Preparation method for improving conversion rate of aryl silane prepared by reducing aryl chlorosilane

Abstract

The invention discloses a preparation method for improving the conversion rate of aryl silane prepared by reducing aryl chlorosilane. Comprising the following steps: enabling aryl chlorosilane, a reducing agent and a phase transfer catalyst to form a reduction reaction system in an ether solvent; raising the temperature of the reduction reaction system for reaction, and performing reduced pressure distillation to obtain aryl silane; wherein the reducing agent comprises alkali metal hydride, and the phase transfer catalyst comprises alkali metal borohydride. According to the preparation method provided by the invention, the reducing capacity of the alkali metal hydride reducing agent is improved by taking the alkali metal borohydride as a phase transfer catalyst, so that the chemical reaction process of reducing aryl chlorosilane to prepare aryl silane is further improved, and the reaction is carried out towards a complete reaction direction; the content of an intermediate product in a final product, especially the content of aryl chlorosilane, is remarkably reduced, and high-purity aryl silane with extremely low chlorine content can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of organic compounds, and particularly to a preparation method for improving the conversion rate of the reduction of arylchlorosilanes to prepare arylsilanes. Background Art

[0002] Arylsilanes, especially phenylsilane among them, are important organosilicon intermediates, which can be used as reducing agents, raw materials for synthesizing polysilanes, and raw materials for preparing diiodosilane. Diiodosilane is a new type of silicon-based precursor material, suitable for forming silicon-containing thin films by atomic layer deposition (ALD) at a relatively low temperature, and can be used to produce high-end semiconductor chips. Diiodosilane can be prepared by the iodination reaction of elemental iodine and phenylsilane.

[0003] The preparation of diiodosilane requires high-purity phenylsilane, especially phenylsilane without chloride impurities, because these chlorides may contaminate diiodosilane, resulting in an excessive chlorine impurity content in diiodosilane. Chlorine impurities can cause many problems in semiconductor chip manufacturing, including corroding equipment and shortening the service life of chips.

[0004] Phenylsilane is traditionally prepared by reducing phenyltrichlorosilane using metal hydrides. During the reduction process, intermediate products such as phenyldichlorosilane and phenylmonochlorosilane are formed. Under common production conditions, due to the steric hindrance effect of the benzene ring, even when an excessive amount of metal hydride is used, these intermediate products cannot be completely reduced, resulting in a certain amount of phenylchlorosilane impurities in the industrially produced phenylsilane products.

[0005] It is already known in the industry that using LiH to reduce phenyltrichlorosilane cannot achieve complete reduction. To address this problem, US Patent No. 4629801 reported an improved method, using a tertiary amine to improve the reduction efficiency of LiH on phenyltrichlorosilane, which can achieve the effect of improving the degree of the reduction reaction. However, the tertiary amine in this implementation is difficult to prepare, has a strong harm to equipment and personnel, and the implementation method is complex. The introduced tertiary amine affects the purity of the phenylsilane product as an impurity, and the industrial operability is relatively low. There is an urgent need to develop an alternative solution. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a preparation method for improving the conversion rate of the reduction of arylchlorosilanes to prepare arylsilanes.

[0007] To achieve the foregoing invention purpose, the technical solutions adopted by the present invention include:

[0008] In a first aspect, the present invention provides a preparation method for improving the conversion rate of the reduction of arylchlorosilanes to prepare arylsilanes, which includes:

[0009] Form a reduction reaction system of an aromatic chloro - silane, a reducing agent, and a phase - transfer catalyst in an ether solvent;

[0010] After heating the reduction reaction system for reaction, obtain the aromatic silane by vacuum distillation;

[0011] Among them, the reducing agent includes an alkali metal hydride, and the phase - transfer catalyst includes an alkali metal borohydride.

[0012] Based on the above - mentioned technical solution, compared with the prior art, the beneficial effects of the present invention at least include:

[0013] The preparation method provided by the present invention uses an alkali metal borohydride as a phase - transfer catalyst to improve the reduction ability of the alkali metal hydride reducing agent, thereby improving the chemical reaction process of reducing the aromatic chloro - silane to prepare the aromatic silane, so that the reaction proceeds in the direction of complete reaction, significantly reducing the content of intermediate products, especially the content of aromatic monochloro - silane, in the final product, and enabling the acquisition of a high - purity aromatic silane with an extremely low chlorine content.

[0014] The above description is only an overview of the technical solution of the present invention. In order to enable those skilled in the art to more clearly understand the technical means of the present application and to implement it in accordance with the content of the specification, the following takes the preferred embodiments of the present invention as examples for illustration. Detailed Description of the Invention

[0015] In view of the deficiencies in the prior art, the inventors of this case have proposed the technical solution of the present invention through long - term research and a large number of practices. The following will further explain the technical solution, its implementation process, principles, etc.

[0016] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0017] Moreover, relational terms such as "first" and "second" are only used to distinguish one component or method step with the same name from another, and do not necessarily require or imply any such actual relationship or order between these components or method steps.

[0018] The embodiment of the present invention provides a preparation method for improving the conversion rate of reducing an aromatic chloro - silane to prepare an aromatic silane, which includes the following steps:

[0019] Form a reduction reaction system of an aromatic chloro - silane, a reducing agent, and a phase - transfer catalyst in an ether solvent;

[0020] After heating the reduction reaction system for reaction, obtain the aromatic silane by vacuum distillation;

[0021] Among them, the reducing agent includes alkali metal hydrides, and the phase transfer catalyst includes alkali metal borohydrides.

[0022] Common metal hydrides used in the reduction method, including lithium hydride, generally have low solubility due to their low compatibility with solvents. Even under excess conditions, they cannot achieve the due reduction effect, which is the main reason for the formation of impurities in phenylchlorosilane at present. The solution provided by the present invention is to use a metal hydride that has good compatibility with both solvents and lithium hydride, such as alkali metal borohydrides like sodium borohydride, to act as a phase transfer catalyst, improve the solubility and reaction activity of the main reducing agent LiH, so as to improve the reduction effect and the degree of reaction progress, so that when the same amount of metal hydride is used, the effect of significantly reducing the impurities in phenylchlorosilane can be achieved.

[0023] Based on the above scheme, the present invention creatively adds sodium borohydride with a certain mass ratio of lithium hydride, which can improve the conversion rate of aryltrichlorosilane during the reaction and obtain phenylsilane with higher purity. Under the same experimental conditions and with the same experimental equipment in the laboratory, the purity of the obtained arylsilane can reach 99.994%, the proportion of phenylmonochlorosilane is about 0.006%, and the chlorine content in the pure product of phenylsilane is about 15 ppm. The chlorine content is significantly reduced after adding borohydride in the synthesis reaction.

[0024] In the current prior art, related technical solutions such as the technical method of improving the reduction degree of phenyltrichlorosilane by tertiary amines mentioned in the background technology point out that conventional reducing agents such as lithium hydride cannot achieve the technical effect of complete reduction, which is mainly due to the too large steric hindrance effect of the aryl group in the reactants. The present invention finds a catalyst to replace tertiary amines, which not only improves the degree of reaction completion and reduces the chlorine element content, but also achieves the technical goal of improving industrial operability and makes remarkable progress.

[0025] In some related prior arts, for example, in the Chinese invention patent with the publication number CN 108530477 A, a technical solution for reducing chloroalkylchlorosilane by the combination of lithium hydride and sodium borohydride and other catalysts is also mentioned. Although they all involve the reduction of the Si-Cl bond, the specific technical purposes and functions are significantly different from those of the present invention.

[0026] The technical problem solved by this prior art is how to improve the reaction selectivity. The role of the borohydride catalyst added is to reduce the content of lithium hydride to avoid reducing the chlorine atom connected to the alkyl group. The difference between arylchlorosilane and alkylchlorosilane is that the phenyl group has a higher steric hindrance effect than the alkyl group. Therefore, it is more difficult to reduce phenylchlorosilane than alkylchlorosilane. This also causes that in the above prior art, as long as the selectivity is controlled, the chlorine in alkylchlorosilane is easily almost completely reduced. However, in the present invention, due to the steric hindrance effect, it is difficult to achieve complete reduction. That is, the purpose and function of the above prior art is to selectively obtain a specific product in which the chlorosilane is reduced and the alkyl group is not reduced. The present invention does not involve the selectivity problem between alkyl chloride and silicon-based chloride. The main problem lies in the problem that the silicon-based chloride cannot be completely reduced.

[0027] In short, the problems solved in the above related prior art are the reduction reaction rate and the reduction reaction selectivity problems, which belong to the reaction kinetics rate problems. In the present invention, however, it is the problem of the degree of the reduction reaction, which belongs to the reaction thermodynamics equilibrium problem. The two are not the same technical problems. And it is worth noting that the so-called improvement of the reduction ability includes various situations. Promoting the rate of the reduction reaction is one of the kinetic situations, and improving the reducibility of the reducing agent to change the degree of the chemical equilibrium is one of the thermodynamic situations. The two cannot be confused. Improving the reaction rate does not necessarily mean changing the chemical equilibrium. It only means that the equilibrium can be reached quickly.

[0028] More specifically, these prior arts also mention the invention in the background art of the present invention to improve the reduction efficacy of LiH on phenyltrichlorosilane. Therefore, these prior arts recognize the problems that need to be solved in the reduction of phenyltrichlorosilane, but do not point out that their inventions can be used to better solve this problem.

[0029] Secondly, the goal of the present invention is to reduce the content of partially reduced by-products, that is, phenylmonochlorosilane, in the phenylsilane product, rather than selectively reducing alkyl chloride or silicon-based chloride. And in the multiple embodiments involved, it is mentioned that the yield of alkylsilane is 100%. This is sufficient to show that due to the lower steric hindrance effect of its alkyl group, after controlling the selectivity, the reaction progress can naturally reach complete thoroughness. Therefore, the above prior art essentially does not face the technical problem that the reduction of the three chlorine atoms connected to the silicon atom is incomplete. For the arylchlorosilane to be reduced in the present invention, it is impossible to achieve a 100% reduction effect (i.e., the product has a chlorine content of 0 ppm) by using the conventional reduction method. This is the consensus in the industry. The statement of a 100% yield in the above prior art precisely shows that its goal is not to solve the problem of the chlorine content caused by the insufficient reaction progress after the reduction reaction equilibrium in the product.

[0030] In some embodiments, the arylchlorosilane includes any one or a combination of two or more of phenyltrichlorosilane, phenyldichlorosilane, phenylmonochlorosilane, o - tolyltrichlorosilane, m - tolyltrichlorosilane, p - tolyltrichlorosilane, o - tolyldichlorosilane, m - tolyldichlorosilane, p - tolyldichlorosilane, o - tolylmonochlorosilane, m - tolylmonochlorosilane, p - tolylmonochlorosilane, but not limited thereto.

[0031] In some embodiments, the alkali metal hydride includes any one or a combination of two or more of LiH, NaH, KH, LiAlH 4 , NaAlH 4 and KAlH 4 , but not limited thereto.

[0032] In some embodiments, the alkali metal borohydride includes any one or a combination of two or more of NaBH 4 , LiBH 4 and KBH 4 , but not limited thereto.

[0033] In some embodiments, the ether solvent is selected from high - boiling - point ether solvents with a boiling point more than 100 °C higher than that of the arylsilane. Preferably, in some embodiments, it is a high - boiling - point ether solvent with a boiling point more than 150 °C higher;

[0034] In some embodiments, the boiling point of the ether solvent is at least 270 °C.

[0035] In some embodiments, the high - boiling - point ether solvent includes any one or a combination of two or more of tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and diethylene glycol dibutyl ether.

[0036] Based on this, the present invention creatively uses a high - boiling - point solvent, such as tetraethylene glycol dimethyl ether, as the solvent for the reduction reaction. By utilizing the 155 - degree boiling - point difference between the solvent and the arylsilane, a high - purity phenylsilane product can be rapidly separated by vacuum distillation after the reduction reaction is completed.

[0037] In some embodiments, in the reduction reaction system, the molar ratio of the chlorine atoms in the arylchlorosilane to the hydrogen atoms of the reducing agent is (0.5 - 1)∶1;

[0038] In some embodiments, in the reduction reaction system, the content of the phase - transfer catalyst is 1 - 10% of the total mass of the reducing agent;

[0039] In some embodiments, in the reduction reaction system, the mass ratio of the reducing agent to the ether solvent is 1∶(5 - 100).

[0040] In some embodiments, the preparation method specifically includes the following steps:

[0041] Fully mix the reducing agent, phase transfer catalyst, and ether solvent, and then heat to the reaction temperature to form a reaction system;

[0042] Slowly add the arylchlorosilane to the reaction system, control the temperature to be stable, and maintain the reaction temperature after the addition is completed to complete the reduction reaction;

[0043] In some embodiments, the reaction temperature is 80 - 120 °C, and the time for the reduction reaction is 1 - 24 h.

[0044] In some embodiments, it further includes the following steps:

[0045] Maintain the reaction temperature for the vacuum distillation.

[0046] Based on the above embodiments, the purity of the arylsilane obtained in the typical embodiment of the present invention is above 99.99%, the mass ratio of the intermediate arylmonochlorosilane is below 0.01%, and the chlorine content is below 25 ppm.

[0047] The present invention improves the method for reducing phenyltrichlorosilane with metal hydride. Aiming at the low solubility of common metal hydrides, a small amount of highly soluble metal hydride is used to achieve an effect similar to that of a phase transfer catalyst, improving the reduction effect of the main metal hydride, thereby greatly reducing the content of phenylchlorosilane impurities in the phenylsilane product. At the same time, the present invention uses a high-boiling-point ether solvent with a boiling point at least 100 degrees higher than that of phenylsilane, so that high-purity phenylsilane products can be quickly separated by vacuum distillation after the reduction reaction is completed.

[0048] The technical solutions of the present invention are further described in detail below through several examples. However, the selected examples are only used to illustrate the present invention and do not limit the scope of the present invention.

[0049] In the following examples and comparative examples, unless otherwise specified, the compounds, reagents, etc. used are conventional reagents and can be commercially obtained; unless specified, the pressure is normal pressure and normal temperature; and the analytical and testing methods involved include:

[0050] Before purification, take 1 mL of the crude phenylsilane synthesis product, add 10 mL of anhydrous n-hexane to the crude product, filter and take 1 mL of the filtrate sample into a chromatographic glass bottle, suck 0.5 μL of the sample with a syringe, inject the sample for testing and obtain the chromatographic composition of the crude product.

[0051] After purification, take 1 mL of the purified phenylsilane obtained after distillation, suck 0.5 μL of the sample with a syringe, inject the sample for testing and obtain the chromatographic composition of the purified phenylsilane.

[0052] Example 1

[0053] Weigh 38.0 g (4.77 mol) of lithium hydride and 2.0 g (0.053 mol) of sodium borohydride and add them to 638 mL of the solvent tetraethylene glycol dimethyl ether. Replace the atmosphere of the reaction device to make it have a protective atmosphere, such as argon. After heating the mixture to 80 °C, start to dropwise add 255 g (1.21 mol) of phenyltrichlorosilane to the mixture of lithium hydride and tetraethylene glycol dimethyl ether, and use cold oil to cool and control the reaction temperature within the range of 100 ± 2 °C. After the dropwise addition of phenyltrichlorosilane is completed, continue the reaction for 12 hours. Take 1 mL of the mixture sample and dilute it with 10 mL of n-hexane, filter and take samples to test the chromatographic composition to monitor the reaction progress.

[0054] After the reaction reaches the maximum limit, maintain the heating temperature at 100 ± 2 °C, and separate phenylsilane by vacuum distillation. A pure product of phenylsilane with a purity of 99.994% can be obtained, which contains 0.006% of phenylmonochlorosilane and the chlorine content is 15 ppm.

[0055] Comparative Example 1

[0056] Weigh 39.7 g (4.99 mol) of lithium hydride and add it to 630 mL of the solvent tetraethylene glycol dimethyl ether. Replace the atmosphere of the reaction device, heat the mixture to 80 °C, dropwise add 252 g (1.19 mol) of phenyltrichlorosilane to the mixture of lithium hydride and tetraethylene glycol dimethyl ether, and use cold oil to cool and control the reaction temperature within the range of 100 ± 2 °C. After the dropwise addition of phenyltrichlorosilane is completed, continue the reaction for 12 hours. Take 1 mL of the mixture sample and dilute it with 10 mL of n-hexane, filter and take samples to test the chromatographic composition to monitor the reaction progress.

[0057] After the reaction reaches the maximum limit, maintain the heating temperature at 100 ± 2 °C, and separate phenylsilane by vacuum distillation. A pure product of phenylsilane with a purity of 99.649% can be obtained, which contains 0.351% of phenylmonochlorosilane and the chlorine content is 865 ppm.

[0058] Through the comparison between the above examples and comparative examples, it can be found that adding sodium borohydride with a weight ratio of about 5% of lithium hydride in the process of preparing phenylsilane by reducing phenyltrichlorosilane with lithium hydride can improve the conversion rate of phenylsilane, greatly reduce the content of phenylchlorosilane by-products, and thus greatly reduce the chlorine content in the purified phenylsilane pure product. At the same time, using high-boiling tetraethylene glycol dimethyl ether as the solvent in the reduction reaction, high-purity phenylsilane products can be simply and quickly separated by vacuum distillation after the reaction is completed.

[0059] Example 2

[0060] This example is generally the same as Example 1, and the main difference lies in adjusting the content of sodium borohydride, which is respectively adjusted to 1% and 10% of the weight ratio of lithium hydride, and phenylsilane with a chlorine content meeting the requirements can be obtained.

[0061] Example 3

[0062] This example is generally the same as Example 1, and the main difference lies in replacing the reducing agent and the catalyst. The reducing agent is replaced by sodium hydride, and the phase transfer catalyst is replaced by potassium borohydride. Still, phenylsilane with a chlorine content meeting the requirements can be obtained.

[0063] Example 4

[0064] This example is generally the same as Example 1, and the main difference lies in replacing phenyltrichlorosilane with p-tolyltrichlorosilane. The obtained p-tolylsilane contains only 0.01% of p-tolylchlorosilane, and the chlorine content is 22 ppm.

[0065] In addition, based on the above description, the embodiments of the present invention also replace various feasible arylchlorosilanes, reducing agents, and phase transfer catalysts, and all can achieve equivalent technical effects, realizing a significant increase in the conversion rate and a significant decrease in the chlorine content.

[0066] Based on the above examples and comparative examples, it can be clear that the preparation method provided by the present invention uses an alkali metal borohydride as a phase transfer catalyst to improve the reduction ability of the alkali metal hydride reducing agent, thereby improving the chemical reaction process of reducing arylchlorosilane to prepare arylsilane, so that the reaction proceeds in the direction of complete reaction, significantly reducing the intermediate products in the final product, especially the content of arylmonochlorosilane, and high-purity arylsilane with a very low chlorine content can be obtained.

[0067] It should be understood that the above examples are only used to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A preparation method for improving the conversion rate of preparing arylsilane by reducing arylchlorosilane, characterized in that, it includes: forming a reduction reaction system of arylchlorosilane, a reducing agent and a phase transfer catalyst in an ether solvent; after heating the reduction reaction system for reaction, obtaining arylsilane by vacuum distillation; wherein, the reducing agent includes alkali metal hydride, and the phase transfer catalyst includes alkali metal borohydride.

2. The preparation method according to claim 1, characterized in that, the arylchlorosilane includes any one or a combination of two or more of phenyltrichlorosilane, phenyldichlorosilane, phenylmonochlorosilane, o-tolyltrichlorosilane, m-tolyltrichlorosilane, p-tolyltrichlorosilane, o-tolyldichlorosilane, m-tolyldichlorosilane, p-tolyldichlorosilane, o-tolylmonochlorosilane, m-tolylmonochlorosilane, p-tolylmonochlorosilane.

3. The preparation method according to claim 1, characterized in that, The alkali metal hydride includes any one or a combination of two or more of LiH, NaH, KH, LiAlH 4 , NaAlH 4 and KAlH 4 ; and / or, the alkali metal borohydride includes NaBH 4 , LiBH 4 and KBH 4 or any combination of two or more thereof.

4. The preparation method according to claim 1, characterized in that, the ether solvent is selected from high-boiling ether solvents with a boiling point 100 °C higher than that of the arylsilane, preferably higher than 150 °C; preferably, the boiling point of the ether solvent is at least 270 °C.

5. The preparation method according to claim 4, characterized in that, the high-boiling ether solvent includes any one or a combination of two or more of tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether and diethylene glycol dibutyl ether.

6. The preparation method according to claim 1, characterized in that, in the reduction reaction system, the molar ratio of the chlorine atom in arylchlorosilane to the hydrogen atom of the reducing agent is (0.5 - 1):1; and / or, in the reduction reaction system, the content of the phase transfer catalyst is 1 - 10% of the total mass of the reducing agent; and / or, in the reduction reaction system, the mass ratio of the reducing agent to the ether solvent is 1:(5 - 100).

7. The preparation method according to claim 1, characterized in that, specifically includes: fully mixing the reducing agent, the phase transfer catalyst and the ether solvent, and then heating to the reaction temperature; slowly adding the arylchlorosilane to the precursor system, controlling the reaction temperature to be stable, and maintaining the reaction temperature to complete the reduction reaction after the addition.

8. The preparation method according to claim 7, characterized in that, the reaction temperature is 80 - 120 °C, and the reduction reaction time is 1 - 24 h.

9. The preparation method according to claim 7, characterized in that, it further includes: maintaining the reaction temperature for the vacuum distillation.

10. The preparation method according to claim 1, characterized in that, the purity of the obtained arylsilane is above 99.99%, the mass ratio of the intermediate arylmonochlorosilane is below 0.01%, and the chlorine content is below 25 ppm.