High-purity diborane as well as production method, industrial equipment and application thereof

Abstract

The invention belongs to the field of chemical engineering, and particularly relates to high-purity diborane as well as a production method, industrial equipment and application thereof. The method comprises a diborane production stage and a diborane purification stage, and the diborane production stage comprises the following steps: feeding BCl3 for the first time: enabling the temperature of a reaction kettle to be 20-22 DEG C, adding BCl3 into the reaction kettle at a constant speed, and controlling the feeding speed of the BCl3 to be 50-60g / min, so that sodium borohydride reacts with boron trichloride; feeding BCl3 for the second time: controlling the temperature of the reaction kettle to be 35-45 DEG C, starting to feed after the temperature reaches 35-45 DEG C, controlling the feeding speed to be 35-45g / min, and reacting to generate diborane; the purification stage of the diborane comprises purification by rectifying the crude product of the diborane. The production method of the high-purity diborane has the advantages of high yield, high purity, safety and low cost.

Description

Technical Field

[0001] The invention belongs to the field of chemical industry, and specifically relates to high-purity diborane and a production method, industrial equipment and application thereof. Background Art

[0002] Diborane is an important chemical raw material, widely used in semiconductor manufacturing, organic synthesis and other fields. Diborane is a gas with a boiling point of -92.5°C, which is flammable and highly toxic, and can be used as a fuel and rocket propellant. The molecular formula B2H6 is a dopant source gas in the semiconductor process, that is, the P-type source in the PN junction process, and the product quality requirements are extremely stringent. This product is flammable, explosive and toxic. At present, the production methods of diborane mainly include chemical reduction method, thermal decomposition method, etc., but these methods have problems such as low efficiency, high cost, poor safety, and low product purity. Therefore, it is of great significance to develop a diborane production method that can be applied to industrial large-scale production with high product yield, high purity, safety and low cost.

[0003] Diborane is commonly used in the semiconductor industry to introduce boron atoms into silicon wafers to adjust the conductivity type (P-type doping). Even trace amounts of impurities (such as oxygen, water, metal ions, etc.) can cause the following problems: (1) abnormal electrical properties (2) lattice defects, reducing the chip quality rate (3) chemical vapor deposition, affecting its insulation, thermal conductivity or mechanical strength. The 99.9999% purity of diborane is a rigid requirement of the semiconductor industry for material performance, process safety and yield control. Any trace impurities may trigger a domino effect, resulting in huge economic losses. Therefore, from synthesis, purification to packaging, it must be carried out in a strict oxygen-free and water-free environment. Summary of the invention

[0004] One of the objects of the present invention is to provide a method for producing high-purity diborane, comprising a diborane production stage and a diborane purification stage, wherein the diborane production stage comprises: First BCl3 feeding: Keep the temperature of the reactor at 20-22°C, add BCl3 into the reactor at a uniform speed, and control the BCl3 feeding rate at 50-60g / min to allow sodium borohydride to react with boron trichloride; Second BCl3 feeding: the temperature of the reactor is controlled at 35-45°C, and feeding is started after the temperature is reached, and the feeding rate is controlled at 35-45g / min to react and generate diborane; The diborane purification stage includes purification by distillation of crude diborane.

[0005] The synthesis of diborane is divided into two stages, and the reaction formula is as follows: (1) 7NaBH4+BCl3=4NaB2H7+3NaCl; (2) 6NaB2H7+2BCl3=7B2H6+6NaCl.

[0006] The production phase includes the following steps: (1) adding a solvent and sodium borohydride and stirring; (2) Evacuate the reactor and replace it with helium; (3) First BCl3 feeding: Keep the temperature of the reactor at 20-22°C, open the helium bypass valve, adjust the flow rate to 0.5L / min, and add BCl3 into the reactor at a uniform rate. The BCl3 feeding rate is controlled at 50-60g / min, and the feeding is completed in about 1-1.5h; (4) After the first BCl3 feed is completed, blow it out with helium; (5) Before the second BCl3 feed, check to ensure that there is a pressure of 0.5 MPa in the freezer. Before the second BCl3 feed, the freezer should be replaced with helium for more than 3 times. Fill the cold hydrazine with dry ice, place the freezer in the cold hydrazine, add liquid nitrogen to the cold hydrazine to 1 / 2 of the freezer, open the valve between the freezers, open the connecting valve between the freezer and the bus, and evacuate the freezer to normal pressure; (6) Second BCl3 feeding: The temperature of the reactor was controlled at 35-45°C. After reaching the temperature, the feeding was started. The feeding rate was controlled at 35-45 g / min. The mercury gauge pressure difference was less than 700 mmHg. The feeding was completed in about 2 hours. (7) After the second BCl3 feed is completed, adjust the helium flow rate for purging; (8) Fill the bus with helium at a pressure of 1.0 MPa and evacuate to normal pressure, repeat this process several times, evacuate the freezer to 700-760 mmHg, turn off the vacuum pump, turn off the mercury gauge, remove the Dewar flask, heat the freezer to room temperature with circulating water, open the valve of the pre-frozen cylinder, and collect diborane; (9) Discharge the residual liquid, rinse the residue in the reactor with waste solvent until the discharged liquid is clear, discharge the solvent in the reactor and the cold hydrazine, and after discharging the residual liquid, maintain the pressure of the reactor at 0.4 MPa, and maintain the pressure of the bus and the freezer at 1.0 MPa.

[0007] Prior to step (1) of the production stage, the production equipment is also leak tested.

[0008] Before step (1) of the production stage, the process also includes taking material from a BCl3 feeder: first, connect the BCl3 cylinder and the feeder, cool the BCl3 feeder to 0°C with a water bath, evacuate the cylinder to 700-750 mmHg with a vacuum pump, fill it with helium to a positive pressure, and then evacuate the cylinder to 700-750 mmHg, repeat this process several times, close the vacuum valve, open the cylinder valve, observe the electronic scale, take the required amount of BCl3, close the cylinder valve, and cut off the BCl3 pipeline.

[0009] During the production stage, 7.5 kg of sodium borohydride and 100 L of diethylene glycol dimethyl ether were used; 3.34 kg of BCl3 was fed for the first time, and 4.46 kg of BCl3 was fed for the second time.

[0010] In step (1) of the production stage, stirring is performed with a stirrer at a frequency of about 12 Hz.

[0011] Preferably, step (2) in the production stage includes: closing the mercury-sealed valve, opening the valve between the cold hydrazine, the product air inlet valve, the vacuum pump valve, and the mercury gauge valve, evacuating to 700-750 mmHg, closing the vacuum pump valve and the mercury gauge valve, filling with helium at a pressure of 0.2 MPa, opening the exhaust valve, exhausting to normal pressure, and closing the exhaust valve; repeating the above operation multiple times.

[0012] Preferably, step (7) in the production stage is specifically as follows: after the second BCl3 feeding is completed, the helium flow rate is adjusted to 1.5-2.5 L / min and the purge is performed for 6-10 hours.

[0013] The distillation comprises the following steps: (1) Leakage test of distillation tower and busbar; (2) replacing the distillation tower and the bus with high-purity helium; (3) Refrigeration: Make the alcohol temperature in the tower kettle insulation tank reach -70°C, then supply liquid nitrogen from the upper kettle to make the temperature of the upper kettle lower than that of the lower kettle, and check whether the distillation tower has any leakage at low temperature; (4) Feeding: Open the valve of the tower top outlet, close the fine-tuning valve and the busbar valve, and after evacuating the system, supply diborane from the feed port in the middle of the tower column. Observe the pressure indicator in the tower, and control the pressure of the tower bottom and tower head to be less than 0.5 MPa by controlling the supply rate of liquid nitrogen and diborane. (5) Full reflux: control the tower bottom temperature to -75℃~-65℃, the pressure to below 0.5MPa, the tower head temperature to -155℃~-135℃, the pressure to below 0.5MPa, and reflux for 12 hours; (6) Heading: The product bus is evacuated to the fine-tuning valve, and the fine-tuning valve is adjusted to allow the gas phase in the tower to slowly enter the bus. The flow rate is controlled at 250-350 ml / min. When the pressure of the bus and the sample bottle is close to the pressure in the tower, the methane and methyl chloride contents are sampled and analyzed. The remaining gas is collected into an aluminum bottle frozen by liquid nitrogen. The fine-tuning valve is closed, and the system is flushed with helium. The sample bottle is removed and the fine-tuning valve is opened again to continue heading. When the pressure in the tower is less than 0.1 MPa, a small amount of helium can be filled in to continue heading. Sampling and analysis are performed every 3-5 hours. As the methane content in the tower decreases, the tower top temperature gradually rises to -110°C~-90°C. When the methane content is analyzed to be less than 100 ppm, the receiving bottle is replaced to receive the finished product. (7) Receiving finished products: The tower head temperature is controlled at -110℃~-90℃ and the pressure is 0.15MPa-0.2MPa to receive the finished products. The methane and chloroform contents are analyzed every 1.5-2.5 hours until the methane content is less than 5PPm and the chloroform content is less than 10PPm. The high-purity diborane is received by changing the bottle.

[0014] After the distillation step (7), the method further includes the step (8) of collecting residual liquid: when the distilled gas component exceeds the limit value, the product is stopped from being received, the residual liquid is collected in a new bottle, and refrigeration is stopped. When the bottom temperature of the tower reaches -40°C and the pressure is at normal pressure, no more collection is performed.

[0015] Preferably, after the distillation step (8), the method further comprises the step (9) of treating the distillation tower: flushing the system with high-purity nitrogen, venting the waste gas through alkaline solution, and filling the system with 0.3 MPa high nitrogen after the system is replaced cleanly for later use.

[0016] The second object of the present invention is to provide an industrial equipment for producing high-purity diborane, including a reactor, a cold trap, a bus, a freezer and a BCl3 feeder, wherein the freezer includes a first freezer and a second freezer; the reactor has inlets for sodium borohydride and a solvent, an inlet for BCl3 and a gas outlet; the reactor is connected to the cold trap and also to a mercury sealing device; the cold trap is connected to the bus; the bus is also respectively connected to the freezer, a vacuum pump, a mercury meter and a wide-mouth Dewar flask.

[0017] A third object of the present invention is to provide high-purity diborane obtained by the aforementioned production method.

[0018] A fourth object of the present invention is to provide the application of the aforementioned high-purity diborane in semiconductor preparation and organic synthesis.

[0019] Beneficial effects: The production method of high-purity diborane suitable for industrial application is safe, low-cost and high-yield, and can obtain high-purity diborane.

[0020] The sodium borohydride and boron trichloride of the present invention react in stages to efficiently synthesize diborane.

[0021] This method uses diethylene glycol dimethyl ether as a solvent. It has a large solubility in sodium borohydride and a small solubility and reactivity with boron trichloride, so better results can be achieved.

[0022] The byproduct of this method is NaCl, which is insoluble in diethylene glycol dimethyl ether. The used solvent can be reused by filtering out the insoluble matter.

[0023] This method does not use fluorine compounds that are highly toxic and difficult to treat as waste. Instead, boron trichloride is added in two stages and reacted under different conditions. The device is simple and easy to operate. The diborane produced has higher purity and greatly improved yield than that produced by other methods at home and abroad. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of an apparatus for the production of diborane.

[0025] Among them, 1. Reactor; 2. Cold trap; 3. Bus; 4. Freezer; 4.1. First freezer; 4.2. Second freezer; 4.3. Third freezer; 4.4. Fourth freezer; 5. BCl3 feeder; 6. Agitator; 7. Mercury sealing device; 8. Vacuum pump; 9. Mercury meter; 10. Wide-mouth Dewar flask. DETAILED DESCRIPTION

[0026] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0027] The term "displacement" refers to replacing the air in a container with helium. Reactor displacement or freezer displacement refers to replacing the air in a reactor or freezer with helium.

[0028] The term "de-heading" refers to the removal of non-condensable gases accumulated at the highest point of the distillation tower (i.e., the tower head).

[0029] The method of the present invention adopts a boron trichloride reduction method to prepare diborane, and has the following characteristics: 1) The reaction is carried out in stages. The first stage is an exothermic reaction with a reaction temperature of 20℃~22℃; the second stage is an endothermic reaction with a temperature of 35℃~45℃. High-purity diborane can be produced efficiently.

[0030] 2) This method uses diethylene glycol dimethyl ether as a solvent. It has a large solubility in sodium borohydride and a small solubility and reactivity with boron trichloride, so better results can be achieved.

[0031] 3) The byproduct of this method is NaCl, which is insoluble in diethylene glycol dimethyl ether. The solvent used can be reused by filtering out the insoluble matter.

[0032] 4) This method does not use fluorine compounds that are highly toxic and difficult to dispose of as waste. Instead, boron trichloride is added in two steps and reacted under different conditions. The device is simple and easy to operate. The diborane produced is of higher purity and much higher yield than that produced by other methods at home and abroad. The yield can reach 98%.

[0033] Production principle of diborane: The preparation of diborane is divided into two stages, and the reaction formula is as follows: (1) 7NaBH4+BCl3=4NaB2H7+3NaCl; (2) 6NaB2H7+2BCl3=7B2H6+6NaCl.

[0034] The first stage listed in reaction formula (1) is an exothermic reaction and the second stage listed in reaction formula (2) is an endothermic reaction. The synthesis reaction is divided into two stages.

[0035] Sodium borohydride is dissolved in diethylene glycol dimethyl ether, and BCl3 is carried into the solution by helium to synthesize diborane. The product is collected in a freezer under liquid nitrogen freezing through three cold hydrazines and a bus. After the reaction is completed, diborane is evaporated into a steel bottle and stored at low temperature.

[0036] The raw material boron trichloride is a colorless gas with a pungent odor at room temperature and pressure, and its boiling point is about 12.5°C. This characteristic means that at a slightly lower temperature (such as 0°C), boron trichloride can easily change from gas to liquid.

[0037] At present, the methods for refining diborane at home and abroad include adsorption, distillation and a combination of adsorption and distillation.

[0038] 1) The adsorption method uses low-temperature adsorption and temperature-raising desorption to remove most of CH4, CO2, etc. However, since the boiling point (-88°C) and molecular weight (30) of C2H6 are very close to those of diborane, the effect of removing C2H6 by adsorption is very poor.

[0039] 2) Distillation and adsorption are combined to produce high-purity diborane.

[0040] The method is to combine low boiling point components such as H2, N2, O2, Ar, CO, CH4 and CH3Cl, C2H5Cl, B4H 10 , B5H9 and other high boiling point components, especially the crude B2H6 with impurities such as CO2 and C2H6 that are close to the boiling point of B2H6 and difficult to separate by distillation, is adsorbed while distilling. An adsorbent that can adsorb and remove these impurities is selected, that is, distillation and adsorption are combined to make the total impurities less than l×10 -6 , to produce 99.995% high purity B2H6. But the equipment is complicated and the process is long.

[0041] 3) Intermittent low-temperature pressure distillation is to separate impurities under pressure. First, separate the impurities with a boiling point lower than the product, and then raise the temperature to receive the product. Impurities with high boiling points remain at the bottom of the tower. This method is simple in process, short in flow, and easy to control. This method adopts this method. Prepare 99.9999% high-purity diborane.

[0042] Example 1 1. Synthesis of diborane Raw materials: sodium borohydride, boron trichloride.

[0043] Auxiliary materials: solvent diethylene glycol dimethyl ether, liquid nitrogen, dry ice, helium, ice cubes.

[0044] Equipment: helium cylinder, BCl3 feeder, reactor, dry ice-cooled hydrazine, wide-mouth Dewar flask, busbar, spare cylinder.

[0045] like Figure 1 As shown, the production equipment includes a reactor 1, a cold trap 2, a bus 3, a freezer 4 and a BCl3 feeder 5. The freezer 4 has a first freezer 4.1, a second freezer 4.2, a third freezer 4.3 and a fourth freezer 4.4. An agitator 6 is arranged in the reactor 1. The reactor 1 is fixed, and the cold trap 2, bus 3, freezer 4 and the like connected by a hose are movable. The reactor 1 has inlets for sodium borohydride and solvent, and also has an inlet for BCl3. The reactor 1 is connected to the cold trap 2 and also to a mercury sealing device 7. The cold trap 2 is connected to the bus 3. The bus 3 is respectively connected to the freezer 4, the vacuum pump 8, the mercury meter 9 and the wide-mouthed Dewar flask 10.

[0046] 1. Leak detection of production equipment

[0047] For the first synthesis of each batch, the bus and freezer have no obvious changes under 5MPa helium pressure for 12 hours, and the reactor has no obvious changes under 0.4MPa helium pressure for 12 hours, which means the leak test is qualified; for the synthesis of the same batch afterwards, the bus and freezer have no obvious changes under 5MPa ammonia pressure for 5-8 hours, and the reactor has no obvious changes under 0.4MPa helium pressure for 5-8 hours, which means the leak test is qualified. Note that the pressure changes should be observed at the same temperature.

[0048] 2. Preparation before production

[0049] 7.5 kg of sodium borohydride, set aside.

[0050] 100L of diethylene glycol dimethyl ether was taken on site.

[0051] BCl3 feeder material collection: first connect the BCl3 cylinder and feeder, cool the BCl3 feeder to 0℃ with a water bath, evacuate to 700-750mmHg with a vacuum pump; fill with helium to positive pressure, evacuate to 700-750mmHg, repeat 3 times, and close the vacuum valve. Open the cylinder valve, observe the electronic scale, take 7.8kg of BCl3, close the cylinder valve, and cut off the BCl3 pipeline.

[0052] 3. Production process

[0053] 3.1 Add solvent and sodium borohydride

[0054] Add the solvent and sodium borohydride, turn on the stirrer, and set the stirring frequency at about 12 Hz (30-40 revolutions per minute).

[0055] 3.2 Reactor evacuation and replacement

[0056] Close the mercury seal valve, open the valve between the cold hydrazine, the product air inlet valve, the vacuum pump valve, and the mercury gauge valve, evacuate to 700-750mmHg, close the vacuum pump valve and the mercury gauge valve, fill with helium to 0.2MPa pressure, open the drain valve, exhaust to normal pressure, and close the drain valve. Repeat the above operation 4 times.

[0057] 3.3 First BCl3 feed

[0058] Heat BCl3 in a water bath, control the temperature at 25℃, 20-22℃ in the kettle, circulate the water bath in the reactor jacket, set the temperature at 20℃. Start feeding, open the helium bypass valve, and adjust the flow rate to 0.5L / min. First open the BCl3 feeder outlet, then open the inlet, and add BCl3 into the kettle at a uniform speed. The BCl3 feeding rate is controlled at about 55g / min, and the feed is 3.34kg, about 1-1.5kg / h. Observe the mercury sealing bubble situation.

[0059] 3.4 Helium Blowing

[0060] After the first BCl3 feed is completed, close the mercury seal valve, open the valve between the cold hydrazine, the product air inlet valve, the vacuum pump valve, and the mercury meter valve, evacuate to 700-760 mmHg, close the vacuum pump valve and the mercury meter valve, fill with helium at a pressure of 0.2 MPa, open the drain valve, exhaust to normal pressure, and close the drain valve. Repeat the above operation 4 times.

[0061] 3.5 Inspection

[0062] Before the second feeding, make sure that the pressure in the freezer is 0.5MPa. The freezer should be replaced with helium before feeding, and replaced 4 times. Fill the cold hydrazine with dry ice.

[0063] 3.6 Place the freezer in a cold hydrazine, add liquid nitrogen to the cold hydrazine to 1 / 2 of the freezer, open the valve between the freezer, open the connecting valve between the freezer and the exhaust, and empty the freezer to normal pressure.

[0064] 3.7 Second BCl3 feed

[0065] Before feeding, close the upper and lower bus connection valves, open the product air inlet valve, mercury gauge valve, and freezer inlet connection valve on the upper row; open the freezer outlet connection valve, bubbler (not shown) connection valve, freezer inlet valve, and freezer outlet valve on the lower row. Control the reactor temperature at 40°C, start feeding after the temperature is reached, control the feeding rate to 40g / min, the mercury gauge pressure difference <700mmHg, feed 4.46kg, and complete the feeding in about 2h. Observe the liquid nitrogen level frequently during the production process and keep it at 1 / 2 of the freezer height.

[0066] 3.8 Purge

[0067] After the feeding was completed, the helium flow rate was adjusted to 2 L / min and the purge was carried out for 8 hours.

[0068] 3.9 Volatilization and collection

[0069] Before volatilization, fill the bus with helium to a pressure of 1.0 MPa, exhaust to normal pressure, and repeat 10 times. Open the inlet valves of freezer 4.1 and freezer 4.2 connected in series, connect the freezer valves, and exhaust connection valves, open the vacuum pump valve and mercury gauge valve, evacuate to 700-760 mmHg, turn off the vacuum pump, turn off the mercury gauge, and remove the Dewar flask. Use circulating water to heat the freezer to room temperature, open the valve of the pre-frozen cylinder, and collect diborane. Repeat the above operation for freezer 4.3 and freezer 4.4 connected in series.

[0070] 3.10 Release residual liquid and maintain pressure

[0071] Open the lower ball valve of the reactor, release the residual liquid, and rinse the residue in the reactor with 15L of waste solvent until the released liquid is clear. Drain the solvent in the reactor and cold hydrazine. After releasing the residual liquid, maintain the pressure of the reactor at 0.4MPa, and the pressure of the bus and freezer at 1.0MPa.

[0072] The yield of crude diborane obtained at this time is 98% and the purity is 96%.

[0073] 3.11 Post-production processing

[0074] After a batch is produced, remove the BCl3 inlet pipe, purge it with nitrogen, observe the condition of the inner wall and replace it in time. Check the plug of the sodium borohydride feed port and the gasket, and replace it if necessary. The production system is evacuated and replaced with helium 5 times, maintaining the pressure at 0.4MPa.

[0075] 4. Safety precautions

[0076] (1) Diborane is a flammable and explosive gas, and is highly toxic and decomposes when exposed to water. Therefore, the system must have high air tightness and must be clean and dry. Production must be carried out in a fume hood.

[0077] (2) The -50℃ cold trap of the reactor is used to prevent the volatilization of diethylene glycol dimethyl ether, and the -78℃ glass cold trap is used to remove high-boiling impurities. The feeding speed should be relatively stable. If the feeding is too fast, a large amount of gas will be generated, and the impurity removal effect of the cold trap will be reduced.

[0078] (3) To speed up the addition of boron trichloride, the cold trap can be placed in warm water at 25℃~30℃ to make it boil slightly, but it should be controlled not to be too fast. The mercury seal connected to the reactor is to prevent pipe blockage and excessive pressure in the reactor, so that no bubbles are produced.

[0079] (4) When adding liquid nitrogen to the liquid nitrogen barrel of the freezer, negative pressure may form in the freezer. The exhaust valve should be closed in time to prevent backflow.

[0080] (5) The refrigerant of the cold trap can be prepared by adding alcohol to dry ice or liquid nitrogen. Both dry ice and liquid nitrogen are extremely cold substances. Avoid contact with the skin to prevent frostbite. Protective gloves should be worn.

[0081] (6) When diborane evaporates, it takes a long time to heat up. You can pour water on the surface of the freezer to speed up the volatilization. However, do not pour water into the small holes inside at the beginning, because the ice formed will melt slowly.

[0082] (7) When stored at room temperature, diborane will partially decompose to produce perborane and hydrogen. Therefore, it should be stored in a freezer or diluted with nitrogen to reduce decomposition.

[0083] (II) Distillation of diborane

[0084] The purity of diborane produced by the above method is generally 96%. Diborane produced by the reaction of boron trichloride and sodium borohydride in a solvent contains 1.5% methane, 1.5% methyl chloride, and trace amounts of impurities such as CO2, H2, N2, and O2. In order to meet the needs of ultra-large-scale and extra-large-scale integrated circuits, diborane must be purified to remove various impurities and achieve a purity of 99.9999%.

[0085] 1. Principle

[0086] Distillation is to use the different distribution of different substances in the gas and liquid phases. The steam generated during distillation interacts with the liquid formed when the steam condenses. The high-boiling point components in the gas phase and the low-boiling point components in the liquid phase are condensed and vaporized multiple times in opposite directions to achieve the separation of the mixture. The boiling points of methane and methyl chloride in diborane are very different from the boiling point of diborane. In distillation, methane and low-boiling point impurities such as nitrogen, hydrogen, and oxygen are removed in the tower top, and high-boiling point impurities such as methyl chloride are left in the residual liquid. High-purity diborane can be obtained in the intermediate fraction.

[0087] 2. Raw materials and equipment

[0088] Table 1: Raw materials and equipment

[0089] The distillation tower is divided into three parts: the tower bottom, the tower body, and the tower top. The highest point of the tower top is called the tower head. There are cooling pipes outside the distillation tower and inside the tower bottom.

[0090] 3. Operation steps

[0091] 3.1 Leak test of distillation tower and busbar. Connect the feed port of the distillation tower to the raw material busbar with a stainless steel hose, and connect the discharge port to the product busbar with a stainless steel hose through a fine-tuning valve. Fill the system with nitrogen at 5.0 MPa. If the pressure does not drop for 2 hours, the leak test is qualified.

[0092] 3.2 Replacement. Clamp the raw gas cylinder, sample bottle, and receiving product bottle onto the busbar, replace the distillation tower and busbar with high-purity helium three times, and fill with helium at 0.5 MPa.

[0093] 3.3 Refrigeration. Add industrial alcohol to the tower kettle insulation tank and tower head, connect and insulate the cooling pipes of the tower head, tower column and tower kettle insulation tank with vacuum hose, connect the liquid outlet of the liquid nitrogen tank with the cooling pipe of the tower kettle insulation tank with vacuum hose, and let the liquid nitrogen flow from the tower kettle insulation tank through the tower column to the cooling pipe of the tower head. When the alcohol temperature in the tower kettle insulation tank reaches -70℃, switch to the upper kettle to supply liquid nitrogen, so that the upper kettle temperature is lower than the lower kettle temperature, and check whether there is leakage in the low temperature distillation tower. If there is a leak, deal with it in time.

[0094] 3.4 Feeding. Open the valve of the outlet port at the top of the tower, close the fine-tuning valve and the busbar valve, and after evacuating the system, supply diborane from the feed port in the middle of the tower column. Observe the pressure indicator in the tower, and control the pressure of the tower bottom and the tower head to be lower than 0.5MPa. It can fluctuate between 0.3 and 0.5MPa. When the pressure is high, speed up the supply of liquid nitrogen, and when the pressure is low, increase the speed of supplying diborane.

[0095] 3.5 Full reflux. Control the tower bottom temperature to -70℃±5℃, the pressure to below 0.5MPa, the tower head temperature to -145±10℃, the pressure to below 0.5MPa, and reflux for 12 hours.

[0096] 3.6 Head removal. Pump the product bus to the fine-tuning valve, adjust the fine-tuning valve to allow the gas phase in the tower to slowly enter the bus, and control the flow rate at 300ml / min. When the pressure of the bus and the sample bottle is close to the pressure in the tower, take samples to analyze the methane and methyl chloride content, and collect the remaining gas into the aluminum bottle frozen by liquid nitrogen. Close the fine-tuning valve, blow the system with helium, remove the sample bottle, and open the fine-tuning valve to continue head removal. When the pressure in the tower is less than 0.1MPa, a small amount of helium (pressure 0.3MPa) can be filled to continue head removal. Sampling and analysis are performed every 4 hours. As the methane content in the tower decreases, the temperature at the top of the tower gradually rises to -100℃±10℃, until the methane content is less than 100PPm, and the receiving bottle is replaced to receive the finished product.

[0097] 3.7 Receive the finished product. The tower head temperature is controlled at -100±10℃, and the pressure is 0.15MPa-0.2MPa. The finished product can be received. The methane and chloroform are analyzed every 2 hours. The content is less than 5PPm for methane and less than 10PPm for chloroform. The high-purity diborane is received by changing the bottle.

[0098] 3.8 Collect the residual liquid. When the distilled gas component exceeds 1500 grams (1200~1300 liters), stop receiving the finished product, change the bottle to collect the residual liquid, and stop refrigeration. When the temperature of the tower bottom reaches -40℃ and the pressure is normal pressure, stop collecting.

[0099] 3.9 Treat the distillation tower. Use high-purity nitrogen to purge the system, exhaust gas is vented through alkali solution, and the system is filled with 0.3MPa high nitrogen after replacement for later use.

[0100] 4. Safety precautions

[0101] 4.1 Low temperature distillation of diborane is only 2kg, but considering its flammability, explosion and high toxicity, it will be more than 1700 liters after gasification. It must be operated with great care. The distillation tower system cannot leak and the pressure cannot be too high. In order to prevent serious consequences caused by air entering the distillation tower, pressurized distillation is used. During the whole distillation process, the pressure is always kept higher than the normal pressure.

[0102] 4.2 Low temperature distillation uses liquid nitrogen as the cooling source, and the liquid nitrogen must be sufficient. When the liquid nitrogen is insufficient, the distillation should be stopped and the raw materials should be recovered.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the patent protection scope of the present invention.

Claims

1. A method for producing high-purity diborane, characterized in that: The production method comprises a diborane production stage and a diborane purification stage, wherein the diborane production stage comprises: First BCl3 feeding: Keep the temperature of the reactor at 20-22°C, add BCl3 into the reactor at a uniform speed, and control the BCl3 feeding rate at 50-60g / min to allow sodium borohydride to react with boron trichloride; Second BCl3 feeding: the temperature of the reactor is controlled at 35-45°C, and the feeding is started after the temperature is reached, and the feeding rate is controlled at 35-45g / min to react and generate the diborane; The diborane purification stage includes purification by distillation of crude diborane.

2. The production method according to claim 1, characterized in that The production phase includes the following steps: (1) adding a solvent and sodium borohydride into the reaction kettle and stirring; (2) evacuating the reactor and replacing it with helium; (3) First BCl3 feeding: Keep the temperature of the reactor at 20-22°C, open the helium bypass valve, adjust the flow rate to 0.5L / min, and uniformly add BCl3 into the reactor. The BCl3 feeding rate is controlled at 50-60g / min and the feeding is completed in 1-1.5h; (4) After the first BCl3 feed is completed, blow it out with helium; (5) Before the second BCl3 feeding, check to ensure that there is a pressure of 0.5 MPa in the freezer. Before the second BCl3 feeding, the freezer should be replaced with helium for more than 3 times. Fill the cold hydrazine with dry ice, place the freezer in the cold hydrazine, add liquid nitrogen to the cold hydrazine to 1 / 2 of the freezer, open the valve between the freezers, open the connecting valve between the freezer and the bus, and evacuate the freezer to normal pressure; (6) Second BCl3 feeding: The temperature of the reactor was controlled at 35-45°C. After reaching the temperature, the feeding was started. The feeding rate was controlled at 35-45 g / min. The mercury gauge pressure difference was less than 700 mmHg. The feeding was completed in about 2 hours. (7) After the second BCl3 feed is completed, adjust the helium flow rate for purging; (8) Fill the bus with helium at a pressure of 1.0 MPa and evacuate to normal pressure, repeat this process several times, evacuate the freezer to 700-760 mmHg, turn off the vacuum pump, turn off the mercury gauge, remove the Dewar flask, heat the freezer to room temperature with circulating water, open the valve of the pre-frozen cylinder, and collect diborane; (9) Discharge the residual liquid, rinse the residue in the reactor with waste solvent until the discharged liquid is clear, discharge the solvent in the reactor and the cold hydrazine, and after discharging the residual liquid, maintain the pressure of the reactor at 0.4 MPa, and maintain the pressure of the bus and the freezer at 1.0 MPa.

3. The production method according to claim 1, characterized in that The synthesis of diborane is divided into two stages, and the reaction formula is as follows: (1) 7NaBH4+BCl3=4NaB2H7+3NaCl; (2) 6NaB2H7+2BCl3=7B2H6+6NaCl.

4. The production method according to claim 2, characterized in that: Prior to step (1) of the production stage, the production equipment is also leak tested; Before step (1) of the production stage, the step also includes taking out the BCl3 feeder: first connect the BCl3 cylinder and the feeder, cool the BCl3 feeder to 0°C with a water bath, evacuate to 700-750 mmHg with a vacuum pump, fill with helium to positive pressure, and then evacuate to 700-750 mmHg, repeat several times, close the vacuum valve, open the cylinder valve, observe the electronic scale, take out the required amount of BCl3, close the cylinder valve, and cut off the BCl3 pipeline; stirring with a stirrer in step (1) of the production stage; Step (2) in the production stage includes: closing the mercury-sealed valve, opening the valve between the cold hydrazine, the product air inlet valve, the vacuum pump valve, and the mercury gauge valve, evacuating to 700-750 mmHg, closing the vacuum pump valve and the mercury gauge valve, filling with helium at a pressure of 0.2 MPa, opening the exhaust valve, exhausting to normal pressure, and closing the exhaust valve; repeating the above operation multiple times; Step (7) in the production stage is specifically as follows: after the second BCl3 feeding is completed, the helium flow rate is adjusted to 1.5-2.5 L / min and the purge is performed for 6-10 hours.

5. The production method according to claim 2, characterized in that: In the production stage, 7.5 kg of sodium borohydride and 100 L of diethylene glycol dimethyl ether were used; 3.34 kg of BCl3 was fed for the first time, and 4.46 kg of BCl3 was fed for the second time; after the purification stage, the purity of the diborane was 99.9999%.

6. The production method according to claim 1, characterized in that: The distillation comprises the following steps: (1) Leakage test of distillation tower and busbar; (2) replacing the distillation tower and the bus with high-purity helium; (3) Refrigeration: Make the alcohol temperature in the tower kettle insulation tank reach -70°C, then supply liquid nitrogen from the upper kettle to make the temperature of the upper kettle lower than that of the lower kettle, and check whether the distillation tower has any leakage at low temperature; (4) Feeding: Open the valve of the tower top outlet, close the fine-tuning valve and the busbar valve, and after evacuating the system, supply diborane from the feed port in the middle of the tower column. Observe the pressure indicator in the tower, and control the pressure of the tower bottom and tower head to be less than 0.5 MPa by controlling the supply rate of liquid nitrogen and diborane. (5) Full reflux: control the tower bottom temperature to -75℃~-65℃, the pressure to below 0.5MPa, the tower head temperature to -155℃~-135℃, the pressure to below 0.5MPa, and reflux for 12 hours; (6) Heading: The product bus is evacuated to the fine-tuning valve, and the fine-tuning valve is adjusted to allow the gas phase in the tower to slowly enter the bus. The flow rate is controlled at 250-350 ml / min. When the pressure of the bus and the sample bottle is close to the pressure in the tower, the methane and chloroform content is sampled and analyzed. The remaining gas is collected into an aluminum bottle frozen by liquid nitrogen. The fine-tuning valve is closed, and the system is flushed with helium. The sample bottle is removed and the fine-tuning valve is opened again to continue heading. When the pressure in the tower is less than 0.1 MPa, a small amount of helium can be filled in to continue heading. Sampling and analysis are performed every 3-5 hours. As the methane content in the tower decreases, the tower top temperature gradually increases to -110°C~-90°C. When the methane content is analyzed to be less than 100 PPm, the receiving bottle is replaced to receive the finished product. (7) Receiving finished products: The tower head temperature is controlled at -110℃~-90℃ and the pressure is 0.15MPa-0.2MPa to receive the finished products. The methane and chloroform contents are analyzed every 1.5-2.5 hours until the methane content is less than 5PPm and the chloroform content is less than 10PPm. The high-purity diborane is received by changing the bottle.

7. The production method according to claim 6, characterized in that: After the rectification step (7), the method further comprises the step (8) of collecting residual liquid: when the distilled gas component exceeds the limit value, the product is stopped from being received, the residual liquid is collected in a bottle instead, and refrigeration is stopped; when the bottom temperature of the tower reaches -40°C and the pressure is at normal pressure, the residual liquid is no longer collected; After the distillation step (8), the method further comprises the step (9) of treating the distillation tower: flushing the system with high-purity nitrogen, venting the waste gas through alkaline solution, and filling the system with 0.3 MPa high nitrogen after the system is replaced cleanly for later use.

8. An industrial device for producing high-purity diborane, characterized in that: The industrial equipment includes a reactor, a cold trap, a bus, a freezer and a BCl3 feeder, wherein the freezer includes a first freezer and a second freezer; the reactor has inlets for sodium borohydride and a solvent, an inlet for BCl3 and a gas outlet; the reactor is connected to the cold trap and also to a mercury sealing device; the cold trap is connected to the bus; the bus is also respectively connected to the freezer, a vacuum pump, a mercury gauge and a wide-mouthed Dewar flask.

9. High-purity diborane obtained by the production method according to any one of claims 1 to 7.

10. Use of the high-purity diborane according to claim 9 in semiconductor preparation and organic synthesis.

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