CN114539025A - Method for separating dihydric alcohol through ester exchange reaction - Google Patents
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- CN114539025A CN114539025A CN202210236913.8A CN202210236913A CN114539025A CN 114539025 A CN114539025 A CN 114539025A CN 202210236913 A CN202210236913 A CN 202210236913A CN 114539025 A CN114539025 A CN 114539025A
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/128—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by alcoholysis
- C07C29/1285—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by alcoholysis of esters of organic acids
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Abstract
The invention relates to a method for separating diols by transesterification, comprising the following steps: reaction (I): mixing the dihydric alcohol mixture with ester and a catalyst to perform ester exchange reaction; cooling to minus 10-minus 30 ℃, or filtering the catalyst or adjusting the pH value of the reaction system to 6-9, and terminating the reaction; (II) product separation: the unreacted diol is separated from the reaction product. The method can fully convert certain dihydric alcohol through ester exchange reaction, and the other dihydric alcohol has low conversion rate or basically does not convert, and the dihydric alcohol with higher purity can be obtained after the product is separated. The separation technology has the advantages of mild conditions, energy conservation, low fixed investment and operation cost, less side reaction, higher separation efficiency and the like.
Description
Technical Field
The invention relates to a method for separating dihydric alcohol through ester exchange reaction, belonging to the technical field of chemical separation.
Background
The dihydric alcohol is an important chemical raw material and has wide application in the aspects of plastics, foods, daily chemical industry, medicine synthesis and the like. For example, ethylene glycol is a platform compound mainly used for synthesizing PET polyester, which is used for producing packaging materials, textile fibers, films, etc., and thus the industrial demand for ethylene glycol is large. With the increasing depletion of petroleum resources and the increase of accumulated discharge of carbon dioxide, a technology for synthesizing glycols such as ethylene glycol from coal and biomass will gradually become a mainstream technology. However, since the selectivity of the reaction is not high, the product is often present as a mixture of glycols, and the purity is not sufficient for downstream production. In addition, the boiling point of the dihydric alcohol is high and close, oligomerization is easy to occur at high temperature, if the dihydric alcohol mixture is separated by rectification, the energy consumption is high, and the purity of the product is difficult to reach a high level. The melting point of the glycol is low and the operating conditions will be very severe if isolated by crystallization. The polarity of the diols is close, and if separation is performed by extraction, the separation efficiency is generally not high. Therefore, there is an urgent need to develop a technology for separating a glycol mixture with high efficiency, low cost and low energy consumption.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: a process for separating diols by transesterification is provided, which can convert some diols sufficiently while other diols have a low or substantially no conversion by transesterification, and which can obtain diols having a high purity after separation of the product.
The technical scheme for solving the technical problems is as follows: a method for separating glycols by transesterification comprising the steps of:
reaction (I): mixing the dihydric alcohol mixture with ester and a catalyst to perform ester exchange reaction; cooling to minus 10-minus 30 ℃, or filtering the catalyst or adjusting the pH value of the reaction system to 6-9, and stopping the reaction;
(II) product separation: the unreacted diol is separated from the reaction product.
In the step (one), the ester comprises one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, dimethyl carbonate and diethyl carbonate, and the mass ratio of the ester to the dihydric alcohol is 0.01-2; the catalyst comprises one or more of sulfuric acid, hydrochloric acid, nitric acid, acidic resin, acidic molecular sieve, alkaline resin, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate and cesium carbonate, and the mass ratio of the catalyst to the dihydric alcohol is 0.002-0.2; the reaction temperature is 10-120 ℃, and the reaction time is 10 minutes-6 hours;
the method adopted in the separation in the step (II) is as follows: one or more of distillation, extraction, melt crystallization and centrifugal separation.
Further, in the step (one), the reaction temperature is 40-70 ℃, and the reaction time is 2-6 hours.
The mass ratio of the ester to the impurity dihydric alcohol is 0.5-5.
The mass ratio of the catalyst to the impurity dihydric alcohol is 0.05-5.
In the step (II), the separation method comprises the steps of firstly removing ester and reaction products of methanol or ethanol by a distillation method, freezing the residual liquid in an environment of minus 15-minus 5 ℃ for 0.1-1 hour to separate out solid carbonate, filtering or centrifuging to remove the solid carbonate at the temperature of minus 15-minus 5 ℃, and taking out the liquid to obtain the dihydric alcohol product with improved purity.
In the step (II), the separation method comprises the steps of firstly removing the ester and the reaction product methanol or ethanol by a distillation method, adding an extracting agent into the residual liquid, extracting and separating the ester to further remove the ester, and taking out the raffinate phase to obtain the dihydric alcohol product with improved purity.
The extracting agent is alkane, arene, ester or ketone, and the mass ratio of the extracting agent to the dihydric alcohol is 0.05-1.
The dihydric alcohol mixture in the step (I) contains two or more of ethylene glycol, propylene glycol, butanediol, pentanediol and hexanediol.
The principle of the invention for separating the dihydric alcohol mixture is as follows: the dihydric alcohol with high carbon number has stronger ester exchange reaction activity, can be fully converted into esters under the action of an acid-base catalyst, has low conversion rate or basically does not convert, has low boiling point or low polarity or high melting point of ester products, is easy to separate the ester products from the mixture by the technologies of distillation, extraction, melt crystallization and the like, and finally obtains the dihydric alcohol product with high purity and low carbon number.
Compared with the prior art, the invention has the advantages that: the reaction condition is mild, the energy is saved, the fixed investment and the operation cost are low, the side reaction is less, and the separation efficiency is higher; can produce high value-added products such as ethylene carbonate, propylene carbonate, butylene carbonate and the like as byproducts.
The technical features of one of the methods for separating diols by transesterification according to the present invention will be further described with reference to examples.
Detailed Description
The required equipment includes: a reaction kettle, a heater, a stirring device, a separating device and the like.
Example one
Putting 8 g of ethylene glycol and 2 g of 1, 2-propylene glycol into a reaction kettle, adding 2 g of dimethyl carbonate, setting the heating temperature to be 50 ℃, and stirring the mixture at the rotating speed of 300 rpm; 0.1 g of concentrated sulfuric acid was added thereto, and the reaction was carried out for 0.5 hour. The reaction was terminated by adding 10% NaOH solution to adjust the pH of the mixture to 7. And removing the mixture, removing the dimethyl carbonate and the reaction product methanol by rotary evaporation, freezing the residual liquid in an environment at the temperature of minus 10 ℃ for half an hour to separate out the carbonate, centrifuging the mixture at the temperature of minus 10 ℃ at the rotating speed of 5000rpm for 10 minutes, taking out the liquid, weighing the liquid, and analyzing the liquid by gas chromatography to obtain the product with the mass concentration of the glycol of 94.6 percent and the yield of the glycol of 87.6 percent.
Example two
Putting 8 g of ethylene glycol and 2 g of 1, 2-butanediol into a reaction kettle, adding 2 g of ethyl acetate, setting the heating temperature to be 60 ℃, and stirring the mixture at the rotating speed of 300 rpm; 0.1 g of cesium carbonate was added and reacted for 2 hours. The temperature is reduced to minus 10 ℃ to terminate the reaction. And removing the mixture, removing ethyl acetate and reaction product ethanol by rotary evaporation, mixing the residual liquid with 5 ml of n-hexane, stirring for 10 minutes, extracting and separating esters, taking out a raffinate phase, weighing, and analyzing by gas chromatography to obtain a product containing 92.3% of glycol by mass and 93.5% of glycol yield.
EXAMPLE III
Putting 9 g of 1, 2-propylene glycol and 1 g of 1, 2-pentanediol into a reaction kettle, adding 1 g of diethyl carbonate, setting the heating temperature to be 120 ℃, and stirring the mixture at the rotating speed of 300 rpm; 0.1 g of sodium hydroxide and 0.1 g of potassium hydroxide were added to the reaction solution, and the reaction was carried out for 3 hours. 10% sulfuric acid was added to adjust the pH of the mixture to 7, and the reaction was terminated. And removing the mixture, removing diethyl carbonate and reaction product ethanol by rotary evaporation, freezing the residual liquid in an environment at the temperature of minus 10 ℃ for half an hour to separate out the carbonate, centrifuging at the temperature of minus 10 ℃ at the rotating speed of 5000rpm for 10 minutes, taking out the liquid, weighing, and analyzing by using gas chromatography to obtain the product containing 98.3% of 1, 2-propylene glycol by mass and 88.7% of 1, 2-propylene glycol by yield.
Example four
Putting 8 g of 1, 2-butanediol and 2 g of 1, 2-hexanediol into a reaction kettle, adding 2 g of methyl formate, reacting at 10 ℃, and stirring the mixture at the rotating speed of 300 rpm; 0.2 g of potassium carbonate was added thereto, and the reaction was carried out for 4 hours. 10% sulfuric acid was added to adjust the pH of the mixture to 7, and the reaction was terminated. Removing the mixture, removing methyl formate and a reaction product methanol by rotary evaporation, mixing the residual liquid with 6 ml of cyclohexane, stirring for 10 minutes, extracting and separating esters, taking out a raffinate phase, weighing, and analyzing by gas chromatography to obtain a product containing 94.6% of 1, 2-butanediol by mass concentration and 94.1% of 1, 2-butanediol by yield.
EXAMPLE five
Putting 9 g of ethylene glycol and 1 g of 2, 3-butanediol into a reaction kettle, adding 1.5 g of dimethyl carbonate, setting the heating temperature to be 50 ℃, and stirring the mixture at the rotating speed of 400 rpm; 0.2 g of concentrated hydrochloric acid and 0.2 g of concentrated nitric acid were added to the reaction solution, and the reaction was carried out for 6 hours. The reaction was terminated by adding 10% NaOH solution to adjust the pH of the mixture to 7. Removing the mixture, removing dimethyl carbonate and a reaction product methanol by rotary evaporation, freezing the residual liquid in an environment with the temperature of minus 10 ℃ for 1 hour to separate out the carbonate, centrifuging the mixture at the temperature of minus 10 ℃, rotating the speed of 6000rpm for 5 minutes, taking out the liquid, weighing the liquid, and analyzing the liquid by gas chromatography to obtain the product with the mass concentration of the glycol of 97.8 percent and the yield of the glycol of 83 percent.
EXAMPLE six
Putting 8 g of 1, 2-propylene glycol and 2 g of 1, 2-hexanediol into a reaction kettle, adding 2 g of ethyl formate, setting the heating temperature to be 50 ℃, and stirring the mixture at the rotating speed of 300 rpm; 0.3 g of sodium carbonate was added and reacted for 10 minutes. The reaction was terminated by adding 3% sulfuric acid and adjusting the pH of the mixture to 7. Removing the mixture, removing ethyl formate and reaction product ethanol by rotary evaporation, mixing the residual liquid with 6 ml of n-octane, stirring for 5 minutes, extracting and separating esters, taking out an extraction raffinate, weighing, and analyzing by gas chromatography to obtain a product containing 90.2% of 1, 2-propylene glycol by mass and 96.8% of 1, 2-propylene glycol by yield.
EXAMPLE seven
Putting 8 g of 1, 2-propylene glycol and 2 g of 1, 2-butanediol into a reaction kettle, adding 2 g of methyl acetate, setting the heating temperature to be 50 ℃, and stirring the mixture at the rotating speed of 300 rpm; 0.2 g of lithium carbonate was added and reacted for 6 hours. The reaction was terminated by adding 3% sulfuric acid and adjusting the pH of the mixture to 7. Removing the mixture, removing methyl acetate and a reaction product methanol by rotary evaporation, mixing the residual liquid with 4 ml of n-octane, stirring for 5 minutes, extracting and separating esters, taking out a raffinate phase, weighing, and analyzing by gas chromatography to obtain a product containing 96.2% of 1, 2-propanediol by mass and 94.1% of 1, 2-propanediol by yield.
Example eight
Putting 7 g of ethylene glycol, 1 g of 1, 2-butanediol, 1 g of 1, 2-pentanediol and 1 g of 1, 2-hexanediol into a reaction kettle, adding 2 g of diethyl carbonate, setting the heating temperature to be 60 ℃, and stirring the mixture at the rotating speed of 300 rpm; 0.3 g of hydrogen type ZSM-5 acidic molecular sieve is added for reaction for 4 hours. The acidic molecular sieve is filtered to terminate the reaction. Removing the mixture, removing methyl acetate and reaction product ethanol by rotary evaporation, mixing the residual liquid with 5 ml of methyl laurate, stirring for 5 minutes, extracting and separating esters, taking out a raffinate phase, weighing, and analyzing by gas chromatography, wherein the product contains 92.1% of glycol by mass and the yield of the glycol is 92.7%.
Example nine
Putting 6 g of ethylene glycol, 1 g of 1, 2-propylene glycol, 1 g of 1, 2-butanediol, 1 g of 1, 2-pentanediol and 1 g of 1, 2-hexanediol into a reaction kettle, adding 2 g of dimethyl carbonate, setting the heating temperature to be 50 ℃, and stirring the mixture at the rotating speed of 300 rpm; 0.2 g of gel type styrene strongly basic resin is added and reacted for 4 hours. The basic resin was filtered to terminate the reaction. Removing the mixture, removing methyl acetate and a reaction product methanol by rotary evaporation, mixing the residual liquid with 5 ml of toluene, stirring for 5 minutes, extracting and separating esters, taking out a raffinate phase, weighing, and analyzing by gas chromatography to obtain a product containing 93.8% of glycol by mass and 90.7% of glycol yield.
Claims (9)
1. A method for separating glycols by transesterification, characterized in that: the method comprises the following steps:
reaction (I): mixing the dihydric alcohol mixture with ester and a catalyst to perform ester exchange reaction; cooling to minus 10-minus 30 ℃, or filtering the catalyst or adjusting the pH value of the reaction system to 6-9, and stopping the reaction;
(II) product separation: the unreacted diol is separated from the reaction product.
2. A method of separating glycols by transesterification according to claim 1, wherein:
in the step (one), the ester comprises one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, dimethyl carbonate and diethyl carbonate, and the mass ratio of the ester to the dihydric alcohol is 0.01-2; the catalyst comprises one or more of sulfuric acid, hydrochloric acid, nitric acid, acidic resin, acidic molecular sieve, alkaline resin, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate and cesium carbonate, and the mass ratio of the catalyst to the dihydric alcohol is 0.002-0.2; the reaction temperature is 10-120 ℃, and the reaction time is 10 minutes-6 hours;
the method adopted in the separation in the step (II) is as follows: one or more of distillation, extraction, melt crystallization and centrifugal separation.
3. A method of separating glycols by transesterification according to claim 2, wherein: in the step (one), the reaction temperature is 40-70 ℃, and the reaction time is 2-6 hours.
4. A method of separating glycols by transesterification according to claim 2, wherein: the mass ratio of the ester to the impurity dihydric alcohol is 0.5-5.
5. A method of separating glycols by transesterification according to claim 2, wherein: the mass ratio of the catalyst to the impurity dihydric alcohol is 0.05-5.
6. A method of separating glycols by transesterification according to claim 2, wherein: in the step (II), the separation method comprises the steps of firstly removing ester and a reaction product methanol or ethanol by a distillation method, freezing the residual liquid in an environment of subzero 15-subzero 5 ℃ for 0.1-1 hour to separate out solid carbonate, filtering or centrifuging to remove the solid carbonate under the condition of subzero 15-subzero 5 ℃, and taking out the liquid to obtain the dihydric alcohol product with improved purity.
7. A method of separating glycols by transesterification according to claim 2, wherein: in the step (II), the separation method comprises the steps of firstly removing the ester and the reaction product methanol or ethanol by a distillation method, adding an extracting agent into the residual liquid, extracting and separating the ester to further remove the ester, and taking out the raffinate phase to obtain the dihydric alcohol product with improved purity.
8. The method of claim 7, wherein the diol is isolated by transesterification, and wherein: the extracting agent is alkane, arene, ester or ketone, and the mass ratio of the extracting agent to the dihydric alcohol is 0.05-1.
9. A method for separating glycols by transesterification according to any of claims 1 to 8, wherein: the dihydric alcohol mixture in the step (I) contains two or more of ethylene glycol, propylene glycol, butanediol, pentanediol and hexanediol.
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