Method for synthesizing and purifying electronic-grade diborane

Abstract

The invention discloses a synthesis and purification method of electronic-grade diborane, and relates to the technical field of diborane synthesis, and the synthesis and purification method has the advantages that cation 1-ethyl-3-methylimidazole in ionic liquid has a relatively large volume and a specific spatial configuration; the ionic liquid can be close to reactants sodium borohydride and hydrogen through intermolecular force, meanwhile, the anion bis (trifluoromethanesulfonyl) imide salt has high polarity and can attract reactant molecules with opposite charges, so that the ionic liquid makes full contact with the reactants, sulfolane has high dissolving capacity and can well dissolve sodium borohydride and hydrogen, and the ionic liquid can be separated from the reactants. Sodium borohydride and hydrogen are uniformly distributed in a mixed solvent, the sodium borohydride and hydrogen are efficiently reacted at proper temperature and pressure to generate high-purity diborane under the synergistic effect of the sodium borohydride and the hydrogen, sufficient contact of reactants is ensured by timely stirring in the reaction process, the reaction efficiency and the diborane yield are greatly improved, and the yield of the diborane is increased. And favorable conditions are created for subsequent preparation of electronic-grade diborane.

Description

Technical Field

[0001] The invention relates to the technical field of diborane synthesis, in particular to a method for synthesizing and purifying electronic grade diborane. Background Art

[0002] With the rapid development of the electronics industry, electronic-grade specialty gases are playing an increasingly critical role in high-tech fields such as semiconductor manufacturing and solar cells. As one of the important specialty gases, the demand for electronic-grade diborane is also growing. The chemical properties of electronic-grade diborane are very active. It can react with many elements and compounds. For example, it can react with oxygen to produce boron oxide and water, and react with halogens to produce corresponding boron halides. Diborane can also react with metals to form metal borides. This active chemical property makes electronic-grade diborane have important application value in fields such as semiconductor manufacturing, but it also brings certain challenges to its storage, transportation and use. In today's electronics industry, the purity requirements for diborane are extremely high. High-purity diborane can ensure the stable performance and reliable quality of electronic products. However, the current synthesis and purification technology of diborane faces many challenges.

[0003] The prior art has certain technical defects. First, in the synthesis of diborane, the purity of the starting raw materials is not strictly controlled, resulting in the introduction of impurities, affecting the efficiency of the subsequent reaction and the purity of diborane. At the same time, it is impossible to provide a stable and efficient environment for the reaction, resulting in a low yield of diborane. Secondly, the prior art has a single means for removing impurities in diborane and the effect is limited. It lacks an efficient adsorption material combination, cannot effectively remove large molecular organic matter and unreacted residual substances, and is not accurate in the treatment of acidic impurities, making it difficult to achieve the preparation of high-purity diborane. Furthermore, the prior art is insufficient in the removal of small and medium molecular impurities during the purification process of diborane, resulting in the final purity of the diborane being difficult to meet the electronic grade requirements. For this reason, we propose a method for synthesizing and purifying electronic grade diborane. Summary of the invention

[0004] The object of the present invention is to provide a method for synthesizing and purifying electronic grade diborane.

[0005] In order to solve the problems raised in the above background technology, the present invention provides the following technical solution: a method for synthesizing and purifying electronic grade diborane, the method specifically comprising the following steps:

[0006] Step 1: Select sodium borohydride with a purity of 99.9% as the boron source material, place the sodium borohydride in a drying oven for drying to remove possible moisture, and at the same time, select hydrogen with a purity of 99.99% as the source material, purify the hydrogen to effectively remove impurity gases therein, and then place the treated sodium borohydride and hydrogen in a corrosion-resistant stainless steel reaction container;

[0007] Step 2, preparing a mixed solvent system, wherein the mixed solvent is composed of an ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and cyclopentane, adding the mixed solvent into a reaction vessel to react, wherein sodium borohydride and hydrogen react under the action of the mixed solvent to generate diborane, and during the reaction, mechanical stirring is used for stirring, wherein the stirring device is an electric stirrer with a stirring paddle, and the material of the stirring paddle is corrosion-resistant polytetrafluoroethylene, so as to ensure that the reactants can be fully contacted, thereby promoting efficient reaction, and immediately performing preliminary separation of the product after the reaction is completed, and during the distillation process, the diborane gas after preliminary separation is collected by a collecting device;

[0008] Step 3: preparing an adsorption material, mixing aluminum oxide, silicon oxide and activated carbon, and then calcining the mixed material in a high temperature environment. After the calcination is completed, a composite material with high adsorption performance is formed. Then, the diborane gas after preliminary separation is adsorbed and purified by the adsorption material, so that it can effectively adsorb and remove specific impurities therein, thereby improving the purity of diborane;

[0009] Step 4: passing the diborane gas treated with the adsorption material through a low-temperature cooling device to condense the high-boiling-point impurities, collecting the condensed impurities using a corrosion-resistant stainless steel container, and then chemically treating the impurities, slowly reacting the collected impurities through a sodium hydroxide solution, and then precipitating and filtering the solution after the reaction to separate the solid matter therein;

[0010] Step 5: Use a molecular sieve adsorption column to adsorb and remove small and medium-molecule impurities. Before using the molecular sieve adsorption column, place the molecular sieve adsorption column in a high-temperature oven for activation treatment, thereby significantly improving the adsorption effect and ensuring that small and medium-molecule impurities can be effectively removed. Finally, use a reduced pressure distillation method to further purify diborane to obtain high-purity electronic grade diborane.

[0011] As a further solution of the present invention: in the step 1, the drying temperature of sodium borohydride is between 50°C and 60°C, the drying time is 3h-5h, and the selected hydrogen needs to be purified, and the purification process is to pass the hydrogen through a purification device equipped with molecular sieves and activated carbon.

[0012] As a further scheme of the present invention: in the step 2, in the mixed solvent, the proportion of ionic liquid to the total volume of the mixed solvent is 30%-50%, the proportion of cyclopentane to the total volume of the mixed solvent is 50%-70%, the reaction temperature in the reaction container is controlled between 80°C-120°C, the pressure is controlled between 2atm-4atm, the reaction time is set to 5h-8h, and during the reaction, the stirring speed is controlled at 50r / min-100r / min.

[0013] As a further solution of the present invention: in the step 2, the product is preliminarily separated immediately after the reaction is completed, the separation method adopts the method of atmospheric distillation, the distillation temperature is controlled at 150°C-180°C, the collecting device is a stainless steel container with a sealing cover, and the inner wall of the container is coated with a polytetrafluoroethylene coating to enhance its low temperature resistance and corrosion resistance. This collecting device can ensure that the diborane gas will not be contaminated and lost during the collection process.

[0014] As a further solution of the present invention: in the step three, alumina, silicon oxide and activated carbon are mixed in a mass ratio of 2-3:1:3-5, and after mixing, the calcination temperature is controlled at 700°C-900°C, and the calcination time is 3h-5h.

[0015] As a further solution of the present invention: in the step 4, the temperature of the low-temperature cooling device is strictly controlled at -20°C to -40°C, the collected impurities are chemically treated, the concentration of the sodium hydroxide solution is 2 mol / L-4 mol / L, and the treatment is carried out at normal temperature and pressure. The chemical treatment is carried out in a ventilated environment to prevent the accumulation of generated gas.

[0016] As a further solution of the present invention: in the step five, the pore size of the molecular sieve adsorption column is 0.2 μm-0.5 μm, the temperature of the activation treatment is 200° C.-300° C., and the activation time is 3 h-5 h.

[0017] As a further solution of the present invention: in the step 5, when diborane is further purified by vacuum distillation, the distillation temperature is controlled to be -50°C to -30°C, and the pressure is controlled to be 1Pa-3Pa.

[0018] As a further solution of the present invention: in the step 5, the condensation device adopts a two-stage condensation structure, the first-stage condensation adopts a circulating ethylene glycol aqueous solution for cooling, and the temperature is controlled at -40°C to -30°C. The diborane gas first undergoes the first-stage condensation to condense most of the diborane gas into liquid, and the second-stage condensation adopts liquid nitrogen for cooling, and the temperature is controlled at -196°C to ensure that the remaining trace diborane gas can also be fully condensed and recovered, thereby obtaining high-purity electronic grade diborane.

[0019] By adopting the above technical solution, compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. The present invention ensures the purity of the starting materials by selecting high-purity boron source materials sodium borohydride and hydrogen source materials in the synthesis and purification method of electronic grade diborane, and configures an ionic liquid composed of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and cyclopentane. The cation 1-ethyl-3-methylimidazolium in the ionic liquid has a large volume and a specific spatial configuration, and can be close to the reactants sodium borohydride and hydrogen through intermolecular forces. At the same time, the anion bis(trifluoromethanesulfonyl)imide salt has a strong polarity, which can attract reactant molecules with opposite charges, so that the ionic liquid and the reactants are fully in contact. This structure is effective in the reaction. A special microscopic environment is formed in the system, allowing the reactant molecules to move and interact more freely. In addition, ionic liquids have good thermal stability and can maintain stable physical and chemical properties within a certain temperature range, providing a stable chemical environment for the reaction. Cyclopentane has a high solubility and can dissolve sodium borohydride and hydrogen very well, making them evenly distributed in the mixed solvent. The two work synergistically to promote the efficient reaction of sodium borohydride and hydrogen at a suitable temperature and pressure to generate high-purity diborane. Stirring in time during the reaction ensures that the reactants are fully in contact, greatly improving the reaction efficiency and diborane yield, and creating favorable conditions for the subsequent preparation of electronic-grade diborane.

[0021] 2. The present invention forms a composite material by accurately mixing aluminum oxide, silicon oxide and activated carbon and then calcining them. The aluminum oxide has high hardness and stability and can provide physical support for the adsorption process. The silicon oxide has a rich microporous structure. These micropores can attract some larger molecular impurities and some impurities with specific functional groups in the diborane gas through physical adsorption to increase the adsorption surface area. The activated carbon has a very strong adsorption capacity, and its rich internal pore structure can adsorb a variety of organic and inorganic impurities through van der Waals forces and the like. When the diborane gas passes through the composite material, the impurities such as large molecular organic matter and unreacted sodium borohydride residues therein are synergistically adsorbed by the components in the composite material. Then, the impurities react with sodium hydroxide solution. For the acidic impurities contained, sodium hydroxide can react with them to generate sodium chloride and water, thereby further removing the impurities. Then, the diborane gas treated by the new adsorption material passes through a low-temperature cooling device to condense the high-boiling impurities, thereby realizing the gradual removal of different impurities and providing a strong guarantee for obtaining high-purity diborane.

[0022] 3. The present invention utilizes a molecular sieve adsorption column to adsorb and remove small and medium molecule impurities. The molecular sieve has a specific pore structure and can selectively adsorb small and medium molecule impurities while allowing diborane gas to pass through. The molecular sieve adsorption column is activated before use to further enhance its adsorption capacity, thereby ensuring that small and medium molecule impurities, including some small molecule organic matter and water, can be effectively removed. Then, a vacuum distillation method is used to further purify diborane. During the vacuum distillation process, the pressure is reduced to reduce the boiling point of diborane, making it easier to gasify. At the same time, an efficient condensing device is used to ensure that the diborane gas can be fully condensed and recovered, thereby obtaining high-purity electronic grade diborane. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the method steps in an embodiment of the present invention;

[0024] Figure 2 It is a schematic diagram for comparing the performance of the embodiment and the comparative example in the embodiment of the present invention. DETAILED DESCRIPTION

[0025] The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0026] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] Please see attached Figure 1 -Attached Figure 2 The present invention provides a method for synthesizing and purifying electronic grade diborane, and the method for synthesizing and purifying electronic grade diborane specifically comprises the following steps:

[0028] Step 1: Select sodium borohydride with a purity of 99.9% as the boron source material, place the sodium borohydride in a drying oven for drying to remove possible moisture, and at the same time, select hydrogen with a purity of 99.99% as the source material, purify the hydrogen to effectively remove impurity gases therein, and then place the treated sodium borohydride and hydrogen in a corrosion-resistant stainless steel reaction container;

[0029] Step 2, preparing a mixed solvent system, wherein the mixed solvent is composed of an ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and cyclopentane, adding the mixed solvent into a reaction vessel to react, wherein sodium borohydride and hydrogen react under the action of the mixed solvent to generate diborane, and during the reaction, mechanical stirring is used for stirring, wherein the stirring device is an electric stirrer with a stirring paddle, and the material of the stirring paddle is corrosion-resistant polytetrafluoroethylene, so as to ensure that the reactants can be fully contacted, thereby promoting efficient reaction, and immediately performing preliminary separation of the product after the reaction is completed, and during the distillation process, the diborane gas after preliminary separation is collected by a collecting device;

[0030] Step 3: preparing an adsorption material, mixing aluminum oxide, silicon oxide and activated carbon, and then calcining the mixed material in a high temperature environment. After the calcination is completed, a composite material with high adsorption performance is formed. Then, the diborane gas after preliminary separation is adsorbed and purified by the adsorption material, so that it can effectively adsorb and remove specific impurities therein, thereby improving the purity of diborane;

[0031] Step 4: passing the diborane gas treated with the adsorption material through a low-temperature cooling device to condense the high-boiling-point impurities, collecting the condensed impurities using a corrosion-resistant stainless steel container, and then chemically treating the impurities, slowly reacting the collected impurities through a sodium hydroxide solution, and then precipitating and filtering the solution after the reaction to separate the solid matter therein;

[0032] Step 5: Use a molecular sieve adsorption column to adsorb and remove small and medium-molecule impurities. Before using the molecular sieve adsorption column, place the molecular sieve adsorption column in a high-temperature oven for activation treatment, thereby significantly improving the adsorption effect and ensuring that small and medium-molecule impurities can be effectively removed. Finally, use a reduced pressure distillation method to further purify diborane to obtain high-purity electronic grade diborane.

[0033] In one embodiment of the present invention: in step 1, the drying temperature of sodium borohydride is between 50°C and 60°C, the drying time is 3h-5h, and the selected hydrogen needs to be purified by passing the hydrogen through a purification device equipped with molecular sieves and activated carbon.

[0034] In one embodiment of the present invention: in step 2, in the mixed solvent, the proportion of ionic liquid in the total volume of the mixed solvent is 30%-50%, the proportion of cyclopentane in the total volume of the mixed solvent is 50%-70%, the reaction temperature in the reaction container is controlled between 80°C-120°C, the pressure is controlled between 2atm-4atm, the reaction time is set to 5h-8h, and during the reaction, the stirring speed is controlled at 50r / min-100r / min.

[0035] In one embodiment of the present invention: in step 2, the product is preliminarily separated immediately after the reaction is completed, the separation method adopts the method of atmospheric distillation, the distillation temperature is controlled at 150°C-180°C, the collecting device is a stainless steel container with a sealing cover, and the inner wall of the container is coated with a polytetrafluoroethylene coating to enhance its low temperature resistance and corrosion resistance. This collecting device can ensure that the diborane gas will not be contaminated and lost during the collection process.

[0036] In one embodiment of the present invention: in step three, alumina, silicon oxide and activated carbon are mixed in a mass ratio of 2-3:1:3-5, and after mixing, the calcination temperature is controlled at 700°C-900°C, and the calcination time is 3h-5h.

[0037] In one embodiment of the present invention: in step 4, the temperature of the low-temperature cooling device is strictly controlled at -20°C to -40°C, the collected impurities are chemically treated, the concentration of the sodium hydroxide solution is 2 mol / L-4 mol / L, and the treatment is carried out at room temperature and pressure. The chemical treatment is carried out in a ventilated environment to prevent the accumulation of generated gas.

[0038] In one embodiment of the present invention: in step five, the pore size of the molecular sieve adsorption column is 0.2 μm-0.5 μm, the temperature of the activation treatment is 200° C.-300° C., and the activation time is 3 h-5 h.

[0039] In one embodiment of the present invention: in step 5, when diborane is further purified by vacuum distillation, the distillation temperature is controlled to be -50°C to -30°C, and the pressure is controlled to be 1Pa-3Pa.

[0040] In one embodiment of the present invention: in step five, the condensation device adopts a two-stage condensation structure, the first-stage condensation adopts a circulating ethylene glycol aqueous solution for cooling, and the temperature is controlled at -40°C to -30°C. The diborane gas first undergoes the first-stage condensation to condense most of the diborane gas into liquid, and the second-stage condensation adopts liquid nitrogen for cooling, and the temperature is controlled at -196°C to ensure that the remaining trace diborane gas can also be fully condensed and recovered, thereby obtaining high-purity electronic grade diborane.

[0041] In one embodiment of the present invention: the purification treatment of hydrogen also includes connecting a deoxidizer bed in series after the purification device equipped with molecular sieve and activated carbon, and the deoxidizer bed is filled with a palladium catalyst supported by activated alumina, which is used to deeply remove trace oxygen impurities in the hydrogen, further ensuring the high purity of the hydrogen source, and avoiding oxidation reaction of oxygen impurities with sodium borohydride or diborane in subsequent reactions;

[0042] In one embodiment of the present invention: before mixing alumina, silica and activated carbon, alumina, silica and activated carbon are pretreated respectively, and the pretreatment includes heating at 300°C-500°C for 2h-4h under a vacuum environment to remove moisture and other volatile impurities adsorbed on the surface of the material, improve the activity of the adsorption material, thereby enhancing the adsorption performance of the composite material for specific impurities, and further improving the purification effect of diborane;

[0043] In one embodiment of the present invention: when chemically treating the impurities condensed by the low-temperature cooling device, a small amount of surfactant is added to the sodium hydroxide solution, and the surfactant is sodium dodecylbenzene sulfonate, and the added amount is 0.1%-0.5% of the mass of the sodium hydroxide solution to promote the contact and reaction between the impurities and the sodium hydroxide solution, improve the impurity removal efficiency, and ensure that the purity of the diborane gas is further improved.

[0044] Example 1, please refer to the attached Figure 1 -Attached Figure 2First, sodium borohydride with a purity of 99.9% was selected as a boron source material, and placed in a drying oven at 60°C for 5 hours to remove water. At the same time, hydrogen with a purity of 99.99% was selected as a source material, and passed through a purification device equipped with molecular sieves and activated carbon to remove impurity gases. The treated sodium borohydride and hydrogen were then placed in a corrosion-resistant stainless steel reaction container. Next, a mixed solvent consisting of ionic liquid 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide salt (accounting for 50% of the total volume of the mixed solvent) and cyclopentane (accounting for 50% of the total volume of the mixed solvent) was added to the reaction container. At a temperature of 120°C and a pressure of 4atm, sodium borohydride and hydrogen were reacted for 8 hours to generate diborane. During the reaction, a polytetrafluoroethylene was used to The electric stirrer of the stirring paddle stirs at a speed of 100r / min. Immediately after the reaction, the product is initially separated by atmospheric distillation, the distillation temperature is controlled to be 180°C, and a stainless steel container with a sealed lid and an inner wall coated with polytetrafluoroethylene is used to collect the diborane gas after initial separation. After that, alumina, silicon oxide and activated carbon are mixed in a mass ratio of 3:1:5 and calcined at 900°C for 5h to form a composite material. The composite material is used to adsorb and purify the diborane gas after initial separation to remove specific impurities. Subsequently, the adsorbed and purified diborane gas is passed through a low-temperature cooling device at a temperature of -40°C to condense high-boiling point impurities. After collecting the condensed impurities in a stainless steel container, it is slowly introduced into 4mo under a ventilated environment at room temperature and pressure. l / L sodium hydroxide solution for reaction. After the reaction, the solid matter is precipitated and filtered to separate. The gas is then passed through a molecular sieve adsorption column with a pore size of 0.5μm. The adsorption column is pre-activated at 300℃ for 5h to remove small and medium molecular impurities. Finally, it is further purified by vacuum distillation. The distillation temperature is controlled at -30℃ and the pressure is 3Pa. The condensation device adopts a two-stage condensation structure. The first stage is cooled at -30℃ with a circulating ethylene glycol aqueous solution to condense most of the diborane gas into liquid. The second stage is cooled at -196℃ with liquid nitrogen to ensure that trace diborane gas is also fully condensed and recovered to obtain high-purity electronic grade diborane.

[0045] Example 2, please refer to the attached Figure 1 -Attached Figure 2First, sodium borohydride with a purity of 99.9% was selected as a boron source material, and placed in a drying oven at 50°C for 3 hours to remove water. At the same time, hydrogen with a purity of 99.99% was selected as a source material, and passed through a purification device equipped with molecular sieves and activated carbon to remove impurity gases. The treated sodium borohydride and hydrogen were then placed in a corrosion-resistant stainless steel reaction container. Next, a mixed solvent consisting of ionic liquid 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide salt (accounting for 30% of the total volume of the mixed solvent) and cyclopentane (accounting for 70% of the total volume of the mixed solvent) was added to the reaction container. At a temperature of 80°C and a pressure of 2atm, sodium borohydride and hydrogen were reacted for 5 hours to generate diborane. During the reaction, a polytetrafluoroethylene agitator was used. The electric stirrer with a stirring paddle was stirred at a speed of 50r / min. Immediately after the reaction, the product was initially separated by atmospheric distillation, the distillation temperature was controlled at 150°C, and a stainless steel container with a sealed lid and an inner wall coated with polytetrafluoroethylene was used to collect the diborane gas after initial separation. After that, alumina, silicon oxide and activated carbon were mixed in a mass ratio of 2:1:3 and calcined at 700°C for 3h to form a composite material. The composite material was used to adsorb and purify the diborane gas after initial separation to remove specific impurities. Subsequently, the adsorbed and purified diborane gas was passed through a low-temperature cooling device at a temperature of -20°C to condense high-boiling point impurities. After collecting the condensed impurities in a stainless steel container, it was slowly introduced into 2mo under ventilation at room temperature and pressure. l / L sodium hydroxide solution for reaction. After the reaction, the solid matter is precipitated and filtered to separate. The gas is then passed through a molecular sieve adsorption column with a pore size of 0.2μm. The adsorption column is pre-activated at 200℃ for 3h to remove small and medium molecular impurities. Finally, it is further purified by vacuum distillation. The distillation temperature is controlled at -50℃ and the pressure is 1Pa. The condensation device adopts a two-stage condensation structure. The first stage is cooled at -40℃ with a circulating ethylene glycol aqueous solution to condense most of the diborane gas into liquid. The second stage is cooled at -196℃ with liquid nitrogen to ensure that trace diborane gas is also fully condensed and recovered to obtain high-purity electronic grade diborane.

[0046] Example 3, please refer to the attached Figure 1 -Attached Figure 2First, sodium borohydride with a purity of 99.9% was selected as the boron source material and placed in a drying oven at 55°C for 4 hours. At the same time, hydrogen with a purity of 99.99% was selected as the source material and passed through a purification device equipped with molecular sieves and activated carbon to remove impurity gases. The treated sodium borohydride and hydrogen were then placed in a corrosion-resistant stainless steel reaction container. Next, an ionic liquid 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide salt (accounting for 40% of the total volume of the mixed solvent) and cyclopentane (accounting for 10% of the total volume of the mixed solvent) were prepared. A mixed solvent consisting of 60% by volume of sodium borohydride was added to a reaction vessel, and sodium borohydride and hydrogen were reacted for 6 hours to generate diborane at a temperature of 100° C. and a pressure of 3 atm. During the reaction, an electric stirrer with a polytetrafluoroethylene stirring blade was used to stir at a speed of 80 r / min. After the reaction was completed, the product was initially separated by atmospheric distillation immediately, and the distillation temperature was controlled at 160° C. A stainless steel container with a sealed lid and an inner wall coated with polytetrafluoroethylene was used to collect the initially separated diborane gas. After that, aluminum oxide and silicon oxide were added. The mixture is mixed with activated carbon in a mass ratio of 3:1:4 and calcined at 800°C for 4 hours to form a composite material. The composite material is used to adsorb and purify the diborane gas after preliminary separation to remove specific impurities. Subsequently, the diborane gas after adsorption and purification is passed through a low-temperature cooling device at a temperature of -30 to condense high-boiling point impurities. After the condensed impurities are collected in a stainless steel container, a 3 mol / L sodium hydroxide solution is slowly introduced into the gas under ventilation at room temperature and pressure for reaction. After the reaction is completed, the solid matter is precipitated and filtered to separate the gas. The gas is then passed through a molecular sieve adsorption column with a pore size of 0.4 μm, which is activated at 250°C for 4 hours in advance to remove small and medium molecular impurities. Finally, the gas is further purified by reduced pressure distillation, and the distillation temperature is controlled to be -40°C and the pressure is 2 Pa. The condensation device adopts a two-stage condensation structure. The first stage is cooled at -35°C with a circulating ethylene glycol aqueous solution to condense most of the diborane gas into liquid. The second stage is cooled at -196°C with liquid nitrogen to ensure that trace diborane gas is also fully condensed and recovered to obtain high-purity electronic grade diborane.

[0047] Comparative Example 1, please refer to the attached Figure 1 -Attached Figure 2First, sodium borohydride with a purity of 99.9% was selected as the boron source material, and placed in a drying oven at 60°C for 5 hours to remove water. At the same time, hydrogen with a purity of 99.99% was selected as the source material, and passed through a purification device equipped with molecular sieves and activated carbon to remove impurity gases. The treated sodium borohydride and hydrogen were then placed in a corrosion-resistant stainless steel reaction container. Next, a mixed solvent consisting of organic solvents toluene (accounting for 50% of the total volume of the mixed solvent) and cyclopentane (accounting for 50% of the total volume of the mixed solvent) was added to the reaction container. At a temperature of 120°C and a pressure of 4atm, sodium borohydride and hydrogen were reacted for 8 hours to generate diborane. The reaction process The mixture was stirred at a speed of 100 r / min by an electric stirrer with a polytetrafluoroethylene stirring paddle. After the reaction was completed, the product was initially separated by atmospheric distillation, the distillation temperature was controlled to be 180°C, and a stainless steel container with a sealing cover and an inner wall coated with polytetrafluoroethylene was used to collect the diborane gas after the initial separation. After that, the silica gel was simply treated and the diborane gas after the initial separation was adsorbed and purified by the silica gel to remove specific impurities. Subsequently, the adsorbed and purified diborane gas was passed through a low-temperature cooling device at a temperature of -40°C to condense high-boiling impurities. After the condensed impurities were collected in a stainless steel container, 4mo l / L sodium hydroxide solution for reaction. After the reaction is completed, the solid matter is precipitated and filtered to separate. The gas is then passed through a molecular sieve adsorption column with a pore size of 0.5μm to remove small and medium molecular impurities. Finally, it is further purified by vacuum distillation. The distillation temperature is controlled at -30℃ and the pressure is 3Pa. The condensation device adopts a two-stage condensation structure. The first stage is cooled at -30℃ with a circulating ethylene glycol aqueous solution to condense most of the diborane gas into liquid. The second stage is cooled at -196℃ with liquid nitrogen to ensure that trace diborane gas is also fully condensed and recovered to obtain electronic grade diborane.

[0048] Comparative Example 2, please refer to the attached Figure 1 -Attached Figure 2 , using electronic-grade diborane provided in the patent document entitled “A method and device for synthesizing high-purity electronic-grade diborane” with application publication number “CN111892020A”;

[0049] Start vacuum purification to thoroughly purify the diborane purifier and related pipelines. Inject 6N grade ultrapure hydrogen as vacuum replacement gas during vacuum purification. After purification, the pressure of the diborane purifier and related pipelines is -29i nHg;

[0050] Open the feeding port of the diaphragm valve of the diborane synthesizer, and the crude diborane gas of the diborane synthesizer enters the "potassium borohydride chemical reaction purifier → sodium hydroxide chemical reaction purifier → 13X molecular sieve adsorption purifier → ultra-low temperature gas-solid separation purifier" in sequence, and the purification rate of diborane is controlled at 25-100 g / h;

[0051] ① The crude diborane gas enters the potassium borohydride chemical reaction purifier from the bottom, and flows out from the top after contacting and reacting with potassium borohydride (chemically pure, 99.9%). The potassium borohydride chemical reaction purifier controls the reaction temperature of the purifier at 20-40°C through circulating water heat exchange. The purifier can convert a small amount of boron trifluoride in the crude diborane gas into diborane;

[0052] ② The gas from the potassium borohydride chemical reaction purifier enters the sodium hydroxide chemical reaction purifier from the bottom, and flows out from the top after contacting and reacting with sodium hydroxide (chemically pure, 99.8%, anhydrous). The sodium hydroxide chemical reaction purifier controls the reaction temperature of the purifier at 15-30° C. through circulating water heat exchange. The purifier can absorb trace amounts of boron trifluoride and acidic gas impurities by reaction;

[0053] ③ The gas coming out of the sodium hydroxide chemical reaction purifier enters the 13X molecular sieve adsorption purifier from the bottom. The 13X molecular sieve adsorption purifier controls the reaction temperature of the purifier at -40℃~-20℃ through the working fluid (water + ethylene glycol) circulation heat exchange. The purifier can remove high boiling point (boiling point greater than -20℃) impurities and carbon dioxide;

[0054] ④ The gas coming out of the 13X molecular sieve adsorption purifier enters the bottom of the ultra-low temperature gas-solid separation purifier. The ultra-low temperature gas-solid separation purifier is immersed in liquid argon at a temperature of -186°C. Diborane condenses on the inner wall of the gas-solid separation purifier in the form of a solid. Impurities such as hydrogen and trace nitrogen can be discharged from the ultra-low temperature gas-solid separation purifier through the vacuum system. After the separation and purification, the pressure of the ultra-low temperature gas-solid separation purifier is -29i nHg. The solid diborane is sealed in the ultra-low temperature gas-solid separation purifier and taken out by gasification of the solid diborane when needed.

[0055] Experimental design

[0056] Experimental materials and equipment:

[0057] Raw materials: sodium borohydride (purity 99.9%), hydrogen (purity 99.99%), ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, sulfolane, alumina, silicon oxide, activated carbon, sodium hydroxide, molecular sieves (different specifications), silica gel, toluene, potassium borohydride (chemically pure, 99.9%), sodium hydroxide (99.8%, anhydrous), etc.

[0058] Equipment: drying oven, purification device (equipped with molecular sieve and activated carbon), stainless steel reaction vessel, electric stirrer (with polytetrafluoroethylene stirring paddle), atmospheric distillation device, high temperature oven, calcination equipment, low temperature cooling device, vacuum distillation device, two-stage condensation device (first-stage circulating ethylene glycol aqueous solution cooling, second-stage liquid nitrogen cooling), vacuum pump, various temperature and pressure monitoring instruments, gas chromatograph (for detecting the purity and impurity content of diborane), etc.;

[0059] Experimental steps:

[0060] According to the methods of Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2, the synthesis and purification of diborane were respectively performed, each group of experiments was repeated 3 times, and the average value was taken as the final result;

[0061] (I) Calculation of reaction efficiency

[0062] First, the theoretical yield of diborane under a given amount of raw materials is calculated according to the chemical reaction equation. For the reaction of sodium borohydride and hydrogen to generate diborane, the stoichiometric relationship is:

[0063] 2NaBH4+2H2→B2H6+2NaH+3H2

[0064] According to the amount of sodium borohydride input, the mass of diborane that should be generated theoretically is calculated according to the stoichiometric ratio (assuming that the mass of sodium borohydride input is mNaBH4, then the theoretical yield is Where MB2H6 is the molar mass of diborane, MNaBH4 is the molar mass of sodium borohydride), then the mass m of diborane actually collected in the experiment 实际 Divide by the theoretical yield and multiply by 100% to get the reaction efficiency.

[0065] (II) Determination and calculation of diborane purity

[0066] The diborane sample was analyzed by gas chromatography to obtain the diborane peak area AB2H6 and the sum of all impurity peak areas ∑A 杂质 The formula for calculating the purity of diborane is: Diborane purity (%) = (AB2H6 / (AB2H6+∑A 杂质 ))×100%;

[0067] As attached Figure 2 As shown, Example 1 is superior to Example 2, Example 3, Comparative Example 1 and Comparative Example 2 in terms of reaction efficiency and obtaining high-purity diborane, which proves that the process of Example 1 has significant advantages.

[0068] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0069] Although the present invention is disclosed as above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for synthesizing and purifying electronic grade diborane, characterized in that: The synthesis and purification method specifically comprises the following steps: Step 1: Select sodium borohydride with a purity of 99.9% as a boron source material, place the sodium borohydride in a drying oven for drying, and at the same time, select hydrogen with a purity of 99.99% as a source material, purify the hydrogen, and then place the treated sodium borohydride and hydrogen in a stainless steel reaction container; Step 2, preparing a mixed solvent system, wherein the mixed solvent is composed of an ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and cyclopentane, adding the mixed solvent into a reaction vessel to react, and during the reaction, mechanical stirring is used for stirring, and the stirring device is an electric stirrer with a stirring paddle, and the material of the stirring paddle is corrosion-resistant polytetrafluoroethylene, and the product is preliminarily separated immediately after the reaction is completed, and during the distillation process, the diborane gas after the preliminarily separation is collected by a collecting device; Step 3: preparing an adsorption material, mixing aluminum oxide, silicon oxide and activated carbon, and then calcining the mixed material in a high temperature environment to form a composite material with high adsorption performance. Then, the diborane gas after preliminary separation is adsorbed and purified by the adsorption material; Step 4: passing the diborane gas treated with the adsorption material through a low-temperature cooling device to condense high-boiling-point impurities, collecting the condensed impurities, and chemically treating the impurities after collection. The collected impurities are slowly reacted through a sodium hydroxide solution, and after the reaction is completed, the solution is precipitated and filtered to separate the solid matter therein; Step 5: Use a molecular sieve adsorption column to adsorb and remove small and medium molecular impurities. Before using the molecular sieve adsorption column, place the molecular sieve adsorption column in a high-temperature oven for activation treatment. Finally, use a reduced pressure distillation method to further purify diborane to obtain high-purity electronic grade diborane.

2. The method for synthesizing and purifying electronic grade diborane according to claim 1, characterized in that: In the step 1, the drying temperature of sodium borohydride is between 50° C. and 60° C., and the drying time is 3 h to 5 h. The selected hydrogen needs to be purified by passing the hydrogen through a purification device equipped with molecular sieves and activated carbon.

3. The method for synthesizing and purifying electronic grade diborane according to claim 1, characterized in that: In the step 2, in the mixed solvent, the proportion of the ionic liquid to the total volume of the mixed solvent is 30%-50%, the proportion of cyclopentane to the total volume of the mixed solvent is 50%-70%, the reaction temperature in the reaction container is controlled between 80°C-120°C, the pressure is controlled between 2atm-4atm, the reaction time is set to 5h-8h, and during the reaction, the stirring speed is controlled at 50r / min-100r / min.

4. The method for synthesizing and purifying electronic grade diborane according to claim 1, characterized in that: In the step 2, the product is initially separated immediately after the reaction is completed. The separation method adopts the atmospheric distillation method, and the distillation temperature is controlled at 150° C.-180° C. The collecting device is a stainless steel container with a sealing cover, and the inner wall of the container is coated with a polytetrafluoroethylene coating.

5. The method for synthesizing and purifying electronic grade diborane according to claim 1, characterized in that: In the step three, alumina, silicon oxide and activated carbon are mixed in a mass ratio of 2-3:1:3-5. After mixing, the calcination temperature is controlled at 700° C.-900° C. and the calcination time is 3 h-5 h.

6. The method for synthesizing and purifying electronic grade diborane according to claim 1, characterized in that: In the step 4, the temperature of the low-temperature cooling device is strictly controlled at -20°C to -40°C, and the collected impurities are chemically treated. The concentration of the sodium hydroxide solution is 2mol / L-4mol / L, and the treatment is carried out at room temperature and pressure. The chemical treatment is carried out in a ventilated environment to prevent the accumulation of generated gases.

7. The method for synthesizing and purifying electronic grade diborane according to claim 1, characterized in that: In the step 5, the pore size of the molecular sieve adsorption column is 0.2 μm-0.5 μm, the activation treatment temperature is 200° C.-300° C., and the activation time is 3 h-5 h.

8. The method for synthesizing and purifying electronic grade diborane according to claim 1, characterized in that: In the step 5, when diborane is further purified by vacuum distillation, the distillation temperature is controlled to be -50°C to -30°C, and the pressure is controlled to be 1Pa-3Pa.

9. The method for synthesizing and purifying electronic grade diborane according to claim 1, characterized in that: In step 5, the condensation device adopts a two-stage condensation structure, the first-stage condensation is cooled by circulating ethylene glycol aqueous solution, and the temperature is controlled at -40°C to -30°C. The diborane gas first undergoes the first-stage condensation, and the second-stage condensation is cooled by liquid nitrogen, and the temperature is controlled at -196°C.

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