JP2002069078A - Method for producing silane from trialkoxysilane and method for producing trialkoxysilane from tetraalkoxysilane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a silane from a trialkoxysilane by the vapor-phase reaction in high reaction result at a low cost by converting a tetraalkoxysilane into the trialkoxysilane and enabling the use of the product as a raw material for the production of silane and provide a method for producing a trialkoxysilane from a tetraalkoxysilane. SOLUTION: A vapor-phase reaction of silicon with an alcohol is carried out in the 1st reaction step to produce a trialkoxysilane, the trialkoxysilane is subjected to disproportionation reaction in the 2nd reaction step to form a silane, the tetraalkoxysilane formed as a by-product in the formation of silane is converted into the trialkoxysilane in the 3rd reaction step and the obtained trialkoxysilane is recycled as a raw material of the 2nd reaction step. As an alternative, the tetraalkoxysilane is made to react with silicon and hydrogen to form the trialkoxysilane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing silane, and more particularly to a method for converting trialkoxysilane into tetraalkoxysilane which is effective in reducing the cost of production equipment and operating costs and which is produced as a by-product in the production of silane. The present invention relates to a method for producing silane from trialkoxysilane which is converted and used again for producing silane, and a method for producing trialkoxysilane from tetraalkoxysilane.

[0002]

2. Description of the Related Art High-purity silicon for semiconductors and solar cells is obtained by converting silicon obtained by reducing an ore, such as silica stone and silica sand, into an arc furnace and converting it to a chlorine compound (trichlorosilane). Later, it is produced by reduction or thermal decomposition again.

However, in this method, since chlorine is used at a high temperature, the cost of manufacturing equipment and products is increased due to measures against corrosion of materials and equipment, environmental measures such as recovery equipment and processing equipment for hydrochloric acid, and the like. Was inevitable, and the technical challenges were also great.

Therefore, a method of producing high-purity silicon by a method not using halogen such as chlorine has been studied, and a method by the following process has been studied.

[0005] That is, as a process for producing high-purity silicon, (1) synthesis of trialkoxysilane by reaction of silicon with an alcohol such as methanol or ethanol. (2) Production of silane by disproportionation reaction of trialkoxysilane. Producing silane using a two-step process of
This is a method of producing high-purity silicon using this silane as a raw material.

[0006]

In order for a method of producing high-purity silicon using this two-stage process to be economically efficient, it is necessary to produce trialkoxysilane at low cost and to obtain trialkoxysilane. It is a necessary condition that the reaction result of the disproportionation reaction is high and that the tetraalkoxysilane by-produced in a large amount in the disproportionation reaction is effectively used.

However, many patents using the liquid phase method for these reaction processes have been filed, but the liquid phase method has a drawback that the conversion is relatively high but the reaction rate is slower than the gas phase method. Was.

The silane as a reaction product aimed at by the present invention is dissolved in a mixture of a trialkoxysilane as a raw material and a tetraalkoxysilane as another reaction product. The yield of silane was easily reduced, and it was necessary to separate tetraalkoxysilane from the starting material, trialkoxysilane, by a method such as distillation.

For this reason, it is difficult to obtain an efficient reaction result,
Further, complicated operations such as separation and recovery of a raw material product and a catalyst are required, so that there is a problem that the production cost is high.

[0010] On the other hand, the gas phase method has an advantage that the reaction rate is potentially higher than the liquid phase method, but it has been considered that the selectivity is low and industrialization is difficult.

Further, there is a problem that trialkoxysilane is hydrolyzed by water contained in the raw material trialkoxysilane to form silica, and water is adsorbed on the catalyst to lower the catalytic activity.

In addition, when silane is produced from trialkoxysilane, tetraalkoxysilane is produced in a molar ratio of 3 with respect to 1 silane, and it is difficult to say that silane can always be produced with a high yield. It was further believed that tetraalkoxysilanes could not be converted to trialkoxysilanes.

Therefore, in the present invention, a trialkoxysilane which can be used as a raw material for converting tetraalkoxysilane to trialkoxysilane and having a high reaction performance at a low cost by the vapor phase method and producing silane again is used. An object of the present invention is to provide a method for producing silane and a method for producing trialkoxysilane from tetraalkoxysilane.

[0014]

According to the silane production method of the present invention, a second reaction step for producing silane and tetraalkoxysilane by a disproportionation reaction of trialkoxysilane; And a third reaction step to be generated.

According to this structure, silane can be produced without passing through a halide, so that it is excellent in environmental measures and safety measures, and the production cost can be kept low.

In addition, since the method includes the first reaction step of producing a trialkoxysilane by reacting silicon with an alcohol in a gas phase, an alkoxysilane having a very low impurity concentration can be easily produced. And high purity silane can be provided at low cost.

Further, by providing a step of removing an oxide formed on the surface of silicon, high catalytic reaction activity can be obtained.

Further, by providing a step of bringing silicon and a copper compound into contact with each other and performing a heat treatment, high catalytic activity can be maintained for a long period of time.

In the present invention, since a metal reactor can be used, it is very useful for industrially producing silane.

In addition, by providing a step of performing heat treatment on the catalyst with reduced catalytic activity to regenerate the catalyst, the catalyst can be used for a long time, so that the production cost of silane can be reduced.

Here, a catalyst obtained by supporting potassium fluoride or hydrotalcite on alumina or zirconia can be used.

In the second reaction step, one or both of the produced silane and tetraalkoxysilane are quickly separated from the reaction step, so that the disproportionation reaction of trialkoxysilane is promoted and the production of silane is promoted. can do.

Next, the tetraalkoxysilane is brought into contact with silicon and hydrogen to produce trialkoxysilane, so that the tetraalkoxysilane produced in the silane producing step or the like can be converted into trialkoxysilane. , The silane yield can be improved.

Here, by performing the production reaction under high pressure, the conversion of tetraalkoxysilane to trialkoxysilane can be improved.

Further, the method includes a step of removing an oxide formed on the surface of silicon, and a step of performing heat treatment by bringing silicon into contact with a copper compound as a catalyst. Conversion rate can be improved.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the overall structure of a silane producing method according to the present invention.

In the present invention, first, in a first reaction step 10, an alcohol such as methanol or ethanol is reacted with silicon using a catalyst to produce trialkoxysilane, hydrogen, and by-product tetraalkoxysilane.

In the figures, the alcohol is represented by "R-
OH "and an alkoxyl group are shown as" RO ".

Then, in a first separation step 40, hydrogen, trialkoxysilane, tetraalkoxysilane and unreacted alcohol are separated from the product in the first reaction step 10, and the alcohol separated in this step is again subjected to second separation. Hydrogen and tetraalkoxysilane are utilized in one reaction step 10 and third reaction step 30.

The trialkoxysilane is sent to the second reaction step 20, where silane and tetraalkoxysilane are produced by a reaction using a catalyst.
At 0, the product silane, tetraalkoxysilane and unreacted trialkoxysilane are separated.

The unreacted trialkoxysilane separated in this separation step is used again in the second reaction step 20,
The tetraalkoxysilane is sent to the third reaction step 30.

In the third reaction step 30, tetraalkoxysilane is reacted with hydrogen and silicon to generate and separate trialkoxysilane (third separation step 60).

By using a catalyst in the third reaction step, the production rate of trialkoxysilane can be accelerated.

Then, the trialkoxysilane is sent to the second reaction step and is used for producing silane.

The overall structure of the present invention comprises the following three structures. (1) Trialkoxysilane is generated from silicon and alcohol (first reaction step). (2) Generate silane from trialkoxysilane (second reaction step). (3) Convert tetraalkoxysilane to trialkoxysilane (third reaction step).

In FIG. 1, the reaction product is separated for each reaction step.
When the amount of tetraalkoxysilane produced and the amount of unreacted alcohol are small, as shown in FIG. 5, alcohol and hydrogen are separated in the first reaction step and the second reaction step 2
A configuration in which trialkoxysilane is supplied to 0 without being separated from tetraalkoxysilane can also be adopted.

Further, a configuration in which the product in the third reaction step is supplied to the second reaction step without separation, or a configuration (not shown) in which the second separation step is used instead of the third separation step can be adopted.

As shown in FIG. 6, the products generated in the respective reaction steps are collectively separated in a fourth separation step 70, and the products are supplied to a step using each separated product as a raw material. It is also possible to adopt a configuration in which

Hereinafter, each configuration will be described in detail using the first to third embodiments.

FIG. 2 is a block diagram showing a first embodiment for producing trialkoxysilane from silicon and alcohol.

In the present embodiment, silicon and alcohol (methanol or ethanol) are allowed to undergo a gas phase reaction,
Produce trialkoxysilane (trimethoxysilane or triethoxysilane) as a raw material of silane.

At this time, when methanol is used, the reaction formula is as follows: The reaction formula using ethanol is Becomes

Note that the silicon used in the present embodiment is not limited to high-purity silicon, but metal silicon or the like can also be used.

First, an oxide film formed inevitably close to silicon as a raw material is etched using hydrogen fluoride or the like to expose the surface of silicon, and then is exposed to copper chloride as a catalyst in a non-oxidizing atmosphere. Heat treatment is performed and alloying treatment is performed.

Here, the heat treatment is performed at a temperature range of 180 ° C.
To 280 ° C, and the processing time is within 5 hours.

Then, by causing a gas phase reaction with the alcohol, copper in copper silylene, which is a silicon alloy nucleus, is replaced with a functional group in the alcohol, and trialkoxysilane is generated.

Here, the temperature range in the gas phase reaction is 1
The temperature is from 80 ° C. to 285 ° C., and the flow rate of the alcohol vapor is 1 to 70 L / h, preferably 2 to 160 L / h per 1 g of silicon at normal temperature and normal pressure.

Further, under the conditions of the present embodiment, the generated trialkoxysilane is a gas, so that the silicon in the silicon copper alloy (copper silylene) is transformed into trialkoxysilane by a reaction, and After detaching from the surface, copper silylene is newly formed on the silicon surface, and trialkoxysilane is formed by a similar reaction mechanism.

Here, the trialkoxysilane is separated from other products by a separation step 12 using a known method such as distillation.

In the present embodiment, it is desirable that the particle size of the copper chloride catalyst is equal to or smaller than that of silicon.

This is because the alloying treatment forms at least 95, preferably at least 125, copper silylenes as alloy nuclei per square millimeter on the surface of silicon.
This is because it is desirable that the number of contact points between silicon and the catalyst be large and that the reaction area of the alloy nucleus generated be large.

Here, a copper compound which forms a copper silylene species such as copper hydroxide can be used as a catalyst instead of copper chloride.

In the alloying operation, any of a fixed bed in which silicon and a catalyst are in a stationary state, and a moving bed or a fluidized bed in a moving state can be used.

Although the particle-particle contact method has been described as a method of forming the alloy nucleus, the silicon alloy nucleus may be formed on the surface of silicon using a gas-solid reaction using a catalyst vapor.

Further, by dissolving the catalyst in a liquid, immersing silicon in the solution, and drying the solution,
A catalyst may be deposited on the surface of silicon to form a silicon alloy core.

After the trialkoxysilane is generated, the supply of silicon to the silicon alloy nucleus for forming new copper silylene is performed by solid-phase diffusion. Preferably shorter,
The size of the alloy nucleus is 5 μm or less, preferably 1 μm or less.

Since it is necessary to balance the rate of silicon consumption by the trialkoxysilane synthesis reaction and the rate of silicon supply by diffusion, an excessive reaction rate must be avoided. Strict control is required so as not to exceed the stated temperature range.

This is because any one of the following problems occurs when the reaction temperature exceeds this temperature range. (1) Since the growth rate of alloy nuclei increases with an increase in the temperature of the alloying treatment, the balance between the consumption rate of silicon due to the formation of trialkoxysilane and the supply rate of silicon due to solid-phase diffusion is lost, and this is suitable for the reaction. An alloy core having a size exceeding the size is formed. (2) As the reaction temperature increases, the consumption rate of silicon due to the generation of trialkoxysilane increases, and significantly exceeds the supply rate of silicon to the alloy nucleus, thereby maintaining the size of the alloy nucleus at an appropriate size. Difficult to do,
The selectivity of trialkoxysilane decreases.

The problem (1) tends to occur in the pretreatment step, and the problem (2) tends to occur in the reaction step.

Next, FIG. 3 is a block diagram showing a second embodiment for producing silane from trialkoxysilane.

In this embodiment, silane is produced by a disproportionation reaction of trialkoxysilane.

At this time, the reaction formula is: Or Becomes

First, a basic compound such as potassium fluoride or hydrotalcite is supported on alumina or zirconia powder to form a catalyst.

Here, as a pretreatment, the catalyst is placed in a non-oxidizing atmosphere at 200 ° C. to 400 ° C., preferably 250 ° C. to 35 ° C.
The heat treatment is performed in a temperature range of 0 ° C. for 5 minutes or more, preferably 30 minutes or more.

The raw material trialkoxysilane is subjected to a dehydration treatment or the like to reduce the amount of water contained therein to 3,000.
ppm or less, preferably 500 ppm or less.

Then, a trialkoxysilane is brought into contact with a catalyst to produce silane by a disproportionation reaction.

At this time, it is desirable to carry out the reaction at a temperature as low as possible within a temperature range where condensation does not occur under reaction conditions such as pressure while maintaining the gaseous phase of the tetraalkoxysilane. In the case of silane, it is 120 to 250 ° C under normal pressure, preferably 120 to 250 ° C.
150 ° C, in the case of triethoxysilane, 16
The reaction is carried out at a temperature in the range of 6 to 300C, preferably 166 to 200C.

The generated silane is separated from other products by a separation step 22 using a known method such as distillation.

When the catalyst activity decreases, the catalyst is regenerated by performing a heat treatment in a non-oxidizing atmosphere at a temperature range of 250 ° C. to 300 ° C. for 30 minutes to 1 hour.

In the present embodiment, by mixing a non-condensable gas or reducing the pressure of the reaction system, it is possible to maintain a low temperature, avoid condensation, and improve the conversion.

In addition, since the reaction product is generated by using the disproportionation reaction, either or both of the reaction product gas, silane and tetraalkoxysilane, is generated from the reaction system by a method such as membrane separation. By separating quickly, the conversion can be improved.

In this embodiment, the fixed layer, the moving layer,
Any of the fluidized beds may be used as a reactor, but a fixed bed is industrially preferable because of a long catalyst life and easy regeneration.

FIG. 4 is a block diagram showing a third embodiment for converting tetraalkoxysilane to trialkoxysilane.

In this embodiment, silicon is reacted with tetraalkoxysilane (tetramethoxysilane or tetraethoxysilane) to produce trialkoxysilane (trimethoxysilane or triethoxysilane) as a silane raw material.

At this time, the reaction formula is as follows: Or Becomes

First, an alloying process is performed using the same method as in the first embodiment to form an alloy nucleus on the surface of silicon.

Then, a mixed gas of tetraalkoxysilane and hydrogen is brought into contact with silicon to cause a gas phase reaction to generate trialkoxysilane.

In this reaction, since the conversion increases as the reaction temperature increases, for example, a gaseous phase reaction is performed at a temperature range of 200 ° C. to 550 ° C., preferably 300 ° C. to 450 ° C. at normal pressure. In addition, it is desirable that the temperature is high and the pressure is high as long as the trialkoxysilane does not thermally decompose. In this case, there is no problem even if the gas phase cannot be maintained and the liquid phase condition is reached.

Further, as suggested by the above reaction formula, since this reaction is a reaction in which the number of moles is reduced, it is desirable to carry out the formation reaction of trialkoxysilane under a high pressure.

In the case where an oxide is formed on the surface of silicon as a reaction raw material, the oxide is removed in advance before performing an alloying treatment or the like.

As a method for removing the oxide, for example,
An etching treatment using hydrogen fluoride, hydrofluoric acid, or a mixture containing them is effective, and it is preferable that the removal of the oxide by this etching treatment or the like be performed more sufficiently than in the synthesis of trialkoxysilane.

The etching method may be either a wet method or a dry method. In the case of using the wet method, for example, the silicon surface is exposed to a reduced pressure of 600 mmHg by a method such as exposing the silicon surface to a reduced pressure of 600 mmHg. The concentration is 1000pp
m or less, preferably 500 ppm or less. This operation is also applicable to trialkoxysilane synthesis, but it is necessary to perform sufficient dehydration.

In the conversion of tetraalkoxysilane to trialkoxysilane, the progress of the reaction is slower than in the synthesis of trialkoxysilane. Therefore, 100 or more, preferably 130 or more copper silylenes per square mm are used. In addition, it is desirable to form a large number of fine catalyst alloy nuclei more than in the case of trialkoxysilane synthesis, and the size of the catalyst alloy nuclei is preferably 10 μm or less.

Incidentally, the alloying treatment step may be carried out independently as a pretreatment operation before the conversion reaction from tetraalkoxysilane to trialkoxysilane, or may occur automatically simultaneously with the reaction in the reactor. You may implement by making it do.

The conversion from tetraalkoxysilane to trialkoxysilane is preferably as large as possible.
Industrially 5% or more, preferably at least 10-20
A conversion of about% is desired.

The necessary amount of hydrogen as a reaction raw material is stoichiometrically 2/3 of that of tetraalkoxysilane, but by supplying an excess of about 1 to 10 times the amount of tetraalkoxysilane, The conversion reaction from tetraalkoxysilane to trialkoxysilane can be promoted.

The trialkoxysilane is separated from other products by a separation step 32 using a known method such as distillation.

Hereinafter, the first embodiment will be described using Examples 1 to 15 and Comparative Example 1, and the second embodiment will be described using Examples 22 and 23 using Examples 16 to 21.
The third embodiment will be described in detail with reference to FIG.

[0089]

Example 1 In this example, metallic silicon (manufactured by Yamaishi Metal, purity 98%) was sieved to 45 to 68 μm, washed with ion-exchanged water, and 5 g of this metallic silicon was treated with hydrofluoric acid (Hirota Chemical Industries, Ltd.). After stirring for 1 hour in 50 ml of Teflon (registered trademark) beaker, the solution in a Teflon (registered trademark) beaker was filtered, washed with ion-exchanged water, and then decompressed (6
The resultant was dried to a residual moisture of 500 ppm or less using a drying method (40 mHg) (hereinafter referred to as “HF treatment”).

Then, 0.18 g of a mixture obtained by mixing HF-treated metal silicon and cuprous chloride (manufactured by Wako Pure Chemical Industries, Ltd.) for 10 minutes was added to a fixed-bed reactor (Pyrex (registered trademark) glass, inner diameter 8 mm) ), And the reactor is
Heating was performed at 40 ° C., and helium gas was passed at a flow rate of 8.0 NL / h for 1 hour to perform heat treatment.

Here, the catalyst concentration of the catalyst formed by mixing metallic silicon and cuprous chloride is expressed by the following equation. According to the above equation, adjustment is performed so that the catalyst concentration becomes 1 to 15 wt%.

After the heat treatment, while maintaining the reactor temperature at 240 ° C., methanol was supplied at a flow rate of 54 mmol / h to synthesize trimethoxysilane.

Here, the partial pressure of methanol was previously 60 kP
The flow rate of the helium gas was adjusted so as to be a.

The gas discharged from the outlet of the reactor was introduced into a gas chromatograph (filler SE-30, column length 2 m, column temperature 150 ° C.), and the product was removed every 2.5 minutes. Analysis was carried out.

As a result, the formation of a methoxysilane compound was observed without an induction period (initial maximum formation rate: 18 mmol / h), and no formation of methoxysilane was observed 3 hours after the start of the reaction.

At this time, the conversion of metal silicon is 85%,
The selectivity of trimethoxysilane was 99.8%, and the only methoxysilane product other than trimethoxysilane was tetramethoxysilane.

[0097]

Comparative Example 1 Except for not performing HF treatment on metallic silicon,
The reaction was carried out under the same treatment and reaction conditions as in Example 1, and the reaction product was analyzed.

After an induction period of about 30 minutes, formation of methoxysilane was observed, but the formation rate was up to about 1 mmol /
h, which was much smaller than that of Example 1.

Up to 9 hours after the start of the reaction, the conversion of metallic silicon was 29%, and the selectivity for trimethoxysilane was 100%.

[0100]

Example 2 In Example 2, the heat treatment temperature was set to 260 ° C.
The reaction was conducted under the same treatment and reaction conditions as in Example 1 except that the temperature was changed to 80 ° C. and 300 ° C., and the reaction product was analyzed. The conversion of metal silicon and the selectivity of trimethoxysilane are summarized in Table 1. Table 1

[0101]

Example 3 In Example 3, the reaction was carried out under the same treatment and reaction conditions as in Example 1 except that the reaction was started without performing the heat treatment.

About 4 hours after the start of the reaction, the peak of the methoxysilane compound was not detected. At that time, the conversion of metal silicon was 73%, and the selectivity of trimethoxysilane was 100%.
%Met.

[0103]

Embodiment 4 Metallic silicon treated with HF and first chloride
A mixture obtained by mixing copper (manufactured by Wako Pure Chemical, special grade) for 10 minutes.
After filling 38 g (catalyst concentration 5 wt%) into a fixed bed reactor (made of Pyrex glass, inner diameter 12 mm), the reactor was heated to 240 ° C., and helium gas was flowed down at a flow rate of 6.5 NL / h for 1 hour. It was circulated and heat-treated.

After the heat treatment, while maintaining the reactor temperature at 240 ° C., methanol was supplied at a flow rate of 50 mmol / h to synthesize trimethoxysilane.

Here, the partial pressure of methanol was previously set at 18 kP.
The flow rate of the helium gas was adjusted so as to be a.

At this time, the conversion rate of metal silicon was 88%,
The trimethoxysilane selectivity was 88%.

[0107]

Example 5 In Example 5, the material of the reactor was SUS30.
Except that the reaction was 4, the reaction was carried out under the same treatment and reaction conditions as in Example 1.

About 6 hours after the start of the reaction, the peak of the methoxysilane compound became smaller, and the reaction was stopped.

At this time, the conversion rate of metal silicon is 70%,
The trimethoxysilane selectivity was 95%.

[0110]

Example 6 In Example 6, a reaction was carried out under the same treatment and reaction conditions as in Example 4, except that the supply of helium gas during the heat treatment was an upflow.

At this time, the conversion rate of metal silicon is 60%,
The trimethoxysilane selectivity was 45%.

[0112]

[Embodiment 7] In Embodiment 7, the supply rate of methanol was set to 1
00 mmol / h (partial pressure 35 kPa), 200 mmol
/ H (partial pressure 70 kPa) except that the reaction was carried out under the same treatment and reaction conditions as in Example 4, and the conversion of metal silicon and the selectivity of trimethoxysilane were determined as shown in Table 2.
Summarized in Table 2

[0113]

Example 8 In Example 8, the catalyst and silicon were brought into contact in advance for one hour, and the pretreated fixed bed and the fluidized bed without pretreatment were treated and reacted in the same manner as in Example 1. The reaction was carried out under the conditions, and the reaction temperature and the conversion ratio of trimethoxysilane are summarized in Table 3. Table 3

Although the selectivity was slightly decreased in the fluidized bed as compared with the fixed bed, the conversion was significantly increased.
It can be seen that a pretreatment operation of heating and contacting the silicon and the catalyst is not necessarily required in the fluidized bed.

[0115]

Embodiment 9 In Embodiment 9, the weight of metal silicon was set to 4.
Flow under the same processing and reaction conditions as in Example 1 except that the ratio of the flow rate (mol / h) of methanol to 1 g of metal silicon was 1 or 2, and the partial pressure of methanol was 30 kPa or 60 kPa. The reaction was carried out using the layers, and the metal silicon conversion and trimethoxysilane selectivity are summarized in Table 4. Table 4

It is understood that a good value can be obtained between 1.0 and 2.0 when the flow rate of methanol per hour and the amount of metallic silicon are represented by a molar ratio.

[0117]

Example 10 In Example 10, the flow rate of methanol was set to 1
The reaction was carried out using a fluidized bed under the same treatment and reaction conditions as in Example 1 except that 70 mmol / h and the catalyst concentration were 0.1 to 10 wt%, and the conversion of metal silicon and the selectivity of trimethoxysilane were tabulated. 5 Table 5

[0118]

Example 11 In Example 11, the material of the reaction vessel was Pyrex or SUS, the weight of metal silicon was 4.5 or 9.0 g, and the flow rate of methanol was 160 or 330 mm.
The reaction was carried out using a fluidized bed under the same treatment and reaction conditions as in Example 1 except that the amount was changed to ol / h, and the conversion of metal silicon and the selectivity of trimethoxysilane were summarized in Table 8. Table 6

As described above, almost the same reaction results as in the case where the Pyrex fixed layer was used as the reaction vessel were obtained by SUS.
This can also be achieved using a fluidized bed made of

[0120]

Example 12 In Example 12, the length of the reaction vessel was 12
mm or 24 mm, the weight of metal silicon was 9.0 g, and the flow rate of methanol was 160 or 330 mmol / h, except that the reaction was carried out using a fluidized bed under the same treatment and reaction conditions as in Example 1, and the conversion of metal silicon and Table 7 summarizes the trimethoxysilane selectivity. Table 7

[0121]

Example 13 In Example 13, a fluidized bed was used under the same treatment and reaction conditions as in Example 1 except that the metal silicon particle diameter was changed from 45 to 105 μm or 45 μm or more and the methanol flow rate was set to 160 mmol / h. Table 8 summarizes the metal silicon conversion and the trimethoxysilane selectivity. Table 8

[0122]

Embodiment 14 In Embodiment 14, the methanol flow rate was set to 16
The flow rate of helium gas was adjusted so that 0 mmol / h and the partial pressure of methanol became 44 kPa, and 4.5 g of metallic silicon was introduced at the start of the reaction, and then 2 g every 2 hours.
A reaction was carried out using a fluidized bed under the same treatment and reaction conditions as in Example 1 except that the charge was repeated.

At this time, the conversion rate of metal silicon is 78%,
The trimethoxysilane selectivity was 95%.

[0124]

Example 15 In Example 15, the results of analysis and quantification of impurities in trimethoxysilane obtained under the conditions of Example 1 by ICP emission analysis are shown in Table 9. Table 9

[0125]

Embodiment 16 In Embodiment 16, alumina powder (Mer) was used.
ck Co., Ltd., 30 g), impregnated with a 46.6% aqueous potassium fluoride solution (Wako Pure Chemical, special grade) in an amount corresponding to the pore volume of alumina powder, and air-dried for 30 minutes. The mixture was filled in a firing tube (manufactured by Pyrex glass, inner diameter: 30 mm) and heated and dried at 150 ° C. overnight in a nitrogen gas flow at a flow rate of 100 ml / min.

The alumina powder thus obtained is
This alumina powder contained 11.6% by weight of potassium fluoride, and this alumina powder was used as a disproportionation catalyst.

Then, 0.5 g of the disproportionation catalyst was charged into a reactor (outside diameter 10 mm, inside diameter 8 mm, glass tube made by Pyrex), and heat-treated at 300 ° C. for 1 hour while flowing helium gas at a flow rate of 10 ml / min. went.

Thereafter, trimethoxysilane (water content: 2000 ppm) was introduced into the reactor at a flow rate of 10.5 mol / h, and a disproportionation reaction was carried out at a reaction temperature of 120 ° C. and normal pressure.

The introduction of trimethoxysilane was carried out by diluting and mixing such that the partial pressure of trimethoxysilane became 40 kPa while adjusting the flow rate of helium gas.

Then, the gas discharged from the outlet of the reactor was directly introduced into the gas chromatograph, and the reaction products were analyzed at regular intervals.

As a result, for 150 hours after the start of the reaction, the conversion of trimethoxysilane was maintained at 85%, and the silane generation rate at this time was 12 mmol / h.

The product other than silane was tetramethoxysilane. The molar ratio of silane to tetramethoxysilane was approximately 1: 3, and a value close to the stoichiometric ratio was obtained.

The above 150 hours did not indicate the life of the catalyst, and it was confirmed that the initial activity was continuously maintained even after 150 hours.

[0134]

Embodiment 17 In Embodiment 17, the heat treatment temperature was set to 150 ° C.
The reaction was carried out under the same treatment and reaction conditions as in Example 16 except for the above.

From the start of the reaction, the conversion of trimethoxysilane was maintained at about 80% for 40 hours, and the production rate of silane was 10 mmol / min. Thereafter, the conversion was gradually decreased. .

The product other than silane was tetramethoxysilane, and the molar ratio of silane to tetramethoxysilane was close to the stoichiometric ratio of 1: 3.

[0137]

Example 18 In Example 18, a reaction was carried out under the same treatment and reaction conditions as in Example 16, except that the amount of water contained in trimethoxysilane was 5000 ppm.

From the start of the reaction, the conversion of trimethoxysilane was maintained at about 70% for 10 hours, and the production rate of silane was 8 mmol / min. Thereafter, the conversion was gradually decreased. .

The product other than silane was tetramethoxysilane, and the molar ratio between silane and tetramethoxysilane obtained a value close to the stoichiometric ratio of 1: 3.

[0140]

Example 19 In Example 19, potassium fluoride was added to 1
0.5 g of alumina powder containing 0.4 wt% was used as a disproportionation catalyst, and trimethoxysilane was used at a flow rate of 12 mmol / h.
A reaction was carried out using the fixed layer under the same treatment and reaction conditions as in Example 16 except that the partial pressure was 21 kPa.

It was confirmed that the conversion of trimethoxysilane still maintained a value of 82% even after 190 hours from the start of the reaction.

[0142]

Example 20 In Example 20, the reaction was carried out under the same treatment and reaction conditions as in Example 19 except that the reaction temperature was changed between 80 ° C. and 250 ° C., and the conversion rate of trimethoxysilane was tabulated. 10 Table 10

[0143]

Example 21 In Example 21, the weight W (g) of the catalyst and the flow rate F (mol / mol) of trimethoxysilane per hour were used.
h) is expressed as W / F, which is the weight of the catalyst divided by the flow rate of trimethoxysilane per hour, and this value is defined as 0.1.
The reaction was carried out under the same treatment and reaction conditions as in Example 19 except that the ratio was changed between 5 and 8, and the W / F value and the conversion of trimethoxysilane were summarized in Table 11. Table 11

[0144]

Embodiment 22 First, using the same method as in Embodiment 1, metal silicon carrying copper having a catalyst concentration of 5 wt% is prepared, and 1 g of this metal silicon is filled in a reactor.

Then, at normal pressure, the reactor temperature is set to 200 ° C to 4 ° C.
The temperature was changed in a temperature range of 50 ° C., and a mixed gas in which tetramethoxysilane and hydrogen were mixed at a volume ratio of 1.9: 1 was supplied to the reactor at a flow rate of 55 mmol / h.

The gas discharged from the outlet of the reactor was directly introduced into the gas chromatograph analyzer to analyze the products.

Table 12 shows the conversion of tetramethoxysilane at each reaction temperature. Table 12

Although most of the reaction products were trimethoxysilane, trace amounts of dimethoxysilane and monomethoxysilane were detected.

[0149]

Embodiment 23 In Embodiment 23, after performing etching and cleaning, the silicon is dried at normal pressure to reduce the residual moisture on the silicon surface to 2000 ppm.
Reaction was carried out under the same treatment and reaction conditions as in Example 2. Table 13

As compared with Table 12, at the same reaction temperature, the conversion of tetramethoxysilane was higher in Example 22 where the residual water content was 500 ppm, and a higher conversion rate was obtained when the water content on the silicon surface was lower. I understand.

[0151]

Example 24 In Example 24, catalyst (cuprous chloride) particles of 150 to 200 μm were used and heated at a temperature of 150 ° C.
A heat treatment was performed for a heating time of 10 minutes, and a reaction was performed under the same treatment and reaction conditions as in Example 22 except that silicon having approximately 50 alloy nuclei per square millimeter was used. Table 14

[0152]

Example 25 In Example 25, the pressure during the reaction was increased to 10 k.
g / cm ² G and tetramethoxysilane 54
% And a reaction gas under the same conditions as in Example 22 except that a mixed gas containing 44% of hydrogen was supplied to the reactor at a flow rate of 145 mmol / h. Summarized. Table 15

[0153]

Example 26 In Example 26, a reaction was carried out under the same treatment and reaction conditions as in Example 25 except that the volume flow ratio of tetramethoxysilane to hydrogen was set to 1: 2. Table 16

In comparison with Table 15, at the same reaction temperature, Example 26, in which tetramethoxysilane and hydrogen were mixed at a ratio of 1: 2, had a higher conversion ratio of tetramethoxysilane, and the conversion ratio was higher than that of tetramethoxysilane. It can be seen that the addition of excess hydrogen results in a higher conversion of tetramethoxysilane.

[0155]

According to the present invention, silane used as a raw material in the manufacturing process of polycrystalline silicon, amorphous silicon, semiconductor devices, and the like is produced without passing through corrosive halides. And the production cost can be kept low.

Further, compared to the case of producing trichlorosilane, the amount of impurities in the produced alkoxysilane is extremely small, so that silane having high purity can be produced.

Further, since the tetraalkoxysilane produced in the silane production step or the like can be converted to trialkoxysilane, the silane yield can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of a silane production method according to the present invention.

FIG. 2 is a block diagram showing the configuration of the first embodiment.

FIG. 3 is a block diagram showing a configuration of a second embodiment.

FIG. 4 is a block diagram showing a configuration of a third embodiment.

FIG. 5 is a block diagram showing an overall configuration of a silane production method according to the present invention.

FIG. 6 is a block diagram showing an overall configuration of a method for producing silane according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 first reaction step 11 trialkoxysilane generation step 12, 22, 32 separation step 20 second reaction step 21 silane generation step 30 third reaction step 31 tetraalkoxysilane conversion step 40 first separation Step 50: Second separation step 60: Third separation step 70: Fourth separation step

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasuhisa Nagata 2205 Narita-cho, Oarai-machi, Higashiibaraki-gun, Ibaraki Pref. Inside the Technical Research Institute of JGC Corporation (72) Inventor Eiichi Suzuki 2-38-21 F, Zenpukuji, Suginami-ku, Tokyo F Term (reference) 4G069 AA03 AA08 BA01A BA01B BA05A BA16A BB08A BC03A BC03B BD15A BD15B CB41 DA06 EA01Y FA02 FB14 GA02 4H039 CA92 CJ30 4H049 VN01 VP01 VQ21 VR11 VR43 VS21 VT04 VT32 V36V

Claims (12)

[Claims] 1. A method comprising: a second reaction step of producing silane and tetraalkoxysilane by a disproportionation reaction of trialkoxysilane; and a third reaction step of producing trialkoxysilane from the tetraalkoxysilane. A silane production method characterized by the following. 2. The silane production method according to claim 1, further comprising a first reaction step of producing the trialkoxysilane by causing a gas phase reaction between silicon and alcohol. 3. The method for producing silane according to claim 1, further comprising a step of removing an oxide formed on a surface of the silicon. 4. The method for producing silane according to claim 1, further comprising a step of performing heat treatment by bringing silicon and a copper compound into contact with each other. 5. The silane production method according to claim 1, wherein a metal reactor is used. 6. The method for producing silane according to claim 1, further comprising a step of subjecting the catalyst having reduced catalytic activity to heat treatment to regenerate the catalyst. 7. The method for producing silane according to claim 6, wherein the catalyst is obtained by supporting potassium fluoride or hydrotalcite on alumina or zirconia. 8. The silane production method according to claim 1, wherein in the second reaction step, one or both of the generated silane and tetraalkoxysilane are promptly separated from the reaction step. 9. A process for producing trialkoxysilane, comprising reacting tetraalkoxysilane with silicon and hydrogen in the presence of a catalyst to produce trialkoxysilane. 10. The method for producing trialkoxysilane according to claim 9, wherein the production reaction is performed under high pressure. 11. The method according to claim 1, further comprising: removing an oxide formed on a surface of the silicon; and performing a heat treatment by bringing the silicon into contact with a copper compound as a catalyst. A method for producing trialkoxysilane from tetraalkoxysilane according to claim 9 or 10. 12. The method for producing trialkoxysilane from tetraalkoxysilane according to claim 9, wherein the conversion rate from tetraalkoxysilane to trialkoxysilane is 5% or more.