Rectification and purification method of tetramethylsilane

Abstract

The invention discloses a rectification purification method of tetramethylsilane, which comprises the following steps: (a) adding a low-boiling-point substance of methyl chlorosilane synthesized by a direct method into water, hydrolyzing, adding into a first rectification tower after hydrolysis, carrying out rectification heavy component removal treatment, introducing the obtained product into a condenser from the tower top, then entering a second rectification tower, and carrying out primary light component removal treatment to obtain a low-boiling-point substance; a rectification treatment product is obtained; (b) carrying out adsorption treatment on the rectification treatment product in the step (a) to obtain an adsorption treatment product after the adsorption is completed; and (c) carrying out liquefaction treatment on an adsorption treatment product in the step (b) to obtain liquid-phase tetramethylsilane, then feeding the liquid-phase tetramethylsilane into a third rectifying tower, and carrying out secondary light component removal treatment to obtain the high-purity tetramethylsilane. According to the method, most impurities in the tetramethylsilane can be removed, so that the purity of the obtained tetramethylsilane is remarkably improved, the application field of the tetramethylsilane is expanded, and the method has a good application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of tetramethylsilane purification, and particularly relates to a distillation purification method for tetramethylsilane. Background Art

[0002] Tetramethylsilane is an important organic silicon material, which is widely used in medicine, aerospace construction and mechanical materials. Tetramethylsilane has no molecular polarity, stable chemical properties, and a low boiling point at normal pressure of only 26.5°C. The most direct application of tetramethylsilane is as 1 H. 13 C and Si NMR analysis internal standard reference reagent. At the same time, it can be used as a foaming agent for polyurethane or polyolefin foam plastics. Ultra-high purity (mass fraction 99.99%) tetramethylsilane can be used as a precursor for chemical vapor deposition (CVD) or plasma enhanced chemical vapor deposition (PECVD) in the electronics industry to prepare high-quality silicon carbide films. In addition, tetramethylsilane can also be used to prepare semiconductor silicon materials, low dielectric constant materials, plasma polymerization silicone films, waterproof materials, and as a raw material for fumed silica.

[0003] Industrially, methylchlorosilane is synthesized by direct method by methyl chloride and silicon powder under copper catalysis. In the direct method synthesis process, the main product is dimethyldichlorosilane, accounting for more than 80% of the total amount. At the same time, a large amount of methylchlorosilane mixture is also produced, including methyltrichlorosilane, trimethylchlorosilane, methyldichlorosilane, low boiling point silane mixture (referred to as low boiling point, LBR) and high boiling point silane mixture (referred to as high boiling point, HBR). The low boiling point contains about 40% of tetramethylsilane, small molecular alkanes of C3-C5, small molecular olefins of C3-C5, halogenated hydrocarbons such as methyl chloride and ethyl chloride, and a small amount of impurities such as trimethylsilane, dimethyl monochlorosilane, trichlorosilane, monomethyldichlorosilane, etc. The method of enriching and purifying the low boiling point mixture constitutes the main method for preparing tetramethylsilane. This method has high economic value. If the purification method is used for enrichment and purification, it can effectively reduce the company's low-boiling hazardous waste emissions and increase corporate benefits. However, this method has many impurities produced by synthesis, and there is an impurity isopentane (30°C) with a boiling point close to the target product tetramethylsilane (26°C-28°C). It was observed that during the distillation process, tetramethylsilane will co-exist with organic impurities such as isopentane, 2-pentene, and cyclopropylethane, making purification very difficult. In addition to the LBR enrichment method, tetramethylsilane can also be prepared by synthesis. Using tetrachlorosilane or ethyl orthosilicate as a silicon source and methyl magnesium iodide as a methyl source, under laboratory conditions, low-temperature, anhydrous and oxygen-free conditions, a relatively low to medium yield of tetramethylsilane can be achieved, which cannot be applied to large-scale industrial production.

[0004] Chinese patent CN118146256A discloses a method for removing 2-chloropropane from a tetramethylsilane raw material, comprising the following steps: S11, mixing and reacting the vaporized tetramethylsilane raw material with a Fe-Na-MOR molecular sieve catalyst under heating conditions; S12, collecting the reaction product, cooling and liquefying it, and distilling it to obtain purified tetramethylsilane. The method for removing 2-chloropropane from a tetramethylsilane raw material of the present invention is to catalyze the reaction of 2-chloropropane in the tetramethylsilane raw material into propylene and HCl by mixing and reacting the tetramethylsilane raw material with a Fe-Na-MOR molecular sieve catalyst, and propylene and HCl can be easily separated from tetramethylsilane by distillation, thereby obtaining purified tetramethylsilane and removing 2-chloropropane impurities from the tetramethylsilane raw material. However, the patent purifies tetramethylsilane by molecular sieve, which only removes the 2-chloropropane impurity in tetramethylsilane, and the removal effect of other impurities in tetramethylsilane cannot be known from its specification.

[0005] Therefore, there is an urgent need in the art for a method for purifying tetramethylsilane to obtain high-purity tetramethylsilane. Summary of the invention

[0006] In view of the deficiencies in the prior art, the object of the present invention is to provide a distillation purification method for tetramethylsilane, which can remove most of the impurities in tetramethylsilane, significantly improve the purity of the obtained tetramethylsilane, expand the application field of tetramethylsilane, and has good application prospects.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A distillation purification method for tetramethylsilane comprises the following steps:

[0009] (a) adding low-boiling products of direct synthesis of methylchlorosilane into water for hydrolysis, adding the hydrolyzed products into a first distillation tower for distillation and heavy removal treatment, introducing the obtained products into a condenser from the tower top, and then entering a second distillation tower for a light removal treatment to obtain a distillation product;

[0010] (b) subjecting the distillation product in step (a) to adsorption treatment, and after the adsorption is completed, obtaining an adsorption product;

[0011] (c) liquefying the adsorption product in step (b) to obtain liquid tetramethylsilane, and then entering a third distillation tower to perform a secondary light removal treatment to obtain high-purity tetramethylsilane;

[0012] Wherein, the adsorption treatment in step (b) is to pass the distillation product into an adsorption tank containing an adsorbent for gas-solid adsorption at a temperature of 35-45° C. for 1-2 h.

[0013] Preferably, in step (a), the top pressure of the first distillation tower is 0.05-0.1 MPa, the top temperature is 31-36°C, the bottom pressure is 0.07-0.12 MPa, the bottom temperature is 45-55°C, and the theoretical number of plates is 40-60; the top pressure of the second distillation tower is 0.08-0.13 MPa, the top temperature is 28-32°C, the bottom pressure is 0.1-0.15 MPa, the bottom temperature is 40-50°C, and the theoretical number of plates is 60-80.

[0014] In the present invention, low boiling points are first hydrolyzed, and chlorosilane or methylchlorosilane therein is removed by reaction. Impurity compounds such as B and P in the raw materials also react with oxygen atoms of water to form Si-OB bonds or Si-OP bonds, thereby converting donor impurities and acceptor impurities, which can be separated in subsequent distillation to remove heavy and light impurities.

[0015] Preferably, the liquefaction treatment in step (c) is to pass the gaseous tetramethylsilane after adsorption treatment into a cold trap with a temperature of 0 to -30°C to collect liquid tetramethylsilane; the top pressure of the third distillation tower is 0.08-0.13MPa, the top temperature is 28-32°C, the bottom pressure is 0.1-0.15MPa, the bottom temperature is 40-50°C, and the theoretical plate number is 60-80.

[0016] In the present invention, halogenated hydrocarbons such as methyl chloride and ethyl chloride, as well as isopentane, 2-pentene and cyclopropylethane in gaseous tetramethylsilane are adsorbed by gas-solid adsorption, so that the tetramethylsilane after adsorption has a higher purity, and then the tetramethylsilane is further purified by liquefaction and secondary dehydrogenation.

[0017] Preferably, the method for preparing the adsorbent comprises the following steps:

[0018] S1, crushing sorghum straw and adding it into a sodium hydroxide solution for impregnation, filtering, washing and drying after the impregnation is completed to obtain pretreated straw powder;

[0019] S2, mixing the pretreated straw powder in step S1 and the asphalt coke evenly, then adding a metal salt solution and stirring, filtering and drying after the stirring, and calcining under an ammonia atmosphere to obtain composite activated carbon after the calcination;

[0020] S3, adding the composite activated carbon in step S2 to toluene, then adding 2,5-diaminobenzenesulfonic acid and concentrated sulfuric acid, heating to react, filtering, washing and drying after the reaction is completed to obtain modified composite activated carbon;

[0021] S4, adding the modified composite activated carbon in step S3 into deionized water, adjusting the pH to 10-12, then adding carbon disulfide, and reacting at a constant temperature. After the reaction is completed, filtering, washing, and drying to obtain the adsorbent.

[0022] Preferably, the mass fraction of the sodium hydroxide solution in step S1 is 5-15%, the immersion temperature is 40-50° C., and the immersion time is 2-4 hours.

[0023] More preferably, the mass fraction of the sodium hydroxide solution in step S1 is 10-15%, the immersion temperature is 45-50° C., and the immersion time is 2-3 h.

[0024] In the present invention, sorghum straw powder is subjected to alkali heat treatment to make its fiber structure loose, so that the activated carbon obtained subsequently has a complex pore structure and a high specific surface area, which is conducive to the adsorption of polar substances.

[0025] Preferably, the metal salt solution in step S2 is a mixed solution of copper nitrate and zirconium nitrate, the concentration of copper ions is 0.3-0.5 mol / L, and the concentration of zirconium ions is 0.3-0.5 mol / L.

[0026] More preferably, the metal salt solution in step S2 is a mixed solution of copper nitrate and zirconium nitrate, the concentration of copper ions is 0.4-0.5 mol / L, and the concentration of zirconium ions is 0.4-0.5 mol / L.

[0027] Preferably, in step S2, the mass ratio of the pretreated straw powder to the pitch coke is 2-3:7-8; the stirring temperature is 30-40°C, and the time is 2-3h; the calcination temperature is 700-800°C, and the time is 1-2h.

[0028] More preferably, in step S2, the mass ratio of the pretreated straw powder to the pitch coke is 2.5-3:7-7.5; the stirring temperature is 35-40°C, and the time is 2-2.5h; the calcination temperature is 750-800°C, and the time is 1-1.5h.

[0029] In the present invention, the pretreated straw powder is mixed with asphalt coke, doped with metal ions, and calcined in an ammonia atmosphere, so that the surface of the obtained composite activated carbon contains more amino groups, which improves the selective adsorption of polar substances by the adsorbent and is also beneficial to subsequent reactions.

[0030] Preferably, in step S3, the mass ratio of the composite activated carbon, 2,5-diaminobenzenesulfonic acid and concentrated sulfuric acid is 50:5-10:10-15, the temperature of the heating reaction is 60-70° C., and the time is 3-6 hours.

[0031] More preferably, in step S3, the mass ratio of the composite activated carbon, 2,5-diaminobenzenesulfonic acid and concentrated sulfuric acid is 50:7-10:12-15, the temperature of the heating reaction is 65-70° C., and the time is 3-5 h.

[0032] In the present invention, the composite activated carbon is reacted with 2,5-diaminobenzenesulfonic acid to introduce benzene rings on the surface of the activated carbon. The C=C in the olefinic substances will form a π...π stacking interaction with the benzene rings, thereby improving the adsorption performance of the adsorbent for olefins in tetramethylsilane.

[0033] Preferably, the mass ratio of the modified composite activated carbon, deionized water and carbon disulfide in step S4 is 50:600-800:30-35.

[0034] More preferably, the mass ratio of the modified composite activated carbon, deionized water and carbon disulfide in step S4 is 50:700-800:32-35.

[0035] Preferably, the isothermal reaction in step S4 is carried out at a temperature of 20-30° C. and for a time of 3-4 h.

[0036] More preferably, the isothermal reaction in step S4 is carried out at a temperature of 20-25° C. and for a time of 3.5-4 h.

[0037] In the present invention, the modified composite activated carbon is reacted with carbon disulfide to introduce dithioamino groups on the surface of the activated carbon. The sulfur atoms contained in the dithioamino groups have a pair of lone pairs of electrons and can form bonds or interactions with polar substances, thereby significantly improving the adsorption of polar substances by the adsorbent.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The distillation and purification method of tetramethylsilane provided by the present invention is to distill and remove the heavy and light components of the low-boiling products of the direct synthesis of methylchlorosilane, and then adsorb them. Since tetramethylsilane in the low-boiling products is a non-polar substance, and most of the azeotropic impurities are polar substances, the adsorbent is subjected to metal doping and surface modification treatment to improve the selective adsorption of polar substances by the adsorbent, thereby removing most of the impurities in tetramethylsilane. Subsequently, the purity of the obtained tetramethylsilane is significantly improved by liquefaction treatment and secondary dehydrogenation treatment, thereby expanding the application field of tetramethylsilane and having good application prospects.

[0040] (2) The distillation and purification method of tetramethylsilane provided by the present invention comprises the following steps: the adsorbent added in the gas-solid adsorption process is made of sorghum straw and asphalt coke as raw materials, and composite activated carbon is obtained by co-calcination. Since the asphalt coke has a fine pore structure, a large surface area and a uniform pore size distribution, this pore structure is conducive to the entry and retention of adsorbent molecules, thereby improving the adsorption performance of the composite activated carbon; at the same time, by adding pre-pretreated straw powder and asphalt coke to copper nitrate and zirconium nitrate for impregnation adsorption, the pores of the composite activated carbon are doped with metal copper and metal zirconium ions, so that the polarity of the composite activated carbon is enhanced, thereby improving the selective adsorption of polar substances by the adsorbent, and the small molecule substances containing olefins are used as It is a Lewis base that can form π-bond complexes with Lewis acids such as copper ions and zirconium ions, greatly enhancing the adsorption affinity of the adsorbent for molecules containing olefins. Subsequently, the composite activated carbon is reacted with 2,5-diaminobenzenesulfonic acid to introduce benzene rings and amino groups on the surface of the activated carbon. The introduction of benzene rings can form π...π stacking interactions with olefin-containing substances, further improving the selective adsorption of olefin impurities by the adsorbent. Finally, the modified composite activated carbon is reacted with carbon disulfide to introduce dithioamino groups into the activated carbon. The sulfur atoms in the dithioamino groups can form bonds or interactions with polar substances, thereby removing a large amount of polar impurities in gas-phase tetramethylsilane and significantly improving the purity of tetramethylsilane. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] The pitch coke was purchased from Henan Yongshunda Trading Co., Ltd., with a particle size of 0.2-0.5 mm and a fixed carbon content of 93-95%.

[0043] Example 1

[0044] A distillation purification method for tetramethylsilane comprises the following steps:

[0045] (a) adding low-boiling substances of direct synthesis of methylchlorosilane to water, the mass ratio of low-boiling substances to water is 1:1, hydrolyzing at 10°C for 40min, adding to the first distillation tower after hydrolysis, and performing distillation and de-heavy treatment, the tower top pressure of the distillation tower is 0.058MPa, the tower top temperature is 34°C, the tower bottom pressure is 0.01MPa, the tower bottom temperature is 50°C, and the theoretical plate number is 50, the obtained product is introduced into a condenser from the tower top, and then enters a second distillation tower, and performs a light removal treatment, the tower top pressure of the distillation tower is 0.11MPa, the tower top temperature is 30°C, the tower bottom pressure is 0.13MPa, the tower bottom temperature is 43°C, and the theoretical plate number is 50, to obtain a distillation treatment product;

[0046] (b) passing the distillation product in step (a) into an adsorption tank containing an adsorbent for gas-solid adsorption at a temperature of 40° C. for 1.5 h to obtain an adsorption product;

[0047] (c) passing the adsorption product in step (b) into a cold trap at a temperature of -15°C to obtain liquid tetramethylsilane, and then entering a third distillation tower for secondary light removal treatment, wherein the top pressure of the distillation tower is 0.1 MPa, the top temperature is 30°C, the bottom pressure is 0.13 MPa, the bottom temperature is 45°C, and the theoretical plate number is 70, thereby obtaining high-purity tetramethylsilane;

[0048] The preparation method of the adsorbent comprises the following steps:

[0049] S1. 50 g of sorghum straw was crushed and added into 800 g of 10% sodium hydroxide solution, and immersed at 45° C. for 3 h. After the immersion was completed, the sorghum straw was filtered, washed and dried to obtain pretreated straw powder.

[0050] S2, 25g of the pretreated straw powder in step S1 was mixed evenly with 75g of asphalt coke, and then 1L of a mixed solution of copper nitrate and zirconium nitrate (the concentration of copper ions was 0.4mol / L, and the concentration of zirconium ions was 0.4mol / L) was added, and stirred at 35°C for 2.5h. After stirring, the mixture was filtered and dried, and calcined in an ammonia atmosphere at a temperature of 750°C for 1.5h. After calcination, composite activated carbon was obtained;

[0051] S3, adding 50g of the composite activated carbon in step S2 to 800mL of toluene, then adding 8g of 2,5-diaminobenzenesulfonic acid and 13g of concentrated sulfuric acid, reacting at 65°C for 5h, filtering, washing and drying after the reaction is completed to obtain modified composite activated carbon;

[0052] S4. Add 50g of the modified composite activated carbon in step S3 to 700g of deionized water, add 5% sodium hydroxide solution by mass to adjust the pH to 11, then add 33g of carbon disulfide, and react at a constant temperature of 25°C for 3.5h. After the reaction is completed, filter, wash and dry to obtain the adsorbent.

[0053] In this embodiment, the purity of tetramethylsilane in the low-boiling-point raw material is 61.8%, and the purity of the obtained high-purity tetramethylsilane is 99.956%.

[0054] Example 2

[0055] A distillation purification method for tetramethylsilane comprises the following steps:

[0056] (a) adding low-boiling substances of direct synthesis of methylchlorosilane to water, the mass ratio of low-boiling substances to water is 1:1, hydrolyzing at 10°C for 40min, adding to the first distillation tower after hydrolysis, and performing distillation and de-heavy treatment, the tower top pressure of the distillation tower is 0.05MPa, the tower top temperature is 31°C, the tower bottom pressure is 0.07MPa, the tower bottom temperature is 45°C, the theoretical plate number is 40, and the obtained product is introduced into a condenser from the tower top, and then enters a second distillation tower, and performs a light removal treatment, the tower top pressure of the distillation tower is 0.08MPa, the tower top temperature is 28°C, the tower bottom pressure is 0.1MPa, the tower bottom temperature is 40°C, and the theoretical plate number is 60, to obtain a distillation treatment product;

[0057] (b) passing the distillation product in step (a) into an adsorption tank containing an adsorbent for gas-solid adsorption at a temperature of 35° C. for 2 h to obtain an adsorption product;

[0058] (c) passing the adsorption product in step (b) into a cold trap at a temperature of 0° C. to obtain liquid tetramethylsilane, and then entering a third distillation tower for secondary light removal treatment, wherein the top pressure of the distillation tower is 0.08 MPa, the top temperature is 28° C., the bottom pressure is 0.1 MPa, the bottom temperature is 40° C., and the theoretical plate number is 60, thereby obtaining high-purity tetramethylsilane;

[0059] The preparation method of the adsorbent comprises the following steps:

[0060] S1. 50 g of sorghum straw was crushed and added into 800 g of 5% sodium hydroxide solution, and immersed at 40° C. for 4 h. After the immersion was completed, the sorghum straw was filtered, washed and dried to obtain pretreated straw powder.

[0061] S2, 20g of the pretreated straw powder in step S1 was mixed evenly with 80g of asphalt coke, and then 1L of a mixed solution of copper nitrate and zirconium nitrate (the concentration of copper ions was 0.3mol / L and the concentration of zirconium ions was 0.5mol / L) was added, and stirred at 30°C for 3h. After stirring, the mixture was filtered and dried, and calcined under an ammonia atmosphere at a temperature of 700°C for 2h. After calcination, composite activated carbon was obtained;

[0062] S3, adding 50g of the composite activated carbon in step S2 to 800mL of toluene, then adding 5g of 2,5-diaminobenzenesulfonic acid and 10g of concentrated sulfuric acid, reacting at 60°C for 6h, filtering, washing and drying after the reaction is completed to obtain modified composite activated carbon;

[0063] S4. Add 50 g of the modified composite activated carbon in step S3 into 600 g of deionized water, add a 5% sodium hydroxide solution to adjust the pH to 10, then add 30 g of carbon disulfide, and react at a constant temperature of 20°C for 4 hours. After the reaction is completed, filter, wash and dry to obtain the adsorbent.

[0064] In this embodiment, the purity of tetramethylsilane in the low-boiling-point raw material is 60.4%, and the purity of the obtained high-purity tetramethylsilane is 99.923%.

[0065] Example 3

[0066] A distillation purification method for tetramethylsilane comprises the following steps:

[0067] (a) adding low-boiling substances of direct synthesis of methylchlorosilane to water, the mass ratio of low-boiling substances to water is 1:1, hydrolyzing at 10°C for 40min, adding to the first distillation tower after hydrolysis, and performing distillation and de-heavy treatment, the tower top pressure of the distillation tower is 0.1MPa, the tower top temperature is 36°C, the tower bottom pressure is 0.12MPa, the tower bottom temperature is 55°C, and the theoretical plate number is 60, and the obtained product is introduced into a condenser from the tower top, and then enters a second distillation tower, and performs a light removal treatment, the tower top pressure of the distillation tower is 0.13MPa, the tower top temperature is 32°C, the tower bottom pressure is 0.15MPa, the tower bottom temperature is 50°C, and the theoretical plate number is 80, to obtain a distillation treatment product;

[0068] (b) passing the distillation product in step (a) into an adsorption tank containing an adsorbent for gas-solid adsorption at a temperature of 45° C. for 1 h to obtain an adsorption product;

[0069] (c) passing the adsorption product in step (b) into a cold trap at a temperature of -30°C to obtain liquid tetramethylsilane, and then entering a third distillation tower for secondary light removal treatment, wherein the top pressure of the distillation tower is 0.13 MPa, the top temperature is 32°C, the bottom pressure is 0.15 MPa, the bottom temperature is 50°C, and the theoretical plate number is 80, thereby obtaining high-purity tetramethylsilane;

[0070] The preparation method of the adsorbent comprises the following steps:

[0071] S1. 50 g of sorghum straw was crushed and added into 800 g of 15% sodium hydroxide solution, and immersed at 50° C. for 2 h. After the immersion was completed, it was filtered, washed and dried to obtain pretreated straw powder;

[0072] S2, 30g of the pretreated straw powder in step S1 was mixed evenly with 70g of asphalt coke, and then 1L of a mixed solution of copper nitrate and zirconium nitrate (the concentration of copper ions was 0.5mol / L and the concentration of zirconium ions was 0.3mol / L) was added, and stirred at 40°C for 2h. After stirring, the mixture was filtered and dried, and calcined in an ammonia atmosphere at a temperature of 800°C for 1h. After calcination, composite activated carbon was obtained;

[0073] S3, adding 50g of the composite activated carbon in step S2 to 800mL of toluene, then adding 10g of 2,5-diaminobenzenesulfonic acid and 15g of concentrated sulfuric acid, reacting at 70°C for 3h, filtering, washing and drying after the reaction is completed to obtain modified composite activated carbon;

[0074] S4. Add 50g of the modified composite activated carbon in step S3 into 800g of deionized water, add 5% sodium hydroxide solution by mass to adjust the pH to 12, then add 35g of carbon disulfide, and react at a constant temperature of 30°C for 3h. After the reaction is completed, filter, wash and dry to obtain the adsorbent.

[0075] In this embodiment, the purity of tetramethylsilane in the low-boiling-point raw material is 64.1%, and the purity of the obtained high-purity tetramethylsilane is 99.945%.

[0076] Comparative Example 1

[0077] A distillation purification method for tetramethylsilane comprises the following steps:

[0078] (a) adding low-boiling substances of direct synthesis of methylchlorosilane to water, the mass ratio of low-boiling substances to water is 1:1, hydrolyzing at 10°C for 40min, adding to the first distillation tower after hydrolysis, and performing distillation and de-heavy treatment, the tower top pressure of the distillation tower is 0.058MPa, the tower top temperature is 34°C, the tower bottom pressure is 0.01MPa, the tower bottom temperature is 50°C, and the theoretical plate number is 50, the obtained product is introduced into a condenser from the tower top, and then enters a second distillation tower, and performs a light removal treatment, the tower top pressure of the distillation tower is 0.11MPa, the tower top temperature is 30°C, the tower bottom pressure is 0.13MPa, the tower bottom temperature is 43°C, and the theoretical plate number is 50, to obtain a distillation treatment product;

[0079] (b) passing the distillation product in step (a) into an adsorption tank containing an adsorbent for gas-solid adsorption at a temperature of 40° C. for 1.5 h to obtain an adsorption product;

[0080] (c) passing the adsorption product in step (b) into a cold trap at a temperature of -15°C to obtain liquid tetramethylsilane, and then entering a third distillation tower for secondary light removal treatment, wherein the top pressure of the distillation tower is 0.1 MPa, the top temperature is 30°C, the bottom pressure is 0.13 MPa, the bottom temperature is 45°C, and the theoretical plate number is 70, thereby obtaining high-purity tetramethylsilane;

[0081] The preparation method of the adsorbent comprises the following steps:

[0082] S1. 50 g of sorghum straw was crushed and added into 800 g of 10% sodium hydroxide solution, and immersed at 45° C. for 3 h. After the immersion was completed, the sorghum straw was filtered, washed and dried to obtain pretreated straw powder.

[0083] S2. Evenly mix 25 g of pretreated straw powder and 75 g of asphalt coke in step S1, then add 1 L of a mixed solution of copper nitrate and zirconium nitrate (the concentration of copper ions is 0.4 mol / L, and the concentration of zirconium ions is 0.4 mol / L), stir at 35°C for 2.5 h, filter and dry after stirring, and calcine in an ammonia atmosphere at a temperature of 750°C for 1.5 h. After calcination, the adsorbent is obtained.

[0084] In this comparative example, the purity of tetramethylsilane in the low-boiling-point raw material is 62.2%, and the purity of the obtained high-purity tetramethylsilane is 93.851%.

[0085] Comparative Example 2

[0086] A distillation purification method for tetramethylsilane comprises the following steps:

[0087] (a) adding low-boiling substances of direct synthesis of methylchlorosilane to water, the mass ratio of low-boiling substances to water is 1:1, hydrolyzing at 10°C for 40min, adding to the first distillation tower after hydrolysis, and performing distillation and de-heavy treatment, the tower top pressure of the distillation tower is 0.058MPa, the tower top temperature is 34°C, the tower bottom pressure is 0.01MPa, the tower bottom temperature is 50°C, and the theoretical plate number is 50, the obtained product is introduced into a condenser from the tower top, and then enters a second distillation tower, and performs a light removal treatment, the tower top pressure of the distillation tower is 0.11MPa, the tower top temperature is 30°C, the tower bottom pressure is 0.13MPa, the tower bottom temperature is 43°C, and the theoretical plate number is 50, to obtain a distillation treatment product;

[0088] (b) passing the distillation product in step (a) into an adsorption tank containing an adsorbent for gas-solid adsorption at a temperature of 40° C. for 1.5 h to obtain an adsorption product;

[0089] (c) passing the adsorption product in step (b) into a cold trap at a temperature of -15°C to obtain liquid tetramethylsilane, and then entering a third distillation tower for secondary light removal treatment, wherein the top pressure of the distillation tower is 0.1 MPa, the top temperature is 30°C, the bottom pressure is 0.13 MPa, the bottom temperature is 45°C, and the theoretical plate number is 70, thereby obtaining high-purity tetramethylsilane;

[0090] The preparation method of the adsorbent comprises the following steps:

[0091] S1. 50 g of sorghum straw was crushed and added into 800 g of 10% sodium hydroxide solution, and immersed at 45° C. for 3 h. After the immersion was completed, the sorghum straw was filtered, washed and dried to obtain pretreated straw powder.

[0092] S2, 25g of the pretreated straw powder in step S1 was mixed evenly with 75g of asphalt coke, and calcined in an ammonia atmosphere at a temperature of 750°C for 1.5h to obtain composite activated carbon;

[0093] S3. Add 50g of the composite activated carbon in step S2 into 700g of deionized water, add 5% sodium hydroxide solution by mass to adjust the pH to 11, then add 33g of carbon disulfide, and react at a constant temperature of 25°C for 3.5h. After the reaction is completed, filter, wash and dry to obtain the adsorbent.

[0094] In this comparative example, the purity of tetramethylsilane in the low-boiling-point raw material is 61.3%, and the purity of the obtained high-purity tetramethylsilane is 95.418%.

[0095] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for the rectification and purification of tetramethylsilane, characterized in that: The following steps are involved: (a) adding low-boiling products of direct synthesis of methylchlorosilane into water for hydrolysis, adding the hydrolyzed products into a first distillation tower for distillation and heavy removal treatment, introducing the obtained products into a condenser from the tower top, and then entering a second distillation tower for a light removal treatment to obtain a distillation product; (b) subjecting the distillation product in step (a) to adsorption treatment, and after the adsorption is completed, obtaining an adsorption product; (c) liquefying the adsorption product in step (b) to obtain liquid tetramethylsilane, and then entering a third distillation tower to perform a secondary light removal treatment to obtain high-purity tetramethylsilane; Wherein, the adsorption treatment in step (b) is to pass the distillation product into an adsorption tank containing an adsorbent for gas-solid adsorption at a temperature of 35-45° C. for 1-2 h.

2. The method according to claim 1, characterized in that In step (a), the top pressure of the first distillation tower is 0.05-0.1MPa, the top temperature is 31-36°C, the bottom pressure is 0.07-0.12MPa, the bottom temperature is 45-55°C, and the theoretical number of plates is 40-60; the top pressure of the second distillation tower is 0.08-0.13MPa, the top temperature is 28-32°C, the bottom pressure is 0.1-0.15MPa, the bottom temperature is 40-50°C, and the theoretical number of plates is 60-80.

3. The method according to claim 1, characterized in that The liquefaction treatment in step (c) is to pass the gaseous tetramethylsilane after adsorption treatment into a cold trap with a temperature of 0 to -30°C to collect liquid tetramethylsilane; the top pressure of the third distillation tower is 0.08-0.13MPa, the top temperature is 28-32°C, the bottom pressure is 0.1-0.15MPa, the bottom temperature is 40-50°C, and the theoretical plate number is 60-80.

4. The method according to claim 1, characterized in that: The preparation method of the adsorbent comprises the following steps: S1, crushing sorghum straw and adding it into a sodium hydroxide solution for impregnation, filtering, washing and drying after the impregnation is completed to obtain pretreated straw powder; S2, mixing the pretreated straw powder and asphalt coke in step S1 uniformly, then adding a metal salt solution, stirring, filtering, drying, and calcining under an ammonia atmosphere, and obtaining composite activated carbon after calcination; S3, adding the composite activated carbon in step S2 to toluene, then adding 2,5-diaminobenzenesulfonic acid and concentrated sulfuric acid, heating to react, filtering, washing and drying after the reaction is completed to obtain modified composite activated carbon; S4, adding the modified composite activated carbon in step S3 into deionized water, adjusting the pH to 10-12, then adding carbon disulfide, and reacting at a constant temperature. After the reaction is completed, filtering, washing, and drying to obtain the adsorbent.

5. The method according to claim 4, characterized in that The mass fraction of the sodium hydroxide solution in step S1 is 5-15%, the immersion temperature is 40-50° C., and the immersion time is 2-4 hours.

6. The method according to claim 4, characterized in that The metal salt solution in step S2 is a mixed solution of copper nitrate and zirconium nitrate, the concentration of copper ions is 0.3-0.5 mol / L, and the concentration of zirconium ions is 0.3-0.5 mol / L.

7. The method according to claim 4, characterized in that In step S2, the mass ratio of the pretreated straw powder to the pitch coke is 2-3:7-8; the stirring temperature is 30-40°C and the time is 2-3h; the calcination temperature is 700-800°C and the time is 1-2h.

8. The method according to claim 4, characterized in that In step S3, the mass ratio of the composite activated carbon, 2,5-diaminobenzenesulfonic acid and concentrated sulfuric acid is 50:5-10:10-15, the temperature of the heating reaction is 60-70° C., and the time is 3-6 hours.

9. The method according to claim 4, characterized in that The mass ratio of the modified composite activated carbon, deionized water and carbon disulfide in step S4 is 50:600-800:30-35.

10. The method according to claim 4, characterized in that The isothermal reaction in step S4 is carried out at a temperature of 20-30° C. and for a time of 3-4 hours.