40, and e usually takes an integer of 3 to 4. Takes an integer of degree. Specifically, phosphomolybdic acid (83PMo+tOna), silicon molybdic acid (H4S
iMol*0no), phosphotungstic acid (HzPW+
□04゜), silicungstic acid (H4SiW+zOa
・) and these Mo, one or more of one atom is V
In the present invention, these heteropolyacids are used at a temperature of 200°C or higher, preferably 300-6
Use one that has been heat-treated at a temperature of 00°C.

Next, a method for converting silicon tetrachloride into trichlorosilane in the present invention will be described.

The conversion method is basically carried out according to the above formula (1), but in the present invention, the reaction is carried out in a so-called gas-solid phase heterogeneous reaction system, and the reaction is carried out in a so-called gas-solid phase heterogeneous reaction system. It is also possible to perform a gas-liquid-solid heterogeneous reaction with silicon tetrachloride in a liquid state below the critical temperature. Hydrogen used in the reaction may be diluted in advance with an inert medium (gas) such as argon, helium, and/or nitrogen, but from the viewpoint of reaction equilibrium, reaction rate, and economics, hydrogen alone may be used. It is preferable to use hydrogen as a pressurizing medium, and there is no problem even if it contains impurities that are normally expected in hydrogen. Furthermore, when carrying out a pressurized reaction, it is preferable to use hydrogen as a pressurizing medium at the same time, and depending on the reaction conditions. When using a solvent that is inert (does not cause a reaction) with respect to raw materials, products, metallic copper and/or copper compounds, aluminum halides, alkali metal halides, etc., such as n-hexane and n-hebutane. It is also possible to use aliphatic hydrocarbons such as typified aliphatic hydrocarbons, alicyclic hydrocarbons typified by cyclohexane and cyclooctane, and aromatic hydrocarbons typified by benzene and toluene.

Although the reaction temperature is not intentionally stipulated, in order for the reaction to proceed substantially, it should be 150°C or higher, preferably 20°C.
It is preferable to carry out the reaction at a temperature of 0 to 650°C from the viewpoint of reaction equilibrium and also from the viewpoint of reaction rate. In addition, when carrying out this reaction, trichlorosilane in an amount below the reaction equilibrium amount is mixed in the silicon tetrachloride charged as a raw material. This means that it can be used even if trichlorosilane remains in silicon tetrachloride when the trichlorosilane produced by the reaction is separated by distillation, etc. However, due to the reaction equilibrium, it is possible to use trichlorosilane containing trichlorosilane. It is desirable to use as little silicon tetrachloride as possible because this will substantially increase the amount of trichlorosilane produced.

Next, the amounts of raw materials used in the present invention, metallic copper, aluminum halide, alkali metal halides, and additives such as heteropolyacids, will be described.

The amount of metal silicon used in the present invention is not particularly limited, but when the process is carried out batchwise, it is preferably 1% by weight or more based on silicon tetrachloride, and if it is less than this value, metal silicon will be lost during the reaction. There is a risk that it will be consumed and the reaction will not be effective. The amount of metallic copper and/or digested compound is not particularly limited, but it is recommended that the reaction be carried out at a metal atomic ratio (g-atmi/g-atms) to the charged silicon metal of 0.5% or more. It is preferable to carry out the reaction with an atomic ratio of aluminum halide to metal silicon of 0.1% or more, and furthermore, the molten salt used is used as a reaction solvent, that is, it is used several times or more in weight ratio to metal silicon. It is also possible.

The amount of heteropolyacid used is also not particularly limited, but it is preferably used in an amount of 0.5% by weight or more based on metal silicon.

Next, specific embodiments for carrying out the present invention will be described. As mentioned above, the reaction in the present invention is preferably carried out at a temperature of 150° C. or higher, further preferably carried out under pressure (hydrogen pressure is preferable), and is carried out by either a flow reaction method or a batch reaction method. It is also possible to do so.

The method of carrying out the present invention is not particularly limited, but the following method may be mentioned as a method that is easy to carry out. Of course, the present invention is not limited to these methods.

(1) After putting a predetermined amount of silicon tetrachloride, metallic silicon, metallic copper and/or copper compound, and a molten salt consisting of an aluminum halide and an alkali metal halide into an autoclave, pressurize to a predetermined pressure with hydrogen, A method in which a heating and stirring reaction is then carried out.

(2) Continuously pour a predetermined amount of molten salt of silicon tetrachloride, copper and/or copper compound, aluminum halide, and alkali metal halide into a pressurized reactor that is preliminarily maintained at a predetermined temperature and a predetermined pressure with hydrogen. A method of introducing and reacting.

(3) A molten salt consisting of silicon metal, copper and/or a copper compound, aluminum halide, and an alkali metal halide is placed in a reactor in advance, and silicon tetrachloride and hydrogen are heated under hydrogen pressure while being maintained at a predetermined temperature. A method in which the reaction is carried out while continuously introducing and continuously extracting the produced gas, and metal silicon, metal copper and/or copper compounds, and molten salt are introduced intermittently or continuously as necessary.

Example □The present invention will be specifically explained below with reference to Examples.

The heteropolyacids used in this example were all stored at 400°C.
The heat treatment was performed for 2 hours.

Example 1 Silicon (purity 98%, approximately 200 mesh), metallic copper powder (for chemical use, approximately 200 mesh), and sodium chloride were placed in a Pyrex reaction tube with an inner diameter of 11 mm that was equipped with a glass filter at the bottom to hold solids. and molten salt of aluminum chloride (melting temperature 200°C1^1cli/
NaC1-1 molar ratio) and a mixture of various heteropolyacids (composition Cu/Si=10 wt%, AlC1,/C
uJ, 5 molar ratio, heteropolyacid/Cu-125wt%)
This mixture was sandwiched between silica wool, and the inside of the fixed 0 reaction tube was thoroughly replaced with helium. Silicon tetrachloride was kept at O''C and bubbled with hydrogen at a predetermined flow rate, and the mixed gas was mixed with hydrogen. (H*/5i calculated from the vapor pressure of silicon tetrachloride
The C1a molar ratio was 9.3. ) The reaction tube was maintained at a predetermined temperature to carry out the reaction for producing trichlorosilane. Results regarding various heteropolyacids, reaction contact times, and reaction temperatures were determined by gas chromatography analysis. The result is the first
Shown in the table.

Very excellent reaction results were obtained even in low temperature reactions. Note that the reaction product gas composition is the value after the reaction has become steady. In addition, the contact time shown here is calculated by calculating the volumetric expansion due to temperature increase assuming that the raw material mixed gas is an ideal gas, calculating the flow rate of the mixed gas at a specified temperature, and dividing the charged solid volume by this flow rate. And so.

Table 1 Peter reactor contact time TC5/(TC3+5T
C) Polyacidity “Csec so1% phosphorus Mo
Acid 400 2.3 24.6 Phosphorus Mo acid
400 1.4 24.3 Phosphorus Mo acid 4
00 0.8 24.5 (Equilibrium) Phosphorus Mo acid 300 6.5 16.6 Phosphorus Mo acid
300 2.8 13.7 Phosphorus W acid 400
0.8 24.2 Phosphorus W acid 300 6
．． 5 15.8 Silica W acid 400 0.8
24.6 Silica W acid 300 6.5
17.5 Silica W acid 300 2.8 14.
6 Silicic Mo acid 400 0.8 24.8 Silicic Mo acid 300 12.0 21.2 (
Equilibrium) Silicic acid 300 6.5 17.
9 Silicic Mo acid 300 2.8 15.3 Silicic Mo acid 300 1.4 13.2 Silicic M
o acid 300 0.9 11.0TCS-)
Lichlorosilane, 5TC-Silicon Tetrachloride TCS/(TC
3+5TC) - TC5 composition in reaction product gas Comparative Example 1 Silicomolybdic acid was used as the heteropolyacid, the ratio of each solid additive to silicon was the same as in Example 1, and a solid mixture excluding copper powder, A solid mixture excluding the molten salt, a solid mixture excluding the heteropolyacid, and a solid mixture consisting of copper powder and silicon excluding the heteropolyacid and the molten salt were charged in the same volume into the same reaction tube as in Example 1,
Hydrogen and silicon tetrachloride were supplied to the reaction tube in the same manner as in Example 1, and a reaction for producing trichlorosilane was carried out as a blank test at 500° C. and a contact time of 2 seconds.

As shown in Table 2, the results are lower than the 400°C reaction results in Example 1 in all cases, and the three-component addition of copper metal, molten salt, and heteropolyacid in the present invention is extremely trivial. It was found to be effective in the production reaction of chlorosilane.

Table 2 Removal components TC5/(TC5+STC)m
o1% Copper powder 0 Molten salt 18.6 Heteropolyacid 16.3 Molten salt 10 Heteropolyacid 23.4 However, in a 400°C reaction with a solid mixture excluding the molten salt and heteropolyacid, at a contact time of 2 seconds, The composition of trichlorosilane in the generated gas is 12.0 mol%.

This also shows that the catalyst system of the present invention has extremely high activity compared to known copper catalysts.

Comparative Example 2 Keimolybdic acid was used as the heteropolyacid, the aluminum chloride in Example 1 was used as aluminum chloride rather than as a molten salt, and the mixed composition of Example 1 and the solid (Cu/Si, heteropolyacid/Cu, AlCl5 /Cu
) and solid loading capacity were the same, and the reaction method and analysis method were the same as in Example 1, and the reaction for producing trichlorosilane was carried out at 500°C.

When this reaction was carried out, it was observed that a white solid was precipitated and adhered to the upper part of the reaction tube that was not heated during the temperature raising process.

The concentration of trichlorosilane in the generated gas in a steady state with a contact time of 2 sec (TCS/(TC5+5TC) so1
%) was 19.2 so1%, which shows an extreme decrease in activity compared to Example 1 using silicone molybdic acid, and is almost the same as the result in Comparative Example 1 excluding the molten salt. Ta. The reason for this is thought to be that aluminum chloride was volatilized and removed from the reaction system.

Example 2 The molten salt was KCI-AICIz (50150 mol ratio), and the solid mixture Cu/Si, 51Mo-Ac1d
/Cu, AlC1z/Cu composition was the same as in Example 1, the molten salt was changed, and other than that, a trichlorosilane formation reaction was carried out in exactly the same manner as in Example 1.

As shown in Table 3, the reaction results did not change even when the molten salt was changed, and it was found that there is no problem even if a molten salt consisting of aluminum chloride and potassium chloride is used.

Table 3 Reaction temperature Contact time TC3/(TC3+5TC)
”Csee mo1% 400 1.4 24.2400
0.8 24.6300 6.5
17.3 Example 3 Using silicon molybdic acid as the heteropolyacid, each composition of the solid mixture 51Mo-Ac1d/Cu 5AICIs
/Cu was the same as in Example 1, Cu/Si was 54%, 2
wt%, and the amount of each additive relative to silicon is 1/2.1
The trichlorosilane production reaction was carried out in the same manner as in Example 1 except that the amount of trichlorosilane was reduced to 15.

As shown in Table 4, even when the amount added as a catalyst was halved, there was no effect on the reaction at all, and even when it was further reduced to one-fifth, no significant decrease in activity was observed. For comparison, some of the results of Example 1 are also listed.

Table 4 Cu/Si Reaction temperature Contact time TC3/(TC5
+STC) wt% 'Csec +go1%1
0 400 0.8 24.810 3
00 12.0 21.210 300
6.5 17.910 300 2.8
15.310 300 1.4
13.25 400 0.8 25.35
300 12.0 21.75 300
6.5 18.22 400 0.
8 23.12 300 12.0
19.62 300 6.5
13.7 Example 4 The metal steel was replaced with chloride steel, and the molten salt, silicomolybdic acid, and Cu (CuC
1z or as copper in CutCI□) is the composition of Example 3
A trichlorosilane production reaction was carried out using the same reaction apparatus and reaction method as in Examples 1 to 3.

As shown in Table 5, even when copper was converted to copper chloride, high reaction activity was similarly exhibited.

Table 5 Copper chloride Reaction temperature Contact time TC5/ (TC5+5
TC)”Csec mo1% CuCIz 400 0.8 23.7
CuC1g 300 12.0 20.
9CuC1z 300 6.5 14.
4CuiC1g 400 0.8 23.
4CuzC1g 400 12.0 20
．． 2 (uzcll 400 6.5 14
．． 7 Example 5 Using silicon molybdic acid as the heteropolyacid, the composition of silicon, copper powder, molten salt, and heteropolyacid was the same as in Example 1, and a SUS perforated plate with an inner diameter of 14 mm was attached to the lower part to hold the solid. A SUS reaction tube prepared as above was filled with 15 d of the above solid mixture, and the inside of the reaction system was pressurized to 35 atmospheres with hydrogen and maintained at a predetermined temperature. Silicon tetrachloride and hydrogen were then mixed in a molar ratio of 1, and the mixture was charged into the reaction tube. The mixed gas was mixed and preheated before introduction, and the mixed gas was introduced into the reaction tube under pressure to perform a reaction for producing trichlorosilane. The generated gas discharged from the reaction tube was heated under pressure with dry ice. After cooling to -70° C. with a refrigerant to condense the chlorosilanes and separate them from hydrogen, the condensate was collected and analyzed by gas chromatography. The reaction condensate is collected at regular time intervals, and the amount of silicon consumed by the reaction in a given time is determined from the analysis value (amount of trichlorosilane produced) using gas chromatography. The consumption rate, volume reduction, volume inside the reaction tube, and the average volume over a certain time interval were determined, and this average volume was divided by the flow rate calculated as an ideal gas for a mixed gas of hydrogen and silicon tetrachloride in a pressurized and heated state. The value was defined as the contact time for convenience.

As shown in Table 6, it was found that trichlorosilane was produced extremely efficiently under pressure even in the low temperature range.

Table 6 Reaction temperature Contact time sec TC3/(TC5+5
TC) 500 °C2026,6-01% 500 10 26.9500
5 26.8400 73
25, 1400 57
24.6400 30 25.6
400 13 21.6350
90 22.2350 T
o 22.1350 40
20.4350 20 14
．． 3 Comparative Example 3 Using the same reactor and the same gas introduction method as in Example 5, only silicon and copper metal or only silicon and cuprous chloride were used as the solid filler, and the composition was 10% relative to silicon.
They were mixed in such a manner that the amounts were % by weight, and a trichlorosilane production reaction was carried out using the same packing capacity and the same analytical method as in Example 5.

As shown in Table 7, both have extremely low activity compared to the catalyst components of the present invention (consisting of metallic copper or a copper compound, a molten salt of aluminum chloride, and a heteropolyacid); It can be seen that the catalyst component of the present invention is extremely effective even in reactions under pressure.

Table 7 Additives Reaction temperature Contact time TCS/ (TC3+5
TC) Cu only 500℃ 20sec 2
4.5 mo1%Cu only 500 10
20.2Cu only 500 7
15.0Cu only 350 120
7.0Cu only 350 100 5
．． 0Cu only 350 50 2.9
CuCI only 500 40 26.9C
uC1 only 500 20 23.6Cu
C1 only 500 10 18.0CuC
I only 350 120 7.2CuCI
Only 350 100 6.0CuCI only 350 50 3.2 Example 6 In a 200 m autoclave, 98% silicon was added to 30.
0g, 8.19g of Cu powder, NaCl-AI
After adding 10.8 g of C1x molten salt (1:1 mol ratio, melting temperature 200 ° C.), 10.3 g of silicon molybdic acid, and 90 g of silicon tetrachloride, the autoclave was further pressurized with 60 kg/cd of hydrogen, and then the autoclave was heated at 500 rpm. The temperature was raised to 220°C while stirring at a stirring speed of After cooling, the reaction solution was taken out and analyzed.

Generation of trichlorosilane was observed at TC5/(TC5+5TC)=8.4so1%.

Example 7 NaCl-AIC1z molten salt (1:2+sol ratio) was 9
．． The trichlorosilane production reaction was carried out under all the same reaction conditions as in Example 6, except that the amount was changed to 2 g.

Trichlorosilane became 8.5 mo1% in the reaction solution,
The reaction was not affected by the molten salt composition.

Effects of the Invention The present invention provides an extremely effective method for economically converting silicon tetrachloride into trichlorosilane, and a catalyst that can effectively carry out the conversion reaction.

The conventional conversion reaction of silicon tetrachloride to trichlorosilane is
Previously, the process had to be carried out at a high temperature of 500 to 600°C, but by carrying out the present invention and using a catalyst with high reaction activity, it was possible to conduct the reaction at an unprecedented temperature of 300°C.
It has become possible to carry out the conversion reaction smoothly and effectively even in a low temperature range of about 100 yen. In addition, in the present invention, since the catalyst component was successfully prevented from volatilizing, it became possible to carry out the reaction with high efficiency and constantly. More surprisingly, in the present invention,
The reaction can also be carried out using silicon tetrachloride in a liquid state below its critical temperature.

Also, as a matter of course, as a result of enabling the reaction at low temperature,
It has also become possible to significantly suppress corrosion of reactors, etc.

As described above, by carrying out the present invention, it is possible to reduce and downsize the reaction equipment from the viewpoint of its high reaction activity, to significantly reduce energy consumption compared to conventional methods from the viewpoint of its low-temperature high activity, and to perform the low-temperature reaction. From the perspective of suppressing corrosion of equipment, etc., it is possible to reduce material costs and extend the service life.In addition, from the perspective of suppressing volatilization of catalyst components, etc., it is possible to reduce material costs and reduce process troubles. Furthermore, it becomes possible to carry out the reaction in an extremely advantageous manner from an industrial standpoint.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. A method for producing trichlorosilane by reacting silicon tetrachloride and metallic silicon with hydrogen or hydrogen and hydrogen chloride, in which the silicon tetrachloride is in a liquid or gaseous state,
The reaction system is a gas-liquid-solid or gas-solid heterogeneous phase reaction, and the heterogeneous reaction is carried out in the presence of metallic copper and/or a copper compound, a molten salt of aluminum halide, and a heteropolyacid. A method for producing trichlorosilane, which is characterized by: 2. The method according to claim 1, wherein the molten salt of aluminum halide is comprised of aluminum halide and an alkali metal halide. 3. The method according to claim 1, wherein the aluminum halide is aluminum chloride. 4. The method according to claim 2, wherein the alkali metal halide is sodium or potassium chloride. 5. The method according to claim 1, wherein the heteropolyacid is mainly composed of an oxide of molybdenum and/or tungsten. 6. The method according to claim 5, wherein the heteropolyacid is heated and dehydrated at 300 to 600°C. 7. The method according to claim 1, wherein the copper compound is chlorinated copper.