A method for preparing 2,3,5-trimethylbenzoquinone

Abstract

The application relates to a preparation method of 2,3,5-trimethylbenzoquinone, which comprises circulating a reaction material containing trimethylphenol and an organic solvent between a first catalytic reaction zone and a second catalytic reaction zone in series, introducing a first oxidant into the first catalytic reaction zone when or before the reaction material contacts the first catalytic reaction zone, introducing a second oxidant into the second catalytic reaction zone when or before the reaction material contacts the second catalytic reaction zone, collecting the reaction material discharged from the second catalytic reaction zone, and returning the reaction material to the upstream of the first catalytic reaction zone after selectively adding trimethylphenol, and repeating the circulation. By adopting a two-stage catalytic oxidation reaction system and differentiating and optimizing the catalyst compositions in the first and second catalytic reaction zones, high selectivity and high yield of 2,3,5-trimethylbenzoquinone are obtained in continuous large-scale production.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and specifically to a method for preparing 2,3,5-trimethylbenzoquinone. Background Technology

[0002] 2,3,5-Trimethylbenzoquinone (Trimethylbenzoquinone for short) is a key intermediate in the synthesis of vitamin E and some pharmaceutical chemicals. The mainstream production route uses 2,3,6-trimethylphenol (Trimethylphenol for short) as raw material and synthesizes 2,3,5-trimethylbenzoquinone in one step through catalytic oxidation reaction.

[0003] Early industrial-scale attempts often employed homogeneous catalytic systems with transition metal halides (such as copper chloride) as the main catalyst. The biggest drawback of these homogeneous copper chloride systems is their low catalyst activity, often requiring stoichiometric or even higher amounts of catalyst to achieve the desired catalytic activity. Furthermore, homogeneous catalysts are difficult to efficiently separate and recover from the product system after the reaction, and their reusability is poor, which is detrimental to the requirements of green chemistry and cost control.

[0004] To address the challenge of separating and recovering homogeneous catalysts, the applicant previously proposed a method for preparing trimethylbenzoquinone using a resin-supported catalyst (see patent document CN 101665422 B). This method uses macroporous or gel-type resin as a support, reacting it with a transition metal salt in an organic solvent to form a resin-supported transition metal catalyst, which is then used for the catalytic oxidation of 2,3,6-trimethylphenol to 2,3,5-trimethylbenzoquinone. Theoretically, this type of catalyst combines high activity with easy separation and recovery, and can be applied to fixed-bed or trickle-bed reactors for continuous operation. However, after verifying its feasibility in small-batch trials, this technology still faces engineering challenges such as maintaining catalyst activity and selectivity, and ensuring long-term operational stability during industrial scale-up. These are common challenges faced by supported catalysts during scale-up.

[0005] Therefore, there is an urgent need in this field to develop a new method for preparing trimethylbenzoquinone that can achieve high selectivity, high yield, good scale-up feasibility, and is suitable for continuous production operation.

[0006] The above background information is provided only to aid in understanding the concept and technical solution of this application. It does not necessarily belong to the prior art of this application, nor does it necessarily provide technical guidance. In the absence of clear evidence that the above information was disclosed before the filing date of this application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0007] The purpose of this invention is to provide a new method for preparing trimethylbenzoquinone that can achieve high selectivity, high yield, good scale-up feasibility, and is suitable for continuous production operation.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing 2,3,5-trimethylbenzoquinone, comprising: The reactants containing trimethylphenol and organic solvent are circulated between a first catalytic reaction zone and a second catalytic reaction zone connected in series, wherein the reactants pass through the first catalytic reaction zone and the second catalytic reaction zone in sequence. When or before the reactants come into contact with the first catalytic reaction zone, a first oxidant is introduced into the first catalytic reaction zone; when or before the reactants come into contact with the second catalytic reaction zone, a second oxidant is introduced into the second catalytic reaction zone. The reactants exiting from the second catalytic reaction zone are collected, and after selectively adding the trimethylphenol, they are returned to the upstream of the first catalytic reaction zone to repeat the cycle. The first catalytic reaction zone is filled with a first supported catalyst, the active components of which include copper and nickel, and the molar amount of copper is greater than the molar amount of nickel. The second catalytic reaction zone is filled with a second supported catalyst, the active components of which include copper and nickel, wherein the molar amount of copper is less than the molar amount of nickel.

[0009] In some embodiments, the molar ratio of copper to nickel in the first supported catalyst is 1:(0.05~0.2), preferably 1:(0.08~0.15), such as 1:0.08, 1:0.09, 1:0.1, 1:0.11, 1:0.12, 1:0.13, 1:0.14, 1:0.15.

[0010] In some embodiments, the molar ratio of copper to nickel in the second supported catalyst is 1:(2~3), preferably 1:(2.3~2.8), such as 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8.

[0011] In some embodiments, the supports in both the first supported catalyst and the second supported catalyst are silica gel.

[0012] In some embodiments, the mass ratio of the active component to the support in the first supported catalyst and the second supported catalyst is independently (0.01~0.08):1, preferably (0.01~0.05):1, such as 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1.

[0013] In some embodiments, the mass ratio of the first supported catalyst packed in the first catalytic reaction zone to the second supported catalyst packed in the second catalytic reaction zone is 1:(0.8~1.2), 1:0.8, 1:0.9, 1:1, 1:1.1, or 1:1.2.

[0014] In some embodiments, the first supported catalyst is prepared by dissolving copper halide and nickel halide in water to form a mixed metal salt solution; then adding a support to the mixed salt solution and performing adsorption treatment to load copper ions and nickel ions onto the support; after adsorption, removing water from the system by evaporation to obtain the first supported catalyst.

[0015] In some embodiments, the second supported catalyst is prepared by dissolving copper halide and nickel halide in water to form a mixed metal salt solution; then adding a support to the mixed salt solution and performing adsorption treatment to load copper ions and nickel ions onto the support; after adsorption, removing water from the system by evaporation to obtain the second supported catalyst.

[0016] Furthermore, the copper halide is copper chloride. During feeding, the copper chloride can be added in its anhydrous form or in its hydrated form (e.g., copper chloride dihydrate). That is, the copper chloride raw material used for feeding is selected from at least one of anhydrous copper chloride and copper chloride hydrate.

[0017] Furthermore, the nickel halide is nickel chloride. During feeding, the nickel chloride can be added in its anhydrous form or in its hydrated form (e.g., nickel chloride hexahydrate). That is, the nickel chloride raw material used for feeding is selected from at least one of anhydrous nickel chloride and nickel chloride hydrate.

[0018] In some embodiments, throughout the cycle, the mass content of trimethylphenol in the reactants entering the first catalytic reaction zone is controlled to be less than 12%, and the mass content of water is controlled to be 2% to 5%.

[0019] Furthermore, throughout the entire cycle, the mass content of trimethylphenol in the reactants entering the first catalytic reaction zone is controlled to be less than 2% to 8%, and the mass content of water is controlled to be 2% to 5%.

[0020] In some embodiments, the first oxidant and the second oxidant are each independently selected from oxygen or an oxygen-containing mixture, and the oxygen volume flow rate entering the first catalytic reaction zone is less than or equal to the oxygen volume flow rate entering the second catalytic reaction zone. Preferably, the oxygen volume flow rate entering the first catalytic reaction zone is less than the oxygen volume flow rate entering the second catalytic reaction zone.

[0021] In some specific embodiments, both the first oxidant and the second oxidant are air, and the volume flow rate ratio of the first oxidant to the second oxidant is (0.2~1):1.

[0022] Furthermore, the inlet flow rate of the first oxidant is 4.5 Nm. 3 / h~15Nm 3 / h, the influent flow rate of the reactants in the first catalytic reaction zone is 1m³ / h. 3 / h~3m 3 / h.

[0023] In some embodiments, the temperature of the reactants entering the first catalytic reaction zone and the second catalytic reaction zone is controlled independently to be 75°C to 95°C.

[0024] In some embodiments, the organic solvent is selected from one or more of n-butanol, n-pentanol, and n-hexanol, and the mass ratio of the organic solvent to the total trimethylphenol is (1~5):1. This invention uses alcohol solvents with high boiling points and weak polarity as the reaction solvent, which on the one hand reduces losses during oxidation reactions; on the other hand, it meets the polarity requirements of ionic and free radical reactions on the reaction system.

[0025] In some embodiments, the trimethylphenol is 2,3,6-trimethylphenol.

[0026] In some embodiments, the reactants also include hydrochloric acid.

[0027] Furthermore, the mass ratio of the hydrochloric acid to the organic solvent is (0.01~0.05):1, and the mass concentration of the hydrochloric acid is 25%~36%.

[0028] In some embodiments, the preparation method is carried out based on a reaction apparatus, which includes a trickle bed reactor, a circulating vessel, and a reflux condenser. The trickle bed reactor has a first catalytic reaction zone and a second catalytic reaction zone arranged sequentially from top to bottom. The shell portion above the first catalytic reaction zone is provided with a first air inlet for introducing the first oxidant and a feed inlet for introducing the reactants. The shell portion between the first catalytic reaction zone and the second catalytic reaction zone is provided with a second air inlet for introducing the second oxidant. The shell portion below the second catalytic reaction zone is provided with a discharge outlet. The circulating vessel is in fluid communication with the feed inlet of the trickle bed reactor through a circulation system. The circulation system includes a circulation pipeline and a circulation pump installed on the circulation pipeline. The circulation pipeline is provided with a trimethylphenol feed inlet. The reflux condenser is connected to the circulating vessel via a reflux pipeline system. The reflux condenser is configured to: condense and discharge the gaseous material entering the circulating vessel, and / or return a portion of the condensed material to the circulating vessel.

[0029] In some embodiments, reactants other than trimethylphenol are first introduced into the circulating reactor for mixing. The mixed material is then fed into the trickle bed reactor through a circulation pipeline. The first oxidant and the second oxidant are introduced into the trickle bed reactor through the first air inlet and the second air inlet, respectively. The circulating reactor is heated until the material temperature in the circulating reactor reaches a preset temperature. Then, trimethylphenol is introduced through the trimethylphenol feed port.

[0030] In some embodiments, the trimethylphenol is introduced into the trimethylphenol feed port in molten form.

[0031] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: This invention employs a two-stage catalytic oxidation reaction system and differentiates and optimizes the catalyst composition in the first and second catalytic reaction zones, thereby achieving a synergistic improvement in catalytic activity and selectivity, and obtaining high selectivity and high yield of 2,3,5-trimethylbenzoquinone in continuous scale-up production. Attached Figure Description

[0032] Figure 1 A schematic diagram of the structure of a reaction device provided by the present invention; Figure 2 The liquid chromatogram of the reaction solution during the oxidation process in the preparation method of 2,3,5-trimethylbenzoquinone provided by the present invention; Figure 3 This is the liquid chromatogram of 2,3,5-trimethylbenzoquinone finally obtained in Example 4 of the present invention; Among them, 1. trickle bed reactor; 11. reactor shell; 12. first catalyst bed; 13. second catalyst bed; 14. intermediate redistribution zone; 15. first air inlet; 16. second air inlet; 2. Circulating vessel; 21. Vessel body; 22. Stirring mechanism; 23. Jacket; 24. Material feeding port; 3. Reflux condenser; 31. Exhaust port; 32. Drain port; 4. Circulation system; 41. Circulation pump; 42. Trimethylphenol feed port. Detailed Implementation

[0033] In the existing technology, the mainstream catalytic system for preparing 2,3,5-trimethylbenzoquinone (TMBQ) mostly uses copper halide as the main catalyst, and 2,3,6-trimethylphenol (TMP) is oxidized by air or oxygen-enriched air.

[0034] Based on the above, this invention proposes a composite catalytic system using copper halide as the main catalyst and nickel halide as the co-catalyst, employing the air oxidation method to prepare 2,3,5-trimethylbenzoquinone from 2,3,6-trimethylphenol. The reaction process was observed and intermediate samples were analyzed. Figure 2 As shown), the inventors infer that in a system with copper chloride as the main catalyst and nickel chloride as the co-catalyst, the oxidation reaction mainly follows the following three-step reaction pathway: (1) Reaction 1: ; (2) Reaction 2: ; (3) Reaction 3: .

[0035] The inventors conducted independent studies on the three steps of the reaction described above, and the results showed that: Reaction 1: 2,3,6-Trimethylphenol reacts with copper chloride to produce 4-chloro-2,3,6-trimethylphenol. This is a rapid reaction that can proceed even without the introduction of air. During the reaction, the color of copper chloride can be clearly observed to change from dark green to yellow-green, and the characteristic peak of 4-chloro-2,3,6-trimethylphenol can be clearly captured by liquid chromatography.

[0036] Reaction 2: This is the process of regenerating cupric chloride by reacting cuprous chloride with oxygen. Its reaction rate is slower than that of reaction 1 and it is more sensitive to process conditions, especially in terms of moisture content and oxygen concentration. Maintaining a suitable moisture content and a high oxygen concentration is necessary to effectively increase the reaction rate.

[0037] Reaction 3: This is the process of 4-chloro-2,3,6-trimethylphenol reacting further with oxygen to generate the target product. It is the rate-controlling step of the overall reaction, with a slow reaction rate, and is also the key stage for the generation of polyaromatic byproducts.

[0038] Destructive testing further demonstrated that simultaneously increasing the concentrations of 4-chloro-2,3,6-trimethylphenol and 2,3,6-trimethylphenol in the reaction system significantly accelerated the formation of polyaromatic byproducts. The most significant byproduct originated from the coupling reaction between 2,3,6-trimethylphenol and the 4-chloro-2,3,6-trimethylphenol intermediate.

[0039] However, neither traditional batch reactors nor continuous reactors such as single-stage fixed-bed reactors, which were attempted in the applicant's previous research, have been able to effectively overcome the technical obstacles caused by the differences in reaction rates in multiple steps. As a result, the selectivity and yield of the target product (2,3,5-trimethylbenzoquinone) have been in a bottleneck state for a long time. In particular, under the scale of pilot-scale and industrial production, the problem of uneven mass and heat transfer has been further aggravated, and the yield has dropped significantly.

[0040] This invention breaks through the conventional thinking of single-stage reactors and creatively constructs two-stage catalytic oxidation reaction zones that are connected in series and have different functions. This allows both the fast and slow reactions in the preparation of 2,3,5-trimethylbenzoquinone to be controlled in an optimal reaction state, unexpectedly achieving a significant improvement in the selectivity and yield of 2,3,5-trimethylbenzoquinone on an industrial scale.

[0041] Specifically, the first catalytic reaction zone is filled with a first supported catalyst, whose active components have a high copper loading and a low nickel loading. The high copper loading provides sufficient active sites, thereby promoting the formation of the intermediate 4-chloro-2,3,6-trimethylphenol. The second catalytic reaction zone is filled with a second supported catalyst, whose active components have a high nickel loading and a low copper loading. The high nickel loading significantly enhances the catalytic activity of the aforementioned slow reaction, accelerates the conversion of the intermediate, reduces its residence time and accumulation concentration in the system, and thus effectively inhibits its coupling with unreacted raw materials to form polyaromatic byproducts. Simultaneously, a second oxidant is further added to the second catalytic reaction zone to increase the reaction rate of the slow reaction and shorten the lifetime of the intermediate in the reaction system.

[0042] This invention, through in-depth research, also discovered that when the water content of the reaction system is high, the reaction rate for the formation of 4-chloro-2,3,6-trimethylphenol is accelerated, but the reaction rate for the oxidation of 4-chloro-2,3,6-trimethylphenol to 2,3,5-trimethylbenzoquinone is reduced. Furthermore, if the concentrations of both 2,3,6-trimethylphenol and 4-chloro-2,3,6-trimethylphenol increase simultaneously in the reaction system, it easily leads to an increase in byproducts. Similarly, a low water content in the reaction system is also unfavorable for the reaction. This invention further preferably uses silica gel as a carrier, which can utilize the strong water absorption of silica gel as a water storage medium to maintain the water content of the reaction system within a relatively constant and suitable range, thereby ensuring the reaction rate while also achieving high yield and high selectivity.

[0043] Based on this, the present invention provides a novel method for preparing 2,3,5-trimethylbenzoquinone and a reaction apparatus suitable for this preparation method. The preparation method of the present invention will be further described below in conjunction with the reaction apparatus.

[0044] like Figure 1 As shown, the reaction apparatus includes a trickle bed reactor 1, a circulating vessel 2, and a reflux condenser 3.

[0045] The trickle bed reactor 1 mainly includes a reactor shell 11, and a first catalyst bed 12 and a second catalyst bed 13 (i.e., the first catalytic reaction zone and the second catalytic reaction zone) disposed within the reactor shell 11.

[0046] The reactor shell 11 is preferably a vertical cylindrical pressure vessel, and its material can be selected from materials known in the art, such as stainless steel, carbon steel lining, or nickel-based alloys (such as Hastelloy), depending on the corrosiveness of the reaction medium and the operating temperature and pressure conditions. The top of the reactor shell 11 has an inlet for introducing the reaction raw material liquid and a first air inlet 15 for introducing the first oxidant, while the bottom of the reactor shell 11 has an outlet for discharging the reaction product mixture.

[0047] The first catalyst bed 12 is filled with a first supported catalyst. The active components of the first supported catalyst include copper and nickel, with the molar amount of copper being greater than that of nickel. This provides sufficient active sites for the aforementioned reaction 1, promoting the formation of the intermediate 4-chloro-2,3,6-trimethylphenol. Consequently, the concentration of 4-chloro-2,3,6-trimethylphenol in the material leaving the first catalyst bed 12 is high, while the concentration of trimethylphenol is low. The active component nickel mainly converts cuprous ions into copper ions. Preferably, the molar ratio of copper to nickel in the first supported catalyst is 1:(0.05~0.2).

[0048] The second catalyst bed 13 is packed with a second supported catalyst. The active components of the second supported catalyst also include copper and nickel, but the molar amount of copper is less than that of nickel, which can accelerate the conversion of intermediates, reduce their residence time and accumulation concentration in the system, and inhibit the formation of by-products. Preferably, the molar ratio of copper to nickel in the second supported catalyst is 1:(2~3).

[0049] Both the first and second supported catalysts use silica gel as the support, with the active component to support mass ratio of (0.01~0.08):1 for each, thus balancing the stability and catalytic activity of the active component. Preferably, the silica gel is controlled to a size of 2-20 mesh for low flow resistance. The loading amount of the second catalyst bed 13 is preferably 0.8-1.2 times that of the first catalyst bed 12. The proportional arrangement of the two catalyst beds facilitates process adjustment. Specifically, when the selectivity of the oxidation reaction fluctuates, simply sampling and testing the reaction solution content from one section is sufficient to determine how to adjust the process.

[0050] Preferably, each of the first catalyst bed 12 and the second catalyst bed 13 is provided with a set of bed support mechanisms at its bottom. These support mechanisms primarily support the entire weight of the catalyst above while simultaneously allowing the gas-liquid two-phase fluid to pass through smoothly with low resistance. As an example, the bed support mechanism can be a high-strength support grid, with the grid spacing determined according to the size of the catalyst particles, typically set to 0.3 to 0.7 times the equivalent diameter of the catalyst particles. To further improve the support effect and prevent catalyst particles from leaking through the gaps, one or more layers of metal wire mesh with different mesh sizes can be laid above the support grid.

[0051] Existing technologies sometimes employ oxygen-enriched air or pure oxygen for oxidation to improve reaction efficiency. However, these techniques can only be implemented on a small-scale basis, and large-scale production remains hampered by safety concerns. To address this challenge, this invention further employs an air-to-liquid ratio (i.e., the gas-to-liquid feed volume ratio) operating mode. This allows the gas-liquid two-phase fluid to flow rapidly within the gaps between catalyst particles, increasing the gas-liquid contact area and thereby improving the utilization rate of oxygen in the air. Consequently, the oxygen mass transfer requirements can be met even under conventional air conditions.

[0052] Based on this, to ensure the synergistic effect of the above-mentioned gas-liquid ratio operation mode and the two-stage reaction configuration, the present invention divides the internal structure of the reactor into the following functional zones: along the longitudinal axis of the reactor shell 11, from top to bottom, there are a top gas-liquid distribution zone, a first catalyst bed 12, an intermediate redistribution zone 14, a second catalyst bed 13, and a bottom collection zone. The top gas-liquid distribution zone, the intermediate redistribution zone 14, and the bottom collection zone are separated and connected by a bed support mechanism and a catalyst bed to achieve gas-liquid separation and flow.

[0053] In the top gas-liquid distribution zone, the feed flow rate of the reaction raw material liquid at the inlet is preferably 1 m³ / s. 3 / h~3m 3 / h, further preferably 1.5m 3 / h~2m 3 / h. To uniformly distribute the reaction feed liquid across the cross-section of the first catalyst bed 12, a liquid distributor is preferably provided. The liquid distributor is fluidly connected to the aforementioned liquid inlet, and can adopt various forms known in the art to accommodate different liquid phase loads and properties such as viscosity or surface tension. As a non-limiting example, it can be any one of a perforated plate distributor, a tray distributor, or a spray pipe distributor, or a combination of the aforementioned forms. Regardless of the specific form used, the design of the liquid distributor should ensure that the liquid phase can form a continuous and uniform drip or spray to initially wet the entire bed cross-section. The first oxidant inlet flow rate of the first inlet 15 is preferably 4.5 Nm³. 3 / h~15Nm 3 / h. The reactants entering the first catalyst bed 12 move downwards under the drag of the first oxidant.

[0054] Preferably, the inlet end of the first air inlet 15 is connected to a first gas distributor for introducing a first stream of oxidant into the first catalyst bed 12. Spatially, the first gas distributor can be positioned above, to the side of, or around the liquid distributor. To prevent direct impact of the airflow on the liquid distributor, which could cause deformation or droplet splashing, the gas outlet direction of the first gas distributor is preferably downward, i.e., towards the first catalyst bed 12, or towards the central axis of the reactor shell 11. The first gas distributor can take many forms known in the art. As a non-limiting example, the first gas distributor can be an annular tube distributor or a sieve plate distributor, the design of which allows the gas to pass through the top space with a small pressure drop and uniform flow rate, thereby contacting the droplets released from the liquid distributor in parallel or cross-flow, forming a gas-liquid two-phase mixture that then uniformly enters the first catalyst bed 12. In addition, to monitor the supply status of the first oxidant in real time, a first pressure detection element and a first flow detection element, such as a pressure transmitter and a volumetric flow meter, are preferably installed on the pipeline where the first air inlet 15 is located, so that the operator or automatic control system can adjust the air intake according to the real-time data to maintain a suitable gas-liquid ratio. A first gas valve is also installed on the pipeline where the first air inlet 15 is located.

[0055] The intermediate redistribution zone 14 is located between the first catalyst bed 12 and the second catalyst bed 13, and a second air inlet 16 is provided on its shell sidewall for introducing a second oxidant. The preferred flow rate of the second oxidant at the second air inlet 16 is 10 Nm³. 3 / h~30 Nm 3 / h. A second gas valve is also installed on the pipeline where the second inlet 16 is located. Similarly, to accurately control the flow rate and pressure of this gas, a second pressure detection element and a second flow detection element are preferably installed on the pipeline where the second inlet 16 is located. In this area, a second gas distributor is further preferably installed, which is in fluid communication with the aforementioned second inlet 16. The specific structural form of the second gas distributor can be designed with reference to the aforementioned first gas distributor, that is, it is also preferably a ring tube or sieve plate structure, and its gas outlet direction is also set downward or towards the central axis of the reactor to avoid serious disturbance to the normal flow of the downward liquid by the high-speed airflow.

[0056] The bottom collection zone is located below the second catalyst bed 13 and is formed by the lower end cap of the reactor shell 11 and the bottom bed support structure. This collection zone is mainly used to provide sufficient buffer space for the gas-liquid two-phase reaction products and guide the fluid to flow smoothly to the outlet.

[0057] The circulating vessel 2 is used to contain, stir, and heat the reaction materials, while simultaneously separating and refluxing unreacted gaseous raw materials and circulating the reaction liquid.

[0058] Specifically, the circulating reactor 2 includes a reactor body 21, a stirring mechanism 22, and a jacket 23. The reactor body 21 is preferably a vertical cylindrical container, and its material can be selected from materials known in the art, such as stainless steel, glass enamel, or nickel-based alloys, depending on the corrosiveness of the reaction medium and the operating temperature requirements. The upper end of the reactor body 21 has a material feeding port 24, a reaction product inlet, a gas outlet, and a reflux port, while the bottom of the reactor body 21 has a circulating outlet for discharging the reaction liquid. Furthermore, the bottom of the reactor body 21 also has a product outlet, which is used to extract the reaction liquid rich in the target product from the reaction system after the reaction reaches a predetermined conversion rate and send it to subsequent separation and purification processes.

[0059] The reaction product inlet is fluidly connected to the outlet at the bottom of the aforementioned trickle bed reactor 1, and is used to receive the mixture stream containing reaction products, unreacted raw materials, and entrained gases discharged from the trickle bed reactor 1. The material feed inlet 24 is connected to an external solvent or other reaction raw material pipeline, and is used to introduce reaction solvents and additives into the vessel body 21. A reflux condenser 3 is connected between the gas outlet and the reflux port. This reflux condenser 3 can be a shell-and-tube or coil heat exchanger conventional in the art, and its cooling medium can be selected from circulating cooling water or a low-temperature refrigerant, such as an aqueous solution of ethylene glycol. The specific working process is as follows: the gas components entering the vessel 21 from the reaction product inlet accumulate in the upper space of the vessel 21 and flow into the reflux condenser 3 from the gas outlet. After heat exchange with the cooling medium, the condensable components in the gas are condensed into liquid phase, while the non-condensable tail gas is discharged from the exhaust port 31 set at the top of the reflux condenser 3. The condensed liquid phase (part of the condensable substances, such as water) returns to the interior of the vessel 21 from the reflux port by gravity or pressure difference, while the other part can be discharged through the drain port 32 set at the bottom of the reflux pipeline or condenser, thereby maintaining the water content of the reaction system.

[0060] The discharge port at the bottom of the vessel 21 is connected to the inlet of the trickle bed reactor 1 via the circulation system 4, thereby realizing continuous circulation of the reaction liquid between the circulating vessel 2 and the trickle bed reactor 1. The circulation system 4 mainly includes pipes and a circulation pump 41 mounted on the pipes. The type of circulation pump 41 can be selected according to the viscosity, temperature, and flow rate requirements of the liquid being transported, using commonly used liquid transport equipment in the field such as centrifugal pumps, magnetic pumps, or metering pumps. A trimethylphenol feed port 42 is also provided on the pipes, which is used to introduce the reaction raw material, namely 2,3,6-trimethylphenol, into the circulation system 4. Through the circulation system 4, the reaction liquid in the circulating vessel 2, together with the 2,3,6-trimethylphenol raw material, is sent to the top inlet of the trickle bed reactor 1 at a set flow rate by the circulation pump 41. After being evenly distributed by the top liquid distributor, it enters the catalyst bed to participate in the reaction, forming a complete reaction liquid circulation loop.

[0061] One end of the stirring mechanism 22 extends into the vessel body 21. Its drive end, located outside the vessel body 21, is connected to a motor or reducer. The stirring end inside the vessel body 21 can be equipped with a paddle, turbine, or anchor impeller. Its function is to continuously and uniformly stir the liquid inside the vessel to enhance heat transfer and promote mixing. A jacket 23 is located on the outer wall of the vessel body 21 and contains a heating medium, such as hot water or heat transfer oil, used to provide or remove the required heat to the material inside the vessel to maintain a suitable reaction temperature. As an example, hot water is used as the heating medium. The hot water enters the jacket 23 from the external hot water supply main pipe, exchanges heat with the vessel wall, and is discharged from the return water pipe. To precisely regulate the hot water inflow, a hot water inlet valve is installed on the heat source supply pipe.

[0062] Unless otherwise specified, the liquid chromatography detection conditions for 4-chloro-2,3,6-trimethylphenol in this invention are as follows: Column: Eclipse XDB C18 5μm×150mm×4.6mm; Quantitative loop: 20 μL; Mobile phase: Acetonitrile: Water: Trifluoroacetic acid = 500 mL: 400 mL: 0.2 g; Flow rate: 1.0 mL / min; The detection wavelength is 215nm.

[0063] The liquid chromatography detection conditions for 2,3,5-trimethylbenzoquinone in this invention are as follows: Column: Eclipse XDB C18 5μm×150mm×4.6mm; Quantitative loop: 20 μL; Mobile phase: Acetonitrile: Water: Trifluoroacetic acid = 500 mL: 600 mL: 0.3 g; Flow rate: 1.0 mL / min; The detection wavelength is 260nm.

[0064] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other. Unless otherwise specified, the reagents and instruments used in the following embodiments and comparative examples are commercially available products or can be prepared with reference to existing technology.

[0065] Example 1: Preparation of silica-supported catalysts: (1) Preparation of the first silica-supported catalyst: Add the following to a rotary drum thin-film evaporator: 80L deionized water, 2.5kg copper chloride dihydrate (CuCl2•2H2O), and 0.4kg nickel chloride hexahydrate (NiCl2•6H2O). Set the rotary drum thin-film evaporator speed to 15 r / min and dissolve for 10 minutes. After dissolution, add 60kg of FNG-Ⅱ type coarse-pore water-resistant silica gel spheres (diameter: 4~8mm; commercially available product, Qingdao Jiyida Silica Gel Reagent Co., Ltd.) for adsorption. After adsorption for 1.0 h, introduce 0.1MPa steam into the jacket 23 of the rotary drum thin-film evaporator for heating, controlling the vacuum degree of the rotary drum thin-film evaporator to -0.085MPa, and evaporate the water. After water evaporation is complete, remove the catalyst from the rotary drum thin-film evaporator to obtain the first silica gel supported catalyst.

[0066] (2) Preparation of the second silica-supported catalyst: Add the following to a rotary drum thin-film evaporator: 80 L of deionized water, 0.8 kg of CuCl₂•2H₂O, and 2.8 kg of NiCl₂•6H₂O. Set the evaporator speed to 15 r / min and dissolve for 10 minutes. After dissolution, add 60 kg of FNG-Ⅱ type coarse-porous water-resistant silica gel spheres (as above) for adsorption. After 1.0 h of adsorption, introduce 0.1 MPa steam into the jacket 23 of the rotary drum thin-film evaporator for heating, controlling the vacuum level of the evaporator to -0.085 MPa, and evaporate the water. After evaporation, remove the catalyst from the rotary drum thin-film evaporator to obtain the second silica gel-supported catalyst.

[0067] Oxidation reaction: The first silica-supported catalyst and the second silica-supported catalyst are respectively loaded into the first catalyst bed 12 and the second catalyst bed 13 of the aforementioned trickle bed reactor 1, with a mass ratio of 1:1. An oxidation reaction is then carried out using the aforementioned reaction apparatus.

[0068] Specifically, 15.5 kg of hydrochloric acid (mass concentration of 32.5%) and 400 kg of n-hexanol are added to circulating reactor 2. The first gas valve is opened, and air (for clarity, this air is referred to as the first air) is introduced into the trickle bed reactor 1, with the first air flow rate set to 10.0 Nm³. 3 / h. Open the second gas valve to introduce air (for clarity, this air will be referred to as the second air), and set the second air flow rate to 21.7 Nm. 3 / h. Start the stirring mechanism 22 inside the circulating tank 2, start the circulating pump 41, and control the flow rate at the circulating outlet of the circulating tank 2 to 1.8m. 3 / h. The material in the circulating reactor 2 enters the circulating pump 41 from the bottom outlet of the circulating reactor 2. After being pressurized by the circulating pump 41, it enters the trickle bed reactor 1. Under the distribution of the liquid distributor, it is uniformly dispersed in the form of tiny droplets on the surface of the first silica gel supported catalyst. It is dragged down by the airflow and moves downward along the gaps between the catalyst particles. After exiting the first catalyst bed 12, it enters the second catalyst bed 13. The material exiting the second catalyst bed 13 returns to the circulating reactor 2. The hot water inlet valve of the jacket 23 of the circulating reactor 2 is opened to control the temperature inside the circulating reactor 2 to 80℃. When the temperature inside the circulating reactor 2 reaches 80℃, molten 2,3,6-trimethylphenol (purity: 99.2wt%) is slowly added from the 2,3,6-trimethylphenol feed port 42 located at the inlet of the circulating pump 41. The total feed amount of 2,3,6-trimethylphenol is 180kg, and the total feeding time is about 8.0h. Samples were taken from circulating reactor 2 to test the 2,3,6-trimethylphenol content. The feeding rate was adjusted to control the 2,3,6-trimethylphenol content at 5 wt% until all 2,3,6-trimethylphenol was added. During the reaction, samples were taken from circulating reactor 2 to test the moisture content. The drainage rate was adjusted by opening and closing the valve at drain outlet 32 ​​to control the moisture content of the material in circulating reactor 2 at 3 wt%. The flow rates of the first and second air sources were controlled to ensure that the oxygen content of the exhaust gas at exhaust outlet 31 was approximately 8.5 vol%. After the 2,3,6-trimethylphenol was added, the reaction continued until the residual 2,3,6-trimethylphenol and 4-chloro-2,3,6-trimethylphenol in circulating reactor 2 were both less than 1.0%, indicating the oxidation reaction was complete.

[0069] The oxidation reaction liquid in the circulating vessel 2 was transferred to the batch distillation vessel for distillation. The n-hexanol obtained from the distillation was reused, and finally 2,3,5-trimethylbenzoquinone was obtained: 194.5 kg (content: 98.8 wt%), with a molar yield of 97.61%.

[0070] Example 2: This embodiment is basically the same as Example 1, except that the amount of n-hexanol fed is 180 kg.

[0071] The final yield was 192.4 kg of 2,3,5-trimethylbenzoquinone (content: 99.1 wt%), with a molar yield of 96.85%.

[0072] Example 3: This embodiment is basically the same as Embodiment 1, except that the amount of n-hexanol fed is 900 kg.

[0073] The final yield was 196.1 kg of 2,3,5-trimethylbenzoquinone (content: 98.9 wt%), with a molar yield of 98.51%.

[0074] Example 4: This embodiment is basically the same as Example 1, except that all 2,3,6-trimethylphenol is added while controlling the 2,3,6-trimethylphenol content to 2wt%, and the total feeding time is approximately 13 hours. Simultaneously, the first air flow rate is controlled at 6.1 Nm³. 3 / h, Second airflow rate: 13.4 Nm 3 / h, ensuring that the oxygen content of the exhaust gas at exhaust port 31 is about 8.5 vol.

[0075] The final yield was 196.7 kg of 2,3,5-trimethylbenzoquinone (content: 99.4 wt%), with a molar yield of 99.30%.

[0076] Example 5: This embodiment is basically the same as Example 1, except that all 2,3,6-trimethylphenol is added while controlling the 2,3,6-trimethylphenol content to 8wt%, and the total feeding time is approximately 6 hours. Simultaneously, the first air flow rate is controlled at 13.3 Nm³. 3 / h, Second airflow rate: 29.0 Nm 3 / h, ensuring that the oxygen content of the exhaust gas at exhaust port 31 is about 8.5 vol.

[0077] The final yield was 191.9 kg of 2,3,5-trimethylbenzoquinone (content: 98.7 wt%), with a molar yield of 96.21%.

[0078] Example 6: This embodiment is basically the same as Embodiment 1, except that the temperature inside the circulating reactor 2 is controlled at 75°C, and the total feeding time of 2,3,6-trimethylphenol is approximately 10 hours. Simultaneously, the first air flow rate is controlled at 8.0 Nm³. 3 / h, Second airflow rate: 17.4 Nm 3 / h, ensuring that the oxygen content of the exhaust gas at exhaust port 31 is about 8.5 vol.

[0079] The final yield was 194.3 kg of 2,3,5-trimethylbenzoquinone (content: 98.4 wt%), with a molar yield of 97.11%.

[0080] Example 7: This embodiment is basically the same as Embodiment 1, except that the temperature inside the circulating reactor 2 is controlled at 95°C, and the total feeding time of 2,3,6-trimethylphenol is approximately 7 hours. Simultaneously, the first air flow rate is controlled at 11.4 Nm³. 3 / h, Second airflow rate: 24.8 Nm 3 / h, ensuring that the oxygen content of the exhaust gas at exhaust port 31 is about 8.5 vol.

[0081] The final yield was 191.6 kg of 2,3,5-trimethylbenzoquinone (content: 98.8 wt%), with a molar yield of 96.15%.

[0082] Example 8: This embodiment is basically the same as Embodiment 1, except that the ratio of the first air to the second air is reduced. Specifically, the first air flow rate is controlled at 5.2 Nm³. 3 / h, Second airflow rate: 26.5 Nm 3 / h, ensuring that the oxygen content of the exhaust gas at exhaust port 31 is about 8.5 vol.

[0083] The final yield was 195.3 kg of 2,3,5-trimethylbenzoquinone (content: 98.5 wt%), with a molar yield of 97.71%.

[0084] Example 9: This embodiment is basically the same as Embodiment 1, except that the ratio of the first air to the second air is increased. Specifically, the first air flow rate is controlled at 15.9 Nm³. 3 / h, Second airflow rate: 15.9 Nm 3 / h, ensuring that the oxygen content of the exhaust gas at exhaust port 31 is about 8.5 vol.

[0085] The final yield was 194.7 kg of 2,3,5-trimethylbenzoquinone (content: 98.7 wt%), with a molar yield of 97.61%.

[0086] Comparative Example 1: This comparative example is basically the same as Example 1, except that all 2,3,6-trimethylphenol was added uniformly while controlling the 2,3,6-trimethylphenol content to 12%, with a total feeding time of approximately 5 hours. Simultaneously, the first air flow rate was controlled at 16.0 Nm³. 3 / h, Second airflow rate: 34.7 Nm 3 / h, ensuring that the oxygen content of the exhaust gas at exhaust port 31 is about 8.5 vol.

[0087] The final yield was 187.7 kg of 2,3,5-trimethylbenzoquinone (content: 98.9 wt%), with a molar yield of 94.29%.

[0088] Comparative Example 2: This comparative example is basically the same as Example 1, except that: by adjusting the drainage volume by opening and closing the valve located at the drain outlet 32, the moisture content of the material in the circulating tank 2 is controlled at 9 wt%, and the 2,3,6-trimethylphenol content is controlled at 5 wt%. All 2,3,6-trimethylphenol is then added, with a total feeding time of approximately 12 hours. Simultaneously, the first air flow rate is controlled at 6.6 Nm³. 3 / h, Second airflow rate: 13.0 Nm 3 / h, ensuring that the oxygen content of the exhaust gas at exhaust port 31 is about 8.5 vol.

[0089] The final yield was 186.0 kg of 2,3,5-trimethylbenzoquinone (content: 98.6 wt%), with a molar yield of 93.15%.

[0090] Comparative Example 3: This comparative example is essentially the same as Example 1, except that in preparing the silica-supported catalyst, 160 L of deionized water, 3.3 kg of CuCl2•2H2O, and 3.2 kg of NiCl2•6H2O were added to the rotary drum thin-film evaporator, along with 120 kg of FNG-II type coarse-porous water-resistant silica gel spheres (same as in Example 1), for adsorption. After 1.0 h of adsorption, 0.1 MPa steam was introduced into the jacket 23 of the rotary drum thin-film evaporator for heating, controlling the vacuum degree of the rotary drum thin-film evaporator at -0.085 MPa, to evaporate the water. After the water evaporation was complete, the catalyst was removed from the rotary drum thin-film evaporator.

[0091] The prepared catalysts were loaded into the first catalyst bed 12 and the second catalyst bed 13 at a mass ratio of 1:1, and the oxidation reaction was carried out according to the process conditions of Example 1. The total feeding time of 2,3,6-trimethylphenol was approximately 10 hours. The first air flow rate was controlled at 8.0 Nm³. 3 / h, Second airflow rate: 17.4 Nm 3 / h, ensuring that the oxygen content of the exhaust gas at exhaust port 31 is about 8.5 vol.

[0092] The final yield was 184.1 kg of 2,3,5-trimethylbenzoquinone (content: 98.7 wt%), with a molar yield of 92.30%.

[0093] Comparative Example 4: This comparative example is basically the same as Example 1, except that in preparing the silica-supported catalyst, 160 L of deionized water, 5.0 kg of CuCl2•2H2O, and 0.8 kg of NiCl2•6H2O were added to the rotary drum thin-film evaporator, along with 120 kg of FNG-II type coarse-porous water-resistant silica gel (same as in Example 1) for adsorption. After 1.0 h of adsorption, 0.1 MPa steam was introduced into the jacket 23 of the rotary drum thin-film evaporator for heating, and the vacuum degree of the rotary drum thin-film evaporator was controlled at -0.085 MPa to evaporate the water. After the water was evaporated, the catalyst was removed from the rotary drum thin-film evaporator.

[0094] The prepared catalysts were loaded into the first catalyst bed 12 and the second catalyst bed 13 at a mass ratio of 1:1, and the oxidation reaction was carried out under the process conditions of Example 1. The total feeding time of 2,3,6-trimethylphenol was approximately 6 hours, and the first air flow rate was controlled at 13.3 Nm³. 3 / h, Second airflow rate: 29.0 Nm 3 / h, ensuring that the oxygen content of the exhaust gas at exhaust port 31 is about 8.5 vol.

[0095] The final yield was 178.3 kg of 2,3,5-trimethylbenzoquinone (content: 98.9 wt%), with a molar yield of 89.57%.

[0096] Comparative Example 5: This comparative example is essentially the same as Example 1, except that in preparing the silica-supported catalyst, 160 L of deionized water, 1.6 kg of CuCl2•2H2O, and 5.6 kg of NiCl2•6H2O were added to the rotary drum thin-film evaporator, along with 120 kg of FNG-II type coarse-porous water-resistant silica gel spheres (same as in Example 1), for adsorption. After 1.0 h of adsorption, 0.1 MPa steam was introduced into the jacket 23 of the rotary drum thin-film evaporator for heating, controlling the vacuum degree of the rotary drum thin-film evaporator at -0.085 MPa, to evaporate the water. After the water evaporation was complete, the catalyst was removed from the rotary drum thin-film evaporator.

[0097] The prepared catalysts were loaded into the first catalyst bed 12 and the second catalyst bed 13 at a mass ratio of 1:1, and the oxidation reaction was carried out under the process conditions of Example 1. The total feeding time of 2,3,6-trimethylphenol was approximately 10 hours, and the first air flow rate was controlled at 8.0 Nm³. 3 / h, Second airflow rate: 17.4 Nm 3 / h, ensuring that the oxygen content of the exhaust gas at exhaust port 31 is about 8.5 vol.

[0098] The final yield was 179.9 kg of 2,3,5-trimethylbenzoquinone (content: 98.6 wt%), with a molar yield of 90.10%.

[0099] Comparative Example 6: This comparative example is essentially the same as Example 1, except that only the first gas valve is opened, allowing air to be introduced through the first air inlet 15 for the reaction, while the second gas valve is closed. The first air flow rate is controlled at 31.7 Nm³. 3 / h, Second airflow rate: 0 Nm 3 / h, ensuring that the oxygen content of the exhaust gas at exhaust port 31 is about 8.5 vol.

[0100] The final yield was 182.6 kg of 2,3,5-trimethylbenzoquinone (content: 98.2 wt%), with a molar yield of 91.08%.

[0101] Comparative Example 7: This comparative example is basically the same as Example 1, except that the catalyst was prepared according to the scheme of Example 1 of the applicant's previous patent application with publication number CN101665422 B.

[0102] Specifically, the following were added to the rotary drum thin-film evaporator: 80 kg of n-hexanol, 22.5 kg of CuCl2•2H2O, and 15.5 kg of hydrochloric acid (mass concentration of 32.5%). The rotary drum thin-film evaporator was set to a rotation speed of 15 r / min, and the mixture was allowed to dissolve for 10 minutes. After dissolution, 120 kg of D301 resin was added for adsorption. After adsorption for 1.0 h, 0.1 MPa steam was introduced into the jacket 23 of the rotary drum thin-film evaporator for heating, and the vacuum degree of the rotary drum thin-film evaporator was controlled at -0.03 MPa to evaporate the water. After evaporation, the catalyst inside the rotary drum thin-film evaporator was removed.

[0103] The prepared catalysts were loaded into the first catalyst bed 12 and the second catalyst bed 13 at a mass ratio of 1:1, and the oxidation reaction was carried out according to the process conditions of Example 1. 320 kg of n-hexanol was added to the circulating reactor 2.

[0104] The final yield was 184.9 kg of 2,3,5-trimethylbenzoquinone (content: 98.7 wt%), with a molar yield of 92.70%.

[0105] This invention utilizes a two-stage trickle-bed reactor 1 to oxidize 2,3,6-trimethylphenol to prepare 2,3,5-trimethylbenzoquinone, which not only effectively overcomes the scale-up effect but also achieves high product selectivity and yield.

[0106] The comparison results of Examples 1, 4, and 5 with Comparative Example 1 show that the product yield decreases with increasing 2,3,6-trimethylphenol content in the reactants. Therefore, to balance reaction efficiency and product yield, the 2,3,6-trimethylphenol content in the reactants needs to be controlled within an appropriate range, neither too high nor too low. Preferably, its content accounts for 2% to 8% of the total reactants.

[0107] The comparison results between Example 1 and Comparative Example 2 show that when the moisture content of the material in the circulating vessel 2 is too high (e.g., ≥9%), the product yield decreases significantly. Therefore, timely discharge of condensate through drain outlet 32 ​​to control the moisture content in the circulating vessel 2 is of great significance for maintaining a high product yield.

[0108] The comparative results of Examples 1, 3 to 5, and 7 show that the catalyst composition has a significant impact on the product yield. When a single copper chloride component is used and the active component is supported on a conventional macroporous anion exchange resin, the product yield is not ideal. Furthermore, even when both catalyst beds use a two-component catalyst of copper chloride and nickel chloride, if the mass ratio of the two components deviates from the appropriate range, the product yield will still be adversely affected.

[0109] Furthermore, the comparison results between Example 1 and Comparative Example 6 confirm that using a two-stage air intake method is beneficial for improving product yield. If oxidant air is only introduced through the first air intake 15 without adding oxidant in the intermediate redistribution zone 14, the product yield is significantly poor.

[0110] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing 2,3,5-trimethylbenzoquinone, characterized in that, include: The reactants containing trimethylphenol, organic solvent and hydrochloric acid are circulated between a first catalytic reaction zone and a second catalytic reaction zone connected in series, wherein the reactants pass through the first catalytic reaction zone and the second catalytic reaction zone in sequence. When the reactants come into contact with the first catalytic reaction zone or before they come into contact, a first oxidant is introduced into the first catalytic reaction zone; when the reactants come into contact with the second catalytic reaction zone or before they come into contact, a second oxidant is introduced into the second catalytic reaction zone. The reactants exiting the second catalytic reaction zone are collected, and after selectively adding the trimethylphenol, they are returned to the upstream of the first catalytic reaction zone to repeat the cycle. The first catalytic reaction zone is filled with a first supported catalyst, the active components of which include copper and nickel, and the molar amount of copper is greater than the molar amount of nickel. The second catalytic reaction zone is filled with a second supported catalyst, the active components of which include copper and nickel, and the molar amount of copper is less than the molar amount of nickel. Both the first supported catalyst and the second supported catalyst use silica gel as the support. The first oxidant and the second oxidant are each independently selected from oxygen or an oxygen-containing mixture; Throughout the entire cycle, the mass content of trimethylphenol in the reactants entering the first catalytic reaction zone is controlled to be less than 12%, and the mass content of water is controlled to be 2% to 5%.

2. The method for preparing 2,3,5-trimethylbenzoquinone according to claim 1, characterized in that, The molar ratio of copper to nickel in the first supported catalyst is 1:(0.05~0.2); and / or, The molar ratio of copper to nickel in the second supported catalyst is 1:(2~3).

3. The method for preparing 2,3,5-trimethylbenzoquinone according to claim 1, characterized in that, The mass ratio of the active component to the support in the first supported catalyst and the second supported catalyst are independently (0.01~0.08):

1.

4. The method for preparing 2,3,5-trimethylbenzoquinone according to claim 1, characterized in that, The mass ratio of the first supported catalyst packed in the first catalytic reaction zone to the second supported catalyst packed in the second catalytic reaction zone is 1:(0.8~1.2).

5. The method for preparing 2,3,5-trimethylbenzoquinone according to claim 1, characterized in that, The oxygen volume flow rate entering the first catalytic reaction zone is less than or equal to the oxygen volume flow rate entering the second catalytic reaction zone.

6. The method for preparing 2,3,5-trimethylbenzoquinone according to claim 5, characterized in that, Both the first oxidant and the second oxidant are air, and the volume flow rate ratio of the first oxidant to the second oxidant is (0.2~1):

1.

7. The method for preparing 2,3,5-trimethylbenzoquinone according to claim 6, characterized in that, The inlet flow rate of the first oxidant is 4.5 Nm. 3 / h~15Nm 3 / h; and / or, The influent flow rate of the reactants in the first catalytic reaction zone is 1 m³ / s. 3 / h~3m 3 / h.

8. The method for preparing 2,3,5-trimethylbenzoquinone according to claim 1, characterized in that, The temperatures of the reactants entering the first catalytic reaction zone and the second catalytic reaction zone are controlled independently to be 75℃~95℃.

9. The method for preparing 2,3,5-trimethylbenzoquinone according to claim 1, characterized in that, The organic solvent is selected from one or more of n-butanol, n-pentanol, and n-hexanol, and the total mass ratio of the organic solvent to the trimethylphenol is (1~5):

1.

10. The method for preparing 2,3,5-trimethylbenzoquinone according to claim 1, characterized in that, The trimethylphenol is 2,3,6-trimethylphenol.

11. The method for preparing 2,3,5-trimethylbenzoquinone according to any one of claims 1 to 10, characterized in that, The preparation method is carried out using a reaction apparatus, which includes a trickle bed reactor, a circulating vessel, and a reflux condenser. The trickle bed reactor is provided with a first catalytic reaction zone and a second catalytic reaction zone arranged sequentially from top to bottom. The shell part above the first catalytic reaction zone is provided with a first air inlet for introducing the first oxidant and a feed inlet for introducing the reactants. The shell part between the first catalytic reaction zone and the second catalytic reaction zone is provided with a second air inlet for introducing the second oxidant. The shell part below the second catalytic reaction zone is provided with a discharge outlet. The circulating vessel is in fluid communication with the feed inlet of the trickle bed reactor through a circulation system. The circulation system includes a circulation pipeline and a circulation pump installed on the circulation pipeline. The circulation pipeline is provided with a trimethylphenol feed inlet. The reflux condenser is connected to the circulating vessel via a reflux pipeline system. The reflux condenser is configured to: condense and discharge the gaseous material entering the circulating vessel, and / or return a portion of the condensed material to the circulating vessel.

12. The method for preparing 2,3,5-trimethylbenzoquinone according to claim 11, characterized in that, First, reactants other than trimethylphenol are introduced into the circulating kettle for mixing. The mixed material is then sent into the trickling bed reactor through a circulating pipeline. The first oxidant and the second oxidant are introduced into the trickling bed reactor through the first air inlet and the second air inlet, respectively. The circulating kettle is heated until the material temperature in the circulating kettle reaches the preset temperature. Then, trimethylphenol is introduced through the trimethylphenol feeding port.

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