Process for the preparation of trimethylbenzoquinone

Abstract

The application relates to the technical field of organic synthesis, and discloses a preparation method of trimethylbenzoquinone, which comprises the following steps: mixing a to-be-reacted solution containing trimethylbenzene and an organic solvent with a ligand catalyst, and carrying out an oxidation reaction with an oxidizing agent to obtain trimethylbenzoquinone; wherein the ligand catalyst comprises methyltrioxorhenium and a non-metallic ligand, and the non-metallic ligand is a compound containing at least two C=N structures. The method has the advantages of low oxidizing agent consumption, high reactant conversion rate and high yield of the product trimethylbenzoquinone.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and specifically to a method for preparing trimethylbenzoquinone. Background Technology

[0002] Trimethylbenzoquinone is an important pharmaceutical intermediate. For example, 2,3,5-trimethylhydroquinone, synthesized by hydrogenation of 2,3,5-trimethylbenzoquinone, is an important intermediate in the synthesis of vitamin E. Artificially synthesized vitamin E currently dominates the market.

[0003] Currently, the main method for synthesizing trimethylbenzoquinone involves using m-cresol as a raw material, alkylating it to produce trimethylphenol, and then oxidizing it to obtain trimethylbenzoquinone. This process has a high yield, but it involves many steps, and the raw material m-cresol is expensive.

[0004] Existing technologies also include methods for preparing trimethylbenzoquinone using pseudotrimethylbenzene as a raw material. CN106565423A discloses a method for obtaining trimethylbenzoquinone from pseudotrimethylbenzene via bromination-oxidation-reduction. CN109836310A discloses a method for obtaining trimethylbenzoquinone from pseudotrimethylbenzene using iron halide catalyst catalytic oxidation. CN108084006A discloses a method for obtaining trimethylbenzoquinone from pseudotetramethylbenzene via sulfonation, alkali fusion, and oxidation; however, the reaction process is complex and the conditions are difficult to control.

[0005] While the above methods can reduce raw material costs, they generally still suffer from low raw material conversion rates and yields. Therefore, a preparation method that can improve the yield and conversion rate of trimethylbenzoquinone is needed. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of low raw material conversion rate and low product yield in the preparation of trimethylbenzoquinone in the prior art, and to provide a method for preparing trimethylbenzoquinone that consumes less oxidant and has a high reactant conversion rate and a high yield of trimethylbenzoquinone.

[0007] To achieve the above objectives, the present invention provides a method for preparing trimethylbenzoquinone, wherein the method includes the following steps:

[0008] The reaction solution containing parabens and organic solvents is mixed with a ligand catalyst and then subjected to an oxidation reaction with an oxidant to obtain trimethylbenzoquinone.

[0009] The ligand catalyst comprises methyl rhenium trioxide and non-metallic ligands, wherein the non-metallic ligands are compounds containing at least two C=N structures.

[0010] Preferably, the molar ratio of methyl rhenium trioxide to nonmetallic ligands in the ligand catalyst is 0.5-4:1, more preferably 0.8-1.2:1.

[0011] Preferably, the nonmetallic ligand has the structure shown in Formula I;

[0012]

[0013] Wherein, R1 is p-chlorophenyl, p-fluorophenyl, p-carboxyphenyl, or p-hydroxyphenyl;

[0014] R2 and R3 are each independently hydrocarbon groups containing 1-6 carbon atoms.

[0015] Preferably, the R2 and R3 bonds form a ring.

[0016] Preferably, the nonmetallic ligand has the structure shown in Formula II;

[0017]

[0018] R1 is p-chlorophenyl, p-fluorophenyl, p-carboxyphenyl, or p-hydroxyphenyl.

[0019] Preferably, the amount of the ligand catalyst used is 0.5-10 wt% of the amount of pseudotrimethylbenzene used, and more preferably 2.5-5 wt%.

[0020] Preferably, the mass ratio of the organic solvent to pseudotrimethylbenzene is 5-100:1, more preferably 8-20:1.

[0021] Preferably, the organic solvent is selected from at least one of fatty alcohols, fatty acids, organic acid anhydrides, halogenated organic acids and halogenated hydrocarbons, and more preferably from at least one of methanol, ethanol, formic acid, acetic acid, trifluoroacetic acid and acetic anhydride.

[0022] Preferably, the molar ratio of the oxidant to pseudotrimethylbenzene is 0.5-8:1, and more preferably 2.5-5:1.

[0023] Preferably, the oxidant is hydrogen peroxide.

[0024] Preferably, the oxidant is added in the form of an oxidant solution, and the mass concentration of the oxidant in the oxidant solution is 15-50 wt%.

[0025] Preferably, the conditions for the oxidation reaction include: a reaction temperature of 20-90℃, more preferably 30-85℃, and more preferably 45-80℃; and a reaction time of 0.1-36h, more preferably 1-12h, and more preferably 2-6h.

[0026] The beneficial effects achieved through the above technical solution are as follows:

[0027] The preparation method provided by this invention uses pseudotrimethylbenzene as raw material and a ligand catalyst formed by methylrhenium trioxide and non-metallic ligands as catalyst to carry out a catalytic oxidation reaction in the presence of an oxidant to obtain trimethylbenzoquinone, thereby improving the conversion rate of raw materials and the yield of reaction products. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the reaction pathway for the catalytic oxidation of trimethylbenzoquinone;

[0029] Figure 2 This is a schematic diagram of a methyl rhenium trioxide and nonmetallic ligand-forming catalyst;

[0030] Figure 3 This is a mass spectrometry analysis of the reaction product of Example 1 and the trimethylbenzoquinone standard. Detailed Implementation

[0031] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0032] This invention discloses a method for preparing trimethylbenzoquinone, wherein the method includes the following steps:

[0033] The reaction solution containing parabens and organic solvents is mixed with a ligand catalyst and then subjected to an oxidation reaction with an oxidant to obtain trimethylbenzoquinone.

[0034] The ligand catalyst comprises methyl rhenium trioxide and non-metallic ligands, wherein the non-metallic ligands are compounds containing at least two C=N structures.

[0035] In this invention, the preparation method uses pseudotrimethylbenzene as raw material and a ligand catalyst formed by methylrhenium trioxide and non-metallic ligands as catalyst to carry out a catalytic oxidation reaction in the presence of an oxidant to obtain trimethylbenzoquinone. The preparation method has simple steps and improves the conversion rate of raw materials and the yield of reaction products.

[0036] According to the present invention, preferably, the molar ratio of methyl rhenium trioxide to nonmetallic ligands in the ligand catalyst is 0.5-4:1, for example 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.8:1, 2:1, 2.4:1, 2.8:1, 3.2:1, 3.6:1, 4:1, or any range between the two, preferably 0.8-1.2:1.

[0037] In this invention, preferably, the non-metallic ligand contains at least two C=N structures, and its empty orbitals form a ligand catalyst with methylrhenium trioxide in the aforementioned molar ratio. This helps to increase the reaction rate with the oxidant, improve the conversion rate of the feedstock parabens, and increase the yield of the product trimethylbenzoquinone. Excessive use of methylrhenium trioxide prevents it from effectively binding with the non-metallic ligand, thus failing to achieve optimal catalytic effect; conversely, insufficient use results in inadequate catalytic performance.

[0038] According to the present invention, preferably, the nonmetallic ligand has the structure shown in Formula I;

[0039]

[0040] R1 is p-chlorophenyl, p-fluorophenyl, p-carboxyphenyl, or p-hydroxyphenyl.

[0041] R2 and R3 are each independently hydrocarbon groups containing 1-6 carbon atoms.

[0042] In this invention, the hydrocarbon group containing 1-6 carbon atoms can be a saturated hydrocarbon group or an unsaturated hydrocarbon group. The saturated hydrocarbon group is an alkyl group containing 1-6 carbon atoms, which can be a straight-chain alkyl group or a branched-chain alkyl group, preferably a straight-chain alkyl group. Specifically, examples include: methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, n-hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl, and 1-ethyl-2-methylpropyl, etc.

[0043] In this invention, the unsaturated hydrocarbon group is an alkenyl or alkynyl group containing 2-6 carbon atoms, specifically, for example, vinyl, propenyl, allyl, isopropenyl, n-butenyl, isobutenyl, n-pentenyl, isopentenyl, n-hexenyl, ethynyl, propynyl, propynyl, butynyl, pentylyl, and hexynyl.

[0044] In this invention, R2 and R3 are each independently a hydrocarbon group containing 1-3 carbon atoms, specifically, for example, methyl, ethyl, n-propyl, vinyl, propenyl, or allyl. R2 and R3 can be the same or different. According to a preferred embodiment of the invention, at least one of R2 and R3 is an unsaturated hydrocarbon group.

[0045] According to the present invention, preferably, the R2 and R3 bonds form a ring. In the present invention, R2 and R3 form a heterocyclic structure with the C=N bond in Formula I, which helps methylrhenium trioxide to abstract oxygen from the oxidant, form a peroxide, and then oxidize the reactants, thereby accelerating the oxidation reaction and increasing the conversion rate of the reactants.

[0046] According to the present invention, preferably, the nonmetallic ligand has the structure shown in Formula II;

[0047]

[0048] R1 is p-chlorophenyl, p-fluorophenyl, p-carboxyphenyl, or p-hydroxyphenyl.

[0049] In this invention, there is no particular limitation on the method of adding the ligand catalyst. The methyl rhenium trioxide and non-metallic ligands of the ligand catalyst can be added together with the solution to be reacted, or the ligand catalyst can be prepared by first preparing the methyl rhenium trioxide and non-metallic ligands and then mixed with the solution to be reacted. Preferably, the ligand catalyst is prepared by first preparing the methyl rhenium trioxide and non-metallic ligands and then mixed with the solution to be reacted.

[0050] In this invention, the preparation method of the ligand catalyst is not particularly limited. According to a preferred embodiment of the invention, according to... Figure 2 The process shown forms the ligand catalyst, and the preparation method of the ligand catalyst includes: mixing methyl rhenium trioxide and non-metallic ligands uniformly at room temperature to obtain the ligand catalyst.

[0051] In this invention, the mixing method is not particularly limited, and those skilled in the art can choose conventional mixing methods, such as stirring.

[0052] According to the present invention, the amount of the ligand catalyst used is not particularly limited, and those skilled in the art can adjust the amount of the ligand catalyst according to the amount of pseudotrimethylbenzene used. Preferably, the amount of the ligand catalyst used is 0.5-10 wt% of the amount of pseudotrimethylbenzene used, for example, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any range between the two, preferably 2.5-5 wt%.

[0053] In this invention, if the amount of ligand catalyst used is too small, the catalytic effect is limited; if the amount of ligand catalyst used is too large, it will result in a waste of catalyst resources and increase the recovery cost.

[0054] According to the present invention, preferably, the mass ratio of the organic solvent to pseudotrimethylbenzene is 5-100:1, for example 5:1, 8:1, 10:1, 12:1, 15:1, 18:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, or any range between the two, preferably 8-20:1.

[0055] According to the present invention, the type of organic solvent is not particularly limited and is a conventional organic solvent in the art. Preferably, the organic solvent is selected from at least one of fatty alcohols, fatty acids, organic acid anhydrides, and halogenated hydrocarbons. The fatty alcohol is a C1-C4 alcohol, such as methanol, ethanol, n-propanol, isobutanol, tert-butanol, etc. The fatty acid is a C1-C3 carboxylic acid, such as formic acid, acetic acid, propionic acid, etc. The organic acid anhydride is an acid anhydride compound containing carbon, such as acetic anhydride, phthalic anhydride, etc. The halogenated hydrocarbon is a compound in which hydrogen atoms in a hydrocarbon molecule are replaced by halogen atoms, and the hydrocarbon molecule is a C1-C3 alkane, such as chloroform, dichloroethane, etc.

[0056] According to the present invention, preferably, the organic solvent is selected from at least one of methanol, ethanol, formic acid, acetic acid, trifluoroacetic acid and acetic anhydride.

[0057] In this invention, the aforementioned organic solvent effectively dissolves the raw material pseudotrimethylbenzene and enhances the catalytic reaction of the ligand catalyst, thereby effectively improving the product yield. Excessive addition of organic solvent will reduce the oxidant concentration, affecting the product yield and increasing solvent recovery costs, while insufficient addition will prevent the raw material from dissolving in the same phase.

[0058] In this invention, the preparation method of the reaction solution is not particularly limited. According to a preferred embodiment of the invention, pseudotrimethylbenzene is mixed with an organic solvent and stirred to dissolve. The stirring rate is not particularly limited, as long as a homogeneous reaction solution is obtained.

[0059] According to a preferred embodiment of the present invention, the reaction solution is mixed with a ligand catalyst, heated to the oxidation reaction temperature, and an oxidant is slowly added to carry out the oxidation reaction.

[0060] According to the present invention, preferably, the molar ratio of the oxidant to pseudotrimethylbenzene is 0.5-8:1, for example 0.5:1, 1:1, 1.2:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.2:1, 4.5:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or any range between the two, preferably 2.5-5:1.

[0061] According to the present invention, the type and source of the oxidant are not particularly limited, and it can be any compound conventionally used in the art that can act as an oxidant to achieve an oxidizing effect in oxidation reactions. Preferably, the oxidant is hydrogen peroxide and / or an oxygen-containing gas, with hydrogen peroxide being more preferred. The oxygen-containing gas is preferably oxygen.

[0062] According to the present invention, preferably, the oxidant is added in the form of an oxidant solution, wherein the mass concentration of the oxidant in the oxidant solution is 15-50 wt%, preferably 20-40 wt%. In the present invention, introducing the oxidant in the form of an oxidant solution helps the oxidant to fully contact with p-xylene, resulting in a milder reaction.

[0063] In this invention, the rate at which the oxidant is added is not particularly limited. Slowly adding the oxidant and mixing it evenly with the reaction solution and catalyst, followed by thorough stirring to carry out the oxidation reaction, can improve the yield of the product trimethylbenzoquinone.

[0064] According to a preferred embodiment of the present invention, based on 1g of pseudotrimethylbenzene, the addition rate of the oxidant is 0.1-3g / h, for example 0.1g / h, 0.2g / h, 0.3g / h, 0.5g / h, 0.6g / h, 0.8g / h, 1g / h, 1.2g / h, 1.4g / h, 1.5g / h, 1.6g / h, 1.8g / h, 2g / h, 2.2g / h, 2.4g / h, 2.5g / h, 2.6g / h, 2.8g / h, 3g / h, or any range between the two, preferably 0.5-2g / h.

[0065] According to the present invention, preferably, the conditions for the oxidation reaction include: a reaction temperature of 20-90°C, for example 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or any range between the two, preferably 30-85°C, more preferably 45-80°C; and a reaction time of 0.1-36h, for example 0.1h, 0.5h, 1h, 2h, 3h, 4h, 6h, 8h, 10h, 12h, 16h, 20h, 24h, 28h, 32h, 36h, or any range between the two, preferably 1-12h, more preferably 2-6h.

[0066] In this invention, the equipment used to carry out the oxidation reaction is not particularly limited, as long as it can achieve the oxidation reaction. Preferably, the oxidation reaction is carried out in a reactor.

[0067] In this invention, the oxidation reaction is carried out according to... Figure 1 The reaction proceeds along the indicated path, with parabens and an oxidant undergoing an oxidation reaction. The reaction steps are simple, the amount of oxidant consumed is small, and the yield of the product trimethylbenzoquinone is high.

[0068] In this invention, preferably, the method further includes: after the oxidation reaction is completed, the oxidation reaction product is washed with water and then separated into phases, and the organic phase is distilled to remove light and heavy components to obtain trimethylbenzoquinone.

[0069] According to a particularly preferred embodiment of the present invention, a method for preparing trimethylbenzoquinone includes the following steps:

[0070] The reaction solution containing parabens and organic solvents is mixed with a ligand catalyst and then subjected to an oxidation reaction with an oxidant to obtain trimethylbenzoquinone.

[0071] The ligand catalyst comprises methyl rhenium trioxide and a non-metallic ligand, wherein the non-metallic ligand is a compound containing at least two C=N structures;

[0072] The molar ratio of methyl rhenium trioxide to nonmetallic ligands in the ligand catalyst is 0.8-1.2:1;

[0073] The nonmetallic ligand has the structure shown in Formula II;

[0074]

[0075] Wherein, R1 is p-chlorophenyl, p-fluorophenyl, p-carboxyphenyl, or p-hydroxyphenyl;

[0076] The amount of the ligand catalyst used is 2.5-5 wt% of the amount of pseudotrimethylbenzene used.

[0077] The present invention will be described in detail below through examples and comparative examples. Unless otherwise specified, all reagents used in the following examples and comparative examples are commercially available.

[0078] Catalyst A Preparation Example

[0079] Catalyst A, as shown in Formula IV, is obtained by mixing methyl rhenium trioxide and the non-metallic ligand shown in Formula III at a molar ratio of 1:1 at room temperature.

[0080]

[0081] Catalyst B Preparation Example

[0082] Catalyst B, as shown in Formula VI, is obtained by mixing methyl rhenium trioxide and the non-metallic ligand shown in Formula V at a molar ratio of 1:1.1 at room temperature.

[0083]

[0084] Catalyst C Preparation Example

[0085] Catalyst C, as shown in Formula VIII, is obtained by mixing methyl rhenium trioxide and the non-metallic ligand shown in Formula VII at a molar ratio of 1:1 at room temperature.

[0086]

[0087] Catalyst D Preparation Example

[0088] Catalyst D, as shown in Formula X, is obtained by mixing methyl rhenium trioxide and the non-metallic ligand shown in Formula IX at a molar ratio of 1:1 at room temperature.

[0089]

[0090] Catalyst E Preparation Example

[0091] Catalyst E is obtained by mixing methyl rhenium trioxide and the non-metallic ligand shown in Formula III at a molar ratio of 3:1 at room temperature.

[0092] Example 1

[0093] (1) Add 2.4g of pseudotrimethylbenzene and 23.7g of formic acid to the reactor and wait for them to be fully mixed and dissolved.

[0094] (2) Add 0.116g of catalyst A to the reactor; control the temperature at 70℃ and keep stirring.

[0095] (3) Prepare hydrogen peroxide solution with a concentration of 30 wt% and add it dropwise to the reactor at a rate of 10.1 g for 1 hour. After the addition is complete, continue to maintain the temperature and stir thoroughly for 4 hours to obtain a product containing trimethylbenzoquinone.

[0096] Figure 3 The mass spectra of the reaction products and the trimethylbenzoquinone standard are shown below. Figure 3 It can be seen that the spectrum of the product obtained in this embodiment is similar to that of the trimethylbenzoquinone standard. Figure 1 The results confirmed that the product obtained from the reaction was trimethylbenzoquinone.

[0097] Example 2

[0098] (1) Add 2.4g of pseudotrimethylbenzene and 35.1g of acetic anhydride to the reactor and wait for them to be fully mixed and dissolved.

[0099] (2) Add 0.09g of catalyst B to the reactor; control the temperature at 60℃ and keep stirring.

[0100] (3) Prepare hydrogen peroxide solution with a concentration of 30 wt% and add it dropwise to the reactor at a rate of 6.3 g for 1 hour. After the addition is complete, continue to maintain the temperature and stir thoroughly for 5 hours to obtain a product containing trimethylbenzoquinone.

[0101] Example 3

[0102] (1) Add 2.4g of pseudotrimethylbenzene and 42.7g of trifluoroacetic acid to the reactor and wait for them to be fully mixed and dissolved.

[0103] (2) Add 0.071g of catalyst C to the reactor; control the temperature at 50℃ and keep stirring.

[0104] (3) Prepare hydrogen peroxide solution with a concentration of 30 wt% and add it dropwise to the reactor at a rate of 7.8 g for 1.5 h. After the addition is complete, continue to maintain the temperature and stir thoroughly for 3 h to obtain a product containing trimethylbenzoquinone.

[0105] Example 4

[0106] Following the method of Example 3, except that catalyst C was replaced with an equal mass of catalyst D, and other conditions were the same as in Example 3, a product containing trimethylbenzoquinone was obtained.

[0107] Example 5

[0108] Following the method of Example 3, except that catalyst C was replaced with an equal mass of catalyst E, and other conditions were the same as in Example 3, a product containing trimethylbenzoquinone was obtained.

[0109] Comparative Example 1

[0110] Following the method of Example 3, except that the catalyst is methyl rhenium trioxide of the same mass as catalyst C, without containing non-metallic ligands, and other conditions are the same as in Example 3, a product containing trimethylbenzoquinone is obtained.

[0111] Comparative Example 2

[0112] Following the method of Example 3, except that no catalyst was added, and other conditions were the same as in Example 3, a product containing trimethylbenzoquinone was obtained.

[0113] Comparative Example 3

[0114] Following the method of Example 3, except that no solvent was added, and all other conditions were the same as in Example 3, a product containing trimethylbenzoquinone was obtained.

[0115] Comparative Example 4

[0116] The method of Example 3 was followed, except that methyl rhenium trioxide and the compound shown in Formula XI were mixed at room temperature in a molar ratio of 1:1 to obtain a catalyst, which replaced an equal mass of catalyst C as a ligand catalyst. Other conditions were the same as in Example 3, and a product containing trimethylbenzoquinone was obtained.

[0117]

[0118] Comparative Example 5

[0119] The method of Example 3 is followed, except that iron oxide and the non-metallic ligand shown in Formula VII are mixed at room temperature in a molar ratio of 1:1 to obtain a catalyst, and an equal mass of catalyst C is replaced. Other conditions are the same as in Example 3 to obtain a product containing trimethylbenzoquinone.

[0120] The trimethylbenzoquinone-containing products of each example and comparative example were washed with water and then separated into phases. The organic phase was then subjected to distillation to remove light and heavy components, yielding trimethylbenzoquinone. Table 1 shows the feed conversion rate, selectivity, and yield of trimethylbenzoquinone for each example and comparative example.

[0121]

[0122] Yield = Conversion Rate × Selectivity × 100%

[0123] All the above data were obtained using gas chromatography analysis.

[0124] Table 1

[0125]

[0126]

[0127] As can be seen from the results in Table 1, the preparation method of the present invention for trimethylbenzoquinone has a higher conversion rate of the reactant parabens and a higher selectivity of the product trimethylbenzoquinone, showing significantly better results.

[0128] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing trimethylbenzoquinone, characterized in that, The method includes the following steps: The reaction solution containing parabens and organic solvents is mixed with a ligand catalyst and then subjected to an oxidation reaction with an oxidant to obtain trimethylbenzoquinone; The ligand catalyst comprises methyl rhenium trioxide and non-metallic ligands, wherein the non-metallic ligands are compounds containing at least two C=N structures.

2. The preparation method according to claim 1, wherein, The molar ratio of methyl rhenium trioxide to nonmetallic ligands in the ligand catalyst is 0.5-4:1, preferably 0.8-1.2:

1.

3. The preparation method according to claim 1 or 2, wherein, The nonmetallic ligand has the structure shown in Formula I; Wherein, R1 is p-chlorophenyl, p-fluorophenyl, p-carboxyphenyl, or p-hydroxyphenyl; R2 and R3 are each independently hydrocarbon groups containing 1-6 carbon atoms.

4. The preparation method according to any one of claims 1-3, wherein, R2 and R3 bonds form a ring; Preferably, the nonmetallic ligand has the structure shown in Formula II; R1 is p-chlorophenyl, p-fluorophenyl, p-carboxyphenyl, or p-hydroxyphenyl.

5. The preparation method according to any one of claims 1-4, wherein, The amount of the ligand catalyst used is 0.5-10 wt% of the amount of pseudotrimethylbenzene used, preferably 2.5-5 wt%.

6. The preparation method according to any one of claims 1-5, wherein, The mass ratio of the organic solvent to pseudotrimethylbenzene is 5-100:1, preferably 8-20:

1.

7. The preparation method according to any one of claims 1-6, wherein, The organic solvent is selected from at least one of fatty alcohols, fatty acids, organic acid anhydrides, halogenated organic acids and halogenated hydrocarbons, and preferably from at least one of methanol, ethanol, formic acid, acetic acid, trifluoroacetic acid and acetic anhydride.

8. The preparation method according to any one of claims 1-7, wherein, The molar ratio of the oxidant to p-trimethylbenzene is 0.5-8:1, preferably 2.5-5:1; Preferably, the oxidant is hydrogen peroxide.

9. The preparation method according to claim 8, wherein, The oxidant is added in the form of an oxidant solution, and the mass concentration of the oxidant in the oxidant solution is 15-50 wt%.

10. The preparation method according to any one of claims 1-9, wherein, The oxidation reaction The appropriate conditions include: a reaction temperature of 20-90℃, preferably 30-85℃, and more preferably 45-80℃; The reaction time is 0.1-36 h, preferably 1-12 h, and more preferably 2-6 h.

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