Continuous centrifugal electrolysis process and device for the synthesis of 2-methyl-1,4-naphthoquinone

Abstract

The application discloses a continuous centrifugal electrolysis process and device for synthesizing 2-methyl-1,4-naphthoquinone. The application utilizes a flow separation electrolytic cell to cyclically electrolytically oxidize a cerous methanesulfonate-methanesulfonic acid solution to form a solution rich in ceric methanesulfonate; the solution rich in ceric methanesulfonate is continuously fed into a reactor, and in the reactor, the solution reacts with beta-methylnaphthalene to generate 2-methyl-1,4-naphthoquinone; during the reaction, an oil-water mixture in the reactor is continuously extracted into a centrifugal extractor to separate the oil phase and the water phase, the separated oil phase is fed back into the reactor, and the separated water phase is fed into the flow separation electrolytic cell to be electrolytically oxidized to regenerate Ce 4+ The application realizes efficient regeneration and reuse of cerium ions, reduces the amount of electrolyte and improves the reaction yield, and effectively reduces the process cost of scale-up.

Description

Technical Field

[0001] This invention relates to the field of 2-methyl-1,4-naphthoquinone synthesis technology, specifically to a continuous centrifugal electrolysis process and apparatus for synthesizing 2-methyl-1,4-naphthoquinone, which can centrifuge and recover electrolyte for cyclic electrolysis of cerium salt to indirectly mediate the synthesis of 2-methyl-1,4-naphthoquinone. Background Technology

[0002] Vitamin K3, also known as sodium menadione bisulfite, is an important fat-soluble vitamin with physiological functions such as promoting the synthesis of clotting factors and participating in human calcium metabolism. It is widely used in pharmaceutical preparations, animal feed additives, and related health products.

[0003] In industrial production, vitamin K3 is usually prepared by an addition reaction with sodium bisulfite, with 2-methyl-1,4-naphthoquinone as the key intermediate.

[0004] Currently, the industrial preparation of 2-methyl-1,4-naphthoquinone commonly uses β-methylnaphthalene as a raw material, employing chromic anhydride or dichromate as oxidants in a strongly acidic medium for liquid-phase oxidation. This process route has advantages such as mature reaction conditions, relatively simple process flow, and wide availability of raw materials, and therefore has been widely used for a considerable period. However, this type of chromium-containing oxidation process inevitably generates large amounts of waste liquid and residue containing hexavalent or trivalent chromium during production, resulting in high treatment costs and serious harm to the environment and ecosystem.

[0005] With increasingly stringent environmental regulations, the discharge and disposal of chromium-containing wastewater are subject to strict restrictions, putting traditional chromium salt oxidation processes under increasing compliance pressure in industrial applications. There is an urgent need to develop cleaner and more environmentally friendly alternative technologies.

[0006] To address the aforementioned issues, several methods for preparing 2-methyl-1,4-naphthoquinone without using chromium salts have been proposed in recent years. These methods include oxidation reactions using peroxides, molecular oxygen, or other metal oxidation systems, or the introduction of novel oxidation techniques such as electrochemistry and photochemistry. However, these methods still suffer from problems in practical applications, such as insufficient reaction selectivity, numerous side reactions, complex equipment, high energy consumption, or difficulty in achieving continuous scale-up. Therefore, a mature process that can be widely promoted in industry has not yet been developed.

[0007] On the other hand, some studies have proposed using a cerium ion system in acidic media for indirect electrochemical oxidation, i.e., using Ce... 4+ As an oxidant, β-methylnaphthalene is oxidized to 2-methyl-1,4-naphthoquinone, while Ce generated in the reaction is simultaneously removed by electrolysis. 3+ Regenerated into Ce 4+This allows for the recycling of cerium ions. Theoretically, this method avoids chromium salt pollution and offers certain environmental advantages. However, such processes often require a high volume ratio (typically 3:1) between the aqueous electrolyte and the oil-phase feedstock, resulting in a large electrolyte consumption and solution volume. This not only increases raw material consumption and operating costs but also negatively impacts subsequent product separation, solvent recovery, and wastewater treatment. These factors significantly limit the widespread application of this method in the industrial production of vitamin K3.

[0008] Therefore, how to significantly reduce the amount of electrolyte or the volume of electrolyte phase in the electrochemical oxidation system while ensuring the efficiency of β-methylnaphthalene oxidation reaction and the selectivity of 2-methyl-1,4-naphthoquinone formation, so as to achieve efficient recycling of the cerium ion system and reduce the overall process cost, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] To address the aforementioned technical problems and shortcomings in the field, this invention provides a continuous centrifugal electrolysis process and apparatus for synthesizing 2-methyl-1,4-naphthoquinone, which solves the problem of excessive electrolyte consumption in the indirect electrolytic oxidation of β-methylnaphthalene by cerium ions in an acidic medium.

[0010] The specific technical solution is as follows: In a first aspect, the present invention provides a continuous centrifugal electrolysis apparatus for synthesizing 2-methyl-1,4-naphthoquinone, comprising an anode electrolyte storage tank, an anode pump, a flow-separated electrolysis cell, a reactor, and a centrifugal extractor capable of continuously separating oil and aqueous phases; The reactor is equipped with a material inlet, a circulation inlet, and a circulation outlet. The circulation outlet is connected to the centrifugal extractor inlet via a circulation pump. The oil phase outlet of the centrifugal extractor is connected to the circulation inlet, and the aqueous phase outlet of the centrifugal extractor is connected to the anode electrolyte storage tank. A flow-divided electrolytic cell includes an anode plate, a cathode plate, and an H-type electrode disposed between the anode plate and the cathode plate. + Ion exchange membrane; anode and cathode plates are connected to the positive and negative terminals of a (DC) power supply, respectively; the anode plate has an anode cavity; the anode cavity inlet is connected to the anode pump, and the outlet is connected to the inlet of a three-way switching valve; the two outlets of the three-way switching valve are connected to the anode electrolyte storage tank and the reactor material inlet, respectively; the anode electrolyte storage tank is connected to the anode pump; the anode electrolyte storage tank initially contains a cerium sulfonate-methanesulfonic acid solution; H + An ion-exchange membrane separates the electrolyte in the anode chamber from the electrolyte in the cathode chamber. In the anode chamber, H... + Can pass through H + The ion exchange membrane enters the cathode cavity, H + Ion exchange membranes can prevent Ce from being removed. 4+ From the anode cavity to the cathode cavity.

[0011] The above-mentioned continuous centrifugal electrolysis device for synthesizing 2-methyl-1,4-naphthoquinone is used as follows: First, the three-way switching valve is switched to connect the anode chamber to the anode electrolyte storage tank. At this time, the anode electrolyte storage tank, anode pump, and anode chamber form an anode electrolyte electrolytic oxidation circulation loop. The flow-divided electrolytic cell is used to force the circulation electrolysis and oxidation of the cerium methanesulfonate-methanesulfonic acid solution to form a solution enriched with high cerium methanesulfonate. Then, the three-way switching valve is switched to connect the anode chamber to the reactor material inlet. At this time, β-methylnaphthalene is already in the reactor. The solution enriched with high cerium methanesulfonate is continuously fed into the reactor. In the reactor, it is stirred and mixed with β-methylnaphthalene to undergo an oxidation reaction to generate 2-methyl-1,4-naphthoquinone. During this period, the circulation pump continuously draws the oil-water mixture in the reactor into a centrifugal extractor for oil-water phase separation. The separated oil phase is discharged from the oil phase outlet and sent back to the reactor through the circulation inlet to form an oil phase circulation. The separated water phase is discharged from the water phase outlet and sent to the anode electrolyte storage tank. Under the action of the anode pump, it further enters the anode chamber of the flow-divided electrolytic cell for electrolytic oxidation and regeneration of Ce. 4+ The material is then sent back to the reactor through the material inlet, forming a water phase cycle.

[0012] The reaction progress can be determined by sampling and testing the materials in the reactor. When the reaction endpoint is reached, all materials in the reactor are discharged from the circulation outlet through the circulation pump and enter the centrifugal extractor to complete the separation of oil and water phases. The water phase is discharged to the anode electrolyte storage tank through the water phase outlet and can be used again for the next batch of 2-methyl-1,4-naphthoquinone synthesis. The oil phase is discharged and collected as a product from the oil phase outlet.

[0013] In this invention, the cerium methanesulfonate-methanesulfonic acid solution can be prepared by mixing methanesulfonic acid (concentration can be 70 wt%, etc.) and cerium carbonate (Ce2(CO3)3·8.5H2O). It is preferable to filter the cerium methanesulfonate-methanesulfonic acid solution before use to remove insoluble solid impurities. Since the prepared cerium methanesulfonate-methanesulfonic acid solution usually contains a small amount of insoluble white solid impurities, if it is directly introduced into the electrolytic cell without filtration, these residual impurities will enter the electrolytic cell flow channels, causing blockage and consequently reducing current efficiency.

[0014] In some embodiments, the cathode plate has a cathode cavity, which is connected to a cathode pump and a cathode electrolyte storage tank to form a cathode electrolyte circulation loop.

[0015] In some embodiments, the cathode electrolyte tank initially contains a cerium methanesulfonate-methanesulfonic acid solution. The cerium methanesulfonate-methanesulfonic acid solution initially contained in the cathode electrolyte tank may be the same as or different from the cerium methanesulfonate-methanesulfonic acid solution initially contained in the anode electrolyte tank.

[0016] In some embodiments, the reactor is a continuously stirred jacketed vessel. Further, the jacket of the continuously stirred jacketed vessel can store a heat exchange medium to control the reaction temperature for the oxidation reaction to produce 2-methyl-1,4-naphthoquinone within the vessel. Even further, a circulating heating tank is connected to the outside of the jacket, and the heat exchange medium circulates between the jacket and the circulating heating tank.

[0017] The purpose of the forced circulation method in this invention is to improve the fluidity of the electrolyte and accelerate the homogenization of the concentration of each component in the electrolyte, thereby avoiding the precipitation of cerium methanesulfonic acid crystals due to excessively high local concentrations.

[0018] In some preferred embodiments, the distance between the anode plate and the cathode plate is 2~30 mm, preferably 5~10 mm. If the distance between the anode and cathode plates is too large, the turbulence effect of the electrolyte is poor, and stagnant areas are easily formed in the electrode cavity, or even dead zones and electrolyte back mixing occur, which in turn affects the current efficiency; if the distance between the anode and cathode plates is too small, the processing precision and installation requirements of the electrolysis equipment are significantly increased, increasing the difficulty of equipment manufacturing and installation.

[0019] In some embodiments, H + The ion exchange membrane is a Nafion 117 proton exchange membrane.

[0020] In a second aspect, the present invention provides the application of the continuous centrifugal electrolysis apparatus described in the first aspect for the synthesis of 2-methyl-1,4-naphthoquinone.

[0021] Thirdly, the present invention provides a continuous centrifugal electrolysis process for synthesizing 2-methyl-1,4-naphthoquinone, comprising: A solution enriched with high cerium methanesulfonic acid is formed by circulating electrolysis of cerium methanesulfonic acid-methanesulfonic acid solution in a flow-divided electrolytic cell. A solution enriched with high-cerium methanesulfonic acid is continuously fed into a reactor, where it undergoes an oxidation reaction with β-methylnaphthalene to generate 2-methyl-1,4-naphthoquinone. During this process, the oil-water mixture is continuously extracted from the reactor and fed into a centrifugal extractor for oil-water phase separation. The separated oil phase is returned to the reactor, while the separated aqueous phase is sent to a flow-divided electrolytic cell for electrolytic oxidation regeneration of Ce. 4+ It is then fed into the reactor to form an aqueous phase circulation.

[0022] In some embodiments, in the initial cerium methanesulfonate-methanesulfonic acid solution, Ce 3+ The concentration is 0.5~1.0 mol / L, for example 0.6 mol / L, 0.7 mol / L, etc. When Ce... 3+ At higher concentrations, Ce is generated after electrolysis. 4+ A corresponding increase in concentration is beneficial for enhancing the reactivity in subsequent oxidation reactions; however, as Ce increases...4+ Increased cerium concentration may lead to the precipitation of high-valent cerium solid compounds during electrolysis, thereby enhancing the scouring effect on the electrodes, reducing electrode lifespan, and adversely affecting the transport, storage, and use of the electrolyte. Conversely, when Ce... 3+ When the concentration is too low, the amount of electrolyte needs to be increased, which leads to an increase in the size of the equipment required for production and a corresponding increase in investment costs.

[0023] In some embodiments, in the initial cerium methanesulfonate-methanesulfonic acid solution, H + The concentration is 1.0~3.0 mol / L, such as 1.5 mol / L, 2.0 mol / L, etc. If the acidity is too high, the electrode potential of cerium ions will increase, leading to a decrease in current efficiency. At the same time, the requirements for the corrosion resistance of the equipment will be significantly increased, thereby increasing the equipment investment cost. If the acidity is too low, the conversion rate and selectivity of the subsequent oxidation reaction will decrease, which is not conducive to the efficient preparation of 2-methyl-1,4-naphthoquinone.

[0024] In some embodiments, in solutions enriched with high cerium methanesulfonate, Ce 4+ The concentration is 0.3~0.6 mol / L, for example 0.4 mol / L, 0.5 mol / L, etc.

[0025] In some preferred embodiments, the current density for circulating electrolysis of the cerium methanesulfonic acid-methanesulfonic acid solution using a flow-divided electrolyzer is 50~150 mA / cm². 2 For example, 60 mA / cm 2 Etc. Under otherwise identical conditions, excessively high current density will lead to an increase in oxygen concentration near the electrode, thereby increasing Ce... 4+ The reduced current efficiency during the electrolytic oxidation process is detrimental to the effective regeneration of cerium ions; while excessively low current density will reduce electrolysis efficiency, prolong reaction time, and affect overall production efficiency.

[0026] In this invention, the oxidation reaction to generate 2-methyl-1,4-naphthoquinone can be carried out according to methods known in the art.

[0027] In some preferred embodiments, Ce in the solution enriched with cerium methanesulfonate 4+ and Ce 3+ The ratio of the total molar amount to the molar amount of β-methylnaphthalene fed is (3~10):1, for example, 4.5:1, etc.

[0028] In some preferred embodiments, β-methylnaphthalene is pre-added to the reactor in the form of an oil phase solution. The solvent in the oil phase solution includes, but is not limited to, at least one of dichloroethane, cyclohexane, etc.

[0029] In some preferred embodiments, the feed volume ratio of the solution enriched with high cerium methanesulfonic acid to the oil phase solution is 1:(0.8~10).

[0030] In some embodiments, the oxidation reaction to generate 2-methyl-1,4-naphthoquinone is carried out at a temperature of 40~70°C, for example, 65°C.

[0031] In some preferred embodiments, the continuous centrifugal electrolysis process for synthesizing 2-methyl-1,4-naphthoquinone employs the continuous centrifugal electrolysis apparatus for synthesizing 2-methyl-1,4-naphthoquinone described in the first aspect.

[0032] This invention solves the technical problem of large electrolyte consumption and difficulty in meeting the requirements of industrial production in existing processes by centrifugally separating and recovering aqueous electrolyte, thereby effectively reducing the production cost of 2-methyl-1,4-naphthoquinone.

[0033] Compared with the prior art, the beneficial effects of this invention are as follows: 1. Because the oxidant in this invention can be regenerated and recycled in the system, it not only effectively saves resources but also significantly reduces environmental pollution.

[0034] 2. In the process of cerium ion electrolytic regeneration, the present invention adopts a centrifugal recovery and recycling method for aqueous electrolyte, which significantly reduces the required electrolyte volume and simplifies the process.

[0035] 3. Maintaining a high concentration of cerium methanesulfonic acid solution through in-situ electrolysis results in a higher reaction yield compared to traditional batch reactors, which is more conducive to the industrial production of 2-methyl-1,4-naphthoquinone. Attached Figure Description

[0036] Figure 1 This is a flowchart of a continuous centrifugal electrolysis process and apparatus for synthesizing 2-methyl-1,4-naphthoquinone according to the present invention.

[0037] Figure 2 This is a schematic diagram of the flow-separated electrolytic cell in a continuous centrifugal electrolysis apparatus for synthesizing 2-methyl-1,4-naphthoquinone according to the present invention.

[0038] Figure 3 This is a schematic diagram of a continuous centrifugal electrolysis device for synthesizing 2-methyl-1,4-naphthoquinone according to the present invention. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0040] Example 1: See Figures 1 to 3 This embodiment provides a continuous centrifugal electrolysis process and apparatus for synthesizing 2-methyl-1,4-naphthoquinone. For example... Figure 3 As shown, the continuous centrifugal electrolysis apparatus for synthesizing 2-methyl-1,4-naphthoquinone includes an anode electrolyte storage tank 10, an anode pump 12, a flow-divided electrolytic cell 11, a reactor 17, and a centrifugal extractor 13 capable of continuously separating oil and aqueous phases. The reactor 17 is a continuous stirred jacketed vessel with a material inlet, a circulation inlet, and a circulation outlet. The circulation outlet is connected to the inlet of the centrifugal extractor 13 via a circulation pump 15. The oil phase outlet of the centrifugal extractor 13 is connected to the circulation inlet, and the aqueous phase outlet of the centrifugal extractor 13 is connected to the anode electrolyte storage tank 10. The centrifugal extractor 13 is connected to a power supply and control device 14. The reactor 17 is connected to a stirring motor 16. A circulating heating tank 8 is connected to the jacket of the reactor 17. The jacket stores a heat exchange medium, which circulates between the jacket and the circulating heating tank 8 to control the reaction temperature for the oxidation reaction to produce 2-methyl-1,4-naphthoquinone within the reactor. Figure 2 As shown, the flow-separated electrolytic cell 11 includes a top plate 1, an anode partition 2, an anode plate 3, and an H plate arranged sequentially. + The reactor consists of an ion exchange membrane 4, a cathode plate 5, a cathode separator 6, and a base plate 7. Anode plate 3 and cathode plate 5 are connected to the positive and negative terminals of power supply 9, respectively. Anode plate 3 has an anode cavity. The inlet of the anode cavity is connected to anode pump 12, and the outlet is connected to the inlet of a three-way switching valve. The two outlets of the three-way switching valve are connected to the material inlets of anode electrolyte storage tank 10 and reactor 17, respectively. Anode electrolyte storage tank 10 is connected to anode pump 12. Cathode plate 5 has a cathode cavity, which connects to the cathode pump and cathode electrolyte storage tank to form a cathode electrolyte circulation loop. Initially, both anode electrolyte storage tank 10 and cathode electrolyte storage tank are filled with a cerium sulfonate-methanesulfonic acid solution. + Ion exchange membrane 4 separates the electrolyte in the anode chamber and the cathode chamber. In the anode chamber, H... + Can pass through H + Ion exchange membrane 4 enters the cathode cavity, H + Ion exchange membrane 4 can prevent Ce 4+ From the anode cavity to the cathode cavity. H + Ion exchange membrane 4 is a Nafion 117 proton exchange membrane.

[0041] The aforementioned continuous centrifugal electrolysis apparatus for synthesizing 2-methyl-1,4-naphthoquinone can be used to synthesize 2-methyl-1,4-naphthoquinone.

[0042] The continuous centrifugal electrolysis process for synthesizing 2-methyl-1,4-naphthoquinone employs the aforementioned continuous centrifugal electrolysis apparatus, including: First, switch the three-way switching valve to connect the anode chamber to the anode electrolyte storage tank 10. At this time, the anode electrolyte storage tank 10, the anode pump 12, and the anode chamber form an anode electrolyte electrolytic oxidation circulation loop. The flow-divided electrolytic cell 11 is used to force the circulation electrolytic oxidation of the cerium methanesulfonic acid-methanesulfonic acid solution to form a solution enriched with high cerium methanesulfonic acid. Then, switch the three-way switching valve to connect the anode chamber to the material inlet of reactor 17. At this time, β-methylnaphthalene is already in reactor 17. The solution enriched with high cerium methanesulfonic acid is continuously fed into reactor 17. In reactor 17, it reacts with β-methylnaphthalene to generate 2-methyl-1,4-naphthoquinone. During this process, the circulation pump 15 continuously draws the oil-water mixture in reactor 17 into the centrifugal extractor 13 for oil-water phase separation. The separated oil phase is discharged from the oil phase outlet and sent back to reactor 17 through the circulation inlet to form an oil phase circulation. The separated water phase is discharged from the water phase outlet and sent to the anode electrolyte storage tank 10. Under the action of the anode pump 12, it further enters the anode chamber of the flow-divided electrolytic cell 11 for electrolytic oxidation regeneration of Ce. 4+ The material is then sent back to reactor 17 via the material inlet, forming a water phase cycle.

[0043] The reaction process is judged by sampling and testing the materials in reactor 17. When the reaction endpoint is reached, all materials in reactor 17 are discharged from the circulation outlet through circulation pump 15 and enter centrifugal extractor 13 to complete the separation of oil phase and water phase. The water phase is discharged to the anode electrolyte storage tank 10 through the water phase outlet and can be used again for the next batch of 2-methyl-1,4-naphthoquinone synthesis. The oil phase is discharged and collected as a product from the oil phase outlet.

[0044] The cerium methanesulfonate-methanesulfonic acid solution is prepared by mixing methanesulfonic acid (concentration can be 70 wt% etc.) and cerium carbonate (Ce2(CO3)3·8.5H2O). Before use, the cerium methanesulfonate-methanesulfonic acid solution is filtered to remove insoluble solid impurities.

[0045] Example 2: The continuous centrifugal electrolysis process and apparatus for synthesizing 2-methyl-1,4-naphthoquinone as described in Example 1 were used.

[0046] Take 600 mL containing Ce 3+ Concentration of 0.6 mol / L, H + A 1.5 mol / L cerium methanesulfonic acid-methanesulfonic acid solution was used as the anolyte, and 200 mL of an electrolyte with the same composition was used as the catholyte. Electrolysis was carried out in a flow-separated electrolytic cell 11, with forced circulation between the flow-separated electrolytic cell 11 and the anolyte storage tank 10 via an anode pump 12. The electrolysis time was 1 h. The resulting solution enriched with cerium methanesulfonic acid contained Ce. 4+The concentration was 0.4~0.5 mol / L. The electrolysis operating parameters were as follows: cell voltage 3.0~3.3 V; anode was a size-stabilized anode DSA (RuO2 / IrO2-Ti); cathode was Pt; electrode area was 100 cm². 2 The distance between the anode and cathode plates is 5 mm; the current density is 60 mA / cm². 2 The electrolysis temperature is 25℃.

[0047] In this embodiment, a 0.1 M β-methylnaphthalene oil phase solution (800 mL) was used, and β-methylnaphthalene was reacted with cerium salt electrolyte Ce. 4+ +Ce 3+ The total molar ratio was 1:4.5. β-methylnaphthalene and a pre-electrolyzed solution enriched with cerium methanesulfonate (obtained by 1 h of electrolysis) were stirred in reactor 17 at 1000 RPM using a stirring motor 16, and heated to 65°C using a circulating heating tank 8. Simultaneously, a portion of the mixture in reactor 17 was used to recover the aqueous electrolyte phase via a centrifugal extractor 13, and the cerium methanesulfonate was oxidized and regenerated in a flow-separated electrolytic cell 11. The electro-oxidized and regenerated cerium methanesulfonate enriched solution, along with the oil phase feed and product, were returned to reactor 17 for a 2 h circulation reaction. After the reaction, the reaction solution was separated to obtain 2-methyl-1,4-naphthoquinone. The conversion rate of β-methylnaphthalene was 94.4%, and the yield of 2-methyl-1,4-naphthoquinone was 73.4%.

[0048] After completing the oxidation of β-methylnaphthalene and separating it to obtain 2-methyl-1,4-naphthoquinone, the aqueous solution obtained by centrifugation is electrolyzed again according to the above electrolysis process to obtain a solution enriched with high cerium methanesulfonate, which is recycled for the next batch of 2-methyl-1,4-naphthoquinone synthesis.

[0049] Table 1 shows the conversion rate of β-methylnaphthalene and the yield of 2-methyl-1,4-naphthoquinone in multiple cyclic experiments.

[0050] Table 1 After β-methylnaphthalene oxidation and separation to obtain 2-methyl-1,4-naphthoquinone, the changes in the total cerium salt concentration in the electrolyte during the cycling process were detected using inductively coupled plasma optical emission spectrometry (ICP-OES) of the aqueous solution obtained after centrifugation, and the changes in the acid concentration in the electrolyte were detected using a pH meter. Table 2 lists the total cerium salt concentration and H2O concentration in the aqueous solution after different cycles. + Concentration results.

[0051] Table 2 After multiple cycles, the concentrations of cerium salt and acid in the electrolyte system did not change significantly; furthermore, repeated recycling of the electrolyte did not significantly affect the reaction yield. These results demonstrate that the centrifugal electrolysis process and apparatus of this invention can achieve efficient recovery and recycling of the electrolyte, and exhibits good operational stability.

[0052] In summary, this invention achieves efficient regeneration and reuse of cerium ions by centrifugally recovering aqueous electrolyte, reducing electrolyte consumption and increasing reaction yield, thus effectively reducing the process cost for scaling up.

[0053] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A continuous centrifugal electrolysis apparatus for synthesizing 2-methyl-1,4-naphthoquinone, characterized in that, Includes an anode electrolyte storage tank, an anode pump, a flow-divided electrolyzer, a reactor, and a centrifugal extractor capable of continuously separating the oil and aqueous phases; The reactor is equipped with a material inlet, a circulation inlet, and a circulation outlet. The circulation outlet is connected to the centrifugal extractor inlet via a circulation pump. The oil phase outlet of the centrifugal extractor is connected to the circulation inlet, and the aqueous phase outlet of the centrifugal extractor is connected to the anode electrolyte storage tank. A flow-divided electrolytic cell includes an anode plate, a cathode plate, and an H-type electrode disposed between the anode plate and the cathode plate. + Ion exchange membrane; anode and cathode plates are connected to the positive and negative terminals of the power supply, respectively; the anode plate has an anode cavity; the inlet of the anode cavity is connected to the anode pump, and the outlet is connected to the inlet of a three-way switching valve; the two outlets of the three-way switching valve are connected to the anode electrolyte storage tank and the reactor material inlet, respectively; the anode electrolyte storage tank is connected to the anode pump; the anode electrolyte storage tank initially contains cerium sulfonate-methanesulfonic acid solution; H + An ion-exchange membrane separates the electrolyte in the anode chamber from the electrolyte in the cathode chamber. In the anode chamber, H... + Can pass through H + The ion exchange membrane enters the cathode cavity, H + Ion exchange membranes can prevent Ce from being removed. 4+ From the anode cavity to the cathode cavity.

2. The continuous centrifugal electrolysis apparatus for synthesizing 2-methyl-1,4-naphthoquinone according to claim 1, characterized in that, The reactor is a continuously stirred jacketed vessel.

3. The continuous centrifugal electrolysis apparatus for synthesizing 2-methyl-1,4-naphthoquinone according to claim 1, characterized in that, The distance between the anode plate and the cathode plate is 2~30 mm, preferably 5~10 mm.

4. The continuous centrifugal electrolysis apparatus for synthesizing 2-methyl-1,4-naphthoquinone according to claim 1, characterized in that, H + The ion exchange membrane is a Nafion 117 proton exchange membrane.

5. The application of the continuous centrifugal electrolysis apparatus for synthesizing 2-methyl-1,4-naphthoquinone according to any one of claims 1 to 4.

6. A continuous centrifugal electrolysis process for synthesizing 2-methyl-1,4-naphthoquinone, characterized in that, include: A solution enriched with high cerium methanesulfonic acid is formed by circulating electrolysis of cerium methanesulfonic acid-methanesulfonic acid solution in a flow-divided electrolytic cell. A solution enriched with high-cerium methanesulfonic acid is continuously fed into a reactor, where it undergoes an oxidation reaction with β-methylnaphthalene to generate 2-methyl-1,4-naphthoquinone. During this process, the oil-water mixture is continuously extracted from the reactor and fed into a centrifugal extractor for oil-water phase separation. The separated oil phase is returned to the reactor, while the separated aqueous phase is sent to a flow-divided electrolytic cell for electrolytic oxidation regeneration of Ce. 4+ It is then fed into the reactor to form an aqueous phase circulation.

7. The continuous centrifugal electrolysis process for synthesizing 2-methyl-1,4-naphthoquinone according to claim 6, characterized in that, In the initial cerium methanesulfonate-methanesulfonic acid solution, Ce 3+ Concentration of 0.5~1.0 mol / L, H + The concentration is 1.0~3.0 mol / L; In solutions enriched with high cerium methanesulfonic acid, Ce 4+ The concentration is 0.3~0.6 mol / L; The current density for circulating electrolysis of cerium methanesulfonic acid-methanesulfonic acid solution using a flow-divided electrolytic cell is 50~150 mA / cm². 2 .

8. The continuous centrifugal electrolysis process for synthesizing 2-methyl-1,4-naphthoquinone according to claim 6, characterized in that, Ce in solutions enriched with cerium methanesulfonate 4+ and Ce 3+ The ratio of the total molar amount to the molar amount of β-methylnaphthalene fed is (3~10):1; β-methylnaphthalene is added to the reactor in the form of an oil phase solution beforehand; The solvent in the oil phase solution includes at least one of dichloroethane and cyclohexane; The volume ratio of the solution enriched with high cerium methanesulfonic acid to the oil phase solution is 1:(0.8~10); The oxidation reaction to produce 2-methyl-1,4-naphthoquinone occurs at temperatures between 40 and 70 °C.

9. The continuous centrifugal electrolysis process for synthesizing 2-methyl-1,4-naphthoquinone according to claim 6, characterized in that, The continuous centrifugal electrolysis process for synthesizing 2-methyl-1,4-naphthoquinone uses the continuous centrifugal electrolysis apparatus for synthesizing 2-methyl-1,4-naphthoquinone as described in any one of claims 1 to 4.

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