JP2020164357A - Method and apparatus for treating polymer - Google Patents

Abstract

To provide a method and apparatus for treating a polymer, capable of: smoothly treating the polymer produced in a step of cooling a reaction product gas generated through a conversion reaction, thereby performing operations with small energy consumption; and reducing loads of polymer disposal work, thereby improving use efficiency in a raw material.SOLUTION: A polymer is collected which is produced by cooling a reaction production gas obtained through conversion reaction of a material gas containing tetrachlorosilane and hydrogen, and the polymer is brought into contact with a hydrogenation catalyst and then is reacted, thereby producing trichlorodisilane or tetrachlorodisilane from hexachlorodisilane in the polymer.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method and a treatment apparatus for treating a polymer of chlorosilanes recovered in the conversion step of converting silicon tetrachloride to trichlorosilane.

High-purity polycrystalline silicon used as a semiconductor material is made from high-purity trichlorosilane (SiHCl ₃ : TCS) produced by a conversion reaction in which silicon tetrachloride (SiCl ₄ : STC) is reacted with hydrogen. It is mainly produced by hydrogen reduction reaction and thermal decomposition reaction of trichlorosilane.

As an apparatus for producing trichlorosilane by such a conversion reaction, for example, Patent Document 1 describes trichlorosilane by introducing silicon tetrachloride and hydrogen into a reaction chamber and causing a conversion reaction at a temperature of 600 ° C. to 1200 ° C. It is disclosed to obtain a reaction product gas containing hydrogen chloride and hydrogen chloride. Then, as a trichlorosilane production apparatus, an apparatus provided with a cooling means for rapidly cooling the reaction-producing gas derived from the reaction chamber at a cooling rate such as reaching 300 ° C. or lower within 1 second has been proposed.

When the reaction product gas is rapidly cooled in such an extremely short time, the reverse reaction in which trichlorosilane in the reaction product gas reacts with hydrogen chloride and decomposes into silicon tetrachloride and hydrogen can be suppressed. The conversion rate of chlorosilane can be increased. However, on the other hand, in the cooling process, dichlorosilylene (SiCl ₂ ) contained in the reaction production gas reacts with silicon tetrachloride (SiCl ₄ ) to form silicon such as hexachlorodisilane (disilicon hexachloride: Si ₂ Cl ₆ ). It is known that higher-order chlorosilanes (polymers) containing two or more atoms are by-produced.

The polymer produced as a by-product in such a conversion step was separated from useful substances such as trichlorosilane, hydrolyzed and discarded. Further, Patent Document 2 proposes a method of decomposing a polymer and converting it into useful trichlorosilane. Patent Document 2 discloses that a raw material gas obtained by mixing a polymer and hydrogen chloride is reacted under heating at 450 ° C. or higher to convert the polymer into trichlorosilane.

Special Publication No. 57-38524 JP-A-2009-227757 JP-A-2007-1791

As described in Patent Document 2, by providing a polymer decomposition furnace to recover trichlorosilane, the burden of hydrolyzing the polymer and disposing of it can be significantly reduced. Further, by reusing the recovered trichlorosilane, it is possible to improve the efficiency of using the raw material and reduce the manufacturing cost.
However, in the polycrystalline silicon manufacturing process, further reduction of manufacturing cost is required. In the decomposition furnace, it is necessary to heat at a high temperature of 450 ° C. or higher in order to react the polymer with hydrogen chloride, and there is a problem that energy consumption is large.

The present invention has been made in view of such circumstances, and it is possible to smoothly process the polymer produced in the step of cooling the reaction-generated gas generated by the conversion reaction to perform an operation with low energy consumption. It is an object of the present invention to provide a polymer treatment method and a treatment apparatus capable of reducing the burden of polymer disposal work and increasing the efficiency of use of raw materials.

In the polymer treatment method of the present invention, the polymer produced by cooling the reaction product gas obtained by converting the raw material gas containing silicon tetrachloride and hydrogen into a reaction product is recovered, and the polymer is brought into contact with a hydrogenation catalyst to react. This is characterized in that trichlorodisilane or tetrachlorodisilane is produced from hexachlorodisilane in the polymer.

The reaction product gas produced in the conversion furnace contains a large amount of dichlorosilylene (SiCl ₂ ). Dichloromethane is abundantly produced in the conversion reaction at a high temperature, and is particularly remarkably produced at a temperature exceeding 1200 ° C.
Therefore, in the cooling process, dichlorosilylene reacts with silicon tetrachloride to produce a polymer mainly composed of hexachlorodisilane (Si ₂ Cl ₆ ) in the condensate. Then, by contacting the polymer in the hydrogenation catalyst, the hexachlorodisilane in the polymer to produce a hydrogenated with trichlorodisilane _{(Si 2} H ₃ Cl 3), or tetrachlorodisilane _{(Si 2} H ₂ Cl ₄₎ Can be done.

Trichlorodisilane and tetrachlorodisilane easily react with a boron compound such as boron trichloride, and react with the boron compound to form a complex having a high boiling point.
For example, according to Patent Document 3, in a method of purifying trichlorosilane contained in a gas produced by a reaction in a chlorination furnace, the applicant has brought a silane chloride polymer into contact with a mixed fluid containing trichlorosilane. , Boron trichloride (BCl ₃ , boiling point 12.4 ° C.) and other boron compounds are reacted to form a complex with a high boiling point, and then distillation separation is proposed.
When trichlorosilane is produced through the distillation step, among the impurities, boron mainly exists as boron trichloride and has a boiling point close to that of trichlorosilane, so that it is difficult to separate by distillation, but it contains trichlorodisilane or tetrachlorodisilane. By adding the condensate, a complex having a high boiling point can be formed, and it can be easily separated from trichlorosilane.

Therefore, the method of the present invention in which the polymer is converted to trichlorodisilane or tetrachlorodisilane by the action of a hydrogenation catalyst is such that the polymer is heated at a high temperature in order to react with hydrogen chloride, as described in Patent Document 2. It is not necessary to provide a decomposition furnace, and the polymer can be converted into trichlorodisilane or tetrachlorodisilane, which is useful for distillation of trichlorosilane, and an operation with low energy consumption can be performed.

In the polymer treatment method of the present invention, nickel can be used as the hydrogenation catalyst.
Since nickel acts effectively as a hydrogenation catalyst for hexachlorodisilane contained in the polymer, it can react well and trichlorodisilane or tetrachlorodisilane can be preferably produced.

The polymer processing apparatus of the present invention is an apparatus for processing a polymer produced in a step of cooling a reaction-generated gas generated by a conversion reaction of a raw material gas containing silicon tetrachloride and hydrogen, and is a solid contained in the polymer. It comprises a filter for removing fractions, which is characterized in that at least the surface is formed of a hydrogenation catalyst.

By forming the surface of the filter with a hydrogenation catalyst, solids such as silicon powder contained in the polymer are removed, and the polymer (hexachlorodisilane) easily reacts with a boron compound such as boron trichloride. Trichlorodisilane or tetrachlorodisilane can be produced.

According to the present invention, energy is produced by smoothly processing the polymer produced in the step of cooling the reaction-producing gas generated by the conversion reaction to produce trichlorodisilane or tetrachlorodisilane which is beneficial for distillation of trichlorosilane. It is possible to carry out operations with low consumption, reduce the burden of polymer disposal work, and improve the efficiency of using raw materials.

It is a schematic diagram which shows one Embodiment of the trichlorosilane production apparatus to which the polymer treatment method of this invention was applied. It is a schematic diagram which shows the detailed structure of the polymer processing apparatus shown in FIG. It is a front view which shows the filter. It is a front view which shows the wire mesh plate. It is a schematic diagram which shows the other embodiment of a polymer processing apparatus.

Hereinafter, a polymer treatment method according to the present invention and an embodiment of a trichlorosilane production apparatus to which the polymer treatment method is applied will be described. Figure 1 shows a schematic overall configuration of the apparatus for producing trichlorosilane 100, in the figure, trichlorosilane TCS, silicon tetrachloride STC, hydrogen H _2, hydrogen chloride is expressed as HCl.

The trichlorosilane production apparatus 100 is supplied with a conversion furnace 1 that generates a reaction generation gas by converting a raw material gas containing silicon tetrachloride and hydrogen, and a reaction production gas from the conversion furnace 1, and cools the reaction production gas. A cooler 2 for recovering the condensate containing trichlorosilane and a polymer treatment apparatus 8 for producing trichlorodisilane or tetrachlorodisilane by contacting the polymer contained in the condensate with a hydrogenation catalyst and reacting them. And have.

In the conversion furnace 1, the raw material gas supply pipe 11 for supplying the raw material gas into the furnace and the reaction generated gas supply pipe 12 for supplying the reaction generated gas generated in the furnace to the cooler 2 are connected. ing. In this conversion furnace 1, silicon tetrachloride is converted by heating the raw material gas supplied through the raw material gas supply pipe 11, and a reaction product gas containing trichlorosilane is obtained (conversion step). The reaction product gas is supplied to the cooler 2 through the reaction product gas supply pipe 12.

In the cooler 2, the reaction product gas supplied through the reaction product gas supply pipe 12 is condensed, and chlorosilanes mainly containing trichlorosilane are recovered as the reaction product (cooling step). In this cooler 2, a liquid recovery unit 3 for collecting the condensate (liquid) in the vessel, a gas recovery unit 4 for recovering the gas in the vessel, a first nozzle 5A for spraying the coolant in the vessel, and A second nozzle 5B is provided.
The liquid recovery unit 3 includes a connection pipe 31 connected to the lower part of the cooler 2 and a tank 32 connected to the connection pipe 31, and collects the condensate in the cooler 2 and stores it in the tank 32. .. The condensate stored in the tank 32 contains a condensed reaction product (trichlorosilane, etc.) and a coolant, and a part of the condensate is a first nozzle 5A at a flow rate controlled by the pump 7 and the valve 9. And while being supplied to the second nozzle 5B, it is sent to the condensate tank 6. Further, the tank 32 is provided with a composition analysis unit 33 that analyzes the composition of the recovered condensate, and the composition analysis unit 33 analyzes the composition of the condensate in the tank 32 to generate a condensed reaction. The amount of polymer and trichlorosilane contained in the product can be measured.

The gas recovery unit 4 includes a connecting pipe 41 connected to the upper part of the cooler 2 and a condenser 42 connected to the connecting pipe 41, and the gas recovered from the cooler 2 is condensed by the condenser 42. Collect the liquid and gas separately. The gas recovered from the cooler 2 contains reaction products (trichlorosilane, etc.) and unreacted gas that were not condensed in the cooler 2, and the liquid liquefied by being cooled and condensed in the condenser 42 is condensed. The gas containing hydrogen and hydrogen chloride that was sent to the liquid tank 6 and was not liquefied in the condenser 42 was sent to the hydrogen chloride recovery system (not shown), separated into hydrogen and hydrogen chloride, and used respectively. To.

The first nozzle 5A and the second nozzle 5B are provided in the upper part of the cooler 2, and spray the coolant supplied through the heat exchangers 51A and 51B, respectively. The coolant is a condensate containing silicon tetrachloride and trichlorosilane as main components, which is supplied from the tank 32 by the pump 7.
Further, the trichlorosilane production apparatus 100 has a control unit 34 that individually controls the temperature and the spray amount of the coolant sprayed from the first nozzle 5A and the second nozzle 5B based on the measurement analysis result of the composition analysis unit 33. Is provided. Further, reference numeral 35 shown in FIG. 1 is a strainer, which removes solid content contained in the condensate.

As shown in FIG. 1, the polymer processing apparatus 8 is provided downstream of the condensate tank 6 and processes the polymer extracted from the condensate tank 6. Then, the treatment liquid after passing through the polymer treatment apparatus 8 is guided to a distillation system (not shown).
As shown in FIG. 2, the polymer processing apparatus 8 has a filter 81 for removing solids such as silicon powder contained in the polymer, and a catalytic reaction tower for contacting the polymer via the filter 81 with a hydrogenation catalyst to react them. It is equipped with 88.

As shown in FIG. 3, for example, the filter 81 has a configuration in which a plurality of wire mesh plates 86 are laminated. As shown in FIG. 4, each wire mesh plate 86 is formed by knitting a plurality of wires 87 into a slightly corrugated plate shape so as to make the surface uneven.
The catalytic reaction tower 88 includes a nickel catalyst that effectively acts as a hydrogenation catalyst for hexachlorodisilane contained in the condensate, and for example, sponge metal-like nickel (for example, sponge nickel R-100 manufactured by Nikko Rica). , R-200) packed with columns.

In the illustrated example, two filters 81 are installed in the polymer processing apparatus 8, and each of the filters 81A and 81B is provided with a supply pipe 82 from the condensate tank 6 branched into two. It is provided in the middle of 82A and 82B, respectively. Then, the branch pipes 82A and 82B are connected to one pipe again after passing through the filters 81A and 81B, and are connected to the catalytic reaction tower 88. Further, valves 83a, 84a, 83b, 84b capable of opening and closing the branch pipes 82A, 82B are arranged before and after the filters 81A, 81B, and by opening and closing the respective valves 83a, 84a, 83b, 84b. , The filter 81 can be selected and used for either one, and the other filter 81 can be maintained during its use.

For example, when the filter 81B is separated and the filter 81A is selected, the valves 83a and 84a are opened and the valves 83b and 84b are closed. In this state, the polymer sent from the condensate tank 6 flows to the filter 81A through the branch pipe 82A. Subsequently, the polymer that has passed through the filter 81A passes through the catalytic reaction column 88 and is guided to the distillation system.
At this time, the maintenance of the other filter 81B performed while the one filter 81A is in use can be performed by opening the valve 85a and using the treatment liquid after the polymer treatment.

Trichlorosilane can be produced as follows using the trichlorosilane production apparatus 100 configured as described above.
<Conversion process>
First, the raw material gas containing silicon tetrachloride and hydrogen is supplied into the conversion furnace 1 through the raw material gas supply pipe 11. When the raw material gas is heated to 1000 ° C. to 1900 ° C. in the conversion furnace 1, the conversion reaction (hydrogenation) of the formula (1) occurs, and the reaction product gas is generated.
SiCl ₄ + H ₂ → SiHCl ₃ + HCl… (1)
This reaction-producing gas is supplied to the cooler 2 through the reaction-producing gas supply pipe 12.

<Cooling process>
The reaction product is obtained by cooling the reaction product gas in the cooler 2 with the coolant sprayed from the first nozzle 5A and the second nozzle 5B. At this time, the high-temperature reaction-producing gas generated in the conversion step can be rapidly cooled by spraying a cooling liquid, and the reaction-producing gas is cooled at a cooling rate at which the decomposition of trichlorosilane is suppressed.
Specifically, the reaction product gas is cooled to 600 ° C. to 950 ° C. within 0.01 seconds to 1 second, then maintained at 600 ° C. to 950 ° C. for about 0.01 seconds to 5 seconds, and finally. The cooling rate is adjusted so that it cools to less than 600 ° C.

The cooled and liquefied condensate of the reaction product is collected in the liquid recovery unit 3 together with the cooling liquid, and is stored in the tank 32 through the connecting pipe 31. Further, the gas in the cooler 2 is recovered by the gas recovery unit 4 and sent to the condenser 42 through the connecting pipe 41. The gas mainly contains trichlorosilane, silicon tetrachloride, hydrogen chloride, and hydrogen. In the condenser 42, hydrogen chloride gas and hydrogen gas are recovered, and condensed and liquefied trichlorosilane is recovered. A part of the condensate recovered by the liquid recovery unit 3 is sent to the first nozzle 5A and the second nozzle 5B as a cooling liquid, and the remaining condensate is recovered together with the trichlorosilane recovered by the gas recovery unit 4. Will be done.

The condensate containing trichlorosilane as a main component stored in the condensate tank 6 is sent to a distillation system (not shown). Further, the polymer contained in the condensate is sent to the polymer processing apparatus 8 and supplied to the catalytic reaction column 88 via the filter 81.
The reaction production gas generated in the conversion furnace 1 contains a large amount of dichlorosilylene, and in the cooling step, dichlorosilylene reacts with silicon tetrachloride to generate hexachlorodisilane, so that the condensed solution contains hexachlorodisilane. There are many polymers mainly composed of hexachlorodisilane. Then, when this polymer comes into contact with a nickel catalyst that effectively acts as a hydrogenation catalyst for hexachlorodisilane, hexachlorodisilane is hydrogenated to produce trichlorodisilane or tetrachlorodisilane.
The treatment liquid containing trichlorodisilane or tetrachlorodisilane that has passed through the polymer treatment apparatus 8 is sent to a distillation system (not shown) and used for separating trichlorosilane and the like.

As described above, the method of the present invention in which the polymer is converted to trichlorodisilane or tetrachlorodisilane by the action of a hydrogenation catalyst does not require a decomposition furnace to be heated at a high temperature in order to react the polymer with hydrogen chloride. The polymer can be converted to trichlorodisilane or tetrachlorodisilane, which are beneficial for distillation of trichlorosilane, allowing operations with low energy consumption. Then, by reusing the trichlorosilane recovered in the distillation step, the efficiency of using the raw material can be improved, the amount of polymer waste can be reduced, and the burden of polymer waste work can be reduced.

By the way, in the above embodiment, the filter 81 of the polymer processing apparatus 8 and the catalytic reaction tower 88 are separately installed. For example, the surface of the wire mesh plate 86 shown in FIGS. 3 and 4 is coated with nickel. By forming the filter 81 in such a manner, the filter 81 can be configured to have a function of a hydrogenation catalyst. In this case, as in the polymer processing apparatus 80 shown in FIG. 5, the catalytic reaction column can be omitted.
In the polymer processing apparatus 80 shown in FIG. 5, by passing the polymer through the filters 81A and 81B, solids such as silicon powder contained in the polymer are removed, and the polymer is mixed with a boron compound such as boron trichloride. It is possible to produce trichlorodisilane or tetrachlorodisilane which are easy to react.
Other configurations are the same as those of the polymer processing apparatus 8, and the common parts are designated by the same reference numerals and the description thereof will be omitted.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, it is possible to use a configuration other than the wire mesh plate as the filter. Further, in the polymer processing devices 8 and 80, the two filters 81 are switched and used, but the number of the filters 81 is not limited.
Further, as the hydrogenation catalyst, activated carbon or nickel, ruthenium, palladium, or platinum supported on the activated carbon may be used.

1 Conversion furnace 2 Cooler 3 Liquid recovery unit 4 Gas recovery unit 5A 1st nozzle 5B 2nd nozzle 6 Condensate tank 7 Pump 8,80 Polymer processing device 9 Valve 11 Raw material gas supply pipe 12 Reaction generation gas supply pipe 31 Connection pipe 32 Tank 33 Composition analysis unit 34 Control unit 41 Connection pipe 42 Condenser 51A, 51B Heat exchanger 81, 81A, 81B Filter 82 Supply pipe 82A, 82B: Branch pipe 83a to 85a, 83b to 85b Valve 86 Wire mesh plate 87 Wire 88 Catalytic reaction tower 100 Trichlorosilane production equipment

Claims (3)

Hexachlorodisilane in the polymer is recovered by recovering the polymer produced by cooling the reaction-generated gas obtained by converting the raw material gas containing silicon tetrachloride and hydrogen, and bringing the polymer into contact with a hydrogenation catalyst to react. A polymer treatment method comprising producing trichlorodisilane or tetrachlorodisilane from. The polymer treatment method according to claim 1, wherein nickel is used as the hydrogenation catalyst. A device for processing a polymer produced in a step of cooling a reaction-generated gas generated by a conversion reaction of a raw material gas containing silicon tetrachloride and hydrogen, comprising a filter for removing solid content contained in the polymer. The filter is a polymer processing apparatus characterized in that at least the surface is formed of a hydrogenation catalyst.

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