CN108047190B - Method for producing D-lactide by using D-lactic acid - Google Patents
Method for producing D-lactide by using D-lactic acid Download PDFInfo
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Abstract
The invention discloses a method for producing D-lactide by using D-lactic acid, which comprises the following steps: (1) preparing raw materials: 35-60 wt% of D-lactic acid solution, wherein the optical purity of the D-lactic acid is more than or equal to 99.5%; (2) dehydrating and oligomerizing to obtain D-lactic acid oligomer; (3) d-lactide is prepared by depolymerizing D-lactic acid oligomer. The method for producing the D-lactide by using the D-lactic acid can obtain the lactic acid oligomer with narrower molecular weight distribution, and the yield and the optical purity of the D-lactide prepared by using the lactic acid oligomer as the raw material are high.
Description
Technical Field
The invention relates to the technical field of lactic acid deep processing. And more particularly, to a method for producing D-lactide using D-lactic acid.
Background
The polylactic acid is a polymer with excellent performance, biocompatibility and biodegradability, and is mainly used for degradable packaging materials and medical materials such as drug microsphere carriers, anti-adhesion films, biological catheters, orthopedic fixtures, orthopedic surgery devices, artificial bones and the like.
In the process of preparing polylactic acid by monomer lactic acid, firstly, the monomer lactic acid is used for generating lactic acid oligomer, and then the lactic acid oligomer is directly condensed to prepare the polylactic acid, or the lactic acid oligomer is used for preparing lactide, and then the lactide is subjected to ring-opening polymerization to generate the polylactic acid. Among them, the lactide ring-opening polymerization is used to prepare polylactic acid with high molecular weight, and thus, it is the current first choice.
The present inventors have found that an oligolactic acid can be used not only as a starting material for the preparation of polylactic acid but also as a pharmaceutical intermediate, and chinese patent document CN1498237A discloses a method for preparing a lactic acid oligomer, which uses lactide as a raw material and can selectively prepare a mixture of linear and cyclic oligolactic acids. The disadvantages of this method are: (1) lactide is required to be used as a raw material, but in industrial production, lactic acid monomers are used as the most cheap raw materials, the cost for directly preparing the lactide from the lactic acid monomers is high, and only the byproduct lactide in melt polycondensation can be used as the raw material; (2) the used solvents such as tetrahydrofuran are toxic and are not suitable for industrial application.
Disclosure of Invention
An object of the present invention is to provide a method for producing a D-lactic acid oligomer using a D-lactic acid monomer and producing D-lactide.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for producing D-lactide by using D-lactic acid, comprising the steps of:
(1) preparing raw materials: 40-60 wt% of D-lactic acid solution, wherein the optical purity of the D-lactic acid is more than or equal to 99.5%;
(2) dehydrating and oligomerizing to obtain D-lactic acid oligomer;
(3) d-lactide is prepared by depolymerizing D-lactic acid oligomer.
In the method for producing D-lactide by using D-lactic acid, in the step (2), ethyl pyruvate is added into the D-lactic acid solution, and the volume ratio of the ethyl pyruvate to the D-lactic acid solution is 0.5-1: 1; simultaneously adding cobalt oxide and di-cysteine methyl ester vanadyl as catalysts into the mixed solution, and stirring; the usage amount of the cobalt oxide is 0.02-0.04 percent of the mass of the D-lactic acid, and the usage amount of the di-cysteine methyl ester vanadyl is 0.04-0.08 percent of the mass of the D-lactic acid; the reaction time is 3-6 h, and the reaction temperature is 5-30 ℃.
The above method for producing D-lactide using D-lactic acid, in step (2):
initial reaction: the mass ratio of the added cobalt oxide to the added di-cysteine methyl ester vanadyl is 1:1.5, and the addition amount of the cobalt oxide in the initial reaction is 1/2 of the total addition amount of the cobalt oxide; the reaction temperature is kept between 5 and 10 ℃ from the initial reaction to the time when one half of the reaction time is passed;
when the reaction time is one-half elapsed: adding all the residual di-cysteine methyl ester vanadyl into a reaction kettle; the reaction temperature is kept between 15 and 20 ℃ from one half of the reaction time to three quarters of the reaction time;
three quarters of the time elapsed: adding the rest cobalt oxide into the reaction kettle; the reaction temperature is kept between 25 and 30 ℃ from the end of the reaction to the end of the reaction after three quarters of the reaction time.
In the above method for producing D-lactide from D-lactic acid, in step (2), the preparation method of di-cysteine methyl ester vanadyl comprises: mixing and stirring cysteine methyl ester and vanadyl sulfate in boric acid solution at room temperature, and reacting for 3-5h to obtain purple solid; the amount ratio of the cysteine methyl ester to the vanadyl sulfate substance is 5:1, and the concentration of the cysteine methyl ester in the boric acid solution is 0.1-5 mol/L.
In the method for producing D-lactide by using D-lactic acid, in the step (2), after the reaction is finished, filtering, standing for layering, separating out an organic phase, and washing the organic phase with water; and (4) carrying out vacuum distillation on the organic phase after washing by water to remove the solvent, thus obtaining a white solid.
In the step (3), the D-lactic acid oligomer obtained in the step (2) is put into a lactide preparation kettle, and the temperature is raised to 145-160 ℃ to melt the D-lactic acid oligomer; the catalyst used for synthesizing the D-lactide is a mixture of nickel oxide and molybdenum glycinate, the usage amount of the nickel oxide is 0.01-0.03 percent of the mass of the D-lactic acid oligomer, the usage amount of the molybdenum glycinate is 0.03-0.09 percent of the mass of the D-lactic acid oligomer, the reaction time is 3-5h, and the reaction time is 3-5hThe stress is 0.01X 105Pa-0.1×105Pa；
Initial reaction: the mass ratio of the added nickel oxide to the added molybdenum glycinate is 1:2, and the addition amount of the nickel oxide during the initial reaction is 1/3 of the total addition amount of the nickel oxide;
when one third of the reaction time has elapsed: adding the rest nickel oxide into the lactide preparation kettle;
two thirds of the reaction time elapsed: the remaining molybdenum glycinate was added to the lactide preparation kettle in its entirety.
In the above method for producing D-lactide from D-lactic acid, in step (3), the preparation method of molybdenum glycinate is: mixing and stirring sodium molybdate and glycine hydroxy acid in a methanol solution at room temperature, and reacting for 2-3h to obtain solid molybdenum glycine hydroxy acid; the weight ratio of glycine hydroxy acid to sodium molybdate is 4:1, and the concentration of sodium molybdate in the methanol solution is 0.1-2 mol/L.
In the method for producing D-lactide by using D-lactic acid, in the step (3), the upper part of the lactide preparation kettle is communicated with the condensation collection tank through the heat insulation pipeline, and the generated D-lactide is cooled and crystallized in the condensation collection tank.
The invention has the following beneficial effects:
(1) the method takes cheap and easily-obtained D-lactic acid monomer in actual industrial production as raw material, is worth of D-lactic acid oligomer with narrow molecular weight distribution, has mild reaction condition, easy control and high yield of D-lactic acid oligomer, and is suitable for industrial production.
(2) The lactide is prepared by using the D-lactic acid oligomer as a raw material, the yield and the purity of the lactide are high, the reaction pressure is improved, and energy is saved in industrial production.
Detailed Description
In order to more clearly illustrate the invention, the invention is further described below in connection with preferred embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.
Example 1
A method for producing D-lactide by using D-lactic acid, comprising the steps of:
(1) preparing raw materials: the optical purity of the D-lactic acid produced by the applicant is greater than or equal to 99.5% in a 40 wt% D-lactic acid solution;
(2) dehydrating and oligomerizing to obtain D-lactic acid oligomer;
adding ethyl pyruvate into the D-lactic acid solution, and stirring to obtain a mixed solution, wherein the volume ratio of the ethyl pyruvate to the D-lactic acid solution is 1: 1;
simultaneously, cobalt oxide and di-cysteine methyl ester vanadyl are added into the mixed solution as catalysts according to the following steps:
initial reaction (0 h): the mass ratio of the added cobalt oxide to the added di-cysteine methyl ester vanadyl is 1:1.5, and the addition amount of the cobalt oxide in the initial reaction is 1/2 of the total addition amount of the cobalt oxide; the reaction temperature was kept at 5 ℃ from the initial reaction to the time when one-half of the reaction time elapsed; stirring;
when the reaction time is one half (2 h): adding all the residual di-cysteine methyl ester vanadyl into a reaction kettle; the reaction temperature is kept at 15 ℃ from one half of the reaction time to three quarters of the reaction time; stirring;
three quarters of the reaction time had elapsed (3 h): adding the rest cobalt oxide into the reaction kettle; the reaction temperature is kept at 25 ℃ from three quarters of the reaction time to the end of the reaction; and (4) stirring.
The using amount of the cobalt oxide is 0.02 percent of the mass of the D-lactic acid, and the using amount of the di-cysteine methyl ester vanadyl is 0.04 percent of the mass of the D-lactic acid; the preparation method of di-cysteine methyl ester vanadyl comprises the following steps: mixing and stirring cysteine methyl ester and vanadyl sulfate in boric acid solution at room temperature, and reacting for 3-5h to obtain purple solid; the quantity ratio of the cysteine methyl ester to the vanadyl sulfate substance is 5:1, and the concentration of the cysteine methyl ester in the boric acid solution is 2 mol/L.
After the reaction is finished, filtering, standing for layering, separating out an organic phase, and washing the organic phase with water; and (3) carrying out vacuum distillation on the organic phase after washing by water to remove the solvent, thus obtaining a white solid, and carrying out fast atom bombardment mass spectrum and nuclear magnetic detection on the obtained white solid, wherein the white solid is the D-lactic acid oligomer of the 6-19 polymer, and the yield of the D-lactic acid oligomer is 95%.
(3) D-lactide is prepared by depolymerizing D-lactic acid oligomer;
putting the D-lactic acid oligomer obtained in the step (2) into a lactide preparation kettle, and conducting the upper part of the lactide preparation kettle with a fluid of a condensation collection tank through a heat insulation pipeline; heating the lactide preparation kettle to 145 ℃ to melt the D-lactic acid oligomer;
the mixture of nickel oxide and molybdenum glycinate was added as catalyst to the lactide preparation kettle according to the following procedure (nickel oxide used in an amount of 0.01% of the mass of the D-lactic acid oligomer, molybdenum glycinate used in an amount of 0.03% of the mass of the D-lactic acid oligomer, reaction time of 3h, reaction pressure of 0.01X 105Pa)：
Initial reaction (0 h): the mass ratio of the added nickel oxide to the added molybdenum glycinate is 1:2, and the addition amount of the nickel oxide during the initial reaction is 1/3 of the total addition amount of the nickel oxide;
when one third of the reaction time has elapsed (1 h): adding the rest nickel oxide into the lactide preparation kettle;
when two thirds of the reaction time had elapsed (2 h): the remaining molybdenum glycinate was added to the lactide preparation kettle in its entirety.
The preparation method of molybdenum glycinate comprises the following steps: mixing and stirring sodium molybdate and glycine hydroxy acid in a methanol solution at room temperature, and reacting for 3 hours to obtain solid molybdenum glycine hydroxy acid; the weight ratio of glycine hydroxy acid to sodium molybdate is 4:1, and the concentration of sodium molybdate in the methanol solution is 2 mol/L.
The generated D-lactide is cooled and crystallized in a condensation collection tank, the yield of the D-lactide is 97.1 percent, and the optical purity is 99.9 percent.
Example 2
A method for producing D-lactide by using D-lactic acid, comprising the steps of:
(1) preparing raw materials: the optical purity of the D-lactic acid produced by the applicant is greater than or equal to 99.5% in a 60 wt% D-lactic acid solution;
(2) dehydrating and oligomerizing to obtain D-lactic acid oligomer;
adding ethyl pyruvate into the D-lactic acid solution, and stirring to obtain a mixed solution, wherein the volume ratio of the ethyl pyruvate to the D-lactic acid solution is 1: 1; adding cobalt oxide and di-cysteine methyl ester vanadyl as catalysts into the mixed solution; the using amount of the cobalt oxide is 0.04 percent of the mass of the D-lactic acid, the using amount of the di-cysteine methyl ester vanadyl is 0.08 percent of the mass of the D-lactic acid, and the mixture is stirred and reacted for 3 hours at room temperature; the preparation method of di-cysteine methyl ester vanadyl comprises the following steps: mixing and stirring cysteine methyl ester and vanadyl sulfate in boric acid solution at room temperature, and reacting for 3-5h to obtain purple solid; the quantity ratio of the cysteine methyl ester to the vanadyl sulfate substance is 5:1, and the concentration of the cysteine methyl ester in the boric acid solution is 0.5 mol/L.
After the reaction is finished, filtering, standing for layering, separating out an organic phase, and washing the organic phase with water; carrying out vacuum distillation on the organic phase after washing with water to remove the solvent, thus obtaining a white solid, and carrying out fast atom bombardment mass spectrum and nuclear magnetic detection on the obtained white solid, wherein the white solid contains a D-lactic acid oligomer of 6-19 polymers and a D-lactic acid oligomer of 30-50 polymers; the yield of D-lactic acid oligomer was 82%.
(3) D-lactide is prepared by depolymerizing D-lactic acid oligomer;
putting the D-lactic acid oligomer obtained in the step (2) into a lactide preparation kettle, and conducting the upper part of the lactide preparation kettle with a fluid of a condensation collection tank through a heat insulation pipeline; heating the lactide preparation kettle to 150 ℃ to melt the D-lactic acid oligomer; a mixture of nickel oxide and molybdenum glycinate carboxylate was added as catalyst to the lactide preparation kettle:
initial reaction (0 h): the mass ratio of the added nickel oxide to the added molybdenum glycinate is 1:2, and the addition amount of the nickel oxide during the initial reaction is 1/3 of the total addition amount of the nickel oxide;
when one third of the reaction time has elapsed (1 h): adding the rest molybdenum glycinate into the lactide preparation kettle;
three quarters of the reaction time had elapsed (2 h): adding the rest nickel oxide into the lactide preparation kettle.
The usage amount of nickel oxide is 0.03 percent of the quality of the D-lactic acid oligomer, the usage amount of molybdenum glycinate carboxylate is 0.09 percent of the quality of the D-lactic acid oligomer, the reaction time is 3 hours, and the reaction pressure is 0.1 multiplied by 105Pa; the preparation method of molybdenum glycinate comprises the following steps: mixing and stirring sodium molybdate and glycine hydroxy acid in a methanol solution at room temperature, and reacting for 3 hours to obtain solid molybdenum glycine hydroxy acid; the quantity ratio of glycine hydroxy acid and sodium molybdate substances is 4:1, and the concentration of sodium molybdate in the methanol solution is 1 mol/L.
The generated D-lactide is cooled and crystallized in a condensation collection tank, the yield of the D-lactide is 86.5 percent, and the optical purity is 99.9 percent.
Example 3
A method for producing D-lactide by using D-lactic acid, comprising the steps of:
(1) preparing raw materials: the optical purity of the D-lactic acid produced by the applicant is greater than or equal to 99.5% in a 50 wt% D-lactic acid solution;
(2) dehydrating and oligomerizing to obtain D-lactic acid oligomer;
adding ethyl pyruvate into the D-lactic acid solution, and stirring to obtain a mixed solution, wherein the volume ratio of the ethyl pyruvate to the D-lactic acid solution is 1: 1;
simultaneously, cobalt oxide and di-cysteine methyl ester vanadyl are added into the mixed solution as catalysts according to the following steps:
initial reaction (0 h): the mass ratio of the added cobalt oxide to the added di-cysteine methyl ester vanadyl is 1:1.5, and the addition amount of the cobalt oxide in the initial reaction is 1/2 of the total addition amount of the cobalt oxide; the reaction temperature was kept at 10 ℃ from the initial reaction to the time when one-half of the reaction time elapsed; stirring;
when the reaction time was one-half (3 h): adding the rest cobalt oxide into the reaction kettle; the reaction temperature is kept at 15 ℃ from one half of the reaction time to three quarters of the reaction time; stirring;
three quarters of the reaction time had elapsed (4.5 h): adding all the residual di-cysteine methyl ester vanadyl into a reaction kettle; the reaction temperature is kept at 30 ℃ from three quarters of the reaction time to the end of the reaction; and (4) stirring.
The using amount of the cobalt oxide is 0.03 percent of the mass of the D-lactic acid, and the using amount of the di-cysteine methyl ester vanadyl is 0.06 percent of the mass of the D-lactic acid; the preparation method of di-cysteine methyl ester vanadyl comprises the following steps: mixing and stirring cysteine methyl ester and vanadyl sulfate in boric acid solution at room temperature, and reacting for 3-5h to obtain purple solid; the quantity ratio of the cysteine methyl ester to the vanadyl sulfate substance is 5:1, and the concentration of the cysteine methyl ester in the boric acid solution is 1 mol/L.
After the reaction is finished, filtering, standing for layering, separating out an organic phase, and washing the organic phase with water; and (3) carrying out vacuum distillation on the organic phase after washing by water to remove the solvent, thus obtaining a white solid, and carrying out fast atom bombardment mass spectrum and nuclear magnetic detection on the obtained white solid, wherein the white solid is the D-lactic acid oligomer of the 6-40 polymer, and the yield of the D-lactic acid oligomer is 90%.
(3) D-lactide is prepared by depolymerizing D-lactic acid oligomer;
putting the D-lactic acid oligomer obtained in the step (2) into a lactide preparation kettle, and conducting the upper part of the lactide preparation kettle with a fluid of a condensation collection tank through a heat insulation pipeline; heating the lactide preparation kettle to 160 ℃ to melt the D-lactic acid oligomer; adding a mixture of nickel oxide and molybdenum glycinate as a catalyst into a lactide preparation kettle; the usage amount of nickel oxide is 0.02 percent of the quality of the D-lactic acid oligomer, the usage amount of molybdenum glycinate carboxylate is 0.06 percent of the quality of the D-lactic acid oligomer, the reaction time is 5 hours, and the reaction pressure is 0.05 multiplied by 105Pa; the preparation method of molybdenum glycinate comprises the following steps: mixing and stirring sodium molybdate and glycine hydroxy acid in a methanol solution at room temperature, and reacting for 3 hours to obtain solid molybdenum glycine hydroxy acid; the quantity ratio of glycine hydroxy acid and sodium molybdate substances is 4:1, and the concentration of sodium molybdate in the methanol solution is 1 mol/L.
The generated D-lactide is cooled and crystallized in a condensation collection tank, the yield of the D-lactide is 73.1 percent, and the optical purity is 99.9 percent.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.
Claims (7)
1. A method for producing D-lactide by using D-lactic acid, which is characterized by comprising the following steps:
(1) preparing raw materials: 35-60 wt% of D-lactic acid solution, wherein the optical purity of the D-lactic acid is more than or equal to 99.5%;
(2) dehydrating and oligomerizing to obtain D-lactic acid oligomer;
(3) d-lactide is prepared by depolymerizing D-lactic acid oligomer;
in the step (2), adding ethyl pyruvate into the D-lactic acid solution, wherein the volume ratio of the ethyl pyruvate to the D-lactic acid solution is 0.5-1: 1; simultaneously adding cobalt oxide and di-cysteine methyl ester vanadyl as catalysts into the mixed solution, and stirring; the usage amount of the cobalt oxide is 0.02-0.04 percent of the mass of the D-lactic acid, and the usage amount of the di-cysteine methyl ester vanadyl is 0.04-0.08 percent of the mass of the D-lactic acid; the reaction time is 3-6 h, and the reaction temperature is 5-30 ℃.
2. The method for producing D-lactide using D-lactic acid according to claim 1, wherein in step (2):
initial reaction: the mass ratio of the added cobalt oxide to the added di-cysteine methyl ester vanadyl is 1:1.5, and the addition amount of the cobalt oxide in the initial reaction is 1/2 of the total addition amount of the cobalt oxide; the reaction temperature is kept between 5 and 10 ℃ from the initial reaction to the time when one half of the reaction time is passed;
when the reaction time is one-half elapsed: adding all the residual di-cysteine methyl ester vanadyl into a reaction kettle; the reaction temperature is kept between 15 and 20 ℃ from one half of the reaction time to three quarters of the reaction time;
three quarters of the time elapsed: adding the rest cobalt oxide into the reaction kettle; the reaction temperature is kept between 25 and 30 ℃ from the end of the reaction to the end of the reaction after three quarters of the reaction time.
3. The method for producing D-lactide using D-lactic acid according to claim 2, wherein in the step (2), di-cysteine methyl ester vanadyl is prepared by: mixing and stirring cysteine methyl ester and vanadyl sulfate in boric acid solution at room temperature, and reacting for 3-5h to obtain purple solid; the amount ratio of the cysteine methyl ester to the vanadyl sulfate substance is 5:1, and the concentration of the cysteine methyl ester in the boric acid solution is 0.1-5 mol/L.
4. The method for producing D-lactide using D-lactic acid according to claim 3, wherein in the step (2), after the reaction is finished, the organic phase is separated by filtration and standing for layering, and the organic phase is washed with water; and (4) carrying out vacuum distillation on the organic phase after washing by water to remove the solvent, thus obtaining a white solid.
5. The method for producing D-lactide using D-lactic acid as claimed in claim 1, wherein in step (3), the D-lactic acid oligomer obtained in step (2) is charged into a lactide preparation vessel, and heated to 145-160 ℃ to melt the D-lactic acid oligomer; the catalyst used for synthesizing the D-lactide is a mixture of nickel oxide and molybdenum glycinate, the using amount of the nickel oxide is 0.01 to 0.03 percent of the mass of the D-lactic acid oligomer, the using amount of the molybdenum glycinate is 0.03 to 0.09 percent of the mass of the D-lactic acid oligomer, the reaction time is 3 to 5 hours, and the reaction pressure is 0.01 multiplied by 105Pa-0.1×105Pa；
Initial reaction: the mass ratio of the added nickel oxide to the added molybdenum glycinate is 1:2, and the addition amount of the nickel oxide during the initial reaction is 1/3 of the total addition amount of the nickel oxide;
when one third of the reaction time has elapsed: adding the rest nickel oxide into the lactide preparation kettle;
two thirds of the reaction time elapsed: the remaining molybdenum glycinate was added to the lactide preparation kettle in its entirety.
6. The method for producing D-lactide using D-lactic acid according to claim 5, wherein in the step (3), the molybdenum glycinate is prepared by: mixing and stirring sodium molybdate and glycine hydroxy acid in a methanol solution at room temperature, and reacting for 2-3h to obtain solid molybdenum glycine hydroxy acid; the weight ratio of glycine hydroxy acid to sodium molybdate is 4:1, and the concentration of sodium molybdate in the methanol solution is 0.1-2 mol/L.
7. The method for producing D-lactide from D-lactic acid according to claim 6, wherein in step (3), the upper part of the lactide preparation tank is in fluid communication with the condensation collection tank through a heat insulation pipe, and the produced D-lactide is cooled and crystallized in the condensation collection tank.
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| Title |
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| Oxygen versus nitrogen co-ordination in complexes of MoⅥ and hydroxamate derivatives of a-amino acids：equilibrium，structural and theoretical studies;Farkas E等;《J．Chem．Soc．》;19991231;第2789-2794页 * |
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