Synthesis and purification process of trimethylsilane

Abstract

The invention relates to the technical field of trimethylsilane production, and discloses a synthesis and purification process of trimethylsilane, which comprises the following steps: dehydrating ethylene glycol dimethyl ether, mixing with sodium aluminum tetrahydride to obtain a mixed solution, and then adding trimethylchlorosilane for reaction; reacting to obtain a gas phase and a liquid phase; and collecting and purifying the gas phase to obtain the trimethylsilane. The trimethylsilane is obtained by taking trimethylchlorosilane and sodium aluminum tetrahydride as raw materials and ethylene glycol dimethyl ester as a solvent. The solvent is dewatered, the reaction by-product salt is separated, and the solvent and the raw materials are recycled. Therefore, efficient and low-cost trimethylsilane production is realized.

Description

Technical Field

[0001] The invention relates to the technical field of trimethylsilane production, and in particular to a synthesis and purification process of trimethylsilane. Background Art

[0002] Trimethylsilane ((CH3)3SiH) can be used as an intermediate in the production of organosilicon polymers and organic synthesis reactions. It can also be used as a capping agent, desiccant, dehydrating agent, high-temperature adhesive and raw material for resins of polymer compounds. In the hydrophobic treatment of glass fiber surfaces and the surface treatment of plastic laminates, the addition of only 0.5% to 4% of the silane coupling agent in the product can greatly improve the thermal deformation temperature of the product, and improve the mechanical properties, electrical properties and processing properties of the product. In the semiconductor field, it is widely used in interlayer insulation films as a film-forming raw material. In addition, it is often used in the synthesis of cephalosporin I and cephalosporin V in pharmaceutical production. Therefore, it is an important auxiliary agent in aviation, aerospace, military, medicine and health, and civil use, and has great market potential, but the high-purity trimethylsilane currently used in China still mainly relies on imports.

[0003] The existing laboratory-level method for preparing trimethylsilane is to use dimethyl monochlorosilane and methyl chloride as raw materials, and then react the Grignard reagent generated by the Grignard reaction with dimethyl monochloromethane to obtain trimethylsilane, and then obtain electronic-grade trimethylsilane by pressure distillation, with a total yield of 68.2%. The advantages of this method are that the Grignard reagent has good selectivity, the impurity content of the trimethylsilane generated by the reaction is low, and it is easy to purify to electronic grade. (Xie Xianqing, Wu Liangfa. Improvement of the synthesis and purification process of electronic-grade trimethylsilane [J]. Journal of Jiangxi Normal University (Natural Science Edition), 2019, 43(02): 172-176.)

[0004] The Chinese utility model patent "An electronic grade trimethylsilane preparation device" with publication number CN218945032U uses trimethylchlorosilane and hydrogen catalytic hydrogenation to prepare trimethylsilane, including an H2 adsorption tower, a compressor, a methylchlorosilane adsorption tower, a reactor, a condenser, a cryogenic device, a collecting tank, a light removal tower, and a heavy removal tower. The advantages of this method are that it essentially eliminates the generation of silane series impurities such as silane, methyltrichlorosilane, dimethyldichlorosilane, dimethylsilane, and trimethylsilane, and does not use solvents and hydrogenating agents, thereby avoiding the generation of salt solutions and solvent recovery during the hydrogenation process.

[0005] The Chinese invention patent "Method and reaction system for continuous production of high-purity trimethylsilane" with publication number CN115028656A uses trimethylchlorosilane as a raw material and an active metal hydride as a reducing agent to produce a reduction reaction in a specific solvent to generate trimethylsilane and a variety of silane impurity gases, which are then purified by combining multi-stage distillation with adsorption. This method can achieve continuous, low-cost mass production of electronic-grade trimethylsilane with an organic purity exceeding 4N and an inorganic purity exceeding 6N.

[0006] The Chinese invention patent with publication number CN116987110A, "A high-performance organic silicon compound refining process and system", uses tetrahydrofuran as a solvent and lithium aluminum hydride as a reducing agent to reduce trimethylchlorosilane to generate trimethylsilane. The tetrahydrofuran is dehydrated with anhydrous calcium chloride or anhydrous calcium sulfate, and the solvent tetrahydrofuran is recycled.

[0007] The Grignard reaction technology involves the storage and reaction of flammable and explosive materials such as methyl chloride, methyl iodide and magnesium powder, and the Grignard reaction is difficult to achieve stable control after scale-up; at the same time, the core raw material of this method, dimethylchlorosilane, is a very trace by-product produced in the production process of silicone intermediates. Its source is unstable, difficult to purchase in large quantities, and expensive.

[0008] The hydrogenation technology mentioned in patent CN218945032U has hydrogen chloride as a by-product, which is highly corrosive and has high requirements on the material of the equipment. It has high initial costs and a large amount of tail gas, which can easily cause environmental pollution.

[0009] Patent CN115028656A does not separate the by-product salt, and the solvent is not recovered. In addition, since the reducing agent and the solvent are not optimized, there are many impurities after the reaction, and the product purification process is too long.

[0010] Patent CN116987110A directly reuses the solvent, but the recycled solvent may contain unreacted raw materials, which will cause a rapid reaction during the mixing process of the solvent and the reducing agent, thereby causing unexpected risks. In addition, the cost of lithium aluminum hydride used in the patent is high.

[0011] Therefore, there is an urgent need for a synthesis and purification process of trimethylsilane to solve the above technical problems. Summary of the invention

[0012] The present invention aims to obtain trimethylsilane by using trimethylchlorosilane and sodium aluminum tetrahydride as raw materials and ethylene glycol dimethyl ester as solvent, and remove water from the solvent, separate the reaction byproduct salt, and recycle the solvent and raw materials, so as to realize efficient and low-cost production of trimethylsilane.

[0013] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0014] A synthesis and purification process of trimethylsilane comprises the following steps:

[0015] Ethylene glycol dimethyl ether is dehydrated and mixed with sodium aluminum tetrahydride to obtain a mixed solution, and then trimethylsilyl chloride is added to react; after the reaction, a gas phase and a liquid phase are obtained; the gas phase is collected and purified to obtain trimethylsilane.

[0016] Specifically, ethylene glycol dimethyl ether is adsorbed and dehydrated by passing through a dehydrator equipped with molecular sieves.

[0017] Industrial-grade ethylene glycol dimethyl ether often contains a small amount of water, and the presence of water will react with the reducing agent (sodium aluminum tetrahydride) to directly generate hydrogen, which poses a safety risk. It will also react with the raw material (trimethylchlorosilane) to generate trimethylsilanol, introducing impurities and causing waste of raw materials. Therefore, the solvent ethylene glycol dimethyl ether needs to be dried.

[0018] Preferably, the mass ratio of ethylene glycol dimethyl ether to sodium aluminum tetrahydride is (4-10):1.

[0019] Preferably, the molar ratio of sodium aluminum tetrahydride to trimethylsilyl chloride is (1.05-1.2):4.

[0020] Preferably, the reaction temperature of trimethylchlorosilane and the mixed solution is 0-40° C., and the reaction pressure is 0.1-0.5 MPa.

[0021] Specifically, the mixed solution is transferred to a reaction kettle to react with trimethylchlorosilane, and stirring is performed during the reaction.

[0022] Preferably, the trimethylsilyl chloride is added dropwise for 10 hours.

[0023] Preferably, the gas phase is collected by condensation at -15°C and then enters a distillation tower for purification; the operating temperature of the distillation tower is -15 to 60°C and the pressure is 0.1 to 0.5 MPa.

[0024] Preferably, the gas phase is condensed and then enters a distillation tower, the collected fraction is trimethylsilane, and the bottoms in the distillation tower are high-boiling impurities.

[0025] Specifically, after the gas phase is condensed, it enters a distillation tower for purification, and the number of theoretical plates of distillation is 15 to 25.

[0026] Preferably, the liquid phase is filtered to obtain a filtrate and a solid material; the solid material is dried and recovered as a by-product.

[0027] Specifically, the solid material is a mixed salt of sodium chloride and aluminum chloride, the drying temperature of the solid material is 130° C., and the drying pressure is normal pressure.

[0028] Preferably, the filtrate is distilled using a distillation tower; during the distillation process: the operating temperature is 20-130° C., and the pressure is 0.1-0.3 MPa.

[0029] Preferably, the filtrate enters a distillation tower, and the front fraction obtained by distillation is unreacted trimethylchlorosilane, and the rear fraction is ethylene glycol dimethyl ether.

[0030] Specifically, the filtrate is distilled using a distillation tower, and the number of theoretical plates of distillation is 15 to 25.

[0031] The filtrate will contain residual trimethylchlorosilane and high-boiling impurities from the reaction. If it is directly reused, it will easily react rapidly with the reducing agent during the mixing process to form trimethylsilane. Increasing the pressure and temperature will cause safety risks and product waste. Direct reuse will cause high-boiling impurities to continue to accumulate, affecting the ratio and reaction of the solvent and solute. Therefore, the filtrate is distilled.

[0032] Specifically, Figure 1 As shown, a synthesis and purification process of trimethylsilane comprises the following steps:

[0033] S1, passing the newly purchased solvent ethylene glycol dimethyl ether through a dehydrator equipped with a molecular sieve to adsorb and remove moisture.

[0034] S2, mixing the ethylene glycol dimethyl ether after dehydration with sodium aluminum tetrahydride to form a mixed solution, and transferring the mixed solution to a reactor, starting stirring, and controlling the temperature of the reactor to 0-40° C., the pressure to 0.1-0.5 MPa, and the mass ratio of ethylene glycol dimethyl ether to sodium aluminum tetrahydride to be 4:1-10:1;

[0035] S3, continuously dripping the raw material trimethylsilyl chloride into the reactor, and controlling the reaction conditions to be stable, the dripping time is 10 hours, after the dripping is completed, the reaction is kept warm until no liquid flows out of the gas phase condenser, and a gas phase and a liquid phase are obtained; the molar ratio of sodium aluminum tetrahydride to trimethylsilyl chloride is 1.05:4 to 1.2:4; the liquid phase is the residual liquid in the reactor;

[0036] The reactor used in step S3 is equipped with a gas phase condenser, which is installed behind the reactor and has a separate receiving tank; this device is prior art and will not be described in detail here.

[0037] S4, the gas phase is the crude product, which is collected by condensation at -15℃ and then enters the distillation tower for purification. The operating temperature of the distillation tower is -15~60℃, the pressure is 0.1~0.5MPa, and the number of theoretical plates of distillation is 15~25. The collected fraction is the product trimethylsilane, and the still residue of the distillation tower is the high-boiling impurities;

[0038] S5, filtering the liquid phase in step S3 to obtain a filtrate and a solid material; drying the solid material to obtain a mixed salt whose main components are sodium chloride and aluminum chloride, which can be used as a by-product, wherein the sodium chloride content of the mixed salt is 28-30.5wt%, and the aluminum chloride content is 64-69.5wt%; drying conditions: temperature 130°C, pressure normal pressure;

[0039] S6, the filtrate enters a solvent recovery tower (the solvent recovery tower here is a distillation tower, and is named as a solvent recovery tower here) for distillation, the operating temperature is 20-130°C, the pressure is 0.1-0.3MPa, the number of theoretical plates of the distillation tower is 10-20, and the front fraction is unreacted trimethylchlorosilane and the rear fraction is ethylene glycol dimethyl ether, which are reused separately.

[0040] The trimethylchlorosilane recovered in step S6 can be directly used as a raw material and added to the reactor in step S3 for reaction; the ethylene glycol dimethyl ether recovered in step S6 can be directly used as a reaction solvent in step S2.

[0041] Beneficial effects:

[0042] The invention uses ethylene glycol dimethyl ether as a solvent, and compared with the commonly used solvent systems such as tetrahydrofuran, diethyl ether, methyl tert-butyl ether, etc. in the prior art, the conversion rate of the reaction can be effectively improved, the reaction time can be shortened, and the production efficiency can be improved.

[0043] The invention uses sodium aluminum tetrahydride as a reducing agent, which has lower cost than lithium aluminum hydride, sodium borohydride and the like commonly used in the prior art, and can reduce production costs.

[0044] The present invention separates and recycles the raw material (trimethylchlorosilane) and the solvent (ethylene glycol dimethyl ether), and can effectively achieve the recycling of the solvent, thereby reducing the consumption of the solvent and increasing the utilization rate of the raw material.

[0045] The present invention filters and dries the liquid phase after the reaction to obtain mixed salt (sodium chloride and aluminum chloride) which is exported as a by-product, thereby effectively increasing production revenue.

[0046] The invention removes water from the solvent ethylene glycol dimethyl ether, thereby reducing the generation of impurities and improving the product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0048] The present invention is further described below with reference to specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0049] All raw materials of the present invention have no particular limitation on their sources, and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0050] There is no particular limitation on the purity of all raw materials in the present invention, and the present invention preferably adopts the conventional purity used in the art.

[0051] The devices used in the present invention are not particularly limited and can be any of the commonly used devices in the art.

[0052] Embodiment 1:

[0053] A synthesis and purification process of trimethylsilane comprises the following steps:

[0054] 400g of newly purchased ethylene glycol dimethyl ether was passed through a molecular sieve dehydrator, dehydrated, and added to a 1L reactor. Then 70g of sodium aluminum tetrahydride was added and stirred. The temperature was kept at 30°C and the pressure was normal pressure. Then 500g of trimethylchlorosilane was added dropwise at a flow rate of 50g / h. After the addition was completed, the mixture was kept warm for 2h to obtain a gas phase and a liquid phase.

[0055] At this time, the product trimethylsilane is in gas phase, which is collected into a distillation tower after condensation, and the distillation temperature is 40°C at the bottom of the tower, -5°C at the top of the tower, and the pressure is normal pressure, to obtain 315g of trimethylsilane. The reaction yield is 92.37%.

[0056] The liquid phase is the residual liquid of the reactor. The residual liquid of the reactor is filtered and dried at a drying temperature of 130° C. After drying for 5 hours, 216 g of mixed salt is obtained, which contains 28.7 wt % of sodium chloride and 65.4 wt % of aluminum chloride.

[0057] The mother liquor (filtrate obtained after filtering the residual liquid in the reaction kettle) was transferred to a recovery distillation tower to obtain 7.68g of trimethylchlorosilane in the front fraction and 364g of ethylene glycol dimethyl ether in the back fraction. The final total yield of the reaction was 93.91%.

[0058] Comparative Example 1:

[0059] A synthesis and purification process of trimethylsilane comprises the following steps:

[0060] 400g of newly purchased ethylene glycol dimethyl ether is added directly to a 1L reactor without dehydration, and then 70g of sodium aluminum tetrahydride is added and stirred to mix. Small bubbles can be clearly seen (water reacts with sodium aluminum tetrahydride to generate hydrogen). Keep the temperature at 30°C and the pressure at normal pressure. Then add 500g of trimethylchlorosilane dropwise at a flow rate of 50g / h. After the addition is completed, keep the reaction warm for 2h. The product trimethylsilane is collected into a distillation tower after condensation. The distillation temperature is 40°C at the bottom of the tower, -5°C at the top of the tower, and the pressure is normal pressure to obtain 292g of trimethylsilane. The reaction yield is 85.62%. The reactor residue is filtered and dried at a drying temperature of 130°C. After drying for 5h, the discharging obtains 205g of mixed salt, which contains 28.0wt% of sodium chloride and 64.8wt% of aluminum chloride. The mother liquor (filtrate obtained after filtering the residual liquid in the reaction kettle) was transferred to a recovery distillation tower to obtain 2.15 g of trimethylchlorosilane in the front fraction and 366 g of ethylene glycol dimethyl ether in the back fraction. The final total yield of the reaction was 86.06%.

[0061] It can be seen from this comparative example that ethylene glycol dimethyl ether that has not been dehydrated contains a small amount of water, and the presence of water will react with the reducing agent to directly generate hydrogen, which poses a safety risk.

[0062] Comparative Example 2:

[0063] A synthesis and purification process of trimethylsilane comprises the following steps:

[0064] 400g of the unrectified mother liquor obtained by the method of Example 1 is directly added to a 1L reactor, and then 70g of sodium aluminum tetrahydride is slowly added and stirred to mix. It can be seen that a small amount of trimethylsilane bubbles are generated due to the presence of trimethylsilyl chloride in the recovered mother liquor. Keep the temperature at 30°C and the pressure at normal pressure. Then 500g of trimethylsilyl chloride is added dropwise at a flow rate of 50g / h. After the addition is completed, the reaction is kept warm for 2h. The product trimethylsilane is collected into a distillation tower after condensation. The distillation temperature is 40°C at the bottom of the tower, -5°C at the top of the tower, and the pressure is normal pressure to obtain 307g of trimethylsilane. The reaction yield is 90.03%. The reactor residue is filtered and dried at a drying temperature of 130°C. After drying for 5h, 217g of mixed salt is obtained by discharging, which contains 28.8% sodium chloride and 66.0% aluminum chloride. The mother liquor (filtrate obtained after filtering the residual liquid in the reaction kettle) was transferred to a recovery distillation tower to obtain 9.21 g of trimethylchlorosilane as a front fraction and 360 g of ethylene glycol dimethyl ether as a rear fraction. The final total yield of the reaction was 91.87%.

[0065] It can be seen from this comparative example that the mother liquor contains trimethylchlorosilane and high-boiling impurities remaining from the reaction. If it is directly reused, it is easy to cause a rapid reaction with the reducing agent during the batching process, resulting in the formation of trimethylsilane.

[0066] Embodiment 2:

[0067] A synthesis and purification process of trimethylsilane comprises the following steps:

[0068] 25 kg of newly purchased ethylene glycol dimethyl ether was passed through a molecular sieve dehydrator, dehydrated, and added to a 500 L reactor. 180 kg of recycled ethylene glycol dimethyl ether was added and mixed. The temperature was controlled at 10 ° C. Then 33 kg of sodium aluminum tetrahydride solid was added and stirred. The reaction temperature was controlled at 10 ° C and the pressure was normal pressure. Then 250 kg of trimethylchlorosilane was added dropwise at a flow rate of 25 kg / h. After the addition was completed, the reaction was kept warm for 3 hours to obtain a gas phase and a liquid phase.

[0069] At this time, the product trimethylsilane is in gas phase, which is collected by condensation and then sent to a distillation tower. The distillation temperature is 50°C at the bottom of the tower, -10°C at the top of the tower, and the pressure is normal pressure, and 162 kg of trimethylsilane is obtained. The reaction yield is 94.87%.

[0070] The liquid phase is the residual liquid of the reactor. The residual liquid of the reactor is transferred to a three-in-one reactor for filtration and drying at a drying temperature of 130°C. After drying for 5 hours, 108.24 kg of mixed salt is obtained, which contains 29.5% sodium chloride and 67.2% aluminum chloride.

[0071] The mother liquor (filtrate obtained after filtering the residual liquid in the reaction kettle) was transferred to a recovery distillation tower to obtain 3.2 kg of trimethylchlorosilane as the front fraction and 183 kg of ethylene glycol dimethyl ether as the rear fraction. The final total yield of the reaction was 96.13%.

[0072] The recovered ethylene glycol dimethyl ether in this embodiment is obtained by distilling the filtrate (also referred to as mother liquor) obtained after filtering the liquid phase according to the method of the present invention. Specifically, the method of Example 1 can be used, and the methods of other embodiments of the present invention can also be used.

[0073] Embodiment 3:

[0074] A synthesis and purification process of trimethylsilane comprises the following steps:

[0075] 25 kg of newly purchased ethylene glycol dimethyl ether was passed through a molecular sieve dehydrator, dehydrated, and added to a 500 L reactor. 180 kg of recycled ethylene glycol dimethyl ether was added and mixed. The temperature was controlled at 40 ° C. Then 37.2 kg of sodium aluminum tetrahydride solid was added and stirred. The reaction temperature was controlled at 40 ° C and the pressure was normal pressure. Then 250 kg of trimethylchlorosilane was added dropwise at a flow rate of 25 kg / h. After the addition was completed, the reaction was kept warm for 3 hours to obtain a gas phase and a liquid phase.

[0076] At this time, the product trimethylsilane is in gas phase, which is collected by condensation and then sent to a distillation tower. The distillation temperature is 50°C at the bottom of the tower, -10°C at the top of the tower, and the pressure is normal pressure, and 166.2 kg of trimethylsilane is obtained. The reaction yield is 97.34%.

[0077] The liquid phase is the residual liquid of the reactor. The residual liquid of the reactor is transferred to a three-in-one reactor for filtration and drying at a drying temperature of 130°C. After drying for 5 hours, 114.49 kg of mixed salt is obtained, which contains 28.6% sodium chloride and 65.2% aluminum chloride.

[0078] The mother liquor (filtrate obtained by filtering the residual liquid in the reaction kettle) was transferred to a recovery distillation tower to obtain 0.4 kg of trimethylchlorosilane as the front fraction and 186 kg of ethylene glycol dimethyl ether as the rear fraction. The final total yield of the reaction was 97.50%.

[0079] The recovered ethylene glycol dimethyl ether in this embodiment is obtained by distilling the filtrate (also referred to as mother liquor) obtained after filtering the liquid phase according to the method of the present invention. Specifically, the method of Example 1 can be used, and the methods of other embodiments of the present invention can also be used.

[0080] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A synthesis and purification process of trimethylsilane, Features: The following steps are involved: Dehydrating ethylene glycol dimethyl ether and mixing it with sodium aluminum tetrahydride to obtain a mixed solution, and then adding trimethylsilyl chloride to react; After the reaction, a gas phase and a liquid phase are obtained; the gas phase is collected and purified to obtain trimethylsilane.

2. A synthesis and purification process of trimethylsilane according to claim 1, Features: The mass ratio of ethylene glycol dimethyl ether to sodium aluminum tetrahydride is (4-10):

1.

3. A synthesis and purification process of trimethylsilane according to claim 1, Features: The molar ratio of sodium aluminum tetrahydride to trimethylsilyl chloride is (1.05-1.2):

4.

4. A synthesis and purification process of trimethylsilane according to claim 1, Features: The reaction temperature of trimethylsilyl chloride and the mixed solution is 0-40° C., and the reaction pressure is 0.1-0.5 MPa.

5. A synthesis and purification process of trimethylsilane according to claim 1, Features: The trimethylsilyl chloride is added dropwise for 10 hours.

6. A synthesis and purification process of trimethylsilane according to claim 1, Features: The gas phase is collected by condensation at -15°C and then enters a distillation tower for purification; the operating temperature of the distillation tower is -15 to 60°C and the pressure is 0.1 to 0.5 MPa.

7. A process for synthesizing and purifying trimethylsilane according to claim 6, Features: After the gas phase is condensed, it enters the distillation tower. The collected fraction is trimethylsilane, and the bottoms of the distillation tower are high-boiling impurities.

8. A synthesis and purification process of trimethylsilane according to claim 1, Features: The liquid phase is filtered to obtain a filtrate and a solid material; the solid material is dried and recovered as a by-product.

9. A process for synthesizing and purifying trimethylsilane according to claim 7, Features: The filtrate is distilled using a distillation tower; during the distillation process: the operating temperature is 20-130° C., and the pressure is 0.1-0.3 MPa.

10. A process for synthesizing and purifying trimethylsilane according to claim 9, Features: The filtrate enters a distillation tower, and the front fraction obtained by distillation is unreacted trimethylchlorosilane, and the rear fraction is ethylene glycol dimethyl ether; the obtained trimethylchlorosilane and ethylene glycol dimethyl ether can be recycled.

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