Preparation method of 2, 3, 5-trimethylhydroquinone diacetate

Abstract

The invention provides a preparation method of 2, 3, 5-trimethylhydroquinone diacetate, which comprises the following steps: S1, under the action of a catalyst, reacting a first raw material to obtain a first product; the first raw material comprises oxoisophorone and acetic anhydride in a molar ratio of 1: X, and X is more than or equal to 1.6 and less than or equal to 1.9; s2, separating acetic acid in the first product to obtain a first crude product; s3, reacting the second raw material; the second raw material comprises newly added acetic anhydride and the first crude product; the molar ratio of the oxoisophorone in the step S1 to the acetic anhydride newly added in the step S3 is 1: Y, and X + Y is more than or equal to 2.6. According to the preparation method, acetic anhydride is fully utilized, and the separation operation difficulty of acetic anhydride and acetic acid in the product is small.

Description

Technical Field

[0001] The invention relates to a method for preparing 2,3,5-trimethylhydroquinone diacetate. Background Art

[0002] Vitamin E is a fat-soluble vitamin essential to the human body. It has the functions of anti-oxidation, anti-aging, improving immunity, and preventing infertility. It is widely used in the pharmaceutical, food, feed, health care products, and cosmetics industries. It is one of the nutrients necessary for the normal growth of organisms. In recent years, my country's feed industry has developed rapidly, and the demand for vitamin E has also increased sharply, with good prospects and extremely high returns.

[0003] Synthetic vitamin E mainly includes dl-α tocopherol and dl-α tocopherol acetate, wherein tocopherol acetate can be prepared by direct esterification of tocopherol or condensation of trimethyl hydroquinone diester and isophytol. The specific esterification steps of rearranging ethyl esterification of oxyisophorone and acetic anhydride to generate trimethyl hydroquinone diester under the action of a catalyst are as follows:

[0004]

[0005] CN101607896B discloses a method for preparing 2,3,5-trimethylhydroquinone diethyl ester from oxyisophorone. The method uses an acidic ionic liquid as a catalyst, and at a reaction temperature of -20°C to 130°C, oxyisophorone is rearranged and simultaneously esterified with anhydride to prepare 2,3,5-trimethylhydroquinone diethyl ester. The molar ratio of oxyisophorone to acetic anhydride is between 1:2 and 1:20. The method removes the acetic acid generated by the reaction and the unreacted acetic anhydride and oxyisophorone by reduced pressure distillation, and does not further explain the separation of acetic anhydride and acetic acid.

[0006] CN111675612B discloses a method for preparing 2,3,5-trimethylhydroquinone diethyl ester. The method comprises the following steps: oxyisophorone and acetic anhydride are subjected to rearrangement reaction under the catalysis of amino acid and polyethylene glycol-modified mesoporous molecular sieve supported solid acid to prepare 2,3,5-trimethylhydroquinone diester. The molar ratio of acetic anhydride to oxyisophorone is 2-20:1, preferably 5-10:1, and the separation of the recovered acetic anhydride and acetic acid is not described.

[0007] The above two steps of esterification require the addition of excessive acetic anhydride to promote the complete esterification of the raw materials. After the unreacted acetic anhydride and the acetic acid generated by the reaction are recovered, a mixture is obtained. It is necessary to separate by high tower distillation to obtain acetic acid with a purity greater than 99% and acetic anhydride with a purity greater than 98%. Distillation is difficult, the theoretical number of plates of the whole tower needs to reach about 50, and the reflux ratio is controlled at about 3-4. Therefore, the equipment investment for the distillation and separation of acetic anhydride and acetic acid is large and the energy consumption is high. If the number of plates of the distillation tower is reduced, the acetic anhydride recovered by distillation contains 5%-20% of acetic anhydride, which cannot be completely separated, the unit consumption of acetic anhydride is large, and the cost of raw materials is high. Summary of the invention

[0008] The present invention provides a method for preparing 2,3,5-trimethylhydroquinone diacetate in order to solve the problems that an excessive amount of acetic anhydride needs to be added during the ethyl esterification of oxoisophorone rearrangement in the prior art, which results in difficulty in separating acetic anhydride and acetic acid in the product. The preparation method makes full use of acetic anhydride, and the difficulty in separating acetic anhydride and acetic acid in the product is small.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for preparing 2,3,5-trimethylhydroquinone diacetate, which comprises the following steps:

[0011] S1. Under the action of a catalyst, reacting a first raw material to obtain a first product; the first raw material comprises oxyisophorone and acetic anhydride in a molar ratio of 1:X, wherein 1.6≤X≤1.9;

[0012] S2, separating the acetic acid in the first product to obtain a first crude product;

[0013] S3, reacting a second raw material; the second raw material includes newly added acetic anhydride and the first crude product; the molar ratio of oxyisophorone in step S1 to the newly added acetic anhydride in step S3 is 1:Y, wherein X+Y≥2.6.

[0014] In the present invention, in step S1, the catalyst is selected conventionally in the art, such as sulfuric acid, trifluoromethanesulfonic acid or perchloric acid.

[0015] In the present invention, in step S1, the amount of the catalyst used is preferably to promote the reaction. For example, the mass of the catalyst may be 0.1 wt%-0.2 wt% of the mass of the oxyisophorone.

[0016] In the present invention, in step S1, the first raw material may further include acetic acid, and the mass of the acetic anhydride may be more than 80wt% of the sum of the masses of the acetic anhydride and the acetic acid, preferably more than 85wt%, for example, 90wt%.

[0017] Wherein, the acetic acid can be added with the acetic anhydride in the form of a mixture. The mixture can be obtained from the previous reaction step S3. That is, the acetic acid and acetic anhydride mixture obtained in step S3 can be applied to the next reaction step S1.

[0018] In the present invention, in step S1, the reaction temperature is conventionally selected in the art, preferably 40-80°C, more preferably 50-70°C, such as 50°C, 60°C or 70°C.

[0019] In the present invention, in step S1, the reaction time is preferably such that the acetic anhydride reacts as completely as possible, for example, 2 hours.

[0020] In the present invention, in step S1, the reaction may be carried out until the content of acetic anhydride in the reaction system is below 1 wt %, preferably below 0.5 wt %.

[0021] In the present invention, in step S1, the molar ratio of the oxyisophorone to the acetic anhydride is preferably 1:(1.7-1.8).

[0022] In certain specific embodiments of the present invention, in step S1, the molar ratio of the oxyisophorone to the acetic anhydride is 1:1.7, 1:1.8 or 1:1.9.

[0023] In the present invention, in step S2, the separation method is conventional in the art, such as distillation, preferably vacuum distillation.

[0024] In the present invention, in step S2, the vacuum degree of the distillation can be 1000Pa.

[0025] In the present invention, in step S2, the distillation temperature may not exceed 50°C.

[0026] In the present invention, in step S2, the separation can separate the acetic acid as completely as possible.

[0027] In the present invention, in step S3, the reaction temperature is conventionally selected in the art, preferably 40-80°C, more preferably 50-70°C, such as 50°C, 60°C or 70°C.

[0028] In the present invention, in step S3, the reaction time is preferably such that the oxoisophorone reacts as completely as possible, for example, 2 hours.

[0029] In the present invention, in step S3, the reaction may be carried out until the content of the oxyisophorone in the reaction system is below 0.5 wt %, preferably below 0.3 wt %.

[0030] In the present invention, in step S3, X+Y may be ≥ 2.9, for example, X+Y = 2.9, 3.2 or 3.7.

[0031] In the present invention, in step S3, X+0.2Y may be ≥2.

[0032] In the present invention, in step S3, X+0.15Y may be ≥2.

[0033] In the present invention, in step S3, X+Y may be ≤3.9.

[0034] In the present invention, the molar ratio of the oxyisophorone in step S1 to the acetic anhydride newly added in step S3 can be 1:(1.0-2.0), preferably 1:(1.8-2.0).

[0035] In certain specific embodiments of the present invention, the molar ratio of the oxyisophorone in step S1 to the acetic anhydride newly added in step S3 is 1:1.0, 1:1.4 or 1:2.0.

[0036] In the present invention, in step S3, the reaction may be followed by quenching. The quenching method is conventional in the art, for example, the quenching may be performed by adding a quenching agent to the reaction system. The quenching agent is conventionally selected in the art, for example, sodium acetate. The amount of the quenching agent is preferably used to terminate the reaction, for example, twice the mass of the catalyst.

[0037] In the present invention, in step S3, after the reaction, distillation can be performed until no acetic anhydride or acetic acid is distilled out to obtain a second crude product. The distillation method is conventional in the art, for example, the distillation can be vacuum distillation. The vacuum degree of the distillation can be 800 Pa. The temperature of the distillation can not exceed 50°C.

[0038] Wherein, the second crude product can be further purified to obtain 2,3,5-trimethylhydroquinone diacetate. The purification step may include: adding n-heptane and then washing with water. The ratio of the n-heptane to the oxyisophorone in step S1 may be 1000mL:1000g. The ratio of the amount of water used in the water washing to the amount of the oxyisophorone in step S1 may be 200mL:1000g. The number of times of the water washing may be three times.

[0039] In certain specific embodiments of the present invention, in step S1, the catalyst is sulfuric acid, and in step S3, after the reaction, a quencher is added to the reaction system for quenching, and the quencher is sodium acetate. After the quenching, distillation is performed until no acetic anhydride or acetic acid is distilled out to obtain a second crude product, and the second crude product is further purified to obtain 2,3,5-trimethylhydroquinone diacetate.

[0040] Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0041] The reagents and raw materials used in the present invention are commercially available.

[0042] The positive and progressive effects of the present invention are:

[0043] (1) In the preparation method of the present invention, the distillation of acetic anhydride and acetic acid is effectively avoided. In the first stage, acetic anhydride is added in an amount less than the reaction equivalent to ensure that acetic anhydride is fully converted into acetic acid. The purity of the recovered acetic acid can reach more than 99 wt %, or even more than 99.5 wt %;

[0044] (2) In the preparation method of the present invention, an excess of acetic anhydride is added in the second stage to ensure that the raw material is fully converted into acetic ester. The purity of the recovered acetic anhydride can be greater than 80wt%, or even greater than 85wt%, and can be directly used in the first stage of the next esterification reaction;

[0045] (3) In the preparation method of the present invention, acetic anhydride is fully utilized, that is, the total amount of acetic anhydride used is less, and there is no distillation operation in the whole process, only ordinary distillation is required, the equipment investment is small, the unit consumption is low, and the energy consumption is low. DETAILED DESCRIPTION

[0046] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0047] In the following examples and comparative examples

[0048] The purity refers to the mass of 2,3,5-trimethylhydroquinone diacetate / the total mass of 2,3,5-trimethylhydroquinone diacetate and organic impurities×100%.

[0049] The content refers to the mass of 2,3,5-trimethylhydroquinone diacetate / the total mass of 2,3,5-trimethylhydroquinone diacetate, organic impurities, inorganic impurities (such as metal salt cation impurities, inorganic anion impurities) and water×100%.

[0050] The yield was calculated by actual yield / theoretical yield × 100%.

[0051] The purity of acetic anhydride / acetic acid in the recovered liquid is determined by gas chromatography. The acetic acid in the recovered liquid in the first stage consists of two parts, one of which is 90% of the acetic acid contained in the acetic anhydride itself, and the rest is acetic acid generated by the reaction.

[0052] The content and purity of 2,3,5-trimethylhydroquinone diacetate in the product are determined by liquid chromatography.

[0053] Example 1

[0054] A method for preparing 2,3,5-trimethylhydroquinone diacetate, wherein the reaction formula is as follows:

[0055]

[0056] The following steps are involved:

[0057] a. Add 1000 g (6.57 mol, 1.0 eq) of oxyisophorone, 1417 g of 90% acetic anhydride recovery liquid (containing 1275 g of acetic anhydride, 12.48 mol, 1.9 eq) and 1 g (0.1 wt%) of sulfuric acid, heat to 50°C, and react at 50°C for 2 h. At this time, the concentration of acetic anhydride in the reaction system is less than 0.5 wt% (detected by gas phase).

[0058] The reaction system was distilled under reduced pressure with a vacuum degree of 1000 Pa and a temperature not exceeding 50° C. The acetic acid was recovered until no liquid was discharged. A total of 889 g of acetic acid was recovered with a purity of 99.6 wt %, containing 0.4 wt % of acetic anhydride (detected by gas phase).

[0059] b. Add 671 g (6.57 mol, 1.0 eq) of acetic anhydride to the reaction system and continue the reaction at 50° C. for 2 h. At this time, the amount of oxyisophorone in the reaction system is less than 0.5 wt % (detected by gas phase).

[0060] 2 g of sodium acetate was added to neutralize the sulfuric acid, and the reaction system was distilled under reduced pressure at a vacuum degree of 800 Pa and a temperature not exceeding 50° C. Acetic anhydride and acetic acid were recovered until no liquid was discharged. 640 g of a mixed solution of acetic anhydride and acetic acid was recovered, and the purity of the recovered liquid acetic anhydride was 93.7 wt %, and that of acetic acid was 6.3 wt % (detected by gas phase).

[0061] Continue to add 1000 mL of n-heptane to the remaining material, then wash three times with 200 mL of water, recover the n-heptane, and obtain 2,3,5-trimethylhydroquinone diacetate with a purity of 98.7 wt%, a content of 98.5 wt%, and a yield of 97.3%.

[0062] Example 1-2

[0063] In this embodiment, the difference from Example 1 is that the reaction temperature is changed to 60° C., and the following steps are specifically included:

[0064] a. Add 1000 g (6.57 mol, 1.0 eq) of oxyisophorone, 1417 g of 90% acetic anhydride recovery liquid (containing 1275 g of acetic anhydride, 12.48 mol, 1.9 eq) and 1 g (0.1 wt%) of sulfuric acid, heat to 60°C, and react at 50°C for 2 h. At this time, the concentration of acetic anhydride in the reaction system is less than 0.5 wt% (detected by gas phase).

[0065] The reaction system was distilled under reduced pressure with a vacuum degree of 1000 Pa and a temperature not exceeding 50° C. The acetic acid was recovered until no liquid was discharged. A total of 888 g of acetic acid was recovered with a purity of 99.7 wt %, containing 0.3 wt % of acetic anhydride (detected by gas phase).

[0066] b. Add 671 g (6.57 mol, 1.0 eq) of acetic anhydride to the reaction system and continue the reaction at 60° C. for 2 h. At this time, the amount of oxyisophorone in the reaction system is less than 0.5 wt % (detected by gas phase).

[0067] 2 g of sodium acetate was added to neutralize the sulfuric acid, and the reaction system was distilled under reduced pressure with a vacuum degree of 800 Pa and a temperature not exceeding 60° C. Acetic anhydride and acetic acid were recovered until no liquid was discharged. 641 g of a mixed solution of acetic anhydride and acetic acid was recovered, and the purity of the recovered liquid acetic anhydride was 93.5 wt %, and that of acetic acid was 6.5 wt % (detected by gas phase).

[0068] Continue to add 1000 mL of n-heptane to the remaining material, then wash three times with 200 mL of water, recover the n-heptane, and obtain 2,3,5-trimethylhydroquinone diacetate with a purity of 98.6 wt%, a content of 98.6 wt%, and a yield of 97.2%.

[0069] Examples 1-3

[0070] In this embodiment, the difference from Example 1 is that the reaction temperature is changed to 70° C., and the following steps are specifically included:

[0071] a. Add 1000 g (6.57 mol, 1.0 eq) of oxyisophorone, 1417 g of 90% acetic anhydride recovery solution (containing 1275 g of acetic anhydride, 12.48 mol, 1.9 eq) and 1 g (0.1 wt%) of sulfuric acid, heat to 70°C, and react at 50°C for 2 h. At this time, the concentration of acetic anhydride in the reaction system is less than 0.5 wt% (detected by gas phase).

[0072] The reaction system was distilled under reduced pressure with a vacuum degree of 1000 Pa and a temperature not exceeding 70° C. The acetic acid was recovered until no liquid was discharged. A total of 885 g of acetic acid was recovered with a purity of 99.5 wt %, containing 0.5 wt % of acetic anhydride (detected by gas phase).

[0073] b. Add 671 g (6.57 mol, 1.0 eq) of acetic anhydride to the reaction system and continue the reaction at 70° C. for 2 h. At this time, the amount of oxyisophorone in the reaction system is less than 0.5 wt % (detected by gas phase).

[0074] 2 g of sodium acetate was added to neutralize the sulfuric acid, and the reaction system was distilled under reduced pressure at a vacuum degree of 800 Pa and a temperature not exceeding 50° C. Acetic anhydride and acetic acid were recovered until no liquid was discharged. 638 g of a mixed solution of acetic anhydride and acetic acid was recovered, and the purity of the recovered liquid acetic anhydride was 93.8 wt %, and the purity of acetic acid was 6.2 wt % (detected by gas phase).

[0075] Continue to add 1000 mL of n-heptane to the remaining material, then wash three times with 200 mL of water, recover the n-heptane, and obtain 2,3,5-trimethylhydroquinone diacetate with a purity of 98.8 wt%, a content of 98.7 wt%, and a yield of 97.1%.

[0076] Example 2

[0077] A method for preparing 2,3,5-trimethylhydroquinone diacetate, wherein the reaction formula is as follows:

[0078]

[0079] The following steps are involved:

[0080] a. Add 1000 g (6.57 mol, 1.0 eq) of oxyisophorone, 1341 g of 90% acetic anhydride recovery liquid (containing 1207 g of acetic anhydride, 11.82 mol, 1.8 eq) and 1 g (0.1 wt %) of sulfuric acid, heat to 60° C., and react at 60° C. for 2 h. At this time, the concentration of acetic anhydride in the reaction system is less than 0.5 wt % (detected by gas phase).

[0081] The reaction system was distilled under reduced pressure with a vacuum degree of 1000 Pa and a temperature not exceeding 50° C. The acetic acid was recovered until no liquid was discharged. A total of 842 g of acetic acid was recovered with a purity of 99.7 wt %, containing 0.3 wt % of acetic anhydride (detected by gas phase).

[0082] b. Add 939 g (9.20 mol, 1.4 eq) of acetic anhydride to the reaction system and continue the reaction at 60° C. for 2 h. At this time, the amount of oxyisophorone in the reaction system is less than 0.5 wt % (detected by gas phase).

[0083] 2 g of sodium acetate was added to neutralize the sulfuric acid, and the reaction system was distilled under reduced pressure with a vacuum degree of 800 Pa and a temperature not exceeding 50° C. Acetic anhydride and acetic acid were recovered until no liquid was discharged. 880 g of a mixed solution of acetic anhydride and acetic acid was recovered, and the purity of the recovered liquid acetic anhydride was 91.0 wt %, and that of acetic acid was 9.0 wt % (detected by gas phase).

[0084] Continue to add 1000 mL of n-heptane to the remaining material, then wash three times with 200 mL of water, recover the n-heptane, and obtain 2,3,5-trimethylhydroquinone diacetate with a purity of 98.8 wt%, a content of 98.7 wt%, and a yield of 97.0%.

[0085] Example 3

[0086] A method for preparing 2,3,5-trimethylhydroquinone diacetate, wherein the reaction formula is as follows:

[0087]

[0088] The following steps are involved:

[0089] a. Add 1000 g (6.57 mol, 1.0 eq) of oxyisophorone, 1267 g of 90% acetic anhydride recovery solution (containing 1140 g, 11.16 mol, 1.7 eq) and 1 g (0.1 wt%) of sulfuric acid, heat to 70°C, and react at 70°C for 2 h. At this time, the concentration of acetic anhydride in the reaction system is less than 0.5 wt% (detected by gas phase).

[0090] The reaction system was distilled under reduced pressure with a vacuum degree of 1000 Pa and a temperature not exceeding 50° C. The acetic acid was recovered until no liquid was discharged. A total of 796 g of acetic acid was recovered with a purity of 99.9 wt %, containing 0.1 wt % of acetic anhydride (detected by gas phase).

[0091] b. Add 1341 g (13.13 mol, 2.0 eq) of acetic anhydride to the reaction system and continue the reaction at 70° C. for 2 h. At this time, the amount of oxyisophorone in the reaction system is less than 0.5 wt % (detected by gas phase).

[0092] 2 g of sodium acetate was added to neutralize the sulfuric acid, and the reaction system was distilled under reduced pressure at a vacuum degree of 800 Pa and a temperature not exceeding 50° C. Acetic anhydride and acetic acid were recovered until no liquid was discharged. 1255 g of a mixed solution of acetic anhydride and acetic acid was recovered, and the purity of the recovered liquid acetic anhydride was 90.5 wt %, and that of acetic acid was 9.5 wt % (detected by gas phase).

[0093] Continue to add 1000 mL of n-heptane to the remaining material, then wash three times with 200 mL of water, recover the n-heptane, and obtain 2,3,5-trimethylhydroquinone diacetate with a purity of 99.2 wt%, a content of 99.1 wt%, and a yield of 97.2%.

[0094] Example 3-2

[0095] In this embodiment, the difference from Example 3 is that the acetic anhydride used in the first stage is changed to 1.6 eq, and specifically includes the following steps:

[0096] a. Add 1000 g (6.57 mol, 1.0 eq) of oxyisophorone, 1193 g (containing 1073 g, 10.51 mol, 1.6 eq) of 90% acetic anhydride recovery liquid and 1 g (0.1 wt%) of sulfuric acid, heat to 70°C, and react at 70°C for 2 h. At this time, the concentration of acetic anhydride in the reaction system is less than 0.5 wt% (detected by gas phase).

[0097] The reaction system was distilled under reduced pressure with a vacuum degree of 1000 Pa and a temperature not exceeding 50° C. The acetic acid was recovered until no liquid was discharged. A total of 749 g of acetic acid was recovered with a purity of 99.9 wt %, containing 0.05 wt % of acetic anhydride (detected by gas phase).

[0098] b. Add 1341 g (13.13 mol, 2.0 eq) of acetic anhydride to the reaction system and continue the reaction at 70° C. for 2 h. At this time, the amount of oxyisophorone in the reaction system is less than 0.5 wt % (detected by gas phase).

[0099] 2 g of sodium acetate was added to neutralize the sulfuric acid, and the reaction system was distilled under reduced pressure with a vacuum degree of 800 Pa and a temperature not exceeding 50° C. Acetic anhydride and acetic acid were recovered until no liquid was discharged. 1230 g of a mixed solution of acetic anhydride and acetic acid was recovered, and the purity of the recovered liquid acetic anhydride was 87.2 wt %, and that of acetic acid was 12.8 wt % (detected by gas phase).

[0100] Continue to add 1000 mL of n-heptane to the remaining material, then wash three times with 200 mL of water, recover the n-heptane, and obtain 2,3,5-trimethylhydroquinone diacetate with a purity of 99.3 wt%, a content of 99.2 wt%, and a yield of 97.2%.

[0101] Example 4

[0102] A method for preparing 2,3,5-trimethylhydroquinone diacetate, wherein the reaction formula is as follows:

[0103]

[0104] The following steps are involved:

[0105] a. Add 1000 g (6.57 mol, 1.0 eq) of oxoisophorone, 1267 g (containing 1140 g, 11.16 mol, 1.7 eq) of 90% acetic anhydride recovery liquid and 2 g (0.2 wt %) of trifluoromethanesulfonic acid, heat to 70° C., and react at 70° C. for 2 h. At this time, the concentration of acetic anhydride in the reaction system is less than 0.5 wt % (detected by gas phase).

[0106] The reaction system was distilled under reduced pressure with a vacuum degree of 1000 Pa and a temperature not exceeding 50° C. The acetic acid was recovered until no liquid was discharged. A total of 793 g of acetic acid was recovered with a purity of 99.8 wt %, containing 0.2 wt % of acetic anhydride (detected by gas phase).

[0107] b. Add 1341 g (13.13 mol, 2.0 eq) of acetic anhydride to the reaction system and continue the reaction at 70° C. for 2 h. At this time, the amount of oxyisophorone in the reaction system is less than 0.5 wt % (detected by gas phase).

[0108] 2 g of sodium acetate was added to neutralize the sulfuric acid, and the reaction system was distilled under reduced pressure at a vacuum degree of 800 Pa and a temperature not exceeding 50° C. Acetic anhydride and acetic acid were recovered until no liquid was discharged. 1250 g of a mixed solution of acetic anhydride and acetic acid was recovered, and the purity of the recovered liquid acetic anhydride was 90.4 wt %, and that of acetic acid was 9.6 wt % (detected by gas phase).

[0109] Continue to add 1000 mL of n-heptane to the remaining material, then wash three times with 200 mL of water, recover the n-heptane, and obtain 2,3,5-trimethylhydroquinone diacetate with a purity of 99.0 wt%, a content of 99.0 wt%, and a yield of 96.8%.

[0110] Example 5

[0111] A method for preparing 2,3,5-trimethylhydroquinone diacetate, wherein the reaction formula is as follows:

[0112]

[0113] The following steps are involved:

[0114] a. Add 1000 g (6.57 mol, 1.0 eq) of oxyisophorone, 1267 g of 90% acetic anhydride recovery solution (containing 1140 g, 11.16 mol, 1.7 eq) and 2 g (0.2%) of perchloric acid, heat to 70°C, and react at 70°C for 2 h. At this time, the concentration of acetic anhydride in the reaction system is less than 0.5 wt% (detected by gas phase).

[0115] The reaction system was distilled under reduced pressure with a vacuum degree of 1000 Pa and a temperature not exceeding 50° C. The acetic acid was recovered until no liquid was discharged. A total of 795 g of acetic acid was recovered with a purity of 99.8 wt %, containing 0.2 wt % of acetic anhydride (detected by gas phase).

[0116] b. Add 1341 g (13.13 mol, 2.0 eq) of acetic anhydride to the reaction system and continue the reaction at 70° C. for 2 h. At this time, the amount of oxyisophorone in the reaction system is less than 0.5 wt % (detected by gas phase).

[0117] 2 g of sodium acetate was added to neutralize the sulfuric acid, and the reaction system was distilled under reduced pressure at a vacuum degree of 800 Pa and a temperature not exceeding 50° C. Acetic anhydride and acetic acid were recovered until no liquid was discharged. 1251 g of a mixed solution of acetic anhydride and acetic acid was recovered, and the purity of the recovered liquid acetic anhydride was 90.6 wt %, and that of acetic acid was 9.4 wt % (detected by gas phase).

[0118] Continue to add 1000 mL of n-heptane to the remaining material, then wash three times with 200 mL of water, recover the n-heptane, and obtain trimethylhydroquinone diacetate with a purity of 98.9 wt%, a content of 98.8 wt%, and a yield of 97.1%.

[0119] Comparative Example 1

[0120] A method for preparing 2,3,5-trimethylhydroquinone diacetate comprises the following steps:

[0121] Add 1000 g (6.57 mol, 1.0 eq) of oxyisophorone, 1677 g (16.42 mol, 2.5 eq) of acetic anhydride and 1 g (0.1 wt%) of sulfuric acid; raise the temperature to 70°C and react at 70°C for 4 h, at which time the concentration of oxyisophorone in the system is less than 0.5 wt% (detected by gas phase).

[0122] 2 g of sodium acetate was added to neutralize the sulfuric acid, and the reaction system was distilled under reduced pressure at a vacuum degree of 800 Pa and a temperature not exceeding 50° C. Acetic anhydride and acetic acid were recovered until no liquid was discharged. 1110 g of a mixed solution of acetic anhydride and acetic acid was recovered, and the recovered liquid contained 30.0 wt % of acetic anhydride and 70.0 wt % of acetic acid (detected by gas phase).

[0123] Continue to add 1000 mL of n-heptane to the remaining material, then wash it three times with 200 mL of water, recover the n-heptane, and obtain 2,3,5-trimethylhydroquinone diacetate with a purity of 99.2 wt%, a content of 99.1 wt%, and a yield of 97.1%.

[0124] A distillation recovery device was built to separate acetic anhydride and acetic acid, with a column height of 2 m, a reflux ratio of 4:1, and a vacuum degree of 2000 Pa. 700 g of pre-boiling acetic acid was recovered with a purity of 96.0 wt%, containing 4.0 wt% of acetic anhydride; 60 g of cross-phase with a purity of 75.0 wt% of acetic acid, containing 25.0 wt% of acetic anhydride; and the remaining acetic anhydride had a purity of 94.7 wt%.

[0125] The main reaction conditions and product conditions of each embodiment and comparative example are listed in Table 1 below.

[0126] Table 1

[0127]

[0128] In summary, the present invention effectively avoids the distillation of acetic anhydride and acetic acid. In the first stage, less than the equivalent amount of acetic anhydride is added to ensure that the acetic anhydride is fully converted into acetic acid, and the purity of the recovered acetic acid can reach more than 99.5wt%. In the second stage, an excess of acetic anhydride is added to ensure that the raw material is fully converted into acetate, and the purity of the recovered acetic anhydride is greater than 85%, which can be directly applied to the first stage. The present invention makes full use of acetic anhydride, and there is no distillation operation in the whole process, only ordinary distillation is required, the equipment investment is small, the unit consumption is low, and the energy consumption is low.

Claims

1. A method for preparing 2,3,5-trimethylhydroquinone diacetate, characterized in that: It includes the following steps: S1. Under the action of a catalyst, reacting a first raw material to obtain a first product; the first raw material comprises oxyisophorone and acetic anhydride in a molar ratio of 1:X, wherein 1.6≤X≤1.9; S2, separating the acetic acid in the first product to obtain a first crude product; S3, reacting a second raw material; the second raw material includes newly added acetic anhydride and the first crude product; the molar ratio of oxyisophorone in step S1 to the newly added acetic anhydride in step S3 is 1:Y, wherein X+Y≥2.

6.

2. The method for preparing 2,3,5-trimethylhydroquinone diacetate according to claim 1, characterized in that: In step S1, the catalyst is sulfuric acid, trifluoromethanesulfonic acid or perchloric acid; and / or, in step S1, the mass of the catalyst is 0.1wt%-0.2wt% of the mass of the oxyisophorone; And / or, in step S1, the molar ratio of the oxyisophorone to the acetic anhydride is 1:(1.7-1.8), for example, 1:1.7, 1:1.8 or 1:1.

9.

3. The method for preparing 2,3,5-trimethylhydroquinone diacetate according to claim 1, characterized in that: In step S1, the reaction temperature is 40-80°C, preferably 50-70°C, such as 50°C, 60°C or 70°C; And / or, in step S1, the reaction time is 2h; And / or, in step S1, the reaction is carried out until the content of acetic anhydride in the reaction system is below 1 wt %, preferably below 0.5 wt %.

4. The method for preparing 2,3,5-trimethylhydroquinone diacetate according to claim 1, characterized in that: In step S1, the first raw material further includes acetic acid, and the mass of the acetic anhydride is more than 80wt% of the sum of the masses of the acetic anhydride and the acetic acid, preferably more than 85wt%, for example, 90wt%.

5. The method for preparing 2,3,5-trimethylhydroquinone diacetate according to claim 4, characterized in that: The acetic acid and the acetic anhydride are added in the form of a mixture; the mixture is preferably obtained from the previous reaction step S3.

6. The method for preparing 2,3,5-trimethylhydroquinone diacetate according to claim 1, characterized in that: In step S2, the separation method is distillation, preferably reduced pressure distillation; And / or, in step S2, the vacuum degree of the distillation is 1000 Pa; and / or, in step S2, the distillation temperature does not exceed 50°C; And / or, in step S2, the separation completely separates the acetic acid.

7. The method for preparing 2,3,5-trimethylhydroquinone diacetate according to claim 1, characterized in that: In step S3, the reaction temperature is 40-80°C, preferably 50-70°C, such as 50°C, 60°C or 70°C; And / or, in step S3, the reaction time is 2h; And / or, in step S3, the reaction is carried out until the content of the oxyisophorone in the reaction system is below 0.5 wt %, preferably below 0.3 wt %; And / or, the molar ratio of the oxyisophorone in step S1 to the acetic anhydride newly added in step S3 is 1:(1.0-2.0), preferably 1:(1.8-2.0), for example 1:1.0, 1:1.4 or 1:2.

0.

8. The method for preparing 2,3,5-trimethylhydroquinone diacetate according to claim 1, characterized in that: X and Y meet at least one of the following conditions ①-④: ①X+Y≥2.9, for example, X+Y=2.9, 3.2 or 3.7; ②X+0.2Y≥2; ③X+0.15Y≥2; ④X+Y≤3.

9.

9. The method for preparing 2,3,5-trimethylhydroquinone diacetate according to claim 1, characterized in that: In step S3, the reaction is followed by quenching; the quenching method is preferably to add a quencher to the reaction system; the quencher is preferably sodium acetate; the mass of the quencher is preferably twice the mass of the catalyst; And / or, in step S3, after the reaction, distillation is further performed until no acetic anhydride or acetic acid is distilled out to obtain a second crude product; the distillation method is preferably reduced pressure distillation; the vacuum degree of the distillation is preferably 800 Pa; the distillation temperature is preferably not more than 50°C.

10. The method for preparing 2,3,5-trimethylhydroquinone diacetate according to claim 9, characterized in that: The second crude product is further purified to obtain 2,3,5-trimethylhydroquinone diacetate; the purification step preferably comprises: adding n-heptane and then washing with water; the n-heptane is preferably used in an amount of 1000 mL:1000 g to the oxyisophorone in step S1; the amount of water used in the water washing is preferably used in an amount of 200 mL:1000 g to the oxyisophorone in step S1; the number of water washings is preferably three times; Preferably, in step S1, the catalyst is sulfuric acid, and in step S3, after the reaction, a quencher is added to the reaction system for quenching, and the quencher is sodium acetate. After the quenching, distillation is performed until no acetic anhydride or acetic acid is distilled out to obtain a second crude product, and the second crude product is further purified to obtain 2,3,5-trimethylhydroquinone diacetate.

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