A preparation method of 2,3,5-trimethylhydroquinone diester

Abstract

The present invention relates to a method for preparing 2,3,5-trimethyl hydroquinone diester from 3,5,5-trimethyl-cyclohexane-2-ene-1,4-diketone (oxyisophorone). The method is to prepare 2,3,5-trimethyl hydroquinone diester by rearrangement reaction of oxyisophorone and esterification reaction with acid anhydride under the catalysis of 3-hydroxypropanesulfonic acid modified silica solid catalyst. During the reaction, the peroxide value of the reaction solution is controlled to be less than 20, and 2,3,5-trimethyl hydroquinone diester with a chromaticity lower than 20 Hazen is prepared, and the product purity is more than 99.5%, and the next step reaction can be carried out without further purification, and the catalyst can be recycled, reducing the generation of three wastes, which is more conducive to industrial production.

Description

Technical Field

[0001] The invention relates to a method for synthesizing 2,3,5-trimethylhydroquinone diester, in particular to a method for preparing 2,3,5-trimethylhydroquinone diester from 3,5,5-trimethyl-cyclohex-2-ene-1,4-dione (oxyisophorone, KIP). Background Art

[0002] 2,3,5-Trimethylhydroquinone diester is an important intermediate for the preparation of vitamin E, which can directly react with isophytol to produce vitamin E acetate.

[0003] There are many known methods for converting oxoisophorone to 2,3,5-trimethylhydroquinone diester:

[0004] In DE2149159, 2,3,5-trimethylhydroquinone diester is prepared by reacting oxoisophorone with acetic anhydride under the catalysis of protonic acid or Lewis acid. The disadvantage of this method is that a large amount of acid (sulfuric acid, nitric acid, hydrochloric acid, etc.) must be used, and the reaction yield is low (66%). After the reaction is completed, alkali is required to neutralize the catalyst, which produces a large amount of three wastes, which is not conducive to green industrial production.

[0005] DE19627977 describes a method for preparing 2,3,5-trimethylhydroquinone diester similar to DE2149159. By using trifluoromethanesulfonic acid, chlorosulfonic acid, fuming sulfuric acid, etc. as catalysts, this method can reduce the stoichiometric acid required in DE2149159 to a catalytic amount, and the yield of 2,3,5-trimethylhydroquinone diester can reach up to 90%. In addition, CN1102138C, CN1420859 and CN1241559A also disclose methods for preparing 2,3,5-trimethylhydroquinone diester by using trifluoromethanesulfonic acid, polyphosphoric acid, etc. as catalysts to catalyze the reaction of KIP and acetic anhydride. The acid catalyst used in such methods is easy to form acid mist at room temperature, and the equipment requirements are very high in production.

[0006] CN1886361A discloses a novel method for preparing 2,3,5-trimethylhydroquinone diester. The method uses a trivalent indium salt (such as indium trichloride, indium trifluoromethanesulfonate) as a catalyst to catalyze the reaction of KIP and anhydride to prepare 2,3,5-trimethylhydroquinone diester. Although the corresponding yield can reach 90%, the catalyst used in the method is expensive and easy to pollute the environment.

[0007] CN101607896 reported the use of ionic liquid as a catalyst to catalyze the reaction of KIP and acid anhydride to prepare 2,3,5-trimethylhydroquinone diester. The amount of ionic liquid used was small and the separation was simple, but the reaction conversion rate was only 38%, the selectivity was 93%, and the single-pass yield was low.

[0008] Based on the shortcomings of the above prior art products, such as low yield, high catalyst dosage and low product purity, the present invention modifies silicon dioxide by 3-hydroxypropanesulfonic acid to improve the reaction selectivity, and at the same time adds an antioxidant to the reaction system to control the peroxide value of the reaction solution, thereby avoiding oxidation of the product, thereby avoiding product deterioration and improving product quality. Summary of the invention

[0009] In view of the disadvantages of low yield, high catalyst dosage and low product purity of the prior art products, the purpose of the present invention is to provide a method for producing 2,3,5-trimethylhydroquinone diester more conducive to industrialization. By using 3-hydroxypropanesulfonic acid modified silica catalysis, 2,3,5-trimethylhydroquinone diester is obtained with high selectivity, and the peroxide value of the reaction solution is controlled at the same time, so as to avoid oxidation and deterioration of the product and improve the product quality. The process route has good reaction selectivity, simple operation and easy industrial production.

[0010] In order to achieve the above invention object, the technical solution of the present invention is as follows:

[0011] A method for preparing 2,3,5-trimethylhydroquinone diester from 3,5,5-trimethyl-cyclohex-2-ene-1,4-dione (oxyisophorone, KIP) comprises: oxyisophorone and acetic anhydride are catalyzed by a 3-hydroxypropanesulfonic acid modified silica catalyst and in the presence of an antioxidant to obtain 2,3,5-trimethylhydroquinone diester in high yield.

[0012] The reaction equation is as follows:

[0013]

[0014] Oxoisophorone undergoes rearrangement reaction under acid catalysis and then further reacts with acetic anhydride to generate 2,3,5-trimethylhydroquinone diester. During the rearrangement process, due to the simultaneous migration of methyl and hydroxyl groups, the impurity 3,4,5-trimethylhydroquinone diester is generated. When preparing vitamin E, this impurity will also react with isophytol to produce impurities that are difficult to separate from vitamin E. The scheme of the present invention avoids the migration of hydroxyl groups during the rearrangement process and improves the reaction selectivity through the use of 3-hydroxypropanesulfonic acid modified silica. The purity of the trimethylhydroquinone diester prepared by the reaction can reach more than 99.9%.

[0015] In the present invention, the 3-hydroxypropanesulfonic acid modified silica is obtained by reacting 3-hydroxypropanesulfonic acid and silica, and the mass ratio of silica to 3-hydroxypropanesulfonic acid is 1:0.01-0.2, preferably 1:0.05-0.1;

[0016] In a specific embodiment of the present invention, 3-hydroxypropanesulfonic acid modified silicon dioxide is prepared by adding 3-hydroxypropanesulfonic acid and silicon dioxide to a solvent, stirring at a certain temperature, and then filtering to obtain a modified catalyst; the solvent is preferably an alkane solvent, and n-hexane and n-heptane are further preferred; the amount of solvent is preferably 5-50 times the mass of silicon dioxide, and more preferably 10-20 times; the reaction temperature of 3-hydroxypropanesulfonic acid modified silicon dioxide is preferably 50-100°C, and more preferably 60-80°C; the stirring time for 3-hydroxypropanesulfonic acid modified silicon dioxide is preferably 1-10h, and more preferably 2-5h.

[0017] In the present invention, the amount of 3-hydroxypropanesulfonic acid modified silica catalyst is 0.1%-1% (mass ratio, based on oxyisophorone), and the amount of catalyst is preferably 0.2%-0.5%;

[0018] In the present invention, the amount of acetic anhydride is 2 to 20 eq (based on oxyisophorone), preferably 2 eq to 10 eq;

[0019] In the present invention, the 3-hydroxypropanesulfonic acid modified silica catalyst is first mixed with acetic anhydride, and then an antioxidant and oxyisophorone are added;

[0020] In the present invention, the antioxidant is preferably a phosphite antioxidant, and more preferably antioxidant 168 and antioxidant 626;

[0021] In the present invention, the antioxidant is added once, and the amount of the antioxidant is 0.01%-0.1% (mass ratio, based on oxyisophorone), and the amount is preferably 0.02%-0.05%; preferably, after the antioxidant is added, the peroxide value of the reaction solution is not higher than 20, preferably not higher than 10.

[0022] In the present invention, the oxyisophorone can be added all at once or added dropwise, preferably added dropwise, and the addition time is usually 4-10 hours, preferably 6-8 hours;

[0023] In the present invention, the reaction temperature of oxyisophorone and acetic anhydride is usually 20-100° C., preferably 30-60° C.; the reaction time is usually 0.5-10 h after the complete addition of oxyisophorone, preferably 1-2 h.

[0024] In the present invention, after the reaction is completed, the catalyst can be removed by filtration, column chromatography, etc., preferably filtration.

[0025] In the present invention, after removing the catalyst, the reaction solution is further distilled under reduced pressure to remove the reaction solvent and the generated acetic acid, the absolute pressure of the reduced pressure distillation is 500-5000 Pa, preferably 500-2000 Pa; the distillation temperature is 50-100° C., preferably 60-80° C.;

[0026] The reaction solution from which the solvent has been removed is further subjected to reduced pressure distillation to obtain 2,3,5-trimethylhydroquinone diester, wherein the absolute pressure of the reduced pressure distillation is 50-500 Pa, preferably 100-200 Pa; the distillation temperature is 100-200° C., preferably 120-150° C.;

[0027] The 2,3,5-trimethylhydroquinone diester is prepared by the scheme of the present invention, the purity of the product is greater than 99.9%, the chromaticity is lower than 20 Hazen, and the yield can be greater than 98% (calculated as oxyisophorone).

[0028] The method of the present invention has the following advantages:

[0029] By using 3-hydroxypropanesulfonic acid modified silica catalyst, the use of corrosive strong acid is avoided, the reaction selectivity is improved, and the product purity is high, which can be greater than 99.9%;

[0030] By adding antioxidants, the peroxide value of the reaction solution is controlled, product deterioration is avoided, product color is reduced, and product quality is improved.

[0031] The method of the present invention is more conducive to industrial production. DETAILED DESCRIPTION

[0032] The following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the rights claimed by the present invention.

[0033] The reagents and solvents used in this process can be purchased from Aladdin Reagent Co., Ltd. The present invention is described in detail below in conjunction with the embodiments.

[0034] Gas chromatography analysis conditions: Agilent gas chromatograph polysiloxane column HP-5 was used for online determination, the vaporization chamber temperature was 250°C, the detector temperature was 250°C, the column temperature was programmed to rise: 50°C, 1 min; 80°C, 1 min; 10°C / min to 250°C, 10 min, and the injection volume was 0.2 μL.

[0035] Example 1

[0036] Preparation of catalyst: Weigh 100 g of silica and 10 g of 3-hydroxypropanesulfonic acid, add 1000 g of n-heptane, stir at 80° C. for 5 h, filter and obtain 109 g of 3-hydroxypropanesulfonic acid modified silica catalyst.

[0037] 204 g (2 mol) of acetic anhydride and 1.52 g of 3-hydroxypropanesulfonic acid modified silica were added to a 1 L reaction bottle in sequence, and the mixture was stirred at 20° C. 0.1 g of antioxidant 168 was added to the reaction system, and the peroxide value of the reaction solution was 8. 152.2 g (1 mol) of oxyisophorone was added dropwise to the reaction bottle, and the addition was completed within 6 h. After the addition was completed, the reaction was continued for 1 h, and the KIP conversion rate reached 99.5%. The reaction solution was then filtered to remove the catalyst, and acetic acid and acetic anhydride were removed from the reaction solution under an absolute pressure of 500 Pa and a temperature of 60° C. After the light components were removed, a simple distillation apparatus was replaced, and 232 g of trimethylhydroquinone diester was obtained under an absolute pressure of 100 Pa and a temperature of 200° C. The product had a chromaticity of 15 Hazen, a yield of 98.3%, and a GC content of 99.9%.

[0038] Example 2

[0039] Preparation of catalyst: Weigh 100 g of silica and 5 g of 3-hydroxypropanesulfonic acid, add 2000 g of n-hexane, stir at 80° C. for 4 h, filter with suction, and obtain 104.8 g of 3-hydroxypropanesulfonic acid-modified silica catalyst.

[0040] 204 g (2 mol) of acetic anhydride and 0.7 g of 3-hydroxypropanesulfonic acid modified silica were added to a 1 L reaction flask in sequence, and the mixture was stirred at 60° C. 0.05 g of antioxidant 626 was added to the reaction system. At this time, the peroxide value of the reaction solution was 9. 152.2 g (1 mol) of oxyisophorone was added dropwise to the reaction flask. The addition was completed within 4 h. After the addition was completed, the reaction was continued for 1 h. The KIP conversion rate reached 99.6%. The reaction solution was then filtered to remove the catalyst. The reaction solution was freed from acetic acid and acetic anhydride under an absolute pressure of 1000 Pa and a temperature of 80° C. After the light components were removed, a simple distillation apparatus was used to obtain 228 g of trimethylhydroquinone diester under an absolute pressure of 150 Pa and a temperature of 150° C. The product had a chromaticity of 18 Hazen, a yield of 96.6%, and a GC content of 99.9%.

[0041] Example 3

[0042] Preparation of catalyst: Weigh 100 g of silica and 20 g of 3-hydroxypropanesulfonic acid, add 2000 g of n-hexane, stir at 80° C. for 4 h, filter with suction, and obtain 119 g of 3-hydroxypropanesulfonic acid-modified silica catalyst.

[0043] 204 g (2 mol) of acetic anhydride and 0.3 g of 3-hydroxypropanesulfonic acid modified silica were added to a 1 L reaction bottle in sequence, and the mixture was stirred at 30 ° C. 0.08 g of antioxidant 168 was added to the reaction system. At this time, the peroxide value of the reaction solution was 9. 152.2 g (1 mol) of oxyisophorone was added dropwise to the reaction bottle. The addition was completed in 8 h. After the addition was completed, the reaction was continued for 1 h. The KIP conversion rate reached 99.8%. The reaction solution was then filtered to remove the catalyst. The reaction solution was freed from acetic acid and acetic anhydride under an absolute pressure of 600 Pa and a temperature of 70 ° C. After the light components were removed, a simple distillation apparatus was replaced. Under an absolute pressure of 200 Pa and a temperature of 150 ° C, 229 g of trimethylhydroquinone diester was obtained. The product chromaticity was 10 Hazen, the yield was 97.0%, and the GC content was 99.9%.

[0044] Comparative Example 1

[0045] 0.26 ml (4.6 mmol) of fluorosulfonic acid was added to 38.8 g (0.38 mol) of acetic anhydride, and then 23.3 g (0.15 mol) of oxoisophorone was added dropwise at 50-60° C. When the conversion rate of oxoisophorone was greater than 99%, the reaction solution was mixed with 130 g of ice water, and the pH was adjusted to 6 with a 40% aqueous sodium hydroxide solution. The crystallized trimethylhydroquinone diacetate was separated by filtration, and then washed with water. After vacuum drying at 50° C., trimethylhydroquinone diester was obtained with a purity of 92.7%. The product chromaticity was 220 Hazen, containing 31.8 g of trimethylhydroquinone diester, and the yield was 90.0%.

[0046] The above specific implementations do not limit the technical solutions of the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing 2,3,5-trimethylhydroquinone diester, comprising: Oxyisophorone and acetic anhydride react under the catalysis of 3-hydroxypropanesulfonic acid modified silica catalyst and in the presence of phosphite antioxidant to obtain 2,3,5-trimethylhydroquinone diester; The preparation method of 3-hydroxypropanesulfonic acid modified silica is as follows: 3-hydroxypropanesulfonic acid and silica are added into a solvent, stirred at 50-100° C. for 1-10 hours, and then filtered to obtain a modified catalyst; the mass ratio of silica to 3-hydroxypropanesulfonic acid is 1:0.01-0.2; After the antioxidant is added, the peroxide value of the reaction solution is not higher than 20.

2. The method according to claim 1, characterized in that The mass ratio of silicon dioxide to 3-hydroxypropanesulfonic acid is 1:0.05-0.

1.

3. The method according to any one of claims 1 to 2, characterized in that: The amount of the 3-hydroxypropanesulfonic acid modified silica catalyst used is 0.1%-1wt%, based on oxyisophorone.

4. The method according to claim 1, characterized in that: The amount of acetic anhydride used is 2 to 20 eq, based on the molar amount of oxyisophorone.

5. The method according to claim 1, characterized in that The antioxidant is selected from antioxidant 168 and antioxidant 626.

6. The method according to claim 5, characterized in that The amount of the antioxidant used is 0.01% to 0.1% by weight based on oxyisophorone.

7. The method according to claim 1, characterized in that The 3-hydroxypropanesulfonic acid modified silica catalyst is first mixed with acetic anhydride, and then an antioxidant and oxyisophorone are added, wherein the antioxidant is added at one time.

8. The method according to claim 7, characterized in that The oxyisophorone can be added all at once or dropwise.

9. The method according to claim 8, characterized in that The oxyisophorone is added dropwise for 4-10 hours.

10. The method according to claim 1, characterized in that The reaction temperature of oxyisophorone and acetic anhydride is 20-100°C.

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