Preparation method of diacid compound

Abstract

The invention discloses a diacid compound preparation method, which comprises: mixing a cyclic organic matter solution with micro-nano inert polymer particles to obtain a mixed solution, introducing gas into the mixed solution to generate micron bubbles, forming a gas-water interface, and carrying out a bubbling reaction to obtain a diacid compound, the cyclic organic matter in the cyclic organic matter solution comprises one or more of cyclohexanone, cyclohexene, cyclohexane or cyclohexanol; a solvent in the cyclic organic matter solution comprises water. The cyclic organic matter is oxidized to generate the diacid compound by means of the special oxidation capacity of the microbubble gas-water interface and the contact electro-catalysis technology, the preparation method can be carried out at normal temperature and normal pressure, additional oxidizing agents and catalysts do not need to be added, and the method is environmentally friendly and low in preparation cost.

Description

Technical Field

[0001] This application relates to the field of organic synthesis technology, and in particular to a method for preparing a diacid compound. Background Technology

[0002] Adipic acid (AA), one of the world's most produced aliphatic dicarboxylic acids, plays an indispensable role in modern chemical industry. Its core industrial value lies primarily in its role as a key monomer in the synthesis of high-performance engineering plastic Nylon 66 (NAL6) through polycondensation. Furthermore, adipic acid is also an important raw material for the production of polyurethane elastomers, plasticizers, and lubricant base oils. In the food industry, adipic acid and its salts also hold a stable market share as acidity regulators. The huge market demand (global annual production exceeding 6 million tons) further highlights its irreplaceable industrial value. Therefore, developing efficient, economical, and environmentally friendly new methods for the synthesis of adipic acid, and continuously optimizing its production process, are core technical challenges that both academia and industry are jointly focusing on and striving to solve.

[0003] In industrial production, adipic acid is mainly synthesized from cyclohexane using a two-step method: the first step involves oxidizing cyclohexane to a mixture of cyclohexanone and cyclohexanol (KA oil) under an air atmosphere of 8-15 bar using a homogeneous Co / Mn catalyst; the second step involves oxidizing cyclohexane to a mixture of cyclohexanone and cyclohexanol (KA oil) under the catalysis of copper(II) salt and ammonium metavanadate using 50-60% nitric acid. KA oil is oxidized to adipic acid. However, using... The main drawback of using it as an oxidant is that it produces a large amount of nitrogen oxide byproducts, including potent greenhouse gases. Treating these byproducts requires additional measures. Emission reduction technologies, which in turn increase production costs.

[0004] Currently, researchers are dedicated to exploring novel oxidants and catalytic systems that can replace nitric acid. Methods with potential industrial applications mainly include the direct oxidation of cyclohexanone to adipic acid using oxygen or air, or the direct oxidation of cyclohexane to adipic acid in the presence of a catalyst. However, these methods still rely on large quantities of homogeneous or heterogeneous catalysts, and their cost and application complexity limit their economic viability. Hydrogen peroxide As a green oxidant, it has attracted much attention due to its high atom utilization and the fact that water is the only byproduct. For example, Mekala et al. used an iron-tungsten oxide catalyst containing mesoporous carbon to... The oxidation of cyclohexanone to adipic acid achieved a conversion rate of 93% and a selectivity of 87%. Other studies have used manganese(II) complex catalysts to achieve adipic acid yields exceeding 80%. Nevertheless, Oxidation methods still face challenges: The relatively high price, insufficient stability (especially under reaction conditions), and the indispensability of catalysts highlight the urgent need to develop more cost-effective and sustainable synthetic routes.

[0005] Currently, electrocatalytic synthesis of adipic acid, as a promising green alternative process, has shown significant potential in laboratory studies to convert biomass-based feedstocks (such as cyclohexanone or furfural) into high-value products using clean electricity under mild conditions. Its core advantage lies in eliminating dependence on high temperature, high pressure, and highly toxic corrosive nitric acid, and avoiding the risks associated with these processes. Emissions. However, this technology still faces multiple severe challenges before industrial application: the core dilemma lies in the difficulty of obtaining electrocatalysts that simultaneously possess high activity, high selectivity (precise control of six-electron oxidation to avoid the generation of byproducts such as succinic acid and glutaric acid), long-term stability, and low cost in strong oxidizing environments. Noble metal-based materials are expensive, while alternative materials have poor stability or selectivity. The reaction system itself is also complex, with efficient pathways often relying on potentially polluting bromide-mediated processes, while progress in exploring mediator-free direct oxidation is slow, and electrolytes (highly corrosive or inefficient in neutral / alkaline environments) and reactor design (such as mass transfer limitations) restrict performance improvement. Energy efficiency and economy are also worrying, with high overpotentials leading to relatively high energy consumption, and the low substrate concentration used to avoid competing reactions (such as oxygen evolution) reducing space-time yield. The separation and purification of efficient, low-energy-consumption products in complex reaction solutions (containing salts, solvents, and byproducts) is extremely difficult. These problems together lead to significant uncertainties in the scale-up and engineering implementation of this technology. Therefore, despite its attractiveness in terms of principle and environmental protection, the actual industrialization of electrocatalytic synthesis of adipic acid is still hampered by key issues such as catalyst performance bottlenecks, system complexity, and cost-effectiveness.

[0006] Therefore, developing a new method for synthesizing adipic acid without the need for external oxidants or catalysts and under normal temperature and pressure is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, this application provides a method for oxidizing cyclohexanone to adipic acid by utilizing the special oxidation ability of the microbubble gas-water interface and contact electrocatalysis technology.

[0008] This application provides a method for preparing a diacid compound, comprising:

[0009] A cyclic organic solution is mixed with inert polymer particles to obtain a mixture. The mixture is then aerated to generate microbubbles, forming a gas-water interface, and a bubbling reaction is carried out to obtain a diacid compound.

[0010] The cyclic organic compound in the cyclic organic compound solution includes one or more of cyclohexanone, cyclohexene, cyclohexane, or cyclohexanol;

[0011] The solvent in the cyclic organic compound solution includes water.

[0012] In some specific implementations, the bubble size of the bubbling reaction is 50 nm to 500 μm, the temperature of the bubbling reaction is 5 °C to 80 °C, and the time of the bubbling reaction is 10 s to 10 h.

[0013] In some specific implementations, the concentration of the cyclic organic compound in the cyclic organic compound solution is from 0.01 mg / mL to 100 mg / mL, and the concentration of the polymer in the mixture is from 0.01 mg / L to 100 mg / L.

[0014] In some specific implementations, the solvent in the cyclic organic solution further includes an organic solvent, which includes one or more of methanol, ethanol, acetonitrile, tetrahydrofuran, chloroform, or dimethyl sulfoxide; the mass ratio of the solvent to water is 1:(1-10).

[0015] In some specific implementations, the inert polymer particles include one or more of polytetrafluoroethylene, perfluoroethylene-propylene copolymer, nylon, rubber, or polyvinylidene fluoride.

[0016] In some specific implementations, the size of the polymer particles is from 1 μm to 1 mm.

[0017] In some specific implementations, the ventilated gas includes one or more of nitrogen, oxygen, air, hydrogen, helium, argon, carbon dioxide, or methane; the ventilated gas flow rate is from 0.01 L / min to 10 L / min.

[0018] In some specific implementations, the microbubbles are generated by one or more of the following methods: microfluidic chip channel pressure drop method, ultrasonic cavitation method, venturi tube jet fragmentation method, membrane dispersion method, energy input method, or chemical reaction method.

[0019] In some specific implementations, the bubbling reaction is detected using coupled mass spectrometry, which includes any one of low-resolution mass spectrometry, high-resolution mass spectrometry, or ultra-high-resolution mass spectrometry.

[0020] In some specific implementations, the detection methods for reaction products include, but are not limited to, one or more of mass spectrometry, chromatography, spectroscopy, and nuclear magnetic resonance. This application does not have any special requirements for the selection of detection methods for reaction products.

[0021] In some specific implementations, the bubbling reaction takes place in a Buchner funnel, and the venting gas enters through the lower end of the Buchner funnel; the pore size of the sand core of the Buchner funnel is 100 nm to 1 mm.

[0022] This application also provides an apparatus for preparing a diacid compound, comprising: a Buchner funnel, a flask connected to the bottom of the Buchner funnel, a flexible tube connected to a side branch of the flask, and gas being blown into the Buchner funnel through the flexible tube and the flask.

[0023] This application utilizes the unique oxidation capacity of the microbubble gas-water interface and contact electrocatalysis technology to oxidize cyclic organic compounds into diacid compounds. The preparation method can be carried out at room temperature and pressure without the need for additional oxidants and catalysts, which is in line with the concept of green synthesis. Moreover, it is environmentally friendly and has a low preparation cost.

[0024] The preparation method is a continuous and stable reaction process. Its good reaction persistence and linear response characteristics to time provide an important experimental foundation for its subsequent large-scale operation and show potential for scalable application. Attached Figure Description

[0025] Figure 1 A diagram of the apparatus for preparing diacid compounds based on microbubbles provided in this application;

[0026] Figure 2 This is a reaction pathway diagram for the oxidation of cyclohexanone to adipic acid at the air-water interface.

[0027] Figure 3 A pathway diagram for enhancing adipic acid production through contact electrocatalysis. Detailed Implementation

[0028] It should be understood that the expression “one or more of…” individually includes each of the objects described after the expression, as well as various different combinations of two or more of the described objects, unless otherwise understood from the context and usage. The expression “and / or” combined with three or more described objects should be understood to have the same meaning, unless otherwise understood from the context.

[0029] The terms “including,” “having,” or “containing,” including the use of their grammatical synonyms, should generally be understood as open-ended and non-restrictive, for example, not excluding other unstated elements or steps, unless otherwise specifically stated or understood from the context.

[0030] It should be understood that the order of steps or the sequence of actions is not important as long as this application remains operational. Furthermore, two or more steps or actions can be performed simultaneously.

[0031] The use of any and all instances or exemplary language such as “e.g.” or “include” in this document is intended merely to better illustrate the application and does not constitute a limitation on the scope of the application. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of this application.

[0032] Furthermore, the numerical ranges and parameters used to define this application are approximate values, and the relevant values ​​in the specific embodiments have been presented as precisely as possible. However, any numerical value inevitably contains standard deviations due to individual test methods. Therefore, unless otherwise explicitly stated, it should be understood that all ranges, quantities, values, and percentages used in this disclosure are modified with the word "approximately." Here, "approximately" generally means that the actual value is within plus or minus 10%, 5%, 1%, or 0.5% of a specific value or range.

[0033] Currently, most existing preparation methods focus on electrocatalysis and external hydrogen peroxide oxidation, but these methods require high energy consumption, catalysts, and reagent costs, making them difficult to industrialize.

[0034] This application provides a method for preparing a diacid compound, comprising:

[0035] A cyclic organic compound solution is mixed with a polymer to obtain a mixture. The mixture is then aerated to generate microbubbles, forming a gas-water interface, and a bubbling reaction is carried out to obtain a diacid compound.

[0036] The cyclic organic compound in the cyclic organic compound solution includes one or more of cyclohexanone, cyclohexene, cyclohexane, or cyclohexanol;

[0037] The solvent in the cyclic organic compound solution includes water.

[0038] This application presents a novel method for the synthesis of adipic acid based on the unique oxidizing properties of the microbubble gas-water interface. This method can be carried out at room temperature and pressure without the need for additional oxidants or catalysts. The spontaneously generated ·OH groups at the microbubble gas-water interface in this application... It is the key reactive species initiating the oxidation of cyclohexanone. The inherent high-intensity electric field at the gas-water interface and the local extreme pH environment it induces are important factors accelerating the reaction process. Furthermore, the introduction of contact electrocatalysis (CEC) can significantly increase the concentration of reactive oxygen species in the system, thereby effectively improving the synthesis efficiency of adipic acid. In summary, this application develops a novel strategy for the efficient and environmentally friendly preparation of high-value-added adipic acid and demonstrates the significant application potential of CEC-water microbubble coupling technology in the field of green oxidative synthesis. Moreover, the reaction in this application is a continuous and stable process. Its good reaction persistence and linear response to time provide an important experimental foundation for its subsequent large-scale operation, showing potential for scalable applications. The gas-water interface can also be in other forms, such as microdroplets and thin films.

[0039] This application first mixes a cyclic organic compound solution with a polymer to obtain a mixture. In some specific implementations, the concentration of the cyclic organic compound in the cyclic organic compound solution is from 0.01 mg / mL to 100 mg / mL, and can be 0.01 mg / mL, 0.05 mg / mL, 0.1 mg / mL, 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.8 mg / mL, 0.9 mg / mL, 1 mg / mL, 1.2 mg / mL, 1.4 mg / mL, 1.6 mg / mL, 1.8 mg / mL, 2 mg / mL, 5 mg / mL, 10 mg / mL, 15 mg / mL, 20 mg / mL, 30 mg / mL, 50 mg / mL, 60 mg / mL, 80 mg / mL, 90 mg / mL, 95 mg / mL, 100 mg / mL, etc. The concentration of the polymer in the mixture is from 0.01 mg / L to 100 mg / L, and can be 0.01 mg / mL, 0.05 mg / mL, 0.1 mg / mL, 0.2 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.8 mg / mL, 0.9 mg / mL, 1 mg / mL, 1.1 mg / mL, 1.2 mg / mL, 1.4 mg / mL, 1.6 mg / mL, 1.8 mg / mL, 2 mg / mL, 10 mg / mL, 20 mg / mL, 30 mg / mL, 50 mg / mL, 70 mg / mL, 80 mg / mL, 90 mg / mL, 95 mg / mL, or 100 mg / mL. In some specific implementations, the solvent in the cyclic organic compound solution further includes an organic solvent, including but not limited to one or more of methanol, ethanol, acetonitrile, tetrahydrofuran, chloroform, or dimethyl sulfoxide; the mass ratio of the solvent to water is 1:(1-10). In some specific implementations, the cyclic organic compound solution contains, but is not limited to, one or more of cyclohexanone, cyclohexene, cyclohexane, or cyclohexanol; the inert polymer particles contain, but are not limited to, one or more of polytetrafluoroethylene, perfluoroethylene-propylene copolymer, nylon, rubber, or polyvinylidene fluoride. In some specific implementations, the size of the polymer particles is from 1 μm to 1 mm.

[0040] This application then aerates the mixture to generate microbubbles, initiating a bubbling reaction to obtain the diacid compound. In some specific implementations, the bubble size of the bubbling reaction is from 50 nm to 500 μm, and can be 50 nm, 100 nm, 500 nm, or 800 μm. nm, 1μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 85μm, 90μm, 95μm, 100μm, 200μm, 400μm, 500μm, the bubbling reaction temperature is from 5℃ to 80℃, and can be 5℃, 10℃, 12℃, 14℃, 16℃, 18℃, 20℃, 21℃, 22℃, 24℃, 25℃, 26℃, 28℃, 30℃, 35℃, 40℃, 45℃, 50℃, 60℃, 70℃, 75℃, 80℃, the bubbling reaction time is from 10 s to 10 h, and can be 10s, 20s, 50s, 1min, 2min, 3min, 4min, 5min, 6h. min, 7 min, 8 min, 9 min, 10 min, 20 min, 40 min, 50 min, 80 min, 10 min, 120 min, 3 h, 5 h, 8 h, 10 h. ·OH and spontaneously generated at the microbubble air-water interface. It is the key active species initiating the oxidation of cyclohexanone; contact electrocatalysis can significantly increase the concentration of reactive oxygen species in the system, thereby effectively improving the synthesis efficiency of adipic acid. The process can be carried out at room temperature and pressure without the addition of additional oxidants and catalysts. Inert nitrogen gas is dispersed in the reaction solution (cyclohexanone 1 mg / mL; methanol / water = 1:3) through a sand core to generate microbubbles. ·OH and ·OH are generated in situ at the gas-water interface of the microbubbles. This process oxidizes cyclohexanone to adipic acid at room temperature without oxidants or catalysts. The main purpose of adding methanol to the system is to enhance the solubility of cyclohexanone, facilitating subsequent scale-up experiments. To monitor the reaction progress, the reaction solution was collected for high-resolution mass spectrometry analysis (TIMS-Q-TOF MS, -ESI mode) 3 minutes after the start of the bubbling reaction. The specific reaction pathway diagram is shown below. Figure 2 The advancement of this oxidation reaction mainly depends on the spontaneous generation of ·OH at the gas-water interface and through contact electrocatalysis, as well as the subsequent conversion of ·OH into ·OH. During the entire oxidation process, cyclohexanone first... Under the influence of the classic Baeyer-Villiger reaction, it is oxidized to ε-caprolactone. This reaction is one of the efficient methods in organic chemistry for converting ketones to esters. The resulting ε-caprolactone undergoes further oxidation... Under certain conditions, ring-opening occurs, transforming it into the intermediate 6-hydroxyhexanoic acid. Subsequently, the hydroxyl group in the 6-hydroxyhexanoic acid molecule is further... Oxidation ultimately transforms it into the target product, adipic acid. Continuous infusion... The mixture flows through a sintered glass core, where it is injected into the solution containing the reactants as microbubbles through the pores. These microbubbles rise and burst in the solution, forming a high-density gas-water interface in the liquid phase. After the reaction is complete, the reaction mixture in the Buchner funnel and flask is collected, and the target product is analyzed using high-resolution mass spectrometry.

[0041] In the oxidation of cyclohexanone to adipic acid, other physicochemical properties of the gas-water interface (such as...) Electric fields and extreme pH levels also play a promoting role. Studies have shown that... A magnitude-high electric field can serve as a novel type of "non-physical" catalyst: when the direction of the electric field aligns with the direction of electron rearrangement or dipole moment change during the reaction, it can significantly lower the reaction energy barrier and increase the reaction rate. Furthermore, the extreme pH conditions and anomalous dielectric constant exhibited by the interfacial region may also produce synergistic effects, jointly driving and accelerating the reaction.

[0042] The contact electrocatalytic mechanism enhances the formation of adipic acid in this application. Polytetrafluoroethylene (PTFE) powder was introduced into the cyclohexanone reaction solution, and the reaction system was terminated after ten minutes of continuous bubbling at a constant flow rate. The reaction solution was then subjected to solid-liquid separation (filtration to remove PTFE solids) followed by high-resolution mass spectrometry analysis (TIMS-Q-TOF MS, -ESI). Experimental results showed that, compared to the control group without PTFE, the mass spectrometric signal response of the product adipic acid was significantly enhanced in the PTFE-added reaction solution. This phenomenon confirms that the PTFE-induced CEC process can effectively enhance the synthesis of adipic acid. Figure 3 The potential pathway for CEC-enhanced adipic acid formation was further elucidated. During the bubbling process, the PTFE powder remained in continuous contact with water molecules and friction occurred at the solid-liquid interface. During this friction, water molecules lost electrons, thus generating ·OH and ·OH. , ·OH and The increase in the concentration of cyclohexanone promoted its oxidation conversion efficiency, thereby significantly increasing the production of adipic acid. The oxidation capacity of the microbubble gas-water interface and contact electrocatalysis jointly promoted the green synthesis of adipic acid from cyclohexanone.

[0043] In some specific implementations, the ventilated gas includes, but is not limited to, one or more of nitrogen, oxygen, air, hydrogen, helium, argon, carbon dioxide, or methane. This application does not have any special requirements for the selection of the ventilated gas. The ventilated gas flow rate is from 0.01 L / min to 10 L / min, and can be 0.01 L / min, 0.05 L / min, 0.1 L / min, 0.2 L / min, 0.3 L / min, 0.5 L / min, 0.6 L / min, 0.7 L / min, 0.8 L / min, 0.9 L / min, 1 L / min, 1.5 L / min, 1.8 L / min, 2 L / min, 3 L / min, 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, or 10 L / min.

[0044] In some specific implementations, the microbubble generation methods include, but are not limited to, one or more of the following: microfluidic chip channel pressure drop method, ultrasonic cavitation method, venturi tube jet fragmentation method, membrane dispersion method, energy input method (such as laser, electric heating) or chemical reaction method (such as carbonate acidification decomposition, hydrogen peroxide catalytic decomposition, water electrolysis). This application does not have any special requirements for the selection of microbubble generation methods.

[0045] Microfluidic chip channel pressure drop method utilizes precision-machined digital chips to precisely control the flow rates of the gas-liquid two-phase system via an injection pump. This causes the gas to converge and shear within a microchannel, initially forming bubbles. The pressure drop caused by abrupt changes in the channel cross-section further refines the bubbles. Ultrasonic cavitation method immerses an ultrasonic transducer in a liquid, applying a high-frequency sound field. The cavitation effect generated by the negative pressure phase of the sound waves initially generates cavitation bubbles, which are then broken up and captured into micro- and nano-bubbles by the energy of cavitation collapse. Venturi jet fragmentation method relies on a centrifugal pump driving liquid through the throat of a Venturi tube to create negative pressure, automatically ejecting gas. The gas is then broken up by intense turbulence and shear force in the diffusion section. Membrane dispersion method introduces pressurized gas into a special membrane with micro- and nano-sized pores. As the gas escapes from the pores, it is directly fragmented into tiny bubbles whose size is determined by the membrane pore size. Energy input method uses a high-speed shear homogenizer to violently agitate the gas-liquid mixture. Alternatively, the principle of thermal abrupt change can be used to suddenly reduce the pressure and increase the temperature of a pressurized saturated liquid, causing the dissolved gas to rapidly precipitate and form bubbles. Chemical reaction method allows the gas generated in situ by a chemical reaction (such as...) Micro- and nano-bubbles are formed directly in the liquid phase.

[0046] In some specific implementations, mass spectrometry data are acquired using captured ion mobility-quadrupole-time-of-flight mass spectrometry (TIMS-Q-TOF MS, Bruker). Prior to analysis, the instrument is calibrated using Tuning Mix calibration solution (Agilent Technologies) in Quadratic mode for the m / z 100-1000 Da mass range. Electrospray ionization conditions are as follows: negative mode, injection flow rate 10 μL / min, voltage 3500 V. Mass spectrometry parameters are set as follows: drying gas (… The flow rate was 3 L / min, the dry gas temperature was 200 °C, and the sampled mass range was 50–200 Da. For MS / MS experiments, the collision-induced dissociation (CID) energy was set between 10–30 eV. Data analysis was performed using Bruker Compass Data Analysis 5.0 software.

[0047] In some specific implementations, the bubbling reaction is detected using coupled mass spectrometry, including any one of low-resolution mass spectrometry, high-resolution mass spectrometry, or ultra-high-resolution mass spectrometry. In some specific implementations, the detection method for the reaction products includes one or more of mass spectrometry, chromatography, spectroscopy, and nuclear magnetic resonance. In some specific implementations, the bubbling reaction is carried out in a Büchner funnel, with the gas entering through the lower end of the funnel; the pore size of the Büchner funnel's sintered metal core is 100 nm to 1 mm.

[0048] This application also provides an apparatus for preparing diacid compounds, such as... Figure 1 As shown, the system includes: a Buchner funnel, a flask connected to the bottom of the Buchner funnel, and a flexible tube connected to a side branch of the flask. Gas is blown into the Buchner funnel through the flexible tube and the flask. Gas is also blown into the Buchner funnel from a gas cylinder via a polytetrafluoroethylene (PTFE) flexible tube through an opening at the side end of the funnel. The gas flow sequentially through the flask at the lower end of the funnel and the G4 sintered glass core within the Buchner funnel, ultimately entering the aqueous solution through the pores of the sintered glass core. At the pores, the gas forms micron-sized bubbles and is released into the liquid phase, significantly increasing the gas-water interface area of ​​the system. Figure 1 The right side shows an enlarged view of the reaction zone in the Buchner funnel. The solution appears milky white, clearly indicating the presence of densely distributed micron-sized bubbles in the liquid phase.

[0049] The microbubble interface reaction device designed in this application can generate microbubbles at low cost in a laboratory environment, and is easy to operate and build. Based on the special oxidation properties of the microbubble gas-water interface, a new method for the synthesis of adipic acid has been developed. This method can be carried out at room temperature and pressure without the need for additional oxidants and catalysts. The introduction of CEC can significantly increase the concentration of reactive oxygen species in the system, thereby effectively improving the synthesis efficiency of adipic acid. This method can also be used for the green oxidative synthesis of other organic molecules.

[0050] The present application is further illustrated below with reference to embodiments. The scope of protection of the present application is not limited to the following embodiments.

[0051] Example 1

[0052] This embodiment provides a method for preparing adipic acid based on microbubble gas-water interface and contact electrocatalysis, including:

[0053] Nitrogen gas was bubbled into the Buchner funnel from a gas cylinder through a polytetrafluoroethylene (PTFE) tube at a flow rate of 0.8 L / min. The gas flow passed sequentially through the flask at the bottom of the funnel and the G4 sintered glass core (5-10 μm pore size) within the Buchner funnel, ultimately entering the aqueous solution through the pores of the core to generate microbubbles. At the pores, nitrogen formed microbubbles of approximately 20 μm and released into the liquid phase. This apparatus was used for the bubbling reaction of cyclohexanone solution. Inert nitrogen gas was dispersed through the sintered glass core in 20 mL of the reaction solution (cyclohexanone 1 mg / mL; methanol / water = 1:3) to generate bubbles. PTFE powder at a concentration of 20 mg was introduced into the cyclohexanone reaction solution. After the reaction, the reaction solution was subjected to solid-liquid separation (filtration to remove PTFE solids) and then analyzed by high-resolution mass spectrometry (TIMS-Q-TOF MS, -ESI). When the content of adipic acid in the system basically no longer increases, the conversion rate of cyclohexanone in this reaction is calculated to be 65.7%, and the product selectivity of adipic acid is 70.3%.

[0054] The reaction pathway of cyclohexanone oxidation to adipic acid at the air-water interface is shown in the figure below. Figure 2 As shown, the spontaneously generated ·OH and ·OH at the microbubble gas-water interface The oxidation of cyclohexanone is initiated by the inherent high-intensity electric field at the air-water interface and the local extreme pH environment induced by it, which accelerates the reaction process. The pathway diagram of contact electrocatalysis enhancing adipic acid formation is shown below. Figure 3 As shown, contact electrocatalysis (CEC) can significantly increase the concentration of reactive oxygen species in the system, thereby effectively improving the synthesis efficiency of adipic acid. In summary, this application develops a novel, efficient, and environmentally friendly strategy for preparing high-value-added adipic acid and demonstrates the significant application potential of CEC-water microbubble coupling technology in the field of green oxidative synthesis. Compared with existing synthesis methods, this method is environmentally friendly, low-cost, and aligns with sustainable development strategies.

[0055] Example 2

[0056] This embodiment provides a method for preparing adipic acid based on microbubble gas-water interface and contact electrocatalysis, including:

[0057] Oxygen was introduced from a gas cylinder through a PTFE tube into the side opening of the Buchner funnel at a flow rate of 0.8 L / min. The gas flow passed sequentially through the flask at the bottom of the funnel and the G4 sintered glass core (5-10 μm pore size) within the Buchner funnel, ultimately entering the aqueous solution through the pores of the sintered glass core to generate microbubbles. At the pores, oxygen formed microbubbles of approximately 20 μm and released into the liquid phase. Oxygen was dispersed through the sintered glass core in 20 mL of the reaction solution (cyclohexanone 1 mg / mL; methanol / water = 1:3) to generate bubbles. PTFE powder at a concentration of 20 mg was introduced into the cyclohexanone reaction solution. After the reaction, the reaction solution underwent solid-liquid separation (filtration to remove PTFE solids) and was analyzed by high-resolution mass spectrometry (TIMS-Q-TOF MS, -ESI). When the adipic acid content in the system essentially ceased to increase, the calculated conversion rate of cyclohexanone in this reaction was 49.7%, and the product selectivity of adipic acid was 58.2%.

[0058] Example 3

[0059] This embodiment provides a method for preparing adipic acid based on microbubble gas-water interface and contact electrocatalysis, including:

[0060] Nitrogen gas was introduced from a gas cylinder through a polytetrafluoroethylene (PTFE) tube into the side opening of the Buchner funnel at a flow rate of 0.8 L / min. The gas flow passed sequentially through the flask at the bottom of the funnel and the G4 sintered glass core (5-10 μm pore size) within the Buchner funnel, ultimately entering the aqueous solution through the pores of the sintered glass core to generate microbubbles. At the pores, nitrogen formed microbubbles of approximately 20 μm and released into the liquid phase. Nitrogen gas was dispersed through the sintered glass core in 20 mL of the reaction solution (cyclohexanone 1 mg / mL; acetonitrile / water = 1:3) to generate bubbles. PTFE powder at a concentration of 20 mg was introduced into the cyclohexanone reaction solution. After the reaction, the reaction solution underwent solid-liquid separation (filtration to remove PTFE solids) and was analyzed by high-resolution mass spectrometry (TIMS-Q-TOF MS, -ESI). When the adipic acid content in the system essentially ceased to increase, the calculated conversion rate of cyclohexanone in this reaction was 70.6%, and the product selectivity of adipic acid was 73.3%.

[0061] Example 4

[0062] This embodiment provides a method for preparing adipic acid based on microbubble gas-water interface and contact electrocatalysis, including:

[0063] Nitrogen gas was introduced from a gas cylinder through a PTFE tube into the side opening of the Buchner funnel at a flow rate of 0.8 L / min. The gas flow passed sequentially through the flask at the bottom of the funnel and the G4 sintered glass core (5-10 μm pore size) within the Buchner funnel, ultimately entering the aqueous solution through the pores of the sintered glass core to generate microbubbles. At the pores, nitrogen formed microbubbles of approximately 20 μm and released into the liquid phase. Nitrogen gas was dispersed through the sintered glass core in 20 mL of the reaction solution (cyclohexanone 1 mg / mL; methanol / water = 1:3) to generate bubbles. 20 mg of FEP powder was introduced into the cyclohexanone reaction solution. After the reaction, the reaction solution underwent solid-liquid separation (filtration to remove FEP solids) and was analyzed by high-resolution mass spectrometry (TIMS-Q-TOF MS, -ESI). When the adipic acid content in the system essentially ceased to increase, the calculated conversion rate of cyclohexanone in this reaction was 64.3%, and the product selectivity of adipic acid was 69.4%.

[0064] Example 5

[0065] This embodiment provides a method for preparing adipic acid based on microbubble gas-water interface and contact electrocatalysis, including:

[0066] Microbubble generators (NANO-RESEARCH-LF1500) based on the dissolved gas release principle were used to generate 30-40 μm microbubbles. Nitrogen gas was connected to the microbubble generator via a pipeline. A 500 mL reaction solution (cyclohexanone 1 mg / mL; methanol / water = 1:3) was prepared in a beaker provided with the device, and 500 mg of PTFE particles were added simultaneously. The device was turned on, and 30-40 μm microbubbles were generated in the beaker for the reaction. After the reaction, the reaction solution was subjected to solid-liquid separation (filtration to remove PTFE solids) and then analyzed by high-resolution mass spectrometry (TIMS-Q-TOF MS, -ESI). When the content of adipic acid in the system essentially no longer increased, the conversion rate of cyclohexanone in this reaction was calculated to be 66.4%, and the product selectivity of adipic acid was 72.1%.

[0067] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and application concept of this application, should be included within the scope of protection of this application.

Claims

1. A method for preparing a diacid compound, characterized in that, include: A cyclic organic compound solution is mixed with inert polymer particles to obtain a mixture. The mixture is then aerated to generate microbubbles, and a bubbling reaction is carried out to obtain a diacid compound. The cyclic organic compound in the cyclic organic compound solution includes one or more of cyclohexanone, cyclohexene, cyclohexane, or cyclohexanol; The solvent in the cyclic organic compound solution includes water.

2. The preparation method according to claim 1, characterized in that, The bubble size of the bubbling reaction is 50 nm to 500 μm, the temperature of the bubbling reaction is 5 °C to 80 °C, and the time of the bubbling reaction is 10 s to 10 h.

3. The preparation method according to claim 1, characterized in that, The concentration of the cyclic organic compound in the solution is from 0.01 mg / mL to 100 mg / mL, and the concentration of the polymer in the mixture is from 0.01 mg / L to 100 mg / L.

4. The preparation method according to claim 1, characterized in that, The solvent in the cyclic organic solution further includes an organic solvent, which includes one or more of methanol, ethanol, acetonitrile, tetrahydrofuran, chloroform or dimethyl sulfoxide; the mass ratio of the organic solvent to water is 1:(1-10).

5. The preparation method according to claim 1, characterized in that, The inert polymer particles include one or more of polytetrafluoroethylene, perfluoroethylene-propylene copolymer, nylon, rubber, or polyvinylidene fluoride.

6. The preparation method according to claim 1, characterized in that, The size of the inert polymer particles is from 1 μm to 1 mm.

7. The preparation method according to claim 1, characterized in that, The ventilated gas includes one or more of nitrogen, oxygen, air, hydrogen, helium, argon, carbon dioxide, or methane; the ventilated gas flow rate is from 0.01 L / min to 10 L / min.

8. The preparation method according to claim 1, characterized in that, The microbubbles are generated by one or more of the following methods: microfluidic chip channel pressure drop method, ultrasonic cavitation method, venturi tube jet fragmentation method, membrane dispersion method, energy input method, or chemical reaction method.

9. The preparation method according to claim 1, characterized in that, The bubbling reaction is detected using coupled mass spectrometry, which includes any one of low-resolution mass spectrometry, high-resolution mass spectrometry, or ultra-high-resolution mass spectrometry. The detection methods for reaction products include one or more of mass spectrometry, chromatography, spectroscopy, or nuclear magnetic resonance.

10. The preparation method according to claim 1, characterized in that, The bubbling reaction is carried out in a Buchner funnel, and the gas being vented enters through the lower end of the Buchner funnel; the pore size of the sand core of the Buchner funnel is 100 nm to 1 mm.

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