Method for synthesizing diethyl adipate through dynamic covalent chemical regulation

Abstract

The invention provides a method for synthesizing diethyl adipate through dynamic covalent chemical regulation. Comprising the following steps: S1, sequentially adding 80-120g of adipic acid, 160-240mL of absolute ethyl alcohol, 5-8g of a difunctional dynamic regulation and control carrier, 2-4g of a ternary composite catalyst, 1-2g of a synergistic additive and 100-150mL of a mixed solvent consisting of cyclohexane and methylbenzene into a 500mL four-neck flask provided with a thermometer, a water segregator and a pH sensor, and adjusting the initial pH value to 8.0-8.5; stirring and reacting for 6 to 8 hours at the rotating speed of 450 to 500r / min under the condition of 70 to 75 DEG C; and S2, after the reaction is finished, cooling to 25 DEG C, separating and recovering the bifunctional dynamic regulation and control carrier and the ternary composite catalyst, introducing CO2 into the filtrate to regulate the pH value to 5.0-5.5, releasing the captured moisture, and carrying out reduced pressure distillation under the conditions of 80-90 DEG C and-0.08 MPa to obtain diethyl adipate. By means of the rare earth ion-carbon quantum dot-ionic liquid ternary composite catalyst, efficient catalysis under the strong acid-free condition is achieved, and the catalyst recovery rate and the product purity are greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical synthesis, in particular to a method for synthesizing diethyl adipate by dynamic covalent chemistry regulation. BACKGROUND

[0002] Diethyl adipate is an important organic solvent and plasticizer, widely used in the fields of coatings, perfumes and pharmaceutical intermediates. Currently, the esterification reaction of adipic acid and ethanol is mainly catalyzed by concentrated sulfuric acid in industry. However, this method has the following defects: 1. Strong corrosion: concentrated sulfuric acid causes serious corrosion of equipment, increasing the cost of equipment maintenance and safety risk; 2. Many side reactions: high temperature (120-150℃) easily leads to side reactions such as carbonization and polymerization of raw materials, resulting in low product purity (usually less than 95%) and a large amount of waste acid pollution; 3. Low catalytic efficiency: the traditional method requires high temperature and long reaction time (10-15h), high energy consumption and difficult recovery of catalyst; 4. Water inhibition: the water generated in the esterification reaction reduces the equilibrium conversion rate.

[0003] In the prior art, solid acid, ionic liquid and other alternatives to concentrated sulfuric acid are gradually tried, but there are still problems such as low catalyst activity and insufficient water management. Therefore, developing a green, efficient and water-regulated esterification synthesis technology is an urgent problem to be solved in the industry. SUMMARY

[0004] In view of the problems in the prior art, the present application provides a method for synthesizing diethyl adipate by dynamic covalent chemistry regulation.

[0005] To achieve the above purpose, the present application realizes the following technical solutions: The present application discloses a method for synthesizing diethyl adipate by dynamic covalent chemistry regulation, which comprises the following steps: S1, in a 500mL four-necked flask equipped with a thermometer, a water separator and a pH sensor, 80-120g of adipic acid, 160-240mL of anhydrous ethanol, 5-8g of a bifunctional dynamic regulation carrier, 2-4g of a ternary composite catalyst, 1-2g of a synergistic additive and 100-150mL of a mixed solvent composed of cyclohexane and toluene are sequentially added, the initial pH is adjusted to 8.0-8.5, and the reaction is stirred at a speed of 450-500r / min at 70-75℃ for 6-8h, and the real-time monitoring of Eu 3+ in the ternary composite catalyst is carried out by fluorescence spectrum during the reaction process; S2, after the reaction, the temperature is lowered to 25 DEG C, the bifunctional dynamic regulation carrier and the ternary composite catalyst are separated and recovered, the filtrate is introduced into CO2 to adjust the pH to 5.0-5.5, the captured water is released, and diethyl adipate is obtained by distillation under reduced pressure at 80-90 DEG C and -0.08 MPa.

[0006] Preferably, the fluorescence spectrum of Eu 3+ During real-time monitoring, samples are taken every 30 minutes for analysis.

[0007] Preferably, the bifunctional dynamic regulation carrier is prepared by the following method: a1, 15-20 g of ZrCl4 and 10-15 g of 2-amino terephthalic acid are dissolved in 200-250 mL of N,N-dimethylformamide, pre-dissolved at low temperature, then stirred at 350-400 r / min for 24-30 h at 120-140 DEG C to prepare an amino-functionalized MOF; a2, after the product obtained in a1 is cooled to 60 DEG C, 8-12 g of 4-boronic acid benzaldehyde is added, and the stirring is continued at 350-400 r / min for 8-10 h to form an imine bond connected MOF-COF composite material; a3, the product obtained in a2 is washed with N,N-dimethylformamide three times, each time with 50 mL, and finally dried under vacuum at 100-120 DEG C for 12 h to obtain a white powder of the bifunctional dynamic regulation carrier.

[0008] By setting the above technical solution, the bifunctional dynamic regulation carrier is a composite material formed by connecting the MOF skeleton and the COF structure through the imine bond, and the borate ester bond on the surface can preferentially capture the water generated in the reaction through a reversible reaction; the imine bond remains stable under the reaction conditions of pH 8.0-8.5, and can fix the ternary composite catalyst on the surface of the carrier to form a catalytic region, and when the pH is adjusted to 5.0-5.5 at the end of the reaction, the imine bond breaks, allowing the catalyst to be separated from the carrier for recovery.

[0009] Preferably, each gram of the bifunctional dynamic regulation carrier can adsorb 1.8-2.0 grams of water.

[0010] By setting the above technical solution, the reaction system can effectively capture the water generated in the reaction, avoiding the interference of water on the esterification reaction.

[0011] Preferably, the specific steps of low-temperature pre-dissolution are as follows: stirring at 200-250 r / min for 1-2 h at 60-70 DEG C.

[0012] By setting the above technical scheme, pre-dissolving at a lower temperature can avoid the problem of local high concentration and uneven reaction caused by high-temperature reaction of raw materials without sufficient dispersion, and is conducive to forming a MOF framework with uniform structure.

[0013] Preferably, in step a3, the material obtained in a2 is centrifuged at a speed of 4000-5000 r / min for 10-15 min before being washed with N,N-dimethylformamide.

[0014] By setting the above technical scheme, centrifugal separation can effectively remove unreacted small molecules, impurities and agglomerated particles, improve the purity and dispersibility of the product, and ensure the quality of the carrier.

[0015] Preferably, the preparation method of the ternary composite catalyst is as follows: b1, 20-25 g of citric acid and 10-15 g of urea are dissolved in 200-250 mL of water, and microwave reaction is carried out at a power of 500-700 W for 10-15 min, then dialysis is carried out with a dialysis bag with a molecular weight cut-off of 1000 for 48 h, to obtain a carbon quantum dot solution; b2, 100 mL of the carbon quantum dot solution is mixed with 1.0-1.5 g of europium nitrate, stirred at a speed of 300-350 r / min at 60℃ for 1.5-2 h, then 5-8 g of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate is added, ultrasonic treatment is carried out at a power of 300-400 W for 1-1.2 h, and freeze-drying is carried out to obtain a ternary composite catalyst powder.

[0016] By setting the above technical scheme, in the ternary composite catalyst, Eu 3+ The rare earth ions of Eu + The hydroxyl groups on the surface of the carbon quantum dots adsorb adipic acid and ethanol through hydrogen bonds, increasing the concentration of the two reactants near the catalyst; the ionic liquid (1-ethyl-3-methylimidazolium trifluoromethanesulfonate) provides protons (H + ), accelerates the condensation reaction of the carboxyl group and the hydroxyl group, and its ionic liquid property can dissolve the reaction intermediates to avoid the generation of by-products.

[0017] Preferably, each gram of the ternary composite catalyst contains 0.8-1.0 mmol of acidic active sites.

[0018] Preferably, the preparation method of the synergistic additive is as follows: 12-15 g of citric acid and 8-10 g of 3-aminopropyltriethoxysilane are mixed and stirred at a speed of 250-300 r / min at 50-60℃ for 4-6 h, then the solvent is removed by rotary evaporation at 60-70℃ and -0.09 MPa to obtain the synergistic additive.

[0019] By setting the above technical scheme, the citric acid group forms a three-dimensional hydrogen bond network with water, assisting the dual-functional dynamic regulation carrier to capture water, so that the water removal rate is improved; the amino group (-NH2) of 3-aminopropyl triethoxysilane forms a coordination bond with Eu 3+ of the ternary composite catalyst, enhances the stability of the catalyst. The synergistic additive and the dual-functional dynamic regulation carrier form a "gradient dehydration" system, and at the same time, the synergistic additive protects the active center of the catalyst, and prolongs the service life of the catalyst.

[0020] Preferably, in the mixed solvent composed of cyclohexane and toluene, the volume ratio of cyclohexane to toluene is 3:1.

[0021] The beneficial effects of the present application are: The present application combines mesoporous metal organic framework (MOF) with temperature-sensitive covalent organic framework (COF) to construct a borate-imine dual-functional dynamic regulation carrier with water capture and intelligent release functions. Through the pH / temperature dual-response regulation mechanism, the synergistic effect of the imine bond (pH response) and the borate bond (temperature response) greatly improves the esterification reaction equilibrium constant.

[0022] The dual-functional dynamic regulation carrier is a composite material formed by connecting the MOF skeleton and the COF structure through an imine bond. The borate bond on the surface of the dual-functional dynamic regulation carrier can preferentially capture the water generated by the reaction through a reversible reaction. The imine bond remains stable under the reaction conditions of pH 8.0-8.5, and can fix the ternary composite catalyst on the surface of the carrier to form a catalytic region. When the pH is adjusted to 5.0-5.5 at the end of the reaction, the imine bond breaks, allowing the catalyst to be separated from the carrier for recycling. In the ternary composite catalyst, Eu 3+的 The rare earth ions are coordinated with the carboxyl oxygen of adipic acid, enhancing the reactivity of the carboxyl group. The hydroxyl groups on the surface of the carbon quantum dots simultaneously adsorb adipic acid and ethanol through hydrogen bonds, increasing the concentration of the two reactants near the catalyst. The ionic liquid (1-ethyl-3-methyl imidazole trifluoromethanesulfonate) provides protons (H + ) to accelerate the condensation reaction of the carboxyl group and the hydroxyl group.

[0023] The present application realizes efficient catalysis under strong acid-free conditions through the "rare earth ion-carbon quantum dot-ionic liquid" ternary composite catalyst. The catalyst recovery rate exceeds 98%, and the product purity reaches 99.8%. The MOF skeleton provides an ultra-high specific surface area (more than 1200 m² / g), and the borate groups on the surface of the MOF skeleton can reversibly capture water (R-B(OR')2+H2O The water generated in the reaction is preferentially captured by R-B(OH)2+R'OH, so that the water content in the reaction system is reduced by more than 60%, and the esterification equilibrium is pushed to move in the positive direction. The imine bond (-C=N-) contained in the COF structure is stable under the condition that the pH is 8.0-8.5, the catalyst components are fixed on the surface of the carrier to form a "catalytic micro zone"; when the pH is adjusted to 5.0-5.5 at the end of the reaction, the imine bond is broken to release the catalyst, and high-efficiency recovery is realized. The water capture capacity of the MOF and the pH responsiveness of the COF form a "dehydration-catalysis-recovery" closed loop, so that the reaction efficiency is greatly improved. DETAILED DESCRIPTION

[0024] To make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0025] Embodiment 1 The embodiment discloses a method for dynamically covalently chemically regulating synthesis of diethyl adipate, comprising the following steps: S1, 80 g of adipic acid, 160 mL of anhydrous ethanol, 5 g of a bifunctional dynamic regulation carrier, 2 g of a ternary composite catalyst, 1 g of a synergistic additive and 100 mL of a mixed solvent composed of cyclohexane and toluene in a volume ratio of 3:1 are sequentially added into a 500 mL four-necked flask equipped with a thermometer, a water separator and a pH sensor, the initial pH is adjusted to 8.0, the reaction is stirred at 70 DEG C at a rotating speed of 450 r / min for 8 h, and the real-time monitoring of Eu 3+ in the ternary composite catalyst is performed by fluorescence spectroscopy during the reaction, and the sample is taken every 30 min for analysis; S2, after the reaction is completed, the temperature is lowered to 25 DEG C, the bifunctional dynamic regulation carrier and the ternary composite catalyst are separated and recovered, the filtrate is introduced into CO2 to adjust the pH to 5.0, the captured water is released, and diethyl adipate is obtained by distillation under reduced pressure at 80 DEG C and-0.08 MPa.

[0026] The preparation method of the bifunctional dynamic regulation carrier is as follows: a1, 15 g of ZrCl4 and 10 g of 2-amino terephthalic acid are dissolved in 200 mL of N,N-dimethylformamide, first stirred at 60 DEG C at a rotating speed of 200 r / min for 1 h, and then stirred at 120 DEG C at a rotating speed of 350 r / min for 24 h to prepare an amino-functionalized MOF; After the products obtained from a2 and a1 are cooled to 60°C, 8g of 4-boronic acid benzaldehyde is added, and the reaction is continued to be stirred at 350r / min for 8h to form an imine bond-linked MOF-COF composite material. a3. The product obtained in a2 was centrifuged at 4000 r / min for 10 min, then washed three times with N,N-dimethylformamide, 50 mL each time, and finally dried under vacuum at 100℃ for 12 h to obtain a white powdery bifunctional dynamic regulation carrier (each gram of bifunctional dynamic regulation carrier can adsorb 1.8-2.0 grams of water).

[0027] The preparation method of the ternary composite catalyst is as follows: b1. Dissolve 20g of citric acid and 10g of urea in 200mL of water, microwave the mixture at 500W for 10min, and then dialyze it with a dialysis bag with a molecular weight cutoff of 1000 for 48h to obtain a carbon quantum dot solution. b2. Mix 100 mL of carbon quantum dot solution with 1.0 g of europium nitrate and stir at 300 r / min for 1.5 h at 60 °C. Then add 5 g of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and sonicate at 300 W for 1 h. After freeze drying, obtain ternary composite catalyst powder (each gram of ternary composite catalyst contains 0.8-1.0 mmol of acidic active sites).

[0028] The preparation method of the synergistic additive is as follows: 12g of citric acid and 8g of 3-aminopropyltriethoxysilane are mixed and stirred at 250r / min for 4h at 50℃, and then the solvent is removed by rotary evaporation at 60℃ and -0.09MPa to obtain the synergistic additive.

[0029] Example 2: This embodiment discloses a method for dynamically covalently chemically controlling the synthesis of diethyl adipate, comprising the following steps: S1. In a 500mL four-necked flask equipped with a thermometer, a water separator, and a pH sensor, add 120g of adipic acid, 240mL of anhydrous ethanol, 8g of a bifunctional dynamic control support, 4g of a ternary composite catalyst, 2g of synergistic additive, and 150mL of a mixed solvent of cyclohexane and toluene in a volume ratio of 3:1. Adjust the initial pH to 8.5. Stir the mixture at 500r / min for 7h at 75℃. During the reaction, monitor the Eu content in the ternary composite catalyst using fluorescence spectroscopy. 3+ Real-time monitoring, with sampling and analysis every 30 minutes; S2. After the reaction is completed, the temperature is lowered to 25°C to separate and recover the bifunctional dynamic control support and the ternary composite catalyst. The filtrate is purged with CO2 to adjust the pH to 5.5. After releasing the captured water, the solution is distilled under reduced pressure at 90°C and -0.08 MPa to obtain diethyl adipate.

[0030] The preparation method of the bifunctional dynamic regulation carrier is as follows: a1. Dissolve 20g of ZrCl4 and 15g of 2-aminoterephthalic acid in 250mL of N,N-dimethylformamide. First, stir at 70℃ and 250r / min for 2h, then stir at 140℃ and 400r / min for 30h to prepare amino-functionalized MOF. After the products obtained from a2 and a1 were cooled to 60°C, 12g of 4-boronic acid benzaldehyde was added, and the reaction was continued to be stirred at 400r / min for 10h to form an imine bond-linked MOF-COF composite material. a3. The product obtained in a2 was centrifuged at 5000 r / min for 15 min, then washed three times with N,N-dimethylformamide, 50 mL each time, and finally dried under vacuum at 120℃ for 12 h to obtain a white powdery bifunctional dynamic regulation carrier (each gram of bifunctional dynamic regulation carrier can adsorb 1.8-2.0 grams of water).

[0031] The preparation method of the ternary composite catalyst is as follows: b1. Dissolve 25g of citric acid and 15g of urea in 250mL of water, microwave the mixture at 700W for 15min, and then dialyze it with a dialysis bag with a molecular weight cutoff of 1000 for 48h to obtain a carbon quantum dot solution. b2. Mix 100 mL of carbon quantum dot solution with 1.5 g of europium nitrate and stir at 350 r / min for 2 h at 60 °C. Then add 8 g of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and sonicate at 400 W for 1.2 h. After freeze drying, obtain ternary composite catalyst powder (each gram of ternary composite catalyst contains 0.8-1.0 mmol of acidic active sites).

[0032] The preparation method of the synergistic additive is as follows: 15g of citric acid and 10g of 3-aminopropyltriethoxysilane are mixed and stirred at 300r / min for 6h at 60℃, and then the solvent is removed by rotary evaporation at 70℃ and -0.09MPa to obtain the synergistic additive.

[0033] Example 3: This embodiment discloses a method for dynamically covalently chemically controlling the synthesis of diethyl adipate, comprising the following steps: S1. In a 500mL four-necked flask equipped with a thermometer, water separator, and pH sensor, add 100g of adipic acid, 200mL of anhydrous ethanol, 6g of bifunctional dynamic control support, 3g of ternary composite catalyst, 1.5g of synergistic additive, and 125mL of a mixed solvent of cyclohexane and toluene in a volume ratio of 3:1. Adjust the initial pH to 8.2. Stir the mixture at 475r / min for 6 hours at 72℃. During the reaction, monitor the Eu content in the ternary composite catalyst using fluorescence spectroscopy. 3+ Real-time monitoring, with sampling and analysis every 30 minutes; S2. After the reaction is completed, the temperature is lowered to 25°C to separate and recover the bifunctional dynamic control support and the ternary composite catalyst. The filtrate is purged with CO2 to adjust the pH to 5.2. After releasing the captured water, the solution is distilled under reduced pressure at 85°C and -0.08 MPa to obtain diethyl adipate.

[0034] The preparation method of the bifunctional dynamic regulation carrier is as follows: a1. Dissolve 17g of ZrCl4 and 12g of 2-aminoterephthalic acid in 225mL of N,N-dimethylformamide. Stir at 225r / min for 1.5h at 65℃, and then stir at 375r / min for 27h at 130℃ to prepare amino-functionalized MOF. After the products obtained from a2 and a1 were cooled to 60°C, 10g of 4-boronic acid benzaldehyde was added, and the reaction was continued to be stirred at 375r / min for 9h to form an imine bond-linked MOF-COF composite material. a3. The product obtained in a2 was centrifuged at 4500 r / min for 12 min, then washed three times with N,N-dimethylformamide, 50 mL each time, and finally vacuum dried at 110 °C for 12 h to obtain a white powdery bifunctional dynamic regulation carrier (each gram of bifunctional dynamic regulation carrier can adsorb 1.8-2.0 grams of water).

[0035] The preparation method of the ternary composite catalyst is as follows: b1. Dissolve 22g of citric acid and 12g of urea in 225mL of water, microwave the mixture at 600W for 12min, and then dialyze it with a dialysis bag with a molecular weight cutoff of 1000 for 48h to obtain a carbon quantum dot solution. b2. Mix 100 mL of carbon quantum dot solution with 1.2 g of europium nitrate and stir at 325 r / min for 1.7 h at 60 °C. Then add 6 g of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and sonicate at 350 W for 1.1 h. After freeze-drying, obtain ternary composite catalyst powder (each gram of ternary composite catalyst contains 0.8-1.0 mmol of acidic active sites).

[0036] The preparation method of the synergistic additive is as follows: 13g of citric acid and 9g of 3-aminopropyltriethoxysilane are mixed and stirred at 275r / min for 5h at 55℃. Then, the solvent is removed by rotary evaporation at 65℃ and -0.09MPa to obtain the synergistic additive.

[0037] Comparative Example 1: A method for the synthesis of diethyl adipate under dynamic covalent chemical regulation, the only difference between this method and Example 3 is that no bifunctional dynamic regulation carrier is added.

[0038] Comparative Example 2: A method for the dynamic covalent chemical regulation of the synthesis of diethyl adipate, the only difference between this method and Example 3 is that no ternary composite catalyst is added.

[0039] Comparative Example 3: A method for the dynamic covalent chemical regulation of the synthesis of diethyl adipate, the only difference between this method and Example 3 is that no synergistic additive is added.

[0040] Comparative Example 4: A method for the dynamic covalent chemical regulation synthesis of diethyl adipate, the only difference between this method and Example 3 is that a single borate ester regulator is used instead of a bifunctional dynamic regulation carrier.

[0041] Comparative Example 5: A method for the dynamic covalent chemical regulation of the synthesis of diethyl adipate, the only difference between this method and Example 3 is that the amount of ternary composite catalyst is halved.

[0042] Comparative Example 6: A method for the dynamic covalent chemical regulation of the synthesis of diethyl adipate, the only difference between this method and Example 3 is that in S2, the reaction temperature for the preparation of diethyl adipate is 60°C.

[0043] Comparative Example 7: A method for the dynamic covalent chemical regulation of the synthesis of diethyl adipate, the only difference between this method and Example 3 is that the initial pH in S1 is 7.0.

[0044] Comparative Example 8: A method for the dynamic covalent chemical regulation of the synthesis of diethyl adipate, the only difference between this method and Example 3 is that a traditional concentrated sulfuric acid catalyst is used instead of a ternary composite catalyst.

[0045] Comparative Example 9: A method for the dynamic covalent chemical regulation of the synthesis of diethyl adipate, the only difference between this method and Example 3 is that the filtrate is not treated with CO2.

[0046] Comparative Example 10: A method for the dynamic covalent chemical regulation of the synthesis of diethyl adipate, the only difference between this method and Example 3 is that toluene is used as a single solvent instead of the mixed solvent composed of cyclohexane and toluene in a volume ratio of 3:1.

[0047] The diethyl adipate prepared by the dynamic covalent chemically regulated synthesis method for diethyl adipate provided in Examples 1-3 and Comparative Examples 1-10 was subjected to performance tests for yield, purity, color, catalyst recovery, and reaction time. 1. Purity detection: Following GB / T6488-2008, gas chromatography (HP-5 column, FID detector) was used, and peak area normalization was applied. The detection conditions are as follows: Column temperature: Initially 80℃, hold for 2 min, then increase to 280℃ at 10℃ / min and hold for 5 min; Injection volume: 1 μL, split ratio 20:1.

[0048] 2. Colorimetric determination: Visual colorimetric determination was performed using APHA colorimetric tubes in accordance with GB / T7534-2004.

[0049] 3. Catalyst recovery rate: The catalyst recovered by filtration was washed three times with ethanol (30 mL each time), dried at 100℃ for 8 h, and then weighed for calculation.

[0050] The results are shown in Table 1.

[0051] Table 1 Performance parameters of diethyl adipate obtained in Examples 1-3 and Comparative Examples 1-10

[0052] Referring to Example 3, and considering Table 1, it can be seen that: In Comparative Example 1, without the addition of the bifunctional dynamic control support, the yield decreased to 68.3%, and the reaction time was extended by 6 hours, demonstrating that the dual action of "dehydration-supporting" dominates the reaction efficiency. Compared with a single borate ester regulator (Comparative Example 4), its dual dynamic bond synergistic mechanism increased the yield by 14% and the catalyst recovery by 14.2%. Due to the inability to effectively dehydrate, side reactions (such as residual monoethyl adipic acid ester) increased, and the purity decreased to 95.2%.

[0053] In Comparative Example 2, without the addition of the ternary composite catalyst, the reaction was almost inefficient, with a yield of only 45.7%. Comparative Example 8, using conventional concentrated sulfuric acid catalysis, achieved a yield of 82.4% but with poor product color, demonstrating the "green and efficient" characteristics of the ternary composite catalyst. Strong oxidizing properties led to the carbonization of a small amount of product, resulting in a purity of 95.8% (significantly lower than in the embodiments of this invention). Halving the amount (Comparative Example 5) resulted in a 7.1% decrease in yield, indicating that the concentration of the ternary composite catalyst has a significant impact on the reaction rate.

[0054] At temperatures below 70℃ (Comparative Example 6), the dynamic activity of the imine bond decreases, and the reaction rate drops by 30%. When the pH deviates from 8.0-8.5 (Comparative Example 7), the stability of the borate ester bond decreases, and the water trapping ability weakens by 25%. The mixed solvent (cyclohexane-toluene) shortens the reaction time by 8% compared to the single solvent through synergistic azeotropic effect (Comparative Example 10). The solvent azeotropic effect is weakened, and there are slightly more residual impurities, with a purity of 97.2%.

[0055] In Comparative Example 3, the yield decreased by 9.6% when the synergistic additive was missing, demonstrating that the reaction performance was improved through a synergistic effect of "assisted dehydration-catalyst protection". Without a bifunctional dynamically controlled support, the ternary composite catalyst lost its "anchoring" effect and dispersed in the solution, making it impossible to recover by filtration; therefore, the recovery rate was "-" (unrecoverable). Without the ternary composite catalyst, there was no catalyst component in the system; therefore, the recovery rate was "-" (no catalyst available for recovery).

[0056] This invention avoids the use of strong acids throughout the process, employing weakly acidic ionic liquids, thus reducing equipment corrosion by 90%. The catalyst recovery rate is >96%, achieving over 5 cycles with no significant performance degradation. The reaction temperature is ≤75℃, offering a significant advantage over traditional methods (120℃).

[0057] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for the dynamic covalent chemical regulation of diethyl adipate synthesis, characterized in that, The method includes the following steps: S1. In a 500mL four-necked flask equipped with a thermometer, water separator, and pH sensor, add 80-120g of adipic acid, 160-240mL of anhydrous ethanol, 5-8g of a bifunctional dynamic control support, 2-4g of a ternary composite catalyst, 1-2g of synergistic additive, and 100-150mL of a mixed solvent of cyclohexane and toluene. Adjust the initial pH to 8.0-8.

5. Stir the mixture at 450-500r / min for 6-8 hours at 70-75℃. During the reaction, monitor the Eu content in the ternary composite catalyst using fluorescence spectroscopy. 3+ Real-time monitoring; S2. After the reaction is completed, the temperature is lowered to 25℃ to separate and recover the bifunctional dynamic control support and the ternary composite catalyst. The filtrate is purged with CO2 to adjust the pH to 5.0-5.

5. After the captured water is released, the solution is distilled under reduced pressure at 80-90℃ and -0.08MPa to obtain diethyl adipate.

2. The method for dynamically covalently chemically controlling the synthesis of diethyl adipate according to claim 1, characterized in that, Eu by fluorescence spectroscopy 3+ During real-time monitoring, samples are taken and analyzed every 30 minutes.

3. The method for dynamically covalently chemically controlling the synthesis of diethyl adipate according to claim 1, characterized in that, The preparation method of the bifunctional dynamic regulation vector is as follows: a1. Dissolve 15-20g of ZrCl4 and 10-15g of 2-aminoterephthalic acid in 200-250mL of N,N-dimethylformamide. After pre-dissolving at low temperature, react the mixture at 120-140℃ and 350-400r / min for 24-30h to prepare amino-functionalized MOF. After cooling the products obtained from a2 and a1 to 60℃, 8-12g of 4-boronic acid benzaldehyde was added, and the reaction was continued to be stirred at 350-400r / min for 8-10h to form an imine bond-linked MOF-COF composite material. The products obtained from a3 and a2 were washed three times with N,N-dimethylformamide, 50 mL each time, and finally dried under vacuum at 100-120 °C for 12 h to obtain a white powdery bifunctional dynamic regulation carrier.

4. The method for dynamically covalently chemically controlling the synthesis of diethyl adipate according to claim 3, characterized in that, Each gram of the dual-function dynamic regulation carrier can adsorb 1.8-2.0 grams of water.

5. The method for dynamically covalently chemically controlling the synthesis of diethyl adipate according to claim 3, characterized in that, The specific steps for low-temperature pre-dissolution are as follows: stir at 60-70℃ at a speed of 200-250r / min for 1-2 hours.

6. The method for dynamically covalently chemically controlling the synthesis of diethyl adipate according to claim 5, characterized in that, In step a3, before washing with N,N-dimethylformamide, the material obtained in a2 needs to be centrifuged at a speed of 4000-5000 r / min for 10-15 min.

7. The method for dynamically covalently chemically controlling the synthesis of diethyl adipate according to claim 5, characterized in that, The preparation method of the ternary composite catalyst is as follows: b1. Dissolve 20-25g of citric acid and 10-15g of urea in 200-250mL of water, microwave the reaction at 500-700W for 10-15min, and then dialyze the solution with a dialysis bag with a molecular weight cutoff of 1000 for 48h to obtain a carbon quantum dot solution. b2. Mix 100 mL of carbon quantum dot solution with 1.0-1.5 g of europium nitrate and stir at 300-350 r / min for 1.5-2 h at 60 °C. Then add 5-8 g of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and sonicate at 300-400 W for 1-1.2 h. After freeze-drying, obtain ternary composite catalyst powder.

8. The method for dynamically covalently chemically controlling the synthesis of diethyl adipate according to claim 7, characterized in that, Each gram of ternary composite catalyst contains 0.8-1.0 mmol of acidic active sites.

9. The method for dynamically covalently chemically controlling the synthesis of diethyl adipate according to claim 7, characterized in that, The preparation method of the synergistic additive is as follows: take 12-15g of citric acid and 8-10g of 3-aminopropyltriethoxysilane, mix and stir them at 250-300r / min for 4-6h at 50-60℃, and then remove the solvent by rotary evaporation at 60-70℃ and -0.09MPa to obtain the synergistic additive.

10. The method for dynamically covalently chemically controlling the synthesis of diethyl adipate according to claim 7, characterized in that, In a mixed solvent composed of cyclohexane and toluene, the volume ratio of cyclohexane to toluene is 3:1.

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