Vinyl tri (2-cyanoethyl) silicate ester and preparation method thereof

Abstract

The invention provides vinyl tri (2-cyanoethyl) silicate ester and a preparation method thereof, belongs to the technical field of lithium ion battery electrolyte additives, and can solve the problems of insufficient electrochemical stability and poor low-temperature performance when an organosilicon compound is used as an electrolyte additive in the prior art. The vinyl tri (2-cyanoethyl) silicate ester has the following structural formula: # imgabs0 #. The vinyl tri (2-cyanoethyl) silicate ester can be applied to an electrolyte additive of a lithium ion battery, and has the advantages of improving the high and low temperature performance of the battery and improving the stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery electrolyte additives, and particularly relates to vinyl tris(2-cyanoethyl) silicate and a preparation method thereof. Background Art

[0002] With the rapid development of fields such as electronic products and electric vehicles, the market has put forward higher requirements for the energy density, operating temperature range, cycle life, and safety performance of lithium batteries. As an important component of lithium batteries, the performance of the electrolyte directly affects the overall performance of the battery. Optimizing the physical and chemical properties of the electrolyte by adding functional additives has become one of the effective ways to improve battery performance. Organosilicon compounds have received extensive attention in the field of lithium battery electrolyte additives due to their unique physical and chemical properties, but there are problems of insufficient electrochemical stability and poor low-temperature performance. Therefore, developing new organosilicon compounds as electrolyte additives is of great significance for improving the comprehensive performance of lithium batteries and promoting the technological progress of lithium batteries. Summary of the Invention

[0003] In view of the technical problems of insufficient electrochemical stability and poor low-temperature performance when using organosilicon compounds as electrolyte additives in the above-mentioned prior art, the present invention provides vinyl tris(2-cyanoethyl) silicate and a preparation method thereof, which can be applied to lithium-ion battery electrolyte additives and have the advantages of improving the high and low temperature performance of the battery and enhancing stability.

[0004] To achieve the above object, on the one hand, the present invention provides a vinyl tris(2-cyanoethyl) silicate, and the technical solution adopted is: vinyl tris(2-cyanoethyl) silicate has the following structural formula:

[0005]

[0006] On the other hand, the present invention also provides a preparation method of the above vinyl tris(2-cyanoethyl) silicate, including the following steps: adding a mixed solution of vinyl trichlorosilane and a second organic solvent to a mixed solution of 3-hydroxypropionitrile, an organic base, and a first organic solvent, and obtaining vinyl tris(2-cyanoethyl) silicate after purification treatment after the dropping is completed; wherein, the molar ratio of 3-hydroxypropionitrile, vinyl trichlorosilane to the organic base is (3.0 - 3.3):1:3.

[0007] In some embodiments, both the first organic solvent and the second organic solvent include at least one of chain carbonate esters, carboxylic acid esters, ethers, and nitriles.

[0008] In some embodiments, the chain carbonate esters include at least one of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0009] In some embodiments, the organic base includes at least one of pyridine, triethylamine, and sodium tert-butoxide.

[0010] In some embodiments, the step of adding a mixed solution of vinyltrichlorosilane and a second organic solvent to a mixed solution of 3-hydroxypropionitrile, an organic base, and a first organic solvent specifically includes the following steps: slowly dropwise adding a mixed solution of vinyltrichlorosilane and a second organic solvent to a mixed solution of 3-hydroxypropionitrile, an organic base, and a first organic solvent, and continuing the reaction for 1 h - 3 h after the dropwise addition is completed. Among them, the temperature of the reaction system is less than 0 °C during the dropwise addition and the continuous reaction process, and the starting temperature of the dropwise addition is -5 °C.

[0011] In some embodiments, adding a mixed solution of vinyltrichlorosilane and a second organic solvent to a mixed solution of 3-hydroxypropionitrile, an organic base, and a first organic solvent is carried out in a glove box or a drying room, and the environmental dew point is controlled below -60 °C.

[0012] In some embodiments, the purification treatment step includes the following steps: performing suction filtration using a suction filtration device, subjecting the separated filtrate to rotary evaporation, then performing vacuum distillation, and finally obtaining vinyl tris(2-cyanoethyl) silicate through molecular distillation.

[0013] In some embodiments, in the vacuum distillation step, the temperature of the distillation head is controlled at 100 °C - 130 °C.

[0014] In some embodiments, the molecular distillation step specifically includes the following steps:

[0015] Performing a first molecular distillation treatment on the product obtained by vacuum distillation treatment, controlling both the inlet and outlet temperatures at 50 °C, and the temperature of the scraper oil bath at 70 - 90 °C, preferably 80 °C;

[0016] Performing a second molecular distillation treatment on the product obtained by the first molecular distillation treatment, controlling both the inlet and outlet temperatures at 50 °C, and the temperature of the scraper oil bath at 90 - 105 °C, preferably 100 °C, to obtain vinyl tris(2-cyanoethyl) silicate.

[0017] Compared with the prior art, the advantages and positive effects of the present invention are as follows: in the vinyl tris(2-cyanoethyl) silicate of the present invention, the vinyl group and functional groups such as cyano group act synergistically to improve the high and low temperature performance of the battery; among them, the unsaturated double bond of the vinyl group can effectively protect the film formation of the positive and negative electrodes; the silicon-oxygen group can enhance the lithium ion conduction performance and effectively reduce the battery impedance; the cyano functional group has a good affinity with hydrogen protons, so that the additive has the effect of removing water and acid, and as the number of cyano groups increases, the effect of removing water and acid becomes more obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1Infrared spectrum of vinyl tris(2-cyanoethyl) silicate in Example 1 of the present invention;

[0019] Figure 2 1H NMR spectrum of vinyl tris(2-cyanoethyl) silicate in Example 1 of the present invention;

[0020] Figure 3 Gas chromatogram of vinyl tris(2-cyanoethyl) silicate in Example 1 of the present invention;

[0021] Figure 4 Enlarged gas chromatogram of vinyl tris(2-cyanoethyl) silicate in Example 1 of the present invention;

[0022] Figure 5 Quantitative test table of gas chromatography of vinyl tris(2-cyanoethyl) silicate in Example 1 of the present invention. Detailed implementation manners

[0023] In order to more comprehensively understand the characteristics and technical content of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the following described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments of the present invention. In the following technical description, for the convenience of explanation, a sufficient understanding of the disclosed embodiments is provided through multiple details. However, one or more embodiments can still be implemented without these details. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope claimed by the present invention.

[0024] The embodiments of the present invention provide a vinyl tris(2-cyanoethyl) silicate and its preparation method, which can improve the performance of lithium batteries. By utilizing the characteristics of the silicon-oxygen bond and other functional groups in its molecule, the regulation of the electrolyte and battery performance can be realized. Among them, the synergistic effect of vinyl and functional groups such as cyano can improve the high and low temperature performance of the battery: in a low temperature environment, it can reduce the viscosity of the electrolyte, increase the ionic conductivity of the electrolyte, enable lithium ions to move smoothly in the electrolyte and intercalate / deintercalate from the electrode material at low temperature, thereby improving the low temperature charge and discharge performance of the battery and increasing the capacity retention rate and charge and discharge efficiency of the battery in a low temperature environment; in a high temperature environment, it can enhance the stability of the electrolyte, reduce the decomposition and volatilization of the electrolyte, reduce the side reaction rate inside the battery, enable the battery to maintain good cycle performance and capacity retention rate at high temperature, and extend the service life of the battery in a high temperature environment.

[0025] The vinyl tris(2-cyanoethyl) silicate in the embodiments of the present invention has the following structural formula:

[0026]

[0027] The vinyl unsaturated double bond in the vinyl tris(2-cyanoethyl) silicate molecule of the present invention can optimize the interfacial properties between the electrolyte and the electrode material, reduce the interfacial impedance, enable lithium ions to more rapidly undergo insertion and extraction reactions on the electrode surface during charge and discharge, and thus improve the rate performance of the battery. At the same time, the unsaturated double bond in the vinyl can also improve the material properties: enhance the flexibility of the material, protect the film formation, and improve the impact resistance of the material.

[0028] The Si-O bond in the vinyl tris(2-cyanoethyl) silicate molecule of the present invention has the functions of enhancing molecular stability and influencing the physical properties of the molecule. First of all, due to the relatively high bond energy of the Si-O bond, generally about 452 kJ / mol, this makes the vinyl tris(2-cyanoethyl) silicate molecule have good stability, be able to maintain the integrity of the molecular structure under certain conditions such as temperature and pH, and is not prone to decomposition; moreover, the presence of the Si-O bond helps to disperse the electron cloud in the molecule, lower the energy state of the molecule, further enhance the molecular stability, enable it to play a role in various environments, and is beneficial to enhancing molecular stability. Due to the polarity of the Si-O bond, the vinyl tris(2-cyanoethyl) silicate molecule has a certain polarity, thus affecting its solubility in different solvents, making it have good solubility in some polar solvents and relatively poor solubility in non-polar solvents; the presence of the Si-O bond also affects the physical properties such as the boiling point and melting point of the molecule. Due to the action of the Si-O bond, the intermolecular interaction force is enhanced, making this substance have a relatively high boiling point and melting point, which is beneficial to maintaining the stability of its physical state at a relatively high temperature in practical applications.

[0029] In the vinyl tris(2-cyanoethyl) silicate molecule of the present invention, the cyano functional group has the following functions: Participating in film formation - constructing the CEI film skeleton: During charging, the cyano group can be adsorbed on the surface of the positive electrode active material through complexation to form the skeleton structure of the positive electrode material interface film (CEI film), which helps other effective components of the electrolyte form a film on the positive electrode surface, stabilizes the structure and composition of the CEI film, prevents the destruction of the positive electrode structure, and inhibits the oxidative decomposition of the electrolyte; Protecting the negative electrode SEI film: The cyano group has a protective effect on the solid electrolyte interface film (SEI film) of the negative electrode, can reduce the damage of transition metals to the SEI film, make the surface morphology of the negative electrode surface more uniform and dense, and improve the safety of the battery during use; At the same time, the participation of the cyano group can reduce side reactions and the gas generation amount; Capturing H protons: When an oxidative side reaction occurs in the electrolyte, the cyano group can preferentially capture H protons, reduce the decomposition of lithium hexafluorophosphate (LiPF6) and fluoroethylene carbonate (FEC), thereby reducing the occurrence of side reactions; Reducing the gas generation amount: The inhibitory effect on the battery side reaction can effectively reduce the gas generation amount of the battery and improve the safety and stability of the battery; Moreover, the cyano group can also improve the electrolyte stability: Due to its high electronegativity, the cyano group can be adsorbed on the positive electrode surface, reduce the contact surface between the electrolyte and the positive electrode, and reduce the direct contact between the electrolyte and the positive electrode material, thereby improving the electrolyte stability and inhibiting its decomposition at high voltages; Removing water and acid, removing moisture: The cyano group itself can react with H2O to generate amino groups, playing a role in removing water, reducing the water content in the electrolyte, and avoiding side reactions caused by moisture; Removing HF: The cyano group has strong electronegativity and can react with HF generated by the decomposition of lithium salts in the electrolyte to remove it, prevent HF from causing interfacial damage to the positive electrode and the dissolution of transition metals, construct a uniform CEI film, and improve the electrochemical stability of the positive electrode.

[0030] The preparation process of vinyl tris(2-cyanoethyl) silicate in the embodiment of the present invention is carried out in a glove box or a drying room, and the environmental dew point is controlled below -60°C. The preparation method specifically includes the following steps: adding a mixed solution of vinyl trichlorosilane and a second organic solvent to a mixed solution of 3-hydroxypropionitrile, an organic base, and a first organic solvent, and obtaining vinyl tris(2-cyanoethyl) silicate after purification treatment after the dropping is completed; wherein, the molar ratio of 3-hydroxypropionitrile, vinyl trichlorosilane, and the organic base is (3.0 - 3.3):1:3. In a preferred embodiment, the molar ratio of 3-hydroxypropionitrile, vinyl trichlorosilane, and the organic base is 3.1:1:3. Using the above molar ratio can make 3-hydroxypropionitrile react fully, promote the reaction to proceed in the direction of generating the target product, improve the conversion rate of 3-hydroxypropionitrile, reduce the residue of unreacted raw materials, and thus provide a high product yield.

[0031] The chemical reaction equation of the present invention is as follows:

[0032]

[0033] In the method for preparing vinyl tris(2-cyanoethyl) silicate according to the embodiment of the present invention, a mixed solution of vinyl trichlorosilane and an organic solvent is dropwise added to a mixed solution of 3-hydroxypropionitrile, an organic base, and an organic solvent. By introducing an organic base into the reaction system, hydrogen chloride generated in the reaction can be continuously neutralized, the acidity in the reaction system can be reduced, the forward reaction can be promoted, the reaction rate can be increased, and the product yield can be improved. The raw materials react in a weakly polar organic system with a low dielectric constant. Vinyl trichlorosilane and 3-hydroxypropionitrile undergo a nucleophilic substitution reaction. The silicon-chlorine bond of vinyl trichlorosilane (CH2=CHSiCl3) is polarized. Since the electronegativity of the chlorine atom is relatively large, the electron cloud of the Si-Cl bond is biased towards the chlorine atom, and the silicon atom has a partial positive charge and has a certain electrophilicity; 3-hydroxypropionitrile (HOCH2CH(OH)CH2CN) undergoes a nucleophilic attack. There are lone pairs of electrons on the oxygen atom of the hydroxyl group, which has a nucleophilic type; the lone pair of electrons on one of the oxygen atoms of the hydroxyl group will attack the silicon atom in vinyl trichlorosilane, and at the same time, a chlorine atom in the Si-Cl bond leaves with a pair of electrons, forming an intermediate, vinyl dichloro(2-cyanoethyl) silicate with the structure of CH2=CHSICl2OCH2CH(OH)CH2CN; there are still two chlorine atoms connected to the silicon atom in the intermediate, and they are continuously attacked by other oxygen atoms of the hydroxyl groups in 3-hydroxypropionitrile to form vinyl monochloro bis(2-cyanoethyl) silicate; as the hydroxyl group of 3-hydroxypropionitrile reacts with the silicon-oxygen bond of vinyl trichlorosilane, the hydrogen atom in the hydroxyl group combines with the chlorine atom to form hydrogen chloride, and the oxygen atom of the hydroxyl group forms a Si-O bond with the silicon atom; there are still hydroxyl groups and silicon-chlorine bonds in the generated intermediate, and they will continue to react, causing the molecules to continuously condense and form a larger molecular structure, and finally generating vinyl tris(2-cyanoethyl) silicate.

[0034] In the above reaction process of the present invention, pyridine is an acid-binding agent, which will consume the hydrogen chloride generated in the reaction, promote the forward reaction, and increase the reaction rate. The reaction mechanism of the pyridine acid-binding agent is as follows: The nitrogen atom in the pyridine molecule has lone pairs of electrons and has strong basicity. The hydrogen ion in hydrogen chloride has acidity. The two undergo an acid-base neutralization reaction, and the hydrogen ion combines with the lone electron on the pyridine nitrogen atom through a coordination bond to form pyridine hydrochloride.

[0035] Both the first organic solvent and the second organic solvent of the present invention include at least one of chain carbonates, carboxylic acid esters, ethers, and nitriles; wherein, the chain carbonates include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC); the carboxylic acid esters include at least one of methyl acetate (MA) and ethyl acetate (EA); the ethers include at least one of dimethoxyethane (DME) and tetrahydrofuran (THF); the nitriles include acetonitrile (AN). In a preferred embodiment, the organic solvent is a solvent with a lower dielectric constant. Since the dielectric constant is a physical quantity that measures the ability of a dielectric to store electric charge under the action of an electric field, polar molecules will undergo orientation polarization in an electric field and are more likely to store electric charge, making the dielectric constant of the material higher; non-polar or weakly polar molecules have a low degree of polarization in an electric field and a weak ability to store electric charge, so the dielectric constant is low. The present invention uses an organic solvent with a lower dielectric constant, making the solubility of the product lower in the solvent system, which is beneficial to obtaining a high-purity product.

[0036] The organic base of the present invention includes at least one of pyridine, triethylamine, and sodium tert-butoxide. By introducing the organic base, the hydrogen chloride generated in the reaction can be continuously neutralized, reducing the acidity in the reaction system, promoting the forward reaction, increasing the reaction rate, and improving the product yield.

[0037] The synthesis and preparation process of the present invention is carried out in a glove box or a drying room, and the environmental dew point is controlled below -60°C. Since the vinyltrichlorosilane molecule contains three chlorine atoms, and the chlorine atom has a large electronegativity, the Si-Cl bond formed with the silicon atom has a strong polarity, and the silicon atom has a partial positive charge, which is easily attacked by the negatively charged oxygen atom in the water molecule, thus triggering a hydrolysis reaction. The present invention carries out the dropping reaction in a glove box or a drying room, which can avoid the hydrolysis reaction of vinyltrichlorosilane.

[0038] During the above dropping process of the present invention, the temperature of the reaction system needs to be controlled. After the temperature of the reaction system is gradually decreased from room temperature to -5°C, a mixed solution of vinyltrichlorosilane and an organic solvent is started to be dropped. During the dropping process, the temperature of the reaction system is kept below 0°C. After the dropping is completed, the above reaction system temperature is maintained for 1 h - 3 h to enable the vinyltrichlorosilane to fully undergo a substitution reaction with 3-hydroxypropionitrile. In a preferred embodiment, the rate of gradient temperature decrease is controlled at 0.5°C / min; in a preferred embodiment, the temperature of the reaction system is kept at -3°C during the dropping process; in a preferred embodiment, the reaction system temperature below 0°C is maintained for 2 h after the dropping is completed.

[0039] The purification process of the preparation method of vinyl tris(2-cyanoethyl) silicate in the embodiments of the present invention belongs to the separation of high-boiling components. In the purification treatment step, first, the synthesized solution is filtered to separate pyridine hydrochloride from the solution; then the filtrate is rotary evaporated to remove the solvent; and then further solvent and pyridine hydrochloride are removed by vacuum distillation to obtain a supersaturated solution containing vinyl tris(2-cyanoethyl) silicate; and then molecular distillation treatment is used to further remove light-component substances and retain high-boiling components, that is, vinyl tris(2-cyanoethyl) silicate of the present invention is obtained.

[0040] In the vacuum distillation step of the above preparation method of the present invention, the reaction system is heated at a gradient temperature, and the temperature of the distillation head is controlled at 100°C - 130°C to further remove organic solvents, excessive 3-hydroxypropionitrile and by-products. In a preferred embodiment, the gradient temperature control rate is 0.5°C / min; in a preferred embodiment, the temperature of the distillation head is controlled at 120°C.

[0041] In the molecular distillation step of the above preparation method of the present invention, the product treated in the vacuum distillation step is subjected to two molecular distillation treatments. For the first molecular distillation treatment, the inlet and outlet temperatures are controlled at 50°C, and the temperature of the scraper oil bath is 70 - 90°C to separate light-component substances such as water, unreacted raw materials and organic solvents; for the second molecular distillation treatment, the inlet and outlet temperatures are controlled at 50°C, and the temperature of the scraper oil bath is 90 - 105°C to obtain vinyl tris(2-cyanoethyl) silicate.

[0042] Vinyl tris(2-cyanoethyl) silicate in the embodiments of the present invention can be used as an additive for lithium-ion battery electrolytes and is suitable for lithium-ion battery electrolytes containing silicon-carbon and silicon-oxygen material battery systems. The vinyl unsaturated double bond in the molecule of vinyl tris(2-cyanoethyl) silicate is beneficial for film formation, can optimize the interfacial performance between the electrolyte and the electrode material, reduce the interfacial impedance, enable lithium ions to be more quickly embedded and de-embedded on the electrode surface during charge and discharge processes, and thus improve the rate performance of the battery; the silicon-oxygen group in the molecule can enhance the conduction performance of lithium ions in the silicon-carbon material battery and effectively reduce the battery impedance; groups such as cyano groups in the molecule may participate in the reaction of inhibiting combustion. When the internal temperature of the battery rises abnormally or encounters other dangerous situations, they can capture free radicals in the combustion reaction process, terminate the free radical chain reaction of combustion, prevent the combustion reaction in the gas phase, reduce the combustion tendency of the electrolyte, and improve the thermal stability and safety of the battery.

[0043] In order to introduce the vinyl tris(2-cyanoethyl) silicate and its preparation method provided by the embodiments of the present invention more clearly and in detail, the following will be described in combination with specific embodiments.

[0044] Example 1

[0045] The preparation method of vinyltris(2-cyanoethyl) silicate in this embodiment includes the following steps:

[0046] Weigh the raw materials vinyltrichlorosilane, 3-hydroxypropionitrile, pyridine, and dimethyl carbonate separately with an electronic balance in a glove box. All raw and auxiliary materials need to be dehydrated before use to ensure that the moisture content is less than 100 ppm. Among them, vinyltrichlorosilane is a commercially available product with a purity of ≥99% and a moisture content of <100 ppm; dimethyl carbonate is a commercially available product with a purity of ≥99% and a moisture content of <100 ppm; 3-hydroxypropionitrile is a commercially available industrial-grade product with a purity of ≥99% and a moisture content of <100 ppm.

[0047] Place 161.49 g of vinyltrichlorosilane and 180.156 g of dimethyl carbonate (diluent) weighed into a constant-pressure dropping funnel and mix them to obtain a first mixed solution.

[0048] Add 220.379 g of 3-hydroxypropionitrile, 237.297 g of pyridine, and 540.468 g of dimethyl carbonate weighed into a double-layer glass reaction kettle and mix them to obtain a second mixed solution. Among them, a mechanical stirrer is connected above the double-layer glass reaction kettle, and the other two ports are respectively connected to a thermometer sleeve and a constant-pressure dropping funnel.

[0049] Turn on the high and low temperature circulation all-in-one machine to cool down the double-layer glass reaction kettle. Start cooling from room temperature at a rate gradient of 0.5 °C / min to -5 °C. After reaching -5 °C, start dropping the first mixed solution. During the dropping process, keep the reaction system temperature below 0 °C. After the dropping is completed, continue to keep the reaction system temperature at 0 °C for 2 h to make the reaction proceed fully.

[0050] Use a sand core G4 suction filtration device for suction filtration, transfer the separated filtrate to a rotary evaporation flask for rotary evaporation treatment, control the rotary evaporation oil bath temperature below 100 °C to obtain 262.6 g of crude product, and then filter the obtained crude product in a glove box to remove the precipitated pyridine hydrochloride.

[0051] Put the filtered crude product into the reaction kettle, raise the temperature gradient, control the distillation head temperature at 120 °C, collect the early fractions, and weigh the product in the reaction kettle as 212.4 g.

[0052] Perform two consecutive molecular distillation treatments on the product in the above reaction kettle. Among them, the first molecular distillation treatment: control the inlet and outlet temperatures at 50 °C and the scraper oil bath temperature at 80 °C to separate water and light components such as raw materials and solvents; the second molecular distillation treatment: control the inlet and outlet temperatures at 50 °C and the scraper oil bath temperature at 100 °C to obtain the heavy component, that is, obtain the vinyltris(2-cyanoethyl) silicate product, and weigh it as 182.24 g.

[0053] Example 2

[0054] The preparation method of vinyltris(2-cyanoethyl) silicate in this embodiment includes the following steps:

[0055] Weigh the raw materials vinyltrichlorosilane, 3-hydroxypropionitrile, pyridine and dimethyl carbonate respectively with an electronic balance in a glove box. All raw and auxiliary materials need to be treated to remove water before use to ensure that the water content is less than 100 ppm. Among them, vinyltrichlorosilane is a commercially available product with a purity ≥ 99% and a water content < 100 ppm; dimethyl carbonate is a commercially available product with a purity ≥ 99% and a water content < 100 ppm; 3-hydroxypropionitrile is a commercially available industrial-grade product with a purity ≥ 99% and a water content < 100 ppm.

[0056] Place 161.49 g of vinyltrichlorosilane and 180.156 g of dimethyl carbonate (diluent) weighed into a constant pressure dropping funnel and mix them to obtain a first mixed solution.

[0057] Add 223.934 g of 3-hydroxypropionitrile, 237.297 g of pyridine and 540.468 g of dimethyl carbonate weighed into a double-layer glass reaction kettle and mix them to obtain a second mixed solution. Among them, a mechanical stirrer is connected above the double-layer glass reaction kettle, and the other two ports are respectively connected with a thermometer sleeve and a constant pressure dropping funnel.

[0058] Turn on the high and low temperature circulating all-in-one machine to cool down the double-layer glass reaction kettle. Start to cool down from room temperature at a rate gradient of 0.5 °C / min to -5 °C. After reaching -5 °C, start to dropwise add the first mixed solution. During the dropping process, keep the reaction system temperature less than 0 °C. After the dropping is completed, continue to keep the reaction system temperature at 0 °C for 2 h to make the reaction proceed fully.

[0059] Use a sand core G4 suction filtration device for suction filtration, transfer the separated filtrate to a rotary evaporation flask for rotary evaporation treatment, control the rotary evaporation oil bath temperature to be less than 100 °C to obtain 259.1 g of crude product, and then filter the obtained crude product in a glove box to remove the precipitated pyridine hydrochloride.

[0060] Put the filtered crude product in a reaction kettle, raise the temperature gradient, control the distillation head temperature at 120 °C, collect the early fractions, and weigh the product in the reaction kettle as 209.2 g.

[0061] Carry out two molecular distillation treatments on the product in the above reaction kettle in sequence. Among them, the first molecular distillation treatment: control the inlet and outlet temperatures at 50 °C and the scraper oil bath temperature at 80 °C to separate water and light components such as raw materials and solvents; the second molecular distillation treatment: control the inlet and outlet temperatures at 50 °C and the scraper oil bath temperature at 100 °C to obtain the heavy component, that is, obtain the vinyltris(2-cyanoethyl) silicate product, and weigh it as 180.95 g.

[0062] Comparative Example 1

[0063] The preparation method of vinyl tris(2-cyanoethyl) silicate in this comparative example includes the following steps:

[0064] Weigh the raw materials vinyl trichlorosilane, 3-hydroxypropionitrile and dimethyl carbonate respectively with an electronic balance in a glove box. All raw and auxiliary materials need to be dehydrated before use to ensure that the water content is less than 100 ppm. Among them, vinyl trichlorosilane is a commercially available product with a purity ≥ 99% and a water content < 100 ppm; dimethyl carbonate is a commercially available product with a purity ≥ 99% and a water content < 100 ppm; 3-hydroxypropionitrile is a commercially available industrial-grade product with a purity ≥ 99% and a water content < 100 ppm.

[0065] Place the weighed 161.49 g of vinyl trichlorosilane and 180.156 g of dimethyl carbonate (diluent) in a double-layer glass reaction kettle and mix them to obtain a first mixed solution.

[0066] Place the weighed 220.379 g of 3-hydroxypropionitrile and 540.468 g of dimethyl carbonate into a constant pressure dropping funnel and mix them to obtain a second mixed solution.

[0067] Connect a mechanical stirrer above the double-layer glass reaction kettle, and connect a thermometer sleeve and a constant pressure dropping funnel to the other two ports respectively. Start the high and low temperature circulating machine to cool the double-layer glass reaction kettle. Cool down from room temperature at a rate gradient of 0.5 °C / min to -5 °C. After reaching -5 °C, start to drop the second mixed solution. During the dropping process, keep the reaction system temperature less than 0 °C. After the dropping is completed, continue to keep the reaction system temperature at 0 °C for 2 h to make the reaction proceed fully.

[0068] Transfer the filtrate obtained after the full reaction to a rotary evaporation flask for rotary evaporation treatment. Control the rotary evaporation oil bath temperature to be less than 100 °C to obtain 259.1 g of crude product. Then filter the obtained crude product in a glove box to remove the precipitated pyridine hydrochloride.

[0069] Put the filtered crude product in a reaction kettle, raise the temperature gradient, control the distillation head temperature to be 120 °C, collect the early fractions, and weigh the product in the reaction kettle as 130.32 g.

[0070] Perform two molecular distillation treatments on the product in the above reaction kettle in sequence. Among them, the first molecular distillation treatment: control the inlet and outlet temperatures to be 50 °C, and the scraper oil bath temperature to be 80 °C to separate water and light components such as raw materials and solvents; the second molecular distillation treatment: control the inlet and outlet temperatures to be 50 °C, and the scraper oil bath temperature to be 100 °C to obtain the heavy component, that is, obtain the vinyl tris(2-cyanoethyl) silicate product, and weigh it as 121.93 g.

[0071] Comparative Example 2

[0072] The preparation method of vinyl tris(2-cyanoethyl) silicate in this comparative example includes the following steps:

[0073] Weigh the raw materials vinyl trichlorosilane, 3-hydroxypropionitrile, pyridine and dichloromethane separately with an electronic balance in a glove box. All raw and auxiliary materials need to be treated to remove water before use to ensure that the water content is less than 100 ppm. Among them, vinyl trichlorosilane is a commercially available product with a purity of ≥99% and a water content of <100 ppm; dichloromethane is a commercially available product with a purity of ≥99% and a water content of <100 ppm; 3-hydroxypropionitrile is a commercially available industrial-grade product with a purity of ≥99% and a water content of <100 ppm;

[0074] Place the weighed 161.49 g of vinyl trichlorosilane and 170 g of dichloromethane (diluent) in a constant-pressure dropping funnel and mix them to obtain a first mixture;

[0075] Add the weighed 223.934 g of 3-hydroxypropionitrile, 237.297 g of pyridine and 510 g of dichloromethane to a double-layer glass reaction kettle and mix them to obtain a second mixture. Among them, a mechanical stirrer is connected above the double-layer glass reaction kettle, and the other two ports are respectively connected to a thermometer sleeve and a constant-pressure dropping funnel;

[0076] Turn on the high and low temperature circulation all-in-one machine to cool down the double-layer glass reaction kettle. Start cooling from room temperature at a rate gradient of 0.5 °C / min to -5 °C. After reaching -5 °C, start dropping the first mixture. During the dropping process, keep the reaction system temperature below 0 °C. After the dropping is completed, continue to keep the reaction system temperature at 0 °C for 2 h to make the reaction proceed fully;

[0077] Use a sand core G4 suction filtration device for suction filtration, transfer the separated filtrate to a rotary evaporation flask for rotary evaporation treatment, control the rotary evaporation oil bath temperature below 100 °C to obtain 152.3 g of crude product, and then filter the obtained crude product in a glove box to remove the precipitated pyridine hydrochloride;

[0078] Put the filtered crude product in a reaction kettle, raise the temperature gradient, control the distillation head temperature at 120 °C, further remove the solvent dichloromethane and by-product pyridine hydrochloride, collect the preliminary distillate, and weigh the product in the reaction kettle as 100.4 g;

[0079] Carry out two molecular distillation treatments on the product in the above reaction kettle in sequence. Among them, the first molecular distillation treatment: control the inlet and outlet temperatures at 50 °C and the scraper oil bath temperature at 80 °C to separate water and light components such as raw materials and solvents; the second molecular distillation treatment: control the inlet and outlet temperatures at 50 °C and the scraper oil bath temperature at 100 °C to obtain a heavy component, that is, obtain vinyl tris(2-cyanoethyl) silicate product, and weigh it as 71.05 g.

[0080] The vinyltris(2-cyanoethyl) silicate prepared in Examples 1-2 and Comparative Examples 1-2 was quantitatively analyzed by gas chromatography. The results are shown in Table 1. The gas chromatograph model was Agilent 7890B. The method was as follows: the injection port was set at 300 °C, the column oven temperature was increased at a rate of 10 °C / min from an initial temperature of 50 °C to 260 °C and held for 15 min; the front FID temperature was set at 300 °C.

[0081] Table 1 Test results of vinyltris(2-cyanoethyl) silicate obtained in Examples 1-2 and Comparative Examples 1-2

[0082] Group Content (%) Example 1 99.430 Example 2 99.471 Comparative Example 1 89.828 Comparative Example 2 70.153

[0083] As can be seen from the above, compared with Example 1, pyridine was not added in Comparative Example 1, the acidity of the reaction system was too high, and the purity of the obtained product was not high and the yield was low. The reaction liquid phase system of Comparative Example 2 was dichloromethane, and the reaction liquid phase system of Example 2 was dimethyl carbonate. In polar aprotic solvents, the product had a lower solubility in the dimethyl carbonate solvent with a lower dielectric parameter, which was beneficial to obtaining a product with high purity. In summary, the content of vinyltris(2-cyanoethyl) silicate obtained by using the preparation method of the present invention in Examples 1 and 2 was significantly higher than that in Comparative Examples 1 and 2.

[0084] For the vinyltris(2-cyanoethyl) silicate obtained in Example 1, the functional groups were determined according to the peak positions of the infrared spectrum. The 1H NMR spectrum was used to infer the types of hydrogen atoms, the chemical environments in which they were located, and the connection modes between them by the positions (chemical shifts) of the peaks in the spectrum, the splitting conditions of the peaks (coupling constants), and the peak areas, so as to determine the molecular structure of the organic compound, and gas chromatography was used to quantitatively characterize the product purity. The characterization results of the infrared spectrum diagram of Example 1 are as shown in Figure 1 the attached Figure 2 and the characterization results of the 1H NMR spectrum diagram are as shown in Figure 3 the attached Figure 4 and

[0085] From Figure 1 it can be seen that the peak positions correspond to the positions of the main functional groups: 2800-2961 cm -1 , alkene alkanes (=CH2, CH2); 2150-2280 cm -1 , cyano group (C≡N); 1400-1667 cm -1 , pyridine; 1060-1092 cm -1 , Si-O-C stretching vibration doublet; 933-965 cm -1 , symmetric Si-O-C stretching vibration. The characteristic peaks of the functional groups contained in the target product vinyltris(2-cyanoethyl) silicate can all be found in the Figure 1 infrared spectrum diagram.

[0086] As shown by the 1H NMR spectrum of Figure 2 Figure 2 , the chemical shift of the hydrogen atom connected to the double bond is generally around 4.0 - 4.5 ppm. The chemical shift of the vinyl hydrogen in vinyl tris(2-cyanoethyl) silicate is within this range; the cyano group (-CN) is an electron-withdrawing group, which will shift the chemical shift of the adjacent hydrogen atom to the low field. Usually, the chemical shift of the methylene hydrogen connected to the cyano group is around 2 - 3 ppm. In the cyanoethyl group, due to the electron-withdrawing effect of the cyano group, the chemical shift of the methylene hydrogen will be at the high field end of this range, around 2.5 - 2.8 ppm, which is consistent with the chemical shift of H in vinyl tris(2-cyanoethyl) silicate fitted by the commonly used professional chemical drawing software, proving that the target structure product vinyl tris(2-cyanoethyl) silicate is synthesized by the preparation method of the present invention.

[0087] The gas chromatogram of vinyl tris(2-cyanoethyl) silicate in Example 1 is as shown in Attachment Figure 3 shown, and the enlarged view is as shown in Attachment Figure 4 shown. The gas chromatography quantitative test results are shown in Table 2. As can be seen from Table 2 below, for vinyl tris(2-cyanoethyl) silicate at 26.848 min, the peak area is 2071.3, the peak height is 313.2, the peak width is 0.0836, the peak area percentage is 99.430%, and the symmetry factor is 5.576; at 26.982 min, the peak area is 11.9, the peak height is 3.6, the peak width is 0.0508, the peak area percentage is 0.570%, and the symmetry factor is 0.996.

[0088] Table 2 Gas Chromatography Quantitative Test Results of Vinyl Tris(2-cyanoethyl) Silicate in Example 1

[0089] Serial Number Time Type Type Area Height Width Area% Peak Area% Symmetry 1 26.848 BB BB 2071.3 313.2 0.0836 99.430 99.430 5.576 2 26.982 BB BB 11.9 3.6 0.0508 0.570 0.570 0.996

[0090] Finally, it should be noted that: The present invention is not limited to the above-listed embodiments. The above are only preferred and feasible embodiments of the present invention. Moreover, the above-described embodiments are only used to illustrate the technical solutions of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations, modifications, evolutions, and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A vinyl tris(2-cyanoethyl) silicate, characterized in that, It has the following structural formula:

2. The preparation method of vinyltris(2-cyanoethyl) silicate according to claim 1, characterized in that, It includes the following steps: adding a mixed solution of vinyltrichlorosilane and a second organic solvent to a mixed solution of 3-hydroxypropionitrile, an organic base, and a first organic solvent, and after the dropping is completed, performing purification treatment to obtain vinyl tris(2-cyanoethyl) silicate; Among them, the molar ratio of 3-hydroxypropionitrile, vinyltrichlorosilane to the organic base is (3.0 - 3.3):1:

3.

3. The preparation method of vinyltris(2-cyanoethyl) silicate according to claim 2, wherein, Both the first organic solvent and the second organic solvent include at least one of chain carbonates, carboxylic acid esters, ethers, and nitriles.

4. The preparation method of vinyl tris(2-cyanoethyl) silicate according to claim 3, characterized in that, The chain carbonates include at least one of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

5. The preparation method of vinyl tris(2-cyanoethyl) silicate according to claim 2, characterized in that, The organic base includes at least one of pyridine, triethylamine, and sodium tert-butoxide.

6. The preparation method of vinyltris(2-cyanoethyl) silicate according to claim 2, characterized in that, The step of adding a mixed solution of vinyltrichlorosilane and a second organic solvent to a mixed solution of 3-hydroxypropionitrile, an organic base, and a first organic solvent specifically includes the following steps: Slowly drop a mixed solution of vinyltrichlorosilane and a second organic solvent into a mixed solution of 3-hydroxypropionitrile, an organic base, and a first organic solvent. After the dropping is completed, continue the reaction for 1 h - 3 h. Among them, the temperature of the reaction system during the dropping and the continued reaction is less than 0 °C, and the starting temperature of the dropping is -5 °C.

7. The preparation method of vinyl tris(2-cyanoethyl) silicate according to claim 2, characterized in that, Adding a mixed solution of vinyltrichlorosilane and a second organic solvent to a mixed solution of 3-hydroxypropionitrile, an organic base, and a first organic solvent is carried out in a glove box or a drying room, and the environmental dew point is controlled below -60 °C.

8. The preparation method of vinyltris(2-cyanoethyl) silicate according to claim 2, characterized in that, The purification treatment step includes the following steps: Perform suction filtration using a suction filtration device. After subjecting the separated filtrate to rotary evaporation, perform vacuum distillation, and then obtain vinyl tris(2-cyanoethyl) silicate through molecular distillation.

9. The preparation method of vinyl tris(2-cyanoethyl) silicate according to claim 8, characterized in that, In the vacuum distillation step, control the temperature of the distillation head to be 100 °C - 130 °C.

10. The preparation method of vinyl tris(2-cyanoethyl) silicate according to claim 8, characterized in that, The molecular distillation step specifically includes the following steps: Perform the first molecular distillation treatment on the product obtained by vacuum distillation treatment, control both the inlet and outlet temperatures to be 50 °C, and the temperature of the scraper oil bath to be 70 - 90 °C; Perform the second molecular distillation treatment on the product obtained by the first molecular distillation treatment, control both the inlet and outlet temperatures to be 50 °C, and the temperature of the scraper oil bath to be 90 - 105 °C to obtain vinyl tris(2-cyanoethyl) silicate.

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