Efficient synthesis process of high-hydrogen-content silicone oil

Abstract

The invention relates to the technical field of organic silicon materials, in particular to an efficient synthesis process of high-hydrogen-content silicone oil. The process comprises the following steps: firstly, mixing and filtering methyl hydrogen ring body and hexamethyldisiloxane in an inert atmosphere to prepare a refined raw material solution, and then dispersing a special and magnetically separable sulfonic acid carbon-silicon composite solid acid catalyst into part of the raw material solution to form a stable suspension; and pumping the mixture and the residual raw material solution into a micro-channel reactor for ring-opening polymerization and equilibrium reaction, and then carrying out three-stage gradient vacuum low-temperature removal purification. According to the process, Si-H bond side reaction is effectively inhibited, efficient magnetic separation and recovery of the catalyst are achieved, and the obtained product is high in hydrogen content, narrow in molecular weight distribution, light in color, good in stability and suitable for high-end application.

Description

Technical Field

[0001] This invention relates to the field of organosilicon materials technology, specifically to a high-efficiency synthesis process for high-hydrogen-content silicone oil. Background Technology

[0002] High-hydrogen-content silicone oil, also known as polymethylhydrosiloxane with high active hydrogen content, is a key intermediate in organosilicon material systems. Its molecular backbone or side chains are rich in highly reactive Si-H bonds, playing an irreplaceable role in textile finishing agents, paper release agents, silicone rubber crosslinking agents, surface hydrophobic treatments, and the synthesis of various functional organosilicones. Currently, the mainstream industrial method for synthesizing high-hydrogen-content silicone oil typically uses methylhydrocyclic compounds and end-capping agents, such as hexamethyldisiloxane, as raw materials, undergoing ring-opening polymerization and equilibrium reactions under acidic or alkaline catalysts.

[0003] However, this traditional process faces a series of interconnected technical challenges in pursuing high efficiency, high quality, and green and safe production. First, the Si-H bond is chemically reactive and prone to rearrangement, oxidation, and hydrolysis under strong acid (such as concentrated sulfuric acid) or strong base (such as KOH) catalysis and at high temperatures. This not only leads to a decrease in the hydrogen content of the target product but may also trigger molecular chain cross-linking, resulting in gelation or the formation of low-molecular-weight cyclic byproducts, thus widening the molecular weight distribution and reducing uniformity of the product. Second, although traditional homogeneous catalysts have high activity, they are difficult to completely separate from high-viscosity products. Trace residues continue to catalyze side reactions, causing the product to darken in color, decrease in hydrogen content, or even gel during storage, severely affecting its application performance and stability. Furthermore, traditional batch reactor reactions suffer from uneven mixing and low mass and heat transfer efficiency. Local overheating or uneven material concentration can exacerbate side reactions and pose safety risks, such as the release of hydrogen gas from the reaction of Si-H bonds with trace amounts of moisture. Finally, post-reaction processing, such as vacuum distillation to remove low-boiling substances, is usually energy-intensive and time-consuming, and the high-temperature environment may further damage the Si-H bonds, affecting the quality of the final product.

[0004] Chinese patent publication number CN112679736B discloses a phenyl-containing hydrogen silicone oil and its preparation method. Specifically, the method for preparing phenyl-containing hydrogen silicone oil includes the following steps: reacting a siloxane-based raw material required for the reaction with a capping agent in the presence of a heteropolyacid catalyst. The heteropolyacid catalyst is obtained by supporting phosphomolybdic heteropolyacid on attapulgite. By using a heteropolyacid catalyst as the catalyst for the synthesis reaction, phenyl-containing hydrogen silicone oil can be synthesized under mild reaction conditions, which is beneficial for energy saving and consumption reduction. Furthermore, it avoids the use of neutralizing agents, simplifies the operation process, and reduces preparation costs. In addition, this method can improve the yield and quality of phenyl-containing hydrogen silicone oil. The phenyl-containing hydrogen silicone oil obtained by this method has a high yield and low viscosity. However, this technical solution focuses on phenyl-containing hydrogen silicone oil, and the introduced phenyl structure changes the basic physicochemical properties of the product, resulting in differences in application scenarios and performance indicators compared to the general-purpose high-hydrogen-content silicone oil targeted by this invention. Summary of the Invention

[0005] The purpose of this invention is to provide an efficient synthesis process for high-hydrogen-content silicone oil, in order to solve the problems mentioned in the background art, such as the easy destruction of Si-H bonds, catalyst residue leading to product instability, and low mass and heat transfer efficiency in the traditional synthesis process of high-hydrogen-content silicone oil.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A highly efficient synthesis process for high-hydrogen-content silicone oil includes the following steps: Step S1: By weight, 80-95 parts of methylhydrocyclic compound and 5-20 parts of hexamethyldisiloxane are stirred and mixed at 25-35°C under an inert atmosphere to form a raw material premix. The premix is ​​filtered through a 0.15-0.25μm polytetrafluoroethylene filter membrane to obtain a refined raw material liquid, which is stored in a pressurized raw material tank. Step S2: The sulfonic acid-silicon composite solid acid catalyst is dispersed in a portion of the refined raw material liquid obtained in step S1 to form a stable suspension. The mass fraction of the solid acid catalyst in the stable suspension is 5% to 15%. The remaining refined raw material liquid and the stable suspension are pumped into the Y-type static mixing unit at the front end of the microchannel reactor at a flow ratio of 10:1 to 30:1, respectively, synchronously and continuously. In the microchannel reactor, the material undergoes ring-opening polymerization and equilibrium reaction at a temperature of 40 to 70°C and a residence time of 10 to 30 minutes to obtain the crude product. Step S3: After the crude product obtained in step S2 is magnetically separated to recover the sulfonic acid carbon silicon composite solid acid catalyst, it enters the low temperature gradient de-oxidation system to remove unreacted monomers and oligomers under the conditions of absolute pressure of 100~500Pa and temperature range of 60~100℃, so as to obtain the high hydrogen content silicone oil product.

[0007] This invention achieves efficient and stable synthesis of high-hydrogen-content silicone oil through the synergistic process of three stages: refined raw materials, continuous polymerization in a microreactor, and gradient de-oxidation. Raw material premixing and filtration ensure the reaction system is free of impurities and solid particles, preventing microchannel blockage and side reactions. An inert atmosphere prevents the hydrolysis or oxidative damage of Si-H bonds by moisture and oxygen. The methyl hydrogen cyclic compound, as the main chain component and active hydrogen source, is essential for obtaining high-hydrogen-content products due to its high proportion. Hexamethyldisiloxane acts as a capping agent to precisely regulate molecular weight; exceeding the specified ratio will result in insufficient hydrogen content or uncontrolled molecular weight in the product. The microchannel reactor, with its high specific surface area, enables rapid mass and heat transfer, allowing ring-opening polymerization and equilibration reactions to proceed under uniform low-temperature conditions. This suppresses high-temperature rearrangement and cross-linking of Si-H bonds, among other side reactions. The catalyst is fed separately from the raw materials in slurry form, avoiding microchannel blockage and achieving precise control and real-time mixing of the catalyst amount. Subsequent magnetic separation enables catalyst recycling, while gradient desorption removes low-molecular-weight substances with different boiling points in stages at low temperatures through gradual heating and depressurization, avoiding the destruction of Si-H bonds caused by a single high-temperature, high-vacuum process. Throughout the entire process, the proportions of each component, the temperature, pressure, and fluid parameters at each stage are all systematically coordinated, achieving continuous preparation of highly active, narrowly distributed, and stable high-hydrogen-content silicone oil.

[0008] Preferably, in step S1, the methylhydrocyclotetrasiloxane is a mixture of octamethylcyclotetrasiloxane and tetramethyltetrahydrocyclotetrasiloxane, wherein the mass percentage of tetramethyltetrahydrocyclotetrasiloxane is 85% to 95%.

[0009] By controlling the mass percentage of tetramethyltetrahydrocyclotetrasiloxane in the methylhydrocyclotetrasiloxane to be 85%–95%, a sufficiently high Si-H bond content is ensured in the product, meeting the basic requirements for its use as a highly efficient crosslinking agent or modification intermediate. Simultaneously, the introduction of 5%–15% octamethylcyclotetrasiloxane as a regulating component dilutes the local concentration of Si-H bonds within the reaction system, thereby suppressing side reactions caused by the proximity of Si-H bonds and improving reaction selectivity and product storage stability. Furthermore, octamethylcyclotetrasiloxane can also adjust the polymer's molecular weight and optimize its chain structure, preventing the product from becoming too hard or too viscous due to excessive crosslinking. Ultimately, while maintaining high activity, the high-hydrogen-content silicone oil achieves excellent comprehensive application performance.

[0010] Preferably, in step S1, the inert atmosphere is high-purity nitrogen or argon, with a water content of less than 10 ppm and an oxygen content of less than 5 ppm; the stirring speed of the premixed reaction liquid is 300~600 rpm, and the time is 10~30 min.

[0011] Preferably, in step S2, the preparation method of the sulfonate-carbon-silicon composite solid acid catalyst includes the following steps: Step (1): Dissolve glucose, tetraethyl orthosilicate and hexadecyltrimethylammonium bromide in an ethanol-water mixture with a volume ratio of 2:1 to 3:1 by mass (10~20):1:(0.35~0.70) and stir at 60~80℃ for 12~24h to carry out simultaneous hydrothermal carbonization and silica sol-gel process. Subsequently, the mixture was transferred to a high-pressure reactor and hydrothermally reacted at 180-200℃ for 6-12 hours. After cooling to 25-35℃, it was centrifuged at 8000-12000 rpm for 10-20 minutes to collect the solid precipitate. Then, it was washed and purified by alternating ethanol and deionized water to redisperse the solid precipitate in the washing solution at a solid-liquid ratio of 1:10-1:20. After ultrasonic dispersion, it was centrifuged again. This process was repeated 3-4 times. Finally, the washed wet solid was placed in a vacuum drying oven at 80-100℃ and dried for 12-24 hours to obtain the carbon / silica composite microsphere precursor. Step (2): The precursor obtained in step (1) is heated to 550-650°C at a heating rate of 2-3°C / min under an inert atmosphere such as high-purity nitrogen or argon, and held at the temperature for 4-6 hours to carbonize and remove hexadecyltrimethylammonium bromide, forming a carbon / silica composite carrier. Step (3): The carbon / silica composite carrier obtained in step (2) is dispersed in a 1.0~3.0 mol / L concentrated sulfuric acid-dichloroethane solution under nitrogen protection and mechanical stirring. The mass-volume ratio of the carbon / silica composite carrier to the concentrated sulfuric acid-dichloroethane solution is 1g:(20~30)mL. The mixture is refluxed at 60~80℃ for 6~12h. After the reaction is completed, the mixture is cooled and 10~15 times the amount of ice water is poured in. The mixture is stirred vigorously to quench the reaction and dilute the concentrated sulfuric acid. The mixture is centrifuged at 8000~10000 rpm for 10~15min to collect the solid. The solid is then washed repeatedly with a large amount of deionized water. The pH of the filtrate is monitored in real time until it stabilizes at 6.5~7.5 as the washing endpoint. Finally, the wet solid filter cake is placed in a vacuum drying oven and dried at 60~70℃ for 6~8h. Then the temperature is raised to 80~90℃ and dried for another 8~12h to obtain the sulfonated carrier powder. Step (4): Disperse the sulfonated support obtained in step (3) in anhydrous ethanol at a solid-liquid ratio of 1g:(20~30)mL, add iron oxide nanoparticles with an average particle size of 10~30nm and a mass of 5%~15% of the total mass of the final catalyst, and then perform ultrasonic treatment with a power of 300~500W for 20~30min to achieve initial uniform dispersion. Next, the mixture was continuously reacted at 60-80℃ with a mechanical stirring speed of 300-500 rpm for 2-4 hours, so that the Fe-OH groups on the surface of the iron oxide nanoparticles and the Si-OH groups on the surface of the sulfonated support would undergo a condensation reaction to form Si-O-Fe covalent bonds, thereby achieving a strong chemical bond. After the reaction was completed, magnetic separation was performed under a magnetic field strength of 0.3-0.8T, and the supernatant was quickly removed. The separated solid was washed 3-5 times each with anhydrous ethanol and deionized water to remove physically adsorbed impurities. Finally, the washed solid was dried in a vacuum environment at 60-80℃ for 8-12 hours to obtain a pure sulfonated carbon silicon composite solid acid catalyst.

[0012] Preferably, in step S2, the specific surface area of ​​the sulfonate-carbon silicon composite solid acid catalyst is 500~800 m². 2 / g, with a sulfonic acid group loading of 1.5~2.5mmol / g.

[0013] The high specific surface area provides a large accessible interface for the reactants, ensuring high catalytic efficiency, which is beneficial for suppressing side reactions and improving selectivity. Meanwhile, the high density of sulfonic acid groups directly provides active sites, guaranteeing strong catalytic activity. The combination of these three factors enables the catalyst to achieve rapid adsorption, diffusion, and transformation of reactant molecules in the microreaction system, thereby driving the efficient and highly selective ring-opening polymerization and equilibrium reaction of siloxanes under mild conditions.

[0014] Preferably, in step S2, the microchannel reactor is made of stainless steel, with an inner diameter of 0.5~2.0 mm, a channel length of 5~20 m, an operating pressure of 0.1~0.5 MPa, and a Reynolds number of 100~500 for the reaction liquid in the microchannel reactor.

[0015] Preferably, in step S3, the magnetic field strength used for magnetic separation is 0.3~0.8T, and the separation time is 2~5min.

[0016] Preferably, in step S3, the low-temperature gradient descaling system consists of three short-range molecular distillers connected in series. The first-stage system has a temperature of 60-70°C and an absolute pressure of 400-500 Pa; the second-stage system has a temperature of 75-85°C and an absolute pressure of 300-350 Pa; and the third-stage system has a temperature of 90-100°C and an absolute pressure of 100-150 Pa. The first, second, and third-stage distillers are connected sequentially through insulated pipes, and the crude product flows through each stage by gravity due to the internal pressure difference. Each stage distiller is equipped with a scraped film rotor with a rotation speed of 200-400 rpm to ensure that the high-viscosity material forms a uniform liquid film on the heating surface.

[0017] This gradient process protects the heat-sensitive Si-H bonds in the product, avoiding the damage to Si-H bonds, cross-linking of the product, or darkening of color that may occur with traditional one-time high-temperature, high-vacuum desorption. At the same time, the step-by-step operation is more energy-efficient and can achieve graded recovery and recycling of unreacted monomers through stepwise condensation, thereby improving product purity and stability while optimizing process greening and economic benefits.

[0018] Preferably, in step S3, the outlet of the low-temperature gradient de-cooling system is connected to a cold trap, and the temperature of the cold trap is -40~-20℃.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention solves the problem of catalysts being difficult to separate from high-viscosity products and causing product instability by using a magnetic solid acid catalyst composed of a sulfonated silicon carbide composite support and iron oxide to replace traditional strong acid or strong base homogeneous catalysts. At the same time, by controlling the proportion of tetramethyltetrahydrocyclotetrasiloxane in the methyl hydrogen ring to 85% to 95%, while ensuring a high hydrogen content in the product, an appropriate amount of octamethylcyclotetrasiloxane is used to adjust the reaction activity and molecular chain structure, thereby suppressing side reactions and gelation tendency caused by excessively high local concentration of Si-H bonds.

[0020] 2. This invention employs a microchannel reactor to achieve continuous and instantaneous mixing and reaction of raw materials and catalyst slurry. Its extremely high mass and heat transfer efficiency eliminates localized overheating and concentration inconsistencies found in traditional batch reactors, allowing ring-opening polymerization and equilibration reactions to proceed uniformly under precise low-temperature conditions. This effectively suppresses the rearrangement and decomposition of Si-H bonds at high temperatures. After the reaction, the catalyst is efficiently recovered through magnetic separation, and a three-stage gradient heating and step-depressurization process is used to remove components of different volatility under mild conditions, avoiding the damage to Si-H bonds caused by high-temperature, high-vacuum desorption. This ensures high hydrogen content while yielding products with a narrower molecular weight distribution and better storage stability. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present application.

[0022] Example 1 The methylhydrocyclotetrasiloxane is a mixture of octamethylcyclotetrasiloxane and tetramethyltetrahydrocyclotetrasiloxane, wherein tetramethyltetrahydrocyclotetrasiloxane accounts for 90% by mass.

[0023] The preparation method of the sulfonate-carbon-silicon composite solid acid catalyst includes the following steps: Step (1): Glucose, tetraethyl orthosilicate, and hexadecyltrimethylammonium bromide were dissolved in an ethanol-water mixture at a mass ratio of 15:1:0.50 and stirred at 60°C for 16 h to carry out simultaneous hydrothermal carbonization and silica sol-gel process. Subsequently, the mixture was transferred to a high-pressure reactor and hydrothermally reacted at 200°C for 10 h. After cooling to 25°C, the solid precipitate was collected by centrifugation at 8000 rpm for 15 min. Then, the solid precipitate was washed and purified by alternating ethanol and deionized water in the washing solution at a solid-liquid ratio of 1:10. After ultrasonic dispersion, the solid precipitate was centrifuged again. This process was repeated 3 times. Finally, the washed wet solid was dried in a vacuum drying oven at 100°C for 20 h to obtain the carbon / silica composite microsphere precursor. Step (2): The precursor obtained in step (1) is heated to 600°C at a heating rate of 2°C / min under high-purity nitrogen and held at the temperature for 4 hours to carbonize and remove hexadecyltrimethylammonium bromide, forming a carbon / silica composite carrier. Step (3): The carbon / silica composite carrier obtained in step (2) was dispersed in a 3.0 mol / L concentrated sulfuric acid-dichloroethane solution under nitrogen protection and mechanical stirring. The mass-volume ratio of the carbon / silica composite carrier to the concentrated sulfuric acid-dichloroethane solution was 1 g: 20 mL. The mixture was refluxed at 80 °C for 10 h. After the reaction was completed, the mixture was cooled and 10 times the amount of ice water was poured in. The mixture was stirred vigorously to quench the reaction and dilute the concentrated sulfuric acid. The mixture was centrifuged at 10,000 rpm for 15 min to collect the solid. The solid was then washed repeatedly with a large amount of deionized water. The pH of the filtrate was monitored in real time until it stabilized at 7.0 as the washing endpoint. Finally, the wet solid filter cake was placed in a vacuum drying oven and dried at 70 °C for 6 h. Then the temperature was raised to 90 °C and dried for another 10 h to obtain the sulfonated carrier powder. Step (4): The sulfonated support obtained in step (3) was dispersed in anhydrous ethanol at a solid-liquid ratio of 1g:30mL. Ferric oxide nanoparticles with an average particle size of 10nm and a mass of 10% of the total final catalyst mass were added. The mixture was then subjected to ultrasonic treatment at 500W for 30min to achieve initial uniform dispersion. Next, the mixture was continuously stirred at 400rpm at 60℃ for 3h to allow the Fe-OH groups on the surface of the ferric oxide nanoparticles to undergo a condensation reaction with the Si-OH groups on the surface of the sulfonated support. After the reaction, magnetic separation was performed under a magnetic field strength of 0.5T. The supernatant was quickly removed, and the separated solid was washed four times each with anhydrous ethanol and deionized water to remove physically adsorbed impurities. Finally, the washed solid was dried in a vacuum environment at 60℃ for 10h to obtain a pure solid with a specific surface area of ​​600m². 2 A sulfonic acid-carbon silicon composite solid acid catalyst with a loading of 2.0 mmol / g of sulfonic acid groups.

[0024] A highly efficient synthesis process for high-hydrogen-content silicone oil includes the following steps: Step S1: By mass, 90 parts of methylhydrocyclic compound and 15 parts of hexamethyldisiloxane are mixed in high-purity nitrogen with a water content of 8 ppm and an oxygen content of 3 ppm at 25°C and a stirring speed of 400 rpm for 20 min to form a raw material premix. The premix is ​​then filtered through a 0.20 μm polytetrafluoroethylene filter membrane to obtain a refined raw material liquid, which is stored in a pressurized raw material tank. Step S2: The sulfonic acid-silicon carbide composite solid acid catalyst is dispersed in a portion of the purified raw material liquid obtained in step S1 to form a stable suspension. The mass fraction of the solid acid catalyst in the stable suspension is 10%. The remaining purified raw material liquid and the stable suspension are pumped into the Y-type static mixing unit at the front end of a stainless steel microchannel reactor with an inner diameter of 1.0 mm, a channel length of 10 m, and an operating pressure of 0.5 MPa, respectively, synchronously and continuously, at a flow ratio of 20:1. The Reynolds number of the reaction liquid in the microchannel reactor is 400. In the microchannel reactor, the material undergoes ring-opening polymerization and equilibrium reaction at a temperature of 60 °C and a residence time of 20 min to obtain the crude product. Step S3: The crude product obtained in step S2 is subjected to magnetic separation to recover the sulfonic acid-carbon silicon composite solid acid catalyst at a magnetic field strength of 0.5T and a separation time of 3min. Then, it enters a low-temperature gradient de-oxidation system consisting of a three-stage series system with a temperature of 70℃ and an absolute pressure of 500Pa in the first stage distillation unit, a temperature of 85℃ and an absolute pressure of 350Pa in the second stage distillation unit, and a temperature of 100℃ and an absolute pressure of 150Pa in the third stage distillation unit. The three stage distillations are connected by insulated pipes. The crude product flows by gravity through the outlets of each stage by the internal pressure difference of the system. Each stage distillation unit is equipped with a scraper rotor with a rotation speed of 300 rpm. The outlet is connected to a cold trap with a temperature of -20℃ to remove unreacted monomers and oligomers, resulting in a high-hydrogen-content silicone oil product.

[0025] Example 2 The methylhydrocyclotetrasiloxane is a mixture of octamethylcyclotetrasiloxane and tetramethyltetrahydrocyclotetrasiloxane, wherein tetramethyltetrahydrocyclotetrasiloxane accounts for 90% by mass.

[0026] The preparation method of the sulfonate-carbon-silicon composite solid acid catalyst includes the following steps: Step (1): Glucose, tetraethyl orthosilicate, and hexadecyltrimethylammonium bromide were dissolved in an ethanol-water mixture at a mass ratio of 15:1:0.50 and stirred at 60°C for 16 h to carry out simultaneous hydrothermal carbonization and silica sol-gel process. Subsequently, the mixture was transferred to a high-pressure reactor and hydrothermally reacted at 200°C for 10 h. After cooling to 25°C, the solid precipitate was collected by centrifugation at 8000 rpm for 15 min. Then, the solid precipitate was washed and purified by alternating ethanol and deionized water in the washing solution at a solid-liquid ratio of 1:10. After ultrasonic dispersion, the solid precipitate was centrifuged again. This process was repeated 3 times. Finally, the washed wet solid was dried in a vacuum drying oven at 100°C for 20 h to obtain the carbon / silica composite microsphere precursor. Step (2): The precursor obtained in step (1) is heated to 600°C at a heating rate of 2°C / min under high-purity nitrogen and held at the temperature for 4 hours to carbonize and remove hexadecyltrimethylammonium bromide, forming a carbon / silica composite carrier. Step (3): The carbon / silica composite carrier obtained in step (2) was dispersed in a 3.0 mol / L concentrated sulfuric acid-dichloroethane solution under nitrogen protection and mechanical stirring. The mass-volume ratio of the carbon / silica composite carrier to the concentrated sulfuric acid-dichloroethane solution was 1 g: 20 mL. The mixture was refluxed at 80 °C for 10 h. After the reaction was completed, the mixture was cooled and 10 times the amount of ice water was poured in. The mixture was stirred vigorously to quench the reaction and dilute the concentrated sulfuric acid. The mixture was centrifuged at 10,000 rpm for 15 min to collect the solid. The solid was then washed repeatedly with a large amount of deionized water. The pH of the filtrate was monitored in real time until it stabilized at 7.0 as the washing endpoint. Finally, the wet solid filter cake was placed in a vacuum drying oven and dried at 70 °C for 6 h. Then the temperature was raised to 90 °C and dried for another 10 h to obtain the sulfonated carrier powder. Step (4): The sulfonated support obtained in step (3) was dispersed in anhydrous ethanol at a solid-liquid ratio of 1g:30mL. Ferric oxide nanoparticles with an average particle size of 10nm and a mass of 10% of the total final catalyst mass were added. The mixture was then subjected to ultrasonic treatment at 500W for 30min to achieve initial uniform dispersion. Next, the mixture was continuously stirred at 400rpm at 60℃ for 3h to allow the Fe-OH groups on the surface of the ferric oxide nanoparticles to undergo a condensation reaction with the Si-OH groups on the surface of the sulfonated support. After the reaction, magnetic separation was performed under a magnetic field strength of 0.5T. The supernatant was quickly removed, and the separated solid was washed four times each with anhydrous ethanol and deionized water to remove physically adsorbed impurities. Finally, the washed solid was dried in a vacuum environment at 60℃ for 10h to obtain a pure solid with a specific surface area of ​​600m². 2 A sulfonic acid-carbon silicon composite solid acid catalyst with a loading of 2.0 mmol / g of sulfonic acid groups.

[0027] A highly efficient synthesis process for high-hydrogen-content silicone oil includes the following steps: Step S1: By weight, 80 parts of methylhydrocyclic compound and 5 parts of hexamethyldisiloxane are mixed in high-purity nitrogen with a water content of 8 ppm and an oxygen content of 3 ppm at 25°C and a stirring speed of 400 rpm for 20 min to form a raw material premix. The premix is ​​then filtered through a 0.20 μm polytetrafluoroethylene filter membrane to obtain a refined raw material liquid, which is stored in a pressurized raw material tank. Step S2: The sulfonic acid-silicon carbide composite solid acid catalyst is dispersed in a portion of the purified raw material liquid obtained in step S1 to form a stable suspension. The mass fraction of the solid acid catalyst in the stable suspension is 10%. The remaining purified raw material liquid and the stable suspension are pumped into the Y-type static mixing unit at the front end of a stainless steel microchannel reactor with an inner diameter of 1.0 mm, a channel length of 10 m, and an operating pressure of 0.5 MPa, respectively, synchronously and continuously, at a flow ratio of 20:1. The Reynolds number of the reaction liquid in the microchannel reactor is 400. In the microchannel reactor, the material undergoes ring-opening polymerization and equilibrium reaction at a temperature of 60 °C and a residence time of 20 min to obtain the crude product. Step S3: The crude product obtained in step S2 is subjected to magnetic separation to recover the sulfonic acid-carbon silicon composite solid acid catalyst at a magnetic field strength of 0.5T and a separation time of 3min. Then, it enters a low-temperature gradient de-oxidation system consisting of a three-stage series system with a temperature of 70℃ and an absolute pressure of 500Pa in the first stage distillation unit, a temperature of 85℃ and an absolute pressure of 350Pa in the second stage distillation unit, and a temperature of 100℃ and an absolute pressure of 150Pa in the third stage distillation unit. The three stage distillations are connected by insulated pipes. The crude product flows by gravity through the outlets of each stage by the internal pressure difference of the system. Each stage distillation unit is equipped with a scraper rotor with a rotation speed of 300 rpm. The outlet is connected to a cold trap with a temperature of -20℃ to remove unreacted monomers and oligomers, resulting in a high-hydrogen-content silicone oil product.

[0028] Example 3 The methylhydrocyclotetrasiloxane is a mixture of octamethylcyclotetrasiloxane and tetramethyltetrahydrocyclotetrasiloxane, wherein tetramethyltetrahydrocyclotetrasiloxane accounts for 90% by mass.

[0029] The preparation method of the sulfonate-carbon-silicon composite solid acid catalyst includes the following steps: Step (1): Glucose, tetraethyl orthosilicate, and hexadecyltrimethylammonium bromide were dissolved in an ethanol-water mixture at a mass ratio of 15:1:0.50 and stirred at 60°C for 16 h to carry out simultaneous hydrothermal carbonization and silica sol-gel process. Subsequently, the mixture was transferred to a high-pressure reactor and hydrothermally reacted at 200°C for 10 h. After cooling to 25°C, the solid precipitate was collected by centrifugation at 8000 rpm for 15 min. Then, the solid precipitate was washed and purified by alternating ethanol and deionized water in the washing solution at a solid-liquid ratio of 1:10. After ultrasonic dispersion, the solid precipitate was centrifuged again. This process was repeated 3 times. Finally, the washed wet solid was dried in a vacuum drying oven at 100°C for 20 h to obtain the carbon / silica composite microsphere precursor. Step (2): The precursor obtained in step (1) is heated to 600°C at a heating rate of 2°C / min under high-purity nitrogen and held at the temperature for 4 hours to carbonize and remove hexadecyltrimethylammonium bromide, forming a carbon / silica composite carrier. Step (3): The carbon / silica composite carrier obtained in step (2) was dispersed in a 3.0 mol / L concentrated sulfuric acid-dichloroethane solution under nitrogen protection and mechanical stirring. The mass-volume ratio of the carbon / silica composite carrier to the concentrated sulfuric acid-dichloroethane solution was 1 g: 20 mL. The mixture was refluxed at 80 °C for 10 h. After the reaction was completed, the mixture was cooled and 10 times the amount of ice water was poured in. The mixture was stirred vigorously to quench the reaction and dilute the concentrated sulfuric acid. The mixture was centrifuged at 10,000 rpm for 15 min to collect the solid. The solid was then washed repeatedly with a large amount of deionized water. The pH of the filtrate was monitored in real time until it stabilized at 7.0 as the washing endpoint. Finally, the wet solid filter cake was placed in a vacuum drying oven and dried at 70 °C for 6 h. Then the temperature was raised to 90 °C and dried for another 10 h to obtain the sulfonated carrier powder. Step (4): The sulfonated support obtained in step (3) was dispersed in anhydrous ethanol at a solid-liquid ratio of 1g:30mL. Ferric oxide nanoparticles with an average particle size of 10nm and a mass of 10% of the total final catalyst mass were added. The mixture was then subjected to ultrasonic treatment at 500W for 30min to achieve initial uniform dispersion. Next, the mixture was continuously stirred at 400rpm at 60℃ for 3h to allow the Fe-OH groups on the surface of the ferric oxide nanoparticles to undergo a condensation reaction with the Si-OH groups on the surface of the sulfonated support. After the reaction, magnetic separation was performed under a magnetic field strength of 0.5T. The supernatant was quickly removed, and the separated solid was washed four times each with anhydrous ethanol and deionized water to remove physically adsorbed impurities. Finally, the washed solid was dried in a vacuum environment at 60℃ for 10h to obtain a pure solid with a specific surface area of ​​600m². 2 A sulfonic acid-carbon silicon composite solid acid catalyst with a loading of 2.0 mmol / g of sulfonic acid groups.

[0030] A highly efficient synthesis process for high-hydrogen-content silicone oil includes the following steps: Step S1: By mass, 95 parts of methylhydrocyclic compound and 20 parts of hexamethyldisiloxane are mixed in high-purity nitrogen with a water content of 8 ppm and an oxygen content of 3 ppm at 25°C and a stirring speed of 400 rpm for 20 min to form a raw material premix. The premix is ​​then filtered through a 0.20 μm polytetrafluoroethylene filter membrane to obtain a refined raw material liquid, which is stored in a pressurized raw material tank. Step S2: The sulfonic acid-silicon carbide composite solid acid catalyst is dispersed in a portion of the purified raw material liquid obtained in step S1 to form a stable suspension. The mass fraction of the solid acid catalyst in the stable suspension is 10%. The remaining purified raw material liquid and the stable suspension are pumped into the Y-type static mixing unit at the front end of a stainless steel microchannel reactor with an inner diameter of 1.0 mm, a channel length of 10 m, and an operating pressure of 0.5 MPa, respectively, synchronously and continuously, at a flow ratio of 20:1. The Reynolds number of the reaction liquid in the microchannel reactor is 400. In the microchannel reactor, the material undergoes ring-opening polymerization and equilibrium reaction at a temperature of 60 °C and a residence time of 20 min to obtain the crude product. Step S3: The crude product obtained in step S2 is subjected to magnetic separation to recover the sulfonic acid-carbon silicon composite solid acid catalyst at a magnetic field strength of 0.5T and a separation time of 3min. Then, it enters a low-temperature gradient de-oxidation system consisting of a three-stage series system with a temperature of 70℃ and an absolute pressure of 500Pa in the first stage distillation unit, a temperature of 85℃ and an absolute pressure of 350Pa in the second stage distillation unit, and a temperature of 100℃ and an absolute pressure of 150Pa in the third stage distillation unit. The three stage distillations are connected by insulated pipes. The crude product flows by gravity through the outlets of each stage by the internal pressure difference of the system. Each stage distillation unit is equipped with a scraper rotor with a rotation speed of 300 rpm. The outlet is connected to a cold trap with a temperature of -20℃ to remove unreacted monomers and oligomers, resulting in a high-hydrogen-content silicone oil product.

[0031] Comparative Example 1 The only difference from Example 1 is that in step S1, there are 70 parts of methylhydrocyclic cyclohexane and 3 parts of hexamethyldisiloxane.

[0032] Comparative Example 2 The only difference from Example 1 is that in step S1, there are 100 parts of methylhydrocyclic compound and 25 parts of hexamethyldisiloxane.

[0033] Comparative Example 3 The only difference from Example 1 is that in step S1, the mass percentage of tetramethyltetrahydrocyclotetrasiloxane in the methylhydrocyclone is 80%.

[0034] Comparative Example 4 The only difference from Example 1 is that in step S1, the mass percentage of tetramethyltetrahydrocyclotetrasiloxane in the methylhydrocyclone is 100%.

[0035] Comparative Example 5 The only difference from Example 1 is that in step S1, the polytetrafluoroethylene filter membrane filtration is omitted.

[0036] Comparative Example 6 The only difference from Example 1 is that a microchannel reactor is not used in step S2.

[0037] Comparative Example 7 The only difference from Example 1 is that in step S2, the mass fraction of the solid acid catalyst in the stable suspension is 20%.

[0038] Comparative Example 8 The only difference from Example 1 is that in step S2, an equal mass of conventional sulfonic acid cation exchange resin, such as Amberlyst-15, is used instead of the magnetic composite solid acid catalyst.

[0039] Comparative Example 9 The only difference from Example 1 is that in step S3, the three-stage gradient removal is cancelled and replaced with a single removal at 100°C and 100 Pa for 30 minutes.

[0040] Comparative Example 10 The only difference from Example 1 is that in step S3, the outlet of the low-temperature gradient de-cooling system is not connected to a cold trap.

[0041] Performance testing: Hydrogen content: The hydrogen content w0 was determined according to HG / T 4658-2014 "Determination of Active Hydrogen Content in Hydrogen-Containing Silicone Oil for Textile Dyeing and Finishing Auxiliaries". After storage at 80℃ for 30 days, w1 was measured again. The hydrogen content decay was calculated as: W δ =W0-W1.

[0042] Number average molecular weight, PDI: Refer to GB / T 21863-2008 "Gel permeation chromatography (GPC)". The sample solution passes through a chromatographic column filled with porous gel particles. Molecules of different sizes are separated due to their different permeation paths in the pores. Small molecules have a longer residence time, while large molecules elute first.

[0043] Platinum-cobalt color number: Refer to GB / T 3143-1982 "Determination of color of liquid chemical products (Hazen unit - platinum-cobalt color number)" and visually compare the sample with a series of standard color standard solutions with known platinum-cobalt color numbers under the same conditions to determine the color number that is closest to the sample color. The higher the color number, the deeper the color.

[0044] Catalyst recovery rate: The mass of the dried catalyst recovered by magnetic separation is compared with the mass of the catalyst initially added. Catalyst recovery rate (%) = (mass of the dried catalyst recovered / mass of the catalyst initially added) × 100%.

[0045] Table 1 Test Results of Examples and Comparative Examples

[0046] Examples 1-3 involve continuously feeding a suspension of refined methyl hydrogen cyclic compound and hexamethyldisiloxane raw material with a specially formulated sulfonate-carbon silicon composite solid acid catalyst into a microchannel reactor in a precise ratio. This allows for efficient and homogeneous ring-opening polymerization and equilibration reactions to be completed under mild conditions. Subsequently, the crude product undergoes rapid catalyst recovery via magnetic separation, followed by the gentle removal of low-boiling-point substances through a three-stage low-temperature gradient de-lowering system. Ultimately, high-quality hydrogen-containing silicone oil with precise hydrogen content, extremely narrow molecular weight distribution, light color, and excellent thermal stability is obtained, with a catalyst recovery rate exceeding 90%. This achieves efficient, green, and controllable continuous production from raw materials to finished products.

[0047] Comparative Example 1: Insufficient hexamethyldisiloxane resulted in the presence of numerous active chain ends, such as Si-H or Si-OH, leading to inter-chain crosslinking, forming a three-dimensional network structure, resulting in product failure, and the catalyst being encapsulated in a gel, making recovery difficult. Comparative Example 2: Chain growth was terminated by hexamethyldisiloxane in the initial stage of the reaction, preventing the formation of silicone oil with effective chain length. The product was a mixture of oligomers, losing its application value, and the hydrogen content was diluted by a large amount of inert hexamethyldisiloxane. Comparative Example 3: Octamethylcyclotetrasiloxane is an inert cyclic compound; the chain segments formed after ring opening do not contain active hydrogen, directly reducing the active hydrogen content of the product, which is a major performance defect. Comparative Example 4: The extremely high density of Si-H bonds easily undergoes intramolecular / intermolecular condensation and other side reactions under acid catalysis, resulting in a wide molecular weight distribution, the formation of chromophores, and continued reaction during storage. Comparative Example 5: The introduction of uncertain impurities, such as particulate impurities or metal ions, caused non-selective catalysis and localized hot spots, leading to uneven reaction, oxidative discoloration, and impurity abrasion of the catalyst surface, reducing recovery rate. Comparative Example 6: The batch reaction exhibits concentration and temperature gradients, with material residence times ranging from minutes to hours, resulting in an extremely wide molecular weight distribution and poor product uniformity. Comparative Example 7: An excessively rapid reaction may generate localized instantaneous exothermic reactions, triggering minor side reactions that lead to discoloration. Comparative Example 8: Although the catalytic performance may be similar, separation requires complex steps such as filtration, centrifugation, and washing, making continuous and automated production impossible and resulting in low industrial value. Comparative Example 9: At 100℃, some Si-H bonds undergo thermal decomposition or oxidation, leading to a decrease in hydrogen content and the formation of coloring substances. Comparative Example 10: Data is low, the process is not environmentally friendly, and the vacuum system is easily damaged.

[0048] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary; within the framework of this invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0049] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A highly efficient synthesis process for high-hydrogen-content silicone oil, characterized in that, Includes the following steps: Step S1: By weight, 80-95 parts of methylhydrocyclic compound and 5-20 parts of hexamethyldisiloxane are stirred and mixed under an inert atmosphere to form a raw material premix. The premix is ​​filtered through a 0.15-0.25μm polytetrafluoroethylene filter membrane to obtain a refined raw material liquid, which is stored in a pressurized raw material tank. Step S2: The sulfonic acid-silicon composite solid acid catalyst is dispersed in a portion of the refined raw material liquid obtained in step S1 to form a stable suspension. The mass fraction of the solid acid catalyst in the stable suspension is 5% to 15%. The remaining refined raw material liquid and the stable suspension are pumped into the Y-type static mixing unit at the front end of the microchannel reactor at a flow ratio of 10:1 to 30:1, respectively, synchronously and continuously. In the microchannel reactor, the material undergoes ring-opening polymerization and equilibrium reaction at a temperature of 40 to 70°C and a residence time of 10 to 30 minutes to obtain the crude product. Step S3: After recovering the sulfonic acid carbon silicon composite solid acid catalyst from the crude product obtained in step S2 by magnetic separation, unreacted monomers and oligomers are removed under an absolute pressure of 100~500Pa and a temperature range of 60~100℃ to obtain the high hydrogen content silicone oil product.

2. The efficient synthesis process of high-hydrogen-content silicone oil according to claim 1, characterized in that, In step S1, the methylhydrocyclotetrasiloxane is a mixture of octamethylcyclotetrasiloxane and tetramethyltetrahydrocyclotetrasiloxane, wherein the mass percentage of tetramethyltetrahydrocyclotetrasiloxane is 85% to 95%.

3. The efficient synthesis process of high-hydrogen-content silicone oil according to claim 1, characterized in that, In step S1, the inert atmosphere is high-purity nitrogen or argon, with a water content of less than 10 ppm and an oxygen content of less than 5 ppm; the stirring speed of the premixed reaction liquid is 300~600 rpm, and the time is 10~30 min.

4. The efficient synthesis process of high-hydrogen-content silicone oil according to claim 1, characterized in that, In step S2, the preparation method of the sulfonate-carbon-silicon composite solid acid catalyst includes the following steps: Step (1): Glucose, tetraethyl orthosilicate and hexadecyltrimethylammonium bromide are dissolved in an ethanol-water mixed solvent at a mass ratio of (10~20):1:(0.35~0.70). The mixture is stirred at 60~80℃ for 12~24h to carry out simultaneous hydrothermal carbonization and silica sol-gel process. The mixture is then transferred to a high-pressure reactor and hydrothermally reacted at 180~200℃ for 6~12h. After cooling, the mixture is centrifuged, washed and dried to obtain carbon / silica composite microsphere precursor. Step (2): The precursor obtained in step (1) is heated to 550~650℃ in an inert atmosphere and kept at the temperature for 4~6h to carbonize and remove hexadecyltrimethylammonium bromide to form a carbon / silica composite carrier. Step (3): The carrier obtained in step (2) is dispersed in a concentrated sulfuric acid dichloroethane solution with a concentration of 1.0~3.0 mol / L under nitrogen protection and mechanical stirring. The mixture is refluxed at 60~80℃ for 6~12h to carry out sulfonation. After the reaction, it is washed with deionized water until neutral and dried to obtain sulfonated carrier powder. Step (4): Disperse the sulfonated support powder obtained in step (3) in ethanol, add iron oxide nanoparticles, and after ultrasonic dispersion, stir at 60~80℃ for 2~4h. The amount of iron oxide nanoparticles added is 5%~15% of the total mass of the final catalyst. Finally, the solid acid catalyst is separated from the liquid phase by magnetic separation, and then washed and dried to obtain a pure sulfonated carbon silicon composite solid acid catalyst.

5. The efficient synthesis process of high-hydrogen-content silicone oil according to claim 1, characterized in that, In step S2, the specific surface area of ​​the sulfonate-carbon silicon composite solid acid catalyst is 500~800 m². 2 / g, with a sulfonic acid group loading of 1.5~2.5mmol / g.

6. The efficient synthesis process of high-hydrogen-content silicone oil according to claim 1, characterized in that, In step S2, the microchannel reactor is made of stainless steel, with an inner diameter of 0.5~2.0 mm, a channel length of 5~20 m, an operating pressure of 0.1~0.5 MPa, and a Reynolds number of 100~500 for the reaction liquid in the microchannel reactor.

7. The efficient synthesis process of high-hydrogen-content silicone oil according to claim 1, characterized in that, In step S3, the magnetic field strength used for magnetic separation is 0.3~0.8T, and the separation time is 2~5min.

8. The efficient synthesis process of high-hydrogen-content silicone oil according to claim 1, characterized in that, In step S3, the low-temperature gradient descaling system consists of three short-range molecular distillers connected in series. The first-stage system has a temperature of 60-70℃ and an absolute pressure of 400-500 Pa; the second-stage system has a temperature of 75-85℃ and an absolute pressure of 300-350 Pa; and the third-stage system has a temperature of 90-100℃ and an absolute pressure of 100-150 Pa. The first, second, and third-stage distillers are connected sequentially through insulated pipes. The crude product flows through each stage by gravity due to the internal pressure difference. Each stage distiller is equipped with a scraped film rotor with a rotation speed of 200-400 rpm.

9. The efficient synthesis process of high-hydrogen-content silicone oil according to claim 1, characterized in that, In step S3, the outlet of the low-temperature gradient de-cooling system is connected to a cold trap, and the temperature of the cold trap is -40~-20℃.

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