JP5392488B2 - Production method and use of trichlorosilane - Google Patents

Description

  The present invention relates to a method for producing trichlorosilane, which is excellent in the effect of recovering trichlorosilane, and its use in a method for producing trichlorosilane in which tetrachlorosilane and hydrogen are reacted to convert to trichlorosilane.

High-purity polycrystalline silicon is obtained by using, for example, trichlorosilane (referred to as SiHCl ₃ : TCS), tetrachlorosilane (referred to as SiCl ₄ : STC), and hydrogen as raw materials, and a hydrogen reduction reaction of trichlorosilane represented by the following formula [1]. It can be produced by a thermal decomposition reaction of trichlorosilane represented by the following formula [2].

SiHCl ₃ + H ₂ → Si + 3HCl (1)
4SiHCl ₃ → Si + 3SiCl ₄ + 2H ₂ ... [2]

  Trichlorosilane, which is a raw material for the above production method, is obtained by reacting metal silicon with hydrogen chloride to produce crude trichlorosilane, which is purified by distillation. Further, trichlorosilane can be produced by a hydrogenation conversion reaction represented by the following formula [3] using tetrachlorosilane recovered by distillation separation from the exhaust gas of the production reaction of polycrystalline silicon as a raw material.

SiCl ₄ + H ₂ → SiHCl ₃ + HCl (3)

  As an apparatus for producing this trichlorosilane, for example, a conversion reaction apparatus (conversion furnace) described in Patent Document 1 is known. This conversion reaction apparatus has a double chamber consisting of an outer chamber and an inner chamber in which a reaction chamber surrounded by a heating element is formed by two concentric tubes, and a heat exchanger is provided at the bottom of the reaction chamber. A raw material gas supply line for supplying hydrogen and tetrachlorosilane to the reaction chamber via the heat exchanger, and a discharge line for discharging the reaction product gas from the reaction chamber, and the heat exchange In the vessel, the supply gas supplied to the reaction chamber is preheated by transferring heat from the reaction product gas discharged from the reaction chamber, and the discharged reaction product gas is cooled.

  For example, Patent Document 2 discloses that a reaction product gas containing trichlorosilane and hydrogen chloride is obtained by introducing tetrachlorosilane and hydrogen into a reaction chamber and performing a conversion reaction at a temperature of 600 ° C. to 1200 ° C. There has been proposed one provided with a cooling means for rapidly cooling the reaction product gas derived from the above at a cooling rate so as to reach, for example, 300 ° C. or less within 1 second.

Japanese Patent No. 3781439 Japanese Patent Publication No.57-38524

  By the way, in the apparatus for producing trichlorosilane described in Patent Document 1, the reaction product gas is cooled by exchanging heat with the supplied raw material gas in the heat exchanger at the lower part of the reaction chamber. In the process, trichlorosilane reacts with hydrogen chloride, and the reverse reaction of the above reaction formula [3] occurs in which silicon tetrachloride (STC) and hydrogen are decomposed. Here, the conventional cooling by the heat exchanger has a disadvantage that the rate of conversion to trichlorosilane is reduced because the reverse reaction cannot be sufficiently suppressed due to the slow cooling rate.

Further, as described in Patent Document 2, the reverse reaction of the above reaction formula [3] is performed by quenching in an extremely short time of 1 second or less to a temperature range of 300 ° C. or less where the reverse reaction hardly occurs. It is possible to suppress. However, when quenching in such an extremely short time, in the cooling process, for example, as shown in the following formula [4], SiCl ₂ (dichlorosilylene) contained in the reaction gas reacts with SiCl _4. It is known that polymers are by-produced. A large amount of this SiCl ₂ is produced at high temperatures in the conversion reaction, and is particularly prominent at temperatures exceeding 1200 ° C., and is contained in the reaction gas extracted from the conversion furnace. The polymer is a general term for higher-order chlorosilanes containing two or more silicon atoms such as Si ₂ Cl ₆ (chlorodisilane), Si ₃ Cl ₈ (chlorotrisilane), Si ₂ H ₂ Cl ₄ and the like. .

SiCl ₂ + SiCl ₄ → Si ₂ Cl ₆ ... [4]

  Thus, when quenching in an extremely short time, decomposition of trichlorosilane during cooling (reverse reaction of formula [3]) is suppressed, and the decrease in trichlorosilane decreases, but the amount of polymer produced Increases, causing problems such as polymer deposition on the piping after the cooling process. On the other hand, when the cooling rate is slow, the amount of polymer produced decreases, but the decomposition of trichlorosilane proceeds and the recovery rate of trichlorosilane decreases.

  Thus, it is necessary to control the reaction gas extracted from the conversion furnace to an appropriate cooling rate. However, the reaction gas extracted from the conversion furnace has a high temperature of 1000 ° C. or higher, and when it is rapidly cooled, it is difficult to appropriately control the cooling rate in a high temperature region of 600 ° C. or higher where trichlorosilane is easily decomposed. . For this reason, conventionally, priority was given to increasing the recovery rate of trichlorosilane, and cooling was performed at an excessive cooling rate.

  Therefore, although the recovery rate of trichlorosilane is high, there is a problem that the generation of the polymer cannot be suppressed and the burden of removing the polymer adhering to the piping is large. Particularly, since the cooling rate is distributed as the apparatus becomes larger, it is difficult to appropriately control the cooling rate of the entire gas, and the cooling rate may be extremely increased locally. For this reason, it becomes difficult to sufficiently suppress the generation of the polymer.

  The present invention has solved the above-mentioned conventional problems, and in the process of cooling the gas generated by the conversion reaction, effectively suppresses the decomposition of trichlorosilane and the production of the polymer, and the burden of the polymer removal work is small. In addition, a method for producing trichlorosilane having a high recovery rate of trichlorosilane is provided.

The present invention relates to a production method and use of trichlorosilane which has solved the above problems by having the following configuration.
[1] A raw material tetrachlorosilane and hydrogen are converted at a temperature of 1000 to 1900 ° C. to produce a reaction gas containing trichlorosilane, dichlorosilylene, hydrogen chloride, and a higher silane compound, and the reaction gas is cooled. In the method for recovering trichlorosilane, (a) a first cooling step in which the reaction gas extracted from the converter is cooled to 600 ° C. or higher within 0.01 seconds and 500 ° C. or lower within 2 seconds from the start of cooling; (B) an intermediate reaction step in which the reaction gas after the first cooling step is maintained in a temperature range of 500 ° C. to 950 ° C. for a period of 0.01 seconds to 5 seconds; and (c) after the intermediate reaction step. It has a 2nd cooling process which cools reaction gas to less than 500 degreeC, The manufacturing method of the trichlorosilane characterized by the above-mentioned.
[2] The method for producing trichlorosilane according to the above [1], wherein the ultimate cooling temperature of the reaction gas is 100 ° C. or higher and 500 ° C. or lower in the first cooling step.
[3] The method for producing trichlorosilane as described in [1] or [2] above, wherein the reaction gas is maintained at 550 ° C. or higher and 800 ° C. or lower in the intermediate reaction step.
[4] The reaction gas is cooled to an ultimate cooling temperature of 100 ° C. to less than 500 ° C. in the first cooling step, and the cooled reaction gas is maintained at a temperature of 550 ° C. to 800 ° C. in the intermediate reaction step [1] -The manufacturing method of the trichlorosilane as described in any one of said [3].
[5] A method for using trichlorosilane, wherein the trichlorosilane recovered by the method described in any one of [1] to [4] above is used as part of a raw material for producing polycrystalline silicon.

  In the production method of the present invention, a raw material tetrachlorosilane and hydrogen are converted at a temperature of 1000 to 1900 ° C. to generate a reaction gas containing trichlorosilane, dichlorosilylene, hydrogen chloride, and a higher order silane compound. The reaction gas extracted from the converter is cooled to 600 ° C. or higher within 0.01 seconds and 500 ° C. or lower within 2 seconds from the start of cooling, and preferably the ultimate cooling temperature is 100 ° C. or higher to lower than 500 ° C. Therefore, the decomposition of trichlorosilane contained in the reaction gas (reverse reaction of the above formula [3]) can be effectively suppressed.

  In the first cooling step, a small amount of polymer is generated by quenching of the reaction gas. The quenched reaction gas is heated to a temperature of 500 ° C. to 950 ° C., preferably 550 ° C. to 800 ° C. in the intermediate reaction step. The range is maintained for 0.01 second to 5 seconds, so that the polymer contained in the reaction gas is sufficiently decomposed. On the other hand, since the upper limit of the holding temperature in the intermediate reaction step is limited to 950 ° C. or lower, preferably 800 ° C. or lower, the holding temperature is sufficiently lower than the cooling start temperature (approximately 1000 ° C. or higher) in the first cooling step, Therefore, there is little decomposition of trichlorosilane in the reaction gas.

  The reaction gas obtained by decomposing the polymer in the intermediate reaction step is finally cooled to less than 500 ° C. in the second cooling step to recover trichlorosilane.

  In the production method of the present invention, since the decomposition of the trichlorosilane and the production of the polymer contained in the reaction gas are suppressed through the first cooling step and the intermediate reaction step, the trichlorosilane can be recovered with a high recovery rate. In addition, since the reaction gas after the second cooling does not substantially contain a polymer, troubles such as pipe adhesion can be reduced, and the soundness of the apparatus can be maintained.

Production process diagram from the production of polycrystalline silicon to the conversion reaction. The graph which shows the relationship of the product gas with the reaction temperature in a conversion reaction. The conceptual diagram of a cooling process. 6 is a graph showing a temperature change in Example 2.

  Hereinafter, the manufacturing method of the trichlorosilane which concerns on this invention is demonstrated concretely based on embodiment.

  In the method for producing trichlorosilane of the present invention, a raw material tetrachlorosilane and hydrogen are converted and reacted at a temperature of 1000 to 1900 ° C. to generate a reaction gas containing trichlorosilane, dichlorosilylene, hydrogen chloride, and a higher order silane compound. In the method of recovering trichlorosilane by cooling the reaction gas, (a) a first cooling step of cooling to 600 ° C. or more within 0.01 seconds and cooling to 500 ° C. or less within 2 seconds from the start of cooling; (B) an intermediate reaction step in which the reaction gas after the first cooling step is kept in a temperature range of 500 ° C. to 950 ° C. for a period of 0.01 seconds to 5 seconds; and (c) a reaction after the intermediate reaction step. It has a 2nd cooling process which cools gas to less than 500 degreeC, It is a manufacturing method of the trichlorosilane characterized by the above-mentioned.

[Polycrystalline silicon manufacturing process]
The manufacturing process and conversion reaction process of polycrystalline silicon are shown in FIG. In the manufacturing process shown in FIG. 1, raw material trichlorosilane (TCS), hydrogen, and tetrachlorosilane (silicon tetrachloride: STC) are introduced into the reactor 10. A silicon rod is installed inside the reaction furnace 10, and the source gas in contact with the surface of a red hot silicon rod (about 800 ° C. to 1200 ° C.) reacts and is generated according to the reaction [1] [2]. Silicon precipitates on the surface of the silicon rod and gradually grows into a polycrystalline silicon rod having a large diameter.

[Exhaust gas treatment process]
The gas discharged from the reactor 10 includes unreacted trichlorosilane (TCS) and hydrogen, as well as by-produced hydrogen chloride (HCl), and chlorosilanes such as silicon tetrachloride (STC), dichlorosilane, and hexachlorodisilane. Is included. The exhaust gas containing these chlorosilanes is led to the cooler 11 and cooled to around −60 ° C. (for example, −65 ° C. to −55 ° C.) to be condensed and liquefied. Here, the hydrogen remaining in a gaseous state without being liquefied is separated, supplied to the reactor 10 again as a part of the raw material gas through a purification process, and reused.

  The condensate containing chlorosilanes liquefied by the cooler 11 is introduced into the distillation step 12, trichlorosilane (TCS) is distilled and separated, and the recovered TCS is returned to the polycrystalline silicon manufacturing process and reused.

  Next, silicon tetrachloride (STC) is distilled off. This silicon tetrachloride is introduced into the conversion furnace 13 together with hydrogen, and trichlorosilane (TCS) is produced by the conversion reaction represented by the above formula [3] at a temperature of 1000 to 1900 ° C. The reaction gas containing TCS is introduced into the condensation step 15 through the cooling step 14, and TCS is recovered. The recovered TCS is returned to the polycrystalline silicon manufacturing process and reused as a raw material for manufacturing polycrystalline silicon.

[Conversion reaction process]
A feed gas containing raw material tetrachlorosilane and hydrogen is introduced into the conversion furnace 13. The raw material tetrachlorosilane to be supplied may contain disilanes, or the disilanes may be removed. The conversion furnace 13 is heated to 1000 ° C. to 1900 ° C., and the supplied raw material gas reacts to generate a reaction gas containing trichlorosilane, dichlorosilylene, hydrogen chloride, and a higher silane compound.

  When the heating temperature of the conversion furnace 13 is less than 1000 ° C., there are disadvantages that the conversion rate and the conversion speed are reduced and the apparatus is large. Moreover, when the heating temperature of the conversion furnace 13 exceeds 1900 degreeC, a conversion rate will not improve and it is uneconomical as production equipment.

FIG. 2 shows an example (equilibrium value) of the composition of the reaction product gas with respect to the reaction temperature in the conversion reaction. As shown in the figure, the gas generated by the conversion reaction contains unreacted H ₂ , SiCl ₄ , and by-products such as HCl, SiCl ₂ , and a polymer together with the target trichlorosilane.

As shown in the graph of FIG. 2, since the conversion amount of SiCl _{4 in} the conversion reaction (decreasing change amount of SiCl ₄ ) increases with temperature, the reaction temperature of the conversion reaction is preferably higher, and the conversion to SiHCl ₃ is maximum. It is more preferable to set the temperature to about 1100 ° C. or higher where the value is close to the value and the conversion to SiCl ₂ becomes remarkable. On the other hand, the higher the reaction temperature of the conversion reaction, the higher the reaction rate of the decomposition of trichlorosilane (the reverse reaction of the above reaction formula [3]) in the subsequent first cooling step. For this reason, the effect of suppressing decomposition of trichlorosilane in the first cooling step is reduced, and even if a high conversion amount of SiCl ₄ is obtained in the conversion reaction step, SiCl finally obtained through the first and second cooling steps. The conversion amount of ₄ is not so large. Therefore, in order to sufficiently exhibit the rapid cooling effect in the first cooling step and obtain a high SiCl ₄ conversion amount after cooling, the reaction temperature in the first conversion step is preferably 1300 ° C. or lower. From the above, the reaction temperature in the conversion reaction step is preferably 1100 to 1300 ° C.

[Cooling process]
An example of the cooling step 14 is shown in FIG. 3, and the change in the cooling temperature of the reaction gas is shown in FIG. As shown in the figure, the reaction gas extracted from the conversion furnace 13 is introduced into the first cooler 21 in the first cooling step, and is over 600 ° C. within 0.01 seconds from the start of cooling, and within 500 seconds within 2 seconds. Cool to below ℃. The reaction gas after the first cooling step is introduced into the intermediate cooler 22 of the intermediate reaction step, and is held in a temperature range of 500 ° C. to 950 ° C. for a period of 0.01 seconds to 5 seconds. Next, the reaction gas after the intermediate reaction step is introduced into the second cooler 23 of the second cooling step, and after being cooled to below 500 ° C., is sent to the distillation separation step 15 of trichlorosilane.

[First cooling]
In the first cooling step, cooling is performed at a cooling rate that sufficiently suppresses decomposition of trichlorosilane (reverse reaction of the above reaction formula [3]). Specifically, the cooling is performed at 600 ° C. or more within 0.01 seconds from the start of cooling and 500 ° C. or less within 2 seconds. Preferably, the reaction gas having a temperature of 600 ° C. or more is cooled to 100 ° C. or more and 500 ° C. or less during 0.01 seconds to 2 seconds within 0.01 seconds from the start of cooling. If cooled under this condition, decomposition of trichlorosilane contained in the reaction gas (reverse reaction of the above formula [3]) can be sufficiently suppressed even on a mass production scale, and excessive cooling conditions are not obtained. The production of the polymer can be suppressed to a small amount.

  In the first cooling step, the reaction gas is cooled to 600 ° C. or more within 0.01 seconds from the start of cooling and to 500 ° C. or less within 2 seconds, whereby the decomposition of trichlorosilane in the reaction gas is suppressed. Therefore, a decrease in the amount of trichlorosilane in the reaction gas can be suppressed. Specifically, the conversion rate of trichlorosilane contained in the reaction gas after the first cooling step maintains 23% to 26.7% in Examples 1 to 15. Moreover, the production | generation of a polymer is suppressed by the said cooling conditions, The polymer production rate in reaction gas can be made into about 0.1%-2%. Specifically, in Examples 1 to 15, the polymer production rate contained in the reaction gas after the first cooling step is 0.1% to 1.6%.

  When the cooling rate is faster than the above conditions, that is, when the reaction gas is cooled to less than 600 ° C. within less than 0.01 second from the start of cooling, the decomposition of trichlorosilane is suppressed, but the amount of polymer produced is reduced. It becomes 2-3% or more, and the load in an intermediate reaction process increases. Specifically, since the reaction temperature and reaction time required to sufficiently decompose the polymer in the intermediate reaction step increase, the amount of heat required for heating increases, and the reaction vessel in the intermediate reaction step increases in size. It is not preferable. On the other hand, if the cooling rate of the first cooling is slower than the above conditions, the decomposition of trichlorosilane in the reaction gas proceeds and the recovery rate of trichlorosilane decreases, which is not preferable.

  The ultimate cooling temperature in the first cooling step is suitably 500 ° C. or less within 2 seconds, and preferably 100 ° C. or more and 500 ° C. or less. When the time to reach 500 ° C. or lower is longer than 2 seconds, decomposition of trichlorosilane contained in the reaction gas proceeds. For example, in Examples 14 to 15, the cooling arrival time is 0.5 seconds and 2.0 seconds longer than those in Examples 1 to 13, and the cooling arrival time is within 2 seconds, but the amount of trichlorosilane in the reaction gas The TCS conversion rate tends to be as low as 23.0% to 23.9%.

  In the first cooling step, it is not preferable to cool the reaction gas to less than 100 ° C. because chlorosilanes in the reaction gas may be condensed or deposited in the apparatus. If the temperature reached by cooling is 100 ° C. or higher, this condensation or precipitation is unlikely to occur, and the reaction gas can be handled as a gas. In addition, when a part of reaction gas condenses in a 1st cooling process, when introduce | transducing this to an intermediate reaction process, it is preferable to supply, after preheating and gasifying.

[Intermediate reaction]
The reaction gas after the first cooling is introduced into the intermediate cooler 22 of the intermediate reaction step, and the temperature ranges from 500 ° C. to 950 ° C., preferably from 550 ° C. to 800 ° C., from 0.01 seconds to 5 seconds. Hold for the following time. By maintaining the reaction gas after the first cooling in the above temperature range, the polymer generated in the first cooling can be decomposed while suppressing the decomposition of trichlorosilane.

  As shown in FIG. 4, for example, in the first cooling, the reaction gas is 600 ° C. or more within 0.01 seconds from the start of cooling and is cooled to 100 ° C. to 500 ° C. within 2 seconds (in FIG. 4, reached). In the intermediate reaction step, the cooling temperature is slightly increased and maintained in a temperature range of 550 ° C. to 800 ° C. (550 ° C. in FIG. 4), thereby decomposing the polymer produced in the first cooling step. The reaction can proceed. Moreover, since decomposition | disassembly of a trichlorosilane is suppressed in this temperature range, content of a trichlorosilane does not reduce substantially.

  Furthermore, while the first cooling step is a rapid quenching step from a conversion reaction temperature of 1000 ° C. or higher, the intermediate reaction step is different from the strict cooling rate of the first cooling step, so the cooling temperature can be controlled. Easy.

  When the holding temperature in the intermediate reaction step is less than 500 ° C., the polymer decomposition reaction is very slow, and the produced polymer cannot be reduced. For example, since the holding temperature in the intermediate reaction step of Comparative Example 2 is 480 ° C., the polymer production rate contained in the reaction gas after the second cooling step is as high as 0.8%.

On the other hand, when the holding temperature in the intermediate reaction step exceeds 950 ° C., the decomposition reaction rate of trichlorosilane increases and the content of trichlorosilane in the reaction gas decreases. For example, in Comparative Example 2, since the holding temperature in the intermediate reaction step is 960 ° C., the amount of trichlorosilane in the reaction gas after the second cooling step is reduced, and the TCS conversion rate is reduced to 23.7%. Furthermore, if the holding temperature in the intermediate reaction step is too high, the amount of dichlorosilylene (SiCl ₂ ) that forms the polymer increases, which is not preferable because the polymer is generated again during the second cooling. On the other hand, if the intermediate reaction temperature exceeds 950 ° C., the amount of heat for heating to this temperature increases, which is uneconomical.

  In the intermediate reaction step, the time for maintaining the reaction gas in the above temperature range is 0.01 seconds or more and 5 seconds or less. If the holding time is less than 0.01 seconds, the polymer is not sufficiently decomposed. On the other hand, if the holding time exceeds 5 seconds, the amount of polymer decomposition does not change. .

  A preferred temperature range for the intermediate reaction step is from 550 ° C to 800 ° C. In this temperature range, the polymer decomposition reaction proceeds in about 0.02 seconds to about 3 seconds, so that the equipment for the intermediate reaction process can be made relatively small and the temperature and reaction time can be easily controlled.

  In the intermediate reaction step, by maintaining the reaction gas after the first cooling in the above temperature range for the above time, the polymer produced in the first cooling step reacts with hydrogen chloride in the reaction gas and decomposes into trichlorosilane or tetrachlorosilane. As a result, the amount of polymer can be reduced.

[Second cooling]
The reaction gas after the intermediate reaction step is introduced into the second cooler 23 of the second cooling step, cooled again to below 500 ° C., and then sent to the distillation separation step 15 for trichlorosilane.

[Introduction of gas]
In the first cooling step, at least one of tetrachlorosilane (SiCl ₄ ) and hydrogen may be introduced into the first cooler 21. By increasing the SiCl ₄ concentration and the H ₂ concentration in the reaction gas in the first cooling step, it is possible to promote the generation of trichlorosilane in the early stage of cooling and suppress the decomposition of trichlorosilane.

The amount of SiCl ₄ and H ₂ introduced into the first cooling step is preferably in the range of 0.01 to 10 molar ratios when the molar amount of SiCl ₄ supplied in the conversion step is 1. If the introduction amount is less than 0.01, the increase amount of trichlorosilane by introduction is small, and even if it is supplied in excess of 10, the increase amount of trichlorosilane is not greatly changed, which is uneconomical.

Introducing hydrogen chloride into the intercooler 22 in the intermediate reaction step can further promote the production of trichlorosilane by polymer decomposition. The amount of hydrogen chloride to be introduced is preferably in the range of 0.01 to 10 molar ratio when the molar amount of SiCl ₄ supplied in the conversion reaction is 1. If the introduction amount is less than 0.01, the effect on the decomposition reaction of the polymer due to the introduction is small, and even if it is supplied in excess of 10, the effect on the decomposition reaction is not increased, which is uneconomic.

  In the second cooling step, by mixing hydrogen chloride with the reaction gas in a temperature range of 350 ° C. or higher, the reaction between hydrogen chloride and the polymer is promoted, and the remaining polymer is slightly lost and one of the decomposition products is lost. It is possible to generate trichlorosilane, which is one of them, and increase the recovery rate of trichlorosilane.

Examples of the present invention are shown below together with comparative examples. These results are shown in Table 1. The conversion rate of SiHCl ₃ (mol% -Si) in Table 1 is the production rate of trichlorosilane to the raw material silicon tetrachloride (SiCl ₄ ) (SiHCl ₃ / SiCl ₄ ), and the polymer production rate (mol% -Si) Is the ratio of silicon contained in the produced polymer to the raw material silicon tetrachloride (SiCl ₄ ) (Si / SiCl _{4 in the} polymer).

[Examples 1 to 11]
Using a mixed gas of hydrogen and silicon tetrachloride (molar ratio of H ₂ and SiCl ₄ of 2.0, H ₂ / SiCl ₄ = 2.0) as a raw material, introducing the raw material gas into the conversion furnace and reacting at 1100 ° C I let you. The product gas after the reaction was introduced into the first cooler and cooled to 300 ° C. Table 1 shows the reaction gas temperature, cooling attainment temperature (cooling lower limit temperature), and cooling lower limit temperature at 0.01 seconds from the start of cooling. The reaction gas after the first cooling was introduced into the intercooler, and the cooling temperature was slightly raised and maintained at the temperature and time shown in Table 1. The reaction gas after the intermediate cooling was introduced into the second cooler, and the cooling temperature was lowered again to cool to 200 ° C. within 0.3 seconds. Table 1 shows the conversion rate of trichlorosilane and the production rate of the polymer contained in the reaction gas after the first cooling, the conversion rate of trichlorosilane and the production rate of the polymer contained in the reaction gas after the second cooling.

[Examples 12 to 15]
The conversion reaction was performed under the same conditions as in Example 1 except that the cooling conditions of the first cooling step were set as shown in Table 1, and the product gas after the reaction was introduced into the first cooler and cooled. Table 1 shows the reaction gas temperature, cooling attainment temperature (cooling lower limit temperature), and cooling lower limit temperature at 0.01 seconds from the start of cooling. The reaction gas after the first cooling was introduced into the intercooler, and the cooling temperature was slightly raised and maintained at the temperature and time shown in Table 1. The reaction gas after the intermediate cooling was introduced into the second cooler, and the cooling temperature was lowered again to cool to 200 ° C. within 0.3 seconds. Table 1 shows the conversion rate of trichlorosilane and the production rate of the polymer contained in the reaction gas after the first cooling, the conversion rate of trichlorosilane and the production rate of the polymer contained in the reaction gas after the second cooling.

[Comparative Examples 1-4]
The conversion reaction was performed under the same conditions as in Example 1 except that the cooling conditions of the first cooling step were set as shown in Table 1, and the product gas after the reaction was introduced into the first cooler and cooled. Table 1 shows the reaction gas temperature, cooling attainment temperature (cooling lower limit temperature), and cooling lower limit temperature at 0.01 seconds from the start of cooling. The reaction gas after the first cooling was introduced into the intercooler, and the cooling temperature was slightly raised and maintained at the temperature and time shown in Table 1. The reaction gas after the intermediate cooling was introduced into the second cooler, and the cooling temperature was lowered again to cool to 200 ° C. within 0.3 seconds. Table 1 shows the conversion rate of trichlorosilane and the production rate of the polymer contained in the reaction gas after the first cooling, the conversion rate of trichlorosilane and the production rate of the polymer contained in the reaction gas after the second cooling.

  As shown in Table 1, in all of Examples 1 to 15, the conversion rate of trichlorosilane was 23% or more, but the polymer production rate was 0.2% or less, and trichlorosilane was efficiently recovered. In addition, the amount of polymer is greatly reduced, and the burden of removing the polymer adhering to the facility is greatly reduced.

  On the other hand, Comparative Example 1 is an example in which the cooling temperature at 0.01 second from the start of cooling in the first cooling step is too low (440 ° C.), and the conversion rate of trichlorosilane is similar to that in Example 1. The polymer production rate is 0.5%, and more polymer is produced than in Example 1.

Comparative Example 2 is an example in which the holding temperature in the intermediate reaction step is too high (960 ° C.), and the conversion rate of trichlorosilane is low and the polymer production rate is also high.
Comparative Example 3 is an example in which the holding temperature in the intermediate reaction step is low (480 ° C.) and the holding time is long. The conversion rate of trichlorosilane is close to that of Example 1, but the production rate of the polymer is high.
Comparative Example 4 is an example in which the cooling rate in the first cooling step is low (500 ° C. in 2.4 seconds) and the intermediate reaction step is not performed, and 200 in the second cooling step directly after the first cooling step. Cooled to ° C. For this reason, although the conversion rate to the polymer was kept low, the conversion rate of trichlorosilane was as low as 20%.

10-reactor, 11-cooler, 12-distillation process, 13-conversion furnace, 14-cooling process, 15-TCS distillation separation process, 21-first cooler, 22-intercooler, 23-second cooler vessel.

Claims (5)

The raw material tetrachlorosilane and hydrogen are converted and reacted at a temperature of 1000 to 1900 ° C. to generate a reaction gas containing trichlorosilane, dichlorosilylene, hydrogen chloride, and a higher silane compound, and the reaction gas is cooled to trichlorosilane. In the method of recovering
(A) a first cooling step in which the reaction gas extracted from the converter is cooled to 600 ° C. or more within 0.01 seconds and 500 ° C. or less within 2 seconds from the start of cooling;
(B) an intermediate reaction step of holding the reaction gas after the first cooling step in a temperature range of 500 ° C. to 950 ° C. for a period of 0.01 seconds to 5 seconds;
(C) A method for producing trichlorosilane, comprising a second cooling step of cooling the reaction gas after the intermediate reaction step to less than 500 ° C.
The method for producing trichlorosilane according to claim 1, wherein in the first cooling step, the ultimate cooling temperature of the reaction gas is 100 ° C or higher and 500 ° C or lower.
The method for producing trichlorosilane according to claim 1 or 2, wherein the reaction gas is maintained at 550 ° C to 800 ° C in the intermediate reaction step.
The reaction gas is cooled to an ultimate cooling temperature of 100 ° C to 500 ° C in the first cooling step, and the cooled reaction gas is maintained at a temperature of 550 ° C to 800 ° C in the intermediate reaction step. A method for producing trichlorosilane as described in any of the above.
The utilization method of the trichlorosilane which uses the trichlorosilane collect | recovered by the method in any one of Claims 1-4 as a part of manufacturing raw material of a polycrystalline silicon.

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