Recovery method and recovery device of hexachlorodisilane

Abstract

The invention provides a recovery method and recovery device of hexachlorodisilane, and the recovery method of hexachlorodisilane comprises the following steps: 1) carrying out first rectification treatment on a chlorosilane solution to be recovered to obtain a first product; 2) carrying out second rectification treatment on the first product to obtain a second product; 3) carrying out adsorption treatment on the second product to obtain a third product; 4) performing photochemical reaction on a mixture containing the third product, a chlorinating agent and a photocatalyst to obtain a fourth product; 5) performing third rectification treatment on the fourth product to obtain a fifth product; and 6) carrying out fourth rectification treatment on the fifth product to obtain hexachlorodisilane. According to the recovery method of hexachlorodisilane provided by the invention, tetrachlorodisilane can be converted into hexachlorodisilane through a photochemical reaction, and through multiple times of rectification treatment and adsorption treatment, not only can the purification difficulty of hexachlorodisilane be reduced, but also the purity and recovery rate of hexachlorodisilane can be improved.

Description

Technical Field

[0001] This invention belongs to the field of polycrystalline silicon technology, and particularly relates to a method and apparatus for recovering hexachlorosilane. Background Technology

[0002] In polysilicon production, the modified Siemens process is widely used due to its mature technology. This process uses trichlorosilane and hydrogen as raw materials, and obtains polysilicon products through high-temperature reduction. The exhaust gas of this process contains unreacted trichlorosilane, hydrogen, hydrogen chloride, and the byproduct silicon tetrachloride, as well as chlorosilanes such as pentachlorosilane and hexachlorosilane, which have higher boiling points than silicon tetrachloride.

[0003] In existing technologies, silicon tetrachloride is mostly converted into trichlorosilane to be used as a raw material for polycrystalline silicon. The remaining chlorosilane residue is then directly distilled to obtain hexachlorosilane, which has higher utilization value. However, because pentachlorosilane (boiling point 131℃) and hexachlorosilane (boiling point 145℃) have similar boiling points, the hexachlorosilane obtained by distillation has low purity and low recovery rate. Therefore, developing a high-purity, high-recovery method for hexachlorosilane recovery is an urgent technical problem to be solved at this stage. Summary of the Invention

[0004] The main objective of this invention is to provide a method for recovering hexachlorosilane, which can improve the purity and recovery rate of hexachlorosilane.

[0005] The present invention also provides a device for recovering hexachlorosilane, which can improve the purity and recovery rate of hexachlorosilane.

[0006] In a first aspect, the present invention provides a method for recovering hexachlorosilane, comprising the following steps:

[0007] 1) The chlorosilane solution to be recovered is subjected to a first distillation treatment to obtain the first product;

[0008] 2) The first product is subjected to a second distillation process to obtain a second product;

[0009] 3) The second product is subjected to adsorption treatment to obtain the third product;

[0010] 4) A photochemical reaction is carried out on the mixture including the third product, the chlorinating agent and the photocatalyst to obtain the fourth product;

[0011] 5) The fourth product is subjected to a third distillation process to obtain the fifth product;

[0012] 6) The fifth product is subjected to a fourth distillation process to obtain the hexachlorosilane.

[0013] In the method for recovering hexachlorosilane as described above, the pressure of the first distillation process is 0.09 MPaG-0.11 MPaG, and the temperature is 33℃-55℃.

[0014] In the above-described method for recovering hexachlorosilane, the pressure of the second distillation process is 0.09 MPaG-0.11 MPaG, and the temperature is 57℃-80℃.

[0015] In the above-described method for recovering hexachlorosilane, the adsorption treatment is carried out at a pressure of 0.05 MPa-0.2 MPa and a temperature of 10°C-25°C.

[0016] In the hexachlorosilane recovery method described above, the photochemical reaction is carried out at a temperature of 20°C-40°C for a time of 4-24 hours.

[0017] In the method for recovering hexachlorosilane as described above, the molar ratio of chlorosilane, chlorinating agent and photocatalyst in the third product is (1-10):(1-78):(1-10).

[0018] In the method for recovering hexachlorosilane as described above, the volume ratio of the chlorinating agent to the third product is (1-2):1.

[0019] In the method for recovering hexachlorosilane as described above, the pressure of the third distillation process is 0.09 MPaG-0.11 MPaG, and the temperature is 40℃-60℃.

[0020] In the above-described method for recovering hexachlorosilane, the pressure of the fourth distillation process is 0.09 MPaG-0.11 MPaG, and the temperature is 145℃-160℃.

[0021] In a second aspect, the present invention provides a recovery apparatus for performing the recovery method of hexachlorosilane as described above, comprising a first distillation unit for performing a first distillation treatment on the chlorosilane solution to be recovered;

[0022] The second distillation unit is used to perform a second distillation process on the first product;

[0023] An adsorption unit is used to adsorb the second product.

[0024] A photochemical reaction unit is used to perform a photochemical reaction on the mixture of the third product, chlorinating agent, and photocatalyst.

[0025] The third distillation unit is used to perform a third distillation process on the fourth product;

[0026] The fourth distillation unit is used to perform a fourth distillation process on the fifth product.

[0027] The method for recovering hexachlorosilane provided by this invention can convert pentachlorosilane into hexachlorosilane through a photochemical reaction. Furthermore, through multiple distillation and adsorption treatments, it can not only reduce the difficulty of purifying hexachlorosilane, but also improve the purity and recovery rate of hexachlorosilane. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the embodiments of the present invention or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A schematic diagram of a hexachlorosilane recovery device provided by the present invention.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1-First distillation unit; 2-Second distillation unit; 3-Cooling unit; 4-Adsorption unit; 5-Buffer unit; 6-Photochemical reaction unit; 7-Third distillation unit; 8-Fourth distillation unit; 9-First storage unit; 10-Second storage unit. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] In the semiconductor industry, high-purity polysilicon is a key material for manufacturing integrated circuits and other semiconductor devices. Polysilicon production typically uses trichlorosilane (TCS) and hydrogen as raw materials, depositing silicon onto the surface of a silicon rod at high temperatures via chemical vapor deposition (CVD). However, this process generates a large number of byproducts and unreacted compounds, including silicon tetrachloride (STC), hydrogen chloride (HCl), and high-boiling-point chlorosilane compounds such as pentachlorosilane (Si₂HCl₅) and hexachlorosilane (Si₂Cl₆).

[0034] Traditionally, polysilicon manufacturers have focused on recycling and reusing silicon tetrachloride, converting it into trichlorosilane for reuse. However, the processing of high-boiling-point chlorosilanes often involves simple hydrolysis to convert them into silicon dioxide and hydrogen chloride. This approach not only causes environmental pollution but also wastes high-value compounds such as hexachlorosilane (Si₂C₁₆). Current technologies face challenges in directly purifying and recovering hexachlorosilane, primarily because its boiling points are very close to those of pentachlorosilane (145°C and 135°C, respectively), making high-purity separation difficult through conventional distillation. This separation difficulty limits the recovery efficiency and purity of hexachlorosilane, impacting its commercial value and application potential.

[0035] To solve this problem, the inventors discovered through research that converting pentachlorosilane into hexachlorosilane not only reduces the difficulty of purifying hexachlorosilane, but also improves its purity and recovery rate.

[0036] Based on this, in a first aspect, the present invention provides a method for recovering hexachlorosilane, comprising the following steps:

[0037] 1) The chlorosilane solution to be recovered is subjected to a first distillation treatment to obtain the first product;

[0038] 2) The first product is subjected to a second distillation process to obtain the second product;

[0039] 3) The second product is subjected to adsorption treatment to obtain the third product;

[0040] 4) A photochemical reaction is carried out on a mixture including the third product, a chlorinating agent, and a photocatalyst to obtain the fourth product;

[0041] 5) The fourth product is subjected to a third distillation process to obtain the fifth product;

[0042] 6) The fifth product is subjected to a fourth distillation process to obtain hexachlorosilane.

[0043] This invention uses a photochemical reaction to convert tetrachlorosilane in a chlorosilane solution into hexachlorosilane, which not only reduces the difficulty of purifying hexachlorosilane but also improves its purity and recovery rate.

[0044] Specifically, in step 1), the chlorosilane solution to be recovered includes 10.57 mol% trichlorosilane, 82.98 mol% silicon tetrachloride, 4.54 mol% hexachlorosilane, 1.91 mol% pentachlorosilane, and other impurities. The chlorosilane solution to be recovered undergoes a first distillation treatment at a temperature set above the boiling point of trichlorosilane (31.8°C) and below the boiling point of silicon tetrachloride (57.6°C) to separate trichlorosilane from the chlorosilane solution, reducing the complexity of subsequent steps. The remaining substance is the first product.

[0045] The present invention does not limit the source of the chlorosilane solution to be recycled. For example, it can come from the chlorosilane solution after the tail gas generated by the reduction furnace after the reduction reaction of trichlorosilane and hydrogen in polysilicon production is condensed to remove hydrogen.

[0046] In step 2), the first product is subjected to a second distillation process. The temperature of the second distillation process is set to be higher than the boiling point of silicon tetrachloride (57.6°C) and lower than the boiling point of hexachlorosilane (145°C) to separate silicon tetrachloride and prepare for subsequent adsorption and photochemical reactions. The remaining substance is the second product.

[0047] In step 3), after cooling, the second product is removed from the solution by resin adsorption, such as metal impurities like B and P, in order to reduce the impact of these impurities on subsequent reactions and the purity of the final product.

[0048] In step 4), the third product is buffered and then mixed with a chlorinating agent and a photocatalyst. Under blue light irradiation, a photochemical reaction is carried out to directionally convert Si-H to Si-Cl, that is, to convert pentachlorosilane to hexachlorosilane, thereby improving the recovery rate of the final hexachlorosilane. Furthermore, since there is no subsequent influence from pentachlorosilane, the purity of the final hexachlorosilane will also be improved.

[0049] The chlorinating agent used in this invention can be, for example, at least one of dichloromethane (CH2Cl2), chloroform (CHCl3), and 1,2-dichloroethane (ClCH2CH2Cl).

[0050] The photocatalyst in this invention can be, for example, neutral eosin Y, with the structure shown below:

[0051]

[0052] In step 5), the fourth product undergoes a third distillation process. The temperature of this third distillation process is set above the boiling point of the chlorinating agent but below the boiling point of hexachlorosilane (145°C) to remove excess chlorinating agent, ensuring that the final product does not contain unreacted reagents and improving the purity of hexachlorosilane. Furthermore, the chlorinating agent can be returned to participate in the photochemical reaction, saving raw materials and reducing production costs.

[0053] In step 6), the fifth product undergoes a fourth distillation process. The temperature of the fourth distillation process is set to be higher than the boiling point of hexachlorosilane (145°C) and lower than the boiling point of the photocatalyst, in order to recover hexachlorosilane. The remaining photocatalyst can be returned to continue participating in the photochemical reaction, saving raw materials and reducing production costs.

[0054] The method for recovering hexachlorosilane provided by this invention can convert pentachlorosilane into hexachlorosilane through a photochemical reaction. Furthermore, through multiple distillation and adsorption treatments, it can not only reduce the difficulty of purifying hexachlorosilane, but also improve the purity and recovery rate of hexachlorosilane.

[0055] In some embodiments of the present invention, the pressure of the first distillation treatment is 0.09 MPaG-0.11 MPaG, for example, it can be a range consisting of 0.09 MPaG, 0.1 MPaG, 0.11, or any two of them; the temperature is 33℃-55℃, for example, it can be a range consisting of 33℃, 35℃, 38℃, 40℃, 45℃, 50℃, 55℃, or any two of them.

[0056] In this invention, the pressure and temperature of the first distillation process are within the above-mentioned range, which can effectively separate trichlorosilane and improve the purity of the final hexachlorosilane.

[0057] In some embodiments of the present invention, the pressure of the second distillation treatment is 0.09 MPaG-0.11 MPaG, for example, it can be a range consisting of 0.09 MPaG, 0.1 MPaG, 0.11, or any two of them; the temperature is 57℃-80℃, for example, it can be a range consisting of 57℃, 60℃, 65℃, 70℃, 75℃, 80℃, or any two of them.

[0058] In this invention, the pressure and temperature of the second distillation process are within the above-mentioned range, which can effectively separate silicon tetrachloride and improve the purity of the final hexachlorosilane.

[0059] In some embodiments of the present invention, the pressure of the adsorption treatment is 0.05 MPa-0.2 MPa, for example, it can be a range of 0.05 MPa, 0.1 MPa, 0.16 MPa, 0.18 MPa, 0.20 MPa, or any two of these; the temperature is 10℃-25℃, for example, it can be a range of 10℃, 15℃, 18℃, 20℃, 25℃, or any two of these.

[0060] In this invention, the pressure and temperature of the adsorption treatment are within the above-mentioned range, which can effectively adsorb metallic impurities in the chlorosilane solution, thereby reducing the impact on subsequent photochemical reactions and improving the purity of the final hexachlorosilane.

[0061] In some embodiments of the present invention, the temperature of the photochemical reaction is 20°C-40°C, for example, it can be a range of 20°C, 25°C, 30°C, 35°C, 40°C or any two of them. The time is 4h-24h, for example, it can be a range of 4h, 5h, 10h, 15h, 20h, 24h or any two of them.

[0062] In this invention, the temperature and time of the photochemical reaction are within the above-mentioned range, which can effectively convert pentachlorosilane into hexachlorosilane and improve the recovery rate of hexachlorosilane. At this temperature, the photocatalyst can better exert its catalytic effect, avoiding catalyst deactivation caused by excessively high temperatures and reducing the occurrence of side reactions.

[0063] In some embodiments of the present invention, the molar ratio of chlorosilane, chlorinating agent and photocatalyst in the third product is (1-10):(1-78):(1-10), for example, it can be a range of 1:10:1, 1:20:1, 1:30:1, 1:40:1, 1:50:1, 1:60:1, 1:70:1, 1:78:1, 1:78:10, 10:78:1, 1:1:1, 1:1:10, 10:1:1 or any two of these.

[0064] The chlorosilanes in the third product of this invention include pentachlorosilane and hexachlorosilane. The molar ratio of chlorosilane, chlorinating agent, and photocatalyst in the third product is within the above-mentioned range, which ensures sufficient chlorination of pentachlorosilane, effectively suppresses side reactions, improves the selectivity and purity of the target product, increases the reaction rate, shortens the reaction time, and improves production efficiency.

[0065] In some embodiments of the present invention, the volume ratio of the chlorinating agent to the third product is (1-2):1, for example, it can be a range of 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1 or any two of these.

[0066] In this invention, the volume ratio of chlorinating agent to the third product is within the above-mentioned range, which can ensure a sufficient supply of chlorinating agent, promote the reaction towards the target product, improve the efficiency and conversion rate of the reaction, suppress the occurrence of side reactions, reduce the generation of by-products, and improve the selectivity and purity of the target product.

[0067] In some embodiments of the present invention, the pressure of the third distillation process is 0.09 MPaG-0.11 MPaG, for example, it can be a range of 0.09 MPaG, 0.095 MPaG, 0.1 MPaG, 0.11 MPaG or any two thereof; the temperature is 40℃-60℃, for example, it can be a range of 40℃, 42℃, 45℃, 48℃, 50℃, 53℃, 55℃, 58℃, 60℃ or any two thereof.

[0068] In this invention, the pressure and temperature of the third distillation process are within the above-mentioned range, which can effectively separate the chlorinating agent and improve the purity of the final hexachlorosilane.

[0069] In some embodiments of the present invention, the pressure of the fourth distillation process is 0.09 MPaG-0.11 MPaG, for example, a range consisting of 0.09 MPaG, 0.095 MPaG, 0.1 MPaG, 0.11 MPaG, or any two thereof; and the temperature is 145℃-160℃, for example, a range consisting of 145℃, 148℃, 150℃, 153℃, 155℃, 158℃, 160℃, or any two thereof.

[0070] In this invention, the pressure and temperature of the fourth distillation process are within the above-mentioned range, which can effectively separate the photocatalyst and hexachlorosilane, thereby improving the purity of the final hexachlorosilane.

[0071] Secondly, the present invention provides a recovery apparatus for performing the hexachlorosilane recovery method described above, such as... Figure 1 As shown, it includes a first distillation unit 1, which is used to perform a first distillation treatment on the chlorosilane solution to be recovered;

[0072] The second distillation unit 2 is used to perform a second distillation process on the first product;

[0073] Adsorption unit 4 is used to adsorb the second product.

[0074] Photochemical reaction unit 6 is used to carry out photochemical reactions on a mixture of the third product, chlorinating agent and photocatalyst;

[0075] The third distillation unit 7 is used to perform a third distillation process on the fourth product;

[0076] The fourth distillation unit 8 is used to perform a fourth distillation process on the fifth product.

[0077] In this invention, the liquid outlet of the first distillation unit 1 is connected to the liquid inlet of the second distillation unit 2, the liquid outlet of the second distillation unit 2 is connected to the liquid inlet of the cooling unit 3, the liquid outlet of the cooling unit 3 is connected to the liquid inlet of the adsorption unit 4, the liquid outlet of the adsorption unit 4 is connected to the liquid inlet of the buffer unit 5, the liquid outlet of the buffer unit 5 is connected to the first liquid inlet of the photochemical reaction unit 6, the liquid outlet of the photochemical reaction unit 6 is connected to the liquid inlet of the third distillation unit 7, the first liquid outlet of the third distillation unit 7 is connected to the liquid inlet of the fourth distillation unit 8, the second liquid outlet of the third distillation unit 7 is connected to the liquid inlet of the second storage unit 10, the liquid outlet of the second storage unit 10 is connected to the second liquid inlet of the photochemical reaction unit 6, the liquid outlet of the fourth distillation unit 8 outputs hexachlorosilane, the solid outlet of the fourth distillation unit 8 is connected to the solid inlet of the first storage unit 9, and the solid outlet of the first storage unit 9 is connected to the solid inlet of the photochemical reaction unit 6.

[0078] Specifically, in this invention, the chlorosilane solution to be recovered undergoes a first distillation process in the first distillation unit 1 to obtain trichlorosilane and a first product; the first product is output through the liquid outlet of the first distillation unit 1 and enters the second distillation unit 2 through the liquid inlet to undergo a second distillation process to obtain silicon tetrachloride and a second product; the second product is output from the liquid outlet of the second distillation unit 2, enters the cooling unit 3 through the liquid inlet of the cooling unit 3 for cooling, and then exits from the liquid outlet of the cooling unit 3, enters the adsorption unit 4 through the liquid inlet of the adsorption unit 4 for adsorption treatment to obtain a third product; the third product is output from the liquid outlet of the adsorption unit 4, enters the buffer unit 5 through the liquid inlet of the buffer unit 5 for buffering, and then exits from the liquid outlet of the buffer unit 5, enters the photochemical reaction unit 6 through the first liquid inlet of the photochemical reaction unit 6, mixes with the photocatalyst and chlorinating agent, and undergoes a photochemical reaction to convert pentachlorosilane into hexachlorosilane to obtain a fourth product; the fourth product exits from the photochemical reaction unit 6... The liquid output from unit 6 enters the third distillation unit 7 through the liquid inlet of the third distillation unit 7 for third distillation treatment, yielding a chlorinating agent and a fifth product. The fifth product exits the third distillation unit 7 through the first liquid outlet, enters the fourth distillation unit 8 through the liquid inlet of the fourth distillation unit 8 for fourth distillation treatment, yielding a photocatalyst and hexachlorosilane. Hexachlorosilane exits the fourth distillation unit 8 through its liquid outlet. The chlorinating agent exits the third distillation unit 7 through the second liquid outlet, enters the second storage unit 10 through the liquid inlet of the second storage unit 10 for storage, and exits from the second storage unit 10, enters the photochemical reaction unit 6 through the second liquid inlet of the photochemical reaction unit 6 to continue participating in the photochemical reaction. The photocatalyst exits the fourth distillation unit 8 through the fourth distillation unit 8 through the first storage unit 9 through the solid inlet of the first storage unit 9 for storage, and exits from the first storage unit 9 through the solid outlet of the first storage unit 9, enters the photochemical reaction unit 6 through the solid inlet of the photochemical reaction unit 6 to continue participating in the photochemical reaction.

[0079] It should be noted that in this invention, the first distillation unit 1, the second distillation unit 2, the third distillation unit 7, and the fourth distillation unit 8 can be distillation columns, the cooling unit 3 can be a cooler, the adsorption unit 4 can be an adsorption column, the buffer unit 5 can be a buffer tank, the photochemical reaction unit 6 can be a photochemical reactor, and the first storage unit 9 and the second storage unit 10 can be storage tanks.

[0080] The hexachlorosilane recovery device provided by this invention can be used to recover hexachlorosilane. Through photochemical reaction, pentachlorosilane can be converted into hexachlorosilane. Furthermore, through multiple distillation and adsorption treatments, not only can the purification difficulty of hexachlorosilane be reduced, but the purity and recovery rate of hexachlorosilane can also be improved.

[0081] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0082] Example 1

[0083] The device in this embodiment is a hexachlorosilane recovery device, such as... Figure 1 As shown, it includes a first distillation unit 1 (distillation column); a second distillation unit 2 (distillation column); a cooling unit 3 (cooler); an adsorption unit 4 (adsorption column); a buffer unit 5 (chlorosilane buffer tank); a photochemical reaction unit 6 (photochemical reactor); a third distillation unit 7 (distillation column); a fourth distillation unit 8 (distillation column); a first storage unit 9 (photocatalyst storage tank); and a second storage unit 10 (chlorinating agent storage tank).

[0084] The liquid outlet of a first distillation unit 1 is connected to the liquid inlet of a second distillation unit 2. The liquid outlet of the second distillation unit 2 is connected to the liquid inlet of a cooling unit 3. The liquid outlet of the cooling unit 3 is connected to the liquid inlet of an adsorption unit 4. The liquid outlet of the adsorption unit 4 is connected to the liquid inlet of a buffer unit 5. The liquid outlet of the buffer unit 5 is connected to the first liquid inlet of a photochemical reaction unit 6. The liquid outlet of the photochemical reaction unit 6 is connected to the liquid inlet of a third distillation unit 7. The first liquid outlet of the third distillation unit 7 is connected to the liquid inlet of a fourth distillation unit 8. The second liquid outlet of the third distillation unit 7 is connected to the liquid inlet of a second storage unit 10. The liquid outlet of the second storage unit 10 is connected to the second liquid inlet of the photochemical reaction unit 6. The liquid outlet of the fourth distillation unit 8 outputs hexachlorosilane. The solid outlet of the fourth distillation unit 8 is connected to the solid inlet of a first storage unit 9. The solid outlet of the first storage unit 9 is connected to the solid inlet of the photochemical reaction unit 6.

[0085] Specifically, the chlorosilane solution to be recovered (obtained from the chlorosilane solution obtained after the reduction reaction of trichlorosilane and hydrogen in polysilicon production, and the removal of hydrogen from the tail gas generated by the reduction furnace through condensation) undergoes a first distillation process in the first distillation unit 1. The pressure of the first distillation process is 0.1 MPaG, and the temperature is 45°C, yielding trichlorosilane and a first product. The first product is output through the liquid outlet of the first distillation unit 1 and enters the second distillation unit 2 through the liquid inlet for a second distillation process. The pressure of the second distillation process is 0.1 MPaG, and the temperature is 65°C, yielding silicon tetrachloride and a second product. The second product is output from the liquid outlet of the second distillation unit 2 and enters the second distillation unit 3 through the liquid inlet. The product is cooled in cooling unit 3, then output from the liquid outlet of cooling unit 3, and enters adsorption unit 4 through the liquid inlet of adsorption unit 4 for adsorption treatment. The adsorption treatment pressure is 0.14 MPa and the temperature is 15℃, yielding a third product. The third product is output from the liquid outlet of adsorption unit 4, enters buffer unit 5 through the liquid inlet of buffer unit 5 for buffering, and then outputs through the liquid outlet of buffer unit 5. In photochemical reaction unit 6, it is mixed with the photocatalyst neutral eosin Y and the chlorinating agent dichloromethane to undergo a photochemical reaction, converting tetrachlorosilane into hexachlorosilane. The photochemical reaction temperature is 35℃ and the time is 15 hours. The third product contains chlorosilane... The molar ratio of chlorinating agent dichloromethane to photocatalyst neutral eosin Y is 10:78:1, denoted as ratio 1. The volume ratio of chlorinating agent dichloromethane to the third product is 1.5:1, denoted as ratio 2, yielding the fourth product. The fourth product exits from the liquid outlet of photochemical reaction unit 6 and enters the third distillation unit 7 through the liquid inlet for third distillation treatment. The pressure of the third distillation treatment is 0.1 MPaG, and the temperature is 50°C, yielding chlorinating agent dichloromethane and the fifth product. The fifth product exits from the first liquid outlet of the third distillation unit 7 and enters the fourth distillation unit 8 through the liquid inlet for fourth distillation treatment. The pressure of the fourth distillation treatment is 0.1 MPaG, and the temperature is 150°C. At ℃, neutral eosin Y photocatalyst and hexachlorosilane are obtained; hexachlorosilane is output from the liquid outlet of the fourth distillation unit 8; dichloromethane chlorinating agent is output from the second liquid outlet of the third distillation unit 7, enters the second storage unit 10 through the liquid inlet of the second storage unit 10 for storage, and is output from the second storage unit 10, enters the photochemical reaction unit 6 through the second liquid inlet of the photochemical reaction unit 6 to continue participating in the photochemical reaction; neutral eosin Y photocatalyst is output from the solid outlet of the fourth distillation unit 8, enters the first storage unit 9 through the solid inlet of the first storage unit 9 for storage, and is output from the solid outlet of the first storage unit 9, enters the photochemical reaction unit 6 through the solid inlet of the photochemical reaction unit 6 to continue participating in the photochemical reaction.

[0086] Example 2-17

[0087] The recovery apparatus and method for hexachlorosilane in Examples 2-17 are basically the same as those in Example 1, except that one or more steps of the recovery method are changed. Specific parameters are shown in Tables 2 and 3.

[0088] Comparative Example 1

[0089] The recovery apparatus and method for hexachlorosilane in Comparative Example 1 and Example 1 are basically the same. The difference is that the recovery apparatus for hexachlorosilane in Comparative Example 1 does not include a photochemical reaction unit. The chlorosilane solution to be recovered directly enters the third distillation unit after passing through the first distillation unit, the second distillation unit and the adsorption unit to remove trichlorosilane, silicon tetrachloride and B and P impurities, so that hexachlorosilane can be recovered.

[0090] Table 1: Composition of the chlorosilane solution to be recovered in the experiment

[0091]

[0092] The content of B and P impurities is at the ppb level; if the content is too low, it will not be reflected in the table.

[0093] Table 2

[0094]

[0095] Table 3

[0096]

[0097] As can be seen from Tables 2 and 3, the method for recovering hexachlorosilane provided by the present invention can convert pentachlorosilane into hexachlorosilane through photochemical reaction. Furthermore, through multiple distillation and adsorption treatments, it can not only reduce the purification difficulty of hexachlorosilane, but also improve the purity and recovery rate of hexachlorosilane.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recovering hexachlorosilane, characterized in that, Includes the following steps: 1) The chlorosilane solution to be recovered is subjected to a first distillation treatment to obtain the first product; 2) The first product is subjected to a second distillation process to obtain a second product; 3) The second product is subjected to adsorption treatment to obtain the third product; 4) A photochemical reaction is carried out on the mixture including the third product, the chlorinating agent and the photocatalyst to obtain the fourth product; 5) The fourth product is subjected to a third distillation process to obtain the fifth product; 6) The fifth product is subjected to a fourth distillation process to obtain the hexachlorosilane.

2. The method for recovering hexachlorosilane according to claim 1, characterized in that, The pressure of the first distillation process is 0.09 MPaG-0.11 MPaG, and the temperature is 33℃-55℃.

3. The method for recovering hexachlorosilane according to claim 1 or 2, characterized in that, The pressure of the second distillation process is 0.09 MPaG-0.11 MPaG, and the temperature is 57℃-80℃.

4. The method for recovering hexachlorosilane according to any one of claims 1-3, characterized in that, The adsorption treatment is performed at a pressure of 0.05 MPa-0.2 MPa and a temperature of 10℃-25℃.

5. The method for recovering hexachlorosilane according to any one of claims 1-4, characterized in that, The photochemical reaction is carried out at a temperature of 20℃-40℃ for a time of 4h-24h.

6. The method for recovering hexachlorosilane according to any one of claims 1-5, characterized in that, The molar ratio of chlorosilane, chlorinating agent and photocatalyst in the third product is (1-10):(1-78):(1-10).

7. The method for recovering hexachlorosilane according to any one of claims 1-6, characterized in that, The volume ratio of the chlorinating agent to the third product is (1-2):

1.

8. The method for recovering hexachlorosilane according to any one of claims 1-7, characterized in that, The pressure of the third distillation process is 0.09 MPaG-0.11 MPaG, and the temperature is 40℃-60℃.

9. The method for recovering hexachlorosilane according to any one of claims 1-8, characterized in that, The pressure of the fourth distillation process is 0.09 MPaG-0.11 MPaG, and the temperature is 145℃-160℃.

10. A recovery apparatus for performing the recovery method of hexachlorosilane according to any one of claims 1-9, characterized in that, It includes a first distillation unit for performing a first distillation treatment on the chlorosilane solution to be recovered; The second distillation unit is used to perform a second distillation process on the first product; An adsorption unit is used to adsorb the second product. A photochemical reaction unit is used to perform a photochemical reaction on the mixture of the third product, chlorinating agent, and photocatalyst. The third distillation unit is used to perform a third distillation process on the fourth product; The fourth distillation unit is used to perform a fourth distillation process on the fifth product.

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