CN111978181B - High-yield preparation method of ethyl chrysanthemate - Google Patents
High-yield preparation method of ethyl chrysanthemate Download PDFInfo
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- CN111978181B CN111978181B CN202011023444.9A CN202011023444A CN111978181B CN 111978181 B CN111978181 B CN 111978181B CN 202011023444 A CN202011023444 A CN 202011023444A CN 111978181 B CN111978181 B CN 111978181B
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/30—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group
- C07C67/333—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group by isomerisation; by change of size of the carbon skeleton
- C07C67/343—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group by isomerisation; by change of size of the carbon skeleton by increase in the number of carbon atoms
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- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
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- C07C245/00—Compounds containing chains of at least two nitrogen atoms with at least one nitrogen-to-nitrogen multiple bond
- C07C245/20—Diazonium compounds
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- C07C67/48—Separation; Purification; Stabilisation; Use of additives
- C07C67/52—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
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- C07C67/48—Separation; Purification; Stabilisation; Use of additives
- C07C67/52—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation
- C07C67/54—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation by distillation
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Abstract
The invention belongs to the technical field of chemical processes, and particularly relates to a preparation method of ethyl chrysanthemate with high yield, which comprises the following steps: (1) diazotization: adding water, glycine ethyl ester hydrochloride, glacial acetic acid and dimethyl carbonate serving as solvents into a diazotization kettle, then dropwise adding a sodium nitrite aqueous solution into the diazotization kettle, and obtaining a diazotization solution after the reaction is finished; (2) cyclization: adding 2, 5-dimethyl-2, 4-hexadiene into a cyclization kettle, adopting cuprous chloride as a catalyst, and obtaining a cyclization solution after complete reaction; (3) desolventizing: sending the cyclized solution into a high-yield desolventizing tower to remove the solvent to obtain a crude product of ethyl chrysanthemate; (4) distillation: and putting the crude ethyl chrysanthemate into a distillation kettle for vacuum distillation to obtain the high-purity ethyl chrysanthemate. The invention has the beneficial effects that: when dimethyl carbonate is used as a solvent, diazotization reaction can be carried out more completely, the loss of raw materials is reduced, and the yield of ethyl chrysanthemate in subsequent cyclization reaction can be improved.
Description
Technical Field
The invention belongs to the technical field of chemical processes, and particularly relates to a preparation method of ethyl chrysanthemate with high yield.
Background
The ethyl chrysanthemate is also an important intermediate of pyrethroids like methyl chrysanthemate, and can be used for preparing various sanitary pyrethroids including permethrin, tetramethrin, phenothrin, propiolate and other insecticides. The reaction of ethyl diazoacetate and 2, 5-dimethyl-2, 4-hexadiene is one of the most important synthesis routes with the most industrial application value. Ethyl diazoacetate and 2, 5-dimethyl-2, 4-hexadiene are used as raw materials to prepare ethyl chrysanthemate, copper powder is usually used as a catalyst, and toluene or halogenated hydrocarbon is used as a solvent, but the problem of low chemical yield exists.
Disclosure of Invention
The invention aims to provide a method for preparing ethyl chrysanthemate with high yield, which has the effects of high reaction rate, high ethyl chrysanthemate yield and stable reaction process.
The technical purpose of the invention is realized by the following technical scheme: (1) diazotization: adding water, glycine ethyl ester salt and glacial acetic acid into a diazotization kettle, stirring to dissolve solids, then adding dimethyl carbonate serving as a solvent into the diazotization kettle, starting freezing to reduce the temperature of diazotization kettle materials to 20 to 25 ℃, then dropwise adding a sodium nitrite aqueous solution into the diazotization kettle, standing and layering after the reaction is finished, and discharging a lower water layer to a waste liquid collecting tank to obtain a diazotization liquid;
(2) Cyclization: adding 2, 5-dimethyl-2, 4-hexadiene into a cyclization kettle, using cuprous chloride as a catalyst, opening and stirring, heating to 90-95 ℃, then beginning to drip heavy nitrogen liquid, continuing to perform heat preservation reaction after dripping the heavy nitrogen liquid, and cooling to 45-60 ℃ after the reaction is completed by introducing water into the cyclization kettle to obtain a cyclization liquid;
(3) Desolventizing: after the cyclized liquid is sent into a high-yield desolventizing tower, a stirrer and a jacket steam feed pipe are started, the temperature is raised and the reflux is started, the dimethyl carbonate and the 2, 5-dimethyl-2, 4-hexadiene are removed, and a cyclized liquid solvent is removed to obtain a crude ethyl chrysanthemate;
(4) And (3) distillation: and putting the crude ethyl chrysanthemate into a distillation kettle for vacuum distillation to obtain high-purity ethyl chrysanthemate.
The invention is further configured as follows: in the step (1), glacial acetic acid is adopted to keep the pH value of the diazotization reaction between 3.5 and 4.5.
The invention is further configured as follows: the diazotization raw material in the step (1) comprises, by mass, 600 to 700 parts of water, 470 to 490 parts of glycine ethyl ester acid salt, 35 to 37 parts of glacial acetic acid, 260 to 265 parts of sodium nitrite and 800 parts of dimethyl carbonate solvent.
The invention is further provided with: in the step (1), the dropping time of the sodium nitrite is controlled to be 4 to 5 hours, and the temperature is kept for 30 to 60min after the dropping.
The invention is further provided with: the cyclized raw materials in the step (2) comprise, by mass, 1100 parts of the whole batch of the diazo liquid in the step (1), 2, 5-dimethyl-2, 4-hexadiene and 2-5 parts of cuprous chloride.
The invention is further configured as follows: and (3) dripping the diazo liquid in the step (2) for 10 to 12h at a speed of less than or equal to 100L/h, and keeping the temperature for 60 to 90min after the dripping of the diazo liquid is finished.
The invention is further provided with: the desolventizing step (3) comprises the following steps:
s1, opening a cyclized liquid feed valve and a vacuum pipe valve of a high-efficiency desolventizing tower, vacuumizing a certain amount of cyclized liquid into the high-efficiency desolventizing tower, opening a manual emptying pipe emptying valve to return the interior of the high-efficiency desolventizing tower to normal pressure, opening a stirrer of the high-efficiency desolventizing tower, a jacketed steam feed pipe and a condensed water discharge pipe, and starting to heat and reflux;
s2, after refluxing for 20 to 40min, opening a dimethyl carbonate receiving tank, a dimethyl carbonate feeding valve and a vacuum valve at the upper part of the dimethyl carbonate receiving tank for vacuum distillation, observing temperature trend balance, adjusting a reflux ratio, keeping the temperature at the top of the tower below 90 ℃, and continuously evaporating dimethyl carbonate;
s3, when the dimethyl carbonate is recovered to 75 to 85 percent, closing a toluene feed valve of a dimethyl carbonate receiving tank and a vacuum valve at the upper part of the toluene feed valve, stopping receiving the dimethyl carbonate, opening a 2, 5-dimethyl-2, 4-hexadiene receiving tank 2, 5-dimethyl-2, 4-hexadiene feed valve, and beginning to remove the 2, 5-dimethyl-2, 4-hexadiene;
s4, the first stage is a previous stage of removing 2, 5-dimethyl-2, 4-hexadiene, the stage is atmospheric distillation, and the overhead temperature of the stage is 60-135 ℃; the second stage is a stage of removing 2, 5-dimethyl-2, 4-hexadiene, the stage is atmospheric distillation, and the overhead temperature of the stage is 135-138 ℃; the third stage is a stage of vacuum removal of 2, 5-dimethyl-2, 4-hexadiene, wherein the pressure in the tower is more than or equal to 0.07Mpa at 115-120 ℃;
and after S5 and 2, 5-dimethyl-2, 4-hexadiene are removed, closing a steam feed valve, a condensate water discharge valve and a vacuum valve of a 2, 5-dimethyl-2, 4-hexadiene receiving tank of the high-efficiency desolventizing tower, opening circulating water in a jacket of the high-efficiency desolventizing tower to start cooling, and opening a discharge valve at the lower part of the high-efficiency desolventizing tower to start barreling and weighing after the temperature of materials in the high-efficiency desolventizing tower is reduced to 50-70 ℃ to obtain crude ethyl chrysanthemate.
The invention is further provided with: and (3) dripping the diazo liquid in the step (2) for 10 to 12h at a speed of less than or equal to 100L/h, and keeping the temperature for 60 to 90min after the dripping of the diazo liquid is finished.
The invention is further provided with: and the 2, 5-dimethyl-2, 4-hexadiene removed in the step S4 is recycled as a raw material for cyclization.
The invention is further provided with: the step (4) of distillation comprises the following steps:
s1, opening a crude ethyl chrysanthemate feed valve and a vacuum pipe valve of a distillation kettle, sucking crude ethyl chrysanthemate in the distillation kettle in vacuum, closing the crude ethyl chrysanthemate feed valve and the vacuum pipe valve, and opening a manual emptying pipe emptying valve to return the distillation kettle to normal pressure;
s2, opening a gas-phase feed valve, a liquid-phase discharge valve, a circulating water inlet/outlet valve, a front distillate receiving tank feed valve and an upper vacuum valve of the front distillate receiving tank feed valve of the distillation still condenser, and opening a high vacuum system when the pressure in the distillation still reaches a vacuum degree of more than or equal to 0.08 MPa;
s3, controlling the vacuum degree to be stable, starting a stirrer of the distillation kettle, opening a steam feed valve and a condensate water discharge valve of a jacket of the distillation kettle, and starting heating to distill front distillate, wherein the distillation temperature is 103 to 107 ℃;
s4, when the temperature in the distillation kettle rises obviously, ending the front distillate distillation process, closing a feed valve of a front distillate receiving tank and an upper vacuum valve thereof, opening a feed valve of a main distillate receiving tank and an upper vacuum valve thereof, and opening a steam feed valve of a large distillation kettle jacket to ensure that the temperature in the distillation kettle reaches 110 to 115 ℃, and beginning to distill out main distillate;
s5, when the temperature in the distillation kettle is obviously reduced, the distillation process of the main fraction is finished
The invention is further provided with: and a DCS (distributed control System) interlocking control system is adopted to control the preparation process of the ethyl chrysanthemate.
The invention has the beneficial effects that:
1. dimethyl carbonate is an organic solvent with low toxicity and excellent environmental protection performance, can replace solvents with higher toxicity such as halogenated hydrocarbon, methylbenzene and the like, and reduces the accidents such as poisoning and the like caused by misoperation of operators. .
2. Dimethyl carbonate has good dispersion and stabilization effects on diazoacetic ether which is a heavy nitridation reaction product, and in a dimethyl carbonate solvent, the diazoacetic ether can be kept stable at a higher temperature and is not easy to decompose, so that the stability of a diazo reaction can be greatly improved.
3. When dimethyl carbonate is used as a solvent, the diazotization reaction temperature can reach 20-25 ℃, so that the diazotization reaction can be carried out more completely, the loss of raw materials is reduced, the content of ethyl diazoacetate in diazotization liquid is improved, the yield of ethyl chrysanthemate in subsequent cyclization reaction can be improved, and the content of ethyl chrysanthemate in cyclization liquid can reach more than 15%.
4. Cuprous chloride can be used as a catalyst for cyclization reaction, has better catalytic effect compared with copper powder, can obviously improve the cyclization reaction rate, and can improve the yield of the ethyl chrysanthemate, the yield of the ethyl chrysanthemate is only 60-70% under the condition that the copper powder is used as the catalyst, and the yield of the ethyl chrysanthemate can reach more than 85% by using the cuprous chloride as the catalyst; the cuprous chloride has a good inhibition effect on polymerization of hexadiene in a dimethyl carbonate environment, the cuprous chloride can play a role in inhibiting polymerization through charge transfer, methoxy groups in the dimethyl carbonate can act with free radicals in the hexadiene to form non-free-radical substances, chain polymerization of the free radicals can be effectively inhibited, the 2, 5-dimethyl-2, 4-hexadiene can be prevented from generating polymerization reaction in the cyclization reaction process, the utilization rate of the 2, 5-dimethyl-2, 4-hexadiene can be improved, the amount of high-temperature polymers in a distillation kettle is reduced, and coking at the bottom of the distillation kettle can be avoided.
5. The boiling point of the dimethyl carbonate is lower, the difference between the boiling point of the dimethyl carbonate and the boiling point of the 2, 5-dimethyl-2, 4-hexadiene is larger, the dimethyl carbonate is used as a solvent, the dimethyl carbonate is favorably separated from the 2, 5-dimethyl-2, 4-hexadiene, the recovery purity of the solvent and the 2, 5-dimethyl-2, 4-hexadiene is higher, and the utilization rate of raw materials can be improved.
The removal of the 2, 5-dimethyl-2, 4-hexadiene is divided into three stages, the 2, 5-dimethyl-2, 4-hexadiene can be separated from a cyclizing solution to the maximum extent to obtain the 2, 5-dimethyl-2, 4-hexadiene with higher purity, the recovery rate of the 2, 5-dimethyl-2, 4-hexadiene is improved, meanwhile, the content of the 2, 5-dimethyl-2, 4-hexadiene in the ethyl chrysanthemate can be reduced, and the subsequent purification of crude ethyl chrysanthemate is facilitated.
7. The removed 2, 5-dimethyl-2, 4-hexadiene can be recycled to a cyclization reaction kettle, the purity of the 2, 5-dimethyl-2, 4-hexadiene has great influence on the yield of the ethyl chrysanthemate, the 2, 5-dimethyl-2, 4-hexadiene subjected to three-stage desolventizing has low impurity content and high quality, can be directly recycled, and can greatly improve the yield of the ethyl chrysanthemate compared with the conventional desolventizing.
Detailed Description
The technical solutions in the examples will be clearly and completely described below. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without inventive step, shall fall within the scope of protection of the present invention.
Example 1
A preparation method of ethyl chrysanthemate with high yield comprises the following steps:
(1) Diazotization: putting 600 parts of water, 490 parts of glycine ethyl ester salt and 35 parts of glacial acetic acid into a diazotization kettle, stirring to dissolve a solid, keeping the pH value of diazotization reaction between 3.5 and 4.5 by adopting glacial acetic acid, putting 800 parts of dimethyl carbonate as a solvent into the diazotization kettle, freezing, cooling the material in the diazotization kettle to 20 to 25 ℃, dropwise adding a sodium nitrite aqueous solution into the diazotization kettle, controlling the dropwise adding time of the sodium nitrite to be 4 to 5 hours, keeping the temperature for 60min after dropwise adding is finished, standing and layering after the reaction is finished, and discharging a lower water layer to a waste liquid collecting tank to obtain a diazotization liquid;
(2) Cyclization: putting 1100 parts of 2, 5-dimethyl-2, 4-hexadiene into a cyclization kettle, taking 2 parts of cuprous chloride as a catalyst, stirring while opening, heating to 90 to 95 ℃, then starting to dropwise add the whole batch of the diazo liquid in the step (1), wherein the dropwise adding time of the diazo liquid is 10 to 12h, the dropwise adding speed is less than or equal to 100L/h, continuing to keep the temperature for 90min after dropwise adding the diazo liquid, and cooling the water in the cyclization kettle to 45 to 60 ℃ after complete reaction to obtain a cyclization liquid;
(3) Desolventizing: s1, opening a cyclized liquid feed valve and a vacuum pipe valve of a high-efficiency desolventizing tower, vacuumizing a certain amount of cyclized liquid into the high-efficiency desolventizing tower, opening a manual emptying pipe emptying valve to return the interior of the high-efficiency desolventizing tower to normal pressure, opening a stirrer of the high-efficiency desolventizing tower, a jacketed steam feed pipe and a condensed water discharge pipe, and starting to heat and reflux;
s2, after refluxing for 20min, opening a dimethyl carbonate receiving tank, a dimethyl carbonate feeding valve and a vacuum valve at the upper part of the dimethyl carbonate receiving tank for vacuum distillation, observing the temperature trend balance, adjusting the reflux ratio, keeping the temperature at the top of the tower below 90 ℃, and continuously steaming out dimethyl carbonate;
s3, when the dimethyl carbonate is recovered to 80%, closing a toluene feeding valve of a dimethyl carbonate receiving tank and an upper vacuum valve thereof, stopping receiving the dimethyl carbonate, opening a 2, 5-dimethyl-2, 4-hexadiene receiving tank 2, 5-dimethyl-2, 4-hexadiene feeding valve, and beginning to remove the 2, 5-dimethyl-2, 4-hexadiene;
s4, the first stage is a previous stage of removing 2, 5-dimethyl-2, 4-hexadiene, the stage is atmospheric distillation, and the overhead temperature of the stage is 60-135 ℃; the second stage is a stage for removing 2, 5-dimethyl-2, 4-hexadiene, the stage is atmospheric distillation, and the overhead temperature of the stage is 135-138 ℃; the third stage is a stage of removing the 2, 5-dimethyl-2, 4-hexadiene in vacuum, wherein the pressure in the tower is more than or equal to 0.07Mpa at the temperature of 115-120 ℃; s5, after the removal of 2, 5-dimethyl-2, 4-hexadiene is finished, closing a steam feed valve, a condensate water discharge valve and a vacuum valve of a 2, 5-dimethyl-2, 4-hexadiene receiving tank of the high-efficiency desolventizing tower, opening circulating water in a jacket of the high-efficiency desolventizing tower, starting cooling, and after the temperature of materials in the high-efficiency desolventizing tower is reduced to 50-70 ℃, opening a discharge valve at the lower part of the high-efficiency desolventizing tower, starting barreling and weighing to obtain crude ethyl chrysanthemate;
(4) And (3) distillation: s1, opening a crude ethyl chrysanthemate feeding valve and a vacuum pipe valve of a distillation kettle, pumping the crude ethyl chrysanthemate into the distillation kettle in a vacuum manner, closing the crude ethyl chrysanthemate feeding valve and the vacuum pipe valve, and opening a manual emptying pipe emptying valve to return the distillation kettle to normal pressure;
s2, opening a gas-phase feed valve, a liquid-phase discharge valve, a circulating water inlet/outlet valve, a front distillate receiving tank feed valve and an upper vacuum valve of the front distillate receiving tank feed valve of the distillation still condenser, and opening a high vacuum system when the pressure in the distillation still reaches a vacuum degree of more than or equal to 0.08 MPa;
s3, controlling the vacuum degree to be stable, starting a stirrer of the distillation kettle, opening a steam feed valve and a condensate water discharge valve of a jacket of the distillation kettle, and starting heating to distill front distillate, wherein the distillation temperature is about 105 ℃;
s4, when the temperature in the distillation kettle rises obviously, ending the front distillate distillation process, closing a feed valve of a front distillate receiving tank and an upper vacuum valve thereof, opening a feed valve of a main distillate receiving tank and an upper vacuum valve thereof, and opening a steam feed valve of a large distillation kettle jacket to ensure that the temperature in the distillation kettle reaches about 113 ℃, and beginning to distill out main distillate;
s5, when the temperature in the distillation kettle is obviously reduced, the distillation process of the main fraction is finished;
and a DCS (distributed control System) interlocking control system is adopted to control the preparation process of the ethyl chrysanthemate.
Example 2
Example 2 differs from example 1 in that:
(1) Diazotization: putting 500 parts of water, 480 parts of glycine ethyl ester salt and 36 parts of glacial acetic acid into a diazotization kettle, stirring to dissolve a solid, keeping the pH value of diazotization reaction between 3.5 and 4.5 by adopting glacial acetic acid, putting 800 parts of dimethyl carbonate as a solvent into the diazotization kettle, freezing, cooling the material in the diazotization kettle to 20 to 25 ℃, dropwise adding a sodium nitrite aqueous solution into the diazotization kettle, controlling the dropwise adding time of the sodium nitrite to be 4 to 5 hours, keeping the temperature for 45min after dropwise adding is finished, standing and layering after the reaction is finished, and discharging a lower water layer to a waste liquid collecting tank to obtain a diazotization liquid;
(2) Cyclization: putting 1100 parts of 2, 5-dimethyl-2, 4-hexadiene into a cyclization kettle, taking 3.5 parts of cuprous chloride as a catalyst, opening and stirring, heating to 90-95 ℃, then starting to dropwise add the whole batch of diazo liquid in the step (1), wherein the dropwise adding time of the diazo liquid is 10-12h, the dropwise adding speed is less than or equal to 100L/h, continuing to keep the temperature for 70min after dropwise adding the diazo liquid, and cooling the cyclization kettle to 45-60 ℃ after complete reaction to obtain the cyclization liquid.
Example 3
Example 3 differs from example 1 in that:
(1) Diazotization: putting 700 parts of water, 470 parts of glycine ethyl ester salt and 37 parts of glacial acetic acid into a diazotization kettle, stirring to dissolve a solid, keeping the pH value of diazotization reaction between 3.5 and 4.5 by adopting glacial acetic acid, putting 800 parts of dimethyl carbonate as a solvent into the diazotization kettle, freezing, cooling the material in the diazotization kettle to 20 to 25 ℃, dropwise adding a sodium nitrite aqueous solution into the diazotization kettle, controlling the dropwise adding time of the sodium nitrite to be 4 to 5 hours, keeping the temperature for 60min after dropwise adding is finished, standing and layering after the reaction is finished, and discharging a lower water layer to a waste liquid collecting tank to obtain a diazotization liquid;
(2) Cyclization: putting 1100 parts of 2, 5-dimethyl-2, 4-hexadiene into a cyclization kettle, taking 2 to 5 parts of cuprous chloride as a catalyst, opening and stirring, heating to 90 to 95 ℃, then starting to dropwise add the whole batch of diazo liquid in the step (1), wherein the dropwise adding time of the diazo liquid is 10 to 12h, the dropwise adding speed is less than or equal to 100L/h, continuing to keep the temperature for 60min after dropwise adding the diazo liquid, and cooling the cyclization kettle to 45 to 60 ℃ after complete reaction to obtain the cyclization liquid.
Example 4
Example 4 differs from example 2 in that dichloroethane is used as solvent in the diazotization step (1).
Example 5
Example 5 differs from example 2 in that copper powder is used as a catalyst in the cyclization in step (2).
Example 6
Example 6 differs from example 2 in that in the step (3) of desolventizing, 2, 5-dimethyl-2, 4-hexadiene was removed by atmospheric distillation at an overhead temperature of 135-138 ℃.
Procedure of the test
Ethyl chrysanthemate is prepared by the scheme of the embodiment 1-6, 2, 5-dimethyl-2, 4-hexadiene obtained in the diazo liquid, the cyclized liquid, the high-efficiency desolventizing tower and the finished ethyl chrysanthemate in each embodiment are taken to prepare samples, and the content of ethyl chrysanthemate in the cyclized liquid, the purity of the 2, 5-dimethyl-2, 4-hexadiene obtained by desolventizing, the residue in a distillation kettle and the yield of the finished ethyl chrysanthemate are measured according to standard methods.
(1) And (3) measuring the content of ethyl chrysanthemate: and (4) measuring by gas chromatography.
(2) 2, 5-dimethyl-2, 4-hexadiene content determination:
quantitative analysis by gas chromatography
Reagent: methylene chloride, meta-xylene (internal standard), 2, 5-dimethyl-2, 4-hexadiene samples
The instrument comprises the following steps: SC-6 gas chromatograph, hydrogen flame ionization detector and column head sample injection.
The method comprises the following steps: accurately weighing 5 2, 5-dimethyl-2, 4-hexadiene standard samples and internal standard substances in different weight ratios, adding a proper amount of solvent for dissolving, fully shaking up, and then carrying out sample injection on a chromatograph one by one to obtain a standard curve; accurately weighing a 2, 5-dimethyl-2, 4-hexadiene sample and an internal standard substance, adding a proper amount of solvent, fully shaking up, then injecting the sample on a chromatograph, and calculating the obtained data with a human standard curve to obtain the content of the 2, 5-dimethyl-2, 4-hexadiene sample in the 2, 5-dimethyl-2, 4-hexadiene sample.
(3) Yield of finished product ethyl chrysanthemate:
yield = (amount of raw material to form target product/amount of raw material fed) × 100%
The yield of the ethyl chrysanthemate is calculated according to 2, 5-dimethyl-2, 4-hexadiene.
Test results
The test results for examples 1-6 are shown in table 1 below:
TABLE 1 Ethyl chrysanthemate preparation test results
| Ethyl chrysanthemate content (%) | 2, 5-dimethyl-2, 4-hexadiene purity (%) | Amount of residue (kg) | Yield (%) | |
| Example 1 | 19.5 | 99.2 | 18 | 87 |
| Example 2 | 21.6 | 99.5 | 12 | 92 |
| Example 3 | 18.9 | 99.3 | 23 | 85 |
| Example 4 | 15.3 | 98.6 | 44 | 76 |
| Example 5 | 13.2 | 99.1 | 65 | 72 |
| Example 6 | 19.4 | 95.2 | 31 | 78 |
It can be seen from table 1 that the use of dimethyl carbonate as solvent and cuprous chloride as catalyst can greatly increase the content of ethyl chrysanthemate and the yield of ethyl chrysanthemate (in terms of hexadiene) in the cyclized solution, reduce the amount of residue in the distillation still, and obtain high-purity 2, 5-dimethyl-2, 4-hexadiene by three-stage rectification and desolventization, thereby further increasing the yield of ethyl chrysanthemate.
Claims (9)
1. The preparation method of the ethyl chrysanthemate with high yield is characterized by comprising the following steps:
(1) Diazotization: adding water, glycine ethyl acetate and glacial acetic acid into a diazotization kettle, stirring to dissolve the solid, then adding dimethyl carbonate as a solvent into the diazotization kettle,
freezing, cooling the diazotization kettle material to 20-25 ℃, then dropwise adding a sodium nitrite aqueous solution into the diazotization kettle, standing and layering after the reaction is finished, and discharging a lower water layer to a waste liquid collecting tank to obtain a diazotization liquid;
(2) Cyclization: adding 2, 5-dimethyl-2, 4-hexadiene into a cyclization kettle, using cuprous chloride as a catalyst, opening and stirring, heating to 90-95 ℃, then beginning to drip heavy nitrogen liquid, continuing to perform heat preservation reaction after dripping the heavy nitrogen liquid, and cooling to 45-60 ℃ after the reaction is completed by introducing water into the cyclization kettle to obtain a cyclization liquid;
(3) Desolventizing: after the cyclized liquid is sent into a high-yield desolventizing tower, a stirrer and a jacket steam feed pipe are started, the temperature is raised and the reflux is started, the dimethyl carbonate and the 2, 5-dimethyl-2, 4-hexadiene are removed, and a cyclized liquid solvent is removed to obtain a crude ethyl chrysanthemate;
the desolventizing step (3) comprises the following steps:
s1, opening a cyclized liquid feed valve and a vacuum pipe valve of a high-efficiency desolventizing tower, vacuumizing a certain amount of cyclized liquid into the high-efficiency desolventizing tower, opening a manual emptying pipe emptying valve to return the interior of the high-efficiency desolventizing tower to normal pressure, opening a stirrer of the high-efficiency desolventizing tower, a jacketed steam feed pipe and a condensed water discharge pipe, and starting to heat and reflux;
s2, after refluxing for 20 to 40min, opening a dimethyl carbonate receiving tank, a dimethyl carbonate feeding valve and a vacuum valve on the upper part of the dimethyl carbonate receiving tank for vacuum distillation, observing temperature trend balance, adjusting a reflux ratio, keeping the temperature of the top of the tower below 90 ℃, and continuously evaporating dimethyl carbonate;
s3, when the dimethyl carbonate is recovered to 75 to 85 percent, closing a toluene feed valve of a dimethyl carbonate receiving tank and a vacuum valve at the upper part of the toluene feed valve, stopping receiving the dimethyl carbonate, opening a 2, 5-dimethyl-2, 4-hexadiene receiving tank 2, 5-dimethyl-2, 4-hexadiene feed valve, and beginning to remove the 2, 5-dimethyl-2, 4-hexadiene;
s4, the first stage is a previous stage of removing 2, 5-dimethyl-2, 4-hexadiene, the stage is atmospheric distillation, and the overhead temperature of the stage is 60-135 ℃; the second stage is a stage for removing 2, 5-dimethyl-2, 4-hexadiene, the stage is atmospheric distillation, and the overhead temperature of the stage is 135-138 ℃; the third stage is a stage of vacuum removal of 2, 5-dimethyl-2, 4-hexadiene, wherein the pressure in the tower is more than or equal to 0.07Mpa at 115-120 ℃;
s5, after the removal of 2, 5-dimethyl-2, 4-hexadiene is finished, closing a steam feed valve, a condensate water discharge valve and a vacuum valve of a 2, 5-dimethyl-2, 4-hexadiene receiving tank of the high-efficiency desolventizing tower, opening circulating water in a jacket of the high-efficiency desolventizing tower, starting cooling, and after the temperature of materials in the high-efficiency desolventizing tower is reduced to 50-70 ℃, opening a discharge valve at the lower part of the high-efficiency desolventizing tower, starting barreling and weighing to obtain crude ethyl chrysanthemate;
(4) And (3) distillation: and putting the crude ethyl chrysanthemate into a distillation kettle for vacuum distillation to obtain high-purity ethyl chrysanthemate.
2. The method for preparing ethyl chrysanthemate with high yield according to claim 1, wherein the method comprises the following steps: in the step (1), glacial acetic acid is adopted to keep the pH value of the diazotization reaction between 3.5 and 4.5.
3. The method for preparing ethyl chrysanthemate with high yield according to claim 1, wherein the method comprises the following steps: the diazotization raw material in the step (1) comprises, by mass, 600 to 700 parts of water, 470 to 490 parts of glycine ethyl ester salt, 35 to 37 parts of glacial acetic acid, 260 to 265 parts of sodium nitrite and 800 parts of dimethyl carbonate solvent.
4. The method for preparing ethyl chrysanthemate with high yield according to claim 1, wherein the method comprises the following steps: in the step (1), the dropping time of the sodium nitrite is controlled to be 4 to 5 hours, and the temperature is kept for 30 to 60min after the dropping is finished.
5. The method for preparing ethyl chrysanthemate with high yield according to claim 1, wherein the method comprises the following steps: the cyclized raw materials in the step (2) comprise, by mass, 1100 parts of the whole batch of the diazo liquid in the step (1), 2, 5-dimethyl-2, 4-hexadiene and 2-5 parts of cuprous chloride.
6. The method for preparing ethyl chrysanthemate with high yield according to claim 1, wherein the method comprises the following steps: in the step (2), the dripping time of the diazo liquid is 10 to 12h, the dripping speed is less than or equal to 100L/h, and the temperature is kept for 60 to 90min after the diazo liquid is dripped.
7. The method for preparing ethyl chrysanthemate with high yield according to claim 1, wherein the method comprises the following steps: and the 2, 5-dimethyl-2, 4-hexadiene removed in the step S4 is recycled as a raw material for cyclization.
8. The method for preparing ethyl chrysanthemate with high yield according to claim 1, wherein the method comprises the following steps: the step (4) of distillation comprises the following steps:
s1, opening a crude ethyl chrysanthemate feed valve and a vacuum pipe valve of a distillation kettle, sucking crude ethyl chrysanthemate in the distillation kettle in vacuum, closing the crude ethyl chrysanthemate feed valve and the vacuum pipe valve, and opening a manual emptying pipe emptying valve to return the distillation kettle to normal pressure;
s2, opening a gas-phase feed valve, a liquid-phase discharge valve, a circulating water inlet/outlet valve, a front distillate receiving tank feed valve and an upper vacuum valve of the front distillate receiving tank feed valve of the distillation still condenser, and opening a high vacuum system when the pressure in the distillation still reaches a vacuum degree of more than or equal to 0.08 MPa;
s3, controlling the vacuum degree to be stable, starting a stirrer of the distillation kettle, opening a steam feed valve and a condensate water discharge valve of a jacket of the distillation kettle, and starting heating to distill front distillate, wherein the distillation temperature is 103 to 107 ℃;
s4, when the temperature in the distillation kettle rises obviously, ending the front distillate distillation process, closing a feed valve of a front distillate receiving tank and an upper vacuum valve thereof, opening a feed valve of a main distillate receiving tank and an upper vacuum valve thereof, and opening a steam feed valve of a large distillation kettle jacket to ensure that the temperature in the distillation kettle reaches 110 to 115 ℃, and beginning to distill out main distillate;
and S5, when the temperature in the distillation kettle is obviously reduced, ending the distillation process of the main fraction.
9. The method for preparing ethyl chrysanthemate with high yield according to claim 1, wherein the method comprises the following steps: and a DCS (distributed control System) interlocking control system is adopted to control the preparation process of the ethyl chrysanthemate.
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