Catalyst for preparing acetophenone by oxidizing ethylbenzene as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst for preparing acetophenone by oxidizing ethylbenzene as well as a preparation method and application of the catalyst, and belongs to the technical field of acetophenone synthesis. The preparation method comprises the following steps: uniformly mixing ammonia water, m-aminophenol and a formaldehyde solution, and carrying out hydrothermal reaction to obtain a polymer precursor; washing and drying the polymer precursor, and then carrying out carbonization treatment to obtain nitrogen-doped carbon spheres; sequentially adding cobalt salt and the nitrogen-doped carbon spheres into a solvent, stirring, washing, drying, and carbonizing to obtain cobalt oxide-loaded carbon spheres; and 2-methylimidazole and cobalt salt are respectively dissolved in the solvent and then uniformly mixed, and the cobalt oxide-loaded carbon spheres are added for aging treatment to obtain the catalyst for preparing acetophenone by oxidizing ethylbenzene. The invention also discloses the catalyst prepared by the method and used for preparing acetophenone by oxidizing ethylbenzene and application of the catalyst. The catalyst for preparing acetophenone by oxidizing ethylbenzene can solve the problems of short service life, low ethylbenzene conversion rate and low acetophenone selectivity of the existing catalyst for preparing acetophenone from ethylbenzene, and has wide application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of acetophenone synthesis, and specifically relates to a catalyst for the oxidation of ethylbenzene to acetophenone, a preparation method thereof, and an application thereof. Background Art

[0002] The oxidation of ethylbenzene to acetophenone, as an important technology in the field of organic synthesis, has received extensive attention in recent years. Acetophenone, as an important organic chemical raw material, is widely used in the manufacture of products such as drugs, resins, and flavoring agents. Currently, there are various types of catalysts for catalyzing the preparation of acetophenone from ethylbenzene, mainly including traditional copper oxide catalysts and ammonium phosphomolybdate with an oxidized chain, etc. For such catalysts, although they show certain catalytic activity in the oxidation reaction of ethylbenzene, their catalytic life is relatively short. After long-term use, the catalytic activity will be significantly reduced, resulting in a decrease in reaction efficiency. Secondly, during the catalytic oxidation reaction of ethylbenzene by some catalysts, a large amount of by-products (such as over-oxidation products like benzaldehyde and benzoic acid) are often generated, leading to low purity of the finished product and increasing the difficulty of subsequent separation and purification.

[0003] How to obtain a more efficient and environmentally friendly catalytic system for the oxidation of ethylbenzene to acetophenone, so as to improve the conversion rate and selectivity of the ethylbenzene oxidation reaction, reduce production costs, and promote the industrial application of this technology is a technical difficulty that urgently needs to be solved in the current field. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a catalyst for the oxidation of ethylbenzene to acetophenone, a preparation method thereof, and an application thereof, so as to solve the problems of short life of the existing catalysts for the preparation of acetophenone from ethylbenzene, low conversion rate of ethylbenzene, and low selectivity of acetophenone.

[0005] The technical solution adopted to solve its technical problem is to provide a preparation method of a catalyst for the oxidation of ethylbenzene to acetophenone, including the following steps:

[0006] (1) Mix ammonia water, m-aminophenol, and formaldehyde solution evenly and carry out hydrothermal reaction to obtain a polymer precursor;

[0007] (2) Wash and dry the polymer precursor, and then carry out carbonization treatment to obtain nitrogen-doped carbon spheres;

[0008] (3) Add cobalt salt and nitrogen-doped carbon spheres to the solvent in sequence, stir, wash, dry, and then carry out carbonization treatment to obtain carbon spheres loaded with cobalt oxide;

[0009] (4) Take 2-methylimidazole and cobalt salt and dissolve them in the solvent respectively and then mix evenly, add the carbon spheres loaded with cobalt oxide for aging treatment, and thus obtain the catalyst for the oxidation of ethylbenzene to acetophenone.

[0010] The beneficial effects of the present invention adopting the above technical solutions are as follows: In the present invention, cobalt oxide is loaded on nitrogen-doped carbon spheres, and then cobalt-organic framework (Co-MOF) is wrapped outside it to form dual active centers; both cobalt (Co) in cobalt oxide and Co-MOF has redox activity, which can effectively promote the oxidation reaction of ethylbenzene to generate acetophenone; at the same time, the porous structure of Co-MOF and the properties of organic ligands can guide substrate molecules (ethylbenzene and oxidant) to the vicinity of cobalt active centers, improve the selectivity of the reaction, and reduce the generation of by-products; secondly, the cobalt oxide loaded on the nitrogen-doped carbon material is wrapped in Co-MOF, which can not only catalyze synergistically with Co-MOF, but also prevent cobalt from leaching and extend the service life of the catalyst; in addition, the pore structure of Co-MOF can screen reactants and products, limit the reaction path and the generation of products, thereby inhibiting the generation of by-products such as tar.

[0011] After the nitrogen-doped carbon spheres are prepared, cobalt oxide loaded on the nitrogen-doped carbon spheres is prepared through hydrothermal reaction and carbonization treatment, realizing the doping of cobalt oxide. The cobalt oxide is loaded on the surface or pores of the nitrogen-doped carbon material in the form of nanoparticles and has high redox activity; at this time, Co-MOF is wrapped on its surface, and Co therein is uniformly distributed in the framework structure of MOF in the form of metal nodes at the molecular level, highly ordered and uniformly dispersed, solving the problem of easy agglomeration caused by Co doping.

[0012] Preferably, step (1) includes the following steps: Dissolve ammonia water in an ethanol aqueous solution, add m-aminophenol, reflux and stir at 25-35 °C in an oil bath for 25-35 min, then add formaldehyde solution and reflux and stir at 25-35 °C in an oil bath for 3-5 h, and heat to 80-150 °C at a heating rate of 3-5 °C / min for hydrothermal reaction for 22-26 h to obtain a polymer precursor.

[0013] More preferably, step (1) includes the following steps: Dissolve ammonia water in an ethanol aqueous solution, add m-aminophenol, reflux and stir at 30 °C in an oil bath for 30 min, then add formaldehyde solution and reflux and stir at 30 °C in an oil bath for 4 h, and heat to 100 °C at a heating rate of 5 °C / min for hydrothermal reaction for 24 h to obtain a polymer precursor.

[0014] More preferably, the material ratio of ammonia water, m-aminophenol and formaldehyde solution is (0.1-0.3) mL: (0.7-0.9) g: (0.4-0.6) mL; the volume concentration of the ethanol aqueous solution is 20-30%; the molar concentration of the formaldehyde solution is 10-15 M.

[0015] More preferably, the material ratio of ammonia water, m-aminophenol and formaldehyde solution is 0.2 mL: 0.83 g: 0.56 mL; the volume concentration of the ethanol aqueous solution is 28.57%; the molar concentration of the formaldehyde solution is 13.44 M.

[0016] Preferably, in steps (2) and (3), the washing is performed by washing with deionized water and ethanol in sequence; the drying temperature is 50-70 °C and the time is 8-12 h for both; the conditions for the carbonization treatment are: under an inert atmosphere, heating to 350-450 °C at a rate of 1-3 °C / min and holding for 2-4 h, and then heating to 450-550 °C at a rate of 1-2 °C / min and holding for 1.5-2.5 h.

[0017] More preferably, in steps (2) and (3), the drying temperature is 60 °C and the time is 12 h for both; the conditions for the carbonization treatment are: under an inert atmosphere, heating to 400 °C at a rate of 2 °C / min and holding for 3 h, and then heating to 500 °C at a rate of 1 °C / min and holding for 2 h.

[0018] Preferably, in steps (3) and (4), the cobalt salt is cobalt nitrate hexahydrate; in step (3), the solvent is a mixed solution of ammonia water and water mixed at a volume ratio of 1: (3-5); the stirring in step (3) is carried out under an oil bath condition, the temperature is 75-85 °C, and the time is 7-9 h; the mass ratio of the cobalt salt to the nitrogen-doped carbon spheres in step (3) is 0.6-1: 0.5.

[0019] More preferably, in step (3), the solvent is a mixed solution of ammonia water and water mixed at a volume ratio of 1:4; the stirring temperature in step (3) is 80 °C and the time is 8 h; the mass ratio of the cobalt salt to the nitrogen-doped carbon spheres in step (3) is 0.8: 0.5.

[0020] Preferably, in step (4), the solvent is methanol; the aging treatment temperature is 20-35 °C and the time is 22-26 h; the mass ratio of 2-methylimidazole, cobalt salt and the carbon spheres loaded with cobalt oxide is 5-8: 2-3: 1.

[0021] More preferably, the aging treatment temperature is 25 °C and the time is 24 h; the mass ratio of 2-methylimidazole, cobalt salt and the carbon spheres loaded with cobalt oxide is 6.56: 2.91: 1.

[0022] More preferably, after the aging treatment, it is washed with methanol 5 times and then placed in a vacuum dryer at 60 °C for 12 h to obtain the catalyst for the preparation of acetophenone from ethylbenzene oxidation.

[0023] The present invention also provides a catalyst for the preparation of acetophenone from ethylbenzene oxidation prepared by the above preparation method.

[0024] The beneficial effects of the present invention adopting the above technical solutions are as follows: For the catalyst for preparing acetophenone from ethylbenzene oxidation obtained in the present invention, the nitrogen-doped carbon spheres, the supported cobalt oxide and the cobalt in Co-MOF in its structure have a synergistic effect, jointly improving the overall activity of the catalyst; meanwhile, Co-MOF is wrapped outside the nitrogen-doped carbon material, preventing the loss of cobalt and improving the stability of the catalyst. The pore structure of Co-MOF restricts the reaction path and the generation of by-products, improving the selectivity of the reaction. When the catalyst for preparing acetophenone from ethylbenzene oxidation obtained in the present invention is used in the selective oxidation of ethylbenzene to prepare acetophenone assisted by carbon dioxide, it has the advantages of long service life, stable reaction, high conversion rate of ethylbenzene and high selectivity of acetophenone.

[0025] The present invention also provides the application of the above-mentioned catalyst for preparing acetophenone from ethylbenzene oxidation in the selective oxidation of ethylbenzene to prepare acetophenone assisted by carbon dioxide.

[0026] Preferably, the application of the catalyst for preparing acetophenone from ethylbenzene oxidation in the selective oxidation of ethylbenzene to prepare acetophenone assisted by carbon dioxide includes the following steps:

[0027] Add the catalyst for preparing acetophenone from ethylbenzene oxidation and ethylbenzene into a high-pressure reactor, and react under the action of an oxidant and carbon dioxide to obtain the target product acetophenone.

[0028] More preferably, the reaction pressure is 2-4 Mpa, the temperature is 75-85 °C, and the time is 9-11 h; the oxidant is tert-butyl hydroperoxide, hydrogen peroxide or oxygen; the liquid ratio of ethylbenzene to the catalyst for preparing acetophenone from ethylbenzene oxidation is (20-30) mL:1 g.

[0029] More preferably, the reaction pressure is 3 Mpa, the temperature is 80 °C, and the time is 10 h; the oxidant is tert-butyl hydroperoxide; the liquid ratio of ethylbenzene to the catalyst for preparing acetophenone from ethylbenzene oxidation is 28 mL:1 g.

[0030] The present invention has the following beneficial effects:

[0031] The catalyst for preparing acetophenone from ethylbenzene oxidation of the present invention is simply synthesized. When it is used for the selective oxidation of ethylbenzene to prepare acetophenone, assisted by carbon dioxide, the catalyst for preparing acetophenone from ethylbenzene oxidation can efficiently selectively oxidize ethylbenzene to acetophenone. The reaction conditions are mild, the conversion rate of ethylbenzene, the selectivity and purity of acetophenone are relatively high, and the catalyst effect does not decrease significantly after repeated use for many times, and the stability is good; meanwhile, carbon dioxide is used as an auxiliary gas in the reaction process, reducing environmental pollution, and having high economic value and practical value. Description of the Drawings

[0032] Figure 1 It is the transmission electron microscope TEM image of the catalyst for preparing acetophenone from ethylbenzene oxidation;

[0033] Figure 2 Catalytic principle diagram of the catalyst for preparing acetophenone by oxidizing ethylbenzene in the selective oxidation of ethylbenzene to acetophenone assisted by carbon dioxide. Specific embodiments

[0034] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further describes the present invention in detail in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0035] Therefore, the following detailed description of the provided embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0036] The features and performance of the present invention are further described in detail below in conjunction with embodiments.

[0037] Example 1

[0038] A catalyst for preparing acetophenone by oxidizing ethylbenzene, and its preparation method includes the following steps:

[0039] (1) Dissolve 0.2 mL of ammonia water in 56 mL of an ethanol aqueous solution with a volume concentration of 28.57%. After adding 0.83 g of m-aminophenol, reflux and stir in an oil bath at 30 °C for 30 min, then add 0.56 mL of a formaldehyde solution with a molar concentration of 13.44 M and reflux and stir in an oil bath at 30 °C for 4 h to obtain a mixed solution; transfer the mixed solution to a reaction kettle with a polytetrafluoroethylene lining, and heat it to 100 °C in a homogeneous reactor at a heating rate of 5 °C / min for a hydrothermal reaction for 24 h to obtain a polymer precursor;

[0040] (2) Wash the polymer precursor with deionized water and ethanol in sequence, collect the washed solid, place it in an oven at 60 °C for drying for 12 h, take it out after drying, and place it in a nitrogen atmosphere and heat it to 400 °C at a rate of 2 °C / min and hold for 3 h, then heat it to 500 °C at a rate of 1 °C / min and hold for 2 h for carbonization treatment to obtain nitrogen-doped carbon spheres, denoted as NCS;

[0041] (3) Weigh 0.8 g of cobalt nitrate hexahydrate and add it to a round-bottom flask containing 10 mL of ammonia water and 40 mL of deionized water. Stir at 25 °C until dissolved. Then add 0.5 g of nitrogen-doped carbon spheres and mix well. Transfer the round-bottom flask to an 80 °C oil bath and stir for 8 h. After taking it out and cooling, wash it successively with deionized water and ethanol. Collect the washed solid and place it in an oven at 60 °C for drying for 12 h. After drying, take it out and place it under a nitrogen atmosphere. Heat it to 400 °C at a rate of 2 °C / min and hold for 3 h, then heat it to 500 °C at a rate of 1 °C / min and hold for 2 h for carbonization treatment to obtain carbon spheres loaded with cobalt oxide, denoted as CoO x / NCS;

[0042] (4) Separately dissolve 6.56 g of 2-methylimidazole and 2.91 g of cobalt nitrate hexahydrate in 100 mL of methanol. Then stir and mix the two. Add 1 g of carbon spheres loaded with cobalt oxide and age at 25 °C for 24 h. Centrifuge to collect the purple precipitate, wash it 5 times with methanol, and place it in a vacuum dryer at 60 °C for 12 h to obtain the catalyst for the oxidation of ethylbenzene to acetophenone, denoted as [CoO x / NCS]@Co-MOF.

[0043] The transmission electron microscope (TEM) characterization of the catalyst for the oxidation of ethylbenzene to acetophenone prepared in this example is as Figure 1 shown.

[0044] This example also provides the application of the above catalyst for the oxidation of ethylbenzene to acetophenone in the selective oxidation of ethylbenzene with carbon dioxide assistance to prepare acetophenone, including the following steps:

[0045] Take 220 mL of a tert-butyl hydroperoxide solution with a mass concentration of 70 wt% and place it in a constant-pressure burette funnel. Add 60 mL of ethylbenzene, shake and extract. After standing until phase separation, add saturated sodium chloride solution. After the organic phase and the aqueous phase are completely separated, remove the lower aqueous phase to obtain the reaction solution. Take 10 mL of the reaction solution into a high-pressure reaction kettle. The reaction solution contains 2.8 mL of ethylbenzene, and add 0.1 g of the catalyst for the oxidation of ethylbenzene to acetophenone. At the same time, introduce carbon dioxide and pressurize to 3 Mpa, and react at 80 °C for 10 h. After the reaction, centrifuge to separate the product solution and the catalyst for the oxidation of ethylbenzene to acetophenone.

[0046] After the catalyst for the oxidation of ethylbenzene to acetophenone is separated, a gas chromatograph (GC-2018) is used to detect and analyze various components in the product solution to determine the conversion rate, selectivity, and product purity of the reaction. The analysis shows that the ethylbenzene conversion rate in this example is 98.3%, the acetophenone selectivity is 99.8%, and the acetophenone purity is 99.5%.

[0047] The separation of the product solution and the purification of acetophenone can be carried out by distillation.

[0048] The prepared catalyst for the oxidation of ethylbenzene to acetophenone was subjected to a cyclic stability test. Specifically, the prepared catalyst for the oxidation of ethylbenzene to acetophenone was reused in the selective oxidation of ethylbenzene to acetophenone assisted by carbon dioxide. After 6 cycles, its selectivity for acetophenone was 99.8%, and the conversion rate of ethylbenzene was 95.6%.

[0049] The catalytic reaction principle of the catalyst for the oxidation of ethylbenzene to acetophenone in the selective oxidation of ethylbenzene to acetophenone assisted by carbon dioxide is as follows Figure 2 shown. During the catalytic reaction process, carbon dioxide can stabilize the free radicals generated during the reaction, such as ethylbenzene free radicals, etc., reduce the activity of the free radicals, and reduce the occurrence of side reactions, making the reaction more conducive to the formation of acetophenone and improving the selectivity and yield of the reaction; the presence of carbon dioxide can adjust the physical and chemical properties of the reaction system, such as polarity, viscosity, etc., thereby affecting the interaction between the reactants and the catalyst and the mass transfer and heat transfer processes of the reaction, which helps to improve the reaction efficiency; carbon dioxide will interact with the catalyst, change the electronic structure and surface properties of the catalyst, and then promote the activity of the catalyst, making ethylbenzene more easily oxidized to acetophenone. At the same time, in the oxidation reaction of ethylbenzene, the free radical reaction is an important link. Carbon dioxide can interact with some active free radicals during the reaction process, such as reacting with carbon free radicals, thereby regulating the reaction process and making the reaction more inclined to generate acetophenone rather than generating tar through side reactions such as uncontrolled polymerization of free radicals.

[0050] Example 2

[0051] A catalyst for the oxidation of ethylbenzene to acetophenone, and its preparation method includes the following steps

[0052] (1) Dissolve 0.1 mL of ammonia water in 56 mL of an ethanol aqueous solution with a volume concentration of 20%. After adding 0.7 g of m-aminophenol, reflux and stir at 25 °C in an oil bath for 35 min, and then add 0.4 mL of a formaldehyde solution with a molar concentration of 10 M and reflux and stir at 25 °C in an oil bath for 5 h to obtain a mixed solution; transfer the mixed solution to a reaction kettle with a polytetrafluoroethylene inner lining, and heat it to 80 °C in a homogeneous reactor at a heating rate of 3 °C / min for 26 h of hydrothermal reaction to obtain a polymer precursor;

[0053] (2) Wash the polymer precursor with deionized water and ethanol in sequence, collect the washed solid, place it in an oven at 50 °C for drying for 12 h, take it out after drying, and place it in a nitrogen atmosphere and heat it to 350 °C at a rate of 1 °C / min and hold for 4 h, and then heat it to 450 °C at a rate of 1 °C / min and hold for 2.5 h for carbonization treatment to obtain nitrogen-doped carbon spheres;

[0054] (3) Weigh 0.6 g of cobalt nitrate hexahydrate and add it to a round-bottom flask containing 10 mL of ammonia water and 30 mL of deionized water. Stir at 25 °C until dissolved. Then add 0.5 g of nitrogen-doped carbon spheres and mix well. Transfer the round-bottom flask to a 75 °C oil bath and stir for 9 h. After taking it out and cooling, wash it successively with deionized water and ethanol. Collect the washed solid and place it in an oven at 50 °C for drying for 12 h. After drying, take it out and place it under a nitrogen atmosphere. Heat it to 350 °C at a rate of 1 °C / min and hold for 4 h, then heat it to 450 °C at a rate of 1 °C / min and hold for 2.5 h for carbonization treatment to obtain carbon spheres loaded with cobalt oxide;

[0055] (4) Separately dissolve 5 g of 2-methylimidazole and 2 g of cobalt nitrate hexahydrate in 100 mL of methanol. Then stir and mix the two, add 1 g of carbon spheres loaded with cobalt oxide, and age at 20 °C for 26 h. Centrifuge to collect the purple precipitate, wash it 5 times with methanol, and vacuum dry it at 60 °C for 12 h to obtain the catalyst for the oxidation of ethylbenzene to acetophenone.

[0056] This example also provides the application of the above-mentioned catalyst for the oxidation of ethylbenzene to acetophenone in the selective oxidation of ethylbenzene to acetophenone assisted by carbon dioxide, including the following steps:

[0057] Take 220 mL of a tert-butyl hydroperoxide solution with a mass concentration of 70 wt% and place it in a constant-pressure burette funnel. Add 60 mL of ethylbenzene, shake and extract, let it stand until phase separation, then add saturated sodium chloride solution. After the organic phase and the aqueous phase are completely separated, remove the lower aqueous phase to obtain the reaction solution. Take 10 mL of the reaction solution into a high-pressure reactor. The reaction solution contains 2.8 mL of ethylbenzene, and add 0.1 g of the catalyst for the oxidation of ethylbenzene to acetophenone to it. At the same time, introduce carbon dioxide and pressurize it to 2 Mpa, and react at 75 °C for 11 h. After the reaction is completed, centrifuge to separate the product solution and the catalyst for the oxidation of ethylbenzene to acetophenone.

[0058] Example 3

[0059] A catalyst for the oxidation of ethylbenzene to acetophenone, and its preparation method includes the following steps:

[0060] (1) Dissolve 0.3 mL of ammonia water in 56 mL of an ethanol aqueous solution with a volume concentration of 30%. Add 0.9 g of m-aminophenol and reflux and stir in a 35 °C oil bath for 25 min. Then add 0.6 mL of a formaldehyde solution with a molar concentration of 15 M and reflux and stir in a 35 °C oil bath for 3 h to obtain a mixed solution. Transfer the mixed solution to a reaction kettle with a polytetrafluoroethylene inner lining, and heat it to 150 °C in a homogeneous reactor at a heating rate of 5 °C / min for hydrothermal reaction for 22 h to obtain a polymer precursor;

[0061] (2) Wash the polymer precursor with deionized water and ethanol successively, collect the washed solid and dry it in an oven at 50 °C for 12 h. After drying, take it out and heat it to 450 °C at a rate of 3 °C / min in a nitrogen atmosphere and hold for 2 h, then heat it to 550 °C at a rate of 2 °C / min and hold for 1.5 h for carbonization treatment to obtain nitrogen-doped carbon spheres;

[0062] (3) Weigh 1 g of cobalt nitrate hexahydrate and add it to a round-bottom flask containing 10 mL of ammonia water and 50 mL of deionized water, stir at 25 °C until dissolved, then add 0.5 g of nitrogen-doped carbon spheres and mix evenly. Transfer the round-bottom flask to an 85 °C oil bath and stir for 7 h. After taking it out and cooling, wash it with deionized water and ethanol successively, collect the washed solid and dry it in an oven at 50 °C for 12 h. After drying, take it out and heat it to 450 °C at a rate of 3 °C / min in a nitrogen atmosphere and hold for 2 h, then heat it to 550 °C at a rate of 2 °C / min and hold for 1.5 h for carbonization treatment to obtain carbon spheres loaded with cobalt oxide;

[0063] (4) Separately dissolve 8 g of 2-methylimidazole and 3 g of cobalt nitrate hexahydrate in 100 mL of methanol, then stir and mix the two, add 1 g of carbon spheres loaded with cobalt oxide, and age at 35 °C for 22 h. Centrifuge to collect the purple precipitate, wash it 5 times with methanol, and vacuum dry it at 60 °C for 12 h to obtain the catalyst for the oxidation of ethylbenzene to acetophenone.

[0064] This example also provides the application of the above-mentioned catalyst for the oxidation of ethylbenzene to acetophenone in the selective oxidation of ethylbenzene to acetophenone assisted by carbon dioxide, including the following steps:

[0065] Take 220 mL of tert-butyl hydroperoxide solution with a mass concentration of 70 wt% and place it in a constant-pressure burette funnel. Add 60 mL of ethylbenzene, shake and extract, let it stand until phase separation, then add saturated sodium chloride solution. After the organic phase and the aqueous phase are completely separated, remove the lower aqueous phase to obtain the reaction solution; Take 10 mL of the reaction solution into a high-pressure reaction kettle. The reaction solution contains 2.8 mL of ethylbenzene, and add 0.1 g of the catalyst for the oxidation of ethylbenzene to acetophenone to it. At the same time, introduce carbon dioxide to pressurize to 4 Mpa, react at 85 °C for 9 h. After the reaction is completed, centrifuge to separate the product solution and the catalyst for the oxidation of ethylbenzene to acetophenone.

[0066] Comparative Example 1

[0067] A preparation method of a catalyst for the oxidation of ethylbenzene to acetophenone. Compared with the preparation method of the catalyst for the oxidation of ethylbenzene to acetophenone in Example 1, the difference is that step (4) is cancelled, and the carbon spheres loaded with cobalt oxide prepared in step (3) are the catalyst for the oxidation of ethylbenzene to acetophenone, and the other steps and parameters are the same as those in Example 1.

[0068] This comparative example also provides the application of the above catalyst for the preparation of acetophenone from ethylbenzene oxidation in the selective oxidation of ethylbenzene to acetophenone assisted by carbon dioxide, and the steps and parameters are the same as those in Example 1.

[0069] After the catalyst for the preparation of acetophenone from ethylbenzene oxidation was separated, gas chromatography (GC-2018) was used to analyze and identify various components in the product solution to determine the conversion rate, selectivity and product purity of the reaction. The analysis shows that in this Comparative Example 1, the conversion rate of ethylbenzene is 98%, the selectivity of acetophenone is 89.7%, and the purity of acetophenone is 99%.

[0070] Comparative Example 2

[0071] A preparation method of a catalyst for the preparation of acetophenone from ethylbenzene oxidation, compared with the preparation method of the catalyst for the preparation of acetophenone from ethylbenzene oxidation in Example 1, is different in that cobalt nitrate hexahydrate is not added in step (4), and the remaining steps and parameters are the same as those in Example 1.

[0072] This comparative example also provides the application of the above catalyst for the preparation of acetophenone from ethylbenzene oxidation in the selective oxidation of ethylbenzene to acetophenone assisted by carbon dioxide, and the steps and parameters are the same as those in Example 1.

[0073] After the catalyst for the preparation of acetophenone from ethylbenzene oxidation was separated, gas chromatography (GC-2018) was used to analyze and identify various components in the product solution to determine the conversion rate, selectivity and product purity of the reaction. The analysis shows that in this Comparative Example 2, the conversion rate of ethylbenzene is 93.1%, the selectivity of acetophenone is 99.3%, and the purity of acetophenone is 99.3%.

[0074] Comparative Example 3

[0075] A catalyst for the preparation of acetophenone from ethylbenzene oxidation is the same as the catalyst for the preparation of acetophenone from ethylbenzene oxidation obtained in Example 1.

[0076] This comparative example also provides the application of the above catalyst for the preparation of acetophenone from ethylbenzene oxidation in the selective oxidation of ethylbenzene to acetophenone assisted by carbon dioxide. Compared with the application in Example 1, the difference is that carbon dioxide is not introduced during the reaction process.

[0077] In this comparative example, carbon dioxide is not introduced. The analysis found that under the same reaction pressure and temperature conditions, to achieve the same conversion rate of ethylbenzene as in Example 1, the reaction time will be extended to 20 h.

[0078] The present invention has been described according to the above embodiments. It should be understood that the above embodiments do not limit the present invention in any form. Any technical solutions obtained by using equivalent replacements or equivalent transformations fall within the scope of the present invention.

Claims

1. A method for preparing a catalyst for oxidizing ethylbenzene to produce acetophenone, characterized in that: The following steps are involved: (1) mixing ammonia water, m-aminophenol and formaldehyde solution and performing a hydrothermal reaction to obtain a polymer precursor; (2) washing and drying the polymer precursor, and then carbonizing it to obtain nitrogen-doped carbon spheres; (3) adding cobalt salt and nitrogen-doped carbon spheres to a solvent in sequence, stirring, washing and drying, and then carbonizing to obtain carbon spheres loaded with cobalt oxide; (4) 2-Methylimidazole and cobalt salt are separately dissolved in a solvent and then mixed evenly, and carbon spheres loaded with cobalt oxide are added thereto for aging treatment to obtain a catalyst for oxidizing ethylbenzene to produce acetophenone.

2. The method for preparing a catalyst for oxidizing ethylbenzene to produce acetophenone according to claim 1, wherein: The step (1) comprises the following steps: dissolving ammonia water in ethanol aqueous solution, adding m-aminophenol, refluxing and stirring in an oil bath at 25 to 35° C. for 25 to 35 minutes, adding formaldehyde solution, refluxing and stirring in an oil bath at 25 to 35° C. for 3 to 5 hours, and heating to 80 to 150° C. at a heating rate of 3 to 5° C. / min for hydrothermal reaction for 22 to 26 hours to obtain a polymer precursor.

3. The method for preparing a catalyst for oxidizing ethylbenzene to prepare acetophenone as claimed in claim 2, characterized in that: The solid-liquid ratio of the ammonia water, m-aminophenol and formaldehyde solution is (0.1-0.3) mL: (0.7-0.9) g: (0.4-0.6) mL; the volume concentration of the ethanol aqueous solution is 20-30%; and the molar concentration of the formaldehyde solution is 10-15M.

4. The method for preparing a catalyst for oxidizing ethylbenzene to prepare acetophenone according to claim 1, wherein: The washing in step (2) and step (3) is performed with deionized water and ethanol in sequence; the drying temperature is 50-70°C and the drying time is 8-12 hours; the carbonization treatment conditions are: in an inert atmosphere, heating to 350-450°C at a rate of 1-3°C / min and maintaining for 2-4 hours, then heating to 450-550°C at a rate of 1-2°C / min and maintaining for 1.5-2.5 hours.

5. The method for preparing a catalyst for oxidizing ethylbenzene to produce acetophenone according to claim 1, wherein: The cobalt salt in step (3) and step (4) is cobalt nitrate hexahydrate; the solvent in step (3) is a mixed solution of ammonia water and water in a volume ratio of 1:(3-5); the stirring in step (3) is carried out under oil bath conditions at a temperature of 75-85° C. for 7-9 hours; the mass ratio of cobalt salt to nitrogen-doped carbon spheres in step (3) is 0.6-1:0.

5.

6. The method for preparing a catalyst for oxidizing ethylbenzene to prepare acetophenone according to claim 1, wherein: The solvent in step (4) is methanol; the aging treatment temperature is 20-35° C. and the time is 22-26 h; the mass ratio of 2-methylimidazole, cobalt salt and carbon spheres loaded with cobalt oxide is 5-8:2-3:

1.

7. A catalyst for preparing acetophenone by oxidizing ethylbenzene, prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the catalyst for oxidizing ethylbenzene to prepare acetophenone according to claim 7 in preparing acetophenone by selective oxidation of ethylbenzene assisted by carbon dioxide.

9. The use according to claim 8, characterized in that The following steps are involved: The catalyst for oxidizing ethylbenzene to prepare acetophenone and ethylbenzene are added into a high-pressure reactor, and the target product acetophenone is prepared by reaction under the action of an oxidant and carbon dioxide.

10. The use according to claim 9, characterized in that The reaction pressure is 2-4 MPa, the temperature is 75-85° C., and the reaction time is 9-11 h; the oxidant is tert-butyl hydroperoxide, hydrogen peroxide or oxygen; and the solid-liquid ratio of ethylbenzene to the catalyst for oxidizing ethylbenzene to prepare acetophenone is (20-30) mL:1 g.

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