A process for the preparation of sorbate esters

Abstract

In order to overcome the problems of organic waste liquid, alkaline waste water and low sorbate yield in the separation of sorbic acid and catalyst after the sorbate esterification reaction in the prior art, the application provides a preparation method of sorbate, after the reaction of reactants sorbic acid, alcohol and ionic liquid catalyst, the alcohol is separated by distillation, then the liquid is cooled, the catalyst and sorbic acid are crystallized and separated, the upper liquid is collected by reduced pressure distillation to obtain sorbate; the crystallized sorbic acid and ionic liquid catalyst can continue to carry out esterification reaction. The preparation method of the application can recycle the sorbic acid and ionic liquid catalyst, improve the utilization rate, and at the same time, the waste of neutralization by lye is not needed, so that the generation of alkaline waste water is reduced; the sorbate is separated by reduced pressure distillation, so that the organic solvent extraction is not needed, and the generation of organic waste liquid is avoided.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sorbic acid product preparation, and particularly relates to a preparation method of sorbic acid ester. BACKGROUND

[0002] Sorbic acid ester is a derivative of sorbic acid and has good antibacterial activity, and can be used as a food additive. At present, it is mainly prepared by acid catalysis direct esterification. Since the reaction of sorbic acid is not complete, the unreacted sorbic acid and the catalyst need to be separated and removed by organic solvent extraction and alkali neutralization, so as to achieve the purpose of separation and purification. This method loses a large amount of sorbic acid, has low sorbic acid ester yield, and produces a large amount of alkaline wastewater and organic waste liquid.

[0003] The research on ionic liquid catalyst as a green catalyst in esterification is a hot topic at present. The ionic liquid catalyst is applied to the esterification reaction of sorbic acid and alcohol as a catalyst. Since the reaction of sorbic acid is not complete, waste liquid is generated in the separation of sorbic acid and ionic liquid catalyst. At present, there is no research on recycling of sorbic acid and ionic liquid catalyst and improving the yield of sorbic acid ester.

[0004] In view of the above technical problems, the present application efficiently prepares sorbic acid ester by a method of continuous esterification reaction combined with reduced pressure distillation, has high yield, and almost does not produce wastewater, and meets the concept of green chemistry. SUMMARY

[0005] In view of the problems of separation of sorbic acid and catalyst after esterification reaction to generate organic waste liquid and alkaline wastewater and low yield of sorbic acid ester in the prior art, the present application provides a preparation method of sorbic acid ester.

[0006] The present application provides a preparation method of sorbic acid ester, and the technical scheme is as follows:

[0007] The preparation method of sorbic acid ester comprises the following steps:

[0008] A: the reactants sorbic acid, alcohol, and ionic liquid catalyst are added into a reaction container, and are stirred at normal temperature first. After the reactants are completely dissolved, the reaction is carried out by heating;

[0009] B: the liquid after the reaction of step A is distilled to recover the fraction of unreacted alcohol;

[0010] C: the remaining liquid after distillation in step B is cooled to make the sorbic acid and ionic liquid catalyst crystallize and separate, and the obtained liquid is subjected to reduced pressure distillation to collect the fraction of sorbic acid ester product;

[0011] D: the crystallized sorbic acid and ionic liquid catalyst in step C are recycled to step A to further react with the newly added alcohol, sorbic acid, and ionic liquid catalyst.

[0012] Preferably, the cooling temperature of the remaining liquid in step C is 6°C to 14°C.

[0013] Preferably, the cooling temperature of the remaining liquid in step C is 8°C-10°C.

[0014] Preferably, the mass ratio of sorbic acid, alcohol, and ionic liquid catalyst in step A is 1:(1-5):(0.01-0.05).

[0015] Preferably, the mass ratio of sorbic acid, alcohol, and ionic liquid catalyst in step A is 1:(2-5):(0.01-0.03).

[0016] Preferably, the reaction temperature in step A is 50℃~100℃, and the reaction time is 4h~12h.

[0017] Preferably, the reaction temperature in step A is 60℃~80℃, and the reaction time is 6h~10h.

[0018] Preferably, in step C, the distillation is carried out under reduced pressure, with a distillation pressure of -0.08 MPa to -0.1 MPa and a distillation temperature of 40°C to 80°C.

[0019] Preferably, the ionic liquid catalyst comprises at least one of the following: propyltriethylsulfonate p-toluenesulfonate ([NEt3PS]pSTA), propyltriethylsulfonate ammonium hydrogen sulfate ([NEt3PS]HSO4), propyltriethylsulfonate ammonium methanesulfonate ([NEt3PS]MSA), propyltriethylsulfonate-3-methylimidazolium hydrogen sulfate ([MIMPS]HSO4), propyltriethylsulfonate-3-methylimidazolium p-toluenesulfonate ([MIMPS]pSTA), propyltriethylsulfonate-3-methylimidazolium methanesulfonate ([MIMPS]MSA), propyltriethylsulfonate-pyridine hydrogen sulfate (PyPS]HSO4), propyltriethylsulfonate-pyridine p-toluenesulfonate ([PyPS]pTSA), and propyltriethylsulfonate-pyridine methanesulfonate ([PyPS]MSA).

[0020] Preferably, the alcohol is a saturated aliphatic hydrocarbon alcohol with 1 to 4 carbon atoms.

[0021] The beneficial effects of this invention are:

[0022] 1. Unreacted sorbic acid crystals are left at the bottom of the container and do not need to be wasted by neutralizing them with alkali. Sorbic acid can be reused, greatly improving the utilization rate of sorbic acid and reducing production costs. At the same time, it reduces the generation of alkaline wastewater, which is in line with the national energy conservation and emission reduction policy.

[0023] 2. Sorbic acid esters are separated by vacuum distillation, which eliminates the need for organic solvent extraction. This method of product collection is simple, increases yield, saves costs, and avoids the generation of organic waste liquid.

[0024] 3. The ionic liquid catalyst crystallizes through liquid cooling and remains at the bottom of the container, reducing the separation steps between the ionic liquid catalyst and sorbate and saving process time; the ionic liquid catalyst can be reused, enabling continuous production and improving production efficiency. Detailed Implementation

[0025] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] On one hand, the present invention provides a method for preparing sorbate, comprising the following steps:

[0027] A: Add sorbic acid, alcohol, and ionic liquid catalyst to the reaction vessel, stir at room temperature first, and heat to carry out the reaction after the reactants have completely dissolved;

[0028] B: Distill the liquid after the reaction in step A to recover the unreacted alcohol fraction;

[0029] C: Cool the remaining liquid after distillation in step B to allow sorbic acid and ionic liquid catalyst to crystallize out, and then separate the crystals; perform vacuum distillation on the obtained liquid to collect the fraction of sorbic acid ester product;

[0030] D: The sorbic acid and ionic liquid catalyst crystallized in step C are recycled to step A and reacted further with the newly added alcohol, sorbic acid and ionic liquid catalyst.

[0031] Alcohols are separated by distillation, dried, and recycled, improving alcohol utilization. Sorbic acid and ionic liquid catalysts are cooled and crystallized, remaining at the bottom of the container. Unreacted sorbic acid crystals remain at the bottom of the container, eliminating the need for further neutralization with alkali and preventing waste. This allows for the reuse of sorbic acid, significantly increasing its utilization rate and reducing production costs. Simultaneously, it reduces the generation of alkaline wastewater, complying with national energy conservation and emission reduction policies. The ionic liquid catalyst is crystallized by cooling and remaining at the bottom of the container, reducing the separation steps between the ionic liquid catalyst and sorbate esters, saving process time. The ionic liquid catalyst can be reused, enabling continuous production and improving efficiency. Sorbic acid esters are separated by vacuum distillation, eliminating the need for organic solvent extraction. This simple method of product collection saves costs and avoids the generation of organic waste liquid. The purity of the sorbate ester product obtained by vacuum distillation can reach over 98.5%, improving the purity of the final sorbate ester product.

[0032] In some embodiments, the container in step A of the sorbate preparation method is a reaction container with a reflux condenser, which facilitates the cooling operation of the liquid in the container when a cooling fluid is introduced into the reflux condenser.

[0033] In some embodiments, the remaining liquid in step C of the sorbate preparation method is cooled to a temperature of 6-14°C.

[0034] The remaining liquid is cooled, and the sorbic acid and ionic liquid catalyst are crystallized, thereby achieving separation from the sorbate. This separation method is simple and does not produce alkaline waste liquid or organic waste liquid, is green production, and conforms to the national energy-saving and emission-reduction policy. The cooling temperature range is based on the temperature range obtained from the phase equilibrium relationship between sorbic acid, ionic liquid catalyst, and sorbate. If the temperature is lower than the temperature range, the effective crystallization ratio of sorbic acid and ionic liquid catalyst decreases. If the temperature is higher than the temperature range, the crystallization of sorbate products increases, which increases the separation cost of sorbate.

[0035] In some preferred embodiments, the remaining liquid in step C of the sorbate preparation method is cooled to a temperature of 8-10°C.

[0036] The preferred temperature for liquid cooling and crystallization is 8-10°C, at which the crystallization ratio of sorbic acid and ionic liquid catalyst is relatively high.

[0037] In some embodiments, the mass ratio of sorbic acid, alcohol, and ionic liquid catalyst in step A of the sorbate preparation method is 1:(1-5):(0.01-0.05).

[0038] In the esterification reaction, in order to make the sorbic acid react as completely as possible, the alcohol content is generally higher than the sorbic acid content. In some embodiments, the alcohol content is 1-5 times the sorbic acid content. A high alcohol content in the reactants allows the alcohol to react with sorbic acid as completely as possible to form sorbate. The ionic liquid catalyst only serves to catalyze the reaction between sorbic acid and alcohol, and accelerate the reaction rate. In the present application, the content of ionic liquid catalyst is 1%-5% of the sorbic acid content. The ionic liquid catalyst is high in cost, but it can be recycled in the preparation method of the present application. Only 1%-5% of the ionic liquid catalyst based on the sorbic acid content can achieve good catalytic effect, and at the same time, it can be recycled to reduce costs.

[0039] In some preferred embodiments, the mass ratio of sorbic acid, alcohol, and ionic liquid catalyst in step A of the sorbate preparation method is 1:(2-5):(0.01-0.03).

[0040] In some embodiments, the reaction temperature in step A of the sorbate preparation method is 50°C-100°C, and the reaction time is 4h-12h.

[0041] In some preferred embodiments, the reaction temperature in step A of the preparation method of sorbate is 60-80℃, and the reaction time is 6-10h.

[0042] The reaction of sorbic acid and alcohol requires heating. The container can be heated in a heating device such as an oil bath pot, or the container can be directly heated. Different heating methods can be selected according to the actual situation. Heating promotes the esterification reaction of sorbic acid and alcohol, and improves the production efficiency. The preferred reaction temperature and reaction time promote the reaction of sorbic acid and alcohol, increase the reaction rate, and increase the yield of sorbate product.

[0043] In some preferred embodiments, the distillation pressure in step C of the preparation method of sorbate is -0.08Mpa to -0.1Mpa, and the distillation temperature is 40-80℃.

[0044] In step C, the upper liquid is subjected to vacuum distillation, and sorbate is precipitated to obtain sorbate product. The pressure and temperature of vacuum distillation are selected according to the preferred range of the amount of sorbate precipitated at different pressures and temperatures. In this temperature and pressure range, the amount of precipitated sorbate is relatively large, the yield of sorbate is relatively high, the purity of sorbate product reaches 98.5% or more, and the production efficiency is effectively improved.

[0045] In some preferred embodiments, the ionic liquid catalyst includes at least one of triethylsulfonic acid propyl-p-toluenesulfonate ([NEt3PS]pSTA), triethylsulfonic acid propyl bisulfate ([NEt3PS]HSO4), triethylsulfonic acid propyl methanesulfonate ammonium ([NEt3PS]MSA), 1-propylsulfonic acid-3-methyl imidazole bisulfate ([MIMPS]HSO4), 1-propylsulfonic acid-3-methyl imidazole p-toluenesulfonate ([MIMPS]pSTA), 1-propylsulfonic acid-3-methyl imidazole methanesulfonate ([MIMPS]MSA), N-propylsulfonic acid pyridine bisulfate ([PyPS]HSO4), N-propylsulfonic acid pyridine p-toluenesulfonate ([PyPS]pTSA), N-propylsulfonic acid pyridine methanesulfonate ([PyPS]MSA).

[0046] In some preferred embodiments, the alcohol is a saturated aliphatic alcohol with 1-4 carbon atoms. Specifically, the saturated aliphatic alcohol with 1-4 carbon atoms includes methanol, ethanol, propanol, butanol, 1,2-ethylene glycol, propylene glycol, 1,3-butylene glycol, glycerol, butanetriol, etc.

[0047] The application is further described by the following examples.

[0048] Example 1

[0049] Into a 1000ml three-necked flask equipped with a condenser, 112g of sorbic acid was put into 460g of methanol, 2g of triethylsulfonium propylsulfate ammonium hydrogen sulfate catalyst was added, and the solution was stirred magnetically and dissolved, and the reaction was carried out under reflux for 12 hours in an oil bath at a heating temperature of 75°C. The methanol was distilled off and collected, and the collected methanol was dried for recycling. After the methanol was removed, condensing water was added to the condenser of the three-necked flask, and the remaining liquid in the flask was cooled to 8°C, and the sorbic acid and triethylsulfonium propylsulfate ammonium hydrogen sulfate catalyst were crystallized and precipitated, and then the upper liquid was poured into a single-necked flask and distilled under reduced pressure to collect 90.7g of methyl sorbate product; the pressure in the reduced pressure distillation was -0.1 MPa, and the distillation temperature was 55°C. The remaining three-necked flask crystalline material.

[0050] Into the three-necked flask, 112g of sorbic acid and 460g of methanol were further added, and the above steps were repeated to collect 110.3g of methyl sorbate product.

[0051] The yield of the sorbate was calculated to be 79.76%.

[0052] The yield of the sorbate was calculated to be 79.76%.

[0053] Example 2

[0054] Into a 1000ml three-necked flask equipped with a condenser, 112g of sorbic acid was put into 460g of methanol, 2g of triethylsulfonium propylsulfate ammonium hydrogen sulfate catalyst was added, and the solution was stirred magnetically and dissolved, and the reaction was carried out under reflux for 12 hours in an oil bath at a heating temperature of 75°C. The methanol was distilled off and collected, and the collected methanol was dried for recycling. After the methanol was removed, condensing water was added to the condenser of the three-necked flask, and the remaining liquid in the flask was cooled to 8°C, and the sorbic acid and triethylsulfonium propylsulfate ammonium hydrogen sulfate catalyst were crystallized and precipitated, and then the upper liquid was poured into a single-necked flask and distilled under reduced pressure to collect 90.7g of methyl sorbate product; the pressure in the reduced pressure distillation was -0.1 MPa, and the distillation temperature was 55°C. The remaining three-necked flask crystalline material.

[0055] Into the three-necked flask, 112g of sorbic acid and 460g of methanol were further added, and the above steps were repeated to collect 110.3g of methyl sorbate product.

[0056] The yield of the sorbate was calculated to be 79.76%.

[0057] Example 3

[0058] Into a 1000ml three-necked flask equipped with a condenser tube, 112g of sorbic acid was charged, 460g of ethanol was poured, 2g of triethylsulfonium propyl p-toluenesulfonate catalyst was added, and the solution was stirred magnetically, and the reaction was carried out under reflux for 12 hours in an oil bath at a temperature of 75°C. The ethanol was distilled off and collected, and the collected ethanol was dried for recycling. After the ethanol was removed, water was added to the condenser tube of the three-necked flask, and the remaining liquid in the flask was cooled to 14°C, and the sorbic acid and triethylsulfonium propyl p-toluenesulfonate catalyst were crystallized, and then the upper liquid was poured into a single-necked flask and distilled under reduced pressure to collect 89.4g of ethyl sorbate product; the reduced pressure distillation was carried out at a pressure of -0.1 MPa and a distillation temperature of 55°C. The remaining three-necked flask was crystallized.

[0059] Into the three-necked flask, 112g of sorbic acid and 460g of ethanol were further charged, and the above steps were repeated to collect 108.0g of ethyl sorbate product.

[0060] The yield of the sorbate was calculated to be 78.33%.

[0061] Example 4

[0062] Into a 1000ml three-necked flask equipped with a condenser tube, 112g of sorbic acid was charged, 460g of ethanol was poured, 2g of triethylsulfonium propyl p-toluenesulfonate catalyst was added, and the solution was stirred magnetically, and the reaction was carried out under reflux for 12 hours in an oil bath at a temperature of 75°C. The ethanol was distilled off and collected, and the collected ethanol was dried for recycling. After the ethanol was removed, water was added to the condenser tube of the three-necked flask, and the remaining liquid in the flask was cooled to 14°C, and the sorbic acid and triethylsulfonium propyl p-toluenesulfonate catalyst were crystallized, and then the upper liquid was poured into a single-necked flask and distilled under reduced pressure to collect 89.4g of ethyl sorbate product; the reduced pressure distillation was carried out at a pressure of -0.1 MPa and a distillation temperature of 55°C. The remaining three-necked flask was crystallized.

[0063] Into the three-necked flask, 112g of sorbic acid and 460g of ethanol were further charged, and the above steps were repeated to collect 108.0g of ethyl sorbate product.

[0064] The yield of the sorbate was calculated to be 78.33%.

[0065] Comparative Example 1

[0066] Into a 1000ml three-necked flask equipped with a condenser, 112g of sorbic acid was added, 460g of methanol was poured in, 2g of triethylsulfonium propylsulfate ammonium hydrogen sulfate catalyst was added, and the solution was stirred magnetically and dissolved, and the reaction was heated to reflux in an oil bath for 12 hours at a temperature of 75°C. The methanol was distilled and collected, and the collected methanol was dried for recycling. After the methanol was removed, water was added to the condenser of the three-necked flask, and the remaining liquid in the flask was cooled to 16°C, and the sorbic acid and triethylsulfonium propylsulfate ammonium hydrogen sulfate catalyst crystallized out, and then the upper liquid was poured into a single-necked flask and distilled under reduced pressure to collect 90.7g of methyl sorbate product; the pressure in the reduced pressure distillation was -0.1Mpa, and the distillation temperature was 55°C. The remaining three-necked flask crystalline material.

[0067] Into the three-necked flask, 112g of sorbic acid and 460g of methanol were added, and the above steps were repeated to collect 55.2g of methyl sorbate product.

[0068] The yield of sorbate was calculated to be 59.90%.

[0069] Comparative Example 2

[0070] Into a 1000ml three-necked flask equipped with a condenser, 112g of sorbic acid was added, 512g of methanol and 2g of concentrated sulfuric acid were poured in as catalyst, and the solution was stirred magnetically and dissolved, and the reaction was heated to reflux in an oil bath for 10 hours at a temperature of 70°C. The methanol was distilled and collected, and after the methanol was removed, the reaction liquid was poured into a separatory funnel, 500ml of ether was added, and the ether layer was washed with 0.1mol / L sodium bicarbonate solution until it was neutral, the ether layer was collected, and the ether was removed by reduced pressure distillation to obtain the methyl sorbate product.

[0071] Comparing Examples 1-4 and Comparative Example 1, it can be seen that after the reaction of alcohol, sorbic acid and ionic liquid catalyst was completed, the remaining liquid after the reaction was cooled, the cooling temperature was not within the range of 6-14°C, and the yield of sorbate product obtained by reduced pressure distillation was low when the recovered sorbic acid and ionic liquid catalyst were recycled; this is mainly because when the remaining liquid after the reaction is cooled and the cooling temperature is not within the range of 6-14°C, the recovered sorbic acid and ionic liquid catalyst contain other impurities, which affects the reaction rate, thereby reducing the yield of sorbate product. In Examples 1-4, the cooling temperature of the remaining liquid after the reaction was within the range of 8-10°C, and the yield of sorbate product prepared was relatively high; different types of alcohol and ionic liquid catalyst had little effect on the reaction rate, and basically did not affect the yield of sorbate.

[0072] In Comparative Example 2, concentrated sulfuric acid was used as a catalyst, the product sorbate obtained by the reaction was separated using ether organic solution, and the remaining sorbic acid and concentrated sulfuric acid catalyst were removed using alkaline liquid, resulting in organic waste liquid, alkaline waste liquid, and the remaining sorbic acid could not be recycled, increasing the production cost.

[0073] Compared with Comparative Examples 1 and 2, the preparation method of sorbate ester in Example 1-4 can realize the reuse of sorbic acid and ionic liquid catalyst without reducing the yield of sorbate ester, i.e. without producing organic waste liquid and alkaline waste liquid, and can realize continuous production and improve production efficiency.

[0074] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a sorbate ester, characterized by, The method comprises the following steps: A: adding the reactants sorbic acid, alcohol, and ionic liquid catalyst into a reaction container, stirring at room temperature, and then heating to react after the reactants are completely dissolved; B: distilling the liquid after the reaction in step A, and recovering the unreacted alcohol fraction; C: cooling the remaining liquid after distillation in step B to crystallize the sorbic acid and ionic liquid catalyst, then separating the crystals; and performing vacuum distillation on the obtained liquid to collect the sorbate product fraction; D: recycling the crystallized sorbic acid and ionic liquid catalyst in step C to step A to further react with newly added alcohol, sorbic acid, and ionic liquid catalyst; The cooling temperature of the remaining liquid in step C is 6-14°C. The ionic liquid catalyst comprises at least one of triethylsulfonic acid propyl-p-toluenesulfonic acid salt ([NEt3PS]pSTA), triethylsulfonic acid propyl ammonium hydrogen sulfate ([NEt3PS]HSO4), and 1-sulfonic acid propyl-3-methyl imidazole hydrogen sulfate ([MIMPS]HSO4).

2. The method of preparing a sorbate ester according to claim 1, characterized in that, The cooling temperature of the remaining liquid in step C is 8-10°C.

3. The method of preparing a sorbate ester according to claim 1, characterized by, The mass ratio of sorbic acid, alcohol, and ionic liquid catalyst in step A is 1:(1-5):(0.01-0.05).

4. The method of preparing a sorbate ester according to claim 3, characterized in that, The mass ratio of sorbic acid, alcohol, and ionic liquid catalyst in step A is 1:(2-5):(0.01-0.03).

5. The method of preparing a sorbate ester according to claim 1, characterized by, The reaction temperature in step A is 50-100°C, and the reaction time is 4-12h.

6. The method of preparing a sorbate ester according to claim 5, characterized in that, The reaction temperature in step A is 60-80°C, and the reaction time is 6-10h.

7. The method of preparing a sorbate ester according to claim 1, characterized by, The distillation pressure in step C is -0.08 Mpa to -0.1 Mpa, and the distillation temperature is 40-80°C.

8. The method for preparing sorbate according to claim 1, characterized in that, The alcohol is a saturated aliphatic alcohol containing 1-4 carbon atoms.