JPH1095606A - Production of silicon trichloride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly selectively produce silicon trichloride without forming a large amount of silicon tetrachloride as a by-product by reacting metallic silicon with hydrogen chloride in the coexistence of a catalyst component and an alkali metallic compound. SOLUTION: (a) Metallic silicon is reacted with hydrogen chloride in the coexistence of (b) a metal of a group VIII element of the periodic table such as iron, cobalt, nickel, palladium or platinum or a chloride thereof and other catalyst components having catalyst activities in producing silicon trichloride therefrom in an amount of 0.05-40wt.%, expressed in terms of metallic element and based on the metallic silicon and (c) an alkali metallic compound such as a chloride, a sulfate or a nitrate of the alkali metal in an amount of 0.01-5wt.%, expressed in terms of metallic element and based on the metallic silicon at 250-300 deg.C to suppress the formation of silicon tetrachloride as a by- product and highly selectively produce the silicon trichloride.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing silicon trichloride. More specifically, the present invention relates to a method for producing silicon trichloride, which is useful as a raw material for producing polycrystalline silicon, by a selective reaction between metallic silicon and hydrogen chloride.

[0002]

2. Description of the Related Art Generally, silicon trichloride is produced by a method in which metallic silicon and hydrogen chloride are contacted and reacted in the presence of a catalyst component. As the catalytically active component, for example,
As described in JP-A-4768, iron compounds are effective. However, when the metal silicon species used as the reaction raw material is a metallurgical metal silicon or silicon iron containing a sufficient amount of an iron element component to exhibit catalytic activity, the reaction system between the metal silicon and hydrogen chloride is used. In addition, it is not necessary to newly add a catalytically active component such as an iron compound, and the reaction with hydrogen chloride is usually carried out using these metallic silicon species without adding a catalytic component. Further, in order to increase the reaction efficiency of gas-solid contact between metal silicon as a reaction raw material and hydrogen chloride, a fluidized bed reaction system is usually used.

[0003] In the reaction between metallic silicon and hydrogen chloride, when the reaction temperature is lower than about 400 ° C, silicon trichloride is mainly produced, but in addition, silicon tetrachloride and a trace amount of silicon dichloride are by-produced. .

[0004]

For the purpose of producing silicon trichloride, by-products of silicon tetrachloride and silicon dichloride are suppressed,
A method for selectively producing silicon trichloride is desirable in terms of productivity. However, according to the findings of the present inventors, when the amount of catalyst components such as iron compounds in the reaction system increases with the progress of the reaction, the side reaction for producing silicon tetrachloride further proceeds, and the production ratio of silicon trichloride, That is, it has been found that the selectivity is reduced and the production yield of silicon trichloride is reduced.

Further, since the reaction between metallic silicon and hydrogen chloride involves a large amount of heat, the temperature of the reaction layer rises rapidly with the progress of the reaction, and the side reaction for producing silicon tetrachloride becomes dominant, and It was found that the selectivity was reduced.

Therefore, it has been a major problem to develop a method for producing silicon trichloride in a highly selective manner without producing a large amount of silicon tetrachloride by-product in the reaction between metallic silicon and hydrogen chloride.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, in the reaction between metallic silicon and hydrogen chloride, in addition to a catalyst component such as an iron compound,
The inventors have found that silicon trichloride is selectively produced by coexisting a compound of an alkali metal element such as lithium, sodium, potassium, rubidium, and cesium in the reaction system, and completed the present invention.

That is, the present invention provides a method for producing silicon trichloride comprising reacting metallic silicon and hydrogen chloride in the presence of a catalyst component having catalytic activity for producing silicon trichloride and an alkali metal compound. It is a manufacturing method.

In the present invention, as the catalyst component having the catalytic activity of producing silicon trichloride from metal silicon and hydrogen chloride, known catalyst components having the above-mentioned actions can be used without any limitation. For example, iron, cobalt, nickel, palladium,
Compounds such as metals and chlorides of Group VIII elements such as platinum, and other metals and chlorides such as aluminum, copper, and titanium are exemplified.

The use amount of these catalyst components is preferably 0.05 to 40% by weight, and more preferably 0.1 to 5% by weight, based on the metal silicon, based on the metal element.

These catalyst components may be present by being added to the reaction system. However, when the metal silicon used contains the catalyst components such as the iron compound as impurities as impurities, these catalyst components may be used. Can be effectively used as the catalyst component. Of course, even when metal silicon containing a catalyst component as an impurity is used, there is no problem if the catalyst component is further added to the reaction system in order to increase the reactivity between the metal silicon and hydrogen chloride.

Here, as the metallic silicon, a known solid substance containing metallic silicon such as metallurgical metallic silicon, silicon iron, or polycrystalline polysilicon is used without any limitation. Further, there is no particular limitation on the components and contents of impurities such as iron compounds contained in the metallic silicon.

In the present invention, the hydrogen chloride to be used is used without any restriction even if nitrogen, hydrogen or the like is mixed therein. However, chlorosilane compounds of silicon trichloride, silicon tetrachloride or silicon dichloride are expected to react with moisture due to high hydrolyzability, thereby lowering the yield of silicon trichloride produced. Accordingly, the hydrogen chloride used in the present invention is preferably in a dry state. The supply rate of hydrogen chloride depends on the setting of the reaction temperature in terms of the reaction rate, but is preferably 0.5 to 50 cm / sec as the superficial velocity of the reactor.

In the present invention, an alkali metal compound is allowed to coexist in the reaction system in the reaction between metallic silicon and hydrogen chloride in the presence of the catalyst component. These alkali metal compounds do not necessarily have the same catalytic activity as the above-mentioned catalyst components such as the iron compound in the reaction between metallic silicon and hydrogen chloride, and do not show the reaction activity alone. However, in the reaction between metallic silicon and hydrogen chloride, a side reaction for producing silicon tetrachloride is suppressed, and the secondary catalyst has a secondary catalytic action for producing silicon trichloride with high selectivity. ,
With the above configuration, silicon trichloride can be produced very efficiently.

In the present invention, the alkali metal compound is
It is a compound of at least one element selected from elements classified into Group I of the periodic table, such as lithium, sodium, potassium, rubidium, and cesium. There is no problem even if these compounds are mixed and used. The compound form of the alkali metal compound is not particularly limited, but salts such as chlorides, sulfates, and nitrates are preferable from the viewpoint of easy handling. Specifically, lithium chloride, sodium chloride, potassium chloride, cesium chloride, sodium sulfate, potassium sulfate, sodium nitrate,
Potassium nitrate and the like can be mentioned.

In the present invention, the amount of these alkali metal compounds present in the reaction system is not particularly limited, but in consideration of the good selectivity of silicon trichloride formation, the amount of the alkali metal compound is reduced to the metal element relative to the metal silicon. Converted to 0.01 to 5
% By weight, preferably in the range of 0.1 to 3% by weight. In addition, even when the amount is in the above range, there is no phenomenon that particularly inhibits the reaction between the metal silicon and hydrogen chloride, but no further improvement effect on the selectivity of silicon trichloride generation is recognized and the efficiency is not efficient.

Next, in the present invention, when an alkali metal compound is added to a reaction system or when the above-mentioned catalyst component is newly added to a reaction system, a specific method of adding the catalyst component is as follows.
Usually, it is preferable that each component is mixed with metal silicon in advance and charged into the reaction system. On the other hand, when assuming continuous production of silicon trichloride, or assuming the use of a fluidized bed reactor, when taking out the reaction residue of metallic silicon out of the reaction system, or when removing silicon trichloride or the like, It is expected that the alkali metal compound or the catalyst component escapes out of the reaction system accompanying the reaction product gas, and the content of the alkali metal compound or the catalyst component in the reaction system decreases. Therefore, when metal silicon as a reaction raw material is charged into the reaction system, an alkali metal compound or a catalyst component is preliminarily mixed with metal silicon, and the amounts of these components in the reaction system are adjusted within the above range. preferable.

In the present invention, a known reactor such as a fixed-bed type or a fluidized-bed type is used without any limitation in relation to the contact system between metallic silicon and hydrogen chloride. As shown in the following examples, even in a fixed bed reactor, the alkali metal compound of the present invention imparts high selectivity to the production of silicon trichloride in the contact reaction between metallic silicon and hydrogen chloride. On the other hand, in the case of continuously producing silicon trichloride by continuously carrying out the contact reaction between metallic silicon and hydrogen chloride, solid metallic silicon is continuously or intermittently charged into the reactor and hydrogen chloride gas is supplied. Need to be in contact with In this case, a fluidized bed reactor is preferable for more efficiently bringing the catalyst component, alkali metal compound, metal silicon, and hydrogen chloride into contact with each other. In addition, since this reaction is an exothermic reaction, it is preferable to use a fluidized bed reactor in order to enhance the heat removal effect of reaction heat.

The reaction temperature is determined from the viewpoints of reaction control and reactor material from the viewpoints of reaction control and reactor material, because the selectivity of silicon trichloride formation tends to decrease as the reaction temperature increases, and the reaction is exothermic. ~ 500 ° C, preferably 250 ~
A range of 400 ° C. is preferred.

[0020]

According to the present invention, in the reaction between metal silicon and hydrogen chloride, the reaction between the metal silicon and hydrogen chloride is carried out by coexisting a catalyst component such as an iron compound and an alkali metal compound in the reaction system. Without inhibiting, the effect of suppressing the side reaction of silicon tetrachloride generation, which proceeds due to the increase in the content of the catalyst component in the system and the heat storage of the reaction heat, and the like, increases the selectivity (generation ratio) of silicon trichloride generation. Is expressed.

Further, according to the present invention, it is not necessary to strictly adjust the concentration of a catalyst component such as iron in the reaction system to a specific range in order to suppress the formation of silicon tetrachloride. As a result, the permissible temperature range of the reaction temperature control is widened, so that it is possible to stably produce silicon trichloride. Furthermore, the effect of the present invention is that various metal silicons can be used without limitation as the reaction raw material since there is no need to particularly limit the concentration of components such as iron in the metal silicon as the reaction raw material.

[0022]

The present invention will be described in more detail with reference to the following Examples, which by no means limit the scope of the present invention.

Example 1 and Comparative Example 1 In a quartz glass tube reactor having an inner diameter of 4 mm, metal silicon (iron 0.
After mixing and filling 25 g of sodium chloride as an alkali metal compound (corresponding to about 1% by weight of metallic silicon in terms of sodium element) into 1 g of the resulting mixture, the reactor was kept at 350 ° C. And a mixed gas of hydrogen chloride gas and nitrogen gas at a rate of 20 ml / min was continuously supplied to the reactor. The gas composition at the outlet of the reactor is analyzed by gas chromatography, and the reaction conversion (%) is calculated based on the amount of hydrogen chloride gas reduced, and the ratio of silicon trichloride in chlorosilanes formed such as silicon trichloride and silicon tetrachloride. Was calculated as silicon trichloride selectivity (%). The reaction reached a nearly steady state 20 minutes after the supply of the mixed gas of hydrogen chloride and nitrogen to the reactor was started, and the reaction conversion was 100%.
The selectivity for silicon trichloride was 92%.

For comparison, as Comparative Example 1, the same method as in Example 1 was carried out except that nothing was added to metallic silicon. In this contact reaction between metallic silicon and hydrogen chloride, the reaction conversion was 100%, and the selectivity to silicon trichloride was 86%.

In each of the following Examples and Comparative Examples, the reaction conversion of hydrogen chloride was approximately 100%. Therefore, in each table, only the formation selectivity of silicon trichloride was shown as the reaction result.

Examples 2 to 10 and Comparative Example 2 In Example 1, 225 mg of ferrous chloride (containing 10% by weight of metallic silicon in terms of element) was added to metallic silicon (containing 0.15% by weight of iron). Then, except that an alkali metal compound such as sodium chloride shown in Table 1 was added and mixed with metal silicon in the same amount as the element shown in Table 1,
A contact reaction between metallic silicon and hydrogen chloride was carried out in the same manner as in Example 1. The results are shown in Table 1.

As Comparative Example 2, 225 mg of ferrous chloride (metallic silicon 10
% By weight) except for adding and mixing.
The same method as described above was performed.

[0028]

[Table 1]

Examples 11 to 13 In Example 1, the reaction temperature was raised to 400 ° C., and metal silicon (containing 0.15% by weight of iron) was replaced with ferrous iron chloride.
25 mg (10% by weight of metal silicon in terms of element) was added and mixed, and an alkali metal compound such as sodium chloride shown in Table 2 was further added to and mixed with metal silicon in the same element conversion amount shown in Table 2. A contact reaction between metallic silicon and hydrogen chloride was carried out in the same manner as in Example 1. The results are shown in Table 2.

As Comparative Example 3, 225 mg of ferrous chloride (metallic silicon 10
% By weight) except for adding and mixing.
A method similar to 1 was performed.

[0031]

[Table 2]

Example 14 In Example 1, high-purity metallic silicon (purity 9%) was used in place of the metallic silicon (containing 0.15% by weight of iron) used.
Example 1 except that nickel metal powder as a catalyst component and sodium chloride as an alkali metal compound were added and mixed in an amount of 0.2% by weight with respect to silicon metal. The contact reaction between metallic silicon and hydrogen chloride was carried out in the same manner as described above. As a result, the reaction conversion was 100%, and the selectivity to silicon trichloride was 82%.

Comparative Example 4 A method similar to that of Example 1 was carried out without adding anything except that the nickel metal powder was added to and mixed with metallic silicon. As a result, the reaction conversion was 100%, and the silicon trichloride selectivity was 70%.

Comparative Example 5 The procedure of Example 14 was repeated, except that nothing was added to the metallic silicon. As a result, the reaction conversion of hydrogen chloride was almost 0%, and no silicon trichloride was produced.

Claims (1)

[Claims] 1. A process for producing silicon trichloride, comprising reacting metallic silicon and hydrogen chloride in the presence of a catalyst component having catalytic activity for producing silicon trichloride and an alkali metal compound therefrom.