Preparation method of high-purity trimethyl boron

Abstract

The invention relates to the technical field of trimethyl boron preparation, in particular to a high-purity trimethyl boron preparation method which comprises the following steps: S1, reaction raw material preparation: magnesium powder and methane chloride react to generate methylmagnesium chloride; reacting boron trifluoride with aluminum trichloride to generate boron trichloride; s2, taking methyl magnesium chloride and boron trichloride as raw materials, and carrying out dry reaction under the conditions that the pressure is 0-1.0 MPa and the temperature is 40-150 DEG C to generate crude trimethyl boron and magnesium chloride; s3, the crude trimethyl boron is subjected to condensation, adsorption and two-stage rectification in sequence, and a high-purity trimethyl boron product is obtained; and S4, magnesium chloride is electrolyzed to obtain magnesium powder and chlorine, and the magnesium powder and the chlorine are recycled. Compared with the prior art, the method has the advantages that the trimethyl boron is prepared by adopting the dry reaction, the reaction is more sufficient, the reaction efficiency is high, the crude trimethyl boron product is purified, the product purity is improved, in addition, the byproduct magnesium chloride can be recycled, and the resource waste is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of trimethylboron preparation, and in particular to a method for preparing high-purity trimethylboron. Background Art

[0002] Trimethylboron is one of the important raw materials for high-end manufacturing industry. It is often used in the electronics industry for P-type doping of semiconductor devices and silicon thin-film solar cells. Compared with diborane, trimethylboron has the advantages of good stability, low toxicity and less pollution.

[0003] At present, the main synthesis method of trimethylboron includes the reaction of methyl Grignard reagent with boron trifluoride or boron trichloride to generate trimethylboron. For example, the patent application with publication number CN102584874A provides a method for preparing trimethylboron, and the specific steps are to add the ether solution of methyl halide to the ether solution of magnesium powder and boron trifluoride under the protection of dry inert gas, and after the addition is completed, the trimethylboron gas is collected in a dry ice cold trap after being kept warm at 65-75°C for 2-3 hours, and then vacuum distilled into a steel cylinder frozen with liquid nitrogen to obtain trimethylboron. The application adopts a one-step method to prepare trimethylboron, which is simpler in process and shorter in reaction time than the traditional two-step method. However, the crude trimethylboron yield prepared by this method is low, only 44% to 87%, which means that a large amount of raw materials will fail to be effectively converted into the target product during the preparation process, resulting in waste of resources and rising production costs.

[0004] In addition, the patent of publication number CN115055135A provides a preparation system of trimethyl boron, and the step of preparing trimethyl boron using the system includes that the mixed solution consisting of methyl halide and hydrofluoric acid is reacted three times with magnesium through three reactors successively to obtain Grignard reagent (i.e. methyl halogenated magnesium), and Grignard reagent and boron trichloride are mixed and reacted simultaneously in a splitter to obtain product trimethyl boron and product magnesium halide (i.e. magnesium bromide or magnesium chloride). The system is provided with a liquid separator, and the filter hole thereon can block the crystal of product magnesium halide (magnesium chloride or magnesium bromide), and can play the role of filtering product magnesium halide (magnesium chloride or magnesium bromide) crystal, so the conversion rate of the whole reaction can be improved. However, the method does not purify and post-process the product trimethyl boron, and does not recycle the by-product magnesium halide produced thereto, causing a waste of resources.

[0005] Therefore, there is an urgent need to study and improve the existing trimethylboron preparation method in order to provide a trimethylboron preparation method that can not only make the prepared trimethylboron have higher purity but also realize the recycling of the by-product magnesium halide to meet the raw material needs of high-end manufacturing industry. Summary of the invention

[0006] In order to solve the technical problem of low purity of trimethylboron prepared in the prior art, the present invention provides a method for preparing high-purity trimethylboron, which can not only improve the purity of the trimethylboron product but also realize the recycling of the by-product magnesium chloride, thereby reducing resource waste.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing high-purity trimethylboron comprises the following steps:

[0009] Step S1. Preparation of reaction materials: magnesium powder and methyl chloride react to produce methyl magnesium chloride; boron trifluoride and aluminum trichloride react to produce boron trichloride;

[0010] Step S2. Using methyl magnesium chloride and boron trichloride as raw materials, a dry reaction is carried out at a pressure of 0 to 1.0 MPa and a temperature of 40 to 150° C. to produce crude trimethyl boron and magnesium chloride;

[0011] Step S3: The crude trimethylboron is sequentially subjected to condensation, adsorption and two-stage distillation to obtain a high-purity trimethylboron product.

[0012] Preferably, the reaction conditions for the reaction of magnesium powder and methyl chloride to generate methyl magnesium chloride in step S1 are: the molar ratio of magnesium powder to methyl chloride is 1:1 to 1:1.2, the reaction pressure is 0 to 1.0 MPa, and the reaction temperature is 20 to 200°C.

[0013] Preferably, the reaction conditions for the reaction of boron trifluoride and aluminum trichloride to generate boron trichloride in step S1 are: the molar ratio of aluminum trichloride to boron trifluoride is 1:1 to 1:1.2, the reaction pressure is 0 to 1.0 MPa, and the reaction temperature is 20 to 200°C.

[0014] Preferably, in step S2, the molar ratio of methylmagnesium chloride to boron trichloride is 3:1 to 3:2, and the dry reaction time is 4 to 24 hours.

[0015] Preferably, the condensation in S3 refers to passing the crude trimethylborane into a condenser for condensation and dehydration, and the condensation and dehydration temperature in the condenser is -100°C to -60°C, and the collection temperature of the condenser is -180°C to -130°C.

[0016] Preferably, in step S3, 5A grade molecular sieve is selected as the adsorbent, and the filling density of the adsorbent is 0.2-2 g / mL.

[0017] Preferably, the two-stage distillation in step S3 includes a primary distillation and a secondary distillation; the pressure of the primary distillation is 0.5MPa to 2.0MPa, and the temperature is -40°C to 20°C; the pressure of the secondary distillation is 0.2MPa to 1.5MPa, and the temperature is -60 to 10°C.

[0018] Preferably, the method further comprises step S4. magnesium chloride is electrolyzed to obtain magnesium powder and chlorine gas, the magnesium powder is recovered for preparing methylmagnesium chloride as a reaction raw material, the chlorine gas is recovered for reacting with aluminum to prepare aluminum trichloride, or the chlorine gas is harmlessly treated.

[0019] Based on the above technical solutions, the present invention has the following beneficial effects:

[0020] (1) The present invention adopts dry reaction to prepare trimethylboron. In the dry reaction, methylmagnesium chloride and boron trichloride exist in gaseous form and can be mixed more fully. Compared with liquid or solid reactants, gaseous reactants have higher diffusion rate and better fluidity, and can be more evenly distributed in the reaction area. It is conducive to sufficient contact and collision between reactants, thereby improving reaction efficiency. In addition, dry reaction usually does not need to use solvent, avoids the solvent volatilization into the product, and causes certain difficulties for subsequent separation, and can reduce environmental pollution problems caused by solvent volatilization, discharge, etc.

[0021] (2) The crude trimethyl boron obtained by the dry reaction of the present invention is sequentially subjected to condensation, adsorption and two-stage distillation steps to remove different impurities in the crude product, thereby improving the purity of the trimethyl boron product.

[0022] (3) The present invention can recycle the by-product magnesium chloride obtained by the dry reaction. The magnesium chloride is subjected to molten electrolysis to prepare magnesium and chlorine. The magnesium can be returned to step S1 for continued use. The chlorine will not pollute the environment after being harmlessly treated. Alternatively, the chlorine can react with aluminum to generate aluminum trichloride and continue to participate in the reaction.

[0023] In summary, the method of the present invention is used to prepare trimethylboron, not only the product purity is high, but also the by-product can be recycled, thus reducing resource waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a process flow chart for preparing high-purity trimethylboron of the present application. DETAILED DESCRIPTION

[0025] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined application purpose, the following is combined with the attached Figure 1 And the preferred embodiments are clearly and completely described.

[0026] Example 1

[0027] This embodiment provides a method for preparing high-purity trimethylborane, which is as follows:

[0028] Step S1. Preparation of reaction raw materials

[0029] Preparation of methyl magnesium chloride: magnesium powder and methyl chloride are added into a reactor at a molar ratio of 1:1.15, and the pressure in the reactor is controlled at 0.5-0.8 MPa and the temperature is 100-120°C to react and generate methyl magnesium chloride.

[0030] Preparation of boron trichloride: Add aluminum trichloride and boron trifluoride in a molar ratio of 1:1 into a reactor, control the pressure in the reactor to 0.5-0.7 MPa and the temperature to 100-120°C, and react to generate boron trichloride.

[0031] Step S2. The methylmagnesium chloride and boron trichloride prepared in step S1 are added into a reactor in a molar ratio of 3:1.5, mixed thoroughly, and then heated to 100-120° C. and pressurized to 0.5-0.7 MPa for dry reaction to generate magnesium chloride and crude trimethylboron. The reaction time is 20 hours.

[0032] Step S3. The crude trimethyl boron collected in step S2 is passed through a condenser to remove water from the crude trimethyl boron. The condensation and dehydration temperature in the condenser is -80 to -70°C, and the collection temperature of the condenser is -150 to -140°C; the dehydrated crude trimethyl boron is then passed through an adsorption tower to remove impurities such as carbon dioxide, dimethylethyl boron, methyldiethyl boron, and triethyl boron from the crude product. The adsorption tower is filled with a 5A molecular sieve with a filling density of 1 g / ml; the gas then enters a light removal tower for primary distillation to remove hydrogen, oxygen, nitrogen, and one Light components such as carbon dioxide, methane, etc., the pressure in the tower is 1~1.5MPa, the temperature of the lower space of the light removal distillation tower is -30~-20℃, the light components are extracted from the top of the light removal tower, and other components enter the bottom of the light removal tower, and then enter the heavy removal tower for secondary distillation to remove heavy components such as dimethyl ethyl boron, triethyl boron, boron trichloride, etc. The pressure in the tower is 1~1.2MPa, the temperature of the lower space of the heavy removal distillation tower is -30~-20℃, the heavy components enter the bottom of the tower, and the fine trimethyl boron is extracted from the heavy removal tower and enters the fine storage tank.

[0033] Step S4. The magnesium chloride in step S2 is collected and electrolyzed to obtain magnesium powder and chlorine gas. The magnesium powder is recovered for preparing methylmagnesium chloride as a reaction raw material. The chlorine gas can be recovered for reacting with aluminum to prepare aluminum trichloride, or the chlorine gas can be passed into a sodium hydroxide solution for harmless treatment.

[0034] Embodiments 2 to 4

[0035] The operation steps of Examples 2 to 4 are the same as those of Example 1, and the difference lies in that some parameters are different, as shown in Tables 1 and 2.

[0036] Table 1

[0037]

[0038]

[0039] Table 2

[0040]

[0041] Performance Testing

[0042] The purity of the high-purity trimethylborane prepared in Examples 1 to 4 and the yield of the product were tested. The results are shown in Table 3.

[0043] Table 3

[0044] Example purity Yield Example 1 99.99996％ 86.23％ Example 2 99.99993％ 82.76％ Example 3 99.99995％ 85.38％ Example 4 99.99991％ 80.96％

[0045] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing high-purity trimethylboron, characterized in that: The steps include: Step S1. Preparation of reaction materials: magnesium powder and methyl chloride react to produce methyl magnesium chloride; boron trifluoride and aluminum trichloride react to produce boron trichloride; Step S2. Using methyl magnesium chloride and boron trichloride as raw materials, a dry reaction is carried out at a pressure of 0 to 1.0 MPa and a temperature of 40 to 150° C. to produce crude trimethyl boron and magnesium chloride; Step S3: The crude trimethylboron is sequentially subjected to condensation, adsorption and two-stage distillation to obtain a high-purity trimethylboron product.

2. The method for preparing high-purity trimethylboron according to claim 1, characterized in that: The reaction conditions for the reaction of magnesium powder and methyl chloride to generate methyl magnesium chloride in step S1 are: the molar ratio of magnesium powder to methyl chloride is 1:1 to 1:1.2, the reaction pressure is 0 to 1.0 MPa, and the reaction temperature is 20 to 200°C.

3. The method for preparing high-purity trimethyl boron according to claim 1, characterized in that: The reaction conditions for the reaction of boron trifluoride and aluminum trichloride to generate boron trichloride in step S1 are: the molar ratio of aluminum trichloride to boron trifluoride is 1:1 to 1:1.2, the reaction pressure is 0 to 1.0 MPa, and the reaction temperature is 20 to 200°C.

4. The method for preparing high-purity trimethylboron according to claim 1, characterized in that: In step S2, the molar ratio of methylmagnesium chloride to boron trichloride is 3:1 to 3:2, and the dry reaction time is 4 to 24 hours.

5. The method for preparing high-purity trimethyl boron according to claim 1, characterized in that: The condensation in S3 refers to passing the crude trimethylborane into a condenser for condensation and water removal, and the condensation and water removal temperature in the condenser is -100°C to -60°C, and the collection temperature of the condenser is -180°C to -130°C.

6. The method for preparing high-purity trimethylboron according to claim 1, characterized in that: In the step S3, 5A grade molecular sieve is selected as the adsorbent, and the filling density of the adsorbent is 0.2-2 g / mL.

7. The method for preparing high-purity trimethylboron according to claim 1, characterized in that: The two-stage distillation in step S3 includes a primary distillation and a secondary distillation; the pressure of the primary distillation is 0.5MPa to 2.0MPa, and the temperature is -40°C to 20°C; the pressure of the secondary distillation is 0.2MPa to 1.5MPa, and the temperature is -60°C to 10°C.

8. The method for preparing high-purity trimethylboron according to claim 1, characterized in that: The method further comprises step S4. magnesium chloride is electrolyzed to obtain magnesium powder and chlorine gas, the magnesium powder is recovered for preparing methylmagnesium chloride as a reaction raw material, the chlorine gas is recovered for reacting with aluminum to prepare aluminum trichloride, or the chlorine gas is harmlessly treated.

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