JP2613262B2 - Method for producing trichlorosilane - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing trichlorosilane from silicon tetrachloride and hydrogen.

2. Description of the Related Art With the recent development of the electronics industry, demand for polycrystalline silicon, monosilane gas, and the like has been rapidly increasing, and it is expected that the demand will continue to increase in the future. Here, trichlorosilane is the most widely used as a raw material of the silicon substance. For example, high-purity polycrystalline silicon is produced by pyrolysis of trichlorosilane, and most of high-purity polycrystalline silicon worldwide is currently produced by this method. Recently, a method for producing monosilane by the disproportionation reaction of trichlorosilane is being put into practical use, and the importance of trichlorosilane will be greatly increased in the future. However, in these methods, trichlorosilane is consumed and a large amount of silicon tetrachloride is by-produced. For example, in the production of high-purity polycrystalline silicon by thermal decomposition of trichlorosilane, about 60% of trichlorosilane is by-produced as silicon tetrachloride, and in the production of monosilane by disproportionation of trichlorosilane, substantially, In addition, three times the mole of silicon tetrachloride as monosilane is by-produced. Therefore, by using this by-produced silicon tetrachloride as a raw material such as Aerosil, for example, a method of reducing the production price of trichlorosilane is known.However, the most excellent method of using silicon tetrachloride is, This is converted back to trichlorosilane,
It is to reuse as a raw material of the above method. For example, by converting silicon tetrachloride to trichlorosilane, the production of monosilane by disproportionation of trichlorosilane substantially results in a process of producing monosilane from metallic silicon and hydrogen, and this process has recently been put into practical use. is there.

Therefore, the technique of converting silicon tetrachloride to trichlorosilane is extremely useful, and in particular, it is extremely important to carry out this process inexpensively, simply, and efficiently in terms of the economy of the process.

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 with hydrogen at 1000 ° C. or higher.

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

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

Regarding the method (1), for example, Japanese Patent Application Laid-Open No. 57-3711 discloses a method in which hydrogen and silicon tetrachloride are sprayed at a temperature of 1100 to 1600 ° C. onto a heating element at the above-mentioned temperature.
% Yield. In JP-A-57-156318,
In the first stage, hydrogen and silicon tetrachloride are reacted at a temperature of 900 ° C. at a molar ratio of H ₂ / SiCl ₄ = 2 to obtain trichlorosilane in a yield of 25%. In JP-A-59-45920, trichlorosilane is obtained by reacting silicon tetrachloride with hydrogen in plasma. In JP-A-60-81010, 1200-1
Reaction of silicon tetrachloride and hydrogen in a temperature range of 400 ° C,
Trichlorosilane is obtained with a yield of about 30%.

It can be said that the method (2) is a thermally advantageous method in which the reaction proceeds at a relatively low temperature as compared with the method (1). The method of (3) using hydrogen chloride gas to promote the reaction more effectively by the method of (2) naturally has the same characteristics. For the methods (2) and (3), it is effective to use a catalyst, and a copper compound or metallic copper is used as the catalyst. For example, in JP-A-56-73617, a fluidized bed reaction is carried out at 350 to 600 ° C. using copper powder as a catalyst to obtain trichlorosilane. Also, in JP-A-58-11042,
The reaction is carried out using a catalyst supporting copper or supporting copper and nickel to obtain trichlorosilane.

In these methods, for example, in the method (1), trichlorosilane can be obtained at a considerably high conversion of silicon tetrachloride. In particular, in order to obtain trichlorosilane in a yield of 30% or more, at a high temperature of 1000 ° C. or more. The amount of heat consumed for performing the reaction is enormous. In addition, since it is a high-temperature reaction, it has severe drawbacks such as severe corrosion of reactors and the like by silicon chloride, and inevitably produces undesirable high-molecular-weight silicon chlorides as by-products. .

On the other hand, the methods (2) and (3) are also useful for producing trichlorosilane from a thermodynamic point of view. As described above, by-products are produced by the method for producing monosilane by disproportionation of trichlorosilane. The production of trichlorosilane from silicon tetrachloride is a very useful method, particularly since the method (2) essentially produces monosilane from metallic silicon and hydrogen. In the method (3), although the yield of trichlorosilane is large, hydrogen chloride does not participate in the conversion of silicon tetrachloride to trichlorosilane, and trichlorosilane is substantially synthesized from metal silicon. Becomes Therefore, from the viewpoint of recycling silicon tetrachloride, although the method is somewhat less useful than the method (2), it also has an advantage that the yield of trichlorosilane is large. It is desirable to exhibit its characteristics.

Furthermore, a process combining these methods (2) and (3) is also known (JP-A-60-36318). Among the above methods, the method (2) is the most excellent from the viewpoint of effective reuse of silicon tetrachloride, and the method (3) is also an excellent method from the viewpoint of formation of trichlorosilane. Hard to throw away. That is, the method (2) or (3) is highly economical, and especially the method (2) is currently being put to practical use as the method of choice.

However, in the method (2), the reaction is usually 500 to 6
The reaction is carried out at 00 ° C, and at a low temperature of about 300 ° C, the reaction hardly proceeds, and there is no example in which trichlorosilane is substantially generated. In addition, in the method (2), a gas-solid phase fluidized bed apparatus has conventionally been used for producing trichlorosilane in large quantities and continuously. However, since it is performed at a high temperature of 500 to 600 ° C., the raw material silane chloride is highly corrosive in a high temperature range, and corrosion of equipment becomes a serious problem in industrial production of trichlorosilane. There are many disadvantages to be solved for industrialization, such as a decrease in the selectivity of trichlorosilane due to the production of high-molecular-weight chlorosilanes and the use of a large amount of heat.

Problems to be Solved by the Invention The object of the present invention is to produce a trichlorosilane by reacting silicon tetrachloride with metallic silicon and hydrogen, and found a catalyst having a very high reaction activity as compared with a conventional catalyst.
It is an object of the present invention to provide an economically advantageous method for producing trichlorosilane very effectively even in a reaction temperature range of about ° C.

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, in the presence of a specific catalyst, production of polycrystalline silicon by thermal decomposition of trichlorosilane or unevenness of trichlorosilane. The present inventors have found an extremely economical method for effectively utilizing silicon tetrachloride by converting silicon tetrachloride by-produced in the production of monosilane by a chlorination reaction, and have completed the present invention.

That is, the present invention relates to a method for producing trichlorosilane by reacting silicon tetrachloride and metal silicon with hydrogen or hydrogen and hydrogen chloride, wherein the silicon tetrachloride is in a liquid or gaseous state, and the reaction system is gas-liquid. A method for producing trichlorosilane, comprising: performing a heterogeneous phase reaction of a solid or a gas and a solid, and performing the heterogeneous reaction in the presence of copper oxide and a metal oxide.

 Hereinafter, the present invention will be described in detail.

The conversion of silicon tetrachloride to trichlorosilane in the present invention is basically represented by the following formula: 3SiCl ₄ + 2H ₂ + Si → 4HSiCl ₃ (I) This reaction is an equilibrium reaction, and proceeds to the right as the temperature increases, the H ₂ / SiCl ₄ molar ratio increases, and the reaction pressure increases. When the temperature is higher than about 300 ° C., the equilibrium composition is not remarkably advantageous to trichlorosilane even if the temperature is increased, and rather, an excessive amount of heat has a greater economic effect. . So if possible 40
It is economical to perform in a low temperature range of 0 ° C. or lower. Here, there is no known example of producing trichlorosilane at a low temperature of around 400 ° C., but in the present invention, the above reaction is carried out in the presence of a mixture of copper oxide and metal oxide. By the thing,
This makes it possible to produce trichlorosilane even at a low temperature of about 300 ° C. And of course,
Means for increasing the yield of trichlorosilane by adding hydrogen chloride gas into the reaction system of the present invention may be employed.

The purity of the metal 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 economical point of view, it is preferable to use the former, since a sufficiently good result can be obtained with the former. The form of the metallic silicon is not limited, but it is recommended to use a powder having a large surface area from the viewpoint of the reaction rate. Of course, it is also possible to use it in another form such as a granular form.

The copper oxide and metal oxide used in the present invention will be described.

The purity of the copper oxide need not be particularly limited, and usually a commercially available product is sufficient. Further, precipitated copper and the like can be used. There is no particular limitation on the form, but it is preferable to use a powder from the viewpoint of the reaction rate and the like.

The metal oxide used in the present invention is represented by the metal element symbol C
It is a complete or partially chlorinated oxide of r, Mo, W, Fe, Co, Ni, Zn, Ag and Al. In the present invention, one or a mixture of two or more of these is mixed with copper oxide for use.

Further, a coprecipitated mixture obtained by an alkali coprecipitation method can be used as a mixture of the copper oxide and the metal oxide. Rather, it is preferable to use a coprecipitation method to obtain a uniform mixed state.

Next, a method for preparing a coprecipitated mixture of copper and another metal in the present invention will be described.

The preparation of mixed metal oxides by the coprecipitation method is generally performed by heating and calcining a coprecipitated hydroxide obtained by alkali-treating an aqueous solution of a metal nitrate or acetate with sodium carbonate or ammonia. Is done. Therefore, for preparing a mixed metal oxide by coprecipitation with copper and another metal, for example, the following method is recommended.

A predetermined amount of a mixed aqueous solution of copper nitrate and another one or two or more metals nitrate or copper acetate and another one or two or more metals acetate, preferably heated to 50 ° C or higher and 90 ° C or lower,
Stir. Next, an aqueous solution of sodium carbonate in excess of the same specified amount, preferably about 10%, as the total specified amount of nitrate groups or acetate groups contained in the aqueous solution is slowly added to the heated and stirred aqueous solution. Precipitate as oxide. After the addition of sodium carbonate, heating and stirring are continued for about 1 hour, then cooled to room temperature, and the deposited precipitate is collected by filtration. The precipitate is sufficiently washed with pure water, dehydrated and dried, and then heated to 150 ° C. or more in an electric furnace, preferably 300 to 600 ° C.
It can be prepared by a method such as heating to a mixed oxide of copper and another metal by heating at a temperature of ° C. However, it is needless to say that the present invention is not limited to these methods.

In the present invention, a heat treatment is performed in advance in the presence of hydrogen before using a mixture of the copper oxide and the metal oxide in the reaction. Heat treatment temperature is 150 ° C or higher, preferably 300 to 500
° C. In this case, this treatment may be performed after mixing with the metal silicon.

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

Although the conversion method is basically performed according to the above formula (I), in the present invention, the reaction is performed in a so-called gas-solid phase.
Performed in a solid phase heterogeneous reaction system. It is also possible to carry out a heterogeneous gas-liquid-solid reaction in a liquid state of silicon tetrachloride below the critical temperature of silicon tetrachloride. The hydrogen used for the reaction may be diluted with a medium (gas) inert to the reaction in advance, for example, argon, helium and / or nitrogen, etc., but hydrogen may be used from the viewpoints of reaction equilibrium, reaction rate and economy. It is preferred to use it alone. Normally, hydrogen may contain an expected impurity, and it is preferable to use hydrogen as a pressurized medium at the same time when performing a pressurized reaction. Further, under the reaction conditions, a solvent which is inactive (does not cause a reaction) to the starting materials, products, metal copper, aluminum halide, alkali metal halide, etc., for example, n
It is also possible to use aliphatic hydrocarbons such as -hexane and n-heptane, alicyclic hydrocarbons such as cyclohexane and cyclooctane, and aromatic hydrocarbons such as benzene and toluene.

Although the reaction temperature is not specified, the reaction temperature is substantially 150 ° C. or higher, preferably 200 to
Performing at 650 ° C. is preferable from the viewpoint of reaction equilibrium and further from the viewpoint of reaction rate. It is to be noted that trichlorosilane having a reaction equilibrium amount or less may be mixed in the silicon tetrachloride charged as a raw material when performing this reaction.This is because silicon trichloride produced by the reaction is separated by distillation or the like. Meaning that trichlorosilane can be used even if trichlorosilane remains therein, but it is preferable to use silicon tetrachloride having a trichlorosilane content as small as possible on the reaction equilibrium, thereby substantially reducing the amount of trichlorosilane produced. More and more desirable.

Next, the amounts of the raw materials, copper oxide and metal oxide used in the present invention will be described. The amount of the metal silicon used in the present invention is not particularly limited. However, when the reaction is carried out in a batch system, the reaction is preferably carried out using 1% by weight or more based on silicon tetrachloride. At the same time, metal silicon is consumed, and the reaction may not be performed effectively. The amount of copper oxide is not particularly limited, but the metal atom ratio (g-atms / g-atms) to the charged metal silicon is 0.5%.
The reaction is preferably performed as described above, and the reaction is preferably performed at an atomic ratio of 0.5% or more of the metal oxide to the charged metal silicon. Although there is no particular problem even if the reaction is carried out in an amount less than this, the effect added to the reaction is unlikely to appear significantly.

In the present invention, the mixture of copper oxide and metal oxide is preferably subjected to a heat reduction treatment with hydrogen in advance. The reason for this is that copper oxide is reduced by hydrogen in the reaction of the present invention and produces water which decomposes chlorosilanes as a raw material and a reaction product. Things are preferred. However, if these mixtures are not used in large quantities, this operation is not so necessary. In the reduction, hydrogen may be used alone or diluted with a medium (such as a gas) inert to these metals. Further, the temperature for carrying out the reduction is preferably the temperature at which the reaction is usually carried out.

Next, specific modes for carrying out the present invention will be described. As described above, the reaction in the present invention is preferably performed at 150 ° C. or higher, and further pressurized (preferably hydrogen pressurized).
It is preferable to carry out the reaction in a state, and it is also possible to carry out the reaction by a flow reaction method or a batch reaction.

Although there is no particular limitation on the method of implementation in the present invention, the following methods are mentioned as methods that are easy to implement. In this case, it is preferable to use the mixture of copper oxide and metal oxide after performing a heat reduction treatment with hydrogen so as not to adversely affect the reaction and the like as much as possible. Of course, the present invention is not limited to these methods.

(1) A method in which a predetermined amount of silicon tetrachloride, metal silicon, copper oxide and metal oxide mixed in advance are placed in an autoclave, and then pressurized to a predetermined pressure with hydrogen, and then a heating and stirring reaction is performed.

(2) A predetermined amount of silicon tetrachloride, metal silicon, premixed copper oxide and metal oxide are continuously introduced into a pressurized reactor previously maintained at a predetermined temperature and a predetermined pressure with hydrogen to perform a reaction. Method.

(3) Put silicon metal in advance and copper oxide and metal oxide mixed in advance in a reactor, and while maintaining a predetermined temperature, continuously introduce silicon tetrachloride and hydrogen by pressurizing hydrogen and continuously produce gas. A method in which a reaction is carried out while being extracted, and metal silicon, copper oxide and metal oxide are introduced intermittently or continuously as required.

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples.

Example 1 Preparation of catalyst The catalyst used in Example 1 was prepared as follows.

While an aqueous solution (equimolar mixture) of cupric nitrate and various metal nitrates was heated and stirred at 85 ° C., an equivalent amount of sodium carbonate with respect to all nitrate groups was gradually added to this aqueous solution. After the addition was completed, the temperature was kept at 85 ° C. for about 1 hour, and the stirring was continued. After cooling, the precipitated precipitate is separated by filtration.
The filtered solid was thoroughly washed with pure water and dried at 100 ° C.
After that, heat gradually from 150 ° C and finally at 400 ° C.
It was heated for a time and fired. This was used as a catalyst.

In a Pyrex reaction tube with an inner diameter of 11 mm attached with a glass filter at the bottom to hold solids, a baked mixture of copper oxide and various metal oxides was added to silicon (98% purity, about 200 mesh). And the reaction tube was filled with 2.1 ml, and the mixture was fixed with silica wool. After sufficiently replacing the inside of the reaction tube with helium, hydrogen was introduced while heating the reaction tube to 500 ° C., and a reduction operation of the catalyst component was performed for 1 hour.
The silicon tetrachloride was kept at 0 ° C., bubbled with hydrogen at a predetermined flow rate, and introduced into the reaction tube together with hydrogen as a mixed gas (H ₂ / SiCl ₄ mo calculated from the vapor pressure of silicon tetrachloride).
The l ratio was 9.3. ). The reaction tube was maintained at a predetermined temperature to carry out a reaction for producing trichlorosilane.

The reaction results were obtained by gas chromatography analysis of the exhaust gas from the reaction tube.

As shown in Table 1, very excellent reaction results were obtained even in the low-temperature reaction. In addition, the value of the reaction product gas composition is a value after the reaction becomes steady. Further, the raw material mixed gas was used as an ideal gas, the volume expansion due to the temperature rise was calculated, the flow rate of the mixed gas at a predetermined temperature was calculated, and the value obtained by dividing the solid volume by this flow rate was appropriately used as the upper contact time.

Example 2 A three-component precipitate was prepared from an aqueous solution to which equimolar amounts of nitrates of copper, chromium and zinc were respectively added, in the same manner as in Example 1, and calcined to obtain a three-component equimolar mixed oxide. It was prepared, mixed with a composition of 10 wt% with respect to metal silicon, and trichlorosilane was produced by the same reaction apparatus and the same reaction method as in Example 1.

As shown in Table 2, a reaction activity in which a ternary mixed oxide may be used was observed.

Comparative Example 1 The same volume of a solid mixture to which copper oxide or chromium oxide (CuO or Cr ₂ O ₃ ) was added in an amount of 10 wt% with respect to silicon was filled in the same reaction tube as in Example 1,
A blank test was performed by performing a reaction for producing trichlorosilane by the same reaction method as in Example 1.

As shown in Table 3, the activity was extremely low as compared with the results of Examples 1 and 2, indicating that the catalyst component of the present invention is effective for this reaction. However, the oxide used was the one that was precipitated and fired in the same manner as in Example 1.

Comparative Example 2 The same volume as in Example 1 was filled in the same reaction tube as in Example 1 with a solid mixture containing 10 wt% of metallic copper or copper chloride with respect to silicon, and trichlorosilane was reacted in the same manner as in Example 1. Was produced.

As shown in Table 4, the activity is very low as compared with the catalyst of the present invention, and it is understood that the catalyst of the present invention is excellent.

Example 3 The same ternary oxide as in Example 2 was added in amounts of 5 and 2 wt% with respect to silicon, respectively, to reduce the amount of catalyst. Was.

As shown in Table 5, it was found that even if the amount of the catalyst was reduced to (1/2), the reaction results were not affected at all, and even if the amount was reduced to (1/5), the present invention was carried out without much influence. did.

 For comparison, the results of Example 2 are also listed.

Example 4 Commercially available chemical reagents of copper oxide (CuO), zinc oxide (ZnO) and chromium oxide (Cr ₂ O ₃ ) were mixed in an equimolar amount in a mortar, and the mixed oxide was mixed with silicon. Ten
The same reaction tube as in Examples 1 to 3 was charged with the same volume as that mixed with silicon powder so as to be wt%, and
After hydrogen reduction in the same manner as described above, a production reaction of trichlorosilane was performed by the same reaction method.

As shown in Table 6, formation of trichlorosilane was recognized with good results.

Example 5 Copper oxide and aluminum oxide (Al
₂ O ₃ ) and molybdenum oxide (MoO ₃ ) are mixed well in a mortar so as to be equal to each metal atom, and copper oxide, aluminum oxide and nickel oxide are mixed so as to be equal to each metal atom. The resulting mixture was mixed at 10 wt% with respect to silicon, and then filled in the same reaction tube as in Examples 1 to 4 with the same volume, and the same reduction operation and the same reaction method were used to prepare trichlorosilane. A production reaction was performed.

As shown in Table 7, good reaction results were obtained with each catalyst.

Example 6 Using copper, chromium and zinc nitrates, Example 2
The mixture was precipitated and calcined in the same manner as described above to prepare a ternary mixed oxide, which was then mixed with silicon so that each of the ternary mixed oxides was 10 wt% with respect to silicon. Each mixture was subjected to a reduction treatment in the same manner as in Example 2 using a mixture having a different catalyst composition, and then trichlorosilane was produced by the same reaction method as in Example 2.

As shown in Table 8, good catalytic activity was exhibited in a wide range for each composition. For comparison, some results of Example 2 are also listed.

Example 7 A mixed oxide composed of exactly the same method and the same three components as in Example 2 was prepared and calcined, and after previously subjected to a reduction treatment at 500 ° C. for 1 hour with hydrogen without mixing with silicon (reduction The weight loss due to the treatment was 17.5 wt%), and this was mixed with silicon so that the weight before the reduction treatment was 10 wt% with respect to silicon, and then the reaction for producing trichlorosilane was carried out in the same manner as in Example 2. Was.

As shown in Table 9, the results were almost the same as the results of Example 2. Therefore, the catalyst reduction treatment does not always need to be performed after mixing with silicon.

Example 8 In a 200 ml autoclave, 8.2 g of a mixed oxide of copper, chromium and zinc prepared and reduced in the same manner as in Example 7, and 30.0 g of 98% silicon were prepared.
And 90 g of silicon tetrachloride, pressurized to 60 kg / cm ² G with hydrogen, and then heated to 220 ° C. while stirring at a stirring speed of 500 rpm.
The production reaction of trichlorosilane was performed for a long time. After the completion of the reaction, the reaction solution was taken out while cooling the autoclave to 5 ° C. and analyzed.

When TCS / (TCS + STC) = 5.2 mol%, formation of trichlorosilane was observed.

The present invention is a very effective method for economically converting silicon tetrachloride to trichlorosilane, and provides a catalyst capable of effectively performing the conversion reaction.

Conventionally, the conversion reaction of silicon tetrachloride into trichlorosilane had to be performed at a high temperature of 500 to 600 ° C., but by carrying out the present invention, a catalyst having the high reaction activity was used. Even in a low temperature range of about 300 to 400 ° C., the conversion reaction can be performed smoothly and effectively. More surprisingly, in the present invention,
The reaction can be carried out with silicon tetrachloride in a liquid state below its critical temperature.

Naturally, since the reaction can be performed at a low temperature, the corrosion of the reaction apparatus and the like can be largely suppressed.

By carrying out the present invention as described above, the reaction equipment is reduced and downsized from the viewpoint of its high reaction activity, the energy is significantly reduced as compared with the conventional method from the viewpoint of its low temperature and high activity, From the viewpoint of suppressing corrosion due to the execution of the reaction, the reaction can be performed extremely advantageously both economically and industrially, for example, by reducing material costs and extending the service life.

Claims (4)

(57) [Claims] 1. A method for producing trichlorosilane by reacting silicon tetrachloride and metallic silicon with hydrogen or hydrogen and hydrogen chloride, wherein said silicon tetrachloride is in a liquid or gaseous state, and said reaction system is gas-liquid- A process for producing trichlorosilane, comprising a solid or gas-solid heterogeneous phase reaction, and the heterogeneous reaction being carried out in the presence of copper oxide and a metal oxide. 2. The method according to claim 1, wherein the metal oxide is iron, nickel, cobalt, chromium, molybdenum, tungsten, aluminum,
2. The method according to claim 1, which is an oxide of silver or zinc. 3. The method according to claim 1, wherein the copper oxide and the metal oxide are heat-treated at 300 to 500 ° C. in the presence of hydrogen. 4. The method according to claim 1, wherein the copper oxide and the metal oxide are coprecipitated with an alkali.