Microreactor and method for synthesizing hydroquinone compounds using the same

Abstract

The present invention provides a microreactor and a method for synthesizing diphenol compounds using the same, belonging to the field of fine chemical synthesis. The microreactor includes a micro-packed bed reactor or a microchannel reactor, the micro-packed bed reactor includes a micro-packed bed reactor inlet and a micro-packed bed reaction tube connected in sequence; the microchannel reactor includes a micro-channel reactor inlet and a microchannel reaction tube connected in sequence; the micro-packed bed reactor inlet or the microchannel reactor inlet includes a gas-liquid mixing unit. During synthesis, the reaction liquid of the phenol compound and the oxidizing reaction gas are introduced into the microreactor for oxidation reaction to obtain an intermediate product, a benzoquinone compound, which is then hydrogenated, evaporated, and crystallized to obtain the intermediate product; the diphenol compound includes hydroquinone and / or tert-butylhydroquinone. The reactor of the present application has a simple structure, promotes gas-liquid mass transfer, reduces the reactor volume, and greatly improves the efficiency and safety of the process.

Description

Technical Field

[0001] The present invention relates to the field of fine chemical synthesis, in particular to a microreactor and a method for synthesizing hydroquinone compounds using the same. Background Art

[0002] Hydroquinone compounds, particularly hydroquinone (HQ) and tert-butylhydroquinone (TBHQ), are an important class of chemicals, widely used in the rubber, food, cosmetics, and pharmaceutical industries, with demand increasing annually. However, conventional preparation methods suffer from significant pollution, complex processes, and numerous reaction byproducts. The production of hydroquinone compounds using phenolic compounds, however, is a hot topic of research due to its low raw material costs and minimal waste production. The hydroxylation of phenolic compounds produces both catechol compounds (accounting for 60%) and hydroquinone compounds. Improving the selectivity of hydroquinone compounds, coupled with the relatively small market for catechol compounds, severely limits hydroquinone production capacity. The oxidation of phenolic compounds offers a shorter process flow and allows for the exclusive production of hydroquinone compounds, making it a preferred route for hydroquinone production. However, in terms of production processes, most oxidation systems present explosive limits, making it difficult to obtain approval for production using conventional technologies and equipment, according to national safety regulations.

[0003] In recent years, the use of micro-reaction technology to achieve safe and efficient oxidation has gradually received attention. Corning, Shandong Haomai and others have developed different types of microreactors, including tubular and flat-plate reactors, which can improve the safety of processes such as oxidation. There are also patent reports on oxidation processes in microchannels. For example, CN212011142U discloses a technology for heat exchange of alcohol microchannel oxidation evaporation reforming, which effectively improves the safety of the oxidation process through efficient heat exchange. However, at this stage, the microscale mechanism of action of heterogeneous slurry catalytic reaction systems containing particulate matter in microchannel reactors is still unclear. Compared with liquid-liquid and gas-liquid reactions, gas-liquid-solid reaction systems with catalyst particles are more complicated. For oxidation reactions with reaction times of tens of minutes or even hours, there is no clear regulatory mechanism for the continuous transfer behavior and catalyst particle deposition behavior in microchannels.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this application is to provide a microreactor and a method for synthesizing hydroquinone compounds using the same to solve the above problems.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] A microreactor includes a micro-packed bed reactor or a microchannel reactor, wherein the micro-packed bed reactor includes a micro-packed bed reactor inlet and a micro-packed bed reaction tube connected in sequence; the microchannel reactor includes a microchannel reactor inlet and a microchannel reaction tube connected in sequence, characterized in that the micro-packed bed reactor inlet or the microchannel reactor inlet includes a gas-liquid mixing unit, and the gas-liquid mixing unit is T-shaped, Y-shaped, hydraulic focusing type or coaxial ring tube type.

[0008] Preferably, the inner diameter of the micro-packed bed reaction tube is about 2 to 8 mm, more preferably 2 to 4 mm.

[0009] Preferably, the microchannel reaction tube has one or more spiral and / or turning structures. More preferably, the spiral and / or turning structures include inversion structures or enhanced mixing structures.

[0010] Preferably, the gas-liquid mixing unit inlet size is about 0.1 to 3 mm, more preferably 0.6 to 2.5 mm; the microchannel reaction tube inner diameter is about 0.1 to 10 mm, more preferably 1 to 10 mm; the spiral curvature is about 0.01 to 0.1 m, more preferably 0.02 to 0.04 m. The gas-liquid inlet size ratio is 1:1.2 to 1:1.4.

[0011] Preferably, a double emulsion generating device is provided downstream of the gas-liquid mixing unit.

[0012] Furthermore, the inlet of the double emulsion generator is sleeved onto the outlet of the gas-liquid mixing unit, and the outlet of the double emulsion generator is connected to the micro-packed bed reaction tube or microchannel reaction tube. The double emulsion generator body is also provided with several inlet ports for an inert oil phase. By introducing an inert oil phase, a countercurrent circulation shearing effect is generated to form a double emulsion structure, which can further promote gas-liquid mass transfer. The inert oil phase is preferably an oil phase such as silicone oil or fluorinated liquid that is non-reactive or miscible with the raw materials.

[0013] Preferably, the outlet of the gas-liquid mixing unit is a constricted pipe orifice, and its horizontal angle α is 5° to 45°, more preferably 10° to 30°.

[0014] Preferably, the inlet of the double emulsion generating device is a constricted pipe orifice, and the angle β between the inlet and the vertical direction is 30° to 60°, more preferably 30° to 45°.

[0015] Preferably, the inlet of the double emulsion generating device is nested with the outlet of the gas-liquid mixing unit.

[0016] Preferably, the microreactor is made of polymer, Hastelloy, stainless steel, silicon carbide or a mixture thereof. More preferably, the inlet of the microreactor is made of polytetrafluoroethylene, and the rear end reaction tube is made of silicon carbide.

[0017] Using this microreactor as the core device can enhance gas-liquid contact and mass transfer, accelerate the overall oxidation reaction process, reduce reactor volume, and improve equipment safety. The inlet mixing size and gas-liquid flow ratio are crucial for the gas-liquid flow pattern. Furthermore, the helical curvature of the downstream piping in the microchannel reactor is directly related to the stability of the gas-liquid flow pattern. This parameter can be further optimized while meeting basic mass transfer requirements.

[0018] The present invention also provides a method for synthesizing hydroquinone compounds using the above-mentioned microreactor: a phenol compound, a main catalyst and a co-catalyst are dissolved in an organic solvent to form a reaction solution, a reducing agent is added, and the pH value is adjusted so that the metal in the reaction solution is approximately in a sol state; the reaction solution and an oxidizing reaction gas are introduced into a microchannel reactor to form a block flow pattern and an oxidation reaction is carried out at a certain temperature and pressure; the two-phase fluid passes through the tubular microchannel reactor once or circulates multiple times, and the total residence time is controlled according to the reaction progress; after gas-liquid separation, an oxidation product suspension is obtained; the suspension is filtered to recover the main catalyst and co-catalyst in the filter cake; the liquid product is then distilled or stripped to remove the organic solvent to obtain an intermediate product, a benzoquinone compound; the benzoquinone compound is added to methanol to prepare a hydrogenation reaction solution; hydrogen is introduced into a stirred tank or fixed bed reactor at a certain temperature and pressure for hydrogenation reaction; the product is subjected to evaporation, crystallization, and other treatments to obtain the hydroquinone compound, and the hydroquinone compound is a high-purity crystal.

[0019] Preferably, the hydroquinone compound includes hydroquinone and / or tert-butylhydroquinone.

[0020] Preferably, the phenolic compound includes phenol and / or 2-tert-butylphenol.

[0021] Preferably, the organic solvent is one or a mixture of acetonitrile, acetone, methanol, ethanol, propanol, n-butanol or tetrahydrofuran.

[0022] The present invention also provides another method for synthesizing hydroquinone compounds using the above-mentioned microreactor: a phenol compound is dissolved in an organic solvent to form a reaction liquid; the reaction liquid and an oxidizing reaction gas are introduced into a micro-packed bed reactor loaded with a molecular sieve catalyst to form a block flow pattern and conduct an oxidation reaction; after gas-liquid separation, the liquid product is distilled or stripped to obtain an intermediate product, a benzoquinone compound; the benzoquinone compound is hydrogenated, evaporated, and crystallized to obtain the hydroquinone compound.

[0023] Preferably, the hydroquinone compound includes hydroquinone and / or tert-butylhydroquinone.

[0024] Preferably, the phenolic compound includes phenol and / or 2-tert-butylphenol.

[0025] Preferably, the organic solvent is one or a mixture of acetonitrile, acetone, methanol, ethanol, propanol, n-butanol or tetrahydrofuran.

[0026] Preferably, the molecular sieve catalyst is a vanadium-supported mesoporous molecular sieve (V-HMS mesoporous molecular sieve).

[0027] When the hydroquinone compound is hydroquinone, the phenol compound is phenol, and the intermediate p-benzoquinone compound is p-benzoquinone, the synthesis route is:

[0028]

[0029] When the hydroquinone compound is tert-butylhydroquinone, the phenol compound is 2-tert-butylphenol, and the intermediate product p-benzoquinone compound is tert-butyl-p-benzoquinone, the synthesis route is:

[0030]

[0031] Optionally, the main catalyst is one or a mixture of Cu(NO3)2·3H2O, CuCl2·2H2O, AgCl, CuO-ZnO, CuI, CuO, FeCl3 or CrCl3.

[0032] Optionally, the co-catalyst is one or a mixture of LiCl, LiCl·H2O, NaCl, KCl, NaNO3, KNO3 or CaCl2.

[0033] Preferably, the main catalyst CuO-ZnO is prepared by co-precipitation method, with Na2CO3 as precipitant, the copper-zinc mass ratio is 2:1, and the copper source and zinc source are Cu(NO3)2·3H2O and Zn(NO3)2·6H2O respectively.

[0034] Preferably, the molar ratio of the main catalyst to the phenol compound is 0.1 to 0.5:1; the molar ratio of the co-catalyst to the phenol compound is 0.1 to 1.0:1.

[0035] Optionally, the reducing agent is one or a mixture of ethanolamine, diethanolamine, hydrazine hydrate or hydroxylamine, and the molar ratio of the reducing agent to the main catalyst is 0.25-2.0.

[0036] Preferably, the pH value is adjusted to 3-6.

[0037] Preferably, the molar ratio of the main catalyst to the co-catalyst is 0.5-5:1.

[0038] Furthermore, the phenol compound raw material has a concentration of approximately 0.1 to 5 mol / L; the flow rate of the reaction liquid is approximately 0.01 to 1 L / min; the oxidation reaction gas is oxygen, air, or a combination thereof; and the flow ratio of the oxidation reaction gas to the reaction liquid is approximately 10:1 to 100:1. Preferably, the flow ratio of the oxidation reaction gas to the reaction liquid is 15:1 to 100:1; further preferably, the flow ratio of the oxidation reaction gas to the reaction liquid is 50:1 to 70:1.

[0039] Furthermore, the oxidation reaction temperature is about 0-150°C; the oxidation reaction pressure is about 0.5-3.0 MPa; and the oxidation reaction time is about 1-120 min. Preferably, when the hydroquinone compound is tert-butylhydroquinone, the oxidation reaction temperature is 120-140°C, the oxidation reaction pressure is 0.8-1.2 MPa, and the oxidation reaction time is 10-40 min. Preferably, when the hydroquinone compound is hydroquinone, the oxidation reaction temperature is 60-100°C, the oxidation reaction pressure is 2.5-3.0 MPa, and the oxidation reaction time is 30-50 min.

[0040] Furthermore, the hydrogenation reaction temperature is about 50-200°C; the hydrogenation reaction pressure is about 1.0-5.0 MPa; and the hydrogenation reaction time is about 2-4 hours. Preferably, when the hydroquinone compound is tert-butylhydroquinone, the hydrogenation reaction temperature is 150-160°C, the hydrogenation reaction pressure is 1.6-1.8 MPa, and the hydrogenation reaction time is 3 hours. Preferably, when the hydroquinone compound is hydroquinone, the hydrogenation reaction temperature is 80-110°C, the hydrogenation reaction pressure is 1.8-2.0 MPa, and the hydrogenation reaction time is 3 hours.

[0041] The microreactor provided by the application, by controlling the initial dispersion state of gas and liquid, forming a gas-liquid block fluid, or fully contacting the gas, liquid and solid in a micro-packed bed, relative to traditional kettle and bubble reactors, the gas-liquid contact area can be increased by about 100 times or more, and an inert oil phase is introduced through a double emulsion generating device to produce a countercurrent circulation shearing effect, forming a double emulsion structure, which can further promote gas-liquid mass transfer. In a microchannel reactor, combined with a high-curvature reaction line design, the gas-liquid aggregation and phase separation in the flow process are reduced, and the gas-liquid efficient mass transfer state is always maintained under the condition of a longer residence time, reducing mass transfer resistance. At the same time, the mass transfer time in the synthesis time can be greatly shortened, so the residence time can be reduced, the reactor volume is reduced, and the amount of liquid under the explosion limit conditions is also reduced synchronously, and the efficiency and safety of the process are greatly improved.

[0042] The present invention uses the microreactor as an oxidation reactor to accelerate the overall synthesis process and develop a new technology for efficiently and safely synthesizing hydroquinone compounds. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0044] Figure 1 Schematic diagram of the gas-liquid mixing unit structure of the microreactor of the present invention, wherein a) is a T-type structure, b) is a Y-type structure, c) is a hydraulic focusing structure, and d) is a coaxial ring tube structure;

[0045] Figure 2 This is a schematic structural diagram of a double emulsion generating device that can be optionally connected to the gas-liquid mixing unit in the present invention;

[0046] Figure 3 Schematic diagram of the spiral structure of the reaction tube of the microchannel reactor in the present invention;

[0047] Figure 4 Schematic diagram of the structure of the micro-packed bed reactor in the present invention.

[0048] Reference numerals:

[0049] 1-Gas-liquid mixing unit; 2-Double emulsion generating device. DETAILED DESCRIPTION

[0050] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0051] The main catalyst CuO-ZnO involved in the following examples was prepared by co-precipitation method, with Na2CO3 as the precipitant, the copper-zinc mass ratio of 2:1, and the copper source and zinc source were Cu(NO3)-2·3H2O and Zn(NO3)2·6H2O, respectively.

[0052] In the following examples, mixtures or mixed solvents without specifying the ratio relationship represent that they can be mixed in any ratio.

[0053] Example 1

[0054] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in (d), the gas-liquid mixing unit is a coaxial ring tube type, the inner diameter of the reaction gas channel is 0.2 mm, the inner diameter of the reaction liquid and the downstream microchannel reaction tube are both 1 mm, and the contact angle between the inner wall of the coaxial ring tube and the liquid phase is greater than 60°. In other embodiments, the gas-liquid mixing unit can also be as follows Figure 1 The T-type shown in a) Figure 1 Y-type as shown in b) or as Figure 1 The hydraulic focusing type shown in c).

[0055] like Figure 3 As shown, the microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.02m.

[0056] In this embodiment, the material of the microchannel reactor is silicon carbide.

[0057] A method for synthesizing tert-butylhydroquinone using the above-mentioned microchannel reactor:

[0058] 1) Ethanol, n-butanol, and tetrahydrofuran are used as organic solvents, and ethanolamine and hydrazine hydrate are used as reducing agents to prepare an oxidation reaction solution, wherein the concentration of the raw material 2-tert-butylphenol is 0.1 mol / L, CuO-ZnO and CrCl3 are selected as the main catalyst, and KCl and CaCl2 are selected as the co-catalyst; the molar ratio of the main catalyst to the 2-tert-butylphenol is 0.15, the molar ratio of the co-catalyst to the 2-tert-butylphenol is 0.1, and the molar ratio of the reducing agent to the main catalyst is 0.5.

[0059] 2) The oxidation reaction liquid and pure oxygen were introduced into the microchannel reactor at a flow rate of 0.01 L / min for the oxidation reaction liquid and 0.1 L / min for the pure oxygen gas, forming a block flow pattern;

[0060] 3) Under the conditions of a reaction temperature of 20° C. and a reaction pressure of 1.0 MPa, the two-phase fluid stayed in the microchannel reactor for 120 minutes, and after gas-liquid phase separation, an oxidation product suspension was obtained;

[0061] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and subjecting the filtrate to rectification to remove the organic solvent and obtain the intermediate product tert-butyl-p-benzoquinone. The conversion rate of the raw material 2-tert-butylphenol is 100%, and the yield of the intermediate product is 68.2%;

[0062] 5) Dissolve tert-butyl-p-benzoquinone in methanol to prepare a hydrogenation reaction solution. In a fixed bed reactor, the reaction temperature is 80°C, the reaction pressure is 3.0 MPa, and the feed space velocity is 1.0 h -1The hydrogenation reaction was carried out for 2.5 hours. The product was evaporated and crystallized to obtain tert-butylhydroquinone crystals with a purity of 99.1%. The total yield of the product was 68.1%.

[0063] Example 2

[0064] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in a), the gas-liquid mixing unit is T-shaped, the inner diameter of the reaction gas channel is 2 mm, the inner diameter of the reaction liquid channel is 2.4 mm, and the inner diameter of the downstream microchannel reaction tube is 4 mm.

[0065] The microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.2m. The material of the microchannel reactor is silicon carbide.

[0066] A method for synthesizing tert-butylhydroquinone using the above-mentioned microchannel reactor:

[0067] 1) using acetonitrile and acetone as organic solvents to prepare an oxidation reaction solution, wherein the raw material 2-tert-butylphenol has a concentration of 0.1 mol / L, diethanolamine and hydroxylamine are used as reducing agents, CuO and CrCl3 are selected as main catalysts, and the molar ratio of each to 2-tert-butylphenol is 0.15; NaCl and LiCl are selected as co-catalysts, and the molar ratio of each to 2-tert-butylphenol is 0.15, and the molar ratio of the reducing agent to the main catalyst is 0.5;

[0068] 2) The oxidation reaction liquid and pure oxygen were introduced into the microchannel reactor at a flow rate of 0.02 L / min for the oxidation reaction liquid and 0.2 L / min for the pure oxygen gas, forming a block flow pattern;

[0069] 3) Under the conditions of a reaction temperature of 20° C. and a reaction pressure of 1.0 MPa, the two-phase fluid stayed in the microchannel reactor for 80 minutes, and after gas-liquid phase separation, an oxidation product suspension was obtained;

[0070] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and subjecting the filtrate to distillation to remove the organic solvent and obtain the intermediate product tert-butyl-p-benzoquinone. The conversion rate of the raw material 2-tert-butylphenol is 100%, and the yield of the intermediate product is 69.7%;

[0071] 5) Dissolve tert-butyl-p-benzoquinone in methanol to prepare a hydrogenation reaction solution. In a fixed bed reactor, the reaction temperature is 150°C, the reaction pressure is 5.0 MPa, and the feed space velocity is 1.0 h -1 , hydrogenation reaction for 3h, the product was evaporated and crystallized to obtain tert-butylhydroquinone crystals with a purity of 99.2%, and the total yield of the product was 69.6%.

[0072] Example 3

[0073] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in b), the gas-liquid mixing unit is Y-shaped, the inner diameter of the reaction gas channel is 1 mm, the inner diameter of the reaction liquid channel is 1.2 mm, and the inner diameter of the downstream microchannel reaction tube is 2 mm.

[0074] The microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.01m.

[0075] In this embodiment, Figure 2 As shown, a double emulsion generator 2 is also provided downstream of the gas-liquid mixing unit 1. The inlet of the double emulsion generator 2 and the outlet of the gas-liquid mixing unit 1 are both constricted orifices, with the inlet of the double emulsion generator 2 nested within the outlet of the gas-liquid mixing unit 1. The outlet of the double emulsion generator 2 communicates with the reaction tube. The double emulsion generator 2 is provided with two inert oil phase inlets. By introducing silicone oil, a countercurrent circulation shearing effect is generated, forming a double emulsion structure that further promotes gas-liquid mass transfer.

[0076] The horizontal angle α of the narrowed pipe opening at the outlet of the gas-liquid mixing unit 1 is 30°. The angle β of the narrowed pipe opening at the inlet of the double emulsion generating device 2 with the vertical direction is 45°.

[0077] In this embodiment, the material of the microchannel reactor is silicon carbide.

[0078] A method for synthesizing tert-butylhydroquinone using the above-mentioned microchannel reactor:

[0079] 1) using acetonitrile and acetone as organic solvents to prepare an oxidation reaction solution, wherein the raw material 2-tert-butylphenol has a concentration of 0.5 mol / L, CuO and CrCl3 are selected as main catalysts, and the molar ratio of CuO and CrCl3 to 2-tert-butylphenol is 0.15; NaCl and LiCl are selected as co-catalysts, and the molar ratio of NaCl and LiCl to 2-tert-butylphenol is 0.3; diethanolamine and hydroxylamine are used as reducing agents, and the molar ratio of reducing agent to main catalyst is 1.0;

[0080] 2) introducing the oxidation reaction liquid and pure oxygen into a microchannel reactor at a flow rate of 0.2 L / min for the oxidation reaction liquid and 4 L / min for the pure oxygen gas to form a block flow pattern, and introducing silicone oil through a double emulsion generator to form a double emulsion structure to further promote gas-liquid mass transfer;

[0081] 3) Under the conditions of a reaction temperature of 120° C. and a reaction pressure of 0.8 MPa, the two-phase fluid resides in the microchannel reactor for 30 minutes, and a liquid-phase oxidation product suspension is obtained after phase separation of gas, liquid, and silicone oil;

[0082] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and subjecting the filtrate to distillation or stripping to remove the organic solvent and obtain the intermediate product tert-butyl-p-benzoquinone. The conversion rate of the raw material 2-tert-butylphenol is 99%, and the yield of the intermediate product is 71.7%;

[0083] 5) Dissolve tert-butyl-p-benzoquinone in methanol to prepare a hydrogenation reaction solution. In a fixed bed reactor, the reaction temperature is 150°C, the reaction pressure is 5.0 MPa, and the feed space velocity is 1.0 h -1 , hydrogenation reaction for 4 hours, the product was evaporated and crystallized to obtain tert-butylhydroquinone crystals with a purity of 99.1%, and the total yield of the product was 71.5%.

[0084] Example 4

[0085] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in (c), the gas-liquid mixing unit is a hydraulic focusing structure, the inner diameter of the reaction gas channel is 2 mm, the inner diameter of the reaction liquid channel is 2.4 mm, and the inner diameter of the downstream microchannel reaction tube is 6 mm.

[0086] The microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.2m. The material of the microchannel reactor is silicon carbide.

[0087] A method for synthesizing tert-butylhydroquinone using the above-mentioned microchannel reactor:

[0088] 1) using acetonitrile and acetone as organic solvents to prepare an oxidation reaction solution, wherein the raw material 2-tert-butylphenol has a concentration of 0.5 mol / L, CuO and CrCl3 are selected as main catalysts, and the molar ratio of CuO and CrCl3 to 2-tert-butylphenol is 0.15; NaCl and LiCl are selected as co-catalysts, and the molar ratio of NaCl and LiCl to 2-tert-butylphenol is 0.3; diethanolamine and hydroxylamine are used as reducing agents, and the molar ratio of reducing agent to main catalyst is 1.0;

[0089] 2) The oxidation reaction liquid and pure oxygen were introduced into the microchannel reactor, with the reaction liquid flow rate of the two side channels being 0.5 L / min and the pure oxygen gas flow rate being 20 L / min, forming a block flow pattern;

[0090] 3) Under the conditions of a reaction temperature of 20° C. and a reaction pressure of 1.0 MPa, the two-phase fluid stayed in the microchannel reactor for 60 minutes, and after gas-liquid phase separation, an oxidation product suspension was obtained;

[0091] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and stripping the filtrate to remove the organic solvent to obtain the intermediate product tert-butyl-p-benzoquinone. The conversion rate of the raw material 2-tert-butylphenol is 95%, and the yield of the intermediate product is 68.6%;

[0092] 5) Dissolve tert-butyl-p-benzoquinone in methanol to prepare a hydrogenation reaction solution. In a fixed bed reactor, the reaction temperature is 50°C, the reaction pressure is 5.0 MPa, and the feed space velocity is 1.0 h -1 , hydrogenation reaction for 2h, evaporation and crystallization of the product to obtain tert-butylhydroquinone crystals with a purity of 99.2%, and the total yield of the product is 68.1%.

[0093] Example 5

[0094] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in (c), the gas-liquid mixing unit is a hydraulic focusing structure, the inner diameter of the reaction gas channel is 2 mm, the inner diameter of the reaction liquid channel is 2.8 mm, and the inner diameter of the downstream microchannel reaction tube is 8 mm.

[0095] The microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.2m. The material of the microchannel reactor is silicon carbide.

[0096] A method for synthesizing tert-butylhydroquinone using the above-mentioned microchannel reactor:

[0097] 1) using acetonitrile and acetone as organic solvents to prepare an oxidation reaction solution, wherein the raw material 2-tert-butylphenol has a concentration of 1.5 mol / L, CuO and KCl are selected as main catalysts, and the molar ratio of CuO and KCl to 2-tert-butylphenol is 0.3; NaCl and LiCl are selected as co-catalysts, and the molar ratio of NaCl and LiCl to 2-tert-butylphenol is 0.9; diethanolamine and hydroxylamine are used as reducing agents, and the molar ratio of reducing agent to main catalyst is 1.5;

[0098] 2) The oxidation reaction liquid and pure oxygen were introduced into the microchannel reactor, with the reaction liquid flow rate of the two side channels being 0.5 L / min and the pure oxygen gas flow rate being 40 L / min, forming a block flow pattern;

[0099] 3) Under the conditions of a reaction temperature of 20°C and a reaction pressure of 1.0 MPa, the two-phase fluid stayed in the microchannel reactor for 73 minutes, and after gas-liquid phase separation, an oxidation product suspension was obtained;

[0100] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and subjecting the filtrate to rectification to remove the organic solvent and obtain the intermediate product tert-butyl-p-benzoquinone. The conversion rate of the raw material 2-tert-butylphenol is 93%, and the yield of the intermediate product is 65.1%;

[0101] 5) Dissolve tert-butyl-p-benzoquinone in methanol to prepare a hydrogenation reaction solution. In a fixed bed reactor, the reaction temperature is 200°C, the reaction pressure is 1.0 MPa, and the feed space velocity is 1.0 h -1 , hydrogenation reaction for 2h, evaporation and crystallization of the product to obtain tert-butylhydroquinone crystals with a purity of 99.2%, and the total yield of the product is 64.6%.

[0102] Example 6

[0103] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in a), the gas-liquid mixing unit is T-shaped, the inner diameter of the reaction gas channel is 2 mm, the inner diameter of the reaction liquid channel is 2.4 mm, and the inner diameter of the downstream microchannel reaction tube is 4 mm.

[0104] The microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.2m. The material of the microchannel reactor is stainless steel.

[0105] A method for synthesizing tert-butylhydroquinone using the above-mentioned microchannel reactor:

[0106] 1) using acetonitrile and acetone as organic solvents to prepare an oxidation reaction solution, wherein the raw material 2-tert-butylphenol has a concentration of 1.5 mol / L, CuO and CrCl3 are selected as main catalysts, and the molar ratio of CuO and CrCl3 to 2-tert-butylphenol is 0.3; NaCl and LiCl are selected as co-catalysts, and the molar ratio of NaCl and LiCl to 2-tert-butylphenol is 0.9; diethanolamine and hydroxylamine are used as reducing agents, and the molar ratio of reducing agent to main catalyst is 1.5;

[0107] 2) introducing the oxidation reaction liquid and pure oxygen into the microchannel reactor at a flow rate of 0.8 L / min for the oxidation reaction liquid and 32 L / min for the pure oxygen gas to form a block flow pattern;

[0108] 3) Under the conditions of a reaction temperature of 20° C. and a reaction pressure of 1.0 MPa, the two-phase fluid stayed in the microchannel reactor for 10 minutes, and after gas-liquid phase separation, an oxidation product suspension was obtained;

[0109] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and stripping the filtrate to remove the organic solvent to obtain the intermediate product tert-butyl-p-benzoquinone. The conversion rate of the raw material 2-tert-butylphenol is 97%, and the yield of the intermediate product is 68.1%;

[0110] 5) Dissolve tert-butyl-p-benzoquinone in methanol to prepare a hydrogenation reaction solution. In a fixed bed reactor, the reaction temperature is 150°C, the reaction pressure is 1.6 MPa, and the feed space velocity is 1.0 h -1 , hydrogenation reaction for 3h, the product was evaporated and crystallized to obtain tert-butylhydroquinone crystals with a purity of 99.1%, and the total yield of the product was 67.5%.

[0111] Example 7

[0112] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in a), the gas-liquid mixing unit is T-shaped, the inner diameter of the reaction gas channel is 2 mm, the inner diameter of the reaction liquid channel is 2.4 mm, and the inner diameter of the downstream microchannel reaction tube is 8 mm.

[0113] The microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.04m.

[0114] In this embodiment, Figure 2 As shown, a double emulsion generator 2 is also provided downstream of the gas-liquid mixing unit 1. The inlet of the double emulsion generator 2 and the outlet of the gas-liquid mixing unit 1 are both constricted orifices, with the inlet of the double emulsion generator 2 nested within the outlet of the gas-liquid mixing unit 1. The outlet of the double emulsion generator 2 communicates with the reaction tube; the double emulsion generator 2 body is provided with two inert oil phase inlets, through which silicone oil is introduced.

[0115] The horizontal angle α of the narrowed pipe opening at the outlet of the gas-liquid mixing unit 1 is 10°. The angle β of the narrowed pipe opening at the inlet of the double emulsion generating device 2 with the vertical direction is 30°.

[0116] In this embodiment, the material of the microchannel reactor is Hastelloy.

[0117] A method for synthesizing tert-butylhydroquinone using the above-mentioned microchannel reactor:

[0118] 1) using acetonitrile and acetone as organic solvents to prepare an oxidation reaction solution, wherein the raw material 2-tert-butylphenol has a concentration of 5.0 mol / L, CuO and CrCl3 are selected as main catalysts, and the molar ratio of CuO and CrCl3 to 2-tert-butylphenol is 0.3; LiCl is selected as co-catalyst, and the molar ratio of LiCl to 2-tert-butylphenol is 0.9; diethanolamine and hydroxylamine are used as reducing agents, and the molar ratio of reducing agent to main catalyst is 2;

[0119] 2) introducing the oxidation reaction liquid and pure oxygen into a microchannel reactor at a flow rate of 1 L / min for the oxidation reaction liquid and 50 L / min for the pure oxygen gas to form a block flow pattern, and introducing silicone oil through a double emulsion generator to form a double emulsion structure to further promote gas-liquid mass transfer;

[0120] 3) Under the conditions of a reaction temperature of 140° C. and a reaction pressure of 1.2 MPa, the two-phase fluid resides in the microchannel reactor for 10 minutes, and a liquid-phase oxidation product suspension is obtained after phase separation of gas, liquid, and silicone oil;

[0121] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and subjecting the filtrate to distillation or stripping to remove the organic solvent and obtain the intermediate product tert-butyl-p-benzoquinone. The conversion rate of the raw material 2-tert-butylphenol is 100%, and the yield of the intermediate product is 71.1%;

[0122] 5) Dissolve tert-butyl-p-benzoquinone in methanol to prepare a hydrogenation reaction solution. In a fixed bed reactor, the reaction temperature is 155°C, the reaction pressure is 1.8 MPa, and the feed space velocity is 1.0 h -1 , hydrogenation reaction for 3h, the product was evaporated and crystallized to obtain tert-butylhydroquinone crystals with a purity of 99.1%, and the total yield of the product was 71%.

[0123] Example 8

[0124] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in a), the gas-liquid mixing unit is T-shaped, the inner diameter of the reaction gas channel is 2 mm, the inner diameter of the reaction liquid channel is 2.4 mm, and the inner diameter of the downstream microchannel reaction tube is 10 mm.

[0125] The microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.1m.

[0126] In this embodiment, Figure 2As shown, a double emulsion generator 2 is also provided downstream of the gas-liquid mixing unit 1. The inlet of the double emulsion generator 2 and the outlet of the gas-liquid mixing unit 1 are both constricted orifices, with the inlet of the double emulsion generator 2 nested within the outlet of the gas-liquid mixing unit 1. The outlet of the double emulsion generator 2 communicates with the reaction tube; the double emulsion generator 2 body is provided with two inert oil phase inlets, through which the fluorinated liquid is introduced.

[0127] The horizontal angle α of the narrowed pipe opening at the outlet of the gas-liquid mixing unit 1 is 5°. The horizontal angle β of the narrowed pipe opening at the inlet of the double emulsion generating device 2 with the vertical direction is 50°.

[0128] In this embodiment, the material of the microchannel reactor is Hastelloy.

[0129] A method for synthesizing tert-butylhydroquinone using the above-mentioned microchannel reactor:

[0130] 1) using ethanol, n-butanol, and tetrahydrofuran as organic solvents, and ethanolamine and hydrazine hydrate as reducing agents to prepare an oxidation reaction solution, wherein the concentration of the raw material 2-tert-butylphenol is 5.0 mol / L, CuO-ZnO and CrCl3 are selected as the main catalyst, and the molar ratio of each to the 2-tert-butylphenol is 0.3; KCl and CaCl2 are selected as the co-catalyst, and the molar ratio of each to the 2-tert-butylphenol is 0.9, and the molar ratio of the reducing agent to the main catalyst is 2;

[0131] 2) introducing the oxidation reaction liquid and pure oxygen into a microchannel reactor at a flow rate of 1 L / min for the oxidation reaction liquid and 100 L / min for the pure oxygen gas to form a block flow pattern, and introducing the fluorinated liquid through a double emulsion generator to form a double emulsion structure to further promote gas-liquid mass transfer;

[0132] 3) Under the conditions of a reaction temperature of 150° C. and a reaction pressure of 3.0 MPa, the two-phase fluid resides in the microchannel reactor for 17 minutes, and a liquid-phase oxidation product suspension is obtained after phase separation of gas, liquid, and fluorinated liquid;

[0133] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and subjecting the filtrate to distillation or stripping to remove the organic solvent and obtain the intermediate product tert-butyl-p-benzoquinone. The conversion rate of the raw material 2-tert-butylphenol is 99%, and the yield of the intermediate product is 70.1%;

[0134] 5) Dissolve tert-butyl-p-benzoquinone in methanol to prepare a hydrogenation reaction solution in a fixed bed reactor at a reaction temperature of 150°C, a reaction pressure of 1.6 MPa, and a feed space velocity of 1.0 h -1 , hydrogenation reaction for 4 hours, the product was evaporated and crystallized to obtain tert-butylhydroquinone crystals with a purity of 99.1%, and the total yield of the product was 69.5%.

[0135] Example 9

[0136] A micro-packed bed reactor, such as Figure 4 As shown, it includes a micro-packed bed reactor inlet and a micro-packed bed reaction tube connected in sequence, the micro-packed bed reactor inlet includes a gas-liquid mixing unit, and the inner diameter of the downstream micro-packed bed reaction tube is 4 mm. Figure 1 As shown in (d), the gas-liquid mixing unit is a coaxial ring tube type, the inner diameter of the reaction gas channel is 0.5 mm, the inner diameter of the reaction liquid pipeline is 2 mm, and the contact angle between the inner wall of the coaxial ring tube and the liquid phase is greater than 60°. In other embodiments, the gas-liquid mixing unit can also be as follows Figure 1 The T-type shown in a) Figure 1 Y-type as shown in b) or as Figure 1 The hydraulic focusing type shown in c).

[0137] In this embodiment, the material of the micro-packed bed reactor is silicon carbide.

[0138] A method for synthesizing tert-butylhydroquinone using the above-mentioned micro-packed bed reactor:

[0139] 1) using ethanol, n-butanol, and tetrahydrofuran as organic solvents to prepare an oxidation reaction solution, wherein the concentration of the raw material 2-tert-butylphenol is 5.0 mol / L, and the catalyst in the micro-packed bed reaction tube is V-HMS mesoporous molecular sieve, and the molar ratio of the catalyst to 2-tert-butylphenol is 2;

[0140] 2) introducing the oxidation reaction liquid and pure oxygen into a micro-packed bed reactor at a flow rate of 1 L / min for the oxidation reaction liquid and 100 L / min for the pure oxygen gas to form a block flow pattern, and introducing the fluorinated liquid through a double emulsion generator to form a double emulsion structure to further promote gas-liquid mass transfer;

[0141] 3) Under the conditions of reaction temperature of 80℃ and reaction pressure of 3.0MPa, the two-phase fluid passes through the micro-packed bed reactor with a feed space velocity of 1.0h -1 , after phase separation of gas, liquid and fluorinated liquid, a liquid-phase oxidation product suspension is obtained;

[0142] 4) filtering the suspension to recover the catalyst in the filter cake, and subjecting the filtrate to distillation or stripping to remove the organic solvent and obtain the intermediate product tert-butyl-p-benzoquinone. The conversion rate of the raw material 2-tert-butylphenol is 73%, and the yield of the intermediate product is 65.7%;

[0143] 5) Dissolve tert-butyl-p-benzoquinone in methanol to prepare a hydrogenation reaction solution in a fixed bed reactor at a reaction temperature of 150°C, a reaction pressure of 1.6 MPa, and a feed space velocity of 1.0 h -1The product was subjected to hydrogenation for 4 hours, and then evaporated and crystallized to obtain tert-butylhydroquinone crystals with a purity of 99.1%. The total yield of the product was 65.1%.

[0144] Comparative Example 1

[0145] The oxidation reaction was carried out in a conventional kettle reactor with a volume of 100 mL and made of stainless steel.

[0146] The steps of synthesizing tert-butylhydroquinone using the above-mentioned traditional kettle reactor are as follows:

[0147] 1) Using ethanol, n-butanol, and tetrahydrofuran as organic solvents, ethanolamine and hydrazine hydrate as reducing agents, 50 mL of a 0.1 mol / L 2-tert-butylphenol solution was prepared as a reaction solution, CuO-ZnO and CrCl3 were selected as the main catalyst, and the molar ratio of the 2-tert-butylphenol was 0.15; KCl and CaCl2 were selected as the co-catalyst, and the molar ratio of the 2-tert-butylphenol was 0.1; the mixture was uniformly mixed and placed in a reactor, and the molar ratio of the reducing agent to the main catalyst was 0.5;

[0148] 2) The reactor was sealed and oxygen was introduced, the pressure in the reactor was maintained at 1 MPa, the reaction temperature was 20°C, and the reaction was carried out under magnetic stirring for 8 hours;

[0149] 3) After the reaction is completed, stirring is stopped, and the oxidation product suspension is filtered to recover the main catalyst and co-catalyst in the filter cake. The filtrate is subjected to rectification to remove the organic solvent and obtain the intermediate product tert-butyl-p-benzoquinone. The conversion rate of the raw material 2-tert-butylphenol is 99%, and the yield of the intermediate product is 65.1%;

[0150] 4) tert-Butyl-p-benzoquinone was prepared into a hydrogenation reaction solution, placed in a reactor, and hydrogen was introduced at a reaction pressure of 3 MPa, a reaction temperature of 80° C., and a reaction time of 3 h. The hydrogenation reaction was carried out. The product was evaporated and crystallized to obtain tert-butylhydroquinone crystals with a purity of 99.1%. The total yield of the product was 64.5%. Compared with Example 1, the yield was reduced by 3.6%, and the oxidation reaction time was increased by 6 hours.

[0151] Comparative Example 2

[0152] The oxidation reaction was carried out in a conventional kettle reactor with a volume of 100 mL and made of stainless steel.

[0153] The steps of synthesizing tert-butylhydroquinone using the above-mentioned traditional kettle reactor are as follows:

[0154] 1) using acetonitrile and acetone as organic solvents to prepare an oxidation reaction solution, wherein the raw material 2-tert-butylphenol has a concentration of 0.5 mol / L, CuO and CrCl3 are selected as main catalysts, and the molar ratio of CuO and CrCl3 to 2-tert-butylphenol is 0.15; NaCl and LiCl are selected as co-catalysts, and the molar ratio of NaCl and LiCl to 2-tert-butylphenol is 0.3; the mixture is uniformly mixed and placed in a reaction kettle; diethanolamine and hydroxylamine are used as reducing agents, and the molar ratio of the reducing agent to the main catalyst is 1.0;

[0155] 2) The reactor was closed and sealed, oxygen was introduced, the pressure in the reactor was maintained at 1 MPa, the reaction temperature was 20°C, and the reaction was carried out under magnetic stirring for 10 h;

[0156] 3) After the reaction is completed, stirring is stopped, and the oxidation product suspension is filtered to recover the main catalyst and co-catalyst in the filter cake. The filtrate is subjected to rectification to remove the organic solvent and obtain the intermediate product tert-butyl-p-benzoquinone. The conversion rate of the raw material 2-tert-butylphenol is 97%, and the yield of the intermediate product is 62.5%;

[0157] 4) tert-Butyl-p-benzoquinone was dissolved in methanol to prepare a hydrogenation reaction solution, which was placed in a reactor and introduced with hydrogen gas at a pressure of 2.5 MPa, a temperature of 80° C., and a reaction time of 3 h. The hydrogenation reaction was carried out. The product was evaporated and crystallized to obtain tert-butylhydroquinone crystals with a purity of 99.3%. The total yield of the product was 62.1%. Compared with Example 3, the yield was reduced by 9.4%, and the oxidation reaction time was increased by 9.5 hours.

[0158] Comparative Example 3

[0159] The oxidation reaction was carried out in a conventional kettle reactor with a volume of 100 mL and made of stainless steel.

[0160] The steps of synthesizing tert-butylhydroquinone using the above-mentioned traditional kettle reactor are as follows:

[0161] 1) using acetonitrile and acetone as organic solvents to prepare an oxidation reaction solution, wherein the raw material 2-tert-butylphenol has a concentration of 1.5 mol / L, CuO and CrCl3 are selected as main catalysts, and the molar ratio of each to 2-tert-butylphenol is 0.3; NaCl and LiCl are selected as co-catalysts, and the molar ratio of each to 2-tert-butylphenol is 0.9; diethanolamine and hydroxylamine are used as reducing agents, and the molar ratio of the reducing agent to the main catalyst is 1.5; the mixture is uniformly mixed and placed in a reaction kettle;

[0162] 2) The reactor was closed and sealed, oxygen was introduced, the pressure in the reactor was maintained at 1.5 MPa, the reaction temperature was 20°C, and the reaction was carried out under magnetic stirring for 10 hours;

[0163] 3) After the reaction is completed, stirring is stopped, and the oxidation product suspension is filtered to recover the main catalyst and co-catalyst in the filter cake. The filtrate is stripped to remove the organic solvent and obtain the intermediate product tert-butyl-p-benzoquinone. The conversion rate of the raw material 2-tert-butylphenol is 87%, and the yield of the intermediate product is 53.1%;

[0164] 4) tert-Butyl-p-benzoquinone was dissolved in methanol to prepare a hydrogenation reaction solution, which was placed in a reactor and introduced with hydrogen gas at a pressure of 3.5 MPa, a temperature of 80° C., and a reaction time of 3 h. The hydrogenation reaction was carried out. The product was evaporated and crystallized to obtain tert-butylhydroquinone crystals with a purity of 99.1%. The total yield of the product was 52.6%. Compared with Example 6, the yield was reduced by 14.9%, and the oxidation reaction time was increased by 9 hours and 50 minutes.

[0165] Comparing the results of Comparative Examples 1-3 with Examples 1-8, as shown in Table 1, taking into account the construction of the block flow pattern and the gas-liquid reaction consumption, the preferred oxygen gas flow rate is 4-100 L / min, the reaction liquid flow rate is 0.2-5 L / min, and the oxygen to reaction liquid flow ratio is 20:1 to 100:1.

[0166] Comparative Example 4

[0167] The oxidation reaction was carried out in a conventional kettle reactor with a volume of 100 mL and made of stainless steel.

[0168] The steps of synthesizing tert-butylhydroquinone using the above-mentioned traditional kettle reactor are as follows:

[0169] 1) Using ethanol, n-butanol, and tetrahydrofuran as organic solvents, 50 mL of a 5 mol / L 2-tert-butylphenol solution was prepared as a reaction solution, and the catalyst was a V-HMS mesoporous molecular sieve, with a molar ratio of 2 to 2-tert-butylphenol; the mixture was uniformly mixed and placed in a reaction kettle;

[0170] 2) The reactor was sealed and oxygen was introduced, the pressure in the reactor was maintained at 1 MPa, the reaction temperature was 20°C, and the reaction was carried out under magnetic stirring for 8 hours;

[0171] 3) After the reaction is completed, stirring is stopped, and the oxidation product suspension is filtered to recover the catalyst in the filter cake. The filtrate is subjected to rectification to remove the organic solvent and obtain the intermediate product tert-butyl-p-benzoquinone. The conversion rate of the raw material 2-tert-butylphenol is 79%, and the yield of the intermediate product is 48.1%;

[0172] 4) tert-Butyl-p-benzoquinone was prepared into a hydrogenation reaction solution, placed in a reactor, and hydrogen was introduced at a reaction pressure of 3 MPa, a reaction temperature of 80° C., and a reaction time of 3 h. The hydrogenation reaction was carried out. The product was evaporated and crystallized to obtain tert-butylhydroquinone crystals with a purity of 99.1%. The total yield of the product was 47.7%. Compared with Example 9, the yield was reduced by 17.4%.

[0173] Table 1 shows the process conditions and effect evaluations of Examples 1-9 and Comparative Examples 1-4.

[0174] Table 1 Process conditions and effect evaluation table of Examples 1-9 and Comparative Examples 1-4

[0175]

[0176] Example 10

[0177] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in (d), the gas-liquid mixing unit is a coaxial ring tube type, the inner diameter of the reaction gas channel is 0.2 mm, the inner diameter of the reaction liquid and the downstream microchannel reaction tube are both 1 mm, and the contact angle between the inner wall of the coaxial ring tube and the liquid phase is greater than 60°. In other embodiments, the gas-liquid mixing unit can also be as follows Figure 1 The T-type shown in a) Figure 1 Y-type as shown in b) or as Figure 1 The hydraulic focusing type shown in c).

[0178] like Figure 3 As shown, the microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.02m.

[0179] In this embodiment, the material of the microchannel reactor is polytetrafluoroethylene.

[0180] A method for synthesizing hydroquinone using the above-mentioned microchannel reactor:

[0181] 1) using ethanol, n-butanol, and tetrahydrofuran as organic solvents, ethanolamine and hydrazine hydrate as reducing agents, and preparing an oxidation reaction solution, wherein the raw material phenol concentration is 0.1 mol / L, the main catalyst is CuO-ZnO and FeCl3, the co-catalyst is KCl and NaCl, the molar ratio of the main catalyst to phenol is 0.15, the molar ratio of the co-catalyst to phenol is 0.1, and the molar ratio of the reducing agent to the main catalyst is 0.5;

[0182] 2) The oxidation reaction liquid and pure oxygen were introduced into the microchannel reactor at a flow rate of 0.01 L / min for the oxidation reaction liquid and 0.1 L / min for the pure oxygen gas, forming a block flow pattern;

[0183] 3) Under the conditions of a reaction temperature of 60° C. and a reaction pressure of 2.5 MPa, the two-phase fluid stayed in the microchannel reactor for 120 minutes, and after gas-liquid phase separation, an oxidation product suspension was obtained;

[0184] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and subjecting the filtrate to distillation to remove the organic solvent and obtain the intermediate product p-benzoquinone. The conversion rate of the raw material phenol is 91%, and the yield of the intermediate product is 87.3%;

[0185] 5) Dissolve p-benzoquinone in methanol to prepare a hydrogenation reaction solution in a fixed bed reactor at a reaction temperature of 100°C, a reaction pressure of 2.0 MPa, and a feed space velocity of 1.0 h -1 The hydrogenation reaction was carried out for 2.5 hours. The product was evaporated and crystallized to obtain hydroquinone crystals with a purity of 99.1%. The total yield of the product was 86.5%.

[0186] Example 11

[0187] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in b), the gas-liquid mixing unit is Y-shaped, the inner diameter of the reaction gas channel is 1 mm, the inner diameter of the reaction liquid channel is 1.2 mm, and the inner diameter of the downstream microchannel reaction tube is 2 mm.

[0188] The microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.2m.

[0189] In this embodiment, Figure 2 As shown, a double emulsion generator 2 is also provided downstream of the gas-liquid mixing unit 1. The inlet of the double emulsion generator 2 and the outlet of the gas-liquid mixing unit 1 are both constricted orifices, with the inlet of the double emulsion generator 2 nested within the outlet of the gas-liquid mixing unit 1. The outlet of the double emulsion generator 2 communicates with the reaction tube. The double emulsion generator 2 is provided with two inert oil phase inlets. By introducing silicone oil, a countercurrent circulation shearing effect is generated, forming a double emulsion structure that further promotes gas-liquid mass transfer.

[0190] The horizontal angle α of the narrowed pipe opening at the outlet of the gas-liquid mixing unit 1 is 30°. The angle β of the narrowed pipe opening at the inlet of the double emulsion generating device 2 with the vertical direction is 45°.

[0191] In this embodiment, the material of the microchannel reactor is silicon carbide.

[0192] A method for synthesizing hydroquinone using the above-mentioned microchannel reactor:

[0193] 1) Acetonitrile and acetone are used as organic solvents to prepare an oxidation reaction solution, wherein the raw material phenol concentration is 0.1 mol / L, CuCl2.2H2O and FeCl3 are selected as main catalysts, and LiCl·H2O and NaNO3 are selected as co-catalysts; diethanolamine and hydroxylamine are used as reducing agents, the molar ratio of the main catalyst to phenol is 0.15, the molar ratio of the co-catalyst to phenol is 0.15, and the molar ratio of the reducing agent to the main catalyst is 0.5;

[0194] 2) The oxidation reaction liquid and pure oxygen were introduced into the microchannel reactor at a flow rate of 0.02 L / min for the oxidation reaction liquid and 0.2 L / min for the pure oxygen gas, forming a block flow pattern;

[0195] 3) Under the conditions of a reaction temperature of 60° C. and a reaction pressure of 2.5 MPa, the two-phase fluid resides in the microchannel reactor for 80 minutes, and the oxidation product suspension is obtained after phase separation of gas, liquid, and silicone oil;

[0196] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and subjecting the filtrate to rectification to remove the organic solvent and obtain the intermediate product p-benzoquinone. The conversion rate of the raw material phenol is 87%, and the yield of the intermediate product is 83.5%;

[0197] 5) Dissolve p-benzoquinone in methanol to prepare a hydrogenation reaction solution in a fixed bed reactor at a reaction temperature of 100°C, a reaction pressure of 2.0 MPa, and a feed space velocity of 1.0 h -1 The hydrogenation reaction was carried out for 2.5 hours. The product was evaporated and crystallized to obtain hydroquinone crystals with a purity of 99.2%. The total yield of the product was 82.8%.

[0198] Example 12

[0199] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in a), the gas-liquid mixing unit is T-shaped, the inner diameter of the reaction gas channel is 2 mm, the inner diameter of the reaction liquid channel is 2.4 mm, and the inner diameter of the downstream microchannel reaction tube is 4 mm.

[0200] The microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.2m.

[0201] In this embodiment, the material of the microchannel reactor is silicon carbide.

[0202] A method for synthesizing hydroquinone using the above-mentioned microchannel reactor:

[0203] 1) using acetonitrile and acetone as organic solvents to prepare an oxidation reaction solution, wherein the raw material phenol concentration is 0.5 mol / L, AgCl and CuI are selected as the main catalyst, and NaCl is selected as the co-catalyst; diethanolamine and hydroxylamine are used as reducing agents, the molar ratio of the main catalyst to phenol is 0.15, the molar ratio of the co-catalyst to phenol is 0.3, and the molar ratio of the reducing agent to the main catalyst is 1.0;

[0204] 2) The oxidation reaction liquid and pure oxygen were introduced into the microchannel reactor at a flow rate of 0.2 L / min for the oxidation reaction liquid and 4 L / min for the pure oxygen gas, forming a block flow pattern;

[0205] 3) Under the conditions of a reaction temperature of 60° C. and a reaction pressure of 2.5 MPa, the two-phase fluid stayed in the microchannel reactor for 30 minutes, and after gas-liquid phase separation, an oxidation product suspension was obtained;

[0206] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and subjecting the filtrate to distillation to remove the organic solvent and obtain the intermediate product p-benzoquinone. The conversion rate of the raw material phenol is 93%, and the yield of the intermediate product is 89.3%;

[0207] 5) Dissolve p-benzoquinone in methanol to prepare a hydrogenation reaction solution in a fixed bed reactor at a reaction temperature of 100°C, a reaction pressure of 2.0 MPa, and a feed space velocity of 1.0 h -1 The hydrogenation reaction was carried out for 2.5 hours. The product was evaporated and crystallized to obtain hydroquinone crystals with a purity of 99.1%. The total yield of the product was 88.5%.

[0208] Example 13

[0209] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in (c), the gas-liquid mixing unit is a hydraulic focusing structure, the inner diameter of the reaction gas channel is 2 mm, the inner diameter of the reaction liquid channel is 2.4 mm, and the inner diameter of the downstream microchannel reaction tube is 6 mm.

[0210] The microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.2m.

[0211] In this embodiment, the material of the microchannel reactor is silicon carbide.

[0212] A method for synthesizing hydroquinone using the above-mentioned microchannel reactor:

[0213] 1) using acetonitrile and acetone as organic solvents to prepare an oxidation reaction solution, wherein the raw material phenol concentration is 0.5 mol / L, CuO-ZnO and FeCl3 are selected as the main catalyst, and KCl and NaCl are selected as the co-catalyst; diethanolamine and hydroxylamine are used as reducing agents, the molar ratio of the main catalyst to phenol is 0.15, the molar ratio of the co-catalyst to phenol is 0.3, and the molar ratio of the reducing agent to the main catalyst is 1.0;

[0214] 2) The oxidation reaction liquid and pure oxygen were introduced into the microchannel reactor at a flow rate of 0.5 L / min for the oxidation reaction liquid and 20 L / min for the pure oxygen gas, forming a block flow pattern;

[0215] 3) Under the conditions of a reaction temperature of 60° C. and a reaction pressure of 2.5 MPa, the two-phase fluid stayed in the microchannel reactor for 60 minutes, and after gas-liquid phase separation, an oxidation product suspension was obtained;

[0216] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and subjecting the filtrate to rectification to remove the organic solvent and obtain the intermediate product p-benzoquinone. The conversion rate of the raw material phenol is 90%, and the yield of the intermediate product is 86.4%;

[0217] 5) Dissolve p-benzoquinone in methanol to prepare a hydrogenation reaction solution in a fixed bed reactor at a reaction temperature of 100°C, a reaction pressure of 2.0 MPa, and a feed space velocity of 1.0 h -1 The hydrogenation reaction was carried out for 2.5 hours. The product was evaporated and crystallized to obtain hydroquinone crystals with a purity of 99.2%. The total yield of the product was 85.7%.

[0218] Example 14

[0219] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in (c), the gas-liquid mixing unit is a hydraulic focusing structure, the inner diameter of the reaction gas channel is 2 mm, the inner diameter of the reaction liquid channel is 2.4 mm, and the inner diameter of the downstream microchannel reaction tube is 8 mm.

[0220] The microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.2m.

[0221] In this embodiment, the microchannel reactor is made of stainless steel.

[0222] A method for synthesizing hydroquinone using the above-mentioned microchannel reactor:

[0223] 1) using acetonitrile and acetone as organic solvents to prepare an oxidation reaction solution, wherein the raw material phenol concentration is 1.5 mol / L, Cu(NO3)2·3H2O and FeCl3 are selected as main catalysts, and NaCl and LiCl·H2O are selected as co-catalysts; diethanolamine and hydroxylamine are used as reducing agents, the molar ratio of the main catalyst to phenol is 0.3, the molar ratio of the co-catalyst to phenol is 0.9, and the molar ratio of the reducing agent to the main catalyst is 1.0;

[0224] 2) The oxidation reaction liquid and pure oxygen were introduced into the microchannel reactor at a flow rate of 0.2 L / min for the oxidation reaction liquid and 40 L / min for the pure oxygen gas, forming a block flow pattern;

[0225] 3) Under the conditions of a reaction temperature of 60°C and a reaction pressure of 2.5 MPa, the two-phase fluid stayed in the microchannel reactor for 73 minutes, and after gas-liquid phase separation, an oxidation product suspension was obtained;

[0226] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and subjecting the filtrate to rectification to remove the organic solvent and obtain the intermediate product p-benzoquinone. The conversion rate of the raw material phenol is 89%, and the yield of the intermediate product is 83.7%;

[0227] 5) Dissolve p-benzoquinone in methanol to prepare a hydrogenation reaction solution in a fixed bed reactor at a reaction temperature of 100°C, a reaction pressure of 2.0 MPa, and a feed space velocity of 1.0 h -1 The hydrogenation reaction was carried out for 2.5 hours. The product was evaporated and crystallized to obtain hydroquinone crystals with a purity of 99.2%. The total yield of the product was 83.0%.

[0228] Example 15

[0229] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in a), the gas-liquid mixing unit is T-shaped, the inner diameter of the reaction gas channel is 2 mm, the inner diameter of the reaction liquid channel is 2.4 mm, and the inner diameter of the downstream microchannel reaction tube is 4 mm.

[0230] The microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.2m.

[0231] In this embodiment, the microchannel reactor is made of stainless steel.

[0232] A method for synthesizing hydroquinone using the above-mentioned microchannel reactor:

[0233] 1) using acetonitrile and acetone as organic solvents to prepare an oxidation reaction solution, wherein the raw material phenol concentration is 1.5 mol / L, CuO-ZnO is selected as the main catalyst, and NaCl is selected as the co-catalyst; diethanolamine and hydroxylamine are used as reducing agents, the molar ratio of the main catalyst to phenol is 0.3, the molar ratio of the co-catalyst to phenol is 0.9, and the molar ratio of the reducing agent to the main catalyst is 1.5;

[0234] 2) The oxidation reaction liquid and pure oxygen were introduced into the microchannel reactor at a flow rate of 0.8 L / min for the oxidation reaction liquid and 32 L / min for the pure oxygen gas, forming a block flow pattern;

[0235] 3) Under the conditions of a reaction temperature of 70°C and a reaction pressure of 3.0 MPa, the two-phase fluid stayed in the microchannel reactor for 23 minutes, and after gas-liquid phase separation, an oxidation product suspension was obtained;

[0236] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and subjecting the filtrate to rectification to remove the organic solvent and obtain the intermediate product p-benzoquinone. The conversion rate of the raw material phenol is 97%, and the yield of the intermediate product is 93.1%;

[0237] 5) Dissolve p-benzoquinone in methanol to prepare a hydrogenation reaction solution in a fixed bed reactor at a reaction temperature of 100°C, a reaction pressure of 2.0 MPa, and a feed space velocity of 1.0 h -1 The hydrogenation reaction was carried out for 2.5 hours. The product was evaporated and crystallized to obtain hydroquinone crystals with a purity of 99.1%. The total yield of the product was 92.3%.

[0238] Example 16

[0239] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in a), the gas-liquid mixing unit is T-shaped, the inner diameter of the reaction gas channel is 2 mm, the inner diameter of the reaction liquid channel is 2.4 mm, and the inner diameter of the downstream microchannel reaction tube is 8 mm.

[0240] The microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.1m.

[0241] In this embodiment, Figure 2As shown, a double emulsion generator 2 is also provided downstream of the gas-liquid mixing unit 1. The inlet of the double emulsion generator 2 and the outlet of the gas-liquid mixing unit 1 are both constricted orifices, with the inlet of the double emulsion generator 2 nested within the outlet of the gas-liquid mixing unit 1. The outlet of the double emulsion generator 2 communicates with the reaction tube. The double emulsion generator 2 is provided with two inert oil phase inlets. By introducing silicone oil, a countercurrent circulation shearing effect is generated, forming a double emulsion structure that further promotes gas-liquid mass transfer.

[0242] The horizontal angle α of the narrowed pipe opening at the outlet of the gas-liquid mixing unit 1 is 5°. The angle β of the narrowed pipe opening at the inlet of the double emulsion generating device 2 with the vertical direction is 30°.

[0243] In this embodiment, the material of the microchannel reactor is Hastelloy.

[0244] A method for synthesizing hydroquinone using the above-mentioned microchannel reactor:

[0245] 1) using acetonitrile and acetone as organic solvents to prepare an oxidation reaction solution, wherein the raw material phenol concentration is 5.0 mol / L, CuO-ZnO is selected as the main catalyst, and NaCl is selected as the co-catalyst; diethanolamine and hydroxylamine are used as reducing agents, the molar ratio of the main catalyst to phenol is 0.3, the molar ratio of the co-catalyst to phenol is 0.9, and the molar ratio of the reducing agent to the main catalyst is 2.0;

[0246] 2) The oxidation reaction liquid and pure oxygen were introduced into the microchannel reactor at a flow rate of 1 L / min for the oxidation reaction liquid and 50 L / min for the pure oxygen gas, forming a block flow pattern;

[0247] 3) Under the conditions of a reaction temperature of 90° C. and a reaction pressure of 3.0 MPa, the two-phase fluid resides in the microchannel reactor for 20 minutes, and the oxidation product suspension is obtained after phase separation of gas, liquid, and silicone oil;

[0248] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and subjecting the filtrate to rectification to remove the organic solvent and obtain the intermediate product p-benzoquinone. The conversion rate of the raw material phenol is 91%, and the yield of the intermediate product is 87.4%;

[0249] 5) Dissolve p-benzoquinone in methanol to prepare a hydrogenation reaction solution in a fixed bed reactor at a reaction temperature of 100°C, a reaction pressure of 2.0 MPa, and a feed space velocity of 1.0 h -1 The hydrogenation reaction was carried out for 2.5 hours. The product was evaporated and crystallized to obtain hydroquinone crystals with a purity of 99.1%. The total yield of the product was 86.6%.

[0250] Example 17

[0251] A microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, such as Figure 1 As shown in a), the gas-liquid mixing unit is T-shaped, the inner diameter of the reaction gas channel is 2 mm, the inner diameter of the reaction liquid channel is 2.4 mm, and the inner diameter of the downstream microchannel reaction tube is 10 mm.

[0252] The microchannel reaction tube has multiple spiral turning structures including an enhanced mixing structure, and the spiral curvature of the reaction tube is 0.1m.

[0253] In this embodiment, Figure 2 As shown, a double emulsion generator 2 is also provided downstream of the gas-liquid mixing unit 1. The inlet of the double emulsion generator 2 and the outlet of the gas-liquid mixing unit 1 are both constricted orifices, with the inlet of the double emulsion generator 2 nested within the outlet of the gas-liquid mixing unit 1. The outlet of the double emulsion generator 2 communicates with the reaction tube. The double emulsion generator 2 is provided with two inert oil phase inlets. By introducing silicone oil, a countercurrent circulation shearing effect is generated, forming a double emulsion structure that further promotes gas-liquid mass transfer.

[0254] The horizontal angle α of the narrowed pipe opening at the outlet of the gas-liquid mixing unit 1 is 10°. The angle β of the narrowed pipe opening at the inlet of the double emulsion generating device 2 with the vertical direction is 50°.

[0255] In this embodiment, the material of the microchannel reactor is Hastelloy.

[0256] A method for synthesizing hydroquinone using the above-mentioned microchannel reactor:

[0257] 1) using ethanol, n-butanol, and tetrahydrofuran as organic solvents, and ethanolamine and hydrazine hydrate as reducing agents to prepare an oxidation reaction solution, wherein the raw material phenol concentration is 5.0 mol / L, Cu(NO3)2·3H2O and FeCl3 are selected as main catalysts, KCl and NaCl are selected as co-catalysts, the molar ratio of the main catalyst to phenol is 0.3, the molar ratio of the co-catalyst to phenol is 0.9, and the molar ratio of the reducing agent to the main catalyst is 2;

[0258] 2) The oxidation reaction liquid and pure oxygen were introduced into the microchannel reactor at a flow rate of 1 L / min for the oxidation reaction liquid and 100 L / min for the pure oxygen gas, forming a block flow pattern;

[0259] 3) Under the conditions of a reaction temperature of 90° C. and a reaction pressure of 3.0 MPa, the two-phase fluid resides in the microchannel reactor for 40 minutes, and the oxidation product suspension is obtained after phase separation of gas, liquid, and silicone oil;

[0260] 4) filtering the suspension to recover the main catalyst and co-catalyst in the filter cake, and subjecting the filtrate to distillation to remove the organic solvent and obtain the intermediate product p-benzoquinone. The conversion rate of the raw material phenol is 93%, and the yield of the intermediate product is 89.3%;

[0261] 5) Dissolve p-benzoquinone in methanol to prepare a hydrogenation reaction solution in a fixed bed reactor at a reaction temperature of 100°C, a reaction pressure of 2.0 MPa, and a feed space velocity of 1.0 h -1 The hydrogenation reaction was carried out for 2.5 hours. The product was evaporated and crystallized to obtain hydroquinone crystals with a purity of 99.1%. The total yield of the product was 88.5%.

[0262] Example 18

[0263] A micro-packed bed reactor, such as Figure 4 As shown, it includes a micro-packed bed reactor inlet and a micro-packed bed reaction tube connected in sequence, the micro-packed bed reactor inlet includes a gas-liquid mixing unit, and the inner diameter of the downstream micro-packed bed reaction tube is 4 mm. Figure 1 As shown in (d), the gas-liquid mixing unit is a coaxial ring tube type, the inner diameter of the reaction gas channel is 0.5 mm, the inner diameter of the reaction liquid pipeline is 2 mm, and the contact angle between the inner wall of the coaxial ring tube and the liquid phase is greater than 60°. In other embodiments, the gas-liquid mixing unit can also be as follows Figure 1 The T-type shown in a) Figure 1 Y-type as shown in b) or as Figure 1 The hydraulic focusing type shown in c).

[0264] In this embodiment, the material of the micro-packed bed reactor is silicon carbide.

[0265] A method for synthesizing hydroquinone using the above-mentioned micro-packed bed reactor:

[0266] 1) using ethanol, n-butanol, and tetrahydrofuran as organic solvents to prepare an oxidation reaction solution, wherein the raw material phenol concentration is 5.0 mol / L, and the catalyst in the micro-packed bed reaction tube is V-HMS mesoporous molecular sieve, and the molar ratio of the catalyst to phenol is 1;

[0267] 2) introducing the oxidation reaction liquid and pure oxygen into a micro-packed bed reactor at a flow rate of 1 L / min for the oxidation reaction liquid and 100 L / min for the pure oxygen gas to form a block flow pattern, and introducing the fluorinated liquid through a double emulsion generator to form a double emulsion structure to further promote gas-liquid mass transfer;

[0268] 3) Under the conditions of reaction temperature of 90°C and reaction pressure of 3.0 MPa, the two-phase fluid passes through the micro-packed bed reactor with a feed space velocity of 1.0 h -1 , after phase separation of gas, liquid and fluorinated liquid, a liquid-phase oxidation product suspension is obtained;

[0269] 4) filtering the suspension to recover the catalyst in the filter cake, and subjecting the filtrate to distillation or stripping to remove the organic solvent and obtain the intermediate product p-benzoquinone. The conversion rate of the raw material phenol is 79%, and the yield of the intermediate product is 73.5%;

[0270] 5) Dissolve p-benzoquinone in methanol to prepare a hydrogenation reaction solution in a fixed bed reactor at a reaction temperature of 100°C, a reaction pressure of 2 MPa, and a feed space velocity of 1.0 h -1 The hydrogenation reaction was carried out for 4 hours, and the product was evaporated and crystallized to obtain hydroquinone crystals with a purity of 99.1%. The total yield of the product was 73.2%.

[0271] Comparative Example 5

[0272] The oxidation reaction was carried out in a conventional kettle reactor with a volume of 100 mL and made of stainless steel.

[0273] The steps of synthesizing hydroquinone using the above-mentioned traditional kettle reactor are:

[0274] 1) Using ethanol, n-butanol, and tetrahydrofuran as organic solvents, ethanolamine and hydrazine hydrate as reducing agents, 50 mL of a 0.1 mol / L phenol solution was prepared as a reaction solution, CuO-ZnO and FeCl3 were selected as the main catalyst, KCl and NaCl were selected as the co-catalyst, the molar ratio of the main catalyst to phenol was 0.15, the molar ratio of the co-catalyst to phenol was 0.1, the mixture was uniformly mixed and placed in a reactor, and the molar ratio of the reducing agent to the main catalyst was 0.5;

[0275] 2) The reactor was closed and sealed, oxygen was introduced, the pressure in the reactor was maintained at 2.5 MPa, the reaction temperature was 60°C, and the reaction was carried out under magnetic stirring for 5 hours;

[0276] 3) After the reaction is completed, stirring is stopped, and the oxidation product suspension is filtered to recover the main catalyst and co-catalyst in the filter cake. The filtrate is subjected to rectification to remove the organic solvent and obtain the intermediate product p-benzoquinone. The conversion rate of the raw material phenol is 97%, and the yield of the intermediate product is 81.5%;

[0277] 4) p-Benzoquinone was prepared into a hydrogenation reaction solution, placed in a reactor, and hydrogen was introduced at a pressure of 2 MPa, a temperature of 100° C., and a reaction time of 3 h. A hydrogenation reaction was carried out. The product was evaporated and crystallized to obtain hydroquinone crystals with a purity of 99.1%. The total yield of the product was 80.8%. Compared with Example 10, the yield was reduced by 5.7%, and the oxidation reaction time was increased by 3 hours.

[0278] Comparative Example 6

[0279] The oxidation reaction was carried out in a conventional kettle reactor with a volume of 100 mL and made of stainless steel.

[0280] The steps of synthesizing hydroquinone using the above-mentioned traditional kettle reactor are as follows:

[0281] 1) using acetonitrile and acetone as organic solvents, preparing 50 mL of a 0.5 mol / L phenol solution as a reaction solution, selecting AgCl and CuI as the main catalyst, selecting NaCl as the co-catalyst, and diethanolamine and hydroxylamine as the reducing agent, the molar ratio of the main catalyst to phenol being 0.15, the molar ratio of the co-catalyst to phenol being 0.3, and the molar ratio of the reducing agent to the main catalyst being 1.0; the mixture is uniformly mixed and placed in a reaction kettle;

[0282] 2) The reactor was sealed and oxygen was introduced, the pressure in the reactor was maintained at 2.5 MPa, the reaction temperature was 60°C, and the reaction was carried out under magnetic stirring for 7 hours;

[0283] 3) After the reaction is completed, stirring is stopped, and the oxidation product suspension is filtered to recover the main catalyst and co-catalyst in the filter cake. The filtrate is subjected to rectification to remove the organic solvent and obtain the intermediate product p-benzoquinone. The conversion rate of the raw material phenol is 97%, and the yield of the intermediate product is 86.3%;

[0284] 4) p-Benzoquinone was prepared into a hydrogenation reaction solution, placed in a reactor, and hydrogen was introduced at a pressure of 2 MPa, a temperature of 100° C., and a reaction time of 3 h. A hydrogenation reaction was carried out. The product was evaporated and crystallized to obtain hydroquinone crystals with a purity of 99.3%. The total yield of the product was 85.7%. Compared with Example 12, the yield was reduced by 2.8%, and the oxidation reaction time was increased by 6.5 hours.

[0285] Comparative Example 7

[0286] The oxidation reaction was carried out in a conventional kettle reactor with a volume of 100 mL and made of stainless steel.

[0287] The steps of synthesizing hydroquinone using the above-mentioned traditional kettle reactor are:

[0288] 1) using acetonitrile and acetone as organic solvents, preparing 50 mL of a 1.5 mol / L phenol solution as a reaction solution, selecting CuO-ZnO as the main catalyst, selecting NaCl as the co-catalyst, and using diethanolamine and hydroxylamine as reducing agents, with a molar ratio of the main catalyst to phenol of 0.3, a molar ratio of the co-catalyst to phenol of 0.9, and a molar ratio of the reducing agent to the main catalyst of 1.5; the mixture is uniformly mixed and placed in a reaction kettle;

[0289] 2) The reactor was sealed and oxygen was introduced, the pressure in the reactor was maintained at 3.0 MPa, the reaction temperature was 70°C, and the reaction was carried out under magnetic stirring for 7 hours;

[0290] 3) After the reaction is completed, stirring is stopped, and the oxidation product suspension is filtered to recover the main catalyst and co-catalyst in the filter cake. The filtrate is subjected to rectification to remove the organic solvent and obtain the intermediate product p-benzoquinone. The conversion rate of the raw material phenol is 89%, and the yield of the intermediate product is 73.9%;

[0291] 4) p-Benzoquinone was prepared into a hydrogenation reaction solution, placed in a reactor, and hydrogen was introduced at a pressure of 2 MPa, a temperature of 100° C., and a reaction time of 3 h. A hydrogenation reaction was carried out. The product was evaporated and crystallized to obtain hydroquinone crystals with a purity of 99.1%. The total yield of the product was 73.2%. Compared with Example 15, the yield was reduced by 19.1%, and the oxidation reaction time was increased by 6 hours and 37 minutes.

[0292] Comparing the results of Comparative Examples 4-6 with Examples 9-16, as shown in Table 2, taking into account the construction of the block flow pattern and the gas-liquid reaction consumption, the preferred oxygen gas flow rate is 4-100 L / min, the reaction liquid flow rate is 0.2-1 L / min, and the oxygen to reaction liquid flow ratio is 15:1 to 100:1.

[0293] Comparative Example 8

[0294] The oxidation reaction was carried out in a conventional kettle reactor with a volume of 100 mL and made of stainless steel.

[0295] The steps of synthesizing hydroquinone using the above-mentioned traditional kettle reactor are:

[0296] 1) Using ethanol, n-butanol, and tetrahydrofuran as organic solvents, 50 mL of a 5 mol / L phenol solution was prepared as a reaction solution, and the catalyst was a V-HMS mesoporous molecular sieve, with a molar ratio of 1 to phenol; the mixture was uniformly mixed and placed in a reaction kettle;

[0297] 2) The reactor was sealed and oxygen was introduced, the pressure in the reactor was maintained at 3 MPa, the reaction temperature was 50°C, and the reaction was carried out under magnetic stirring for 8 hours;

[0298] 3) After the reaction is completed, stirring is stopped, and the oxidation product suspension is filtered to recover the catalyst in the filter cake. The filtrate is subjected to rectification to remove the organic solvent and obtain the intermediate product p-benzoquinone. The conversion rate of the raw material phenol is 75%, and the yield of the intermediate product is 47.2%;

[0299] 4) p-Benzoquinone was prepared into a hydrogenation reaction solution, placed in a reactor, and hydrogen was introduced at a pressure of 3 MPa, a temperature of 80° C., and a reaction time of 3 h. The hydrogenation reaction was carried out. The product was evaporated and crystallized to obtain tert-butylhydroquinone crystals with a purity of 99.1%. The total yield of the product was 46.8%. Compared with Example 18, the yield was reduced by 26.4%.

[0300] Table 2 shows the process conditions and effect evaluation results of Examples 10-18 and Comparative Examples 5-8.

[0301] Table 2 Process conditions and effect evaluation table for Examples 10-18 and Comparative Examples 5-8

[0302]

[0303] As can be seen from Examples 1-18 and Comparative Examples 1-8 in Tables 1 and 2, the microreactor and the method for synthesizing hydroquinone compounds provided by the present invention are used to prepare hydroquinone and tert-butylhydroquinone. The synthesis path is stable, the product yield is high, the purity is high, the reaction time is shorter, and the safety is higher, and the method has prospects for industrial promotion and application.

[0304] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

[0305] Furthermore, those skilled in the art will appreciate that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and to form distinct embodiments. For example, in the claims above, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is intended solely to enhance understanding of the overall background of this application and should not be construed as an admission or any implication that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for synthesizing hydroquinone compounds using a microreactor, wherein the microreactor comprises a microchannel reactor, wherein the microchannel reactor comprises a microchannel reactor inlet and a microchannel reaction tube connected in sequence, wherein the microchannel reactor inlet comprises a gas-liquid mixing unit, and the gas-liquid mixing unit is T-shaped, Y-shaped, hydraulic focusing type, or coaxial ring tube type, characterized in that: A phenol compound, a main catalyst, and a co-catalyst are dissolved in an organic solvent to form a reaction solution, a reducing agent is added, and the pH value is adjusted so that the metal in the reaction solution is approximately in a sol state. The reaction solution and an oxidizing reaction gas are introduced into a microchannel reactor to form a block flow pattern and perform an oxidation reaction. After gas-liquid separation, the liquid product is distilled or stripped to obtain an intermediate product, a p-benzoquinone compound. The p-benzoquinone compound is subjected to a hydrogenation reaction, evaporation, and crystallization to obtain the hydroquinone compound. The hydroquinone compound includes hydroquinone and / or tert-butylhydroquinone; The phenolic compound includes phenol and / or 2-tert-butylphenol; The organic solvent is one or a mixture of acetonitrile, acetone, methanol, ethanol, propanol, n-butanol or tetrahydrofuran; The main catalyst is one or a mixture of Cu(NO3)2·3H2O, CuCl2·2H2O, AgCl, CuO-ZnO, CuI, CuO, FeCl3 or CrCl3; The co-catalyst is one or a mixture of LiCl, LiCl·H2O, NaCl, KCl, NaNO3, KNO3 or CaCl2.

2. The method according to claim 1, characterized in that The microchannel reaction tube has one or more spiral and / or turning structures.

3. The method according to claim 2, characterized in that The spiral and / or turning structure includes an inverted structure or an enhanced hybrid structure.

4. The method according to claim 1, wherein The main catalyst CuO-ZnO is prepared by a co-precipitation method, with Na2CO3 as a precipitant, a copper-zinc mass ratio of 2:1, and the copper source and zinc source are Cu(NO3)2·3H2O and Zn(NO3)2·6H2O respectively.

5. The method according to claim 1, wherein The molar ratio of the main catalyst to the phenol compound is 0.1 to 0.5:1; the molar ratio of the co-catalyst to the phenol compound is 0.1 to 1.0:

1.

6. The method according to claim 1, characterized in that The reducing agent is one or a mixture of ethanolamine, diethanolamine, hydrazine hydrate or hydroxylamine.

7. The method according to claim 1, characterized in that The pH value is adjusted to 3-6.

8. A method for synthesizing hydroquinone compounds using a microreactor, wherein the microreactor comprises a micro-packed bed reactor, wherein the micro-packed bed reactor comprises a micro-packed bed reactor inlet and a micro-packed bed reaction tube connected in sequence; wherein the micro-packed bed reactor inlet comprises a gas-liquid mixing unit, wherein the gas-liquid mixing unit is T-shaped, Y-shaped, hydraulic focusing type, or coaxial ring tube type, characterized in that: A phenol compound is dissolved in an organic solvent to form a reaction liquid, the reaction liquid and an oxidation reaction gas are passed into a micro-packed bed reactor loaded with a molecular sieve catalyst to form a block flow pattern and perform an oxidation reaction, after gas-liquid separation, the liquid product is distilled or stripped to obtain an intermediate p-benzoquinone compound, and the p-benzoquinone compound is subjected to a hydrogenation reaction, evaporation, and crystallization to obtain the hydroquinone compound; The hydroquinone compound includes hydroquinone and / or tert-butylhydroquinone; The phenolic compound includes phenol and / or 2-tert-butylphenol; The organic solvent is one or a mixture of acetonitrile, acetone, methanol, ethanol, propanol, n-butanol or tetrahydrofuran; The molecular sieve catalyst is a vanadium-loaded mesoporous molecular sieve.

9. The method according to claim 1 or 8, characterized in that The inlet size of the gas-liquid mixing unit is 0.1-3 mm; the inner diameter of the microchannel reaction tube is 0.1-10 mm, and the spiral curvature is 0.01-0.2 m.

10. The method according to claim 1 or 8, characterized in that A double emulsion generating device is provided downstream of the gas-liquid mixing unit to further promote gas-liquid mass transfer.

11. The method according to claim 10, characterized in that The inlet of the double emulsion generating device is sleeved on the outlet of the gas-liquid mixing unit, and the outlet of the double emulsion generating device is connected to the micro-packed bed reaction tube or microchannel reaction tube; the double emulsion generating device body is also provided with several inert oil phase inlets.

12. The method according to claim 11, characterized in that The socket structure meets one of the following conditions: a. The outlet of the gas-liquid mixing unit is a constricted pipe orifice, the horizontal angle α of which is 5° to 45°; b. The inlet of the double emulsion generating device is a constricted orifice, the angle β with the vertical direction is 30° to 60°; c. The inlet of the double emulsion generating device is connected to the outlet of the gas-liquid mixing unit.

13. The method according to claim 1 or 8, characterized in that The concentration of the phenol compound raw material is 0.1 to 5 mol / L; the flow rate of the reaction solution is 0.01 to 10 L / min; The oxidation reaction gas is oxygen, air or a combination of the two; The flow ratio of the oxidation reaction gas to the reaction liquid is 10:1 to 100:

1.

14. The method according to claim 13, characterized in that The flow ratio of the oxidation reaction gas to the reaction liquid is 15:1 to 100:

1.

15. The method according to claim 1 or 8, characterized in that The oxidation reaction temperature is 0 to 150°C; The oxidation reaction pressure is 0.5-4.0 MPa; The oxidation reaction time is 1 to 120 minutes.

16. The method according to claim 1 or 8, characterized in that The hydrogenation reaction temperature is 50-200°C; The hydrogenation reaction pressure is 1.0-5.0 MPa; The hydrogenation reaction time is 2 to 4 hours.

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