Preparation method of high-purity diiodosilane

Abstract

The invention discloses a preparation method of high-purity diiodosilane, which comprises the following steps: firstly, preparing a p-phenylsilane solution from phenyl trichlorosilane and sodium hydride as raw materials, rectifying and purifying the p-phenylsilane solution, directly reacting the p-phenylsilane solution with iodine to generate diiodosilane, and reacting phenylsilane with iodine to directly generate diiodosilane; in the process of preparing diiodosilane from phenylsilane, conditions are mild, the reaction process is controllable, the reaction time is shortened by controlling the temperature in the synthesis process and increasing the pressure of a reaction system, hydrogen iodide overflow is reduced, sodium hydride is adopted as a reducing agent in the reaction process, and the yield of diiodosilane is increased. The solid waste can be recycled, the cost can be effectively reduced, and industrialization of diiodosilane is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of diiodosilane preparation methods, and in particular to a process for preparing diiodosilane by iodination of an organic silicon source. Background Art

[0002] Diiodosilane (H2SiI2), an important silicon source for chemical vapor deposition (CVD), can be deposited onto a wide range of substrates. Currently, the synthesis and purification of diiodosilane are still monopolized by developed countries. While research has been conducted domestically, the conditions for large-scale production are still lacking.

[0003] The main methods for preparing diiodosilane include: halogen exchange; preparation by direct reaction of silicon and hydrogen iodide or silicon with hydrogen and iodine; organosilicon source iodination (phenylsilane iodination) and silyl iodination (monosilane iodination). The organosilicon source iodination method has attracted widespread attention due to its less hazardous raw materials, relatively mild reaction conditions, and ease of implementation under laboratory conditions. However, its raw materials, phenylsilane and elemental iodine, react, resulting in high reaction costs, a slow reaction process, and a long reaction time. This is not conducive to its large-scale production. To reduce costs, a phenylsilane self-made method is often used. Chinese patent CN113548669A discloses a preparation apparatus and method for high-purity electronic-grade diiodosilane, relating to the field of diiodosilane purification technology. The above-mentioned preparation apparatus includes a first reactor, a second reactor, and a vacuum distillation purifier. The first reactor is divided into a fluidized bed section, an oil phase section, and a hydrogen iodide section. The lower ends of the oil phase section and the hydrogen iodide section are connected to the second reactor. The preparation method of high-purity electronic-grade diiodosilane includes the following steps: nitrogen replacement; initiating a reaction using phenylsilane, an oxygen-containing compound catalyst, and an aromatic organic solvent to generate a phenylsilane layer, a monoiodophenylsilane layer, and a hydrogen iodide layer; continuously introducing phenylsilane, adjusting the discharge port and the flow rate of phenylsilane, and controlling the interface between the monoiodophenylsilane layer and the hydrogen iodide layer to be at the interface between the oil phase segment and the hydrogen iodide segment; and performing vacuum distillation. The preparation device and preparation method of the present invention reduce side reactions by isolating phenylsilane from contact with HI, thereby improving product purity and feedstock conversion. However, the reaction preparation process produces a large number of byproducts, and the cost of treating the three wastes is high.

[0004] Chinese patent CN110606491B discloses a method for preparing high-purity diiodosilane. Under inert gas protection, lithium aluminum tetrahydride and phenyldichlorosilane are reacted with an ether solvent to produce a phenylsilane mixture. The phenylsilane mixture is heated to evaporate the phenylsilane, which is then collected. The collected phenylsilane is added dropwise to powdered elemental iodine under stirring at a temperature of -80 to 30°C, and an oxygen-containing organic compound is added as a catalyst to produce the diiodosilane mixture. The temperature of the diiodosilane mixture is then raised to distill the crude diiodosilane. This method differs from the silane iodination method disclosed in this application. This reaction produces a larger number of byproducts and results in higher waste treatment costs. Summary of the Invention

[0005] The present invention aims to provide a method for preparing high-purity diiodosilane, wherein phenylsilane is prepared in-house and the waste generated by the reaction is single and convenient for post-processing. The temperature and pressure during the synthesis of diiodosilane are controlled to improve the reaction yield, and the purity of diiodosilane can be improved by distillation purification.

[0006] The technical solution adopted in the present invention is:

[0007] A method for preparing high-purity diiodosilane, comprising the following steps:

[0008] Step 1: mixing a reducing agent and solvent A to form a mixed solution;

[0009] Step 2: After the temperature of the mixed solution of the reducing agent and solvent A stabilizes, phenyltrichlorosilane is added dropwise to the mixed solution of the reducing agent and solvent A. After the addition is complete, the reaction system is maintained for 0.5-1 hour, and then the temperature is raised to react. The reaction product is filtered and purified by distillation to obtain purified phenylsilane;

[0010] Step 3: After uniformly mixing the iodine element and the solvent B, the purified phenylsilane is added dropwise to the solution of the iodine element and the solvent B, and the temperature and pressure are controlled to react to obtain a diiodosilane product;

[0011] Step 4: distill the diiodosilane product.

[0012] Preferably, the reducing agent in step 1 is sodium hydride;

[0013] Solvent A is one or a mixture of methyl tert-butyl ether, tetrahydrofuran, and diethylene glycol dimethyl ether;

[0014] Preferably, the temperature of the mixed solution in step 1 is -20 to 10°C.

[0015] Preferably, after forming the mixed liquid in step 1, a gas replacement step is further included, wherein the gas replacement step is to use nitrogen or inert gas to replace the gas in the reaction system 2-3 times.

[0016] Preferably, the temperature of the temperature-raising reaction in step 2 is 20-40° C., and the reaction time is 6-12 h;

[0017] In step 2, the distillation pressure is 50 KPa and the distillation temperature is 25-50°C.

[0018] Preferably, the molar ratio of the reducing agent to phenyltrichlorosilane in step 2 is 3:1 to 5:1.

[0019] Preferably, in step 2, the volume ratio of phenyltrichlorosilane to solvent A is 1:3 to 1:5.

[0020] Preferably, the temperature of mixing the iodine element and the solvent B in step 3 is -78 to -50°C;

[0021] The molar ratio of phenylsilane to iodine is 1:2 to 1:5;

[0022] The volume ratio of phenylsilane to solvent B is 1:2 to 1:5.

[0023] Preferably, the solvent B in step 3 is one or more of toluene, xylene, trimethylbenzene, dichloromethane, n-hexane, chloroform, etc.

[0024] Preferably, after the purified phenylsilane is added dropwise in step 3, the temperature is maintained at -78 to -50°C for 8 to 12 hours, the reaction system is heated to 30 to 45°C, and a nitrogen pressure of 0.01 to 0.4 MPa is applied for 48 to 72 hours.

[0025] During the reaction, the fluctuation is controlled to be no more than ±2° C., and a pressure of 0.01-0.4 MPa, preferably 0.05-0.4 MPa, is applied to the experimental system to prevent the overflow of the intermediate product hydrogen iodide during the experiment, thereby increasing the reaction yield and shortening the reaction time.

[0026] Preferably, the distillation treatment in step 4 is performed at a pressure of 20-40 kPa and a temperature of 30-60°C.

[0027] Reaction equation of the present invention is:

[0028] PhSiH3+I2→PhSiH2I+HI

[0029] PhSiH3+HI→SiH3I+PhH

[0030] PhSiH2I+HI→SiH2I2+PhH,

[0031] SiH3I+I2→SiH2I2+HI.

[0032] The beneficial effects of the present invention are:

[0033] The present invention provides a method for preparing high-purity diiodosilane. The invention lies in that the raw materials are prepared by phenyltrichlorosilane and sodium hydride, and after the phenylsilane solution is distilled and purified, it is directly used to react with iodine to generate diiodosilane. Phenylsilane reacts with iodine to directly generate diiodosilane. The reaction conditions are mild and the reaction process is controllable. However, since the key intermediate product hydrogen iodide overflows during the reaction process, the reaction process is relatively slow and time-consuming, which is not conducive to industrialization. The invention controls the temperature during the synthesis process and increases the pressure of the reaction system, thereby reducing the overflow of hydrogen iodide and shortening the reaction time. The reaction is moved in a direction that is conducive to the generation of diiodosilane, thereby improving and optimizing the yield of diiodosilane, and the obtained diiodosilane is prepared into high-purity diiodosilane by distillation and purification. Phenylsilane reduction typically involves the reaction of phenyltrichlorosilane with lithium aluminum tetrahydride. This process produces a mixture of lithium chloride and aluminum chloride, which prevents waste reuse. Furthermore, lithium aluminum tetrahydride is expensive, making industrialization costly. Using sodium hydride as the reducing agent in the reaction allows for solid waste recycling and effectively reduces costs, thus facilitating the industrialization of diiodosilane.

[0034] The method of the present invention starts with the preparation of phenylsilane. First, phenyltrichlorosilane and sodium hydride are used for self-production. Usually, phenylsilane reduction adopts phenyltrichlorosilane and lithium aluminum hydride to react. The reaction process produces solid wastes as a mixture of lithium chloride and aluminum chloride, which cannot be reused. The price of lithium aluminum hydride is high, which is high for industrialization. Using sodium hydride as a reducing agent in the reaction process can realize solid waste recycling and effectively reduce costs. After the phenylsilane solution is subjected to rectification and purification, it is directly used to react with iodine to generate diiodosilane, which can effectively reduce the cost of preparing diiodosilane. By controlling the temperature and increasing the pressure of the reaction system during the synthesis process, the reaction is moved in a direction that is conducive to the generation of diiodosilane, which can effectively shorten the reaction time and improve the yield of optimized diiodosilane. The obtained diiodosilane is subjected to two rectification and purification steps to prepare high-purity diiodosilane.

[0035] The mainstream method for preparing diiodosilane in the industry is the direct reaction of phenylsilane with elemental iodine. This process requires the high cost of the raw material phenylsilane, which increases the cost of diiodosilane preparation, limiting its large-scale production and making it difficult to meet actual market demand. However, the production of phenylsilane in-house can reduce the process cost and make this method more suitable for industrial application. Currently, most phenylsilane production methods use lithium aluminum tetrahydride reduction, but lithium aluminum tetrahydride is expensive and produces three wastes that cannot be recycled. Using sodium hydride as a reducing agent is less expensive and the three waste products can be recycled. The process of preparing diiodosilane from phenylsilane has many reaction processes and the experimental intermediate hydrogen iodide has a low boiling point, which can overflow from the system during the experiment, resulting in a long reaction time, which is not conducive to industrial application. The present invention, through process control of the diiodosilane synthesis conditions, can promote the reaction towards the production of diiodosilane. This can effectively shorten the reaction time and increase the reaction yield, making it more suitable for industrial application.

[0036] The present invention also has the following advantages:

[0037] (1) The diiodosilane yield obtained by the method for preparing high-purity diiodosilane described in the present invention is relatively high and can reach more than 80%.

[0038] (2) The diiodosilane prepared by the present invention has a high purity, and the product after distillation contains a low content of by-products. (3) The reaction temperature of the preparation process of the present invention is easy to control, which reduces the difficulty of process operation, and the reaction time can be shortened by applying external pressure.

[0039] (4) The preparation process is reasonable, easy to operate, and suitable for large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the H NMR spectrum of the preparation method of high-purity diiodosilane, the final product of Example 1 of the present invention. DETAILED DESCRIPTION

[0041] The present invention provides a method for preparing high-purity diiodosilane. First, solvent A and sodium hydride are added to a reactor 1. The reactor is then cooled to -20 to 10°C. The reaction system is replaced with nitrogen three times, and then phenyltrichlorosilane is slowly added to the reactor. After the phenyltrichlorosilane is added dropwise, the reaction system is maintained for 0.5 to 1 hour. The reaction system is then heated to 20 to 40°C. After reacting for 6 to 12 hours, the solid in the reaction system is filtered and the liquid is purified by distillation to obtain pure phenylsilane. The resulting solid waste is treated and collected. The chloride salt is later reused.

[0042] Add iodine and solvent to the reactor, purge the reactor with nitrogen, lower the reactor temperature to -60°C, and then dropwise add pure phenylsilane to the reaction system. After the addition of phenylsilane is complete, maintain the temperature at low temperature for 8-12 hours, then raise the temperature to 30-45°C and apply a nitrogen pressure of 0.01-0.4 MPa to the reaction system for 48-72 hours. Purify the reaction liquid by distillation.

[0043] Example 1

[0044] First, add 400ml of methyl tert-butyl ether and 75g of sodium hydride to the reactor, then cool the reactor to -20°C. After nitrogen is purged three times, slowly add 211g of phenyltrichlorosilane to the reactor. After the addition of phenyltrichlorosilane is complete, maintain the reaction system for 0.5h, then raise the temperature to 30°C. After reacting for 6h, filter the solids in the reaction system and purify the liquid by distillation to obtain pure phenylsilane. The distillation pressure is 50kPa and the distillation temperature is 50°C.

[0045] 235g of iodine and 300ml of toluene solvent were added to the reactor. After the reactor was purged with nitrogen, the temperature of the reactor was lowered to -60°C, and 100g of pure phenylsilane was added dropwise to the reaction system. After the addition of phenylsilane was completed, the temperature was kept at -60°C for 10 hours, and the reaction system was heated to 30°C. A nitrogen pressure of 0.2MPa was applied to the reaction system and maintained for 72 hours. The product yield was 85%. The reaction solution was subjected to a rectification and purification experiment. Vacuum distillation was carried out at 30°C and 35kPa (absolute pressure). Figure 1 It can be seen that the purity of the final product is 99%.

[0046] Example 2

[0047] First, add 200ml of methyl tert-butyl ether and 75g of sodium hydride to the reactor, then cool the reactor to -10°C. After nitrogen is purged three times, slowly add 211g of phenyltrichlorosilane to the reactor. After the addition of phenyltrichlorosilane is complete, maintain the reaction system for 0.5h, then raise the temperature to 30°C. After reacting for 6h, filter the solids in the reaction system and purify the liquid by distillation to obtain pure phenylsilane. The distillation pressure is 50kPa and the distillation temperature is 25°C.

[0048] 300g of elemental iodine and 300ml of chloroform solvent were added to a reactor. After the reactor was purged with nitrogen, the reactor temperature was lowered to -60°C. 100g of pure phenylsilane was then added dropwise to the reaction system. After the addition of phenylsilane was complete, the reaction system was kept at -60°C for 10 hours, then the temperature was raised to 30°C. A nitrogen pressure of 0.1MPa was applied to the reaction system for 60 hours. The product yield was 78%. The reaction solution was subjected to a rectification and purification experiment. Vacuum distillation was performed at 40°C and 30kPa (absolute pressure), and the final product purity was 98%.

[0049] Example 3

[0050] First, add 200ml of tetrahydrofuran and 75g of sodium hydride to the reactor. Then, cool the reactor to -10°C and replace the reaction system with nitrogen three times. Then, slowly add 211g of phenyltrichlorosilane to the reactor. After the addition of phenyltrichlorosilane is complete, maintain the reaction system for 0.5h. Then, heat the reaction system to 30°C. After reacting for 6h, filter the solids in the reaction system and purify the liquid by distillation to obtain pure phenylsilane. The distillation pressure is 50kPa and the distillation temperature is 35°C.

[0051] 470g of elemental iodine and 300ml of chloroform solvent were added to a reactor. After the reactor was purged with nitrogen, the reactor temperature was lowered to -60°C. 100g of pure phenylsilane was then added dropwise to the reaction system. After the addition of phenylsilane was complete, the reaction system was kept at -60°C for 10 hours, then the temperature was raised to 30°C. A nitrogen pressure of 0.1MPa was applied to the reaction system for 60 hours. The product yield was 72%. The reaction solution was subjected to a rectification and purification experiment. Vacuum distillation was performed at 50°C and 25kPa (absolute pressure), and the final product purity was 96%.

[0052] Comparative Example 1

[0053] This comparative example is identical to Example 1, differing in that nitrogen was not used to replace the air in the system during the initial experiments. The final yield of diiodosilane was approximately 60%. This significantly reduced yield and the final product purity were relatively low.

[0054] Comparative Example 2

[0055] This comparative example is the same as Example 1, except that: during the preparation of diiodosilane, it was found that different iodinated silanes and hydrogen iodide were generated during the experimental process. When no pressure was applied to the reaction system, the diiodosilane generation time was 5 days after heating at room temperature, which was too long and not conducive to industrial production. The reactor system was pressurized to prevent the intermediate hydrogen iodide from overflowing from the reaction system. The reaction system was heated to 30°C, and the final reaction time of diiodosilane was approximately 60 hours, shortening the reaction time and facilitating industrial production.

[0056] Comparative Example 3

[0057] This comparative example is identical to Example 1, except that 235 g of elemental iodine and 300 ml of toluene solvent were added to a reactor. The reactor was purged with nitrogen and then cooled to 0°C. Then, 100 g of pure phenylsilane was added dropwise to the reaction system. After the addition of phenylsilane was complete, the temperature was maintained at 0°C for 60 hours. The final yield of diiodosilane was only 5%, indicating that diiodosilane formation is only favorable when the temperature is raised to a certain level.

[0058] The present invention is described in more detail above through some non-limiting specific embodiments. However, the present invention is not limited to the above embodiments, and the embodiments and descriptions are only for illustrating the principles of the present invention. That is to say, the above descriptions are only some preferred embodiments of the present invention, and cannot be used to limit the scope of rights of the present invention. For ordinary technicians in this technical field, various changes, improvements and modifications can be made to the present invention without departing from the spirit, principle and scope of the present invention. The additional features of these improvements may exist alone or in any combination, and these changes, improvements and modifications should also be regarded as within the scope of the invention claimed for protection.

Claims

1. A method for preparing high-purity diiodosilane, characterized in that: The method comprises the following steps, Step 1: mixing a reducing agent and solvent A to form a mixed solution; Step 2: After the temperature of the mixed solution of the reducing agent and solvent A stabilizes, phenyltrichlorosilane is added dropwise to the mixed solution of the reducing agent and solvent A. After the addition is complete, the reaction system is maintained for 0.5-1 hour, and then the temperature is raised to react. The reaction product is filtered and purified by distillation to obtain purified phenylsilane; Step 3: After uniformly mixing the iodine element and the solvent B, the purified phenylsilane is added dropwise to the solution of the iodine element and the solvent B, and the temperature and pressure are controlled to react to obtain a diiodosilane product; Step 4: distill the diiodosilane product.

2. A method for preparing high-purity diiodosilane according to claim 1, characterized in that: The reducing agent in step 1 is sodium hydride; Solvent A is one or a mixture of methyl tert-butyl ether, tetrahydrofuran, and diethylene glycol dimethyl ether.

3. A method for preparing high-purity diiodosilane according to claim 1, characterized in that: The temperature of the mixed solution in step 1 is -20 to 10°C; After the mixed liquid is formed in step 1, a gas replacement step is also included, wherein the gas replacement step is to use nitrogen or inert gas to replace the gas in the reaction system 2-3 times.

4. The method for preparing high-purity diiodosilane according to claim 1, wherein: The temperature of the temperature-raising reaction in step 2 is 20-40° C., and the reaction time is 6-12 h; In step 2, the distillation pressure is 50 KPa and the distillation temperature is 25-50°C.

5. The method for preparing high-purity diiodosilane according to claim 1, wherein: In step 2, the molar ratio of reducing agent to phenyltrichlorosilane is 3:1 to 5:

1.

6. The method for preparing high-purity diiodosilane according to claim 1, wherein: In step 2, the volume ratio of phenyltrichlorosilane to solvent A is 1:3 to 1:

5.

7. The method for preparing high-purity diiodosilane according to claim 1, wherein: The temperature of mixing the iodine element and the solvent B in step 3 is -78 to -50°C; The molar ratio of phenylsilane to iodine is 1:2 to 1:5; The volume ratio of phenylsilane to solvent B is 1:2 to 1:

5.

8. The method for preparing high-purity diiodosilane according to claim 1, wherein: The solvent B described in step 3 is one or more of toluene, xylene, trimethylbenzene, dichloromethane, n-hexane and chloroform.

9. The method for preparing high-purity diiodosilane according to claim 1, wherein: After the purified phenylsilane is added dropwise in step 3, the temperature is maintained at -78 to -50°C for 8 to 12 hours, the reaction system is heated to 30 to 45°C, and a nitrogen pressure of 0.01 to 0.4 MPa is applied and maintained for 48 to 72 hours.

10. The method for preparing high-purity diiodosilane according to claim 1, wherein: The distillation treatment in step 4 is performed at a pressure of 20-40 kPa and a temperature of 30-60°C.

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