Method for synthesizing high-purity L-lactide
By using molecular sieve and metal oxides to prepare catalysts in the process of synthesis of high optical purity L-lactides, the problems of catalyst recovery and contamination are solved, and high-purity products and low-cost production are achieved.
Patent Information
- Application Number
- CN202411606226.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-12
- Publication Date
- 2025-02-18
AI Technical Summary
The catalyst used in the prior art for the synthesis of high optical purity L-lactide cannot be recovered, resulting in environmental pollution and impurity treatment problems.
Using molecular sieve as support and metal oxide as active components, a metal oxide catalyst is formed by preparing a catalyst precursor and calcining, which is used to react with L-lactic acid to synthesize high-purity L-lactide.
The stability and ease of recycling of catalysts are achieved, product contamination is reduced, optical purity of L-lactide is improved, and raw material and equipment investment is reduced.
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Figure BDA0005129645860000081
Abstract
Description
Technical Field
[0001] The present application relates to the field of chemical production technology, and in particular to a method for synthesizing high-purity L-lactide. Background Art
[0002] In the prior art, a method for preparing L-lactide with high optical purity comprises the following steps: (1) mixing L-lactic acid and zinc salt for polymerization reaction; the mass of the zinc salt is 0.1-1.5% of the mass of the L-lactic acid raw material; (2) adding melamine and a co-catalyst after the reaction for cracking reaction; the mass of the melamine is 0.1-0.5% of the mass of the L-lactic acid; the co-catalyst is disodium 3-indole phosphate; (3) distilling and collecting the fractions, and condensing to obtain L-lactide with high optical purity.
[0003] In the above method, the catalyst cost is low, and L-lactide can be obtained at a high yield, which is suitable for industrial production. However, since the co-catalyst contains an indole ring, the NH in the indole ring can be hydrogen-bonded with the catalyst melamine, so that the molecule can be firmly attached to the surface of the melamine catalyst, resulting in the catalyst being unable to be recovered. There are problems with impurity treatment during the preparation of the catalyst, which may cause environmental pollution if not properly treated. Summary of the invention
[0004] The present application provides a method for synthesizing high-purity L-lactide, using molecular sieve as a carrier, metal oxide as an active component, and L-lactic acid as a raw material. The optical purity of the reaction product L-lactide is high; and the prepared catalyst has good stability, produces little pollution to the product, and is easy to recover after the reaction is completed. The specific technical scheme is as follows:
[0005] The present application provides a method for synthesizing high-purity L-lactide, comprising the following steps:
[0006] Preparation of a catalyst precursor: adding 2 to 5 g of molecular sieve to 15 ml of anhydrous ethanol to form a first mixed solution, dissolving 0.02 to 0.5 g of a metal salt in 25 ml of deionized water to form a second mixed solution, pouring the first mixed solution and the second mixed solution into a beaker and mixing them evenly to form a target liquid; heating the target liquid at 60 to 80° C. and stirring for 30 to 60 min, and placing it in an ultrasonic crusher for 1 to 2 h, repeating the process several times, and then placing it in an oven to dry, to obtain a catalyst precursor;
[0007] Preparation of a catalyst: grinding the prepared catalyst precursor and calcining it in a muffle furnace, wherein the calcination temperature is 450-700° C. and the calcination time is 4-8 hours, to obtain a catalyst including a metal oxide;
[0008] Synthesis of high-purity L-lactide: L-lactic acid and the prepared catalyst are added to a flask at a mass ratio of 5 to 15:1 and 15 to 25 ml of an azeotropic solvent for reaction, wherein the reaction temperature is 90 to 170° C. and the reaction time is 3 to 9 hours; after the reaction is completed, distill for 20 to 30 minutes to obtain high-purity L-lactide.
[0009] In some embodiments of the present application, the metal salt includes at least one of ferrous chloride, ferric chloride, aluminum chloride, zinc chloride, stannous chloride, tin tetrachloride, cupric chloride, and cuprous chloride.
[0010] In some embodiments of the present application, the molecular sieve includes at least one of ZSM-5, USY, H-Beta, 5A molecular sieve, and 3A molecular sieve.
[0011] In some embodiments of the present application, the step of repeating multiple times and then placing in an oven for drying specifically includes:
[0012] Repeat twice and then place in an oven to dry; the drying temperature is 80-100°C and the drying time is 6-8h.
[0013] In some embodiments of the present application, the heating rate of the calcination is 3-5°C / min, the calcination temperature is 450-600°C, and the calcination time is 5-7h.
[0014] In some embodiments of the present application, the mass ratio of L-lactic acid to catalyst is 5 to 10:1.
[0015] In some embodiments of the present application, the reaction temperature is 100-150° C., the reaction time is 4-8 hours, and distillation is performed for 20-30 minutes after the reaction is completed.
[0016] In some embodiments of the present application, the azeotropic solvent includes at least one of benzene, toluene, xylene, cyclohexane, and cyclopentane.
[0017] In some embodiments of the present application, the catalyst, L-lactic acid, and azeotropic solvent are stirred during the reaction, and the stirring is stopped after the reaction is completed.
[0018] In some embodiments of the present application, the volume of the flask is greater than or equal to 100 ml.
[0019] Beneficial effects of the present application: The present application provides a method for synthesizing high-purity L-lactide, which uses molecular sieves as carriers, metal oxides as active components, and L-lactic acid as raw materials. Not only is the raw material cost low and the preparation process simple, the reaction conditions are mild, the equipment investment is small, and the optical purity of the reaction product L-lactide is high; and the prepared catalyst has good stability, produces little pollution to the product, and is easy to recover after the reaction is completed. The prepared catalyst is particularly suitable for catalyzing the synthesis of lactide by direct polymerization of lactic acid, and is easy to separate after the reaction is completed. It is a heterogeneous catalyst with significant selective polymerization effect. DETAILED DESCRIPTION
[0020] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.
[0021] A method for synthesizing high-purity L-lactide provided in an embodiment of the present application uses a molecular sieve as a carrier, a metal oxide as an active component, and L-lactic acid as a raw material. Not only is the raw material cost low and the preparation process simple, the reaction conditions are mild, the equipment investment is small, and the optical purity of the reaction product L-lactide is high; the prepared catalyst has good stability, produces little pollution to the product, and is easy to recover after the reaction is completed. The prepared catalyst is particularly suitable for catalyzing the synthesis of lactide by direct polymerization of lactic acid, and is a heterogeneous catalyst with significant selective polymerization effect.
[0022] The present application provides a method for synthesizing high-purity L-lactide, comprising the following steps:
[0023] Preparation of catalyst precursor: Add 2-5g molecular sieve into 15ml anhydrous ethanol to form a first mixed solution, dissolve 0.02-0.5g metal salt into 25ml deionized water to form a second mixed solution, pour the first mixed solution and the second mixed solution into a beaker and mix them evenly to form a target liquid; heat the target liquid at 60-80°C and stir for 30-60min, and place it in an ultrasonic crusher for 1-2h, repeat several times and place it in an oven to dry to obtain a catalyst precursor. The ultrasonic crusher is used to provide an ultrasonic environment for the target liquid.
[0024] Preparation of catalyst: Grind the prepared catalyst precursor and place it in a muffle furnace for calcination, wherein the calcination heating rate is 3-6°C / min, the calcination temperature is 450-700°C, and the calcination time is 4-8h to obtain a metal oxide catalyst, wherein the metal oxide is the active component in the catalyst.
[0025] Synthesis of high-purity L-lactide: L-lactic acid and the prepared catalyst are added to a flask at a mass ratio of 5 to 15:1 and 15 to 25 ml of an azeotropic solvent for reaction, wherein the reaction temperature is 90 to 170° C. and the reaction time is 3 to 9 hours; after the reaction is completed, distill for 20 to 30 minutes to obtain high-purity L-lactide.
[0026] In some embodiments of the present application, the metal salt includes at least one of ferrous chloride, ferric chloride, aluminum chloride, zinc chloride, stannous chloride, tin tetrachloride, cupric chloride, and cuprous chloride.
[0027] In some embodiments of the present application, the molecular sieve includes at least one of ZSM-5, USY, H-Beta, 5A molecular sieve, and 3A molecular sieve.
[0028] In some embodiments of the present application, the process is repeated multiple times and then placed in an oven for drying, specifically comprising:
[0029] Repeat twice and then place in an oven to dry; the drying temperature is 80-100°C and the drying time is 6-8h.
[0030] In some embodiments of the present application, the heating rate of the calcination is 3-5°C / min, the calcination temperature is 450-600°C, and the calcination time is 5-7h.
[0031] In some embodiments of the present application, the mass ratio of L-lactic acid to catalyst is 5 to 10:1.
[0032] In some embodiments of the present application, the reaction temperature is 100-150° C., the reaction time is 4-8 hours, and distillation is performed for 20-30 minutes after the reaction is completed.
[0033] In some embodiments of the present application, the azeotropic solvent includes at least one of benzene, toluene, xylene, cyclohexane, and cyclopentane.
[0034] In some embodiments of the present application, the catalyst, L-lactic acid, and azeotropic solvent are stirred during the reaction, and the stirring is stopped after the reaction is completed.
[0035] In some embodiments of the present application, the volume of the flask is greater than or equal to 100 ml. Exemplarily, the volume of the flask can be 100 ml, which is convenient for reading.
[0036] The present application provides a method for synthesizing high-purity L-lactide, which uses molecular sieves as carriers, metal oxides as active components, and L-lactic acid as raw materials. The method has low raw material costs and a simple preparation process, mild reaction conditions, and low equipment investment, and the optical purity of the reaction product L-lactide is high; the prepared catalyst has good stability, produces little pollution to the product, and is easy to recover after the reaction is completed. The prepared catalyst is particularly suitable for catalyzing the synthesis of lactide by direct polymerization of lactic acid, and is easy to separate after the reaction is completed, and is a heterogeneous catalyst with significant selective polymerization effect.
[0037] A method for synthesizing high-purity L-lactide of the present application will be described in detail below with reference to specific embodiments.
[0038] Example 1
[0039] A method for synthesizing high-purity L-lactide, which method requires first preparing a catalyst, and then synthesizing high-purity L-lactide based on the prepared catalyst; wherein the metal oxide is SnO2, the molecular sieve is ZSM-5, and the weight content of SnO2 in the prepared catalyst is 2%. The preparation method is as follows:
[0040] (1) Weigh 2.5 g of ZSM-5 and add it to 15 ml of anhydrous ethanol. At the same time, weigh 0.0749 g of stannous chloride dihydrate and dissolve it in 25 ml of deionized water. Pour the two into a beaker and mix them evenly. Then, heat and stir them at 80°C for 30 min with a heating stirrer and place them in an ultrasonic environment provided by an ultrasonic crusher for 1 h. Repeat this twice and then place them in an oven to dry.
[0041] (2) The catalyst precursor in the beaker is ground and then calcined in a muffle furnace, wherein the calcination temperature is 600°C and the calcination time is 5 hours. The metal oxide SnO2 is generated during the calcination process.
[0042] (3) The prepared catalyst, L-lactic acid, and azeotropic solvent were added to a flask for reaction, wherein the mass ratio of L-lactic acid to catalyst was 14:1, the azeotropic solvent was 15 ml, the reaction temperature was 90°C, and the reaction time was 5 h; after the reaction was completed, the reaction was distilled for 30 min and the product was collected.
[0043] Example 2
[0044] A method for synthesizing high-purity L-lactide, which method requires first preparing a catalyst, and then synthesizing high-purity L-lactide based on the prepared catalyst; wherein the metal oxide is SnO2, the molecular sieve is H-Beta, and the weight content of SnO2 in the prepared catalyst is 2%. The preparation method is as follows:
[0045] (1) Weigh 2.5 g of H-Beta and add it to 15 ml of anhydrous ethanol. At the same time, weigh 0.0749 g of stannous chloride dihydrate and dissolve it in 25 ml of deionized water. Pour the two into a beaker and mix them evenly. Then, heat and stir them at 80°C for 30 min with a heating stirrer and place them in an ultrasonic environment provided by an ultrasonic crusher for 1 h. Repeat this twice and then place them in an oven to dry.
[0046] (2) The catalyst precursor in the beaker is ground and then calcined in a muffle furnace, wherein the calcination temperature is 600°C and the calcination time is 5 hours. The metal oxide SnO2 is generated during the calcination process.
[0047] (3) The prepared catalyst, L-lactic acid, and azeotropic solvent were added to a flask for reaction, wherein the mass ratio of L-lactic acid to catalyst was 14:1, the azeotropic solvent was 15 ml, the reaction temperature was 90°C, and the reaction time was 5 h; after the reaction was completed, the reaction was distilled for 30 min and the product was collected.
[0048] Example 3
[0049] A method for synthesizing high-purity L-lactide, which method requires first preparing a catalyst, and then synthesizing high-purity L-lactide based on the prepared catalyst; wherein the metal oxide is ZnO, the molecular sieve is ZSM-5, and the weight content of ZnO in the prepared catalyst is 2%. The preparation method is as follows:
[0050] (1) Weigh 2.5 g of ZSM-5 and add it to 15 ml of anhydrous ethanol. At the same time, weigh 0.0837 g of zinc chloride and dissolve it in 25 ml of deionized water. Pour the two into a beaker and mix them evenly. Then, heat and stir them at 80°C for 30 min with a heating stirrer and place them in an ultrasonic environment provided by an ultrasonic crusher for 1 h. Repeat this twice and then place them in an oven to dry.
[0051] (2) The catalyst precursor in the beaker is ground and then calcined in a muffle furnace, wherein the calcination temperature is 600°C and the calcination time is 5 hours. The metal oxide generated during the calcination process is ZnO.
[0052] (3) The prepared catalyst, L-lactic acid, and azeotropic solvent were added to a flask for reaction, wherein the mass ratio of L-lactic acid to catalyst was 14:1, the azeotropic solvent was 15 ml, the reaction temperature was 90°C, and the reaction time was 5 h; after the reaction was completed, the reaction was distilled for 30 min and the product was collected.
[0053] Example 4
[0054] A method for synthesizing high-purity L-lactide, which method requires first preparing a catalyst, and then synthesizing high-purity L-lactide based on the prepared catalyst; wherein the metal oxide is ZnO, the molecular sieve is H-Beta, and the weight content of ZnO in the prepared catalyst is 2%. The preparation method is as follows:
[0055] (1) Weigh 2.5 g of H-Beta and add it to 15 ml of anhydrous ethanol. At the same time, weigh 0.0837 g of zinc chloride and dissolve it in 25 ml of deionized water. Pour the two into a beaker and mix them evenly. Then, heat and stir them at 80°C for 30 min with a heating stirrer and place them in an ultrasonic environment provided by an ultrasonic crusher for 1 h. Repeat this twice and then place them in an oven to dry.
[0056] (2) The catalyst precursor in the beaker is ground and then calcined in a muffle furnace, wherein the calcination temperature is 600°C and the calcination time is 5 hours. The metal oxide generated during the calcination process is ZnO.
[0057] (3) The prepared catalyst, L-lactic acid, and azeotropic solvent were added to a flask for reaction, wherein the mass ratio of L-lactic acid to catalyst was 14:1, the azeotropic solvent was 15 ml, the reaction temperature was 90°C, and the reaction time was 5 h; after the reaction was completed, the reaction was distilled for 30 min and the product was collected.
[0058] Example 5
[0059] A method for synthesizing high-purity L-lactide, which method requires first preparing a catalyst, and then synthesizing high-purity L-lactide based on the prepared catalyst; wherein the metal oxides are SnO2 and ZnO, the molecular sieve is H-Beta, and the weight content of SnO2 and ZnO in the prepared catalyst is 1%. The preparation method is as follows:
[0060] (1) Weigh 2.5 g of H-Beta and add it to 15 ml of anhydrous ethanol. At the same time, weigh 0.0419 g of zinc chloride and 0.0375 g of stannous chloride dihydrate and dissolve them in 25 ml of deionized water. Pour the two into a beaker and mix them evenly. Then, heat and stir at 80°C for 30 min with a heating stirrer and place it in an ultrasonic environment provided by an ultrasonic crusher for 1 h. Repeat this process several times and then place it in an oven to dry.
[0061] (2) The catalyst precursor in the beaker is ground and then calcined in a muffle furnace, wherein the calcination temperature is 600°C and the calcination time is 5 hours. The metal oxides generated during the calcination process are SnO2 and ZnO.
[0062] (3) The prepared catalyst, L-lactic acid, and azeotropic solvent were added to a flask for reaction, wherein the mass ratio of L-lactic acid to catalyst was 14:1, the azeotropic solvent was 15 ml, the reaction temperature was 90°C, and the reaction time was 5 h; after the reaction was completed, the reaction was distilled for 30 min and the product was collected.
[0063] The reaction products of the high-purity L-lactide synthesized in Examples 1 to 5 were subjected to high performance liquid chromatography (HPLC) analysis. The HPLC analysis method was: C18 chromatographic column (250×4.6 mm); PDA detector; the mobile phase was chromatographic grade acetonitrile at a flow rate of 1.0 ml·min -1 , the detection wavelength is 200nm; the injection volume is 10ul. The product yield is calculated by combining the external standard method. The gas chromatography results show that the product shows good optical purity. The reaction results are shown in the following table.
[0064] Table 1: Reaction product distribution
[0065]
[0066] According to Table 1 above, in the preparation method for synthesizing high-purity L-lactide shown in Example 5, the yield of lactide is significantly improved and can reach 80.35%.
[0067] Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present application without departing from the spirit and scope of the embodiments of the present application. Thus, if these modifications and variations of the embodiments of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.
Claims
1. A method for synthesizing high-purity L-lactide, characterized in that: The following steps are involved: Preparation of a catalyst precursor: adding 2 to 5 g of molecular sieve to 15 ml of anhydrous ethanol to form a first mixed solution, dissolving 0.02 to 0.5 g of a metal salt in 25 ml of deionized water to form a second mixed solution, pouring the first mixed solution and the second mixed solution into a beaker and mixing them evenly to form a target liquid; heating the target liquid at 60 to 80° C. and stirring for 30 to 60 min, and placing it in an ultrasonic crusher for 1 to 2 h, repeating the process several times, and then placing it in an oven to dry, to obtain a catalyst precursor; Preparation of a catalyst: grinding the prepared catalyst precursor and calcining it in a muffle furnace, wherein the calcination temperature is 450-700° C. and the calcination time is 4-8 hours, to obtain a catalyst including a metal oxide; Synthesis of high-purity L-lactide: L-lactic acid and the prepared catalyst are added to a flask at a mass ratio of 5 to 15:1 and 15 to 25 ml of an azeotropic solvent for reaction, wherein the reaction temperature is 90 to 170° C. and the reaction time is 3 to 9 hours; after the reaction is completed, distill for 20 to 30 minutes to obtain high-purity L-lactide.
2. The method for synthesizing high-purity L-lactide according to claim 1, characterized in that: The metal salt includes at least one of ferrous chloride, ferric chloride, aluminum chloride, zinc chloride, stannous chloride, tin tetrachloride, cupric chloride and cuprous chloride.
3. The method for synthesizing high-purity L-lactide according to claim 1, characterized in that: The molecular sieve includes at least one of ZSM-5, USY, H-Beta, 5A molecular sieve, and 3A molecular sieve.
4. The method for synthesizing high-purity L-lactide according to claim 1, characterized in that: The method of repeating the steps several times and then placing the steps in an oven for drying specifically comprises: Repeat twice and then place in an oven to dry; the drying temperature is 80-100°C and the drying time is 6-8h.
5. The method for synthesizing high-purity L-lactide according to claim 1, characterized in that: The heating rate of the calcination is 3-5°C / min, the calcination temperature is 450-600°C, and the calcination time is 5-7h.
6. The method for synthesizing high-purity L-lactide according to claim 1, characterized in that: The mass ratio of the L-lactic acid to the catalyst is 5 to 10:
1.
7. The method for synthesizing high-purity L-lactide according to claim 1, characterized in that: The reaction temperature is 100-150° C., and the reaction time is 4-8 hours. After the reaction is completed, distillation is performed for 20-30 minutes.
8. The method for synthesizing high-purity L-lactide according to claim 1, characterized in that: The azeotropic solvent includes at least one of benzene, toluene, xylene, cyclohexane and cyclopentane.
9. The method for synthesizing high-purity L-lactide according to claim 1, characterized in that: The catalyst, L-lactic acid and azeotropic solvent are stirred during the reaction, and the stirring is stopped after the reaction is completed.