JP2017210382A - Manufacturing method of disilane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of disilane capable of manufacturing disilane of higher disilane at high selectivity by thermal decomposition of disilane.SOLUTION: Disilane is manufactured by thermal decomposition of silane. The manufacturing method of disilane has; a thermal decomposition process of supplying gas containing silane to a reactor 1 and heating the same to 420°C to 460°C, thermally decomposing the silane so that conversion ratio of the silane becomes 1% to 10% and generating higher silane containing the disilane; a separation process for sending gas containing the higher silane containing the disilane generated in the thermal decomposition process and the undecomposed silane from the reactor 1 to a separator 2, cooling the same at -120°C to -80°C and liquefying or solidifying the higher silane containing the disilane to collect them and separating the higher silane containing the disilane and undecomposed silane; and a circulation process for returning gas containing the undecomposed silane separated in the separation process from the separator 2 to the reactor 1 and supplying the same to the thermal decomposition process again.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing disilane.

  As a method for producing disilane, a thermal decomposition method of silane is known (for example, see Patent Documents 1 to 3). However, the thermal decomposition method of silane sometimes produces various higher order silanes other than disilane, and there is room for improvement in that disilane is selectively produced among various higher order silanes.

Japanese Patent No. 4855462 Japanese Patent Laid-Open No. 11-260729 Japanese Patent Laid-Open No. 03-183614

  Accordingly, the present invention provides a method for producing disilane, which solves the problems of the prior art as described above and can produce disilane with high selectivity among higher silanes by thermally decomposing silane. The task is to do.

In order to solve the above problems, one aspect of the present invention is as described in [1] and [2] below.
[1] A method for producing disilane by thermal decomposition of silane,
A gas containing silane is supplied to the reactor and heated to 420 ° C. or higher and 460 ° C. or lower to thermally decompose the silane so that the conversion rate of silane is 1% or higher and 10% or lower. A pyrolysis process to be generated;
A gas containing high-order silane containing disilane and undecomposed silane produced in the pyrolysis step is sent from the reactor to the separator and cooled to −120 ° C. or higher and −80 ° C. or lower to contain higher order silane containing disilane. A separation step of liquefying or solidifying and collecting silane and separating higher-order silane containing disilane and undecomposed silane;
A circulation step in which the gas containing undecomposed silane separated in the separation step is returned from the separator to the reactor, and again supplied to the thermal decomposition step;
A process for producing disilane.

[2] In the circulation step, the gas containing undecomposed silane separated in the separation step is supplemented with an amount of silane thermally decomposed in the thermal decomposition step, and then returned to the reactor [1] ] The manufacturing method of the disilane of description.

  According to the present invention, disilane can be produced with high selectivity among higher silanes by thermally decomposing silane.

It is the schematic of the disilane manufacturing apparatus explaining the manufacturing method of the disilane which concerns on one Embodiment of this invention.

When silane (SiH ₄ ) is thermally decomposed, higher-order silanes (Si _n H _{2n + 2} , n is an integer of 2 or more) such as disilane (Si ₂ H ₆ ) and trisilane (Si ₃ H ₈ ) are generated. Of these higher silanes, it was not easy to produce disilane with high selectivity.
As a result of diligent study, the present inventors have made it possible to thermally decompose silane while keeping the conversion rate of silane low, and to circulate undecomposed silane and repeatedly thermally decompose disilane with a low conversion rate, thereby achieving high selectivity. The present inventors have found that it is possible to manufacture the present invention and have completed the present invention. Here, the “conversion rate of silane” means a rate at which silane is converted into another substance such as disilane by thermal decomposition.

The reaction in which higher order silane is generated from silane is represented by the following formula.
2SiH ₄ → Si ₂ H ₆ + H ₂
3SiH ₄ → Si ₃ H ₈ + 2H ₂
nSiH ₄ → Si _n H _{2n + 2} + (n−1) H ₂

  Hereinafter, an embodiment of the present invention will be described. In addition, this embodiment shows an example of this invention and this invention is not limited to this embodiment. In addition, various changes or improvements can be added to the present embodiment, and forms to which such changes or improvements are added can also be included in the present invention.

  The method for producing disilane according to the present embodiment is a method for producing disilane by thermal decomposition of silane, a thermal decomposition step for thermally decomposing silane, a higher-order silane containing disilane produced in the thermal decomposition step, and an undecomposed silane. A separation step of separating silane, and a circulation step of circulating undecomposed silane separated in the separation step and thermally decomposing it again.

In the thermal decomposition step, a gas containing silane is supplied to the reactor and heated to 420 ° C. or higher and 460 ° C. or lower, and the silane is thermally decomposed so that the conversion rate of silane is 1% or higher and 10% or lower. It is the process of producing | generating the higher order silane containing.
In the separation step, a gas containing a high-order silane containing disilane generated in the thermal decomposition step and undecomposed silane is sent from the reactor to the separator, and cooled to −120 ° C. or higher and −80 ° C. or lower to contain disilane. In this step, the higher order silane is liquefied or solidified and collected to separate the higher order silane containing disilane and undecomposed silane.

The circulation step is a step in which the gas containing undecomposed silane separated in the separation step is returned from the separator to the reactor, and again supplied to the thermal decomposition step.
According to the production method of disilane of this embodiment, it is possible to produce disilane with high selectivity by suppressing generation of trisilane or the like among higher order silanes. Therefore, disilane can be efficiently produced with high yield.

  Below, the manufacturing method of the disilane of this embodiment is demonstrated still in detail, referring FIG. FIG. 1 shows an example of an apparatus for producing disilane, which is a reactor 1 for heating and thermally decomposing silane, a separator 2 for separating higher-order silane containing disilane generated by pyrolysis and undecomposed silane, and a separator. And a circulation pump 3 for returning the undecomposed silane separated in 2 from the separator 2 to the reactor 1.

  First, after the inside of the system of the disilane production apparatus is depressurized to, for example, vacuum by the vacuum pump 4, the dilution gas for diluting the silane becomes a predetermined pressure in the system of the disilane production apparatus via the dilution gas flow meter 6. To introduce. Next, silane is introduced into a disilane production system from a silane container (for example, a cylinder) (not shown) through the silane flowmeter 5 until a predetermined pressure is reached. Then, the circulation pump 3 is operated to circulate the gas in the system of the disilane production apparatus (hereinafter, the gas circulated in the system of the disilane production apparatus may be referred to as “circulation gas”). Thereby, a mixed gas of silane and dilution gas is supplied to the reactor 1. Since the flow rate of the circulating gas is set to a predetermined flow rate (for example, 2 L / min or more and 20 L / min) by the circulating gas flow meter 7, the flow rate of the mixed gas supplied to the reactor 1 also becomes the predetermined flow rate. .

  The reactor 1 includes a heater (not shown), and the inside of the reactor 1 is heated to a predetermined temperature (420 ° C. or higher and 460 ° C. or lower) by the heater. 420 ° C. or higher and 460 ° C. or lower). The silane is thermally decomposed by heating to produce higher-order silane containing disilane. The conditions such as the temperature in the reactor 1 and the flow rate of the mixed gas are set so that the conversion rate of silane is 1% or more and 10% or less. Is set. Therefore, some of the silanes in the reactor 1 are thermally decomposed to produce higher order silanes such as disilane and trisilane, and other parts are not decomposed and undecomposed silane remains (thermal decomposition step). Therefore, in the reactor 1, there is a gas (hereinafter referred to as “higher silane-containing gas”) containing higher order silane containing disilane generated in the thermal decomposition step, undecomposed silane, and dilution gas. Will be.

  The conversion rate of silane can be controlled by the temperature, pressure, flow rate of mixed gas, etc. in the reactor 1. When the temperature in the reactor 1 is increased, the conversion rate of silane can be increased. Conversely, when the temperature in the reactor 1 is decreased, the conversion rate of silane can be decreased. Further, when the pressure in the reactor 1 is increased, the conversion rate of silane can be increased. Conversely, when the pressure in the reactor 1 is decreased, the conversion rate of silane can be decreased. Furthermore, if the flow rate of the mixed gas is increased, the conversion rate of silane can be decreased, and conversely, if the flow rate of the mixed gas is decreased, the conversion rate of silane can be increased. For example, when the temperature in the reactor 1 is as low as 430 ° C., the flow rate of the mixed gas is reduced to 2 L / min, and when the temperature in the reactor 1 is as high as 450 ° C., the flow rate of the mixed gas is set to 20 L / min. If so, the conversion rate of silane can be controlled to 1% or more and 10% or less.

  The high-order silane-containing gas in the reactor 1 is sent to the separator 2 by a circulation pump 3. The separator 2 is provided with a coolant (not shown) such as liquid nitrogen, and the interior of the separator 2 is cooled to a predetermined temperature (−120 ° C. to −80 ° C.) by the coolant. The contained gas is cooled in the separator 2 to a predetermined temperature (−120 ° C. or higher and −80 ° C. or lower). Higher order silanes such as disilane and trisilane in the higher order silane-containing gas are collected in the separator 2 because they are liquefied or solidified by cooling. Undecomposed silane in the high-order silane-containing gas is hardly collected because it hardly liquefies and solidifies even by cooling. Thereby, in the separator 2, higher silane containing disilane and undecomposed silane are separated (separation step). Therefore, in the separator 2, there is a gas containing undecomposed silane and a diluent gas (hereinafter referred to as “undecomposed silane-containing gas”) together with the higher order silane collected by liquefaction or solidification. It will be. Moreover, the pressure in the system of a disilane manufacturing apparatus falls because higher order silane is liquefied or solidified and collected.

  The method for separating and recovering only disilane from the higher order silane collected by the separator 2 is not particularly limited, but a distillation method can be used. That is, higher order silane containing disilane, trisilane and the like can be distilled to separate disilane and higher order silane from disilane such as trisilane. An adsorption method can also be used. That is, it can be separated using an adsorbent such as zeolite and utilizing the difference in adsorption ability depending on the type of higher order silane.

  The undecomposed silane-containing gas in the separator 2 is returned to the reactor 1 by the circulation pump 3 and again supplied to the thermal decomposition process (circulation process). That is, the undecomposed silane-containing gas is heated to a predetermined temperature (420 ° C. or more and 460 ° C. or less) in the reactor 1, and higher order silane containing disilane is generated by thermal decomposition of silane. At this time, since the conversion rate of silane is set to be 1% or more and 10% or less, a part of the silane in the reactor 1 is thermally decomposed and the other part is not decomposed and undecomposed silane is formed. Remain.

  Then, the higher order silane-containing gas in the reactor 1 is sent again to the separator 2 to separate the higher order silane containing disilane and undecomposed silane, and the undecomposed silane containing gas in the separator 2 is It is returned to the reactor 1 by the circulation pump 3 and used for the thermal decomposition process. In this way, disilane can be efficiently produced in high yield by repeating thermal decomposition of silane at a low conversion rate, collection of higher order silane, and circulation of undecomposed silane-containing gas.

  Although the silane concentration in the system of the disilane production apparatus decreases due to the thermal decomposition of silane, the undecomposed silane-containing gas with the decreased silane concentration may be circulated through the reactor 1 as it is, or the silane may be thermally decomposed. Silane is introduced into the system of the disilane production apparatus from the container through the silane flowmeter 5, silane is supplemented to the undecomposed silane-containing gas, and the undecomposed silane-containing gas having an increased silane concentration is circulated to the reactor 1. The silane may be thermally decomposed.

  When replenishing silane, the amount of silane thermally decomposed in the thermal decomposition step may be replenished to keep the silane concentration in the system of the disilane production apparatus constant at all times. Moreover, the replenishment of silane may be performed constantly or intermittently. The continuous replenishment of silane can be performed by setting the silane flow meter 5 to a predetermined flow rate and constantly introducing a constant flow rate of silane from the silane container into the system of the disilane production apparatus.

  Since excess circulating gas in the disilane production apparatus can be extracted out of the system by the pressure regulating valve 8, when the pressure in the system of the disilane production apparatus becomes high due to replenishment of silane, the excess circulation gas is pressurized. What is necessary is just to adjust a pressure by extracting out of the system with the adjustment valve 8. FIG. Therefore, the pressure in the system of the disilane production apparatus can be kept constant while the circulation gas is circulated and the thermal decomposition of silane is repeated.

In addition, the quality (purity) of the silane used in the disilane production method of the present embodiment is not particularly limited, and any purity may be used, but high-purity silane may be used. preferable.
The thermal decomposition of silane is performed so that the conversion rate of silane is 1% or more and 10% or less. If the conversion rate is within the above numerical range, higher order than disilane such as trisilane, tetrasilane and the like. It is possible to produce disilane with high selectivity by suppressing the production of higher order silane.

  Furthermore, in this embodiment, the mixed gas of silane and dilution gas was circulated in the system of the disilane production apparatus. However, the ratio of silane in the mixed gas may be 10% by volume or more and 80% by volume or less, preferably Is 20 volume% or more and 60 volume% or less. If the ratio of silane in the mixed gas is within the numerical range as described above, an effect is obtained that the gas circulating in the system of the disilane production apparatus is easily maintained at a stable pressure and flow rate. As the dilution gas, a gas inert to silane is preferably used, and specific examples include hydrogen, nitrogen, argon, and helium. Dilution gas may be used individually by 1 type, and may use 2 or more types together (that is, the said mixed gas is good also as a mixed gas of 3 or more types of gas). However, the dilution gas may not be used. That is, only silane may be introduced into the system of the disilane production apparatus and circulated.

  Furthermore, the heating temperature of the silane in the reactor 1 is 420 ° C. or higher and 460 ° C. or lower (more preferably 430 ° C. or higher and 450 ° C. or lower). With such a heating temperature, disilane is sufficiently decomposed by thermal decomposition of silane. It is difficult to produce higher order silanes than disilanes such as trisilane and tetrasilane. Thus, disilane can be produced with high selectivity. As long as the circulating gas passing through the reactor 1 is heated, the shape and heating method of the reactor 1 are not particularly limited. For example, a heating method in which the reaction tower is heated by a heater is adopted. Also good.

  Furthermore, although the cooling temperature in the separator 2 is −120 ° C. or higher and −80 ° C. or lower (more preferably −100 ° C. or higher and −80 ° C. or lower), silane is collected at such a cooling temperature. High-order silane can be collected with high efficiency while suppressing the above. If disilane is circulated to the reactor 1 without being collected by the separator 2, it will be converted to a higher order silane such as trisilane and tetrasilane, and it will be difficult to produce disilane with high selectivity. If it is said cooling temperature, it is possible to manufacture disilane with high selectivity.

  Furthermore, the pressure in the system of the disilane production apparatus (the pressure in the reactor 1 and the separator 2) is not particularly limited, and any of normal pressure, pressurization, and depressurization may be used. The pressure is preferably (gauge pressure) or less, more preferably 0.1 MPa (gauge pressure) or more and 0.6 MPa (gauge pressure) or less.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
[Example 1]
Using a disilane production apparatus similar to the disilane production apparatus of FIG. 1, the same operation as in the above embodiment was performed to thermally decompose silane to produce disilane. The reactor was made of stainless steel, the volume was 0.6 L, and the heating temperature was set to 450 ° C. The cooling temperature of the separator was set to -80 ° C. The dilution gas was hydrogen gas, and was introduced into the disilane production system through a dilution gas flowmeter until the pressure reached 0.15 MPa (gauge pressure). Furthermore, silane was introduced from the silane container through the silane flow meter into the system of the disilane production apparatus until the pressure reached 0.4 MPa (gauge pressure).

  When the pressure adjustment valve is set to 0.4 MPa (gauge pressure) and the pressure in the system of the disilane production apparatus becomes higher than that, excess circulating gas in the disilane production apparatus is brought out of the system by the pressure adjustment valve. The pressure in the system of the disilane production apparatus was always kept at 0.4 MPa (gauge pressure). Further, the circulating gas flow meter was set to 10 L / min so that the flow rate of the circulating gas flowing in the system of the disilane production apparatus was kept constant.

Further, during the reaction, silane was always introduced into the disilane production system from the silane container through the silane flowmeter at a flow rate of 0.2 L / min. Thus, the amount of silane thermally decomposed in the thermal decomposition step was supplemented to keep the silane concentration in the system of the disilane production apparatus constantly constant.
In this way, the silane was thermally decomposed so that the conversion rate of silane was 6.0%, and the reaction was performed for 3 hours. During the reaction, the amount of silane in the circulating gas is analyzed at the inlet and outlet of the reactor using a gas chromatograph GC-14B manufactured by Shimadzu Corporation (the detector is a TCD (Thermal Conductivity Detector) detector). did. And the conversion rate of the silane was computed from the difference of both measured values. After completion of the reaction, the higher silane collected in the separator was analyzed using the same gas chromatograph as described above. The selectivity for disilane was 72.4%.

[Example 2]
Using a disilane production apparatus similar to the disilane production apparatus of FIG. 1, the same operation as in the above embodiment was performed to thermally decompose silane to produce disilane. The reactor was made of stainless steel, its volume was 0.6 L, and the heating temperature was set to 440 ° C. The cooling temperature of the separator was set to -90 ° C. The dilution gas was hydrogen gas, and was introduced into the disilane production system through a dilution gas flowmeter until the pressure reached 0.15 MPa (gauge pressure). Furthermore, silane was introduced from the silane container through the silane flowmeter into the system of the disilane production apparatus until the pressure reached 0.3 MPa (gauge pressure).

  When the pressure adjustment valve is set to 0.3 MPa (gauge pressure) and the pressure in the system of the disilane production apparatus becomes higher than that, excess circulating gas in the disilane production apparatus is removed from the system by the pressure adjustment valve. The pressure inside the system of the disilane production apparatus was always kept at 0.3 MPa (gauge pressure). Further, the circulating gas flow meter was set to 10 L / min so that the flow rate of the circulating gas flowing in the system of the disilane production apparatus was kept constant.

Further, during the reaction, silane was always introduced into the disilane production system from the silane container through the silane flow meter at a flow rate of 0.1 L / min. Thus, the amount of silane thermally decomposed in the thermal decomposition step was supplemented to keep the silane concentration in the system of the disilane production apparatus constantly constant.
In this way, silane was thermally decomposed so that the conversion rate of silane was 3.5%, and the reaction was performed for 3 hours. After completion of the reaction, the higher silane collected in the separator was analyzed using the same gas chromatograph as described above. The selectivity for disilane was 82.7%.

[Comparative Example 1]
The reaction was conducted in the same manner as in Example 2 except that the heating temperature of the reactor was 470 ° C., the replenishing silane flow rate was 0.4 L / min, and the silane conversion was 14.6%. After completion of the reaction, the higher silane collected in the separator was analyzed using the same gas chromatograph as described above. The selectivity for disilane was 43.8%.
From these results, it can be seen that disilane can be produced with high selectivity by carrying out the reaction while keeping the conversion rate of silane low.

1 Reactor 2 Separator 3 Circulation Pump 4 Vacuum Pump 5 Silane Flow Meter 6 Diluent Gas Flow Meter 7 Circulating Gas Flow Meter 8 Pressure Control Valve

Claims (2)

A method for producing disilane by thermal decomposition of silane,
A gas containing silane is supplied to the reactor and heated to 420 ° C. or higher and 460 ° C. or lower to thermally decompose the silane so that the conversion rate of silane is 1% or higher and 10% or lower. A pyrolysis process to be generated;
A gas containing high-order silane containing disilane and undecomposed silane produced in the pyrolysis step is sent from the reactor to the separator and cooled to −120 ° C. or higher and −80 ° C. or lower to contain higher order silane containing disilane. A separation step of liquefying or solidifying and collecting silane and separating higher-order silane containing disilane and undecomposed silane;
A circulation step in which the gas containing undecomposed silane separated in the separation step is returned from the separator to the reactor, and again supplied to the thermal decomposition step;
A process for producing disilane.   2. The circulation step according to claim 1, wherein the gas containing undecomposed silane separated in the separation step is supplemented with an amount of silane thermally decomposed in the thermal decomposition step and then returned to the reactor. Disilane production method.

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