阅读说明：本技术 一种柠檬酸异丙酯的制备方法 (Preparation method of isopropyl citrate ) 是由 杜明松 于 2020-12-22 设计创作，主要内容包括：本发明提供了一种柠檬酸异丙酯的制备方法,所述制备方法包括如下步骤：柠檬酸和异丙醇在固体酸催化剂的催化下进行酯化反应,得到所述柠檬酸异丙酯；其中,所述固体酸催化剂选自固定化对苯磺酸和/或强酸型阳离子交换树脂。本发明提供的柠檬酸异丙酯的制备方法简单易行,后处理方便,仅需简单过滤,蒸馏出低沸物即可；并且本发明的制备方法可以提高酯化反应的反应效率,同时对设备无腐蚀,催化剂易于回收再利用,活性基本保持不变。(The invention provides a preparation method of isopropyl citrate, which comprises the following steps: carrying out esterification reaction on citric acid and isopropanol under the catalysis of a solid acid catalyst to obtain the isopropyl citrate; wherein the solid acid catalyst is selected from immobilized p-benzenesulfonic acid and/or strong acid type cation exchange resin. The preparation method of the isopropyl citrate provided by the invention is simple and feasible, the post-treatment is convenient, and only simple filtration is needed to distill low-boiling-point substances; the preparation method can improve the reaction efficiency of the esterification reaction, does not corrode equipment, is easy to recycle the catalyst, and basically keeps the activity unchanged.)

1. A preparation method of isopropyl citrate is characterized by comprising the following steps:

carrying out esterification reaction on citric acid and isopropanol under the catalysis of a solid acid catalyst to obtain the isopropyl citrate;

wherein the solid acid catalyst is selected from immobilized p-benzenesulfonic acid or activated strong acid type cation exchange resin.

2. The preparation method of claim 1, wherein the solid acid catalyst is immobilized p-benzenesulfonic acid, and the mass ratio of the solid acid catalyst to the citric acid is 1 (10-20);

and/or the solid acid catalyst is activated strong acid type cation exchange resin, and the mass ratio of the solid acid catalyst to the citric acid is 1 (5-10).

3. The production method according to claim 1 or 2, characterized in that the production method of the immobilized p-benzenesulfonic acid comprises:

dropwise adding a calcium chloride solution into a mixed solution of sodium alginate, polyvinyl alcohol and p-benzenesulfonic acid for reaction, and then filtering to obtain the immobilized p-benzenesulfonic acid;

preferably, the mass ratio of the sodium alginate to the polyvinyl alcohol to the p-benzenesulfonic acid is (3-5) to 10:1, and further preferably is 4:10: 1;

preferably, the mass ratio of the p-benzenesulfonic acid to the calcium chloride is (1.5-2) to 1;

preferably, the concentration of the calcium chloride solution is 2-5 wt%.

4. The production method according to any one of claims 1 to 3, wherein the method for activating the strong acid type cation exchange resin comprises:

reacting strong acid type cation exchange resin with alkali, and then activating by using strong acid to obtain the activated strong acid type cation exchange resin;

preferably, the activation method of the strong acid type cation exchange resin comprises the following steps:

adding strong acid type cation exchange resin into a sodium hydroxide solution, soaking for 30min, washing with water to be neutral, adding hydrochloric acid for activation, and then washing, filtering and drying to obtain the activated strong acid type cation exchange resin.

5. The production method according to any one of claims 1 to 4, wherein the mass ratio of the citric acid to the isopropyl alcohol is 1 (1.2 to 1.5).

6. The process according to any one of claims 1 to 5, wherein the esterification reaction is carried out at a reaction temperature of 70 to 100 ℃, preferably for a reaction time of 5 to 12 hours;

and/or the vacuum degree of the esterification reaction is-0.05 to-0.08 MPa.

7. The preparation method according to claim 6, wherein during the esterification reaction, part of the isopropanol and the water generated by the reaction are discharged out of the reaction system and do not flow back into the reaction system;

preferably, part of the isopropanol is fed during the esterification reaction every 0.3 to 0.6 h.

8. The process according to any one of claims 1 to 7, wherein the process further comprises filtration after completion of the reaction and then distillation under reduced pressure to remove low boiling substances.

9. The preparation method according to claim 8, characterized in that the temperature of the reduced pressure distillation is 100-120 ℃, and the time is preferably 0.5-2 h;

and/or the vacuum degree of the reduced pressure distillation is-0.08 to-0.1 MPa.

10. The production method according to any one of claims 1 to 9, characterized by comprising the steps of:

(1) the solid acid catalyst is prepared by a method comprising the following steps: dropwise adding a calcium chloride solution into a mixed solution of sodium alginate, polyvinyl alcohol and p-benzenesulfonic acid in a mass ratio of (3-5) to 10:1 for reacting for 20-25h, and then filtering, drying and screening to obtain immobilized p-benzenesulfonic acid;

alternatively, the solid acid catalyst is prepared by a process comprising the steps of: adding strong acid type cation exchange resin into a sodium hydroxide solution, soaking for 30min, washing with water to be neutral, adding hydrochloric acid for activation, and then washing, filtering and drying to obtain activated strong acid type cation exchange resin;

(2) carrying out esterification reaction on citric acid and isopropanol with the mass ratio of 1 (1.2-1.5) at 70-100 ℃ and-0.05-0.08 MPa for 5-12h under the catalysis of the solid acid catalyst, discharging part of isopropanol and water out of a reaction system in the reaction process, and supplementing part of isopropanol every 0.3-0.6 h;

the catalyst is immobilized p-benzenesulfonic acid, the mass ratio of the catalyst to citric acid is 1 (10-20), or the catalyst is activated strong acid type cation exchange resin, and the mass ratio of the catalyst to citric acid is 1 (5-10);

(3) filtering after the reaction is finished, and then carrying out reduced pressure distillation at the temperature of 100-120 ℃ for 0.5-2h, wherein the vacuum degree is-0.08 to-0.1 MPa, thus obtaining the isopropyl citrate.

Technical Field

The invention belongs to the technical field of chemical synthesis, and relates to a preparation method of isopropyl citrate.

Background

The isopropyl citrate is a mixture of monoisopropyl citrate, diisopropyl citrate and triisopropyl citrate, wherein the proportion of the monoisopropyl citrate is the highest and about 70 percent, and the isopropyl citrate and trace metals in the grease act to generate inactive compounds so as to prevent oxidation. At present, isopropyl citrate is mainly used as an antioxidant and a chelating agent, and can be used for preventing rancidity of grease, butter and the like.

At present, isopropyl citrate is generally prepared by esterifying citric acid and isopropanol under the catalytic action of a catalyst, concentrated sulfuric acid is used as the catalyst in the conventional production process at present, but the concentrated sulfuric acid has strong acidity, severe corrosion to equipment in the production process and certain potential safety hazard, and meanwhile, the concentrated sulfuric acid is used as the catalyst, so that more side reactions exist, the post-treatment process is complex and the waste acid pollutes the environment.

CN101270045A discloses a method for synthesizing citric acid triester with hydrophobic solid acid as a catalyst, which adopts hydrophobic solid acid as a catalyst to prepare citric acid triester of alcohol with 1-3C atoms, adds a water-carrying agent in the reaction process, and adopts a batch sample injection method.

Therefore, it is desirable to provide a novel process for the preparation of isopropyl citrate.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a preparation method of isopropyl citrate, which is simple and feasible, is convenient to post-treat, and only needs simple filtration to distill low-boiling-point substances; the preparation method can improve the reaction efficiency of the esterification reaction, does not corrode equipment, is easy to recycle the catalyst, and basically keeps the activity unchanged.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a process for the preparation of isopropyl citrate, said process comprising the steps of:

carrying out esterification reaction on citric acid and isopropanol under the catalysis of a solid acid catalyst to obtain the isopropyl citrate;

wherein the solid acid catalyst is selected from immobilized p-benzenesulfonic acid or activated strong acid type cation exchange resin.

According to the invention, the solid acid catalyst is selected as the catalyst for the esterification reaction of the citric acid and the isopropanol, the solid acid catalyst has no obvious corrosion to equipment, is easy to recover, can be recycled only by simple filtration, and can be recycled, and the activity can be basically kept unchanged in the recycling process.

The esterification reaction of the invention can realize the purpose of the invention without adding additional components such as water-carrying agents and the like.

The preparation method provided by the invention can improve the reaction efficiency of the esterification reaction, and the yield of the product can reach more than 95%.

The reaction formula of the esterification reaction of the invention is as follows:

when the catalyst of the present invention is immobilized p-benzenesulfonic acid, in order to ensure the best catalytic effect of the solid acid catalyst, the present invention preferably has a mass ratio of the solid acid catalyst to citric acid of 1 (10-20), for example, 1:12, 1:15, 1:16, 1:18, etc.

When the catalyst of the present invention is an activated strong acid type cation exchange resin, in order to ensure the best catalytic effect of the solid acid catalyst, the present invention preferably has a mass ratio of the solid acid catalyst to citric acid of 1 (5-10), for example, 1:6, 1:7, 1:8, 1:9, etc.

The excessive or insufficient amount of the catalyst can cause slight reduction of the catalytic efficiency, influence the catalytic efficiency, cause lower product yield and indirectly increase the production cost.

In order to further improve the catalytic effect of the catalyst and improve the product yield, the invention limits the preparation method of the solid acid catalyst, and the preparation method of the immobilized p-benzenesulfonic acid comprises the following steps:

and dropwise adding a calcium chloride solution into a mixed solution of sodium alginate, polyvinyl alcohol and p-benzenesulfonic acid for reaction, and then filtering to obtain the immobilized p-benzenesulfonic acid.

In a preferable embodiment of the invention, the mass ratio of sodium alginate to polyvinyl alcohol to p-benzenesulfonic acid is (3-5):10:1, and more preferably 4:10: 1.

In a preferred embodiment of the present invention, the mass ratio of p-benzenesulfonic acid to calcium chloride is (1.5-2) to 1, for example, 1.6:1, 1.7:1, 1.8:1, 1.9:1, etc.

After filtration, the obtained immobilized p-benzenesulfonic acid is dried and then sieved to remove fine particles, preferably 60 mesh sieve.

The activation method of the strong acid type cation exchange resin comprises the following steps:

and (3) reacting the strong acid type cation exchange resin with alkali, and then activating by using strong acid to obtain the activated strong acid type cation exchange resin.

As a specific embodiment of the present invention, the method for activating the strong acid type cation exchange resin comprises:

adding strong acid type cation exchange resin into a sodium hydroxide solution, soaking for 30min, washing with water to be neutral, adding hydrochloric acid for activation, and then washing, filtering and drying to obtain the activated strong acid type cation exchange resin.

The catalyst prepared by the preparation method provided by the invention has better catalytic effect, and the product yield can be improved while the dosage of the catalyst is reduced.

The mass ratio of the citric acid to the isopropanol is 1 (1.2-1.5), such as 1:1.3, 1:1.4 and the like.

The esterification reaction of the present invention has a reaction temperature of 70-100 deg.C, such as 75 deg.C, 80 deg.C, 85 deg.C, 90 deg.C, 95 deg.C, etc., and preferably has a reaction time of 5-12h, such as 6h, 7h, 8h, 9h, 10h, 11h, etc.

The vacuum degree of the esterification reaction is-0.05 to-0.08 MPa, such as-0.06 MPa and-0.07 MPa.

In the invention, the esterification reaction is reduced pressure distillation, part of distilled isopropanol and water generated in the reaction are discharged from the reaction system and do not flow back to the reaction system, the fraction contains part of isopropanol which can be separated by a water separation device, and the obtained isopropanol can be recycled.

Since part of the isopropanol is distilled off, part of the isopropanol is supplemented every 0.3 to 0.6h, for example every 0.5h, during the esterification reaction, and the addition amount of the isopropanol is preferably the evaporation amount of the isopropanol.

After the esterification reaction, it is necessary to remove low boiling substances generated by the reaction, and it is preferable that the production method further comprises filtering after the completion of the reaction, and then distilling under reduced pressure to remove low boiling substances.

As a preferred technical scheme of the invention, the temperature of the reduced pressure distillation is 100-120 ℃, such as 105, 110, 115 and the like, and the preferred time is 0.5-2h, such as 1, 1.5 and the like.

As a preferable technical scheme of the invention, the vacuum degree of the reduced pressure distillation is-0.08 to-0.1 MPa.

As a specific embodiment of the present invention, the preparation method comprises the steps of:

(1) the solid acid catalyst is prepared by a method comprising the following steps: dropwise adding a calcium chloride solution into a mixed solution of sodium alginate, polyvinyl alcohol and p-benzenesulfonic acid in a mass ratio of (3-5) to 10:1 for reacting for 20-25h, and then filtering, drying and screening to obtain immobilized p-benzenesulfonic acid;

alternatively, the solid acid catalyst is prepared by a process comprising the steps of: adding strong acid type cation exchange resin into a sodium hydroxide solution, soaking for 30min, washing with water to be neutral, adding hydrochloric acid for activation, and then washing, filtering and drying to obtain activated strong acid type cation exchange resin;

(2) carrying out esterification reaction on citric acid and isopropanol with the mass ratio of 1 (1.2-1.5) at 70-100 ℃ and-0.05-0.08 MPa for 5-12h under the catalysis of the solid acid catalyst, discharging part of isopropanol and water out of a reaction system in the reaction process, and supplementing part of isopropanol every 0.3-0.6 h;

wherein the solid acid catalyst is immobilized p-benzenesulfonic acid, the mass ratio of the catalyst to citric acid is 1 (10-20), or the solid acid catalyst is activated strong acid type cation exchange resin, and the mass ratio of the catalyst to citric acid is 1 (5-10);

(3) filtering after the reaction is finished, and then carrying out reduced pressure distillation at the temperature of 100-120 ℃ for 0.5-2h, wherein the vacuum degree is-0.08 to-0.1 MPa, thus obtaining the isopropyl citrate.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the invention, the solid acid catalyst is selected as the catalyst for the esterification reaction of citric acid and isopropanol, the solid acid catalyst has no obvious corrosion to equipment, is easy to recover, can be recycled only by simple filtration, and can be recycled, and the activity can be basically kept unchanged in the recycling process;

(2) the preparation method provided by the invention can improve the reaction efficiency of the esterification reaction, and the yield of the product can reach more than 95% at most;

(3) the purpose of the invention can be realized without adding additional components such as water-carrying agents and the like in the esterification reaction;

(4) the esterification reaction provided by the invention has mild conditions and simple process, and is suitable for industrial production.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the specific embodiments are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Example 1

This example provides a method for preparing immobilized p-benzenesulfonic acid.

Adding 20g of sodium alginate, 50g of polyvinyl alcohol and 5g of p-toluenesulfonic acid into 400mL of purified water, uniformly mixing, heating in a 90 ℃ constant-temperature water bath kettle to completely dissolve the sodium alginate, cooling to about 35 ℃, dropwise adding 400mL of 2% calcium chloride solution into the solution, continuously and slowly stirring, after dropwise adding, placing the reaction solution at 4 ℃ for crosslinking for 24 hours, taking out, filtering, drying at 45 ℃ under reduced pressure for 5 hours, and sieving by a 60-mesh sieve to remove fine particles to obtain the immobilized p-toluenesulfonic acid.

Examples 2 to 3

This example provides a method for preparing immobilized p-benzenesulfonic acid.

The difference from example 1 is that in this example, the mass ratio of sodium alginate to polyvinyl alcohol to p-benzenesulfonic acid is 1:10:1 (example 2) and 7:10:1 (example 3).

Example 4

This example provides a method for activating a strong acid type cation exchange resin.

Adding 100g of strong acid type cation exchange resin into 200mL of 5% sodium hydroxide, soaking for 30min, washing with water to neutrality, adding 300mL of 5% hydrochloric acid, activating, soaking for 30min, adding purified water, washing until effluent is neutral, filtering, and vacuum drying at 50 deg.C.

Example 5

This example provides a process for the preparation of isopropyl citrate.

(1) Adding 5g of immobilized p-toluenesulfonic acid provided in example 1 into a mixed solution of 50g of citric acid and 300mL of isopropanol, heating at 75 ℃, distilling under reduced pressure, reacting for 5h, separating out fractions every 30min, adding distilled isopropanol, and totally adding 1350mL of isopropanol;

(2) after the reaction was complete, filtration was carried out and the filtrate was distilled at 100 ℃ under reduced pressure for 1 hour to give 62.7g of a product in a theoretical yield of 97.1% calculated on the basis of (70% for monoisopropyl ester: diisopropyl ester: triisopropyl ester: 25% for 5%).

Example 6

This example provides a process for the preparation of isopropyl citrate.

The difference from example 5 is that the solid acid catalyst used in this example is the immobilized p-toluenesulfonic acid provided in example 2, and finally isopropyl citrate 50.8g is obtained with a yield of 78.6%.

Example 7

This example provides a process for the preparation of isopropyl citrate.

The difference from example 1 is that the solid acid catalyst used in this example is the immobilized p-toluenesulfonic acid provided in example 3, and 43.6g of isopropyl citrate is finally obtained with a yield of 67.5%.

Example 8

This example provides a process for the preparation of isopropyl citrate.

The difference from example 1 is that the mass ratio of citric acid to immobilized p-toluenesulfonic acid in this example is 5:1, and 50.5g of isopropyl citrate is finally obtained with a yield of 78.2%.

Example 9

This example provides a process for the preparation of isopropyl citrate.

The difference from example 1 is that the mass ratio of citric acid to immobilized p-toluenesulfonic acid in this example is 25:1, and the final yield of isopropyl citrate is 38.7g and 59.9%.

Example 10

This example provides a process for the preparation of isopropyl citrate.

(1) Adding 5g of the activated strong acid type cation exchange resin provided in the embodiment 4 into a mixed solution of 50g of citric acid and 300mL of isopropanol, heating at 80 ℃, distilling under reduced pressure, reacting for 8h, separating out a fraction every 30min, supplementing distilled isopropanol, and totally supplementing 2560mL of isopropanol;

(2) after the reaction is finished, filtering is carried out, and the filtrate is distilled under reduced pressure at 100 ℃ for 1h to obtain 61.5g of a product.

The theoretical yield was calculated as (70%: 25%: 5%) for the monoisopropyl ester: diisopropyl ester: triisopropyl ester, and the yield was 95.2%.

Example 11

This example provides a process for the preparation of isopropyl citrate.

The difference from example 1 is that the mass ratio of citric acid to activated strong acid type cation exchange resin in this example was 2:1, and 61.8g of isopropyl citrate was finally obtained with a yield of 95.7%.

Example 12

This example provides a process for the preparation of isopropyl citrate.

The difference from example 1 is that the mass ratio of citric acid to activated strong acid type cation exchange resin in this example is 15:1, and 40.6g of isopropyl citrate is finally obtained with a yield of 62.8%.

Comparative example 1

The comparative example provides a method for preparing isopropyl citrate.

The difference from example 1 is that in this comparative example, the solid acid catalyst was replaced with concentrated sulfuric acid, and finally, isopropyl citrate 32.1g was obtained in a yield of 49.7%.

Comparative example 2

The comparative example provides a method for preparing isopropyl citrate.

The difference from example 1 is that in this comparative example, the solid acid catalyst was replaced with a hydrophobic solid acid catalyst (active component was magnesium sulfate, support was activated carbon), and finally 30.2g of isopropyl citrate was obtained with a yield of 46.7%.

Although the invention has been described in detail hereinabove by way of general description, specific embodiments and experiments, it will be apparent to those skilled in the art that many modifications and improvements can be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.