Catalyst, preparation method thereof and preparation method of 9-fluorenone

Abstract

The invention provides a catalyst, a preparation method thereof and a preparation method of 9-fluorenone. The catalyst takes foam metal as a carrier, and transition metal oxide with a spinel structure is loaded on the surface and / or in pores of the foam metal; wherein the transition metal oxide exists on the surface and / or in pores of the foam metal in the form of nanosheets with the thickness of 5-20 nm, and the pore density of the foam metal is 40-120 PPI. The catalyst provided by the invention can be used for preparing 9-fluorenone. The preparation method of the catalyst is simple and easy to implement, raw materials are easy to obtain, and the catalyst is suitable for mass production.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic synthesis and relates to a catalyst and a preparation method thereof and a preparation method of 9-fluorenone. Background Art

[0002] 9-Fluorenone (hereinafter referred to as fluorenone) is an important organic synthesis intermediate and is widely used in various industrial fields, especially in the synthesis of medicines, pesticides, dyes and polymer materials. In the field of medicine, fluorenone and its derivatives are used as intermediates for the synthesis of anticonvulsant drugs such as 2-hydroxyaminoacetylfluorenone; in materials science, fluorenone is often used as an intermediate for the synthesis of organic light-emitting diode materials, photoconductive materials and high-performance polymers. Therefore, the development of an efficient, economical and environmentally friendly fluorenone preparation technology has important industrial significance.

[0003] Traditional methods for the oxidation of fluorene mainly rely on the use of heavy metal oxidants (such as chromates, manganates) or chemical reagents (such as hydrogen peroxide), which are usually accompanied by high environmental pollution and expensive production costs. In addition, the selectivity of the catalysts in these methods is poor, the reaction conditions are relatively harsh, and high temperatures or strong acid-base conditions are usually required. More by-products are also produced during the reaction, which increases the difficulty of product separation and purification and affects the overall yield. Therefore, the selection of catalysts and reactors has become the key to the efficient catalytic oxidation of fluorene.

[0004] In recent years, using molecular oxygen as an oxidant has become a green and efficient strategy for the synthesis of fluorenone. The use of highly selective catalysts (such as transition metal catalysts or nanomaterials) and mild oxidants (such as oxygen or air) can not only reduce the use of traditional oxidants and reduce environmental pollution, but also achieve efficient oxidation of fluorene under low energy consumption conditions. In particular, in recent years, researchers have tried to use materials such as supported metal catalysts (such as reference 1), heteropolyacid catalysts, cerium oxide, etc., combined with green oxidants such as molecular oxygen or air, to carry out oxidation reactions of fluorene under milder conditions to improve the selectivity and yield of fluorenone. Although existing patent documents (such as reference 2 and reference 3) disclose catalysts for catalytic oxidation of fluorene, most catalysts are solid powders, and the poor gas-liquid-solid three-phase mass transfer during the reaction restricts its industrial amplification.

[0005] In addition, the catalytic oxidation reaction of fluorene is basically carried out in a stirred tank reactor, while the traditional stirred tank reactor has huge defects when carrying out oxygen oxidation reactions. For example, the poor heat and mass transfer performance of the stirred tank reactor means that the reaction often takes a long time (several hours or even 1 day), making it difficult to scale up industrially. In addition, the solubility of oxygen in most organic solvents is low, which means that the oxidation reaction often requires a higher pressure. The traditional stirred tank reactor has a large liquid holding capacity, and there are serious safety issues when operating under high pressure. In recent years, the emergence of microreactor technology has brought feasible process intensification methods to oxygen oxidation reactions. Due to its excellent transfer performance, the microreactor can effectively improve the reaction efficiency of gas-liquid reactions. In addition, the advantages of the microreactor, such as small liquid holding capacity and continuous operation, can improve the time and space yield of the reaction under the premise of intrinsic safety.

[0006] Therefore, studying a catalyst for synthesizing 9-fluorenone and a method for preparing 9-fluorenone and solving the above-mentioned technical problems have become the top priority of current research.

[0007] References:

[0008] Reference 1: Applied Surface Science, 2024, 654, 159522.

[0009] Reference 2: CN109772326B

[0010] Reference 3: CN112473676B Summary of the invention

[0011] Problem that the invention aims to solve

[0012] In view of the technical problems existing in the prior art, the present invention first provides a catalyst. The catalyst of the present invention can be used for the preparation of 9-fluorenone, and more specifically, the catalyst of the present invention is a catalyst suitable for a micro-packed bed reactor.

[0013] Furthermore, the present invention also provides a method for preparing a catalyst, which is simple and easy to implement, and the raw materials are easy to obtain, and is suitable for mass production.

[0014] Furthermore, the present invention also provides a method for preparing 9-fluorenone, which has simple reaction conditions, environmentally friendly reaction steps, and a microreactor with a small liquid holding volume and high production efficiency. It can produce 9-fluorenone on a large scale, overcoming the problems of long reaction time, low yield and poor production safety in the existing preparation process of 9-fluorenone, and can also achieve continuous and stable operation.

[0015] Solutions for solving problems

[0016] The present invention aims to design a fluorene catalytic oxidation catalyst that can be used in microreactor technology through innovative catalytic system design, and develop a new microreactor process for its continuous flow catalytic oxidation. Through the optimization design of the catalyst and the regulation of process conditions, it is possible to achieve efficient oxidation of fluorene at a short residence time, significantly improve the yield of fluorenone, and produce fewer by-products, and is easy to operate, with great industrial application potential.

[0017] It has been found that the above technical problems can be solved by implementing the following technical solutions:

[0018] [1] A catalyst suitable for a micro-packed bed reactor, wherein the catalyst is supported by a foamed metal, and a transition metal oxide with a spinel structure is loaded on the surface and / or in the pores of the foamed metal;

[0019] in,

[0020] The transition metal oxide is present on the surface and / or in the pores of the foam metal in the form of nanosheets with a thickness of 5 to 20 nm.

[0021] The pore density of the foam metal is 40-120 PPI.

[0022] [2] The catalyst according to [1], wherein

[0023] In the catalyst, the loading amount of the transition metal oxide is 0.01 to 0.1 g / cm based on the volume of the foamed metal. 3 , preferably 0.03 to 0.05 g / cm 3 ;

[0024] The content of oxygen in the transition metal oxide is 40 mol% to 70 mol%.

[0025] [3] The catalyst according to [1] or [2], wherein

[0026] The foam metal includes any one of foam nickel, foam copper and foam iron, preferably foam nickel;

[0027] The transition metal includes a combination of two or more of cobalt, manganese and nickel.

[0028] [4] A method for preparing a catalyst according to any one of [1] to [3], wherein the preparation method comprises the following steps:

[0029] 1) Pretreatment of the foam metal: performing surface treatment on the foam metal to remove oxides and impurities on the surface of the foam metal;

[0030] 2) Loading of transition metal oxide catalyst layer: An aqueous solution containing transition metal salt is used as a precursor solution, and electrodeposition is performed at room temperature, followed by calcination to obtain the catalyst layer.

[0031] [5]. The preparation method according to [4], wherein in step 2),

[0032] The concentration of the transition metal salt in the precursor solution is 1-6 mol / L.

[0033] [6]. The preparation method according to [4] or [5], wherein in step 2),

[0034] The voltage of the electrodeposition is 1 to 6 V, and the time of the electrodeposition is 10 to 60 s;

[0035] The calcination temperature is 200-600° C., and the calcination time is 1-4 hours.

[0036] [7]. Use of the catalyst according to any one of [1] to [3] in the preparation of 9-fluorenone by oxidation of fluorene, wherein a microfilled reactor is used in the preparation.

[0037] [8]. A method for preparing 9-fluorenone, comprising the following steps:

[0038] The oxygen-containing gas and the reaction solvent containing fluorene are introduced into a micro mixer for mixing, and then enter into a micro packed bed reactor for catalytic oxidation reaction, and then cooled in a micro coil, and then separated into gas and liquid in a gas-liquid phase separator to obtain 9-fluorenone;

[0039] Wherein, the filler in the micro-packed bed reactor is a catalyst according to any one of [1] to [3];

[0040] Furthermore, the micro-packed bed reactor and the micro-coil are each independently placed in a temperature-controlled box.

[0041] [9]. The preparation method according to [8], wherein:

[0042] The molar ratio of oxygen in the oxygen-containing gas to fluorene is (10-60):1;

[0043] The oxygen concentration in the oxygen-containing gas is 21 to 100%.

[0044]

[10] . The preparation method according to [8] or [9], wherein:

[0045] The temperature of the catalytic oxidation reaction is 80 to 140°C;

[0046] The catalytic oxidation reaction time is 10min to 60min;

[0047] The pressure of the catalytic oxidation reaction is 0.5-5 MPa.

[0048]

[11] . The preparation method according to any one of [8] to

[10] , wherein

[0049] The reaction solvent includes any one of toluene, p-xylene, o-dichlorobenzene, cyclohexane, propylene carbonate, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

[0050] Effects of the Invention

[0051] Through the implementation of the above technical solution, the beneficial effects of the present invention are:

[0052] 1) The catalyst of the present invention has good catalytic effect and can be used for the preparation of 9-fluorenone.

[0053] 2) The preparation method of the catalyst of the present invention is simple and easy, the raw materials are easy to obtain, and it is suitable for mass production.

[0054] 3) The preparation method of 9-fluorenone of the present invention has simple reaction conditions, environmentally friendly reaction steps, short reaction time (within 1 hour), high product selectivity, and can effectively solve the problems of long reaction time, low yield and poor production safety in the prior art, thereby providing an economical and sustainable solution for the large-scale production of 9-fluorenone. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a macroscopic morphology of the catalyst prepared in Example 1 of the present invention;

[0056] Figure 2 The SEM spectrum of the catalyst prepared in Example 1 of the present invention (the left side is a low magnification, and the right side is a high magnification);

[0057] Figure 3 is the EDS spectrum of the catalyst prepared in Example 1 of the present invention;

[0058] Figure 4 The present invention is a process flow chart for preparing 9-fluorenone.

[0059] Description of reference numerals: Figure 4 In the figure, 1 is a pump; 2 is a back pressure valve 1; 3 is a gas mass flow controller; 4 is a micro mixer; 5 is a temperature control box 1; 6 is a micro packed bed reactor; 7 is a temperature control box 2; 8 is a micro coil; 9 is a back pressure valve 2; and 10 is a gas-liquid phase separator. DETAILED DESCRIPTION

[0060] Various exemplary embodiments, features and aspects of the present invention will be described in detail below. The word "exemplary" used here means "used as an example, embodiment or illustrative". Any embodiment described here as "exemplary" is not necessarily interpreted as being superior or better than other embodiments.

[0061] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In other examples, methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0062] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0063] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0064] In this specification, unless otherwise specified, the word "multiple" in "multiple", "multiple", "plurality", etc. means a numerical value of 2 or more.

[0065] In the present specification, "optional" or "optionally" means that the event or situation described below may or may not occur, and the description includes cases where the event occurs and cases where it does not occur.

[0066] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0067] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B.

[0068] In the present specification, a numerical range expressed using "above" or "below" means a numerical range including the number.

[0069] In this specification, when "normal temperature" or "room temperature" is used, the temperature may be 23±2°C.

[0070] <First aspect>

[0071] A first aspect of the present invention provides a catalyst, wherein the catalyst uses a foamed metal as a carrier, and a transition metal oxide with a spinel structure is loaded on the surface and / or in the pores of the foamed metal.

[0072] In some specific embodiments, the foam metal includes any one of foam nickel, foam copper and foam iron, preferably foam nickel. In some specific embodiments, the pore density of the foam metal is 40 to 120 PPI (average number of pores per linear inch), for example, 40 PPI, 50 PPI, 60 PPI, 70 PPI, 80 PPI, 90 PPI, 100 PPI, 110 PPI, 120 PPI, etc. It has been found that when the pore density is met, an efficient catalytic effect can be obtained, and the sufficient flow of materials can be guaranteed in the micro-packed bed reactor, so that the entire catalytic reaction can be carried out stably and continuously.

[0073] The present invention has no particular limitation on the shape of the foam metal, for example, a cylindrical shape is exemplified. Furthermore, the diameter of the cylinder is 2 to 5 mm, preferably 3 or 4 mm, and the height of the cylinder is 2 to 20 mm, preferably 5 mm.

[0074] In some specific embodiments, the transition metal oxide of the spinel structure can be represented by the formula AB2O4, wherein A is a divalent transition metal cation, B is a trivalent transition metal cation, A and B can be the same or different, and when A and B are the same, A (or B) represents two or more transition metals. During the research process of the present invention, it was found that for the catalytic oxidation system of fluorene, cobalt (or cobalt oxide), manganese (or manganese oxide) or a combination of the two have catalytic activity; while nickel (or nickel oxide) has no catalytic activity, but when it is combined with other transition metals (such as NiCo2O4), it has catalytic activity. In some specific embodiments, the transition metal includes a combination of two or more of cobalt, manganese and nickel.

[0075] In the catalyst of the present invention, the transition metal oxide is in the form of nanosheets and exists on the surface and / or in the pores of the foamed metal. In some specific embodiments, the thickness of the nanosheets is 5 to 20 nm, for example, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, etc.

[0076] In the catalyst of the present invention, the loading amount of the transition metal oxide is 0.01 to 0.1 g / cm2 based on the volume of the foamed metal. 3 , preferably 0.03 to 0.05 g / cm 3 , for example, it can be 0.02 g / cm 3 , 0.025g / cm3 , 0.03g / cm 3 , 0.035g / cm 3 , 0.04g / cm 3 , 0.045g / cm 3 , 0.05g / cm 3 , 0.055g / cm 3 , 0.06g / cm 3 , 0.07g / cm 3 , 0.08g / cm 3 , 0.09g / cm 3 , 0.1g / cm 3 wait.

[0077] In some specific embodiments, the content of oxygen in the transition metal oxide is 40 mol% to 70 mol%, for example, it can be 40 mol%, 47.1 mol%, 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, etc.

[0078] <Second Aspect>

[0079] The second aspect of the present invention provides a method for preparing the catalyst according to the first aspect of the present invention, comprising the following steps:

[0080] 1) Pretreatment of the foam metal: performing surface treatment on the foam metal to remove oxides and impurities on the surface of the foam metal;

[0081] 2) Loading of transition metal oxide catalyst layer: An aqueous solution containing transition metal salt is used as a precursor solution, and electrodeposition is performed at room temperature, followed by calcination to obtain the catalyst layer.

[0082] Step 1): Pretreatment of metal foam

[0083] The purpose of pretreatment of metal foam is mainly to remove oil stains and passivation oxide film on the surface of metal foam, making the surface of metal foam rougher and more porous, which is conducive to the enhancement of the loading and binding force of the transition metal oxide catalyst layer.

[0084] Specifically, the pretreatment step of the foam metal includes:

[0085] S1: Cutting and grinding: Cut the foam metal into a cylindrical shape (4 mm in diameter and 5 mm in height), and grind to remove the dense oxide film and other impurities on the surface.

[0086] S2: Degreasing: Place a certain amount of cut foam metal in acetone and use ultrasonic cleaning to remove surface oil stains.

[0087] S3: Pickling: Soak the degreased metal foam in an inorganic acid solution and perform ultrasonic cleaning to obtain a metal foam with a certain surface roughness. In a preferred embodiment of the present invention, the metal foam may be surface treated with dilute sulfuric acid, and the concentration of the dilute sulfuric acid may be 0.5 to 2 mol / L. Dilute sulfuric acid may also be used in combination with other types of solutions, such as ultrapure water, acetone, and mixed solutions thereof.

[0088] S4: taking out the pickled foam metal and rinsing it with deionized water. In a specific embodiment of the present invention, after the foam metal is surface treated, the treated foam metal can be dried for later use.

[0089] Step 2): Loading of transition metal oxide catalyst layer

[0090] The aqueous solution containing transition metal salt is used as a precursor solution, and electrodeposition is performed at room temperature, followed by calcination to obtain the product.

[0091] In some specific embodiments, the concentration of the transition metal salt in the precursor solution is 1 to 6 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.2 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, etc.

[0092] The type of transition metal salt of the present invention is not particularly limited in principle as long as it is (easily) soluble in water. For example, in some specific embodiments, the transition metal salt includes one or more of transition metal nitrates, transition metal sulfates, transition metal hydrochlorides or hydrates thereof.

[0093] Electrodeposition technology refers to the technology that forms a coating by causing anions and cations in the electrolyte to undergo redox reactions on the electrode surface under the action of an external electric field. Anions move toward the anode and cations move toward the cathode, where a reduction reaction occurs on the cathode surface to deposit a metal coating. The cathode overpotential acts as the driving force for the cathode reduction reaction, driving the electrodeposition of metal cations at the cathode.

[0094] In some specific embodiments, the anode material used in the electrodeposition is graphite, and the cathode material is foamed metal; wherein the graphite electrode is connected to the positive pole of the power supply, and the foamed metal is connected to the negative pole of the power supply.

[0095] In some specific embodiments, a DC constant voltage power supply is used in the electrodeposition.

[0096] In some specific embodiments, the voltage of the electrodeposition is 1 to 6V, for example, 1V, 1.5V, 2V, 2.5V, 3V, 3.5V, 4V, 4.5V, 5V, 5.5V, 6V, etc. Wherein, too high a voltage will lead to serious hydrogen evolution on the surface of the foam metal, generate a large number of bubbles, and the transition metal cannot be effectively deposited. Too high a voltage will also lead to a high oxidation potential of the graphite pole, resulting in an anode side reaction, thereby oxidizing the metal ions in the electrolyte into metal oxides; while too low a voltage will lead to a slow deposition rate and low deposition efficiency. In the present invention, when the voltage of the electrodeposition is controlled at 1 to 6V, the transition metal can be effectively and evenly deposited on the surface of the foam metal.

[0097] In some specific embodiments, the electrodeposition time is 10 to 60 s, for example, 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, 55 s, 60 s, etc.

[0098] In some specific embodiments, the calcination temperature is 200-600°C, for example, it can be 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C; the calcination heating rate is 2-10°C / min, preferably 5°C / min; the calcination time is 1-4h, for example, it can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, etc.

[0099] In some specific embodiments, before the calcination treatment, the electrodeposited metal foam is optionally washed with deionized water and then dried.

[0100] <Third Aspect>

[0101] The third aspect of the present invention provides a use of the catalyst according to the first aspect of the present invention in the preparation of 9-fluorenone by fluorene oxidation and a method for synthesizing 9-fluorenone using a microreactor based on the catalyst. In some preferred embodiments, the selectivity of the catalyst in the method can be 98% and the conversion rate can be 94%.

[0102] Specifically, the third aspect of the present invention also provides a method for preparing 9-fluorenone, which is a microreactor-based synthesis method comprising the following steps:

[0103] The oxygen-containing gas and the reaction solvent containing fluorene are introduced into a micro mixer for mixing, and then enter into a micro packed bed reactor for catalytic oxidation reaction, and then cooled in a micro coil, and then separated into gas and liquid in a gas-liquid phase separator to obtain 9-fluorenone;

[0104] Wherein, the filler in the micro-packed bed reactor is the catalyst described in the first aspect of the present invention;

[0105] Furthermore, the micro-packed bed reactor and the micro-coil are each independently placed in a temperature-controlled box.

[0106] A) The present invention utilizes a micro mixer to mix the raw materials for producing 9-fluorenone, i.e., oxygen-containing gas and a reaction solvent containing fluorene in the micro mixer. By utilizing the micro mixer to carry out the above-mentioned mixing, it is possible to fully mix the raw materials. Specifically, a pump (e.g., a horizontal flow pump, a diaphragm pump, a magnetic pump, a plunger pump, etc.) or a gas mass flow controller can be used to pass the raw materials into the micro mixer.

[0107] The present invention has no particular limitation on the oxygen-containing gas, and examples thereof include compressed air, pure oxygen, or air diluted with an inert gas such as nitrogen, argon or helium. Oxygen-containing air prepared by adding pure oxygen to air may also be used.

[0108] In some specific embodiments, the oxygen concentration in the oxygen-containing gas is 21-100%, for example, 21%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc. When the oxygen concentration in the oxygen-containing gas is within the above range, the reaction can be effectively carried out. Specifically, the oxygen concentration in the present invention refers to the volume concentration.

[0109] In some specific embodiments, the concentration of fluorene in the reaction solvent containing fluorene is 0.05-1 mol / L, for example, it can be 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, etc.

[0110] In some specific embodiments, the molar ratio of oxygen in the oxygen-containing gas to fluorene is (10-60):1, for example, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, etc. For example, the conversion rate of fluorene can be improved by adjusting the flow rate ratio of the oxygen-containing gas and the reaction solvent containing fluorene into the micromixer so that the molar ratio of oxygen in the oxygen-containing gas to fluorene is within the above range.

[0111] The present invention has no particular limitation on the reaction solvent, which can be an organic solvent commonly used in the art, for example, aromatic hydrocarbon solvents (e.g., toluene, p-xylene, o-dichlorobenzene), alkane solvents (e.g., cyclohexane), ester solvents (e.g., propylene carbonate), amide solvents (N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide), sulfoxide solvents (e.g., dimethyl sulfoxide), etc. In some specific embodiments, the reaction solvent includes any one of toluene, p-xylene, o-dichlorobenzene, cyclohexane, propylene carbonate, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide, preferably N-methylpyrrolidone.

[0112] The present invention has no particular limitation on the micromixer used, which can be any micromixer known in the art that is suitable for gas-liquid mixing, for example, a microchannel mixer (such as a micro tee), a membrane disperser mixer (such as a microporous membrane disperser), a micro packed bed disperser or a micro mesh mixer, etc.

[0113] b) In the present invention, the raw materials mixed in the micro mixer are introduced into a micro-packed bed reactor for catalytic oxidation reaction.

[0114] In the present invention, the packed bed reactor can be obtained by adjusting the packed bed reactor in the prior art, and the adjustment includes adjusting the microchannel equivalent diameter, microchannel volume and / or filler. In some specific embodiments, the catalyst described in the first aspect of the present invention is used as filler and filled in a micro-packed bed reactor. The configuration of the micro-packed bed reactor can be a cylindrical pipe, whose inner diameter is equivalent to the outer diameter of the catalyst carrier of the present invention, and the total length is equivalent to the total length of the filled catalyst.

[0115] In some specific embodiments, the temperature of the micro-mixer and the micro-packed bed reactor is controlled by a temperature control box 1, and the temperature of the catalytic oxidation reaction is 80-140°C, for example, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, etc.; by controlling the temperature in the micro-mixer and the micro-packed bed reactor at 80-140°C, the catalytic oxidation reaction rate and the conversion rate of fluorene can be increased. In some specific embodiments, the time of the catalytic oxidation reaction is 10min-60min, for example, 15min, 24min, 30min, 40min, 48min, 60min, etc.; by controlling the residence time in the micro-packed bed reactor at 10min-60min, the equipment size and investment can be reduced while ensuring the reaction rate and the conversion rate of fluorene.

[0116] The temperature control box 1 is not particularly limited in the present invention, and it can be a device known in the art for controlling the reaction temperature, for example, a constant temperature oil bath pot, a tubular air heating furnace, etc.

[0117] In some specific embodiments, the pressure of the catalytic oxidation reaction system can be controlled by a back pressure valve, and the pressure of the catalytic oxidation reaction is 0.5-5 MPa, for example, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, etc.; by controlling the pressure in the catalytic oxidation reaction system at 0.5-5 MPa, the catalytic oxidation reaction can be ensured to be carried out safely and effectively.

[0118] c) The present invention cools the gas-liquid mixture after oxidation reaction in the micro-packed bed reactor in a micro-coil.

[0119] In some specific embodiments, the temperature of the microcoil is controlled by a temperature control box 2, and the diameter and length of the microcoil are not limited as long as they can be kept cooled to room temperature.

[0120] The present invention has no particular limitation on the temperature control box 2 , which may be a temperature control device known in the art, such as a cooling cycle machine, an air cooler, and the like.

[0121] d) The present invention separates the gas-liquid mixture cooled in the microcoil into gas-liquid in a gas-liquid phase separator.

[0122] In some specific embodiments, the present invention separates the gas phase and the liquid phase of the gas-liquid mixture obtained after catalytic oxidation reaction and cooling, with the gas phase in the upper layer and the liquid phase (i.e., the reaction product phase) in the lower layer. The separation can be performed by any means known in the art. In some specific embodiments, the gas-liquid mixture is passed into a gas-liquid phase separator for gas-liquid separation, the waste gas is discharged from the upper part of the gas-liquid phase separator, and the product is released from the lower part of the gas-liquid phase separator.

[0123] In some specific embodiments, the present invention has no particular limitation on the gas-liquid phase separator, which can be any gas-liquid phase separator known in the art suitable for gas-liquid phase separation, such as a membrane phase separator, a gas-liquid separation tank, and the like.

[0124] Example

[0125] The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0126] In the following examples, the calculation formulas for fluorene conversion, fluorenone selectivity and fluorenone yield are:

[0127] Fluorene conversion rate (%) = (1-fluorene concentration in product / fluorene concentration in raw material) × 100%

[0128] Fluorenone selectivity (%) = Fluorenone concentration in the product / (fluorene conversion rate × fluorene concentration in the raw material) × 100%

[0129] Fluorenone yield (%) = (fluorene conversion rate × fluorenone selectivity) × 100%.

[0130] The microreactor used in the following examples is as follows:

[0131] Micro-packed bed reactor: composed of a stainless steel pipe with an inner diameter of 4 mm and a length of 20 cm (the catalyst prepared in the present invention is used as filler and filled into the pipe until it is full).

[0132] The conversions and selectivities described in the following examples were determined by liquid chromatography.

[0133] Example 1

[0134] A method for preparing a nickel foam-supported cobalt-manganese oxide catalyst comprises the following steps:

[0135] 1) Pretreatment of nickel foam: Use acetone, dilute sulfuric acid and deionized water to ultrasonically clean nickel foam (110 PPI, diameter 4 mm, height 5 mm) in sequence to remove oxides and impurities on the surface of nickel foam, and dry it for later use;

[0136] 2) Loading of cobalt manganese oxide catalyst layer: connect the graphite electrode to the positive pole of the power supply, connect the nickel foam pretreated in step 1) to the negative pole of the power supply, use a precursor solution composed of a 4.2 mol / L transition metal nitrate aqueous solution (Co(NO3)2·6H2O, an aqueous solution of 50 wt% Mn(NO3)2 (Co:Mn molar ratio = 1:1)) as the electrolyte, electrodeposit for 30 s at 5 V, wash with deionized water and dry, and calcine at 400°C for 2 h in an air atmosphere (calcination heating rate of 5°C / min).

[0137] Catalyst morphology and structural characterization

[0138] The macroscopic morphology of nickel foam supported cobalt manganese oxide catalyst is shown in Figure 2. Figure 1 As shown. Figure 1 It can be seen that the catalyst is a black cylindrical block.

[0139] SEM image of nickel foam supported cobalt manganese oxide catalyst Figure 2 As shown. Figure 2It can be seen that the structure of the catalytic layer on the catalyst surface is nanosheets with a thickness of about 10nm.

[0140] EDS image of nickel foam supported cobalt manganese oxide catalyst Figure 3 As shown. Figure 3 It can be seen that the element composition of the catalytic layer on the catalyst surface is: 20.1% Mn, 29.8% Co, 47.1% O (molar fraction).

[0141] A method for preparing fluorenone comprises the following steps:

[0142] Fluorene was dissolved in N-methylpyrrolidone as a substrate solution (the concentration of fluorene was 0.2 mol / L).

[0143] like Figure 4 As shown, a pump and a gas mass flow controller are used to transport the substrate liquid (flow rate is 0.1 mL / min) and pure oxygen (flow rate is 22 sccm) to the micromixer for mixing, and then enter the micropacked bed reactor (composed of 8 pipe sections) connected to the outlet of the micromixer for catalytic oxidation reaction (temperature is 100°C, pressure is 4 MPa, and residence time is 48 min), and then enter the microcoil connected to the outlet of the micropacked bed reactor for cooling (temperature is room temperature), and finally enter the gas-liquid phase separator through the back pressure valve for phase separation, and the liquid at the lower outlet of the gas-liquid phase separator is sampled and tested.

[0144] The results showed that the conversion rate of fluorene was 93%, the selectivity of fluorenone was 95%, and the yield of fluorenone was 88.4%.

[0145] Example 2

[0146] A method for preparing a nickel foam-supported cobalt-nickel oxide catalyst comprises the following steps:

[0147] 1) Pretreatment of nickel foam: Use acetone, dilute sulfuric acid and deionized water to ultrasonically clean nickel foam (110 PPI, diameter 4 mm, height 5 mm) in sequence to remove oxides and impurities on the surface of nickel foam, and dry it for later use;

[0148] 2) Loading of cobalt nickel oxide catalyst layer: connect the graphite electrode to the positive pole of the power supply, connect the nickel foam pretreated in step 1) to the negative pole of the power supply, use a precursor solution composed of a 4.2 mol / L transition metal nitrate aqueous solution (Co(NO3)2·6H2O, Ni(NO3)2·6H2O aqueous solution (Co:Ni molar ratio = 2:1)) as the electrolyte, electrodeposit at 5 V for 30 s, wash with deionized water and then dry, and calcine at 400°C for 2 h in an air atmosphere (calcination heating rate is 5°C / min).

[0149] A method for preparing fluorenone comprises the following steps:

[0150] Fluorene was dissolved in N-methylpyrrolidone as a substrate solution (the concentration of fluorene was 0.2 mol / L).

[0151] A pump and a gas mass flow controller are used to transport the substrate liquid (flow rate is 0.1 mL / min) and pure oxygen (flow rate is 22 sccm) to the micromixer for mixing, and then enter the micro-packed bed reactor (composed of 4 pipe sections) connected to the outlet of the micromixer for catalytic oxidation reaction (temperature is 120°C, pressure is 4 MPa, and residence time is 24 min), and then enter the microcoil connected to the outlet of the micro-packed bed reactor for cooling (temperature is room temperature), and finally enter the gas-liquid phase separator through the back pressure valve for phase separation, and the liquid at the lower outlet of the gas-liquid phase separator is sampled and tested.

[0152] The results showed that the conversion rate of fluorene was 92%, the selectivity of fluorenone was 91%, and the yield of fluorenone was 83.7%.

[0153] Example 3

[0154] A method for preparing a nickel foam-supported manganese-nickel oxide catalyst comprises the following steps:

[0155] 1) Pretreatment of nickel foam: Use acetone, dilute sulfuric acid and deionized water to ultrasonically clean nickel foam (110 PPI, diameter 4 mm, height 5 mm) in sequence to remove oxides and impurities on the surface of nickel foam, and dry it for later use;

[0156] 2) Loading of manganese nickel oxide catalyst layer: connect the graphite electrode to the positive pole of the power supply, connect the nickel foam pretreated in step 1) to the negative pole of the power supply, use a precursor solution composed of a 4.2 mol / L transition metal nitrate aqueous solution (50 wt% Mn(NO3)2, Ni(NO3)2·6H2O aqueous solution (Mn:Ni molar ratio = 4:1)) as the electrolyte, electrodeposit for 30 s at 5 V, wash with deionized water and then dry, and calcine at 400°C for 2 h in an air atmosphere (calcination heating rate of 5°C / min).

[0157] A method for preparing fluorenone comprises the following steps:

[0158] Fluorene was dissolved in N-methylpyrrolidone as a substrate solution (the concentration of fluorene was 0.2 mol / L).

[0159] A pump and a gas mass flow controller are used to transport the substrate liquid (flow rate is 0.1 mL / min) and pure oxygen (flow rate is 22 sccm) to the micromixer for mixing, and then enter the micro-packed bed reactor (composed of 8 pipe sections) connected to the outlet of the micromixer for catalytic oxidation reaction (temperature is 100°C, pressure is 4 MPa, and residence time is 48 min), and then enter the microcoil connected to the outlet of the micro-packed bed reactor for cooling (temperature is room temperature), and finally enter the gas-liquid phase separator through the back pressure valve for phase separation, and the liquid at the lower outlet of the gas-liquid phase separator is sampled and tested.

[0160] The results showed that the conversion rate of fluorene was 80%, the selectivity of fluorenone was 99%, and the yield of fluorenone was 79.2%.

[0161] Example 4

[0162] A method for preparing a nickel foam-supported manganese-cobalt-nickel oxide catalyst comprises the following steps:

[0163] 1) Pretreatment of nickel foam: Use acetone, dilute sulfuric acid and deionized water to ultrasonically clean nickel foam (110 PPI, diameter 4 mm, height 5 mm) in sequence to remove oxides and impurities on the surface of nickel foam, and dry it for later use;

[0164] 2) Loading of manganese cobalt nickel oxide catalyst layer: connect the graphite electrode to the positive pole of the power supply, connect the nickel foam pretreated in step 1) to the negative pole of the power supply, use a precursor solution composed of 4.2 mol / L transition metal nitrate aqueous solution (Co(NO3)2·6H2O, Ni(NO3)2·6H2O, 50 wt% Mn(NO3)2 aqueous solution (Mn:Co:Ni molar ratio = 4:2:1)) as the electrolyte, electrodeposit at 5 V for 30 s, wash with deionized water and then dry, and calcine at 400°C for 2 h in an air atmosphere (calcination heating rate is 5°C / min).

[0165] A method for preparing fluorenone comprises the following steps:

[0166] Fluorene was dissolved in N-methylpyrrolidone as a substrate solution (the concentration of fluorene was 0.2 mol / L).

[0167] A pump and a gas mass flow controller are used to transport the substrate liquid (flow rate is 0.1 mL / min) and pure oxygen (flow rate is 22 sccm) to the micromixer for mixing, and then enter the micro-packed bed reactor (composed of 4 pipe sections) connected to the outlet of the micromixer for catalytic oxidation reaction (temperature is 120°C, pressure is 4 MPa, and residence time is 24 min), and then enter the microcoil connected to the outlet of the micro-packed bed reactor for cooling (temperature is room temperature), and finally enter the gas-liquid phase separator through the back pressure valve for phase separation, and the liquid at the lower outlet of the gas-liquid phase separator is sampled and tested.

[0168] The results showed that the conversion rate of fluorene was 95%, the selectivity of fluorenone was 90%, and the yield of fluorenone was 85.5%.

[0169] Example 5

[0170] A method for preparing a nickel foam-supported manganese-cobalt-nickel oxide catalyst comprises the following steps:

[0171] 1) Pretreatment of nickel foam: Use acetone, dilute sulfuric acid and deionized water to ultrasonically clean nickel foam (110 PPI, diameter 4 mm, height 5 mm) in sequence to remove oxides and impurities on the surface of nickel foam, and dry it for later use;

[0172] 2) Loading of manganese cobalt nickel oxide catalyst layer: connect the graphite electrode to the positive pole of the power supply, connect the nickel foam pretreated in step 1) to the negative pole of the power supply, use a precursor solution composed of 4.2 mol / L transition metal nitrate aqueous solution (Co(NO3)2·6H2O, Ni(NO3)2·6H2O, 50 wt% Mn(NO3)2 aqueous solution (Mn:Co:Ni molar ratio = 4:2:1)) as the electrolyte, electrodeposit at 5 V for 30 s, wash with deionized water and then dry, and calcine at 400°C for 2 h in an air atmosphere (calcination heating rate is 5°C / min).

[0173] A method for preparing fluorenone comprises the following steps:

[0174] Fluorene was dissolved in N-methylpyrrolidone as a substrate solution (the concentration of fluorene was 0.2 mol / L).

[0175] A pump and a gas mass flow controller are used to transport the substrate liquid (flow rate is 0.1 mL / min) and pure oxygen (flow rate is 22 sccm) to the micromixer for mixing, and then enter the micro-packed bed reactor (composed of 8 pipe sections) connected to the outlet of the micromixer for catalytic oxidation reaction (temperature is 100°C, pressure is 4 MPa, and residence time is 48 min), and then enter the microcoil connected to the outlet of the micro-packed bed reactor for cooling (temperature is room temperature), and finally enter the gas-liquid phase separator through the back pressure valve for phase separation, and the liquid at the lower outlet of the gas-liquid phase separator is sampled and tested.

[0176] The results showed that the conversion rate of fluorene was 94%, the selectivity of fluorenone was 98%, and the yield of fluorenone was 92.1%.

[0177] Example 6

[0178] A method for preparing a nickel foam-supported manganese-cobalt-nickel oxide catalyst comprises the following steps:

[0179] 1) Pretreatment of nickel foam: Use acetone, dilute sulfuric acid and deionized water to ultrasonically clean nickel foam (110 PPI, diameter 4 mm, height 5 mm) in sequence to remove oxides and impurities on the surface of nickel foam, and dry it for later use;

[0180] 2) Loading of manganese cobalt nickel oxide catalyst layer: connect the graphite electrode to the positive pole of the power supply, connect the nickel foam pretreated in step 1) to the negative pole of the power supply, use a precursor solution composed of 4.2 mol / L transition metal nitrate aqueous solution (Co(NO3)2·6H2O, Ni(NO3)2·6H2O, 50 wt% Mn(NO3)2 aqueous solution (Mn:Co:Ni molar ratio = 4:2:1)) as the electrolyte, electrodeposit at 5 V for 30 s, wash with deionized water and then dry, and calcine at 400°C for 2 h in an air atmosphere (calcination heating rate is 5°C / min).

[0181] A method for preparing fluorenone comprises the following steps:

[0182] Fluorene was dissolved in N-methylpyrrolidone as a substrate solution (the concentration of fluorene was 0.2 mol / L).

[0183] A pump and a gas mass flow controller are used to transport the substrate liquid (flow rate is 0.1 mL / min) and pure oxygen (flow rate is 11 sccm) to the micromixer for mixing, and then enter the micro-packed bed reactor (composed of 8 pipe sections) connected to the outlet of the micromixer for catalytic oxidation reaction (temperature is 100°C, pressure is 2 MPa, and residence time is 48 min), and then enter the microcoil connected to the outlet of the micro-packed bed reactor for cooling (temperature is room temperature), and finally enter the gas-liquid phase separator through the back pressure valve for phase separation, and the liquid at the lower outlet of the gas-liquid phase separator is sampled and tested.

[0184] The results showed that the conversion rate of fluorene was 90%, the selectivity of fluorenone was 99%, and the yield of fluorenone was 89.1%.

[0185] Example 7

[0186] A method for preparing a nickel foam-supported manganese-cobalt-nickel oxide catalyst comprises the following steps:

[0187] 1) Pretreatment of nickel foam: Use acetone, dilute sulfuric acid and deionized water to ultrasonically clean nickel foam (110 PPI, diameter 4 mm, height 5 mm) in sequence to remove oxides and impurities on the surface of nickel foam, and dry it for later use;

[0188] 2) Loading of manganese cobalt nickel oxide catalyst layer: connect the graphite electrode to the positive pole of the power supply, connect the nickel foam pretreated in step 1) to the negative pole of the power supply, use a precursor solution composed of 4.2 mol / L transition metal nitrate aqueous solution (Co(NO3)2·6H2O, Ni(NO3)2·6H2O, 50 wt% Mn(NO3)2 aqueous solution (Mn:Co:Ni molar ratio = 4:2:1)) as the electrolyte, electrodeposit at 5 V for 30 s, wash with deionized water and then dry, and calcine at 400°C for 2 h in an air atmosphere (calcination heating rate is 5°C / min).

[0189] A method for preparing fluorenone comprises the following steps:

[0190] Fluorene was dissolved in p-xylene as a substrate liquid (the concentration of fluorene was 0.2 mol / L).

[0191] A pump and a gas mass flow controller are used to transport the substrate liquid (flow rate is 0.1 mL / min) and pure oxygen (flow rate is 22 sccm) to the micromixer for mixing, and then enter the micro-packed bed reactor (composed of 8 pipe sections) connected to the outlet of the micromixer for catalytic oxidation reaction (temperature is 100°C, pressure is 2 MPa, and residence time is 48 min), and then enter the microcoil connected to the outlet of the micro-packed bed reactor for cooling (temperature is room temperature), and finally enter the gas-liquid phase separator through the back pressure valve for phase separation, and the liquid at the lower outlet of the gas-liquid phase separator is sampled and tested.

[0192] The results showed that the conversion rate of fluorene was 75%, the selectivity of fluorenone was 99%, and the yield of fluorenone was 74.3%.

Claims

1. A catalyst suitable for a micro-packed bed reactor, characterized in that: The catalyst uses foamed metal as a carrier, and a transition metal oxide with a spinel structure is loaded on the surface and / or in the pores of the foamed metal; in, The transition metal oxide is present on the surface and / or in the pores of the foam metal in the form of nanosheets with a thickness of 5 to 20 nm. The pore density of the foam metal is 40-120 PPI.

2. The catalyst according to claim 1, characterized in that In the catalyst, the loading amount of the transition metal oxide is 0.01 to 0.1 g / cm based on the volume of the foamed metal. 3 , preferably 0.03 to 0.05 g / cm 3 ; The content of oxygen in the transition metal oxide is 40 mol% to 70 mol%.

3. The catalyst according to claim 1 or 2, characterized in that The foam metal includes any one of foam nickel, foam copper and foam iron, preferably foam nickel; The transition metal includes a combination of two or more of cobalt, manganese and nickel.

4. A method for preparing a catalyst according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: 1) Pretreatment of the foam metal: performing surface treatment on the foam metal to remove oxides and impurities on the surface of the foam metal; 2) Loading of transition metal oxide catalyst layer: An aqueous solution containing transition metal salt is used as a precursor solution, and electrodeposition is performed at room temperature, followed by calcination to obtain the catalyst layer.

5. The preparation method according to claim 4, characterized in that: In step 2), The concentration of the transition metal salt in the precursor solution is 1-6 mol / L.

6. The preparation method according to claim 4 or 5, characterized in that: In step 2), The voltage of the electrodeposition is 1 to 6 V, and the time of the electrodeposition is 10 to 60 s; The calcination temperature is 200-600° C., and the calcination time is 1-4 hours.

7. Use of the catalyst according to any one of claims 1 to 3 in the preparation of 9-fluorenone by oxidation of fluorene, wherein a microfilled reactor is used in the preparation.

8. A method for preparing 9-fluorenone, characterized in that: The following steps are involved: The oxygen-containing gas and the reaction solvent containing fluorene are introduced into a micro mixer for mixing, and then enter into a micro packed bed reactor for catalytic oxidation reaction, and then cooled in a micro coil, and then separated into gas and liquid in a gas-liquid phase separator to obtain 9-fluorenone; Wherein, the filler in the micro-packed bed reactor is the catalyst according to any one of claims 1 to 3; and the micro-packed bed reactor and the micro-coil are each independently placed in a temperature-controlled box.

9. The preparation method according to claim 8, characterized in that: The molar ratio of oxygen in the oxygen-containing gas to fluorene is (10-60):1; The oxygen concentration in the oxygen-containing gas is 21 to 100%.

10. The preparation method according to claim 8 or 9, characterized in that: The temperature of the catalytic oxidation reaction is 80 to 140°C; The catalytic oxidation reaction time is 10min to 60min; The pressure of the catalytic oxidation reaction is 0.5-5 MPa.

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