CN110845313A - Continuous preparation method of 3, 4-dihydroxy-2, 5-hexanedione - Google Patents
Continuous preparation method of 3, 4-dihydroxy-2, 5-hexanedione Download PDFInfo
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- CN110845313A CN110845313A CN201910931661.9A CN201910931661A CN110845313A CN 110845313 A CN110845313 A CN 110845313A CN 201910931661 A CN201910931661 A CN 201910931661A CN 110845313 A CN110845313 A CN 110845313A
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- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/61—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by reactions not involving the formation of >C = O groups
- C07C45/67—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by reactions not involving the formation of >C = O groups by isomerisation; by change of size of the carbon skeleton
- C07C45/68—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by reactions not involving the formation of >C = O groups by isomerisation; by change of size of the carbon skeleton by increase in the number of carbon atoms
- C07C45/72—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by reactions not involving the formation of >C = O groups by isomerisation; by change of size of the carbon skeleton by increase in the number of carbon atoms by reaction of compounds containing >C = O groups with the same or other compounds containing >C = O groups
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Abstract
The invention discloses a continuous preparation method of 3, 4-dihydroxy-2, 5-hexanedione, which comprises the following steps: conveying the reaction raw materials into at least one fixed bed reactor filled with zinc powder and provided with a jacket through a metering pump for reaction, then enabling the reaction liquid flowing out of the fixed bed reactor to enter a reaction liquid storage tank, and then entering the subsequent extraction process. The invention establishes a process method for continuously preparing 3, 4-dihydroxy-2, 5-hexanedione, can be used for replacing the original batch reactor reaction process, has the advantages of high efficiency, stability, controllability and the like compared with the batch reaction technology, further utilizes the multi-fixed bed series technology to effectively improve the preparation efficiency of the 3, 4-dihydroxy-2, 5-hexanedione, has better controllability, safety and reaction conversion rate, effectively inhibits the occurrence of side reaction and reduces the generation amount of three wastes.
Description
Technical Field
The invention belongs to the technical field of organic synthesis, and particularly relates to a continuous preparation method of 3, 4-dihydroxy-2, 5-hexanedione.
Background
In recent years, compared with the traditional kettle type reaction technology, the continuous reaction technology has stronger mass transfer and heat transfer performance and simpler monitoring performance of the reaction process, so that the continuous reaction technology has wide application in the field of organic synthesis. The novel technology can also combine multi-step operation into a simple linear process, so that the time from research to production and application can be greatly shortened. In 2016, the first report of a Pinacol coupling reaction using continuous flow reaction technology was published by the Christophe Len group. With this as a guide, researchers developed a method for continuously preparing 3, 4-dihydroxy-2, 5-hexanedione by using fixed bed reaction equipment and methylglyoxal as a raw material to perform a Pinacol coupling reaction.
Preparation of 3, 4-dihydroxy-2, 5-hexanedione from 4-hydroxy-2, 5-dimethyl-3 (2H) -furanone (perfumery furanone)
) An intermediate of (1). In the prior art, the synthesis method of 3, 4-dihydroxy-2, 5-hexanedione comprises the following steps: (1) taking methylglyoxal as a raw material, and preparing 3, 4-dihydroxy-2, 5-hexanedione by utilizing self Pinacol coupling reaction; (2) taking methylglyoxal and hydroxyacetone as raw materials, and preparing 3, 4-dihydroxy-2, 5-hexanedione by utilizing a cross Aldol coupling reaction; (3) 2, 5-dimethylfuran is used as a raw material, and oxidation reaction participated by osmium tetroxide is utilized to prepare 3, 4-dihydroxy-2, 5-hexanedione; (4) tartaric acid is used as a raw material, and 3, 4-dihydroxy-2, 5-hexanedione and the like are prepared through multi-step reaction. Wherein the synthetic route of taking the methylglyoxal as the raw material and utilizing the self Pinacol coupling reaction is as followsThe main methods for industrially producing 3, 4-dihydroxy-2, 5-hexanedione are now available. So far, the mode of preparing 3, 4-dihydroxy-2, 5-hexanedione by taking methylglyoxal as a raw material is mainly a batch kettle reaction, and no report exists for preparing the compound by using a continuous flow reaction technology.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a continuous preparation method of 3, 4-dihydroxy-2, 5-hexanedione.
The technical scheme of the invention is as follows:
a continuous process for the preparation of 3, 4-dihydroxy-2, 5-hexanedione comprising: conveying the reaction raw materials into at least one fixed bed reactor filled with zinc powder and provided with a jacket through a metering pump for reaction, then conveying the reaction liquid flowing out of the fixed bed reactor into a reaction liquid storage tank, and then conveying the reaction liquid into the subsequent extraction process; the reaction raw materials are a 20-50 wt% methylglyoxal aqueous solution and acetic acid, and the molar ratio of the methylglyoxal to the acetic acid is 1: 1-10;
wherein, the residence time of the reaction raw materials in the fixed bed reactor is 1-60min through flow rate control, the reaction temperature in the fixed bed reactor is kept at 0-50 ℃ by introducing a refrigerant into a jacket, and the content of each component in the reaction liquid flowing out of the fixed bed reactor is detected through gas phase and gas phase connection and liquid phase or liquid phase connection.
In a preferred embodiment of the invention, the flow rates of the methylglyoxal aqueous solution and the acetic acid are both 1-10mL/min, and the methylglyoxal aqueous solution and the acetic acid are mixed by a static mixer and then enter the fixed bed reactor for reaction.
In a preferred embodiment of the present invention, the aqueous methylglyoxal solution and acetic acid are mixed and then fed into the fixed bed reactor at a flow rate of 1-10mL/min for reaction.
In a preferred embodiment of the present invention, the number of the fixed bed reactors is at least three, wherein at least two fixed bed reactors are connected in series for reaction, and the rest is reserved for standby, and the specific reaction process is as follows: when the residual quantity of the methylglyoxal in the reaction solution is higher than a set value, isolating the fixed bed reactor positioned at the most upstream of the at least two fixed bed reactors, connecting one of the fixed bed reactors as a spare fixed bed reactor in series with the downstream of the fixed bed reactor positioned at the most downstream of the at least two fixed bed reactors, and replacing the zinc powder in the fixed bed reactor positioned at the most upstream of the at least two fixed bed reactors as a spare fixed bed reactor; when the participation amount of the methylglyoxal in the reaction liquid is higher than the set value again, the reaction process is repeated circularly.
Further preferably, the fixed bed reactors include first to third fixed bed reactors, and the specific reaction process is as follows:
a. the reaction raw materials firstly pass through a first fixed bed reactor, then continuously enter a second fixed bed reactor, and then enter a reaction liquid storage tank;
b. when the first time of the residual quantity of the methylglyoxal in the reaction liquid is higher than a set value, the methylglyoxal is connected in series into a third fixed bed reactor, the first fixed bed reactor is isolated, the reaction is continued, and the zinc powder in the first fixed bed reactor is supplemented;
c. when the residual methylglyoxal in the reaction liquid is higher than the set value for the second time, serially connecting the reaction liquid into the first fixed bed reactor, isolating the second fixed bed reactor, continuing the reaction, and supplementing the zinc powder in the second fixed bed reactor;
d. when the third time of the residual methylglyoxal in the reaction liquid is higher than the set value, the residual methylglyoxal is connected in series into the second fixed bed reactor, the third fixed bed reactor is isolated, the reaction is continued, and the zinc powder in the third fixed bed reactor is supplemented;
repeating the steps a to d to realize continuous reaction.
The invention has the beneficial effects that: the invention establishes a process method for continuously preparing 3, 4-dihydroxy-2, 5-hexanedione, can be used for replacing the original batch reactor reaction process, has the advantages of high efficiency, stability, controllability and the like compared with the batch reaction technology, further utilizes the multi-fixed bed series technology to effectively improve the preparation efficiency of the 3, 4-dihydroxy-2, 5-hexanedione, has better controllability, safety and reaction conversion rate, effectively inhibits the occurrence of side reaction and reduces the generation amount of three wastes.
Drawings
FIG. 1 is a schematic process flow diagram of example 1 of the present invention.
FIG. 2 is a schematic process flow diagram of example 2 of the present invention.
FIG. 3 is a schematic process flow diagram of example 3 of the present invention.
Detailed Description
The technical solution of the present invention will be further illustrated and described below with reference to the accompanying drawings by means of specific embodiments.
The equation for the self Pinacol coupling reaction of methylglyoxal is shown below, with the major by-product being the partially reduced product hydroxyacetone (compound 3).
Example 1
The process flow is shown in figure 1, acetone aldehyde aqueous solution (located in a raw material storage tank V001) with the concentration of 30 wt% and acetic acid (located in a raw material storage tank V002) are respectively conveyed into a static mixer M001 through a raw material conveying pump P001 and an acetic acid conveying pump V002 at certain flow rate (flow rate range of 1mL/min to 10mL/min) and proportion, mixing the aqueous solution of methylglyoxal with acetic acid, feeding the mixture into a fixed bed reactor R001 filled with zinc powder from the bottom, the temperature of the fixed bed reactor R001 is controlled between 0 and 50 ℃ (a cooling medium is introduced into a jacket), the residence time of the reaction liquid in the fixed bed reactor is controlled between 1 and 60min by adjusting the flow rate, then, the reaction solution flowing out of the fixed bed reactor R001 is introduced into a reaction solution storage tank V003, the contents of the respective components in the reaction liquid flowing out from the fixed bed reactor R001 were detected by gas phase.
In the above process, the molar ratio of methylglyoxal to acetic acid is 1: 2, controlling the flow rate to enable the reaction liquid to stay in the fixed bed reactor for 20min, wherein the conversion rate of the methylglyoxal is 96%; the selectivity of the reaction was 87%; the yield of 3, 4-dihydroxy-2, 5-hexanedione (compound 2) was about 84%.
Example 2
The process flow is shown in fig. 2, firstly, mixing 30 wt% aqueous solution of methylglyoxal with acetic acid in a raw material mixing kettle M001 according to a certain proportion, then conveying the mixed raw material to a fixed bed reactor R001 filled with zinc powder through a raw material conveying pump P001 at a certain flow rate (the flow rate range is 1mL/min to 10mL/min), controlling the temperature of the fixed bed reactor R001 between 0 ℃ and 50 ℃ (a cooling medium is introduced into a jacket), controlling the residence time of reaction liquid in the fixed bed reactor R001 between 1 min and 60min by adjusting the flow rate, then making the reaction liquid flowing out of the fixed bed reactor R001 enter a reaction liquid storage tank V003, and detecting the content of each component in the reaction liquid flowing out of the fixed bed reactor R001 through a gas phase. In the above process, the molar ratio of methylglyoxal to acetic acid is 1: 2, the flow rate was controlled so that the reaction solution remained in the fixed bed reactor for 20min, and substantially the same experimental results as in example 1 were obtained.
Example 3
The zinc powder in the fixed bed reactor is consumed along with the reaction along with the change of time, and when the zinc powder in the fixed bed reactor is less than a certain amount, the conversion rate and the yield of the reaction are both reduced. In order to ensure the continuity of the reaction and the substantial invariance of the conversion and yield of the reaction, attempts have therefore been made to solve this problem by using a series of multiple fixed bed reactors.
The process flow is shown in figure 3, firstly, mixing 30 wt% concentration methylglyoxal water solution and acetic acid in a raw material mixing kettle M001 according to a certain proportion, then conveying the mixed raw material to a fixed bed reactor filled with zinc powder through a raw material conveying pump P001 at a certain flow rate, controlling the temperature of the fixed bed reactor between 0 ℃ and 50 ℃ (introducing a refrigerant into a jacket), controlling the residence time of reaction liquid in the fixed bed reactor between 1 min and 60min by adjusting the flow rate, then making the reaction liquid flowing out of the fixed bed reactor R001 enter a reaction liquid storage tank V003, and detecting the content of each component in the reaction liquid flowing out of the fixed bed reactor through gas phase.
Firstly, the zinc powder passes through a fixed bed reactor R001, then continuously enters a fixed bed reactor R002, then enters a reaction liquid storage tank V003, is connected in series into the fixed bed reactor R003 when the residual quantity of the methylglyoxal in the reaction liquid is higher than 2 percent, isolates the fixed bed reactor R001, continuously reacts, and supplements the zinc powder in the fixed bed reactor R001. And when the residual amount of the methylglyoxal in the reaction liquid is higher than 2 percent again, connecting the reaction liquid in the fixed bed reactor R001 in series again, isolating the fixed bed reactor R002, continuing the reaction, and supplementing the zinc powder in the fixed bed reactor R002. When the third time of the residual amount of the methylglyoxal in the reaction solution is higher than 2%, the methylglyoxal is connected in series into the fixed bed reactor R002, the fixed bed reactor R003 is isolated, the reaction is continued, and the zinc powder in the fixed bed reactor R003 is supplemented in such a circulating operation, so that the problems of reaction conversion rate and yield reduction caused by the consumption of the zinc powder in the fixed bed can be solved.
In the above process, the molar ratio of methylglyoxal to acetic acid is 1: 2, the flow rate was controlled so that the reaction solution remained in the fixed bed reactor for 20min, and substantially the same experimental results as in example 1 were obtained.
The above description is only a preferred embodiment of the present invention, and therefore should not be taken as limiting the scope of the invention, which is defined by the appended claims.
Claims (5)
1. A continuous preparation method of 3, 4-dihydroxy-2, 5-hexanedione is characterized by comprising the following steps: the method comprises the following steps: conveying the reaction raw materials into at least one fixed bed reactor filled with zinc powder and provided with a jacket through a metering pump for reaction, then conveying the reaction liquid flowing out of the fixed bed reactor into a reaction liquid storage tank, and then conveying the reaction liquid into the subsequent extraction process; the reaction raw materials are 20-50 wt% of methylglyoxal aqueous solution and acetic acid, and the molar ratio of the methylglyoxal to the acetic acid is 1: 1-10;
wherein, the residence time of the reaction raw materials in the fixed bed reactor is 1-60min through flow rate control, the reaction temperature in the fixed bed reactor is kept at 0-50 ℃ by introducing a refrigerant into a jacket, and the content of each component in the reaction liquid flowing out of the fixed bed reactor is detected through gas phase and gas phase connection and liquid phase or liquid phase connection.
2. The continuous process for preparing 3, 4-dihydroxy-2, 5-hexanedione as described in claim 1, wherein: the flow rates of the methylglyoxal aqueous solution and the acetic acid are both 1-10mL/min, and the methylglyoxal aqueous solution and the acetic acid are mixed by a static mixer and then enter the fixed bed reactor for reaction.
3. The continuous process for preparing 3, 4-dihydroxy-2, 5-hexanedione as described in claim 1, wherein: mixing the methylglyoxal aqueous solution and acetic acid, and then feeding the mixture into the fixed bed reactor at a flow rate of 1-10mL/min for reaction.
4. A process for the continuous preparation of 3, 4-dihydroxy-2, 5-hexanedione according to any one of claims 1 to 3, wherein: the number of the fixed bed reactors is at least three, wherein at least two fixed bed reactors are connected in series for reaction, the rest is used for standby, and the specific reaction process is as follows: when the residual quantity of the methylglyoxal in the reaction solution is higher than a set value, isolating the fixed bed reactor positioned at the most upstream of the at least two fixed bed reactors, connecting one of the fixed bed reactors as a spare fixed bed reactor in series with the downstream of the fixed bed reactor positioned at the most downstream of the at least two fixed bed reactors, and replacing the zinc powder in the fixed bed reactor positioned at the most upstream of the at least two fixed bed reactors as a spare fixed bed reactor; when the participation amount of the methylglyoxal in the reaction liquid is higher than the set value again, the reaction process is repeated circularly.
5. A process for the continuous preparation of 3, 4-dihydroxy-2, 5-hexanedione as described in claim 4 wherein: the fixed bed reactor comprises a first fixed bed reactor, a second fixed bed reactor, a third fixed bed reactor and a fourth fixed bed reactor, wherein the specific reaction process is as follows:
a. the reaction raw materials firstly pass through a first fixed bed reactor, then continuously enter a second fixed bed reactor, and then enter a reaction liquid storage tank;
b. when the first time of the residual quantity of the methylglyoxal in the reaction liquid is higher than a set value, the methylglyoxal is connected in series into a third fixed bed reactor, the first fixed bed reactor is isolated, the reaction is continued, and the zinc powder in the first fixed bed reactor is supplemented;
c. when the residual methylglyoxal in the reaction liquid is higher than the set value for the second time, serially connecting the reaction liquid into the first fixed bed reactor, isolating the second fixed bed reactor, continuing the reaction, and supplementing the zinc powder in the second fixed bed reactor;
d. when the third time of the residual methylglyoxal in the reaction liquid is higher than the set value, the residual methylglyoxal is connected in series into the second fixed bed reactor, the third fixed bed reactor is isolated, the reaction is continued, and the zinc powder in the third fixed bed reactor is supplemented;
repeating the steps a to d to realize continuous reaction.
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Inventor after: Xu Wenfeng Inventor after: Yang Jingxiang Inventor after: Zhang Jianglong Inventor after: Chen Yujun Inventor after: Li Xinhao Inventor after: Zeng Renxiang Inventor before: Yang Jingxiang Inventor before: Xu Wenfeng Inventor before: Chen Yujun Inventor before: Li Xinhao Inventor before: Zeng Renxiang |
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Application publication date: 20200228 |