Process and system for preparing diborane

Abstract

The invention provides a method for preparing diborane. The method comprises the following steps: in an inert atmosphere, taking halogenated hydrocarbon as raw material gas, carrying out first-step reaction on the halogenated hydrocarbon and hydroboron dissolved in an ether solvent to generate an intermediate, and then dropwise adding organic acid, and carrying out second-step reaction on the organic acid and the obtained intermediate to generate diborane gas. The invention also provides a diborane preparation system used in the method. According to the method and the system, halogenated hydrocarbon, hydroboron and organic acid are used as raw materials, diborane is prepared through two-step reaction, gas-liquid reaction and liquid-liquid reaction are carried out step by step, gas-solid reaction is avoided, the reaction rate is high, and consumed time is short; meanwhile, the raw material halogenated hydrocarbon does not react with the ether solvent, the halogenated hydrocarbon and the ether solvent do not react to generate byproducts, impurities generated in the reaction process are hydrocarbon and hydrogen which are easy to separate, later-stage diborane purification is facilitated, separation and purification are simple, the cost is low, and the obtained diborane product is high in yield and purity.

Description

Technical Field

[0001] The invention belongs to the technical field of clean and energy-saving coal gasification, and in particular relates to a method and a system for preparing diborane. Background Art

[0002] Diborane (B2H6) is chemically active, highly toxic, unstable at room temperature, and slowly decomposes into higher boranes and hydrogen. Diborane is used as a gaseous impurity source in the electronics industry, mainly as a dopant in the production of P-type semiconductor chips, and is widely used in solar photovoltaic, semiconductor and other industries. There are many existing methods for synthesizing diborane. Among them, the most typical method for preparing diborane is to react metal hydrides / borohydrides with boron halides, such as: ① sodium hydride / sodium borohydride reacts with boron trifluoride in an ether solvent. This method is a gas-solid reaction with a slow reaction rate and a long time consumption. In addition, the produced diborane contains impurities such as ethane, ether, and fluorine compounds that are difficult to separate, making subsequent purification difficult; ② sodium borohydride reacts with boron trichloride in an ether solvent such as diethylene glycol dimethyl ether. The reaction can be divided into two steps: the first step: 7NaBH4+3BCl3=4NaB2H7+3NaCl, the second step: 6NaB2H7+2BCl3=7B2H6+6NaCl. In this method, the raw material boron trichloride reacts with the ether solvent to produce impurities such as ethane and carbon dioxide, and carbon dioxide, ethane and diborane have similar boiling points and are difficult to separate; in addition, excessive boron trichloride will also lead to a reduced yield of diborane.

[0003] At present, there are no relevant reports that can solve the problems existing in the prior art of preparing diborane products, such as slow gas-solid reaction rate, high content of impurities that are difficult to separate, and great difficulty in purification. Summary of the invention

[0004] The first object of the present invention is to provide a method for preparing diborane. The method uses halogenated hydrocarbons, borohydrides and organic acids as raw materials to prepare diborane in two steps. The method can solve the problems of slow gas-solid reaction rate, high content of impurities that are difficult to separate, and great difficulty in purification when preparing diborane in the prior art. The method is simple, has low preparation cost and simple purification.

[0005] The second object of the present invention is to provide a system for preparing diborane using the above method, which has a simple structure and is easy to control.

[0006] To achieve the first object of the present invention, the following technical solutions are adopted:

[0007] A method for preparing diborane comprises: in an inert atmosphere, firstly using halogenated hydrocarbon as raw material gas to react with borohydride dissolved in an ether solvent to generate an intermediate, and then dropping an organic acid to react with the intermediate to generate diborane gas.

[0008] The method for preparing diborane according to the present invention, preferably, the method comprises:

[0009] (1) Under an inert atmosphere, first, a halogenated hydrocarbon is used as a raw material gas to react with a borohydride dissolved in an ether solvent in a reaction kettle to generate an intermediate in a first-step reaction, wherein the unreacted raw material gas and the ether solvent are condensed into a condensate and returned to the reaction kettle for continuous reaction;

[0010] (2) An organic acid is dropped into the reaction kettle to react with the obtained intermediate in a second-step reaction to generate diborane gas, obtaining a mixed gas containing diborane gas; the mixed gas containing diborane gas is condensed to separate out a condensate containing the raw material gas and the ether solvent, obtaining a crude diborane gas product;

[0011] (3) The obtained crude diborane gas product is subjected to a first-stage freezing to further separate and remove the condensate containing the raw material gas and the ether solvent, and gaseous diborane is output;

[0012] (4) The obtained gaseous diborane is subjected to a second-stage freezing to separate out non-condensable gas containing CH4 and H2, obtaining liquid diborane as a diborane product.

[0013] The method for preparing diborane according to the present invention, preferably, the halogenated hydrocarbon includes methyl chloride and / or methyl bromide; and / or,

[0014] the ether solvent includes any one or a combination of more than one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and polyethylene glycol dimethyl ether; and / or,

[0015] the borohydride includes any one or a combination of more than one of sodium borohydride, potassium borohydride, and lithium borohydride; and / or,

[0016] the organic acid includes dichloroacetic acid and / or fluoboric acid; and / or,

[0017] the inert atmosphere includes any one or a combination of more than one of nitrogen, argon, and helium.

[0018] The method for preparing diborane according to the present invention, preferably, in the first-step reaction, the reaction temperature is 0 to 20 °C, and / or the feeding flow rate of the halogenated hydrocarbon is 0.5 to 2 g / min, and / or after the feeding of the halogenated hydrocarbon is completed, the reaction continues for 0.5 to 1 h, and / or the molar ratio of the borohydride to the halogenated hydrocarbon is 2:(1 to 1.5).

[0019] The method for preparing diborane according to the present invention, preferably, in the second-step reaction, the reaction temperature is 30 to 45 °C, and / or the dropping flow rate of the organic acid is 3 to 10 ml / min, and / or after the dropping of the organic acid is completed, the reaction continues for 0.5 to 1 h, and / or the molar ratio of the borohydride to the organic acid is 1:(0.3 to 0.7).

[0020] In the method for preparing diborane of the present invention, preferably, the ether solvent is pretreated before being used to dissolve the borohydride; preferably, the pretreatment comprises: heating and vacuum distilling the ether solvent in sequence to remove water and alcohol substances therein; preferably, the heating temperature is 80-100°C.

[0021] The method for preparing diborane of the present invention preferably comprises:

[0022] In step (1), the condensation temperature is -35 to -50°C; and / or,

[0023] In step (2), the condensation temperature is -40 to -60°C; and / or,

[0024] In step (3), the first stage freezing temperature is -80 to -100°C; and / or,

[0025] In step (4), the second stage freezing temperature is -130 to -170°C.

[0026] To achieve the second object of the present invention, a system for preparing diborane used in the above method is provided.

[0027] The system of the present invention, preferably, comprises a production unit;

[0028] The production unit includes an electronic scale, a raw material gas cylinder, an inert gas cylinder, a liquid tank, a condenser and a reaction kettle connected by pipelines; wherein,

[0029] The liquid tank, the reaction kettle and the condenser are connected in sequence through pipelines;

[0030] The raw gas cylinder contains raw gas;

[0031] The inert gas cylinder is provided with inert gas;

[0032] The liquid tank contains organic acid, and is provided with an air inlet at the top and a liquid discharge port at the bottom. The air inlet is connected to the inert gas bottle and is used to introduce inert gas into the liquid tank so that the organic acid therein is pressurized and then discharged from the liquid discharge port.

[0033] The reactor is added with an ether solvent and a borohydride to obtain a borohydride dissolved in an ether solvent, and is provided with an air inlet, a liquid inlet and an air outlet on the top thereof; the air inlet is connected to the raw gas cylinder for introducing the raw gas to react with the borohydride therein in the first step to generate an intermediate, the liquid inlet is connected to the liquid discharge port of the liquid tank for dripping an organic acid to react with the intermediate therein in the second step to generate diborane gas, and the air outlet is used to discharge the mixed gas therein;

[0034] The feed inlet of the condenser is connected to the gas outlet of the reactor, which is used to condense the mixed gas from the reactor, separate the condensate containing the raw material gas and the ether solvent, and output the crude diborane product gas;

[0035] The reactor is equipped with a temperature controller for controlling the temperature of the materials therein;

[0036] The gas inlet of the reactor is also connected to the inert gas cylinder, which is used to introduce inert gas as a purge gas to displace the air or mixed gas therein;

[0037] The raw material gas cylinder is placed on the electronic scale, which is used to weigh and record the feed amount of the raw material gas by the electronic scale;

[0038] The condenser is equipped with a first refrigeration device for controlling the temperature of the condenser.

[0039] In the system of the present invention, preferably, the system further includes a purification unit and a vacuum pump, and the production unit, the purification unit and the vacuum pump are sequentially connected through pipelines;

[0040] The purification unit includes a first collection tank and a second collection tank connected in sequence, and the feed inlet of the first collection tank is connected to the discharge outlet of the condenser; wherein,

[0041] The outside of the first collection tank is equipped with a cooling jacket and a second refrigeration device connected to its cooling jacket, which is used to collect and freeze the crude diborane product gas from the condenser, further separate and remove the condensate containing the raw material gas and the ether solvent, and output gaseous diborane;

[0042] The outside of the second collection tank is equipped with a cooling jacket and a third refrigeration device connected to its cooling jacket, which is used to collect and freeze the gaseous diborane from the first collection tank, discharge the non-condensable gas containing CH4 and H2, and obtain liquid diborane;

[0043] The vacuum pump is connected to the gas outlet of the second collection tank for pumping out the non-condensable gas therein.

[0044] The present invention also provides a method for preparing diborane using the aforementioned system, and the method includes:.

[0045] (1) Add an ether solvent and a borohydride into the reaction kettle respectively, and stir for 2 - 3 h to dissolve the borohydride. Under an inert atmosphere, first turn on the temperature controller and the first refrigeration device respectively. After the reaction kettle reaches the reaction temperature of the first step reaction and the condenser reaches the condensation temperature, introduce a halogenated hydrocarbon from the raw material gas cylinder into the reaction kettle as the raw material gas, so that it reacts with the borohydride dissolved in the ether solvent to generate an intermediate in the first step reaction; and condense the unreacted raw material gas and the ether solvent into a condensate and return it to the reaction kettle for continuous reaction;

[0046] (2) Adjust the temperature controller (7) and the first refrigeration device (8) respectively. After the reaction kettle (6) reaches the reaction temperature of the second step reaction and the condenser (5) reaches the condensation temperature, drop an organic acid from the liquid tank (4) into the reaction kettle (6), so that it reacts with the obtained intermediate in the second step reaction to generate diborane gas, and make the obtained mixed gas containing diborane gas be condensed to separate out a condensate containing the raw material gas and the ether solvent, and obtain a crude diborane gas product;

[0047] (3) Turn on the second refrigeration device (10). After the first collection tank (9) reaches the first - stage freezing temperature, input the obtained crude diborane gas product into the first collection tank (9) for first - stage freezing until the pressure in the first collection tank (9) no longer changes, and further separate and remove the condensate containing the raw material gas and the ether solvent to obtain gaseous diborane;

[0048] (4) Turn on the third refrigeration device. After the second collection tank reaches the second - stage freezing temperature, input the obtained gaseous diborane into the second collection tank for second - stage freezing until the pressure in the second collection tank no longer changes, and separate out the non - condensable gas containing CH4 and H2 therein to obtain liquid diborane as the diborane product;

[0049] (5) Turn on the vacuum pump to evacuate the second collection tank and discharge the non - condensable gas from the second collection tank.

[0050] The beneficial effects of the present invention are as follows:

[0051] The method for preparing diborane of the present invention uses a halogenated hydrocarbon, a borohydride and an organic acid as raw materials, and prepares diborane through two - step reactions. The gas - liquid reaction and the liquid - liquid reaction are carried out step by step, avoiding the gas - solid reaction, and can solve the problem of slow gas - solid reaction rate existing in the prior art for preparing diborane; at the same time, the raw material halogenated hydrocarbon does not react with the ether solvent, avoiding the reaction between the raw material and the solvent to generate by - products, and the impurities generated during the reaction are hydrocarbons and hydrogen which are easy to separate, which is beneficial to the later purification of diborane. The separation and purification are simple and the cost is low, and it can solve the problems of high content of difficult - to - separate impurities and great purification difficulty existing in the prior art for preparing diborane;

[0052] The system for preparing diborane for the aforementioned method according to the present invention has a simple structure and is convenient to control. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a schematic structural diagram of the system for preparing diborane according to the present invention in one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0054] The technical solutions and their effects of the present invention will be further described below in conjunction with specific embodiments / examples. The following embodiments / examples are only used to illustrate the content of the present invention, and the invention is not limited to the following embodiments or examples. Simple changes made to the present invention using the concept of the present invention are within the scope of protection of the present invention.

[0055] A method for preparing diborane includes: under an inert atmosphere, first using a halogenated hydrocarbon as a raw material gas to react with a borohydride dissolved in an ether solvent in a first step to form an intermediate, and then dropping an organic acid to react with the obtained intermediate in a second step to form diborane gas.

[0056] In the present invention, the preparation of diborane is divided into two-step reactions: First, the halogenated hydrocarbon reacts with the borohydride to form an intermediate, and the reaction formula is as follows: RX (halogenated hydrocarbon) + 2MBH4 (borohydride) = RH + MX + MB2H7 (intermediate); then, the intermediate reacts with the organic acid to form diborane gas, and the reaction formula is as follows: MB2H7 (intermediate) + H + (organic acid) = B2H6 (diborane) + M + + H2.

[0057] In the present invention, using a halogenated hydrocarbon, a borohydride and an organic acid as raw materials, diborane is prepared through two-step reactions, and the gas-liquid reaction and liquid-liquid reaction are carried out step by step, avoiding the gas-solid reaction, and can solve the problem of slow gas-solid reaction rate existing in the prior art for preparing diborane; moreover, the raw material halogenated hydrocarbon does not react with the ether solvent, avoiding the reaction of the raw material with the solvent to generate by-products, and the impurities generated during the reaction are hydrocarbons and hydrogen that are easy to separate, which is beneficial to the purification of diborane in the later stage, and the separation and purification are simple and the cost is low.

[0058] In one embodiment, the method includes:

[0059] (1) Under an inert atmosphere, first using a halogenated hydrocarbon as a raw material gas to react with a borohydride dissolved in an ether solvent in a reaction kettle in a first step to form an intermediate, wherein the unreacted raw material gas and the ether solvent are condensed into condensate and returned to the reaction kettle to continue the reaction;

[0060] (2) Drop an organic acid into the reaction kettle, and let it undergo a second-step reaction with the obtained intermediate to generate diborane gas, obtaining a mixed gas containing diborane gas; the mixed gas containing diborane gas is condensed to separate a condensate containing the raw material gas and the ether solvent, obtaining a crude diborane gas product;

[0061] (3) Subject the obtained crude diborane gas product to a first-stage freezing to further separate and remove the condensate containing the raw material gas and the ether solvent, and output gaseous diborane;

[0062] (4) Subject the obtained gaseous diborane to a second-stage freezing to separate non-condensable gas containing CH4 and H2, obtaining liquid diborane as the diborane product.

[0063] In the present invention, the raw material halogenated hydrocarbon does not react with the ether solvent, avoiding the reaction between the raw material and the solvent to generate by-products, and the impurities generated during the reaction process are hydrocarbons and hydrogen that are easy to separate. The separation of relevant impurities can be achieved only through condensation and freezing, which is beneficial to the purification of diborane in the later stage. The separation and purification are simple and the cost is low.

[0064] In one embodiment, the halogenated hydrocarbon includes methyl chloride and / or methyl bromide, such as methyl chloride.

[0065] In one embodiment, the ether solvent includes any one or a combination of more than one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and polyethylene glycol dimethyl ether.

[0066] In one embodiment, the borohydride includes any one or a combination of more than one of sodium borohydride, potassium borohydride, and lithium borohydride, such as potassium borohydride.

[0067] In one embodiment, the organic acid includes dichloroacetic acid and / or fluoboric acid.

[0068] In one embodiment, the inert atmosphere includes any one or a combination of more than one of nitrogen, argon, and helium.

[0069] In the present invention, in the first-step reaction, too high or too low reaction temperature is not conducive to the formation of the intermediate. In one embodiment, in the first-step reaction, the reaction temperature is 0 to 20 °C, such as 2 °C, 4 °C, 5 °C, 6 °C, 8 °C, 10 °C, 12 °C, 14 °C, 15 °C, 16 °C, and 18 °C.

[0070] In the present invention, in the first-step reaction, if the feeding flow rate of the halogenated hydrocarbon is too fast, it will cause waste of the raw material gas and increase the subsequent separation burden; if it is too slow, it will affect the reaction efficiency and thus affect the preparation of diborane. In one embodiment, in the first-step reaction, the feeding flow rate of the halogenated hydrocarbon is 0.5-2 g / min, such as 0.6 g / min, 0.8 g / min, 1 g / min, 1.2 g / min, 1.4 g / min, 1.5 g / min, 1.6 g / min and 1.8 g / min.

[0071] In the present invention, in the first-step reaction, if the reaction time is too short, the reaction is likely to be incomplete, the yield of the intermediate is small, and it will affect the preparation of diborane; if the reaction time is too long, it will affect the reaction efficiency and thus affect the preparation of diborane. In one embodiment, in the first-step reaction, after the feeding of the halogenated hydrocarbon is completed, the reaction continues for 0.5-1 h, such as 0.6 h, 0.7 h, 0.8 h and 0.9 h.

[0072] In the present invention, in the first-step reaction, when the molar ratio of the borohydride to the halogenated hydrocarbon is too large, the borohydride cannot react completely, resulting in waste of raw materials and small yield of the intermediate, which affects the preparation of diborane; when the molar ratio of the borohydride to the halogenated hydrocarbon is too small, the halogenated hydrocarbon cannot react completely, resulting in waste of the raw material gas and increasing the subsequent separation burden. In one embodiment, in the first-step reaction, the molar ratio of the borohydride to the halogenated hydrocarbon is 2:(1-1.5), such as 2:1.1, 2:1.2, 2:1.3 and 2:1.4.

[0073] In the present invention, in the second-step reaction, too high or too low reaction temperature is not conducive to the formation of diborane. In one embodiment, in the second-step reaction, the reaction temperature is 30-45 °C, such as 32 °C, 34 °C, 35 °C, 36 °C, 38 °C, 40 °C, 42 °C and 44 °C.

[0074] In the present invention, in the second-step reaction, if the dropping flow rate of the organic acid is too fast, it will cause waste of the raw material gas and increase the subsequent separation burden; if it is too slow, it will affect the reaction efficiency and thus affect the preparation of diborane. In one embodiment, in the second-step reaction, the dropping flow rate of the organic acid is 3-10 ml / min, such as 4 ml / min, 5 ml / min, 6 ml / min, 7 ml / min, 8 ml / min and 9 ml / min.

[0075] In the present invention, in the second-step reaction, if the reaction time is too short, the reaction is likely to be incomplete and the yield of diborane is small; if the reaction time is too long, it will affect the reaction efficiency and thus affect the preparation of diborane. In one embodiment, in the second-step reaction, after the dropping of the organic acid is completed, the reaction continues for 0.5-1 h, such as 0.6 h, 0.7 h, 0.8 h and 0.9 h.

[0076] In the present invention, in the second-step reaction, when the molar ratio of the borohydride to the organic acid is too large, the intermediate cannot react completely, resulting in waste of raw materials and low production of diborane; when the molar ratio of the borohydride to the organic acid is too small, the organic acid cannot react completely, resulting in waste of the organic acid and increasing the subsequent separation burden. In one embodiment, in the second-step reaction, the molar ratio of the borohydride to the organic acid is 1:(0.3 - 0.7), such as 1:0.4, 1:0.5, and 1:0.6.

[0077] Those skilled in the art understand that ether solvents will contain water and alcohol substances. If not treated, it will have an adverse impact on the subsequent reaction process. In one embodiment, before the ether solvent is used to dissolve the borohydride, it is first pretreated; preferably, the pretreatment includes: heating and vacuum distilling the ether solvent in sequence to remove the water and alcohol substances therein; preferably, the heating temperature is 80 - 100 °C, such as 85 °C, 90 °C, and 95 °C.

[0078] In one embodiment, the dissolution of the borohydride in the ether solvent is carried out under stirring, preferably stirring for 2 - 3 h, such as 2.5 h.

[0079] Those skilled in the art understand that in order to improve the efficiency of the first-step reaction, in one embodiment, in step (1), the condensation temperature is -35 - -50 °C, such as -35 °C, -40 °C, -45 °C, and -50 °C, so as to condense the unreacted raw material gas and the ether solvent into condensate and return it to the reaction kettle for continuous reaction.

[0080] In the mixed gas containing diborane gas obtained in step (2), in addition to containing diborane gas, it also carries impurities such as unreacted raw material gas, ether solvent, and reaction by-products (such as CH4 and H2). In order to improve the purity of the obtained diborane product, in one embodiment, in step (2), the condensation temperature is -40 - -60 °C, such as -40 °C, -45 °C, -50 °C, -55 °C, and -60 °C, so as to condense the raw material gas and the ether solvent therein into condensate for separation.

[0081] In order to improve the purity of the obtained diborane product, in one embodiment, in step (3), the first-stage freezing temperature is -80 - -100 °C, such as -80 °C, -85 °C, -90 °C, -95 °C, and -100 °C, so as to freeze the raw material gas and the ether solvent therein into condensate for further separation and removal.

[0082] In order to improve the purity of the obtained diborane product, in one embodiment, in step (4), the second-stage freezing temperature is -130 to -170 °C, such as -130 °C, -135 °C, -140 °C, -145 °C, -150 °C, -155 °C, -160 °C, -165 °C, and -170 °C, so as to freeze the gaseous diborane therein into condensate for collection, and CH4 and H2 therein are separated and discharged as non-condensable gases.

[0083] Those skilled in the art understand that the inert atmosphere is achieved by replacing the air in the preparation system with an inert gas, and it is preferably replaced more than 3 times, such as 4 times or 5 times.

[0084] The method for preparing diborane according to the present invention uses a halogenated hydrocarbon, a borohydride, and an organic acid as raw materials, and prepares diborane through two-step reactions, with gas-liquid reactions and liquid-liquid reactions carried out step by step, avoiding gas-solid reactions, and can solve the problem of slow gas-solid reaction rate existing in the prior art when preparing diborane; at the same time, the raw material halogenated hydrocarbon does not react with the ether solvent, avoiding the generation of by-products from the reaction of the raw material with the solvent, and the impurities generated during the reaction are hydrocarbons and hydrogen that are easy to separate, which is beneficial to the later purification of diborane, with simple separation and purification and low cost, and can solve the problems of high content of difficult-to-separate impurities and large purification difficulty existing in the prior art when preparing diborane.

[0085] The present invention also provides a system for preparing diborane for the aforementioned method.

[0086] In one embodiment, as Figure 1 shown, the system includes a production unit;

[0087] The production unit includes an electronic scale 1, a raw material gas cylinder 2, an inert gas cylinder 3, a liquid tank 4, a condenser 5, and a reaction kettle 6 connected by pipelines; among them,

[0088] The liquid tank 4, the reaction kettle 6, and the condenser 5 are sequentially connected by pipelines;

[0089] The raw material gas cylinder 2 is equipped with raw material gas;

[0090] The inert gas cylinder 3 is equipped with inert gas;

[0091] The liquid tank 4 is equipped with an organic acid, and an air inlet is provided at the top and a liquid discharge port is provided at the bottom. Its air inlet is connected to the inert gas cylinder 3 for introducing inert gas into the liquid tank 4 so that the organic acid therein is pressurized and discharged from its liquid discharge port;

[0092] An ether solvent and a borohydride are added into the reactor 6 to obtain a borohydride dissolved in the ether solvent. An air inlet, a liquid inlet, and an air outlet are respectively arranged at the top thereof. The air inlet is connected to the raw material gas cylinder 2 to introduce a raw material gas to react with the borohydride therein to generate an intermediate in the first step. The liquid inlet is connected to the drain outlet of the liquid tank 4 to drip an organic acid to react with the intermediate therein to generate diborane gas in the second step. The air outlet is used to discharge the mixed gas therein. Those skilled in the art understand that the mixed gas includes the mixed gas of the unreacted raw material and the ether solvent in the first step, and the mixed gas containing diborane gas obtained in the second step.

[0093] The feed inlet of the condenser 5 is connected to the air outlet of the reactor 6, and is used for condensing the mixed gas from the reactor 6, separating out the condensate containing the raw material gas and the ether solvent, and outputting the crude diborane product gas.

[0094] The reactor 6 is equipped with a temperature controller 7 for controlling the temperature of the materials therein.

[0095] The air inlet of the reactor 6 is further connected to the inert gas cylinder 3, and is used for introducing an inert gas as a purge gas to displace the air or the mixed gas containing diborane gas therein.

[0096] The raw material gas cylinder 2 is arranged on the electronic scale 1, and is used for weighing and recording the feed amount of the raw material gas by using the electronic scale 1.

[0097] The condenser 5 is equipped with a first refrigeration device 8 for controlling the temperature of the condenser 5.

[0098] In one embodiment, the system further includes a purification unit and a vacuum pump. The production unit, the purification unit, and the vacuum pump are sequentially connected through pipelines.

[0099] The purification unit includes a first collection tank 9 and a second collection tank 11 connected in sequence, and the feed inlet of the first collection tank 9 is connected to the discharge outlet of the condenser 5. Among them,

[0100] The first collection tank 9 is externally equipped with a cooling jacket and a second refrigeration device 10 connected to its cooling jacket, and is used for collecting and freezing the crude diborane product gas from the condenser 5, further separating and removing the condensate containing the raw material gas and the ether solvent, and outputting gaseous diborane.

[0101] The second collection tank 11 is externally equipped with a cooling jacket and a third refrigeration device 12 connected to its cooling jacket, and is used for collecting and freezing the gaseous diborane from the first collection tank 9, discharging the non-condensable gas containing CH4 and H2, and obtaining liquid diborane.

[0102] The vacuum pump 13 is connected to the gas outlet of the second collection tank 11 for pumping out the non-condensable gas therein.

[0103] The system for preparing diborane for the foregoing method of the present invention has a simple structure and is convenient to control.

[0104] The present invention also provides a method for preparing diborane using the foregoing system, as Figure 1 shown, the method includes:

[0105] (1) Respectively add an ether solvent and a borohydride into the reaction kettle 6, and stir for 2 to 3 hours to dissolve the borohydride; under an inert atmosphere, first respectively turn on the temperature controller 7 and the first refrigeration device 8, and after the reaction kettle 6 reaches the reaction temperature of the first-step reaction and the condenser 5 reaches the condensation temperature, introduce a halogenated hydrocarbon from the raw material gas cylinder 2 into the reaction kettle 6 as a raw material gas, and make it react with the borohydride dissolved in the ether solvent to generate an intermediate in the first-step reaction;

[0106] (2) Respectively adjust the temperature controller 7 and the first refrigeration device 8, and after the reaction kettle 6 reaches the reaction temperature of the second-step reaction and the condenser 5 reaches the condensation temperature, drop an organic acid from the liquid tank 4 into the reaction kettle 6, and make it react with the obtained intermediate in the second-step reaction to generate diborane gas, and make the obtained mixed gas containing diborane gas be condensed to separate out a condensate containing the raw material gas and the ether solvent, and obtain a crude diborane gas product;

[0107] (3) Turn on the second refrigeration device 10, and after the first collection tank 9 reaches the first-stage freezing temperature, input the obtained crude diborane gas product into the first collection tank 9 for first-stage freezing until the pressure in the first collection tank 9 no longer changes, and further separate and remove the condensate containing the raw material gas and the ether gas to obtain gaseous diborane;

[0108] (4) Turn on the third refrigeration device 12, and after the second collection tank 11 reaches the second-stage freezing temperature, input the obtained gaseous diborane into the second collection tank 11 for second-stage freezing until the pressure in the second collection tank 11 no longer changes, separate out the non-condensable gas of CH4 and H2 therein, and obtain liquid diborane as the diborane product;

[0109] (5) Turn on the vacuum pump 13, evacuate the second collection tank 11, and discharge the non-condensable gas from the second collection tank 11.

[0110] In one embodiment, as Figure 1As shown, the method includes: in step (1), before the ether solvent is used to dissolve borohydride, it is pre-treated; preferably, the pre-treatment includes: heating and vacuum distilling the ether solvent in sequence to remove water and alcohol substances (such as methanol) therein; preferably, the heating temperature is 80-100 °C, such as 85 °C, 90 °C and 95 °C.

[0111] In one embodiment, as Figure 1 shown, the method includes:

[0112] After the organic acid is prepared in the liquid tank 4, the system is purged with an inert gas, preferably purged more than 3 times, to achieve the inert atmosphere of step (1).

[0113] The present invention will be further described below through specific examples.

[0114] The raw materials used in the following examples and comparative examples are as follows:

[0115] Polyethylene glycol dimethyl ether, purity ≥ 99 wt%;

[0116] Diethylene glycol dimethyl ether, purity ≥ 99 wt%;

[0117] Triethylene glycol dimethyl ether, purity ≥ 99 wt%;

[0118] Sodium borohydride, purity ≥ 98 wt%;

[0119] Lithium borohydride, purity ≥ 96 wt%;

[0120] Chloromethane, purity ≥ 99 wt%;

[0121] Bromomethane, purity ≥ 99 wt%;

[0122] Fluoroboric acid, purity ≥ 98 wt%;

[0123] Dichloroacetic acid, purity ≥ 99 wt%

[0124] Boron trichloride, purity is 5N;

[0125] Nitrogen, purity is 5N;

[0126] Argon, purity is 5N.

[0127] Example 1 (S1)

[0128] A method for preparing diborane is carried out by using the system as Figure 1 shown, and specifically includes:

[0129] (1) After heating the ether solvent (diethylene glycol dimethyl ether solvent) at 80 °C, vacuum distillation is carried out to remove water and alcohol substances therein, and the pre-treated ether solvent is obtained;

[0130] Add 4 L of the pretreated ether solvent and 90 g of borohydride (lithium borohydride) into the reaction kettle 6 respectively, and stir for 2.5 h to dissolve the borohydride;

[0131] Add the organic acid (dichloroacetic acid) into the liquid tank 4, and purge and replace the whole system 4 times with the inert gas (argon) from the inert gas cylinder 3;

[0132] Under an inert atmosphere, first turn on the temperature controller 7 and the first refrigeration device 8 respectively. After the reaction kettle 6 reaches the reaction temperature of the first step (10 °C) and the condenser 5 reaches the condensation temperature (-40 °C), introduce the halogenated hydrocarbon from the raw material gas cylinder 2 into the reaction kettle 6 as the raw material gas according to the molar ratio of borohydride to halogenated hydrocarbon of 2:1.3, with an introduction flow rate of 1.0 g / min. After the introduction is completed, continue the reaction for 1.0 h to make it react with the borohydride dissolved in the ether solvent to generate an intermediate in the first step reaction; and condense the unreacted raw material gas and the ether solvent into condensate by the condenser 5 and return it to the reaction kettle 6 for continuous reaction;

[0133] (2) Adjust the temperature controller 7 and the first refrigeration device 8 respectively. After the reaction kettle 6 reaches the reaction temperature of the second step (42 °C) and the condenser 5 reaches the condensation temperature (-45 °C), drop the organic acid (dichloroacetic acid) from the liquid tank 4 into the reaction kettle 6 according to the molar ratio of borohydride to organic acid of 1:0.35, with a dropping flow rate of 6 ml / min. After the dropping is completed, continue the reaction for 1 h to make it react with the obtained intermediate in the second step reaction to generate diborane gas, and obtain a mixed gas containing diborane gas; the mixed gas containing diborane gas is condensed by the condenser 5 to separate out the condensate containing the raw material gas and the ether solvent, and obtain the crude diborane gas;

[0134] (3) Turn on the second refrigeration device 10. After the first collection tank 9 reaches the first-stage freezing temperature (-85 °C), input the obtained crude diborane gas into the first collection tank 9 for first-stage freezing until the pressure in the first collection tank 9 no longer changes, and further separate and remove the condensate containing the raw material gas and the ether gas to obtain gaseous diborane;

[0135] (4) Turn on the third refrigeration device 12. After the second collection tank 11 reaches the second-stage freezing temperature (-150 °C), input the obtained gaseous diborane into the second collection tank 11 for second-stage freezing until the pressure in the second collection tank 11 no longer changes, and separate out the non-condensable gas containing CH4 and H2 therein to obtain liquid diborane as the diborane product;

[0136] (5) Turn on the vacuum pump 13 to evacuate the second collection tank 11 and discharge the non-condensable gas from the second collection tank 11.

[0137] Example 2 (S2)

[0138] The diborane is prepared by using the system and method in Example 1, and the difference from Example 1 is that the method includes:

[0139] (1) After heating the ether solvent (polyethylene glycol dimethyl ether solvent) at 90 °C, carry out vacuum distillation to remove the water and alcohol substances therein, and obtain the pretreated ether solvent;

[0140] Add 3 L of the pretreated ether solvent and 80 g of borohydride (sodium borohydride) into the reaction kettle 6 respectively, and stir for 2.5 h to dissolve the borohydride;

[0141] Add the organic acid (fluoboric acid) into the liquid tank 4, and purge and replace the whole system 4 times with the inert gas (nitrogen) from the inert gas cylinder 3;

[0142] Under an inert atmosphere, first turn on the temperature controller 7 and the first refrigeration device 8 respectively. After the reaction kettle 6 reaches the reaction temperature of the first step reaction (18 °C) and the condenser 5 reaches the condensation temperature (-45 °C), introduce the halogenated hydrocarbon from the raw material gas cylinder 2 into the reaction kettle 6 as the raw material gas according to the molar ratio of borohydride to halogenated hydrocarbon of 2:1.4, with the introduction flow rate of 0.7 g / min. After the introduction is completed, continue the reaction for 1.0 h to make it react with the borohydride dissolved in the ether solvent to generate an intermediate in the first step reaction;

[0143] (2) Adjust the temperature controller 7 and the first refrigeration device 8 respectively. After the reaction kettle 6 reaches the reaction temperature of the second step reaction (38 °C) and the condenser 5 reaches the condensation temperature (-50 °C), drop the organic acid (fluoboric acid) from the liquid tank 4 into the reaction kettle 6 according to the molar ratio of borohydride to organic acid of 1:0.65, with the dropping flow rate of 4 ml / min. After the dropping is completed, continue the reaction for 1 h to make it react with the obtained intermediate in the second step reaction to generate diborane gas, and obtain a mixed gas containing diborane gas; the mixed gas containing diborane gas is condensed by the condenser 5 to separate out the condensate containing the raw material gas and the ether solvent, and obtain the crude diborane gas product;

[0144] (3) Turn on the second refrigeration device 10. After the first collection tank 9 reaches the first-stage freezing temperature (-85 °C), input the obtained crude diborane gas product into the first collection tank 9 for the first-stage freezing until the pressure in the first collection tank 9 no longer changes, and separate out the condensate containing the raw material gas and the ether gas to obtain gaseous diborane;

[0145] (4) Turn on the third refrigeration device 12. After the second collection tank 11 reaches the second-stage freezing temperature (-150 °C), input the obtained gaseous diborane into the second collection tank 11 for second-stage freezing until the pressure in the second collection tank 11 no longer changes, and further separate and remove the non-condensable gas containing CH4 and H2 therein to obtain liquid diborane as the diborane product;

[0146] (5) Turn on the vacuum pump 13 to evacuate the second collection tank 11 and discharge the non-condensable gas from the second collection tank 11.

[0147] Example 3 (S3)

[0148] Diborane is prepared using the system and method in Example 1. The difference from Example 1 is that the method includes:

[0149] (1) After heating the ether solvent (triethylene glycol dimethyl ether solvent) to 100 °C, perform vacuum distillation to remove water and alcohol substances therein to obtain a pretreated ether solvent;

[0150] Add 5 L of the pretreated ether solvent and 120 g of borohydride (lithium borohydride) into the reaction kettle 6 respectively, and stir for 2 h to dissolve the borohydride;

[0151] Add the organic acid (dichloroacetic acid) into the liquid tank 4, and purge and replace the entire system 4 times with the inert gas (nitrogen) from the inert gas cylinder 3;

[0152] Under an inert atmosphere, first turn on the temperature controller 7 and the first refrigeration device 8 respectively. After the reaction kettle 6 reaches the reaction temperature of the first-step reaction (15 °C) and the condenser 5 reaches the condensation temperature (-45 °C), input the halogenated hydrocarbon from the raw material gas cylinder 2 into the reaction kettle 6 as the raw material gas according to the molar ratio of borohydride to halogenated hydrocarbon of 2:1.5, with an input flow rate of 1.0 g / min. After the input is completed, continue the reaction for 1.0 h to make it react with the borohydride dissolved in the ether solvent to generate an intermediate in the first-step reaction;

[0153] (2) Adjust the temperature controller 7 and the first refrigeration device 8 respectively. After the reaction kettle 6 reaches the reaction temperature (42 °C) for the second-step reaction and the condenser 5 reaches the condensation temperature (-50 °C), drop the organic acid (dichloroacetic acid) from the liquid tank 4 into the reaction kettle 6 at a molar ratio of borohydride to organic acid of 1:0.35. The dropping flow rate is 6 ml / min. After the dropping is completed, continue the reaction for 1 h to make it undergo the second-step reaction with the obtained intermediate to generate diborane gas, and obtain a mixed gas containing diborane gas; the mixed gas containing diborane gas is condensed by the condenser 5 to separate out a condensate containing raw material gas and ether solvent, and obtain a crude diborane gas product;

[0154] (3) Open the second refrigeration device 10. After the first collection tank 9 reaches the first-stage freezing temperature (-90 °C), input the obtained crude diborane gas product into the first collection tank 9 for first-stage freezing until the pressure in the first collection tank 9 no longer changes, and separate out a condensate containing raw material gas and ether gas to obtain gaseous diborane;

[0155] (4) Open the third refrigeration device 12. After the second collection tank 11 reaches the second-stage freezing temperature (-155 °C), input the obtained gaseous diborane into the second collection tank 11 for second-stage freezing until the pressure in the second collection tank 11 no longer changes, and separate out the non-condensable gas containing CH4 and H2 therein to obtain liquid diborane as the diborane product;

[0156] (5) Open the vacuum pump 13 to evacuate the second collection tank 11 and discharge the non-condensable gas from the second collection tank 11.

[0157] Example 4 (S4)

[0158] Prepare diborane using the system and method in Example 1, and the difference from Example 1 is only that:

[0159] In step (1), the molar ratio of borohydride to halogenated hydrocarbon is 2:1;

[0160] The molar ratio of borohydride to organic acid is 1:0.5;

[0161] The feeding flow rate of the halogenated hydrocarbon is 2 g / min;

[0162] The dropping flow rate of the organic acid is 10 ml / min;

[0163] The condensation temperature for the first-step reaction is -35 °C;

[0164] The condensation temperature for the second-step reaction is -40 °C;

[0165] The first-stage freezing temperature is -80 °C;

[0166] The second-stage freezing temperature is -130 °C.

[0167] Comparative Example 1 (D1)

[0168] Using the existing technology, diborane is prepared by reacting sodium borohydride and boron trichloride in an ether solvent such as diethylene glycol dimethyl ether. The preparation steps are as follows:

[0169] (1) Add 2.5 L of diethylene glycol dimethyl ether solvent and 80 g of sodium borohydride to the reaction kettle, stir to dissolve it, and purge and replace the entire system with nitrogen 4 times; slowly introduce boron trichloride gas into the reaction kettle according to the molar ratio of BCl3 / NaBH4 of 0.14, control the reaction temperature at 18 °C, and react for 1 h after the introduction is completed;

[0170] (2) Raise the temperature of the reaction kettle to 35 °C, slowly introduce boron trichloride gas into the reaction kettle according to the molar ratio of BCl3 / NaBH4 of 0.19, with a flow rate of 1.0 g / min. After the introduction of boron trichloride is completed, continue to react for 1.0 h, and collect the resulting diborane product gas through a -196 °C condensation device.

[0171] Results:

[0172] Analyze the yields, purities, and components of the diborane products obtained in Examples 1-4 and Comparative Example 1. The analysis results are shown in Table 1.

[0173] Table 1 Yields, purities, and components of diborane products

[0174]

[0175] From the comparison between Examples 1-4 and Comparative Example 1 and the data in Table 1, it can be seen that:

[0176] In the preparation process of Comparative Example 1, the yield of the diborane product is low, and the raw materials boron trichloride and ether solvent react to produce impurities such as ethane and carbon dioxide, resulting in high contents of ethane and carbon dioxide that are not easily separated in the obtained diborane product and low purity;

[0177] The method for preparing diborane of the present invention uses a halogenated hydrocarbon, a borohydride, and an organic acid as raw materials, and prepares diborane through two-step reactions, with gas-liquid reactions and liquid-liquid reactions carried out step by step, avoiding gas-solid reactions, having a fast reaction rate and short time consumption; at the same time, the raw material halogenated hydrocarbon does not react with the ether solvent, so no by-products are generated between the two, and the impurities generated during the reaction are hydrocarbons and hydrogen that are easy to separate, which is beneficial to the purification of diborane in the later stage. The separation and purification are simple, the diborane product has a high yield and high purity, and the components of ethane and carbon dioxide that are not easily separated are not detected.

Claims

1. A method for preparing diborane, characterized in that, The method includes: under an inert atmosphere, first using a halogenated hydrocarbon as a feed gas to react with a borohydride dissolved in an ether solvent in a first-step reaction to form an intermediate, and then dropping an organic acid to react with the obtained intermediate in a second-step reaction to form diborane gas.

2. The method according to claim 1, wherein The method includes: (1) Under an inert atmosphere, first using a halogenated hydrocarbon as a feed gas to react with a borohydride dissolved in an ether solvent in a reaction kettle in a first-step reaction to form an intermediate, condensing the unreacted feed gas and the ether solvent into a condensate and returning it to the reaction kettle for continuous reaction; (2) Dropping an organic acid into the reaction kettle to react with the obtained intermediate in a second-step reaction to form diborane gas, obtaining a mixed gas containing diborane gas; the mixed gas containing diborane gas is condensed to separate out a condensate containing the feed gas and the ether solvent, and a crude diborane gas product is output; (3) Subjecting the obtained crude diborane gas product to a first-stage freezing to further separate and remove the condensate containing the feed gas and the ether solvent, and outputting gaseous diborane; (4) Subjecting the obtained gaseous diborane to a second-stage freezing to separate out non-condensable gas containing CH4 and H2, and obtaining liquid diborane as the diborane product.

3. The method according to claim 1 or 2, wherein the halogenated hydrocarbon includes methyl chloride and / or methyl bromide; and / or, the ether solvent includes any one or a combination of more than one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and polyethylene glycol dimethyl ether; and / or the borohydride includes any one or a combination of more than one of sodium borohydride, potassium borohydride, and lithium borohydride; and / or the organic acid includes dichloroacetic acid and / or fluoboric acid; and / or the inert atmosphere includes any one or a combination of more than one of nitrogen, argon, and helium.

4. The method according to any one of claims 1-3, wherein in the first-step reaction, the reaction temperature is 0-20 °C, and / or the feeding flow rate of the halogenated hydrocarbon is 0.5-2 g / min, and / or after the feeding of the halogenated hydrocarbon is completed, the reaction continues for 0.5-1 h, and / or the molar ratio of the borohydride to the halogenated hydrocarbon is 2:(1-1.5).

5. The method according to any one of claims 1-4, wherein in the second-step reaction, the reaction temperature is 30-45 °C, and / or the dropping flow rate of the organic acid is 3-10 ml / min, and / or after the dropping of the organic acid is completed, the reaction continues for 0.5-1 h, and / or the molar ratio of the borohydride to the organic acid is 1:(0.3-0.7).

6. The method according to any one of claims 1-5, characterized in that Before being used to dissolve the borohydride, the ether solvent is first pretreated; preferably, the pretreatment includes: heating and vacuum distilling the ether solvent in sequence to remove water and alcohol substances therein; preferably, the heating temperature is 80-100 °C.

7. The method according to any one of claims 2-6, wherein in step (1), the condensation temperature is -35 to -50 °C; and / or, in step (2), the condensation temperature is -40 to -60; and / or, in step (3), the first-stage freezing temperature is -80 to -100 °C; and / or, in step (4), the second-stage freezing temperature is -130 to -170 °C.

8. A system for preparing diborane for the method according to any one of claims 1 - 7.

9. The system according to claim 8, wherein The system includes a production unit; The production unit includes an electronic scale (1), a raw material gas cylinder (2), an inert gas cylinder (3), a liquid tank (4), a condenser (5) and a reaction kettle (6) connected by pipelines; wherein, The liquid tank (4), the reaction kettle (6) and the condenser (5) are sequentially connected by pipelines; The raw material gas cylinder (2) is equipped with raw material gas; The inert gas cylinder (3) is equipped with inert gas; The liquid tank (4) is equipped with organic acid, and has an air inlet at the top and a liquid discharge port at the bottom. Its air inlet is connected to the inert gas cylinder (3) for introducing inert gas into the liquid tank (4) to pressurize the organic acid therein and discharge it from its liquid discharge port; An ether solvent and a borohydride are added into the reaction kettle (6) to obtain a borohydride dissolved in the ether solvent, and it has an air inlet, a liquid inlet and an air outlet at the top respectively; and its air inlet is connected to the raw material gas cylinder (2) for introducing raw material gas to react with the borohydride therein in a first - step reaction to generate an intermediate, its liquid inlet is connected to the liquid discharge port of the liquid tank (4) for dripping in organic acid to react with the intermediate therein in a second - step reaction to generate diborane gas, and its air outlet is used to discharge the mixed gas therein; The feed inlet of the condenser (5) is connected to the air outlet of the reaction kettle (6) for condensing the mixed gas from the reaction kettle (6), separating out a condensate containing raw material gas and ether solvent, and outputting a crude diborane product gas; The reaction kettle (6) is equipped with a temperature controller (7) for controlling the temperature of the materials therein; The air inlet of the reaction kettle (6) is also connected to the inert gas cylinder (3) for introducing inert gas as a purge gas to displace the air or mixed gas therein; The raw material gas cylinder (2) is arranged on the electronic scale (1) for weighing and recording the feed amount of the raw material gas by the electronic scale (1); The condenser (5) is equipped with a first refrigeration device (8) for controlling the temperature of the condenser (5); Preferably, the system further includes a purification unit and a vacuum pump, and the production unit, the purification unit and the vacuum pump are sequentially connected by pipelines; The purification unit includes a first collection tank (9) and a second collection tank (11) connected in sequence, and the feed inlet of the first collection tank (9) is connected to the discharge outlet of the condenser (5); wherein, The outside of the first collection tank (9) is equipped with a cooling jacket and a second refrigeration device (10) connected to its cooling jacket for collecting and freezing the crude diborane product gas from the condenser (5), further separating and removing the condensate containing raw material gas and ether solvent, and outputting gaseous diborane; The outside of the second collection tank (11) is equipped with a cooling jacket and a third refrigeration device (12) connected to its cooling jacket for collecting and freezing the gaseous diborane from the first collection tank (9), discharging the non - condensable gas containing CH4 and H2, and obtaining liquid diborane; The vacuum pump (13) is connected to the gas outlet of the second collection tank (11) for pumping out the non-condensable gas therein.

10. A method for preparing diborane using the system as described in claim 9, characterized in that, The method includes: (1) Respectively adding an ether solvent and a borohydride into the reaction kettle (6), and stirring for 2 - 3 h to dissolve the borohydride; under an inert atmosphere, first respectively turn on the temperature controller (7) and the first refrigeration device (8), and after the reaction kettle (6) reaches the reaction temperature of the first-step reaction and the condenser (5) reaches the condensation temperature, introducing a halogenated hydrocarbon from the raw material gas cylinder (2) into the reaction kettle (6) as a raw material gas, so that it reacts with the borohydride dissolved in the ether solvent to generate an intermediate in the first-step reaction; and condensing the unreacted raw material gas and the ether solvent into condensate and returning it to the reaction kettle for continuous reaction; (2) Respectively adjusting the temperature controller (7) and the first refrigeration device (8), and after the reaction kettle (6) reaches the reaction temperature of the second-step reaction and the condenser (5) reaches the condensation temperature, dropping an organic acid from the liquid tank (4) into the reaction kettle (6), so that it reacts with the obtained intermediate in the second-step reaction to generate diborane gas, and separating the obtained mixed gas containing diborane gas by condensation to obtain a condensate containing the raw material gas and the ether solvent, thereby obtaining a crude diborane gas product; (3) Turning on the second refrigeration device (10), and after the first collection tank (9) reaches the first-stage freezing temperature, inputting the obtained crude diborane gas product into the first collection tank (9) for first-stage freezing until the pressure in the first collection tank (9) no longer changes, further separating and removing the condensate containing the raw material gas and the ether solvent to obtain gaseous diborane; (4) Turning on the third refrigeration device (12), and after the second collection tank (11) reaches the second-stage freezing temperature, inputting the obtained gaseous diborane into the second collection tank (11) for second-stage freezing until the pressure in the second collection tank (11) no longer changes, separating out the non-condensable gas containing CH4 and H2 therein to obtain liquid diborane as the diborane product; (5) Turning on the vacuum pump (13) to evacuate the second collection tank (11) and discharging the non-condensable gas from the second collection tank (11).

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