Method for preparing diborane

Abstract

According to the method for preparing the diborane provided by the invention, boron trichloride does not need to be fed for multiple times in stages, complicated reaction temperature control is not needed, intermediate control steps in the production process are few, the generation efficiency of the diborane is favorably improved, and the process difficulty is reduced. The method comprises the following steps: reacting boron trichloride with metal hydroboron in the presence of trimethyl borate and an ether solvent to prepare diborane gas; the boron trichloride is fed in a one-step feeding manner.

Description

Technical Field

[0001] The invention relates to a diborane synthesis technology, and in particular to a method for preparing diborane. Background Art

[0002] Diborane (B2H6) is a colorless, flammable, highly toxic gas with a boiling point of -92.5°C and a relative molecular weight of 27.67. It can generate boric acid and hydrogen when in contact with water, and can be decomposed at high temperatures to obtain higher-order boranes and hydrogen. It has a special molecular configuration and is a typical "electron-deficient" compound. Diborane can be used as a gaseous impurity source, a dopant for ion implantation and boron doping oxidation diffusion, and is mainly used as a dopant in the production of P-type semiconductor chips. Therefore, it is widely used in semiconductor integrated circuits, liquid crystal displays, semiconductor light-emitting devices, and solar cells. Diborane is usually diluted with N2, Ar, He, H2 and other gases and used as a mixed gas.

[0003] At present, the synthesis methods of diborane are:

[0004] (1) Preparation of diborane by dry process using boron trifluoride and sodium borohydride Patent application CN111892020A discloses a method for preparing diborane by using boron trifluoride and metal borohydride under solvent-free conditions, which method is prone to low reaction efficiency and incomplete reaction.

[0005] (2) Diborane is prepared by reacting boron trichloride and sodium borohydride in an ether solvent. This method is divided into two steps. The first step is the reaction of sodium borohydride and boron trichloride to generate NaB2H7, which is an exothermic reaction; the second step is the reaction of NaB2H7 and boron trichloride to generate diborane, which is an endothermic reaction. To prepare diborane by this method, boron trichloride needs to be added to the reaction system in stages, and the reaction temperature needs to be controlled in stages. At the same time, the amount of boron trichloride needs to be controlled in stages during the reaction process, otherwise side reactions are likely to occur, resulting in a decrease in yield.

[0006] The above existing technologies have the disadvantages of difficult control of reaction conditions, low efficiency and low yield, which make it difficult to scale up industrial production. Summary of the invention

[0007] The invention provides a method for preparing diborane. When the method is adopted, boron trichloride does not need to be fed multiple times in stages, and complex reaction temperature control is not required. The intermediate control steps in the production process are few, which is beneficial to improving the generation efficiency of diborane and reducing the process difficulty.

[0008] To achieve the purpose, the present invention provides the following technical solutions:

[0009] The present invention provides a method for preparing diborane, which comprises the following steps:

[0010] Boron trichloride and metal borohydride are reacted in the presence of trimethyl borate and an ether solvent to prepare diborane gas; the boron trichloride is fed in a one-step feeding manner.

[0011] Preferably, the ether solvent is selected from one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and polyether;

[0012] Preferably, the molecular weight of the polyether is ≤300, and the polyether may be, for example, polyethylene glycol dimethyl ether.

[0013] In the present invention, the boron trichloride can be a gaseous or liquid raw material.

[0014] In the present invention, the metal borohydride can be selected from one or more borohydrides of sodium, lithium and potassium, specifically, for example, one or more of lithium borohydride, sodium borohydride, potassium borohydride and the like.

[0015] Preferably, the molar ratio of the trimethyl borate to the ether solvent is 0.1-10, for example, 0.1, 0.5, 1, 1.5, 1.8, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, etc. The inventors have found that the preferred molar ratio is conducive to obtaining a better reaction yield.

[0016] Preferably, the molar ratio of boron trichloride to trimethyl borate is 0.3-0.9, for example, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc.; the molar ratio of metal borohydride to boron trichloride is 1-9, for example, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, etc. The inventors have found that the preferred molar ratio is conducive to obtaining a better reaction yield.

[0017] In some embodiments, the trimethyl borate and the ether solvent are stirred and mixed in advance to form a mixed liquid, and then other materials are added;

[0018] In some embodiments, the trimethyl borate and the ether solvent are stirred and mixed at -10°C to 35°C, for example, the stirring and mixing time is 0.1-1h.

[0019] In some embodiments, the boron trichloride is added to the reaction system before the metal borohydride is added; for example, the boron trichloride is added to the reaction system for 0.1-2 hours before the metal borohydride is added. In some embodiments, the addition and reaction of boron trichloride can be carried out at a temperature at which trimethyl borate and an ether solvent are stirred and mixed, for example, at -10°C to 35°C.

[0020] Preferably, the reaction is carried out at a temperature of -30°C to 70°C, such as -30, -20, -10, 0, 10, 20, 30, 40, 50, 60, 70°C, etc., and the pressure is controlled to be -100KPa to 100KPa, such as -100, -90, -80, -70, -60, -50, -30, -10, 0, 10, 20, 50, 100KPa, etc. The inventors have found that the reaction is carried out under preferred conditions to obtain a better reaction yield. In a more preferred embodiment, the reaction is carried out at a temperature of -10°C to 70°C, and the pressure is controlled to be -100KPa to 100KPa. The reaction is carried out under more preferred conditions, which can further significantly improve the reaction yield.

[0021] In some embodiments, boron trichloride can be added at a temperature where trimethyl borate and an ether solvent are stirred and mixed, for example, at -10°C to 35°C. In some embodiments, boron trichloride can be added at a temperature of -30°C to 70°C. In some embodiments, the reaction temperature is controlled at -30°C to 70°C when metal borohydride is added. In some embodiments, the temperature conditions when boron trichloride is added and the temperature conditions when metal borohydride is added can be the same or different.

[0022] In some preferred embodiments, the molar ratio of trimethyl borate to the ether solvent is 0.1-10, the molar ratio of boron trichloride to trimethyl borate is 0.3-0.9, the molar ratio of metal borohydride to boron trichloride is 1-9, and the reaction is carried out at a temperature of -10°C to 70°C, and the pressure is controlled to be -100KPa to 100KPa. The preparation of diborane by this preferred method can obtain a better yield of diborane.

[0023] The boron trichloride of the present invention is fed in one step, which means that the boron trichloride does not need to be fed in multiple stages or in stages under multiple temperature conditions.

[0024] Specifically, the reaction is carried out in a protective gas atmosphere; preferably, the protective gas is selected from one or more of nitrogen, argon, and helium. Specifically, for example, before the reaction is carried out, a protective gas is introduced into the reaction device for purging and replacement, for example, replacement 2-5 times.

[0025] In some embodiments, the diborane gas is collected by a condensing device, and the condensing temperature of the condensing device is preferably controlled to be -100°C to -196°C.

[0026] Preferably, after the reaction is completed, the residual liquid is filtered to remove salt and impurities and then recycled to the reaction system, that is, used as the mixed liquid. In the reaction system of the present invention, the reaction liquid can be reused after treatment, saving production costs.

[0027] The technical solution provided by the present invention has the following beneficial effects:

[0028] In the method of the present invention, diborane is prepared by reacting boron trichloride and metal borohydride in the presence of trimethyl borate and an ether solvent, wherein boron trichloride reacts with trimethyl borate to generate (CH3O)2BCl, and (CH3O)2BCl reacts with metal borohydride to generate diborane. The method of the present invention is used to prepare diborane without multi-stage feeding of boron trichloride, and the process control is simple, which is conducive to reducing the process difficulty.

[0029] The method of the present invention is used to prepare diborane, with fewer intermediate control links, simple material feeding, and no need for complex temperature control procedures. The production efficiency of diborane can be greatly improved, the difficulty of process operation can be reduced, and the production cost can be saved. DETAILED DESCRIPTION

[0030] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0031] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0032] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in the art can be used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be purchased commercially.

[0033] Raw material description: Boron trichloride, industrial grade (purity ≥ 99%); Sodium borohydride, industrial grade 98%; Trimethyl borate, industrial grade ≥ 99%; Solvent, industrial grade purity ≥ 99%; The purity of other gases is 5N.

[0034] Example 1

[0035] 402 g of diethylene glycol dimethyl ether solvent was added to the reaction kettle, and the experimental device was evacuated and purged three times with argon gas with a purity of 99.999%, and then evacuated to -90 kPa;

[0036] Add 309 g of trimethyl borate to the solvent in the reactor, start stirring, set the stirring rate to 60 r / min, the solvent mixing time to 0.5 h, and the temperature to 10 ° C;

[0037] Then, 175.5 g of boron trichloride gas was introduced, and after a reaction time of 0.5 h, 111 g of sodium borohydride was added and the reaction was continued for 2.5 h, and the temperature was controlled at 20°C;

[0038] The diborane gas obtained by the reaction was collected by a -196°C condenser. The collected product was weighed to obtain 51.8 g of diborane, with a yield of 96%.

[0039] Example 2

[0040] 201 g of diethylene glycol dimethyl ether solvent was added to the reaction kettle, and the experimental device was evacuated and purged three times with argon gas with a purity of 99.999%, and then evacuated to -30 kPa;

[0041] Add 309 g of trimethyl borate to the solvent in the reactor, start stirring, set the stirring rate to 65 r / min, the solvent mixing time to 0.6 h, and the temperature to -5 °C;

[0042] Then, 175.5 g of boron trichloride gas was introduced, and after a reaction time of 0.6 h, 111 g of sodium borohydride was added and the reaction was continued for 2.7 h, and the temperature was controlled at 45°C;

[0043] The diborane gas obtained by the reaction was collected by a -196°C condenser. The collected product was weighed to obtain 51.5 g of diborane, with a yield of 95.3%.

[0044] Example 3

[0045] 302.6 g of triethylene glycol dimethyl ether solvent was added into the reaction kettle, and the experimental device was evacuated and purged with argon gas with a purity of 99.999% for 4 times, and then evacuated to 10 kPa;

[0046] Add 329.6 g of trimethyl borate to the solvent in the reactor, start stirring, set the stirring rate to 70 r / min, the solvent mixing time to 0.5 h, and the temperature to 15 °C;

[0047] Then, 117 g of boron trichloride gas was introduced, and after a reaction time of 0.6 h, 111 g of sodium borohydride was added to continue the reaction for 2.5 h, and the temperature was controlled at 20°C;

[0048] The diborane gas obtained by the reaction was collected by a -196°C condenser. The collected product was weighed to obtain 51.3 g of diborane, with a yield of 95%.

[0049] Example 4

[0050] 402 g of diethylene glycol dimethyl ether solvent was added to the reaction kettle, and the experimental device was evacuated and purged with 99.999% pure argon gas for 4 times, and then evacuated to -80 kPa;

[0051] Add 257.5 g of trimethyl borate to the solvent in the reactor, start stirring, set the stirring rate to 70 r / min, the solvent mixing time to 0.5 h, and the temperature to 15 °C;

[0052] Then, 146.3 g of boron trichloride gas was introduced, and after a reaction time of 0.5 h, 103.6 g of sodium borohydride was added to continue the reaction for 3 h, and the temperature was controlled at 30 °C;

[0053] The diborane gas obtained by the reaction was collected by a -196°C condenser. The collected product was weighed to obtain 48.5 g of diborane, with a yield of 96.2%.

[0054] Example 5

[0055] 402 g of diethylene glycol dimethyl ether solvent was added to the reaction kettle, and the experimental device was evacuated and purged with argon gas with a purity of 99.999% for 4 times, and then evacuated to -60 kPa;

[0056] Add 257.5 g of trimethyl borate to the solvent in the reactor, start stirring, set the stirring rate to 65 r / min, the solvent mixing time to 0.5 h, and the temperature to 15 °C;

[0057] Then, 146.3 g of boron trichloride gas was introduced, and after a reaction time of 0.6 h, 124 g of potassium borohydride was added to continue the reaction for 3 h, and the temperature was controlled at 30 °C;

[0058] The diborane gas obtained by the reaction was collected by a -196°C condenser. The collected product was weighed to obtain 39.3 g of diborane, with a yield of 94.9%.

[0059] Comparative Example 1

[0060] 402 g of diethylene glycol dimethyl ether solvent was added to the reaction kettle, and the experimental device was evacuated and purged three times with argon gas with a purity of 99.999%, and then evacuated to -90 kPa;

[0061] Add 20.6 g of trimethyl borate to the solvent in the reactor, start stirring, set the stirring rate to 60 r / min, the solvent mixing time to 0.5 h, and the temperature to 10 °C;

[0062] Then, 5.9 g of boron trichloride gas was introduced, and after a reaction time of 0.5 h, 16.7 g of sodium borohydride was added and the reaction was continued for 2.5 h, and the temperature was controlled at 20°C;

[0063] The diborane gas obtained by the reaction was collected by a -196°C condenser. The collected product was weighed to obtain 6.5 g of diborane, with a yield of 80%.

[0064] The main difference between this comparative example and Examples 1-5 is that the raw materials do not adopt the preferred molar ratio, resulting in a decrease in the yield of diborane.

[0065] Comparative Example 2

[0066] The first step of reaction: add 402g of diethylene glycol dimethyl ether solvent to the reactor, evacuate and purge the experimental device 4 times with argon gas with a purity of 99.999%, evacuate again, and then introduce argon gas with a purity of 99.999% to normal pressure; add 111g of sodium borohydride to the solvent in the reactor, start stirring, set the stirring rate to 50r / min, the stirring time to 0.5h, and at the same time adjust the reactor temperature to 20°C, introduce 38.1g of boron trichloride gas, and after stirring for 1.5h, remove a small amount of impurity gas.

[0067] Second step reaction: adjust the temperature of the reactor to 30°C, introduce 78.9 g of boron trichloride gas, and react for 4 hours to generate diborane.

[0068] The diborane gas obtained by the reaction was collected by a -196°C condensing device, and the collected product was weighed to obtain 44.82 g of diborane with a yield of 83%.

[0069] Compared with the examples, in this comparative example, boron trichloride is fed in stages at different reaction temperatures, which significantly increases the difficulty of process operation and control.

[0070] Comparative Example 3 (Compared with Example 2)

[0071] 201 g of diethylene glycol dimethyl ether solvent was added to the reaction kettle, and the experimental device was evacuated and purged three times with argon gas with a purity of 99.999%, and then evacuated to -30 kPa;

[0072] Add 309 g of trimethyl borate to the solvent in the reactor, start stirring, set the stirring rate to 65 r / min, the solvent mixing time to 0.6 h, and the temperature to -5 °C;

[0073] Then, 175.5 g of boron trichloride gas was introduced, and after a reaction time of 0.6 h, 111 g of sodium borohydride was added to continue the reaction for 5 h, and the temperature was controlled at -20 °C;

[0074] The diborane gas obtained by the reaction was collected by a -196°C condenser. The collected product was weighed to obtain 35.3 g of diborane, with a yield of 65.4%.

[0075] Comparative Example 4 (Compared with Example 2)

[0076] 201 g of diethylene glycol dimethyl ether solvent was added to the reaction kettle, and the experimental device was evacuated and purged three times with 99.999% pure argon gas, and then filled with argon to 200 kPa;

[0077] Add 309 g of trimethyl borate to the solvent in the reactor, start stirring, set the stirring rate to 65 r / min, the solvent mixing time to 0.6 h, and the temperature to -5 °C;

[0078] Then, 175.5 g of boron trichloride gas was introduced, and after a reaction time of 0.6 h, 111 g of sodium borohydride was added and the reaction was continued for 2.7 h, and the temperature was controlled at 45°C;

[0079] The diborane gas obtained by the reaction was collected by a -196°C condenser. The collected product was weighed to obtain 34.1 g of diborane, with a yield of 63.2%.

[0080] It is easy to understand that the above embodiments are only examples for clear explanation and do not mean that the present invention is limited thereto. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the present invention.

Claims

1. A method for preparing diborane, characterized in that: The method comprises the following steps: Boron trichloride and metal borohydride are reacted in the presence of trimethyl borate and an ether solvent to prepare diborane gas; the boron trichloride is fed in a one-step feeding manner.

2. The method according to claim 1, characterized in that The ether solvent is selected from one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and polyether; Preferably, the molecular weight of the polyether is ≤300.

3. The method according to claim 1 or 2, characterized in that: The boron trichloride is a gaseous or liquid raw material; And / or, the metal borohydride is selected from one or more of borohydrides of sodium, lithium and potassium.

4. The method according to any one of claims 1 to 3, characterized in that: The molar ratio of the trimethyl borate to the ether solvent is preferably 0.1-10.

5. The method according to any one of claims 1 to 4, characterized in that: The molar ratio of the boron trichloride to trimethyl borate is preferably 0.3-0.9, and the molar ratio of the metal borohydride to boron trichloride is preferably 1-9.

6. The method according to any one of claims 1 to 5, characterized in that: The trimethyl borate and the ether solvent are stirred and mixed in advance to form a mixed liquid, and then other materials are added; Preferably, the trimethyl borate and the ether solvent are stirred and mixed at -10°C to 35°C, and preferably the stirring and mixing time is 0.1-1h.

7. The method according to claim 6, characterized in that After adding the boron trichloride into the reaction system, the metal borohydride is then added; Preferably, the boron trichloride is added to the reaction system and reacted for 0.1-2 hours before adding the metal borohydride.

8. The method according to any one of claims 1 to 7, characterized in that: The reaction is carried out at a temperature of -30°C to 70°C, and the pressure is controlled to be -100KPa to 100KPa; preferably, the reaction is carried out at a temperature of -10°C to 70°C.

9. The method according to any one of claims 1 to 8, characterized in that: The reaction is carried out in a protective gas atmosphere; preferably, the protective gas is selected from one or more of nitrogen, argon and helium.

10. The method according to any one of claims 1 to 9, characterized in that: The diborane gas is collected by a condensing device, and the condensing temperature of the condensing device is preferably controlled to be -100°C to -196°C; Preferably, after the reaction is completed, the residual liquid is filtered to remove salt and separate impurities and then recycled to the reaction system.