Process for producing electronic grade diethyl carbonate

Abstract

This invention relates to the field of fine chemical technology, specifically disclosing a production process for electronic-grade diethyl carbonate. The method includes the following steps: ethylene carbonate and anhydrous ethanol undergo a transesterification reaction in a microwave reactor catalyzed by a composite catalyst; the reaction solution is then subjected to phase separation treatment, followed by a continuous separation process coupling atmospheric and vacuum distillation to obtain an intermediate; further purification is achieved by molecular sieve adsorption to remove metal impurities and moisture, combined with precision filtration using a polytetrafluoroethylene membrane. The composite catalyst significantly improves the transesterification reaction efficiency and product selectivity. This process, through the synergistic effect of reaction process enhancement and multi-stage purification technology, achieves highly efficient removal of moisture, metal impurities, and nanoscale particles from the reaction system. The resulting electronic-grade diethyl carbonate meets the stringent requirements of high-end electronic chemicals such as lithium battery electrolytes, and possesses technical advantages such as short reaction cycle, thorough impurity removal, and high product purity.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, and more specifically, to a process for producing electronic-grade diethyl carbonate. Background Technology

[0002] Diethyl carbonate, as an important lipid compound, is a key component of high-end electronic chemicals such as lithium-ion battery electrolytes and semiconductor photoresists due to its excellent chemical stability and solubility. Electronic-grade diethyl carbonate requires extremely high purity, necessitating strict control of moisture, metal ions, and nanoscale particulate impurities. The core of its preparation technology lies in the efficient control of the transesterification reaction and the precise design of the purification process.

[0003] Currently, the industrial production of diethyl carbonate mainly employs the transesterification method, using ethylene carbonate or propylene carbonate and ethanol as raw materials, which are then reacted via transesterification under the action of a catalyst. However, these traditional processes have several drawbacks: on the one hand, the dimethyl carbonate produced in the reaction forms an azeotrope with methanol or ethanol, making it difficult to separate the product from the raw material, thus affecting the yield and purity of diethyl carbonate. On the other hand, traditional catalysts are usually homogeneous or solid catalysts, which suffer from problems such as difficult catalyst separation, low selectivity, and easy occurrence of side reactions, limiting the improvement of the target product yield and purity. Furthermore, the reaction conditions are relatively harsh, usually requiring high temperature and high pressure, resulting in high energy consumption and low production efficiency. Therefore, this invention provides a process method for producing electronic-grade diethyl carbonate to solve the above-mentioned technical problems. Summary of the Invention

[0004] The purpose of this invention is to provide a production process for electronic-grade diethyl carbonate. This process achieves efficient removal of moisture, metal impurities, and nano-sized particles from the reaction system through the synergistic effect of reaction process enhancement and multi-stage purification technology. The resulting electronic-grade diethyl carbonate meets the stringent requirements of high-end electronic chemicals such as lithium battery electrolytes. It has technical advantages such as short reaction cycle, thorough impurity removal, and high product purity.

[0005] A process for producing electronic-grade diethyl carbonate includes the following steps:

[0006] S1. Add ethylene carbonate and anhydrous ethanol to a microwave reactor, add a composite catalyst, purge the air with inert gas, turn on microwave heating, control the microwave heating conditions, reaction temperature and pressure, and stir the reaction to obtain a crude reaction solution containing diethyl carbonate, ethanol and ethylene glycol.

[0007] S2. Cool the crude reaction solution to 20-30℃, add sodium carbonate to separate the phases and separate the upper organic phase. Pump the organic phase into an atmospheric distillation column and a vacuum distillation column for continuous separation to obtain diethyl carbonate intermediate.

[0008] S3. The diethyl carbonate intermediate is subjected to adsorption treatment in a fixed-bed reactor filled with molecular sieves to remove moisture and metal impurities; then it is filtered through a polytetrafluoroethylene membrane to retain particles with a diameter >0.05-0.2μm to obtain electronic grade diethyl carbonate.

[0009] Preferably, step S1 comprises 10-15 parts by weight of ethylene carbonate, 8-12 parts by weight of anhydrous ethanol and 0.4-0.8 parts by weight of composite catalyst.

[0010] Preferably, in step S1, the microwave frequency is 2000-2500MHz, the power is 200-400W, the reaction temperature is 60-70℃, the pressure is 0.04-0.06MPa, and the stirring reaction time is 25-35min.

[0011] Preferably, in step S2, the production process of electronic-grade diethyl carbonate according to claim 1 is characterized in that the top temperature of the atmospheric distillation column in step S2 is 75-80℃, the bottom temperature is 115-125℃, the vacuum degree of the vacuum distillation column is -0.08 to -0.1MPa, the top temperature is 80-90℃, and the bottom temperature is 105-115℃.

[0012] Preferably, in step S3, the adsorption temperature is 45-55℃ and the flow rate is 0.3-0.7 BV / h.

[0013] Preferably, in step S3, the molecular sieve is composed of 3A and 13X type molecular sieves with a mass ratio of 1-3:1, and the filling height of the mixed molecular sieve is 4-6 times the bed diameter.

[0014] Preferably, the preparation step of the composite catalyst in step S1 is as follows:

[0015] A1. Hexagonal boron nitride was dispersed in N-methylpyrrolidone, sodium dodecylbenzenesulfonate was added, and the mixture was ultrasonically exfoliated for 3-5 hours. After centrifugation and drying, boron nitride nanosheets were obtained. The boron nitride nanosheets and alumina nanoparticles were dispersed in anhydrous ethanol, ultrasonically dispersed for 30-40 minutes, and then stirred and mixed at 70-80℃ for 2-4 hours. After centrifugation and drying, a composite carrier was obtained.

[0016] A2. The composite support is dispersed in toluene, 3-aminopropyltrimethoxysilane is added, and the reaction is carried out at 80-100℃ for 4-6 h under nitrogen protection. After washing and drying, an intermediate is obtained. The intermediate is dispersed in toluene, 3-glycidyl etheroxypropyltrimethoxysilane is added, and the reaction is carried out at 90-110℃ for 5-7 h under nitrogen protection. After washing and drying, the modified composite support is obtained.

[0017] A3. The modified composite support and 1-butyl-3-methylimidazolium hydroxyacetate were dispersed in deionized water, the pH was adjusted to 10-12, and the reaction was carried out at 50-70℃ for 6-8h. Then 1-propylsulfonyl-3-methylimidazolium hydrogen sulfate was added, and the reaction was continued at 60-80℃ for 7-9h. After washing and drying, the composite catalyst was obtained.

[0018] Preferably, step A1 comprises, by weight, 10-15 parts hexagonal boron nitride, 80-90 parts N-methylpyrrolidone, 1-3 parts sodium dodecylbenzenesulfonate; and 10-15 parts boron nitride nanosheets, 5-8 parts alumina nanoparticles, and 70-80 parts anhydrous ethanol.

[0019] Preferably, step A2 comprises, by weight, 10-15 parts of the composite carrier, 60-70 parts of toluene and 2-5 parts of 3-aminopropyltrimethoxysilane; and 10-15 parts of the intermediate, 60-70 parts of toluene and 3-6 parts of 3-glycidyl etheroxypropyltrimethoxysilane.

[0020] Preferably, step A3 comprises, by weight, 3-6 parts of modified composite carrier, 0.3-0.8 parts of 1-butyl-3-methylimidazolium hydroxyacetate, 30-40 parts of deionized water, and 0.5-1 parts of 1-propylsulfonyl-3-methylimidazolium hydrogen sulfate.

[0021] In summary, the present invention has the following beneficial effects:

[0022] 1. This invention constructs a highly active and selective composite catalyst system by bifunctionally modifying a boron nitride and alumina composite support. Based on the layered structure of boron nitride nanosheets and the mesoporous properties of alumina nanoparticles, the composite support provides abundant loading sites and mass transfer channels, significantly enhancing the dispersibility of the active components. Furthermore, through stepwise grafting modification with amino and epoxy silanes, a gradient functionalized surface is formed, enabling the directional anchoring of glycolic acid esters and sulfonic acid imidazole salts to form acid-base synergistic active centers. This allows for precise control of the proton transfer pathway in the transesterification reaction, suppressing the formation of byproducts. The non-thermal effect of the microwave field further enhances the adsorption-dissociation behavior of reactant molecules on the catalyst surface, overcoming the kinetic limitations of traditional heat conduction and achieving efficient conversion under mild conditions.

[0023] 2. This invention employs a multi-stage purification strategy combining molecular sieve adsorption and polytetrafluoroethylene (PTFE) membrane filtration, achieving deep removal of impurities through structural complementarity. The microporous characteristics of 3A molecular sieve preferentially adsorb moisture and small polar impurities, while 13X molecular sieve selectively captures metal ions through ion exchange. The hydrophobic surface properties and pore size distribution design of the PTFE membrane effectively intercept nanoscale particles and reduce the risk of membrane fouling. This purification system, through the synergistic effect of chemical adsorption by molecular sieves and physical retention by membranes, overcomes the limitations of single purification technologies in removing trace impurities, ensuring product purity reaches electronic-grade standards. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the experimental materials used, unless otherwise specified, were all purchased from conventional biochemical reagent stores. All quantitative experiments in the following examples were performed in triplicate, and the data are the average of the three replicates or the average ± standard deviation.

[0026] Hexagonal boron nitride, purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number S40088;

[0027] Type 3A molecular sieve, purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number S14149;

[0028] The 13X molecular sieve was purchased from Xi'an Qiyue Biotechnology Co., Ltd., brand name Qiyue Biotechnology.

[0029] Example 1

[0030] A process for producing electronic-grade diethyl carbonate includes the following steps:

[0031] S1. Add 10 parts of ethylene carbonate and 8 parts of anhydrous ethanol to a microwave reactor, add 0.4 parts of composite catalyst, purge the air with nitrogen, turn on microwave heating, control the microwave frequency to 2000MHz, the power to 200W, the reaction temperature to 60℃, the pressure to 0.04MPa, stir the reaction at 200r / min for 35min to obtain a crude reaction solution containing diethyl carbonate, ethanol and ethylene glycol.

[0032] S2. The crude reaction solution was cooled to 20°C, and sodium carbonate was added for phase separation. After standing for 30 minutes, the upper organic phase was separated. The organic phase was then pumped sequentially into an atmospheric distillation column and a vacuum distillation column for continuous separation. The atmospheric distillation column had a top temperature of 75°C and a bottom temperature of 115°C; the vacuum distillation column had a vacuum of -0.08 MPa, a top temperature of 80°C, and a bottom temperature of 105°C, ultimately yielding diethyl carbonate intermediate.

[0033] S3. The diethyl carbonate intermediate was passed through a fixed-bed reactor packed with molecular sieves. The molecular sieves consisted of 3A and 13X type molecular sieves in a 1:1 mass ratio, and the packing height of the mixed molecular sieves was four times the bed diameter. The adsorption temperature was 45℃, the flow rate was 0.3 BV / h, and after 2 hours of treatment, moisture and metal impurities were removed. Subsequently, the mixture was filtered through a polytetrafluoroethylene membrane to retain particles with a diameter >0.05 μm, yielding electronic-grade diethyl carbonate.

[0034] The preparation steps of the composite catalyst are as follows:

[0035] A1. 10 parts of hexagonal boron nitride were dispersed in 80 parts of N-methylpyrrolidone, and 1 part of sodium dodecylbenzenesulfonate was added. The mixture was ultrasonically exfoliated for 5 hours at a power of 200 W and a temperature of 25 °C. After centrifugation and drying, boron nitride nanosheets were obtained. 10 parts of boron nitride nanosheets and 5 parts of alumina nanoparticles were dispersed in 70 parts of anhydrous ethanol. The mixture was ultrasonically dispersed for 40 minutes at a power of 150 W and a temperature of 30 °C. Then, the mixture was stirred and blended at 70 °C for 4 hours at a stirring speed of 300 r / min. After centrifugation and drying, a composite carrier was obtained.

[0036] A2. Disperse 10 parts of the composite support in 60 parts of toluene, add 2 parts of 3-aminopropyltrimethoxysilane, react at 80℃ for 6 h under nitrogen protection, stirring at 200 r / min, wash and dry to obtain an intermediate; disperse 10 parts of the intermediate in 60 parts of toluene, add 3 parts of 3-glycidyl etheroxypropyltrimethoxysilane, react at 90℃ for 7 h under nitrogen protection, stirring at 200 r / min, wash and dry to obtain the modified composite support;

[0037] A3. Disperse 3 parts of the modified composite support and 0.3 parts of 1-butyl-3-methylimidazolium hydroxyacetate in 30 parts of deionized water, adjust the pH to 10, and react at 50℃ for 8 h with a stirring speed of 150 r / min; then add 0.5 parts of 1-propylsulfonyl-3-methylimidazolium hydrogen sulfate, and continue to react at 60℃ for 9 h with a stirring speed of 150 r / min. After washing and drying, the composite catalyst is obtained.

[0038] Example 2

[0039] A process for producing electronic-grade diethyl carbonate includes the following steps:

[0040] S1. Add 12 parts of ethylene carbonate and 10 parts of anhydrous ethanol to a microwave reactor, add 0.5 parts of composite catalyst, purge the air with nitrogen, turn on microwave heating, control the microwave frequency to 2250MHz, the power to 300W, the reaction temperature to 65℃, the pressure to 0.05MPa, stir the reaction at 250r / min for 30min to obtain a crude reaction solution containing diethyl carbonate, ethanol and ethylene glycol.

[0041] S2. The crude reaction solution was cooled to 25°C, and sodium carbonate was added for phase separation. After standing for 25 minutes, the upper organic phase was separated. The organic phase was then pumped sequentially into an atmospheric distillation column and a vacuum distillation column for continuous separation. The atmospheric distillation column had a top temperature of 78°C and a bottom temperature of 120°C; the vacuum distillation column had a vacuum of -0.09 MPa, a top temperature of 85°C, and a bottom temperature of 110°C, ultimately yielding diethyl carbonate intermediate.

[0042] S3. The diethyl carbonate intermediate was passed through a fixed-bed reactor packed with molecular sieves. The molecular sieves consisted of 3A and 13X type molecular sieves in a mass ratio of 2:1, and the packing height of the mixed molecular sieves was 5 times the bed diameter. The adsorption temperature was 50℃, the flow rate was 0.5 BV / h, and the treatment time was 1.5h to remove moisture and metal impurities. Subsequently, it was filtered through a polytetrafluoroethylene membrane to retain particles with a diameter >0.1μm, thus obtaining electronic-grade diethyl carbonate.

[0043] The preparation steps of the composite catalyst are as follows:

[0044] A1. 12 parts of hexagonal boron nitride were dispersed in 85 parts of N-methylpyrrolidone, and 2 parts of sodium dodecylbenzenesulfonate were added. The mixture was ultrasonically exfoliated for 4 hours at an ultrasonic power of 250 W and an ultrasonic temperature of 30 °C. After centrifugation and drying, boron nitride nanosheets were obtained. 12 parts of boron nitride nanosheets and 6 parts of alumina nanoparticles were dispersed in 75 parts of anhydrous ethanol. The mixture was ultrasonically dispersed for 35 minutes at an ultrasonic power of 200 W and a temperature of 35 °C. Then, the mixture was stirred and blended at 75 °C for 3 hours at a stirring speed of 350 r / min. After centrifugation and drying, a composite carrier was obtained.

[0045] A2. 12 parts of the composite support were dispersed in 65 parts of toluene, and 3 parts of 3-aminopropyltrimethoxysilane were added. The mixture was reacted at 90°C for 5 hours under nitrogen protection with a stirring speed of 220 r / min. After washing and drying, the intermediate was obtained. 12 parts of the intermediate were dispersed in 65 parts of toluene, and 4 parts of 3-glycidyl etheroxypropyltrimethoxysilane were added. The mixture was reacted at 100°C for 6 hours under nitrogen protection with a stirring speed of 220 r / min. After washing and drying, the modified composite support was obtained.

[0046] A3. Four parts of the modified composite support and 0.5 parts of 1-butyl-3-methylimidazolium hydroxyacetate were dispersed in 35 parts of deionized water, the pH was adjusted to 11, and the reaction was carried out at 60℃ for 7 h with a stirring speed of 160 r / min. Then, 0.7 parts of 1-propylsulfonyl-3-methylimidazolium hydrogen sulfate were added, and the reaction was continued at 70℃ for 8 h with a stirring speed of 160 r / min. After washing and drying, the composite catalyst was obtained.

[0047] Example 3

[0048] A process for producing electronic-grade diethyl carbonate includes the following steps:

[0049] S1. Add 15 parts of ethylene carbonate and 12 parts of anhydrous ethanol to a microwave reactor, add 0.8 parts of composite catalyst, purge the air with nitrogen, turn on microwave heating, control the microwave frequency to 2500MHz, power to 400W, reaction temperature to 70℃, pressure to 0.06MPa, stir the reaction at 300r / min for 25min to obtain a crude reaction solution containing diethyl carbonate, ethanol and ethylene glycol.

[0050] S2. The crude reaction solution was cooled to 30°C, and sodium carbonate was added for phase separation. After standing for 20 minutes, the upper organic phase was separated and continuously pumped into an atmospheric distillation column and a vacuum distillation column for further separation. The atmospheric distillation column had a top temperature of 80°C and a bottom temperature of 125°C; the vacuum distillation column had a vacuum of -0.1 MPa, a top temperature of 90°C, and a bottom temperature of 115°C, ultimately yielding diethyl carbonate intermediate.

[0051] S3. The diethyl carbonate intermediate was passed through a fixed-bed reactor packed with molecular sieves. The molecular sieves consisted of 3A and 13X type molecular sieves in a mass ratio of 3:1, and the packing height of the mixed molecular sieves was 6 times the bed diameter. The adsorption temperature was 55℃, the flow rate was 0.7 BV / h, and after 1 hour of treatment, moisture and metal impurities were removed. Subsequently, the mixture was filtered through a polytetrafluoroethylene membrane to retain particles with a diameter >0.2 μm, yielding electronic-grade diethyl carbonate.

[0052] The preparation steps of the composite catalyst are as follows:

[0053] A1. 15 parts of hexagonal boron nitride were dispersed in 90 parts of N-methylpyrrolidone, and 3 parts of sodium dodecylbenzenesulfonate were added. The mixture was ultrasonically exfoliated for 3 hours at a power of 300 W and a temperature of 35 °C. After centrifugation and drying, boron nitride nanosheets were obtained. 15 parts of boron nitride nanosheets and 8 parts of alumina nanoparticles were dispersed in 80 parts of anhydrous ethanol. The mixture was ultrasonically dispersed for 30 minutes at a power of 250 W and a temperature of 40 °C. Then, the mixture was stirred and blended at 80 °C for 2 hours at a stirring speed of 400 r / min. After centrifugation and drying, a composite carrier was obtained.

[0054] A2. 15 parts of the composite support were dispersed in 70 parts of toluene, and 5 parts of 3-aminopropyltrimethoxysilane were added. The mixture was reacted at 100℃ for 4 hours under nitrogen protection with a stirring speed of 250 r / min. After washing and drying, the intermediate was obtained. 15 parts of the intermediate were dispersed in 70 parts of toluene, and 6 parts of 3-glycidyl etheroxypropyltrimethoxysilane were added. The mixture was reacted at 110℃ for 5 hours under nitrogen protection with a stirring speed of 250 r / min. After washing and drying, the modified composite support was obtained.

[0055] A3. Disperse 6 parts of the modified composite support and 0.8 parts of 1-butyl-3-methylimidazolium hydroxyacetate in 40 parts of deionized water, adjust the pH to 12, and react at 70℃ for 6 h with a stirring speed of 180 r / min; then add 1 part of 1-propylsulfonyl-3-methylimidazolium hydrogen sulfate, and continue to react at 80℃ for 7 h with a stirring speed of 180 r / min. After washing and drying, the composite catalyst is obtained.

[0056] Example 4

[0057] A process for producing electronic-grade diethyl carbonate includes the following steps:

[0058] S1. Add 13 parts of ethylene carbonate and 11 parts of anhydrous ethanol to a microwave reactor, add 0.6 parts of composite catalyst, purge the air with nitrogen, turn on microwave heating, control the microwave frequency to 2350MHz, power to 350W, reaction temperature to 68℃, pressure to 0.055MPa, stir the reaction at 280r / min for 28min to obtain a crude reaction solution containing diethyl carbonate, ethanol and ethylene glycol.

[0059] S2. The crude reaction solution was cooled to 23°C, and sodium carbonate was added for phase separation. After standing for 22 minutes, the upper organic phase was separated and continuously pumped into an atmospheric distillation column and a vacuum distillation column for further separation. The atmospheric distillation column had a top temperature of 77°C and a bottom temperature of 122°C; the vacuum distillation column had a vacuum of -0.085 MPa, a top temperature of 85°C, and a bottom temperature of 110°C, ultimately yielding diethyl carbonate intermediate.

[0060] S3. The diethyl carbonate intermediate was passed through a fixed-bed reactor packed with molecular sieves. The molecular sieves consisted of 3A and 13X type molecular sieves in a mass ratio of 2.5:1, and the packing height of the mixed molecular sieves was 5.5 times the bed diameter. The adsorption temperature was 52℃, the flow rate was 0.6 BV / h, and the treatment time was 1.2h to remove moisture and metal impurities. Subsequently, it was filtered through a polytetrafluoroethylene membrane to retain particles with a diameter >0.15μm, thus obtaining electronic-grade diethyl carbonate.

[0061] The preparation steps of the composite catalyst are as follows:

[0062] A1. 13 parts of hexagonal boron nitride were dispersed in 88 parts of N-methylpyrrolidone, and 2.5 parts of sodium dodecylbenzenesulfonate were added. The mixture was ultrasonically exfoliated for 4.5 h at an ultrasonic power of 280 W and a temperature of 32 °C. After centrifugation and drying, boron nitride nanosheets were obtained. 13 parts of boron nitride nanosheets and 7 parts of alumina nanoparticles were dispersed in 78 parts of anhydrous ethanol. The mixture was ultrasonically dispersed for 38 min at an ultrasonic power of 230 W and a temperature of 38 °C. Then, the mixture was stirred and blended at 78 °C for 3.5 h at a stirring speed of 380 r / min. After centrifugation and drying, a composite carrier was obtained.

[0063] A2. 13 parts of the composite support were dispersed in 68 parts of toluene, and 4 parts of 3-aminopropyltrimethoxysilane were added. The mixture was reacted at 95°C for 5.5 h under nitrogen protection with a stirring speed of 230 r / min. After washing and drying, an intermediate was obtained. 13 parts of the intermediate were dispersed in 68 parts of toluene, and 5 parts of 3-glycidyl etheroxypropyltrimethoxysilane were added. The mixture was reacted at 105°C for 6.5 h under nitrogen protection with a stirring speed of 230 r / min. After washing and drying, a modified composite support was obtained.

[0064] A3. Disperse 5 parts of the modified composite support and 0.6 parts of 1-butyl-3-methylimidazolium hydroxyacetate in 38 parts of deionized water, adjust the pH to 11.5, and react at 65℃ for 7.5 h with a stirring speed of 170 r / min; then add 0.8 parts of 1-propylsulfonyl-3-methylimidazolium hydrogen sulfate, and continue to react at 75℃ for 8.5 h with a stirring speed of 170 r / min. After washing and drying, the composite catalyst is obtained.

[0065] Comparative Example 1

[0066] A process for producing electronic-grade diethyl carbonate differs from Example 4 in that the composite catalyst described in this invention is not used in step S1, but instead a traditional homogeneous catalyst, triethylamine. The remaining reaction conditions, namely microwave frequency, power, temperature, and pressure, are the same as in Example 4.

[0067] Comparative Example 2

[0068] A production process for electronic-grade diethyl carbonate differs from Example 4 in that the aminosilane grafting modification in step A2 is omitted in the composite catalyst preparation step. That is, the composite support obtained in step A1 is directly used for loading the ionic liquid in step A3, and the surface functionalization treatment of 3-aminopropyltrimethoxysilane and 3-glycidyl etheroxypropyltrimethoxysilane is not performed. The rest of the catalyst preparation and reaction conditions, such as microwave frequency, power, temperature, and pressure, are the same as in Example 4.

[0069] Comparative Example 3

[0070] A production process for electronic-grade diethyl carbonate differs from Example 4 in that the surface modification steps A2 and A3 are omitted in the composite catalyst preparation step. That is, the boron nitride and alumina composite support obtained in step A1 is directly used as the catalyst. The remaining catalyst preparation and reaction conditions, such as microwave frequency, power, temperature, and pressure, are the same as in Example 4.

[0071] Comparative Example 4

[0072] A process for producing electronic-grade diethyl carbonate differs from Example 4 in that 1-propylsulfonyl-3-methylimidazolium hydrogen sulfate is not introduced in step A3 of the composite catalyst preparation step; only 1-butyl-3-methylimidazolium hydroxyacetate is retained. The remaining catalyst preparation and reaction conditions, such as microwave frequency, power, temperature, and pressure, are the same as in Example 4.

[0073] Comparative Example 5

[0074] A process for producing electronic-grade diethyl carbonate differs from Example 4 in that step S3 does not use a combination system of 3A and 13X molecular sieves, but instead uses 3A molecular sieve alone, with a packing height of 5 times the bed diameter. The remaining purification conditions, such as adsorption temperature, flow rate, and membrane filtration parameters, are the same as in Example 4.

[0075] Comparative Example 6

[0076] A production process for electronic-grade diethyl carbonate differs from Example 4 in that step S1 does not use microwave heating, but instead uses traditional oil bath heating. At the same time, the heating power is equivalently matched to maintain the reaction temperature at 68°C. The stirring speed and reaction time are the same as in Example 4, and the remaining reaction conditions remain unchanged.

[0077] Performance testing

[0078] The production processes of electronic-grade diethyl carbonate in Examples 1-4 and Comparative Examples 1-6 were tested for performance, and the test results are shown in Table 1 below.

[0079] Table 1

[0080] Test Project Yield / % Selectivity / % Moisture / ppm Catalyst cycle number Example 1 92.3 98.3 4.2 8 Example 2 93.8 98.5 3.5 9 Example 3 92.0 98.4 4.0 8 Example 4 94.2 98.9 2.8 10 Comparative Example 1 78.6 92.0 18.5 / Comparative Example 2 85.1 92.5 10.2 5 Comparative Example 3 81.5 93.2 15.3 4 Comparative Example 4 88.2 96.0 8.7 6 Comparative Example 5 89.4 98.0 5.5 7 Comparative Example 6 87.1 97.2 4.8 6

[0081] 1. Examples 1-4 of this invention, through microwave-enhanced transesterification and the synergistic effect of composite catalysts, achieved yields ≥92.3%, significantly higher than Comparative Examples 1-6. Example 4, relying on a gradient functionalized modified support—specifically, the stepwise grafting of 3-aminopropyltrimethoxysilane and 3-glycidyl etheroxypropyltrimethoxysilane to construct an acid-base synergistic active center—achieved a high yield of 94.2% and a high selectivity of 98.9%, effectively suppressing the formation of byproducts such as ethylene glycol. In Comparative Example 1, the traditional homogeneous catalyst, due to poor dispersion of active centers, had a yield of only 78.6%, verifying the necessity of composite catalyst design.

[0082] 2. The example uses a combination of 3A and 13X molecular sieves for adsorption, combined with precision filtration via a polytetrafluoroethylene membrane. The moisture content is ≤4.2ppm, significantly lower than that of comparative examples 1-6. The microporous structure of the 3A molecular sieve preferentially adsorbs small water molecules, while the 13X molecular sieve captures polar metal ions through ion exchange. The two work synergistically to achieve deep dehydration and removal of metal impurities, meeting the stringent requirements of electronic-grade diethyl carbonate for trace moisture.

[0083] 3. The composite catalyst in Example 4 achieved a cycle count of 10 times, significantly higher than Comparative Examples 1-6. This is attributed to the high mechanical strength of the boron nitride nanosheet and alumina nanoparticle composite support and the directional loading of 1-butyl-3-methylimidazolium glycolate and 1-propylsulfonyl-3-methylimidazolium hydrogen sulfate, which reduced the loss of active components. Comparative Example 2, which omitted support surface modification, only achieved 5 cycles, demonstrating the crucial role of gradient functionalization modification in catalyst structural stability.

[0084] In summary, this invention, through microwave field coupling of composite catalysts and multi-stage purification technology, significantly outperforms single-variable comparative examples in four core indicators: yield, selectivity, moisture control, and catalyst cycle stability. Among these, Example 4 exhibits the best overall performance, validating the synergistic advantages of dual-functional modification of the composite support, microwave non-thermal mass transfer enhancement, and molecular sieve-membrane filtration gradient purification. This provides an industrially feasible solution for the green and efficient production of electronic-grade diethyl carbonate.

[0085] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A process for producing electronic-grade diethyl carbonate, characterized in that, Includes the following steps: S1. Add ethylene carbonate and anhydrous ethanol to a microwave reactor, add a composite catalyst, purge the air with inert gas, turn on microwave heating, control the microwave frequency to 2000-2500MHz, the power to 200-400W, the reaction temperature to 60-70℃, the pressure to 0.04-0.06MPa, stir the reaction for 25-35min to obtain a crude reaction solution containing diethyl carbonate, ethanol and ethylene glycol. S2. Cool the crude reaction solution, add sodium carbonate to separate the phases and separate the upper organic phase. Pump the organic phase into an atmospheric distillation column and a vacuum distillation column for continuous separation to obtain diethyl carbonate intermediate. S3. The diethyl carbonate intermediate is subjected to adsorption treatment in a fixed-bed reactor packed with molecular sieves to remove moisture and metal impurities; then it is filtered through a polytetrafluoroethylene membrane to retain particles with a diameter of 0.05-0.2μm to obtain electronic grade diethyl carbonate. The preparation step of the composite catalyst in step S1 is as follows: A1. Hexagonal boron nitride was dispersed in N-methylpyrrolidone, sodium dodecylbenzenesulfonate was added, and the mixture was ultrasonically exfoliated for 3-5 hours. After centrifugation and drying, boron nitride nanosheets were obtained. The boron nitride nanosheets and alumina nanoparticles were dispersed in anhydrous ethanol, ultrasonically dispersed for 30-40 minutes, and then stirred and mixed at 70-80℃ for 2-4 hours. After centrifugation and drying, a composite carrier was obtained. A2. The composite support is dispersed in toluene, 3-aminopropyltrimethoxysilane is added, and the reaction is carried out at 80-100℃ for 4-6 h under nitrogen protection. After washing and drying, an intermediate is obtained. The intermediate is dispersed in toluene, 3-glycidyl etheroxypropyltrimethoxysilane is added, and the reaction is carried out at 90-110℃ for 5-7 h under nitrogen protection. After washing and drying, the modified composite support is obtained. A3. The modified composite support and 1-butyl-3-methylimidazolium hydroxyacetate were dispersed in deionized water, the pH was adjusted to 10-12, and the reaction was carried out at 50-70℃ for 6-8h. Then 1-propylsulfonyl-3-methylimidazolium hydrogen sulfate was added, and the reaction was continued at 60-80℃ for 7-9h. After washing and drying, the composite catalyst was obtained.

2. The production process of electronic-grade diethyl carbonate according to claim 1, characterized in that, In step S1, the components are 10-15 parts by weight of ethylene carbonate, 8-12 parts by weight of anhydrous ethanol and 0.4-0.8 parts by weight of composite catalyst.

3. The production process of electronic-grade diethyl carbonate according to claim 1, characterized in that, In step S2, the top temperature of the atmospheric distillation column is 75-80℃ and the bottom temperature is 115-125℃. The vacuum degree of the vacuum distillation column is -0.08 to -0.1MPa, the top temperature is 80-90℃, and the bottom temperature is 105-115℃.

4. The production process of electronic-grade diethyl carbonate according to claim 1, characterized in that, In step S3, the adsorption temperature is 45-55℃ and the flow rate is 0.3-0.7 BV / h.

5. The production process of electronic-grade diethyl carbonate according to claim 1, characterized in that, In step S3, the molecular sieve is composed of 3A and 13X type molecular sieves with a mass ratio of 1-3:1, and the filling height of the mixed molecular sieve is 4-6 times the bed diameter.

6. The production process of electronic-grade diethyl carbonate according to claim 1, characterized in that, Step A1 comprises, by weight, 10-15 parts hexagonal boron nitride, 80-90 parts N-methylpyrrolidone, 1-3 parts sodium dodecylbenzenesulfonate; and 10-15 parts boron nitride nanosheets, 5-8 parts alumina nanoparticles, and 70-80 parts anhydrous ethanol.

7. The production process of electronic-grade diethyl carbonate according to claim 1, characterized in that, Step A2 comprises, by weight, 10-15 parts of the composite carrier, 60-70 parts of toluene and 2-5 parts of 3-aminopropyltrimethoxysilane; and 10-15 parts of the intermediate, 60-70 parts of toluene and 3-6 parts of 3-glycidyl etheroxypropyltrimethoxysilane.

8. The production process of electronic-grade diethyl carbonate according to claim 1, characterized in that, In step A3, by weight, there are 3-6 parts of modified composite carrier, 0.3-0.8 parts of 1-butyl-3-methylimidazolium hydroxyacetate, 30-40 parts of deionized water, and 0.5-1 parts of 1-propylsulfonyl-3-methylimidazolium hydrogen sulfate.