Method and system for synthesizing trichlorosilane and silicon tetrachloride by using trichlorosilane by-product

Abstract

The invention belongs to the technical field of chlorosilane synthesis, and relates to a method and a synthesis system for synthesizing trichlorosilane and silicon tetrachloride by using trichlorosilane by-products. The method comprises the following steps: reacting a trichlorosilane by-product with excessive hydrogen chloride gas in a reaction tower under the irradiation of ultraviolet light, recovering the hydrogen chloride gas to obtain a reaction crude product, rectifying and separating the reaction crude product to obtain trichlorosilane, and co-producing silicon tetrachloride. The synthesis system comprises a raw material reaction system, a trichlorosilane rectification system and a silicon tetrachloride rectification system, the raw material reaction system comprises a reaction tower, a transparent quartz glass wall is arranged in the reaction tower, and ultraviolet light penetrates through the wall to irradiate raw materials for reaction. According to the method, hexachlorodisilane in the trichlorosilane by-product can be efficiently converted at low cost, the method is simple, conditions are mild, catalysis is not needed, high-boiling emission is reduced, the method is green and environmentally friendly, the purity of obtained trichlorosilane is larger than 99.5%, the purity of silicon tetrachloride is larger than 99%, and the reaction yield is larger than 80%.

Description

Technical Field

[0001] The invention belongs to the technical field of chlorosilane synthesis, and relates to a method and a synthesis system for synthesizing trichlorosilane and silicon tetrachloride by utilizing trichlorosilane byproduct. Background Art

[0002] Silicon powder and hydrogen chloride are used to prepare trichlorosilane in a synthesis furnace, and dichlorosilane, silicon tetrachloride, hexachlorodisilane and other impurities are produced as by-products. Dichlorosilane can be reversed to prepare trichlorosilane, which is used as silane epitaxial gas and polymer synthesis chain extender, etc. Silicon tetrachloride can be used to synthesize sealants and other crosslinking agents. Hexachlorodisilane is stable in nature and is a colorless and low-volatile moisture-sensitive chemical. It is often used as a highly pure material precursor and plays an important role in many advanced thin film deposition processes such as semiconductor storage and logic chip manufacturing processes. It can be esterified to prepare hexaalkoxydisilane, which is used to manufacture thin films, semiconductors and other products. However, the proportion of hexachlorodisilane in trichlorosilane synthesis is less than 0.5%, and it is difficult to purify high-purity hexachlorodisilane. Silicone monomer companies are more concerned about how to design a simple device to catalyze hexachlorodisilane into trichlorosilane monomer with high economic value for the company in the synthesis system at a low cost. Summary of the invention

[0003] Based on this, the object of the present invention is to provide a method for synthesizing trichlorosilane and silicon tetrachloride using trichlorosilane byproducts, which can continuously and efficiently convert hexachlorodisilane in the trichlorosilane byproduct into trichlorosilane and silicon tetrachloride which are in great demand in the functional silane industry, thereby reducing the emission of high-boiling trichlorosilane byproducts and saving post-processing costs.

[0004] The invention also provides a synthesis system used in the method, which is simple and low in cost.

[0005] To achieve the above object, the present invention adopts the following technical solutions: The invention provides a method for synthesizing trichlorosilane and silicon tetrachloride by utilizing trichlorosilane byproducts. The trichlorosilane byproducts are reacted with excess hydrogen chloride gas under ultraviolet light irradiation, and the hydrogen chloride gas is recovered to obtain a crude reaction product. The crude reaction product is separated by rectification to obtain trichlorosilane and silicon tetrachloride is co-produced.

[0006] Furthermore, the trichlorosilane by-product contains hexachlorodisilane, and the hexachlorodisilane accounts for more than 90%; the moisture content of the hydrogen chloride gas is ≤300ppm; and the molar ratio of the hexachlorodisilane to the hydrogen chloride gas is 1:5-10.

[0007] Furthermore, the wavelength range of the ultraviolet light is 200-380nm; the power of the ultraviolet light source is 30-50W, including a high-pressure mercury lamp, a low-pressure mercury lamp or an LED light source, preferably an LED light source, and the LED light source is preferably ring-shaped.

[0008] Furthermore, the reaction is carried out under the conditions of an initial pressure of 0.3-2.0 MPa and a temperature of 60-80°C.

[0009] Furthermore, the crude reaction product is distilled and separated at 33-35° C. to obtain trichlorosilane, and then distilled and separated at 57-59° C. to obtain silicon tetrachloride.

[0010] The present invention further provides a synthesis system, which is used in a method for synthesizing trichlorosilane and silicon tetrachloride using trichlorosilane byproduct, and comprises a raw material reaction system, a trichlorosilane distillation system and a silicon tetrachloride distillation system.

[0011] Furthermore, the raw material reaction system includes a trichlorosilane byproduct storage device, a flow meter, a reaction tower, a cooling device and a reaction crude product storage device connected in sequence through pipelines. The reaction tower is provided with a transparent wall, and ultraviolet light irradiates the raw material through the transparent wall. The ultraviolet light irradiates the raw material through the transparent wall to cause a reaction between the raw materials. The ultraviolet light can break the Si-Si bond in hexachlorodisilane to produce trimethylsilyl radicals, and the radicals react with hydrogen chloride to obtain trichlorosilane and silicon tetrachloride; the transparent wall has good light transmittance and pressure resistance, and can realize continuous irradiation of ultraviolet light, continuously generate trimethylsilyl radicals, and the radicals react with hydrogen chloride to continuously generate trichlorosilane and silicon tetrachloride.

[0012] Furthermore, the transparent wall is located in the lower middle part of the reaction tower, and its height is 1 / 4 to 1 / 3 of the height of the reaction tower. The material of the transparent wall includes quartz glass.

[0013] Furthermore, the reaction tower is provided with a hydrogen chloride gas inlet at the lower part of the wall; the upper wall of the reaction tower is provided with a feed port and a discharge port, the feed port is connected to a pipeline of the flow meter, and the discharge port is connected to the cooling device.

[0014] Furthermore, the trichlorosilane by-product storage device is used to store trichlorosilane by-products, and the flow meter controls the trichlorosilane by-products to enter the reaction tower from the feed port on the upper wall of the reaction tower at a flow rate of 20-40 L / h.

[0015] Furthermore, the cooling device includes a water cooling device and a deep cooling device. The product after the raw material reaction flows out from the discharge port at the top of the reaction tower and enters the cooling device. After being cooled by the water cooling device and the deep cooling device in turn, a crude reaction product is obtained. The crude reaction product storage device is used to store the crude reaction product.

[0016] Furthermore, the trichlorosilane distillation system includes a flow meter 2, a distillation tower 1, a distillation condenser 1 and a trichlorosilane finished product storage device connected in sequence through pipelines; the silicon tetrachloride distillation system includes a distillation tower 2, a distillation condenser 2 and a silicon tetrachloride finished product storage device connected in sequence through pipelines; the distillation tower 1 is connected to the flow meter 2 and the distillation tower 2 respectively; the flow meter 2 is connected to the reaction crude product storage device.

[0017] Furthermore, the crude reaction product in the crude reaction product storage device enters into the distillation tower one at a certain flow rate controlled by flow meter two, undergoes distillation separation at 33-35° C., and then is cooled by the distillation condenser one to obtain trichlorosilane, which is stored in the trichlorosilane finished product storage device.

[0018] Furthermore, the crude product of the reaction is distilled to obtain trichlorosilane, which enters distillation tower 2 through the bottom of distillation tower 1 and is distilled and separated at 57-59° C., and then cooled in distillation condenser 2 to obtain silicon tetrachloride, which is stored in the silicon tetrachloride finished product storage device.

[0019] The beneficial effects of the present invention are: 1. The method for synthesizing trichlorosilane and silicon tetrachloride using trichlorosilane byproduct provided by the present invention can efficiently and low-cost convert hexachlorodisilane produced as a byproduct in the trichlorosilane synthesis system into trichlorosilane and silicon tetrachloride which are in great demand in the functional silane industry. The synthesis method is simple, the conditions are mild, no catalysis is required, high boiling point emissions are reduced, and it is green and pollution-free.

[0020] 2. The method provided by the present invention for synthesizing trichlorosilane and silicon tetrachloride using trichlorosilane byproducts has good purity and high yield, and can be widely used in the functional silane industry.

[0021] 3. In the synthesis system provided by the present invention, a transparent wall is provided on the reaction tower of the raw material reaction system. The transparent wall has good light transmittance and pressure resistance, and can realize continuous irradiation of ultraviolet light to break the Si-Si bond in hexachlorodisilane to generate free radicals. The free radicals react with hydrogen chloride to continuously generate trichlorosilane and silicon tetrachloride.

[0022] 4. The synthesis system provided by the present invention can obtain high-purity trichlorosilane and silicon tetrachloride by using a simple trichlorosilane distillation system and a silicon tetrachloride distillation system, thereby shortening the production cycle, reducing the complexity of the production equipment, and saving the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Attached Figure 1 A schematic diagram of the structure of the synthesis system provided by the present invention; Attached Figure 2 This is an enlarged view of the raw material reaction system structure in the synthesis system provided by the present invention; Attached Figure 3 This is an enlarged structural diagram of the trichlorosilane distillation system in the synthesis system provided by the present invention; Attached Figure 4 This is an enlarged structural diagram of the silicon tetrachloride distillation system in the synthesis system provided by the present invention; In the figure, 1 is a trichlorosilane by-product storage tank, 2 is a flow meter 1, 3 is a reaction tower, 4 is a water cooler, 5 is a deep freezer, 6 is a reaction crude product storage tank, 7 is a flow meter 2, 8 is a distillation tower 1, 9 is a distillation condenser 1, 10 is a trichlorosilane finished product storage tank, 11 is a distillation tower 2, 12 is a distillation condenser 2, and 13 is a silicon tetrachloride finished product storage tank. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. The embodiments mentioned are all implemented on the premise of the technical solutions of the present invention, and detailed implementation processes are given, but it should be stated that the protection scope of the present invention is not limited to the following embodiments.

[0026] In the following examples of the present invention, trichlorosilane and silicon tetrachloride were synthesized by using the method and synthesis system provided by the present invention, using trichlorosilane byproduct and hydrogen chloride gas under ultraviolet light irradiation.

[0027] First, silicon powder and hydrogen chloride gas are reacted to prepare crude trichlorosilane, and after distilling trichlorosilane and silicon tetrachloride, the high boiling point is distilled and enriched to obtain a byproduct with a high hexachlorodisilane content used in the embodiment of the present invention, wherein the hexachlorodisilane accounts for more than 90%. The hydrogen chloride gas in the embodiment is a dry gas with a water content of ≤300ppm, and the gas is the same as the gas used in the preparation of trichlorosilane by the reaction of silicon powder.

[0028] The synthetic system structure used in the embodiment is as follows Figure 1-4 As shown, the system includes a raw material reaction system ( Figure 2 )、Trichlorosilane distillation system( Figure 3) and silicon tetrachloride distillation system ( Figure 4 The raw material reaction system includes a trichlorosilane byproduct storage tank 1, a flow meter 2, a reaction tower 3, a cooling device and a reaction crude product storage tank 6 which are sequentially connected through pipelines.

[0029] The trichlorosilane byproduct storage tank 1 is used to store the trichlorosilane byproduct, and the flowmeter 2 controls the flow of the trichlorosilane byproduct. A trichlorosilane byproduct feed port is provided on the upper wall of the reaction tower 3, and the feed port is connected to the flowmeter 2 pipeline. The flowmeter 2 controls the trichlorosilane byproduct to enter the reaction tower 3 at a flow rate of 20~40L / h. The reaction tower 3 is provided with a hydrogen chloride gas inlet at the lower part of the wall, and the dry hydrogen chloride gas enters the reaction tower 3 from the lower part of the reaction tower 3 through the hydrogen chloride gas inlet. The initial pressure of the reaction tower 3 is 0.3~2.0MPa, and the temperature is 60~80℃. The feed molar ratio of hexachlorodisilane to hydrogen chloride gas in the trichlorosilane byproduct is 1:5~10.

[0030] A transparent wall is provided in the middle and lower part of the reaction tower 3, and ultraviolet light irradiates trichlorosilane byproduct and hydrogen chloride gas through the transparent wall. The ultraviolet light can break the Si-Si bond in the hexachlorodisilane in the trichlorosilane byproduct to generate free radicals, and the free radicals react with hydrogen chloride to obtain trichlorosilane and silicon tetrachloride; the ultraviolet light source adopts a ring-shaped LED light source with a power of 30-50W and a wavelength of 200-380nm; the transparent wall has good light transmittance and pressure resistance, and can realize continuous irradiation of ultraviolet light, continuously generate trimethylsilyl free radicals, and the free radicals react with hydrogen chloride to continuously generate trichlorosilane and silicon tetrachloride.

[0031] The reaction tower 3 used in the embodiment is a tower cylinder with a height of 1m and a diameter of 20cm; wherein the height of the transparent wall is 30cm and the material is quartz glass. The hydrogen chloride gas inlet is 5cm away from the bottom of the reaction tower 3, the feed inlet is 15cm away from the top of the reaction tower 3, and the discharge port is 5cm away from the top of the reaction tower 3.

[0032] The cooling device includes a water cooler 4 and a deep cooler 5 (the deep cooler 5 contains brine with a sodium chloride mass concentration of 24% and a temperature of -25~-20°C). The product after the raw material reaction flows out from the discharge port on the reaction tower 3 and enters the water cooler 4 and the deep cooler 5 in sequence. After cooling, a crude reaction product is obtained, which is stored in a crude reaction product storage tank 6.

[0033] The trichlorosilane distillation system comprises a flow meter 2 7, a distillation tower 1 8, a distillation condenser 1 9 and a trichlorosilane finished product storage tank 10 which are sequentially connected through pipelines.

[0034] The crude reaction product storage tank 6 is connected to the flow meter 2 7. The crude trichlorosilane enters the distillation tower 1 8 at a certain flow rate controlled by the flow meter 2 7, and is distilled and separated at 33-35°C. After being cooled by the distillation condenser 1 9, trichlorosilane is obtained and stored in the trichlorosilane finished product storage tank 10.

[0035] The silicon tetrachloride distillation system comprises a second distillation tower 11, a second distillation condenser 12 and a silicon tetrachloride finished product storage tank 13 which are sequentially connected by pipelines.

[0036] The crude product of the reaction is distilled to obtain trichlorosilane, which enters the distillation tower 11 from the bottom of the distillation tower 8 and is distilled and separated at 57-59° C. It is then cooled in the distillation condenser 12 to obtain silicon tetrachloride, which is stored in the silicon tetrachloride finished product storage tank 13.

[0037] Example 1 The trichlorosilane byproduct with a hexachlorodisilane content of 90.8% and the hydrogen chloride gas are respectively fed from the trichlorosilane byproduct storage tank 1 through a flow meter 2 and the hydrogen chloride raw material tank and a gas flow meter to maintain a molar ratio of hydrogen chloride to hexachlorodisilane of 5:1, wherein the trichlorosilane byproduct enters the reaction tower 3 with an initial pressure of 0.4MPa and a temperature of 62°C from the feed port at the upper part of the reaction tower 3 at a rate of 20L / h. At the same time, dry hydrogen chloride is fed from the hydrogen chloride gas inlet at the lower part of the reaction tower 3. An LED ring light source with a power of 50W and a wavelength of 275nm is used to continuously irradiate the raw material through the transparent wall of the reaction tower 3, and enters the reaction crude product storage tank 6 from the discharge port at the upper part of the reaction tower 3, and enters the distillation tower 8 through a flow meter 7. After 12 hours, about 340.4kg of hexachlorodisilane and 141.7m 3 Hydrogen chloride, except low-recovery hydrogen chloride, is distilled and separated at 33~35℃ to obtain 141.5kg of trichlorosilane with a purity of 99.8%, and the reaction yield is 82.5%; distilled and separated at 57~59℃ to obtain 177.4kg of silicon tetrachloride with a purity of 99.4%.

[0038] Example 2 The trichlorosilane byproduct with a hexachlorodisilane content of 92.2% and the hydrogen chloride gas are respectively fed from the trichlorosilane byproduct storage tank 1 through a flow meter 2 and the hydrogen chloride raw material tank and a gas flow meter to maintain a molar ratio of hydrogen chloride to hexachlorodisilane of 7:1, wherein the trichlorosilane byproduct enters the reaction tower 3 with an initial pressure of 0.9 MPa and a temperature of 70°C from the feed port at the upper part of the reaction tower 3 at a rate of 25 L / h. At the same time, dry hydrogen chloride is fed from the hydrogen chloride gas inlet at the lower part of the reaction tower 3. An LED ring light source with a power of 30 W and a wavelength of 245 nm is used to continuously irradiate the raw material through the transparent wall of the reaction tower 3, and enters the reaction crude product storage tank 6 from the discharge port at the upper part of the reaction tower 3, and enters the distillation tower 8 through a flow meter 7. After 12 hours, about 432 kg of hexachlorodisilane and 251.7 m3 Hydrogen chloride, except low-recovery hydrogen chloride, is distilled and separated at 33~35℃ to obtain 181.1kg of trichlorosilane with a purity of 99.84%, and the reaction yield is 83.2%; distilled and separated at 57~59℃ to obtain 227kg of silicon tetrachloride with a purity of 99.4%.

[0039] Example 3 The trichlorosilane byproduct with a hexachlorodisilane content of 93.6% and the hydrogen chloride gas are respectively fed from the trichlorosilane byproduct storage tank 1 through a flow meter 2 and the hydrogen chloride raw material tank and a gas flow meter to maintain a molar ratio of hydrogen chloride to hexachlorodisilane of 8:1, wherein the trichlorosilane byproduct enters the reaction tower 3 with an initial pressure of 1.8 MPa and a temperature of 65°C from the feed port at the upper part of the reaction tower 3 at a rate of 30 L / h. At the same time, dry hydrogen chloride is fed from the hydrogen chloride gas inlet at the lower part of the reaction tower 3. An LED ring light source with a power of 40 W and a wavelength of 245 nm is used to continuously irradiate the raw material through the transparent wall of the reaction tower 3, and enters the reaction crude product storage tank 6 from the discharge port at the upper part of the reaction tower 3, and enters the distillation tower 8 through a flow meter 7. After 10 hours, about 438.6 kg of hexachlorodisilane and 292.1 m 3 Hydrogen chloride, except low-recovery hydrogen chloride, is distilled and separated at 33~35℃ to obtain 180.94kg of trichlorosilane with a purity of 99.76%, and the reaction yield is 81.9%; 227kg of silicon tetrachloride with a purity of 99.28% is distilled and separated at 57~59℃.

[0040] Example 4 The trichlorosilane byproduct with a hexachlorodisilane content of 94.1% and the hydrogen chloride gas are respectively fed from the trichlorosilane byproduct storage tank 1 through a flow meter 2 and the hydrogen chloride raw material tank and a gas flow meter to maintain a molar ratio of hydrogen chloride to hexachlorodisilane of 10:1, wherein the trichlorosilane byproduct enters the reaction tower 3 with an initial pressure of 1.2MPa and a temperature of 70°C from the feed port at the upper part of the reaction tower 3 at a rate of 40L / h. At the same time, dry hydrogen chloride is fed from the hydrogen chloride gas inlet at the lower part of the reaction tower 3. An LED ring light source with a power of 40W and a wavelength of 245nm is used to continuously irradiate the raw material through the transparent wall of the reaction tower 3, and enters the reaction crude product storage tank 6 from the discharge port at the upper part of the reaction tower 3, and enters the distillation tower 8 through a flow meter 7. After 8 hours, about 470.3kg of hexachlorodisilane and 391.5m 3 Hydrogen chloride, except low-recovery hydrogen chloride, is distilled and separated at 33~35℃ to obtain 192.4kg of trichlorosilane with a purity of 99.74%, and the reaction yield is 81.2%; distilled and separated at 57~59℃ to obtain 241.3kg of silicon tetrachloride with a purity of 99.30%.

[0041] Comparative Example 1 The trichlorosilane byproduct with a hexachlorodisilane content of 85.4% and the hydrogen chloride gas are respectively fed from the trichlorosilane byproduct storage tank 1 through a flow meter 2 and the hydrogen chloride raw material tank and a gas flow meter to maintain a molar ratio of hydrogen chloride to hexachlorodisilane of 7:1, wherein the trichlorosilane byproduct enters the reaction tower 3 with an initial pressure of 0.9 MPa and a temperature of 70°C from the feed port at the upper part of the reaction tower 3 at a rate of 25 L / h. At the same time, the dry hydrogen chloride reaction tower 3 is fed to the hydrogen chloride gas inlet at the lower part. An LED ring light source with a power of 50 W and a wavelength of 275 nm is used to continuously irradiate the raw material through the transparent wall of the reaction tower 3, and the raw material enters the reaction crude product storage tank 6 from the discharge port at the upper part of the reaction tower 3, and enters the distillation tower 8 through a flow meter 7. After 12 hours, about 400.2 kg of hexachlorodisilane and 233.3 m 3 Hydrogen chloride, except low-recovery hydrogen chloride, is distilled and separated at 33~35℃ to obtain 96.8kg of trichlorosilane with a purity of 99.84%, and the reaction yield is 48%; distilled and separated at 57~59℃ to obtain 121.4kg of silicon tetrachloride with a purity of 99.4%.

[0042] Comparative Example 2 The trichlorosilane byproduct with a hexachlorodisilane content of 90.8% and the hydrogen chloride gas are respectively fed from the trichlorosilane byproduct storage tank 1 through a flow meter 2 and the hydrogen chloride raw material tank and a gas flow meter to maintain a molar ratio of hydrogen chloride to hexachlorodisilane of 7:1, wherein the trichlorosilane byproduct enters the reaction tower 3 with an initial pressure of 2.0 MPa and a temperature of 75°C from the feed port at the upper part of the reaction tower 3 at a rate of 35 L / h. At the same time, the dry hydrogen chloride reaction tower 3 is fed with the hydrogen chloride gas inlet at the lower part. An LED ring light source with a power of 40 W and a wavelength of 310 nm is used to continuously irradiate the raw material through the transparent wall of the reaction tower 3, and the raw material enters the reaction crude product storage tank 6 from the discharge port at the upper part of the reaction tower 3, and enters the distillation tower 8 through a flow meter 7. After 10 hours, about 496.4 kg of hexachlorodisilane and 289.2 m 3 Hydrogen chloride, except low-recovery hydrogen chloride, is distilled and separated at 33~35℃ to obtain 113kg of trichlorosilane with a purity of 99.78%, and the reaction yield is 45.2%; distilled and separated at 57~59℃ to obtain 141.8kg of silicon tetrachloride with a purity of 99.42%.

[0043] Comparative Example 3 The difference from Example 2 is that there is no ultraviolet irradiation, and the hydrogen chloride is recovered at low temperature after 12 hours of feeding. The hexachlorodisilane content is 90.7% as measured by gas chromatography, and almost no reaction occurs.

[0044] As can be seen from Examples 1-3, by using the synthesis system and method provided by the present invention, trichlorosilane byproduct with a hexachlorodisilane content of >90% and hydrogen chloride gas are used, the molar ratio of hexachlorodisilane to hydrogen chloride gas is 1:5-10, ultraviolet light is continuously irradiated, the light source power is 30-50W, the irradiation wavelength range is 200-380nm, the initial pressure of the reaction tower is 0.3-2.0MPa, and the temperature is 60-80°C. After removing the low-purity hydrogen chloride, trichlorosilane with a purity of 99.5% and a yield of >80% can be obtained by distillation and separation at 33-35°C, and silicon tetrachloride with a purity of >99% and a yield of >80% can be obtained by distillation and separation at 57-59°C.

[0045] Comparative Examples 1-3 and the embodiment of the present invention use the same synthesis system. Comparative Example 1 uses a trichlorosilane byproduct with a hexachlorodisilane content of less than 90% to react with hydrogen chloride gas, and in Comparative Example 2, the ultraviolet wavelength used is 310nm, which makes the free radical generation effect poor, and ultimately leads to a significant decrease in the yield of trichlorosilane and silicon tetrachloride, and the yield is less than 50%. Comparative Example 3 does not use ultraviolet light irradiation, and the hexachlorodisilane in the trichlorosilane byproduct hardly reacts with hydrogen chloride, and trichlorosilane and silicon tetrachloride products cannot be obtained.

[0046] In summary, by using the synthesis system and method provided by the present invention, continuous irradiation of ultraviolet light can be used to continuously segmentally break the Si-Si bond in the hexachlorodisilane in the trichlorosilane byproduct to produce free radicals, and the free radicals react with hydrogen chloride to continuously generate trichlorosilane and silicon tetrachloride. The synthesized trichlorosilane and silicon tetrachloride have good purity and high yield, and can be widely used in the functional silane industry. The synthesis method is simple, the conditions are mild, no catalysis is required, the high boiling emissions are reduced, and it is green and pollution-free. The synthesis system provided by the present invention reduces the complexity of production equipment, shortens the production cycle, and saves production costs.

[0047] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for synthesizing trichlorosilane and silicon tetrachloride using trichlorosilane byproduct, characterized in that: The trichlorosilane byproduct reacts with excess hydrogen chloride gas under ultraviolet light irradiation, and the hydrogen chloride gas is recovered to obtain a crude reaction product. The crude reaction product is separated by distillation to obtain trichlorosilane and co-produce silicon tetrachloride.

2. The method according to claim 1, characterized in that The trichlorosilane by-product contains hexachlorodisilane, and the hexachlorodisilane accounts for more than 90%; the molar ratio of the hexachlorodisilane to the hydrogen chloride gas is 1:5-10.

3. The method according to claim 1, characterized in that The wavelength range of the ultraviolet light is 200-380nm; the power of the ultraviolet light source is 30-50W, including a high-pressure mercury lamp, a low-pressure mercury lamp or an LED light source.

4. The method according to claim 1, characterized in that The reaction is carried out under the conditions of an initial pressure of 0.3-2.0 MPa and a temperature of 60-80°C.

5. The method according to claim 1, characterized in that The crude product of the reaction is distilled and separated at 33-35° C. to obtain trichlorosilane, and then distilled and separated at 57-59° C. to obtain silicon tetrachloride.

6. A synthesis system, characterized in that: The method for synthesizing trichlorosilane and silicon tetrachloride by using trichlorosilane byproduct as claimed in any one of claims 1 to 5 comprises a raw material reaction system, a trichlorosilane distillation system and a silicon tetrachloride distillation system.

7. The synthesis system according to claim 6, characterized in that The raw material reaction system includes a trichlorosilane byproduct storage device, a flow meter, a reaction tower, a cooling device and a reaction crude product storage device which are sequentially connected through pipelines. The reaction tower is provided with a transparent wall, and ultraviolet light irradiates the raw material through the transparent wall.

8. The synthesis system according to claim 7, characterized in that The transparent wall is located in the middle and lower part of the reaction tower, and its height is 1 / 4 to 1 / 3 of the height of the reaction tower. The material of the transparent wall includes quartz glass.

9. The synthesis system according to claim 7 or 8, characterized in that: The reaction tower is provided with a hydrogen chloride gas inlet at the lower part of the wall; the upper wall of the reaction tower is provided with a feed inlet and a discharge port, the feed inlet is connected to a pipeline of the flow meter, and the discharge port is connected to the cooling device.

10. The synthesis system according to claim 7, characterized in that The trichlorosilane distillation system comprises a flow meter 2, a distillation tower 1, a distillation condenser 1 and a trichlorosilane finished product storage device which are sequentially connected via pipelines; the silicon tetrachloride distillation system comprises a distillation tower 2, a distillation condenser 2 and a silicon tetrachloride finished product storage device which are sequentially connected via pipelines; the distillation tower 1 is respectively connected to the flow meter 2 and the distillation tower 2; the flow meter 2 is connected to the reaction crude product storage device.

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