JPS64325B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing monosilane by disproportionation reaction of hydrochlorosilane.

Silane is particularly useful as a raw material for producing silicon, which is used in semiconductor devices or solar cells, by pyrolysis.

It is well known that the disproportionation reaction of chlorosilanes in the presence of a catalyst is an equilibration reaction as shown in the following formula, and that monosilane is obtained by this reaction.

2HSiCl ₃ H ₂ SiCl ₂ +SiCl ₄ (1) 2H ₂ SiCl ₂ H ₃ SiCl+HSiCl ₃ (2) 2H ₃ SiClSiH ₄ +H ₂ SiCl ₂ (3) However, the conventional methods for producing monosilane have a number of drawbacks. For example, in JP-A-47-12569, a solid anion exchange resin and dichlorosilane are brought into contact and monosilane is obtained by the disproportionation reaction. This method has the disadvantages that the reaction rate is slow and the catalyst is expensive. In addition, the activity of amine-based disproportionation catalysts is significantly reduced by trace amounts of moisture, so careful attention must be paid to the dehydration and drying process. In this dehydration and drying process, the heating temperature of solid anion exchange resins has a sensitive effect on the catalytic activity.
It is not possible to carry out short-term drying under reduced pressure by heating, which is complicated by requiring either long-term drying at room temperature under a stream of inert gas, or thorough washing and dehydration using a water-free solvent.

Next, JP-A-57-209816 discloses that a compound having an α-oxoamine group is used as a catalyst and brought into contact with dichlorosilane to obtain monosilane. In this method, monosilane is obtained from the top of the column by bringing dichlorosilane gas into countercurrent contact with the catalyst in the column using a device equipped with a tray-type column in a round-bottomed flask.
A mixture of high boiling chlorosilanes, catalyst and solvent is removed from the round bottom flask via overflow. This method uses a large amount of catalyst and requires separation of high-boiling chlorosilanes, solvent, and catalyst after removing monosilane, so it is not suitable for monosilane synthesis on an industrial scale.

Furthermore, in Japanese Patent Publication No. 57-20244, 1,8-diazabicyclo[5,4,0]-7-undecene is used as one of the catalysts used when producing dichlorosilane by disproportionation reaction of trichlorosilane. However, there is no mention of producing silane from dichlorosilane or using a solid catalyst.

The object of the present invention is to provide a catalyst with superior performance that can disproportionate hydrochlorosilane to produce monosilane.

The present inventors continued their research to achieve the above object, and as a result found that the object could be achieved by using a catalyst in which DBU or a DBU salt was supported on a carrier, and thus completed the present invention.

That is, the gist of the present invention is to bring hydrochlorosilane and the above catalyst into contact for a short period of time.

The resulting equilibrium mixture can be rectified to obtain monosilane.

The hydrochlorosilane that can be used in the present invention is preferably dichlorosilane or monochlorosilane, but a mixture of two or more hydrochlorosilanes with an H/Cl (atomic ratio) of 1/2 or more, preferably 1/1 or more can also be used. be able to.

The DBU or DBU salt-supported catalyst used in the method of the present invention can be used, for example, in an alcohol such as methanol.
It can be prepared by dissolving DBU or DBU salt, adding a carrier to the solution, stirring, distilling off methanol, and directly drying under reduced pressure by heating. Examples of DBU salts that can be used at this time include hydrogen chloride salt, hydrogen iodide salt, trichlorosilane salt, and dichlorosilane salt.

Supports that can be used include those that can be used as ordinary catalyst supports, such as silica, alumina, silica-alumina, zeolite, and activated carbon.

The disproportionation reaction of hydrochlorosilanes starts from 0°C.
It can be carried out at 400° C., preferably from 50° C. to 150° C., under atmospheric pressure, under pressure below atmospheric pressure, or under pressure above atmospheric pressure.

The amount of DBU or DBU salt supported on the carrier that can be used in the present invention can be in the range of 0.001 to 0.5 g in terms of DBU per 1 ml of the apparent solution volume of the carrier, preferably in the range of 0.01 to 0.05 g. .
It is also possible to carry out the reaction continuously over a long period of time.

The contact time between the catalyst and dichlorosilane to reach sufficient thermodynamic equilibrium in the disproportionation reaction of dichlorosilane in the present invention (based on the reaction tube space).
is 0.5 seconds or more. In terms of production efficiency, a shorter contact time is advantageous, and is preferably 1 to 5 seconds.

As described above, the present invention can efficiently obtain monosilane from hydrochlorosilane using a DBU-supported catalyst.

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

Example 1 Dichlorosilane with a purity of 99% is placed in a stainless steel cylinder (1), and the cylinder is heated to 50°C in an oil bath. As a result, a constant flow rate of dichlorosilane vapor is introduced into the preheater, and the vapor is heated to 80% of the reaction temperature in the preheater.
℃ and introduced into the reactor. The reactor is made of stainless steel with an inner diameter of 10 mm and a length of 150 mm.
35~ containing 5% by weight of DBU hydrochloride
Silica gel having a mesh size of 70, a pore diameter of 40 angstroms, and a specific surface area of 650 m ² /g was added and heated to 80°C. The reaction vapor flowing out from the reactor was condensed and collected using a dry ice acetone bath and a liquid nitrogen trap. The analysis results of the reaction vapor by gas chromatography at a contact time of 1 second were as follows.

Monosilane 11.2 mol% Monochlorosilane 16.2 〃 Dichlorosilane 37.1 〃 Trichlorosilane 35.0 〃 Tetrachlorosilane 0.5 〃 Example 2 In a reaction apparatus similar to Example 1, a 35-70 mesh containing 5 weight percent of DBU hydrochloride, a pore size of 40 angstroms, Silica gel with a specific surface area of 650 m ² /g was added and heated to 80°C. Dichlorosilane gas with a purity of 99% was then introduced into the reactor for a contact time of 2 seconds. The reaction was carried out for 6 hours a day for 50 consecutive days.
The reaction was carried out for 300 hours. At this time, gas chromatography analysis conducted every 2 hours showed that monosilane was 10.8~
The yield was maintained at 11.4 mol percent, indicating the long-term activity of the catalyst. After 300 hours of reaction, the nitrogen content in the catalyst was analyzed and found that 93% of the nitrogen content remained compared to the analysis value before the start of the reaction.

Claims (1)

[Claims] 1 1,8-diazabicyclo[5,4,0]-undecene-7 (hereinafter abbreviated as "DBU") or
A method for producing monosilane, which comprises supporting a DBU salt on a carrier and contacting the carrier with hydrochlorosilane. 2. The method according to item 1, wherein the hydrochlorosilane is dichlorosilane. 3. The method according to item 1, wherein the hydrochlorosilane is a mixture of hydrochlorosilanes and has an atomic ratio of H/Cl of 1/2 or more. 4. The method according to item 3, wherein the atomic ratio is 1/1 or more.