A process for purifying 2,3,5-trimethylhydroquinone diacetate foots

Abstract

This application discloses a purification process for 2,3,5-trimethylhydroquinone diacetate (TMHQ-DA) by-products, belonging to the field of 2,3,5-trimethylhydroquinone diacetate purification technology. Using TMHQ-DA by-products as raw materials, the process involves first dissolving them in alcohol, then, under the catalysis of an alkali, allowing TMBC-DA to undergo an ester exchange reaction with ethanol to generate TMBC. After the reaction, the alkali catalyst is recovered, and the filtrate is extracted and recrystallized to obtain TMHQ-DA crystals. This application employs a solid alkali catalytic system, eliminating the need for expensive biological enzymes, shortening the reaction time to several hours, and ensuring the entire system is anhydrous, thus avoiding ester hydrolysis side reactions. Through this method, the TMBC-DA content in the TMHQ-DA by-products is reduced from 30% to below 3% with high purity, achieving resource utilization of the by-products. The ester reaction can be carried out efficiently under mild conditions, requiring no large amounts of solvent, resulting in extremely low losses. The process route is short, equipment requirements are low, significantly reducing industrial costs, and making it suitable for large-scale production.

Description

Technical Field

[0001] This application belongs to the field of 2,3,5-trimethylhydroquinone diacetate purification technology, and in particular relates to a process for purifying 2,3,5-trimethylhydroquinone diacetate by-products. Background Technology

[0002] 2,3,5-Trimethylhydroquinone diacetate (TMHQ-DA) is an important intermediate in the synthesis of vitamin E. Currently, there are some reports on TMHQ-DA synthesis methods in domestic and international literature. Patents CN1420859A and US5955628A use protic acids or Lewis acids to catalyze the reaction of KIP and acetic anhydride to prepare 2,3,5-trimethylhydroquinone diacetate. This method not only uses a large amount of acid, causing significant equipment corrosion, but also has a low yield (66%), with the main byproduct being 3,4,5-trimethylpyrocatechol diacetate (TMBC-DA). Patents CN1102138C and CN1420859A use trifluoromethanesulfonic acid and polyphosphoric acid as catalysts to catalyze the reaction of KIP and acetic anhydride to prepare TMHQ-DA. Patent CN111392390A uses modified cyclodextrin supported on a solid acid catalysis to rearrange and obtain 2... 3,5-Trimethylhydroquinone diester; Patent CN1886361A uses trivalent indium salt as a catalyst to catalyze the reaction of KIP and acetic anhydride to prepare TMHQ-DA, and the yield can be increased to 90%; The methods for synthesizing TMHQ-DA mentioned in the above patents will generate a certain amount of byproduct 3,4,5-trimethylpyrocatechol diester.

[0003] 3,4,5-Trimethylpyrocatechin diester has similar properties to the product and cannot be separated by distillation. It is generally separated by recrystallization. Patent US5969176A mentions a method for separating TMHQ-DA solid, which involves filtering the reaction mixture, mixing the filtrate with ice water, and then filtering at 5 °C to obtain TMHQ-DA solid with a yield of 98%, but a purity of only 94.7% (when the purity is 98.5%, the yield is only 89.7%, and both yield and purity cannot be guaranteed to be high simultaneously). These methods involve cooling the reaction product, requiring the addition of large amounts of solvent, resulting in either low purity or low yield. Furthermore, obtaining sufficient cooling is energy-intensive. EP0916642B1 and its related patents report a method for crystallizing TMHQ-DA in a mixed solvent of acetic acid and water, with a mass ratio of acetic acid to water of 40 / 60-70 / 30, a solution concentration of 10-35 wt%, and a crystallization endpoint temperature of 10-18 °C. At ℃, the product purity can reach 99.9%, but the yield is only about 60%. Another problem is that the solvent consumption is large, the final product yield is low and unstable, and the reproducibility of the experiment is not strong. Although recrystallization can separate most of TMHQ-DA, some product remains in the waste, which is difficult to further purify by extraction, crystallization and other methods.

[0004]

[0005] In the existing process, the separation yield of 2,3,5-trimethylhydroquinone diacetate is low, with the TMHQ-DA content in the by-products being about 47% and the TMBC-DA content being about 30%. It is difficult to further separate TMHQ-DA from the by-products, or the separation cost is high. Summary of the Invention

[0006] The purpose of this application is to provide a purification process for 2,3,5-trimethylhydroquinone diacetate by-products, in order to solve the technical problems in the prior art where the separation yield and purity of 2,3,5-trimethylhydroquinone diacetate cannot be guaranteed at the same time, and the separation cost is high.

[0007] To achieve the above objectives, the technical solution adopted in this application is: to provide a purification process for 2,3,5-trimethylhydroquinone diacetate residue, specifically including the following steps: (i) An alcoholic solution and a catalytic base were added to the 2,3,5-trimethylhydroquinone diacetate residue to carry out an ester exchange reaction, generating a TMBC mixture; (II) Filter the TMBC mixture, recover the catalytic base, add an organic solvent to the filtrate for extraction, and recrystallize to obtain 2,3,5-trimethylhydroquinone diacetate crystals; the reaction route is as follows:

[0008] In one embodiment, Step (I) The alcohol solution is a C1-C10 alcohol; the catalytic base includes a solid catalytic base and a liquid catalytic base. The solid catalytic base is one of DMAP, 2-aminopyridine, 3-aminopyridine, sodium carbonate or sodium bicarbonate, and the liquid catalytic base is one of DBU, triethylamine, diethylamine, ethylenediamine, N-methylimidazolium, morpholine or ammonia water.

[0009] In one embodiment, After the solid catalytic base reaction is completed, it is directly filtered and recovered; after the liquid catalytic base reaction is completed, TMHQ-DA is separated by extraction and crystallization, and the remaining part is separated into liquid base by distillation for reuse in the next batch.

[0010] In one embodiment, In step (I), the 2,3,5-trimethylhydroquinone diacetate residue contains, by mass fraction, 45-48% TMHQ-DA, 30-35% TMBC-DA, and the balance being impurities, including 10% C. 11 H 13 BrO2, trace amounts of C 13 H 16 O4, C 18 H 22 O2, C 12 H 14 O2, C 11 H 14 O2, C 11 H 13 BrO2 is 4-bromo-2,3,6-trimethylphenol acetate or 2-bromo-3,4,5-trimethylphenol acetate.

[0011] In one embodiment, In step (1), the mass ratio of 2,3,5-trimethylhydroquinone diacetate residue to catalytic base is 1:0.1-3, preferably 1:0.7.

[0012] In one embodiment, Step (I) The raw material mass concentration after adding 2,3,5-trimethylhydroquinone diacetate residue to alcohol solution is 5-50 wt%.

[0013] In one embodiment, Step (1) The temperature for the transesterification reaction is 10-100 ℃, and the reaction time is 6-40 h.

[0014] In one embodiment, Step (ii) The organic solvent is one of n-hexane, n-heptane, or cyclohexane.

[0015] In one embodiment, Step (ii) The volume ratio of organic solvent to filtrate is 2-5:1.

[0016] In one embodiment, The purity of 2,3,5-trimethylhydroquinone diacetate crystals is >99%, and the total yield of the separation is >99%.

[0017] This application provides a purification process for 2,3,5-trimethylhydroquinone diacetate (TMHQ-DA) by-products. Using TMHQ-DA by-products as raw materials, the by-products are first dissolved in alcohol to prepare ethanol solutions of varying concentrations. The raw materials are in solid form and anhydrous, as are the added ethanol solutions. The entire reaction system is anhydrous, thus preventing ester hydrolysis. Then, under the catalysis of an alkali, TMHQ-DA undergoes an ester exchange reaction with ethanol to generate 3,4,5-trimethylpyrocatechol monoester (TMBC). After the reaction, the solid alkali catalyst is recovered through simple filtration and reused in the next batch of experiments. The filtrate is extracted with an organic solvent and recrystallized to obtain TMHQ-DA crystals. The reaction mechanism is as follows:

[0018] Ethanol, under the action of a base, loses a hydrogen proton to form the corresponding ethanol oxonium. This oxonium attacks the carbonyl carbon atom of TMBC-DA, subsequently losing one molecule of ethyl acetate to form the corresponding TMBC oxonium. Finally, the TMBC oxonium acquires a hydrogen proton to form TMBC. From a kinetic perspective, ethanol has a pKa value of 15.9, while the pKa values ​​of the two phenolic hydroxyl groups of catechol (the parent structure of TMBC) are 9 and 13, respectively, and the pKa values ​​of the two phenolic hydroxyl groups of hydroquinone (the parent structure of TMHQ) are 9.91 and 11.56, respectively. Therefore, in the transesterification reaction with ethanol, TMBC-DA is more likely to react, losing an ester group to form TMBC.

[0019] Compared with the prior art, this application has the following beneficial effects: Under the catalysis of an alkali, and with strict control of reaction time and temperature, the byproduct TMBC-DA in TMHQ-DA waste is converted into TMBC (conversion rate >90%), while TMHQ-DA in the waste hardly reacts, with a conversion rate <5%. This application is the first to utilize the kinetic difference between TMBC-DA and TMHQ-DA in alkali-catalyzed transesterification to achieve selective conversion, and the first to apply solid alkali-catalyzed transesterification to the removal of TMBC-DA from TMHQ-DA waste. This application uses a solid alkali catalytic system, eliminating the need for expensive biological enzymes, shortening the reaction time to several hours, and the entire system is anhydrous, avoiding the occurrence of ester hydrolysis side reactions. Through this method, the TMBC-DA content in TMHQ-DA waste is reduced from 30% to below 3%, realizing the resource utilization of byproducts. When the TMBC-DA content in the waste is <10%, it can be removed by simple extraction, followed by crystallization to recover TMHQ-DA. The yield of TMHQ-DA synthesized in the prior art is about 98%, and recrystallization can yield 93%. The original TMHQ-DA solid content was 5%, with a 5% product loss in the by-product. This application can reduce the content of the main by-product TMBC-DA in the by-product, recover TMHQ-DA through extraction and separation, and recrystallize it in a suitable solvent to separate more than 90% of TMHQ-DA from the by-product again, with a TMHQ-DA crystal purity of more than 99.2% and an overall separation yield of 99%. The transesterification reaction can be carried out efficiently under mild conditions (normal pressure and moderate temperature). The purification process does not require the use of a large amount of solvent or the increase in energy consumption by lowering the temperature. The solid base catalyst can be recycled with extremely low loss, reducing the cost of catalyst use and the burden of solid waste treatment. The process route is short and the equipment requirements are low, which significantly reduces industrial costs and is suitable for large-scale production. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The above are gas phase characterization diagrams of the waste materials used in the examples; Figure 2 This is a gas phase characterization diagram of the TMBC mixture in Example 1; Figure 3 The purity content characterization diagram of the TMHQ-DA crystals separated in Example 7 is shown. Figure 4 The purity content characterization diagram of the TMHQ-DA crystals separated in Example 9 is shown. Figure 5 This is a characterization diagram of the purity of the TMHQ-DA crystals separated in Example 14. Detailed Implementation

[0022] To make the technical problems to be solved, the technical solutions, and the beneficial effects of this application clearer, this application will be further described in detail. It should be understood that the specific embodiments described herein are only for explaining this application and are not intended to limit this application.

[0023] Example 1 A purification process for 2,3,5-trimethylhydroquinone diacetate residue specifically includes the following steps: (a) such as Figure 1 As shown, the initial content of TMBC-DA in the 2,3,5-trimethylhydroquinone diacetate residue was 30.36%, and the initial content of TMHQ-DA was 45.8%. 10 g of 2,3,5-trimethylhydroquinone diacetate residue was added to anhydrous ethanol to prepare a 15 wt% solution. 7 g of sodium bicarbonate was added to the solution, and the transesterification reaction was carried out at 60 °C for 10 h to generate a TMBC mixture. Figure 2 As shown, the TMBC mixture was analyzed by gas chromatography, and the content of TMHQ-DA was 44.63% and the content of TMBC-DA was 5.47%. (ii) Filter the TMBC mixture and directly recover sodium bicarbonate. The recovered sodium bicarbonate is recycled for the next batch of purification. The solvent in the filtrate is removed by rotary evaporation. Hexane (4 times the volume of the filtrate) is added and extracted 5 times. The 2,3,5-trimethylhydroquinone diacetate crystals are recovered by recrystallization with a purity of 99.5%. The TMHQ-DA recovery rate in the by-product is 89.4%, and the total separation yield is 99.1%.

[0024] Example 2 The difference between this embodiment and Example 1 is that sodium bicarbonate is replaced with N-methylimidazole, which is a liquid alkali. After the reaction, TMHQ-DA is separated by extraction crystallization, and the remaining part is separated by distillation to obtain liquid alkali for reuse in the next batch. The rest of the operation is the same. After the reaction, the content of TMHQ-DA is 44.34%, the content of TMBC-DA is 5.97%, the purity of TMHQ-DA crystals is 99.4%, the recovery rate of TMHQ-DA in the waste is 88.7%, and the total separation yield is 99%.

[0025] Example 3 The difference between this embodiment and Example 1 is that sodium bicarbonate is replaced with DMAP, while the rest of the operation is the same. After the reaction, the content of TMHQ-DA is 45.37%, the content of TMBC-DA is 3.21%, the purity of TMHQ-DA crystals is 99.5%, the recovery rate of TMHQ-DA in the waste is 90.9%, and the total separation yield is 99.1%.

[0026] Example 4 The difference between this embodiment and Example 2 is that N-methylimidazole was replaced with triethylamine. The rest of the operation was the same. After the reaction, the content of TMHQ-DA was 39.35%, the content of TMBC-DA was 5.36%, the purity of TMHQ-DA crystals was 99.4%, the recovery rate of TMHQ-DA in the waste was 78.7%, and the total separation yield was 98.6%.

[0027] Example 5 The difference between this embodiment and Example 1 is that the temperature of the transesterification reaction was adjusted to 40 °C and the reaction time was adjusted to 24 h. The other operations were the same. After the reaction, the content of TMHQ-DA was 43.47%, the content of TMBC-DA was 9.46%, the purity of TMHQ-DA crystals was 99.1%, the recovery rate of TMHQ-DA in the waste was 86.7%, and the total separation yield was 99.0%.

[0028] Example 6 The difference between this embodiment and Example 1 is that the temperature of the transesterification reaction was adjusted to 80 °C and the reaction time was adjusted to 6 h. The other operations were the same. After the reaction, the content of TMHQ-DA was 39.77%, the content of TMBC-DA was 5.08%, the purity of TMHQ-DA crystals was 99.5%, the recovery rate of TMHQ-DA in the waste was 79.6%, and the total separation yield was 98.7%.

[0029] Example 7 The difference between this embodiment and Example 2 is that N-methylimidazole was replaced with DBU; all other operations were the same. After the reaction, the TMHQ-DA content was 32.62%, and the TMBC-DA content was 0.58%. Figure 3 As shown, the TMHQ-DA crystal purity is 99.8%, the TMHQ-DA recovery rate in the waste is 65.5%, and the total separation yield is 98.0%.

[0030] Example 8 The difference between this embodiment and Example 1 is that sodium bicarbonate is replaced with 2-aminopyridine. The rest of the operation is the same. After the reaction, the content of TMHQ-DA is 34.09%, the content of TMBC-DA is 3.5%, the crystal purity of TMHQ-DA is 99.5%, the recovery rate of TMHQ-DA in the waste is 68.3%, and the total separation yield is 98.1%.

[0031] Example 9 The difference between this embodiment and Example 1 is that sodium bicarbonate is replaced with 3-aminopyridine; the rest of the operations are the same. After the reaction, the TMHQ-DA content is 40.14%, and the TMBC-DA content is 7.13%. Figure 4 As shown, the TMHQ-DA crystal purity is 99.2%, the TMHQ-DA recovery rate in the waste is 80.1%, and the total separation yield is 98.7%.

[0032] Example 10 The difference between this embodiment and Example 2 is that N-methylimidazolium is replaced with morpholine, while the rest of the operation is the same. After the reaction, the content of TMHQ-DA is 33.23%, the content of TMBC-DA is 2.24%, the crystal purity of TMHQ-DA is 99.6%, the recovery rate of TMHQ-DA in the waste is 66.6%, and the total separation yield is 98.0%.

[0033] Example 11 The difference between this embodiment and Example 2 is that N-methylimidazole was replaced with ammonia. The rest of the operation is the same. After the reaction, the content of TMHQ-DA was 38.63%, the content of TMBC-DA was 3.55%, the purity of TMHQ-DA crystals was 99.5%, the recovery rate of TMHQ-DA in the waste was 77.4%, and the total separation yield was 98.5%.

[0034] Example 12 The difference between this embodiment and Example 1 is that sodium bicarbonate is replaced with sodium carbonate, while the rest of the operation is the same. After the reaction, the content of TMHQ-DA is 36.87%, the content of TMBC-DA is 3.51%, the crystal purity of TMHQ-DA is 99.5%, the recovery rate of TMHQ-DA in the waste is 73.8%, and the total separation yield is 98.4%.

[0035] Example 13 The difference between this embodiment and Example 1 is that the mass ratio of 2,3,5-trimethylhydroquinone diacetate residue to sodium bicarbonate is 1:0.1. The other operations are the same. After the reaction, the content of TMHQ-DA is 43.69%, the content of TMBC-DA is 9.12%, the crystal purity of TMHQ-DA is 99.1%, the recovery rate of TMHQ-DA in the residue is 87.1%, and the total separation yield is 99.0%.

[0036] Example 14 The difference between this embodiment and Example 1 is that the mass ratio of 2,3,5-trimethylhydroquinone diacetate residue to sodium bicarbonate is 1:3. All other operations are the same. After the reaction, the TMHQ-DA content is 38.56%, and the TMBC-DA content is 1.89%. Figure 5 As shown, the TMHQ-DA crystal purity is 99.7%, the TMHQ-DA recovery rate in the waste is 77.4%, and the total separation yield is 98.5%.

[0037] Example 15 The difference between this embodiment and Example 1 is that the 2,3,5-trimethylhydroquinone diacetate residue was prepared into a 10 wt% solution after being added to anhydrous ethanol. The rest of the operation was the same. After the reaction, the TMHQ-DA content was 45.78%, the TMBC-DA content was 7.44%, the TMHQ-DA crystal purity was 99.1%, the TMHQ-DA recovery rate in the residue was 91.3%, and the total separation yield was 99.1%.

[0038] Example 16 The difference between this embodiment and Example 1 is that the 2,3,5-trimethylhydroquinone diacetate residue was prepared into a 50 wt% solution after being added to anhydrous ethanol. The rest of the operation was the same. After the reaction, the TMHQ-DA content was 42.98%, the TMBC-DA content was 3.42%, the TMHQ-DA crystal purity was 99.5%, the TMHQ-DA recovery rate in the residue was 86.1%, and the total separation yield was 98.9%.

[0039] Example 17 The difference between this embodiment and Example 1 is that the 2,3,5-trimethylhydroquinone diacetate residue was prepared into a 30 wt% solution after being added to anhydrous ethanol. The rest of the operation was the same. After the reaction, the TMHQ-DA content was 43.58%, the TMBC-DA content was 4.78%, the TMHQ-DA crystal purity was 99.4%, the TMHQ-DA recovery rate in the residue was 87.2%, and the total separation yield was 99.0%.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is that the temperature of the transesterification reaction was adjusted to 110 °C, while the rest of the operation was the same. After the reaction, the content of TMHQ-DA was 7.24%, the content of TMBC-DA was 0.01%, the purity of TMHQ-DA crystals was 99.8%, the recovery rate of TMHQ-DA in the waste was 14.5%, and the total separation yield was 95.6%.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that the temperature of the transesterification reaction was adjusted to 0 °C, while the rest of the operation was the same. After the reaction, the content of TMHQ-DA was 43.66%, the content of TMBC-DA was 18.34%, the crystal purity of TMHQ-DA was 45.2%, the recovery rate of TMHQ-DA in the waste was 39.7%, and the total separation yield was 96.8%.

[0042] Comparative Example 3 The difference between this comparative example and Example 1 is that the molar ratio of 2,3,5-trimethylhydroquinone diacetate residue to sodium bicarbonate is 1:4. The other operations are the same. After the reaction, the content of TMHQ-DA is 20.31%, the content of TMBC-DA is 0.08%, the crystal purity of TMHQ-DA is 99.7%, the recovery rate of TMHQ-DA in the residue is 40.8%, and the total separation yield is 96.8%.

[0043] Comparative Example 4 The difference between this comparative example and Example 1 is that the raw material concentration was changed to 70 wt%, while the rest of the operation was the same. After the reaction, the TMHQ-DA content was 28.35%, the TMBC-DA content was 1.62%, the TMHQ-DA crystal purity was 99.6%, the TMHQ-DA recovery rate in the waste was 56.8%, and the total separation yield was 97.6%.

[0044] Comparative Example 5 The difference between this comparative example and Example 1 is that the volume ratio of n-hexane to filtrate is 0.5:1. The other operations are the same. After the reaction, the content of TMHQ-DA is 44.63%, the content of TMBC-DA is 5.47%, the crystal purity of TMHQ-DA is 85.6%, the recovery rate of TMHQ-DA in the by-product is 62.0%, and the total separation yield is 97.8%.

[0045] The separation results from Example 1 and Comparative Examples 1-5 show that the yield and purity of TMHQ-DA obtained under the conditions of Example 1 are both above 99%, while the separation effect outside the screening conditions of this application is not ideal.

[0046] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A purification process for 2,3,5-trimethylhydroquinone diacetate by-products, characterized in that, Specifically, the following steps are included: (i) An alcoholic solution and a catalytic base were added to the 2,3,5-trimethylhydroquinone diacetate residue to carry out an ester exchange reaction, generating a TMBC mixture; (ii) Filter the TMBC mixture, recover the catalytic base, add an organic solvent to the filtrate for extraction, recrystallize to obtain 2,3,5-trimethylhydroquinone diacetate crystals.

2. The purification process for 2,3,5-trimethylhydroquinone diacetate by-products according to claim 1, characterized in that, The alcohol solution in step (a) is a C1-C10 alcohol; the catalytic base includes a solid catalytic base and a liquid catalytic base, wherein the solid catalytic base is one of DMAP, 2-aminopyridine, 3-aminopyridine, sodium carbonate or sodium bicarbonate, and the liquid catalytic base is one of DBU, triethylamine, diethylamine, ethylenediamine, N-methylimidazolium, morpholine or ammonia water.

3. The purification process for 2,3,5-trimethylhydroquinone diacetate by-products according to claim 2, characterized in that, After the solid catalytic base reaction is completed, it is directly filtered and recovered; after the liquid catalytic base reaction is completed, TMHQ-DA is first separated by extraction and crystallization, and the remaining part is separated into liquid base by distillation for reuse in the next batch.

4. The purification process for 2,3,5-trimethylhydroquinone diacetate by-products according to claim 1, characterized in that, The 2,3,5-trimethylhydroquinone diacetate residue in step (I) contains, by mass fraction, 45-48% TMHQ-DA, 30-35% TMBC-DA, and the remainder is impurities.

5. The purification process for 2,3,5-trimethylhydroquinone diacetate by-products according to claim 1, characterized in that, In step (i), the mass ratio of 2,3,5-trimethylhydroquinone diacetate residue to catalytic base is 1:0.1-3.

6. The purification process for 2,3,5-trimethylhydroquinone diacetate by-products according to claim 1, characterized in that, The raw material mass concentration after adding the 2,3,5-trimethylhydroquinone diacetate residue to the alcohol solution in step (1) is 5-50 wt%.

7. The purification process for 2,3,5-trimethylhydroquinone diacetate by-products according to claim 1, characterized in that, The temperature of the transesterification reaction in step (i) is 10-100 °C, and the reaction time is 6-40 h.

8. The purification process for 2,3,5-trimethylhydroquinone diacetate by-products according to claim 1, characterized in that, The organic solvent mentioned in step (ii) is one of n-hexane, n-heptane, or cyclohexane.

9. The purification process for 2,3,5-trimethylhydroquinone diacetate by-products according to claim 1, characterized in that, The volume ratio of the organic solvent to the filtrate in step (ii) is 2-5:

1.

10. The purification process for 2,3,5-trimethylhydroquinone diacetate by-products according to claim 1, characterized in that, The purity of the 2,3,5-trimethylhydroquinone diacetate crystals is >99%, and the total yield of the separation is >99%.

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