Cobalt-based catalysts, methods of making and using, methods of catalyzing selective oxidation reactions of cyclohexane, methods of detecting liquid phase products

Abstract

The application provides a cobalt-based catalyst and a preparation method and application, a method for catalyzing selective oxidation reaction of cyclohexane, and a detection method for liquid-phase products, and relates to the technical field of nanometer new material catalysis. The preparation method of the cobalt-based catalyst provided by the application comprises the following steps: mixing a carrier and a diluent to obtain carrier slurry; coating the carrier slurry on the surface of a support sheet, drying, and then placing in an atomic layer deposition reaction cavity; alternately pulsing a cobalt precursor and an oxidizing agent into the atomic layer deposition reaction cavity, performing an oxidation reaction, and obtaining a cobalt-based catalyst. The application adopts atomic layer deposition technology to precisely control the CoO x particle size and distribution at an atomic scale, realizes precise positioning of CoO x particles, and greatly improves the catalytic performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nanometer new material catalysis technology, and particularly relates to a cobalt-based catalyst, a preparation method and application, a method for catalyzing selective oxidation of cyclohexane, and a method for detecting liquid-phase products. BACKGROUND

[0002] Cyclohexanol and cyclohexanone (commonly known as KA oil) are important products of selective oxidation of cyclohexane, and the KA oil is a raw material for producing nylon-66 and a large number of pharmaceutical intermediates, and is widely used. Therefore, the preparation of KA oil by selective oxidation of cyclohexane is a very important reaction in industry.

[0003] At present, the cyclohexane oxidation reaction has problems such as low conversion rate and poor selectivity of KA oil. From the perspective of thermodynamics and kinetics, the carbon-hydrogen bond energy barrier of cyclohexane is high, and it is not easy to occur oxidative reaction with oxygen insertion, resulting in low conversion rate. Moreover, the carbon-oxygen bond activation energy of the products cyclohexanone and cyclohexanol is low, and it is easy to occur over-oxidation to produce by-products such as acids and esters, resulting in poor selectivity. In order to solve the above problems, many researchers use the method of adding additional hydrogen peroxide, acetonitrile and other oxidants to chemically induce the cleavage of the C-H bond of cyclohexane, thereby improving the conversion rate. However, due to the high cost of the oxidant, it is difficult to realize industrialization. Therefore, it is necessary to use advanced methods to reasonably design and prepare catalysts to improve the catalytic performance of selective oxidation of cyclohexane.

[0004] The cobalt-based catalyst has always been a commonly used selective oxidation catalyst for cyclohexane. Due to the special 3d orbital state of Co, the activation ability of Co for the carbon-hydrogen bond of cycloalkane is strong, so that the cobalt-based catalyst can effectively activate the carbon-hydrogen bond of cyclohexane. In addition, Co can interact with the metal oxide carrier to produce more oxygen vacancies on the surface of the carrier, which can accelerate the adsorption and dissociation of oxygen molecules, so that oxygen can more efficiently participate in the reaction. At the same time, the cobalt-based catalyst can accelerate the conversion of intermediate products, thereby improving the catalytic performance of selective oxidation of cyclohexane.

[0005] The preparation methods of the commonly used supported catalysts include impregnation method, sol-gel method, ion exchange method, etc., which are difficult to achieve atomic-level precise control of the structure of the catalyst. SUMMARY

[0006] The purpose of the present application is to provide a cobalt-based catalyst, a preparation method and application, a method for catalyzing selective oxidation of cyclohexane, and a method for detecting liquid-phase products. The present application uses atomic layer deposition technology to precisely control the CoO x particle size and its distribution, and realizes the precise positioning of CoO x particles, thereby greatly improving the catalytic performance.

[0007] To achieve the above object, the present application provides the following technical solutions.

[0008] The present application provides a preparation method of a cobalt-based catalyst, comprising the following steps:

[0009] The carrier and the diluent are mixed to obtain a carrier slurry; the carrier slurry is coated on the surface of a support sheet, and after drying, it is placed in an atomic layer deposition reaction cavity;

[0010] A cobalt precursor and an oxidizing agent are alternately pulsed into the atomic layer deposition reaction cavity to perform an oxidation reaction, thereby obtaining a cobalt-based catalyst.

[0011] Preferably, the carrier comprises one or more of an alpha-Fe2O3 carrier, a SiO2 carrier and an Al2O3 carrier.

[0012] Preferably, the cobalt precursor comprises dicobalt.

[0013] Preferably, the oxidizing agent comprises oxygen or ozone.

[0014] Preferably, the number of times of the alternate pulsing is 1-30.

[0015] The present application provides a cobalt-based catalyst prepared by the preparation method described in the above technical solution, comprising a carrier and CoO x x in the CoO x is 1-1.5.

[0016] The present application provides an application of the cobalt-based catalyst described in the above technical solution in a selective oxidation reaction of cyclohexane.

[0017] The present application provides a method for catalyzing a selective oxidation reaction of cyclohexane, comprising the following steps:

[0018] The cobalt-based catalyst described in the above technical solution and cyclohexane are mixed, and a selective oxidation reaction is performed in an oxygen atmosphere to obtain a liquid phase product; the liquid phase product comprises cyclohexanol and / or cyclohexanone.

[0019] Preferably, the mass ratio of the cobalt-based catalyst to cyclohexane is 1:500-1000.

[0020] The present application provides a detection method of a liquid phase product obtained by the method described in the above technical solution, and the detection method of cyclohexanol and / or cyclohexanone in the liquid phase product comprises the following steps: taking chlorobenzene as an internal standard, performing gas chromatography detection on the liquid phase product to obtain the content of cyclohexanol and / or cyclohexanone in the liquid phase product.

[0021] The detection method of the ester species and / or the acid species in the liquid phase product comprises the following steps: dissolving the liquid phase product in a solvent, adding a chromogenic agent, titrating the acid species in the liquid phase product with a sodium hydroxide solution to obtain the content of the acid species in the liquid phase product; adding an excess of sodium hydroxide solution, performing condensation reflux, then re-titrating the mixed solution after cooling with a hydrochloric acid solution, and obtaining the content of the ester species in the liquid phase product according to the difference between the molar amount of the excess sodium hydroxide and the molar amount of the hydrochloric acid used for re-titration.

[0022] The detection method of cyclohexyl hydrogen peroxide in the liquid phase product comprises the following steps: taking chlorobenzene as an internal standard, performing gas chromatography detection on the liquid phase product to obtain the content of cyclohexanol in the liquid phase product; adding triphenyl phosphine to the liquid phase product to perform a reduction reaction, and detecting the content of cyclohexanol in the reduction system using gas chromatography; and obtaining the content of cyclohexyl hydrogen peroxide in the liquid phase product according to the difference between the content of cyclohexanol in the reduction system and the content of cyclohexanol in the liquid phase product.

[0023] The application provides a preparation method of a cobalt-based catalyst. x The cobalt-based catalyst prepared by the method can achieve excellent cyclohexane oxidation conversion rate and selectivity under the condition of low load of non-noble metal. x The preparation method is simple, and the particle size and distribution of CoO BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a high-resolution TEM image of the surface of the 10Co / Fe2O3 catalyst prepared in Example 2 and the alpha-Fe2O3 carrier;

[0025] Figure 2 It is a high-resolution TEM image of the surface of the 10Co / Fe2O3 catalyst prepared in Example 2;

[0026] Figure 3 It is a preparation schematic diagram of the cobalt-based catalyst. DETAILED DESCRIPTION

[0027] The application provides a preparation method of a cobalt-based catalyst.

[0028] The carrier and the diluent are mixed to obtain carrier slurry; the carrier slurry is coated on the surface of a support sheet, and after drying, is placed in an atomic layer deposition reaction cavity;

[0029] Alternately pulse cobalt precursor and oxidizing agent into the atomic layer deposition reaction cavity, and perform oxidation reaction to obtain cobalt-based catalyst.

[0030] The carrier and diluent are mixed to obtain carrier slurry; the carrier slurry is coated on the surface of the support sheet, and after drying, is placed in the atomic layer deposition reaction cavity. In the present application, the carrier preferably includes one or more of alpha-Fe2O3 carrier, SiO2 carrier and Al2O3 carrier. In the present application, the average particle size of the carrier is preferably 1-100 nm, more preferably 1-50 nm. In the present application, the alpha-Fe2O3 carrier is preferably nanorod-shaped.

[0031] In the present application, when the carrier is alpha-Fe2O3 carrier, the preparation method of the alpha-Fe2O3 carrier preferably includes: mixing ferric chloride, water and propylene diamine, and performing hydrothermal reaction to obtain hydrothermal product; calcining the hydrothermal product to obtain alpha-Fe2O3 carrier.

[0032] In the present application, the ferric chloride is preferably ferric chloride hexahydrate. In the present application, the water is preferably deionized water. In the present application, the ratio of the amount of ferric chloride, water and propylene diamine is preferably 1-2 g: 5-10 mL: 5-10 mL, more preferably 1.6 g: 7 mL: 7 mL. In the present application, the mixing of the ferric chloride, water and propylene diamine preferably includes: dissolving the ferric chloride in water, and then adding propylene diamine. In the present application, the mixing is preferably performed at room temperature. In the present application, the temperature of the hydrothermal reaction is preferably 160-180℃; the time of the hydrothermal reaction is preferably 14-16 h. The present application preferably further includes, after the hydrothermal reaction: performing solid-liquid separation on the obtained system to obtain precipitate; and sequentially performing washing and drying on the precipitate to obtain hydrothermal product. In the present application, the washing preferably includes sequentially performed first water washing, alcohol washing and second water washing. In the present application, the first water washing preferably includes first ultrasonic cleaning with deionized water, and then centrifugal separation. In the present application, the alcohol washing preferably includes first ultrasonic cleaning with ethanol, and then centrifugal separation. In the present application, the alcohol washing is preferably performed 3 times. In the present application, the second water washing preferably includes centrifugal washing with deionized water. In the present application, the time of ultrasonic cleaning during the first water washing and alcohol washing is preferably 10-50 s. In the present application, during the first water washing, alcohol washing and second water washing, the rotation speed of the centrifuge is preferably 8000-10000 rpm, and the rotation time is preferably 3-5 min. In the present application, the temperature of the drying is preferably 80-100℃; the time of the drying is preferably 10-18 h, more preferably 12-15 h.

[0033] After obtaining the hydrothermal product, the hydrothermal product is preferably calcined to obtain the α-Fe2O3 carrier. In the present application, the temperature of the calcination is preferably 400-600°C, more preferably 450-500°C; the holding time is preferably 60-120 min, more preferably 100-180 min. In the present application, the heating rate from room temperature to the temperature of the calcination is preferably 5-10°C / min, more preferably 5-8°C / min. In the present application, the carrier surface is made to have defect oxygen vacancies by calcination to obtain the α-Fe2O3 carrier.

[0034] In the present application, the carrier and the diluent are mixed to obtain the carrier slurry. In the present application, the diluent preferably comprises one or more of ethanol, methanol, acetone, water and chloroform. In the present application, the mass content of the carrier in the carrier slurry is preferably 1-5 g / L, more preferably 2-4 g / L.

[0035] In the present application, the support sheet is preferably a silicon sheet. In the present application, the silicon sheet is used to make the vapor deposition more uniform due to its strong thermal conductivity.

[0036] In the present application, the carrier slurry is coated on the surface of the support sheet, and after drying, is placed in the atomic layer deposition reaction cavity. In the present application, the coating thickness of the carrier slurry is preferably 0.1-1 mm, more preferably 0.5-0.8 mm. In the present application, the drying temperature is preferably room temperature.

[0037] In the present application, the cobalt precursor and the oxidizing agent are alternately pulsed into the atomic layer deposition reaction cavity to perform oxidation reaction to obtain the cobalt-based catalyst. In the present application, the heating temperature of the cobalt precursor is preferably 60-110°C, more preferably 90°C. In the present application, the cobalt precursor preferably comprises bis(cyclopentadienyl)cobalt. In the present application, the cobalt precursor is preferably first heated to the sublimation temperature of the cobalt precursor and then pulsed into the atomic layer deposition reaction cavity. In the present application, the flow rate of the cobalt precursor is preferably 30-60 seem, more preferably 40-50 seem.

[0038] In the present application, the oxidizing agent preferably comprises oxygen or ozone, more preferably ozone. In a specific embodiment of the present application, ozone is obtained by converting high-purity oxygen (more than 99.99%) into ozone through an ozone generator and then introducing it into the atomic layer deposition reaction cavity for reaction. In the present application, the flow rate of the ozone is preferably 10-50 seem, more preferably 15-20 seem.

[0039] In this invention, the preferred conditions for each pulse of the cobalt precursor include: pulse time of 5-50 s, breath-holding time of 7-70 s, and purging time of 10-80 s; more preferably, pulse time of 30-40 s, breath-holding time of 30-40 s, and purging time of 60-70 s.

[0040] In this invention, the preferred conditions for each pulse of oxidant include: pulse time of 5-50s, breath-holding time of 10-75s, and purging time of 10-80s; more preferably, 20-75s: pulse time of 2-8s, breath-holding time of 6-8s, and purging time of 6-8s.

[0041] In this invention, an alternating pulse consists of sequentially pulsed cobalt precursor and pulsed oxidant once. The number of alternating pulses is preferably 1 to 30, more preferably 5 to 20. In a specific embodiment of this invention, such as... Figure 3 As shown, cobalt diacene is first pulsed into the atomic layer deposition reaction chamber to anchor the cobalt diacene onto the carrier surface. Then, an oxidant is pulsed to react with the cobalt diacene, generating CoO on the carrier surface. x .

[0042] In this invention, the temperature of the oxidation reaction is preferably 150-250°C, more preferably 180-200°C.

[0043] This invention provides a cobalt-based catalyst prepared by the method described above, comprising a support and CoO2 grown in situ on the surface of the support. x The CoO x x in the figure is 1 to 1.5. In this invention, the CoO x The particle size is preferably 1–4 nm. In this invention, the mass percentage of Co in the cobalt-based catalyst is preferably 0.01–3%, more preferably 0.05–1.5%.

[0044] This invention provides the application of the cobalt-based catalyst described above in the selective oxidation of cyclohexane. In this invention, the application is preferably carried out under solvent-free conditions.

[0045] This invention provides a method for the selective oxidation of cyclohexane catalyzed by the following steps:

[0046] The cobalt-based catalyst described in the above technical solution is mixed with cyclohexane and subjected to a selective oxidation reaction in an oxygen atmosphere to obtain a liquid product; the liquid product includes cyclohexanol and / or cyclohexanone.

[0047] In this invention, no solvent is added during the selective oxidation of cyclohexane catalytically.

[0048] In the present application, the mass ratio of the cobalt-based catalyst to cyclohexane is preferably 1:500-1000, and more preferably 1:750-800. In the present application, the gas for providing the oxygen atmosphere is preferably pure oxygen.

[0049] In the present application, the temperature of the selective oxidation reaction is preferably 100-180°C, and more preferably 145-160°C; the time of the selective oxidation reaction is preferably 0.5-15h, and more preferably 1-3h; and the pressure of the selective oxidation reaction is preferably 0.5-3MPa, and more preferably 1-2MPa. In the present application, the selective oxidation reaction is preferably carried out under stirring; and the stirring rate is preferably 800-1500rpm, and more preferably 900-1000rpm.

[0050] After the selective oxidation reaction, the reaction system obtained in the present application is preferably subjected to centrifugation, and the supernatant obtained is the liquid-phase product. In the present application, the cobalt-based catalyst is removed by centrifugation.

[0051] The present application can achieve excellent conversion rate and selectivity of cyclohexane oxidation using a low-loading non-noble metal, and can be used for efficiently preparing cyclohexanol and cyclohexanone by selective catalytic oxidation of cyclohexane under solvent-free conditions.

[0052] The present application also provides a detection method for the liquid-phase product obtained by the method described in the above technical solution. The detection method for each substance in the liquid-phase product is described below. The detection method of the present application can comprehensively determine and analyze the liquid-phase product of the selective oxidation reaction of cyclohexane, and solve the problem of inaccurate product analysis.

[0053] In the present application, the detection method for cyclohexanol and / or cyclohexanone in the liquid-phase product comprises the following steps: taking chlorobenzene as an internal standard, and detecting the liquid-phase product by gas chromatography to obtain the content of cyclohexanol and / or cyclohexanone in the liquid-phase product. The present application does not have special requirements for the conditions of the gas chromatography detection, and the gas chromatography detection method known to those skilled in the art can be used.

[0054] In the present application, the detection method for ester species and / or acid species in the liquid-phase product comprises the following steps: dissolving the liquid-phase product in a solvent, adding a chromogenic agent, titrating the acid species in the liquid-phase product with a sodium hydroxide solution to obtain the content of the acid species in the liquid-phase product; adding an excess of sodium hydroxide solution, performing condensation reflux, and then titrating the mixed solution after cooling with a hydrochloric acid solution to obtain the content of the ester species in the liquid-phase product according to the difference between the molar amount of the excess sodium hydroxide and the molar amount of the hydrochloric acid used for the back titration.

[0055] The liquid phase product is dissolved in a solvent, a color developing agent is added, and the acid species in the liquid phase product is titrated using a sodium hydroxide solution to obtain the content of the acid species in the liquid phase product. In the present application, the solvent preferably comprises one or more of ethanol, acetone and n-butanol, and more preferably is ethanol. In the present application, the ratio of the amount of the liquid phase product to the amount of the solvent is preferably 1 g: 10-50 mL, and more preferably is 1 g: 10-20 mL. In the present application, the color developing agent is preferably a phenolphthalein solution; the concentration of the phenolphthalein solution is preferably 0.1-0.5 mol / L; and the amount of the phenolphthalein solution added when titrating the acid species in the liquid phase product is preferably 1-20 drops, and more preferably is 5-10 drops. In the present application, the concentration of the sodium hydroxide solution used when titrating the acid species in the liquid phase product is preferably 0.05-0.2 mol / L, and more preferably is 0.1 mol / L. In the present application, the end point of the titration of the sodium hydroxide solution is when the solution changes from colorless to red.

[0056] In the present application, the calculation formula of the content of the acid species in the liquid phase product is shown in Formula I:

[0057]

[0058] In Formula I, n 酸 is the molar amount of the acid species in the liquid phase product, and the unit is mol; C NaOH is the concentration of the sodium hydroxide solution, and the unit is mol / L; V NaOH is the volume of the sodium hydroxide solution titration, and the unit is L; m 滴定液相产物质量 is the mass of the liquid phase product used in the titration, and the unit is g; m 液相产物总质量 is the total mass of the liquid phase product obtained from the selective oxidation reaction of cyclohexane, and the unit is g.

[0059] In the present application, an excess amount of sodium hydroxide solution is added, and after condensation reflux, the mixed solution after cooling is back-titrated using a hydrochloric acid solution, and the content of the ester species in the liquid phase product is obtained according to the difference between the molar amount of the excess sodium hydroxide and the molar amount of the hydrochloric acid used in the back-titration. In the present application, the volume of the excess sodium hydroxide solution is preferably 5-20 mL, and more preferably is 10-20 mL. In the present application, the concentration of the excess sodium hydroxide solution is preferably 0.05-0.2 mol / L, and more preferably is 0.1 mol / L. In the present application, the temperature of the condensation reflux is preferably 70-150°C, and more preferably is 110°C; and the time of the condensation reflux is preferably 1-3 h. In the present application, the concentration of the hydrochloric acid solution is preferably 0.05-0.2 mol / L, and more preferably is 0.1 mol / L. In the present application, the end point of the back-titration of the hydrochloric acid solution is when the solution changes from red to colorless.

[0060] In the present application, the calculation formula of the content of the ester species in the liquid phase product is shown in Formula II:

[0061]

[0062] In formula II, n 酯 is the molar amount of the ester species in the liquid phase product, unit: mol; C NaOH is the concentration of the excess sodium hydroxide solution, unit: mol / L; V 过量NaOH is the volume of the excess sodium hydroxide solution, unit: L; C HCl is the concentration of the hydrochloric acid solution, unit: mol / L; V HCl is the volume of the hydrochloric acid solution titration, unit: L; m 滴定液相产物质量 is the mass of the liquid phase product used in titration, unit: g; m 液相产物总质量 is the total mass of the liquid phase product obtained by the selective oxidation reaction of cyclohexane, unit: g.

[0063] In the specific embodiments of the present application, the standard solution is calibrated as follows: 17 mol / L concentrated hydrochloric acid is added to 50 mL of deionized water to prepare a 0.1 mol / L hydrochloric acid solution; 4 g of sodium hydroxide particles is weighed and added to deionized water to prepare a 0.1 mol / L sodium hydroxide solution.

[0064] 0.1 g of anhydrous sodium carbonate is placed in a muffle furnace and calcined at 300-400℃ for 7 h to remove water, and 1 g is taken and added to 50 mL of deionized water in a 250 mL conical flask to prepare a sodium carbonate solution; bromocresol green-methyl red titration indicator (color change pH range 5-8) is added to the sodium carbonate solution, and the above-mentioned 0.1 mol / L hydrochloric acid solution is used to titrate the sodium carbonate solution, when the solution changes from green to dark red, it is the end point of titration, and the volume V1 of hydrochloric acid solution consumed when the solution changes color is recorded; at the same time, bromocresol green-methyl red indicator is added to a pure water solution, and the above-mentioned 0.1 mol / L hydrochloric acid solution is added dropwise, and the volume V0 of hydrochloric acid solution consumed when the solution changes color is recorded, and the accurate concentration of the hydrochloric acid solution is calculated using formula IV.

[0065]

[0066] In formula IV, C HCl is the concentration of the hydrochloric acid solution, unit: mol / L; m is the mass of anhydrous sodium carbonate after water removal, unit: g.

[0067] Take 0.1g hydrogen potassium phthalate into the oven 100-150℃ drying overnight, in the conical flask 50mL deionized water into hydrogen potassium phthalate solution, add 2 drops of phenolphthalein indicator (color change pH range is 8.2-10.0), using the above prepared 0.1mol / L sodium hydroxide solution to the known concentration of hydrogen potassium phthalate solution titration, when the phenolphthalein reagent turns red is the end point of titration, record the solution when the volume of sodium hydroxide solution consumed V1;At the same time in pure water solution is added phenolphthalein reagent, drop the above 0.1mol / L sodium hydroxide solution, record the solution when the volume of sodium hydroxide solution consumed V0, using formula V to obtain the accurate concentration of sodium hydroxide solution.

[0068]

[0069] In formula V, C NaOH The concentration of sodium hydroxide solution, unit mol / L;M is the mass of dried hydrogen potassium phthalate, unit g.

[0070] In the application, the detection method of cyclohexyl hydroperoxide in the liquid phase product comprises the following steps: taking chlorobenzene as an internal standard, the liquid phase product is detected by gas chromatography to obtain the content of cyclohexanol in the liquid phase product; triphenyl phosphorus is added to the liquid phase product to carry out a reduction reaction, and the content of cyclohexanol in the reduction system is detected by gas chromatography; the content of cyclohexyl hydroperoxide in the liquid phase product is obtained according to the difference between the content of cyclohexanol in the reduction system and the content of cyclohexanol in the liquid phase product.

[0071] In the application, the detection method of cyclohexyl hydroperoxide in the liquid phase product comprises the following steps: taking chlorobenzene as an internal standard, the liquid phase product is detected by gas chromatography to obtain the content of cyclohexanol in the liquid phase product; triphenyl phosphorus is added to the liquid phase product to carry out a reduction reaction, and the content of cyclohexanol in the reduction system is detected by gas chromatography; the content of cyclohexyl hydroperoxide in the liquid phase product is obtained according to the difference between the content of cyclohexanol in the reduction system and the content of cyclohexanol in the liquid phase product.

[0072] After obtaining the content of cyclohexanol in the liquid phase product, triphenyl phosphorus is added to the liquid phase product to carry out a reduction reaction, and the content of cyclohexanol in the reduction system is detected by gas chromatography; the content of cyclohexyl hydroperoxide in the liquid phase product is obtained according to the difference between the content of cyclohexanol in the reduction system and the content of cyclohexanol in the liquid phase product. In the application, the mass ratio of triphenyl phosphorus to cyclohexane is preferably 0.1-1:150, and more preferably 1:150, so as to ensure that all cyclohexyl radicals in the liquid phase product are converted into cyclohexanol.

[0073] In the application, triphenyl phosphorus can reduce cyclohexyl hydroperoxide in the liquid phase product into cyclohexanol.

[0074] In the application, the calculation formula of the content of cyclohexyl hydroperoxide in the liquid phase product is shown in formula III:

[0075]

[0076] In formula III, n 环己基过氧化氢 is the molar amount of the intermediate product cyclohexylhydrogen peroxide in the liquid phase product, in mol; n 加入三苯基磷后环己醇的摩尔量 is the molar amount of cyclohexanol measured after the addition of triphenylphosphine, in mol; n 加入三苯基磷前环己醇的摩尔量 is the molar amount of cyclohexanol measured before the addition of triphenylphosphine, in mol; m 取用液相产物的质量 is the mass taken from the liquid phase product for detection, in g; m 液相产物总质量 is the total mass of the liquid phase product of the selective oxidation reaction of cyclohexane, in g.

[0077] The technical solutions in the present application will be described clearly and completely below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0078] Example 1

[0079] Preparation of iron oxide nanorod carrier:

[0080] 1.6 g of iron trichloride hexahydrate powder was weighed, added with 7 mL of deionized water, and stirred for 10 min to be dissolved into a yellow clear solution;

[0081] 7 mL of propylene diamine was added to the above yellow clear solution at normal temperature, and immediately after the addition, a precipitate was generated, and continuous stirring resulted in a dark red mixture;

[0082] The above dark red mixture was transferred into a polytetrafluoroethylene-lined hydrothermal kettle, and placed in an oven for hydrothermal reaction at 180℃ for 16 h;

[0083] After the reaction was completed, natural cooling was performed, and the clear supernatant propylene diamine aqueous solution was completely separated from the catalyst powder of iron trioxide nanoparticles, and then the clear supernatant was transferred to obtain a precipitate;

[0084] The above precipitate was placed into a centrifuge tube, 20 mL of deionized water was added, and ultrasonic treatment was performed for 10 s to remove the ligand ions on the surface of the material, and then centrifugal separation was performed at a speed of 10000 rpm;

[0085] After the centrifugal washing with deionized water, 20 mL of ethanol was added, and ultrasonic treatment was performed for 10 s to fully mix the precipitate with the ethanol, and then the centrifuge tube was placed into a centrifuge, and centrifugal separation was performed at a speed of 10000 rpm, and then the clear supernatant was transferred, and the above steps were repeated three times;

[0086] After the above steps are completed, 20 mL of deionized water is added, the pH of the supernatant after centrifugation is tested using pH test paper, and after the pH reaches neutral, the centrifuge tube is placed in an oven at 80°C and dried for 12 h;

[0087] The dried hydrothermal product is taken out and placed in a crucible, calcined at 500°C for 3 h, and naturally cooled to room temperature to obtain an α-Fe2O3 carrier.

[0088] Preparation of a cobalt-based catalyst:

[0089] 20 mg of the α-Fe2O3 carrier is weighed and ultrasonically dispersed using ethanol to obtain a carrier slurry with a concentration of 1 g / L; the carrier slurry is applied to the surface of a silicon wafer (8 cm x 8 cm in size) with a coating thickness of 0.5 mm, and dried at room temperature (25°C);

[0090] The above sample is placed in an atomic layer deposition (ALD) reaction chamber, high-purity nitrogen gas (99.999%) generated by a nitrogen generator is used as the carrier gas, the carrier gas flow rate is set to 50 sccm / min, the heating temperature of the cobaltocene is set to 90°C, the cobaltocene pulse time is 50 s, the gas retention time is 60 s, and the purge time is 70 s; after the cobaltocene precursor pulse enters the reaction chamber and reacts, ozone is pulsed again to oxidize the cobaltocene to CoO x , the oxidation temperature is 190°C, the ozone is generated by a high-purity oxygen generator (99.99%), the flow rate is 15 sccm, the ozone pulse time is 20 s, the gas retention time is 60 s, and the purge time is 75 s; a 1Co / Fe2O3 cobalt-based monatomic catalyst is prepared (wherein "1" represents the number of alternating pulses), and the Co content of the catalyst is 0.081wt% as characterized by ICP-MS.

[0091] The 1Co / Fe2O3 catalyst prepared above is subjected to performance testing for selective oxidation of cyclohexane. 20 mg of the above 1Co / Fe2O3 catalyst is accurately weighed, 15 g of cyclohexane is added, and placed in a high-pressure reaction kettle; the high-pressure reaction kettle is leak-tested using a soap bubble, and the sealed high-pressure reaction kettle is purged three times with pure oxygen (99.99%); the gas pressure in the high-pressure reaction kettle is maintained at 1 MPa, the high-pressure reaction kettle is heated to 145°C and the stirring speed is maintained at 1000 rpm, the reaction is carried out for 90 min, and the liquid phase product is obtained; chlorobenzene is used as an internal standard, and gas chromatography is used to quantitatively analyze the liquid phase product.

[0092] The test results show that the conversion rate of cyclohexane is 11.356% and the selectivity of the products cyclohexanol and cyclohexanone (KA oil) is 46.46% when the 1Co / Fe2O3 catalyst is used for selective oxidation of cyclohexane under solvent-free conditions. This indicates that the cobalt-based catalyst prepared by the method provided by the present application has good catalytic performance.

[0093] Example 2

[0094] 20 mg of the a-Fe2O3 carrier described in Example 1 was weighed and ultrasonically dispersed using ethanol to obtain a carrier slurry with a concentration of 1 g / L; the carrier slurry was applied to the surface of a silicon wafer (8 cm x 8 cm in size) with a coating thickness of 0.5 mm, and dried at room temperature (25°C);

[0095] The sample was placed in an ALD reaction chamber, and high-purity nitrogen (99.999%) generated by a nitrogen generator was used as the carrier gas; the carrier gas flow rate was set to 50 sccm / min, the heating temperature of the cobaltocene was set to 90°C, the cobaltocene pulse time was 50 s, the holding time was 60 s, and the purge time was 70 s; after the cobaltocene precursor pulse entered the reaction chamber and reacted, ozone was pulsed again to oxidize the cobaltocene to CoO x , the oxidation temperature was 190°C, the ozone was generated by a high-purity oxygen generator (99.99%), the flow rate was 15 sccm, the ozone pulse time was 25 s, the holding time was 75 s, and the purge time was 60 s; the above-mentioned pulse cobaltocene-pulse ozone process was repeated to prepare a 10Co / Fe2O3 cobalt-based sub-nanometal cluster catalyst (wherein “10” represents the number of alternating pulses), and the Co content of the catalyst was 1.47 wt% as characterized by ICP-MS.

[0096] The 10Co / Fe2O3 catalyst prepared above was subjected to performance testing for selective oxidation of cyclohexane. 20 mg of the 10Co / Fe2O3 catalyst was accurately weighed, 15 g of cyclohexane was added, and the high-pressure reaction kettle was placed in a high-pressure reaction kettle; the high-pressure reaction kettle was leak-tested using a soap bubble, and the sealed high-pressure reaction kettle was purged and cleaned three times using pure oxygen (99.99%); the gas pressure in the high-pressure reaction kettle was maintained at 1 MPa, the high-pressure reaction kettle was heated to 145°C and the stirring speed was maintained at 1000 rpm, the reaction was carried out for 90 min, and the liquid phase product was obtained; chlorobenzene was used as an internal standard, and gas chromatography was used to quantitatively analyze the liquid phase product.

[0097] The test results show that the conversion rate of cyclohexane is 10.433% and the selectivity of product KA oil is 77.392% when the 10Co / Fe2O3 catalyst is used for selective oxidation of cyclohexane under solvent-free conditions. This indicates that the cobalt-based catalyst prepared by the method provided by the present application has excellent catalytic performance.

[0098] Example 3

[0099] Take 20 mg of the α-Fe2O3 carrier described in Example 1, and use ethanol to ultrasonically disperse to obtain a carrier slurry with a concentration of 1 g / L; apply the carrier slurry to the surface of a silicon wafer (with a size of 8 cm x 8 cm), with a coating thickness of 0.5 mm, and dry at room temperature (25°C);

[0100] Put the above sample into an ALD reaction cavity, use high-purity nitrogen gas (99.999%) generated by a nitrogen generator as the carrier gas, set the carrier gas flow rate to 50 sccm / min, set the heating temperature of the cobaltocene to 90°C, set the cobaltocene pulse time to 50 s, the gas retention time to 60 s, and the purge time to 70 s; after the cobaltocene precursor pulse enters the reaction cavity and reacts, pulse ozone to oxidize the cobaltocene to CoO x , the oxidation temperature is 190°C, the ozone is generated by an ozone generator from high-purity oxygen (99.99%), the flow rate is 15 sccm, the pulse time is 25 s, the gas retention time is 75 s, and the purge time is 60 s; repeat the above process of pulsed cobaltocene-pulsed ozone to prepare 20Co / Fe2O3 ultrafine nanoparticle cobalt-based catalyst (wherein "20" represents the number of alternating pulses), and the Co content of the catalyst is 1.89 wt% as characterized by ICP-MS.

[0101] Test the cyclohexane selective oxidation reaction performance of the 20Co / Fe2O3 catalyst prepared above. Accurately take 20 mg of the 20Co / Fe2O3 catalyst above, add 15 g of cyclohexane, and put it into a high-pressure reaction kettle; use a soap bubble to check the high-pressure reaction kettle for leaks, and use pure oxygen (99.99%) to replace and clean the sealed high-pressure reaction kettle 3 times; keep the gas pressure of the high-pressure reaction kettle at 1 MPa, heat the high-pressure reaction kettle to 145°C, and keep the stirring speed at 1000 rpm, react for 90 min, and obtain a liquid phase product; use chlorobenzene as an internal standard, and use gas chromatography to quantitatively analyze the liquid phase product.

[0102] The test results show that the conversion rate of cyclohexane is 11.106% and the selectivity of product KA oil is 73.52% when the 20Co / Fe2O3 catalyst is used to perform cyclohexane selective oxidation reaction under solvent-free conditions. This shows that the cobalt-based catalyst prepared by the method provided by the present application has good catalytic performance.

[0103] Example 4

[0104] Take 20 mg of SiO2 carrier, use ethanol to ultrasonically disperse to obtain a carrier slurry with a concentration of 1 g / L; apply the carrier slurry to the surface of a silicon wafer (with a size of 8 cm x 8 cm), with a coating thickness of 0.8 mm, and dry at room temperature (25°C);

[0105] The sample is placed in an ALD reaction cavity, the carrier gas used is high-purity nitrogen (99.999%) generated by a nitrogen generator; the carrier gas flow is set to 50 sccm / min, the heating temperature of the cobaltocene is set to 90°C, the pulse time of the cobaltocene is 50s, the holding time is 60s, and the purge time is 70s; after the cobaltocene precursor pulse enters the reaction cavity and reacts, the ozone is pulsed again, and the cobaltocene is oxidized to CoO using ozone x , the oxidation temperature is 190°C, the ozone is generated by a high-purity oxygen (99.99%) generator, the flow is 15sccm, the pulse time is 25s, the holding time is 75s, and the purge time is 60s; the above-mentioned pulse cobaltocene-pulse ozone process is repeated to prepare 5Co / SiO2 ultra-fine nano-particle cobalt-based catalyst (wherein "5" represents the number of alternating pulses), and the Co content of the catalyst is 0.37wt% by ICP-MS characterization.

[0106] The 5Co / SiO2 catalyst prepared above is subjected to performance test of selective oxidation of cyclohexane. 20mg of the 5Co / SiO2 catalyst is accurately weighed, 15g of cyclohexane is added, and the high-pressure reaction kettle is placed in a high-pressure reaction kettle; the high-pressure reaction kettle is leak-tested using a soap bubble, and the sealed high-pressure reaction kettle is purged three times using pure oxygen (99.99%); the gas pressure of the high-pressure reaction kettle is kept at 1MPa, the high-pressure reaction kettle is heated to 145°C and kept at a stirring speed of 1000rpm, and the reaction is carried out for 90min to obtain a liquid phase product; chlorobenzene is used as an internal standard, and gas chromatography is used to quantitatively analyze the liquid phase product.

[0107] The test results show that the conversion rate of cyclohexane is 10.85% and the selectivity of KA oil is 71.12% when the 5Co / SiO2 catalyst is used for selective oxidation of cyclohexane under solvent-free conditions. It is shown that the cobalt-based catalyst prepared by the method provided by the present application has good catalytic performance.

[0108] Example 5

[0109] 20mg of Al2O3 carrier is weighed and dispersed using ethanol ultrasonic dispersion to obtain a carrier slurry with a concentration of 1g / L; the carrier slurry is coated on the surface of a silicon wafer (size 8cm x 8cm) with a coating thickness of 0.8mm, and dried at room temperature (25°C);

[0110] The sample is placed in an ALD reaction cavity, the carrier gas used is high-purity nitrogen (99.999%) generated by a nitrogen generator; the carrier gas flow is set to 50 sccm / min, the heating temperature of the cobaltocene is set to 90°C, the pulse time of the cobaltocene is 50s, the holding time is 60s, and the purge time is 70s; after the cobaltocene precursor pulse enters the reaction cavity and reacts, the ozone is pulsed again, and the cobaltocene is oxidized to CoO using ozonex The oxidation temperature is 190°C, the ozone is generated by a high-purity oxygen (99.99%) through an ozone generator, the flow rate is 15 sccm, the pulse time is 25 s, the hold time is 75 s, and the purge time is 60 s; the above-mentioned pulse cobaltocene-pulse ozone process is repeated to prepare a 5Co / Al2O3 ultrafine nanoparticle cobalt-based catalyst (wherein "5" represents the number of times of alternating pulses), and the Co content of the catalyst is 0.52wt% as indicated by ICP-MS characterization.

[0111] The 5Co / Al2O3 catalyst prepared above is subjected to performance test of selective oxidation of cyclohexane. 20 mg of the 5Co / Al2O3 catalyst is accurately weighed, 15 g of cyclohexane is added, and the mixture is put into a high-pressure reaction kettle; the high-pressure reaction kettle is subjected to leak detection by using a soap bubble, and the closed high-pressure reaction kettle is cleaned by replacement with pure oxygen (99.99%) for 3 times; the gas pressure of the high-pressure reaction kettle is kept at 1 MPa, the high-pressure reaction kettle is heated to 145°C and kept at a stirring speed of 1000 rpm, and the reaction is carried out for 90 min to obtain a liquid phase product; chlorobenzene is used as an internal standard, and the liquid phase product is subjected to quantitative analysis by using gas chromatography.

[0112] The test results show that the conversion rate of cyclohexane is 9.07% and the selectivity of product KA oil is 79.85% when the 5Co / Al2O3 catalyst is used for selective oxidation of cyclohexane under a solvent-free condition, indicating that the cobalt-based catalyst prepared by the method provided in the application has good catalytic performance.

[0113] Comparative Example 1

[0114] The α-Fe2O3 carrier prepared in Example 1 is used as Comparative Example 1, which is named as 0Co / Fe2O3.

[0115] The 0Co / Fe2O3 catalyst prepared above is subjected to performance test of selective oxidation of cyclohexane. 20 mg of the 0Co / Fe2O3 catalyst is accurately weighed, 15 g of cyclohexane is added, and the mixture is put into a high-pressure reaction kettle; the high-pressure reaction kettle is subjected to leak detection by using a soap bubble, and the closed high-pressure reaction kettle is cleaned by replacement with pure oxygen (99.99%) for 3 times; the gas pressure of the high-pressure reaction kettle is kept at 1 MPa, the high-pressure reaction kettle is heated to 145°C and kept at a stirring speed of 1000 rpm, and the reaction is carried out for 90 min to obtain a liquid phase product; chlorobenzene is used as an internal standard, and the liquid phase product is subjected to quantitative analysis by using gas chromatography.

[0116] The test results show that the conversion rate of cyclohexane is 1.8% and the selectivity of product KA oil is 21.8% when the 0Co / Fe2O3 catalyst is used for selective oxidation of cyclohexane under a solvent-free condition, indicating that the cobalt-based catalyst prepared by the method provided in the application has good catalytic performance.

[0117] Test Example

[0118] Figure 1 The high resolution TEM image of the ultrafine nanoparticle metal catalyst prepared using ALD for Example 2 and the α-Fe2O3 carrier shows that the average diameter of the carrier is 50 nm, and the ultrafine CoO x nanoparticles are successfully loaded on the surface of the carrier.

[0119] Figure 2 The high resolution TEM image of the ultrafine metal nanoparticles loaded on the surface of the iron oxide carrier for Example 2 shows that the lattice fringes of the carrier and the loaded metal can be clearly seen, and the particles loaded on the surface of the carrier are CoO x , the size of the ultrafine nanoparticles is 2 nm ± 1 nm, and the interplanar spacing is 0.24 nm, which belongs to the (200) crystal plane of CoO x .

[0120] The Co content test results of the catalysts prepared in Examples 1-3 and Comparative Example 1 and the performance comparison of the catalysts show that as the number of cycles of the catalyst increases, the Co content shows an overall upward trend. After CoO x is deposited on the surface of the α-Fe2O3 carrier, the conversion rate and selectivity of the catalyst are greatly improved.

[0121] Example 6

[0122] The product structure analysis of the liquid phase product of the selective oxidation reaction of cyclohexane in the examples using gas chromatography-mass spectrometry shows that the product contains cyclohexane, cyclohexanol, cyclohexanone and other products, and it is also observed that the product contains acids, ester substances and intermediate product cyclohexyl hydroperoxide.

[0123] A test method for testing acid species and ester species in a liquid phase product: 1 g of the liquid phase product is dissolved in 20 mL of ethanol, 10 drops of 0.1 mol / L phenolphthalein solution are added, 0.1 mol / L sodium hydroxide solution is added, and the solution is titrated to a slight pink color. The volume of sodium hydroxide solution consumed after titration is recorded, and the content of acid species in the liquid phase product is calculated according to Formula I; 20 mL of excess sodium hydroxide solution (concentration of 0.1 mol / L) is added, and the solution is condensed and refluxed in an oil bath at 110°C for 1 h. After cooling to room temperature, 0.1 mol / L hydrochloric acid solution is added to the round-bottom flask, and the solution is titrated to a colorless transparent solution. At the same time, the consumption of hydrochloric acid solution is recorded, and the content of ester species in the liquid phase product is calculated according to Formula II.

[0124]

[0125] In Formula I, n 酸 is the molar amount of acid species in the liquid phase product, with a unit of mol; CNaOH V represents the concentration of the sodium hydroxide solution, expressed in mol / L. NaOH The volume of sodium hydroxide solution titrated is expressed in L; m 滴定液相产物质量 The mass of the liquid product used in the titration is expressed in grams (g), and in this example, it is 1 g; m 液相产物总质量 The total mass of the liquid-phase products from the selective oxidation of cyclohexane in the examples is expressed in grams.

[0126]

[0127] In Equation II, n 酯 C represents the molar amount of ester species in the liquid-phase product, expressed in mol. NaOH The concentration of excess sodium hydroxide solution is expressed in mol / L; C HCl V represents the concentration of the hydrochloric acid solution, in mol / L. HCl The volume of hydrochloric acid solution titrated is expressed in L; m 滴定液相产物质量 The mass of the liquid product used in the titration is expressed in grams (g), and in this example, it is 1 g; m 液相产物总质量 The total mass of the liquid-phase products from the selective oxidation of cyclohexane in the examples is expressed in grams.

[0128] The liquid product prepared in Example 1 contained 0.0016 mol of acid species and 0.0005 mol of ester species. The liquid product prepared in Example 2 contained 0.0019 mol of acid species and 0.0015 mol of ester species. The liquid product prepared in Example 3 contained 0.0021 mol of acid species and 0.0017 mol of ester species. The liquid product prepared in Example 4 contained 0.0020 mol of acid species and 0.00112 mol of ester species. The liquid product prepared in Example 5 contained 0.0011 mol of acid species and 0.0007 mol of ester species.

[0129] Example 7

[0130] A method for determining the intermediate product cyclohexyl hydroperoxide: 1g of solution is taken from the liquid product of the selective oxidation reaction of cyclohexane in the examples, chlorobenzene is added as an internal standard, and the contents of cyclohexanol and cyclohexanone are determined by gas chromatography; 0.1g of triphenylphosphine is added to the 1g solution to reduce cyclohexyl hydroperoxide to cyclohexanol, and the content of cyclohexanol is determined by gas chromatography. The molar amount of the intermediate product cyclohexyl hydroperoxide is calculated by the difference in the molar amount of cyclohexanol before and after the addition of triphenylphosphine, as shown in Formula III.

[0131]

[0132] In formula III, n 环己基过氧化氢 is the molar amount of cyclohexyl hydroperoxide in the liquid phase product, unit: mol; n 加入三苯基磷后环己醇的摩尔量 is the molar amount of cyclohexanol measured after adding triphenyl phosphine, unit: mol; n 加入三苯基磷前环己醇的摩尔量 is the molar amount of cyclohexanol measured before adding triphenyl phosphine, unit: mol; m 取用液相产物的质量 is the mass taken out from the liquid phase product for detection, unit: g, 1 g in the present example; m 液相产物总质量 is the total mass of the liquid phase product of the selective oxidation reaction of cyclohexane in the example, unit: g.

[0133] The content of cyclohexyl hydroperoxide in the liquid phase product prepared in Example 1 is 0.00044 mol. The content of cyclohexyl hydroperoxide in the liquid phase product prepared in Example 2 is 0 mol. The content of cyclohexyl hydroperoxide in the liquid phase product prepared in Example 3 is 0 mol. The content of cyclohexyl hydroperoxide in the liquid phase product prepared in Example 4 is 0.001 mol. The content of cyclohexyl hydroperoxide in the liquid phase product prepared in Example 5 is 0.0011 mol.

[0134] Calibration method of standard solution

[0135] The calibration method of the standard solution used in the present application is as follows: 17 mol / L concentrated hydrochloric acid is added to 50 mL of deionized water to prepare a 0.1 mol / L hydrochloric acid solution; 4 g of sodium hydroxide (granular) is weighed and added to deionized water to prepare a 0.1 mol / L sodium hydroxide solution.

[0136] 0.1 g of anhydrous sodium carbonate is placed in a muffle furnace and calcined at 350℃ for 7 h to remove water, and 1 g is taken out and added to 50 mL of deionized water in a 250 mL conical flask to prepare a sodium carbonate solution; bromocresol green-methyl red titration indicator is added to the sodium carbonate solution, and the above-mentioned 0.1 mol / L hydrochloric acid solution is used to titrate the sodium carbonate solution, when the solution changes from green to dark red, it is the end point of titration, record the volume V1 of hydrochloric acid solution consumed when the solution changes color, at the same time, bromocresol green-methyl red indicator is added to the pure water solution, and the above-mentioned 0.1 mol / L hydrochloric acid solution is added dropwise, and the volume V0 of hydrochloric acid solution consumed when the solution changes color is recorded, and the accurate concentration of the hydrochloric acid solution is calculated using formula IV.

[0137]

[0138] In formula IV, C HCl is the concentration of the hydrochloric acid solution, unit: mol / L; m is the mass of anhydrous sodium carbonate after water removal, unit: g.

[0139] Take 0.1 g of hydrogen potassium phthalate into an oven 110℃ to dry overnight, add 50 mL of deionized water to make a hydrogen potassium phthalate solution in a conical flask, add 2 drops of phenolphthalein indicator, use the above prepared 0.1 mol / L sodium hydroxide solution to titrate the hydrogen potassium phthalate solution with known concentration, when the phenolphthalein reagent turns red, it is the end point of titration, record the volume V1 of sodium hydroxide solution consumed when the solution changes color; at the same time, add phenolphthalein reagent in pure water solution, and add the above 0.1 mol / L sodium hydroxide solution dropwise, record the volume V0 of sodium hydroxide solution consumed when the solution changes color, and calculate the accurate concentration of sodium hydroxide solution using formula V.

[0140]

[0141] In formula V, C NaOH is the concentration of sodium hydroxide solution, unit: mol / L; m is the mass of dried hydrogen potassium phthalate, unit: g.

[0142] The above only describes the preferred embodiments of the present application, it should be noted that for those skilled in the art, without departing from the principles of the present application, can make a number of improvements and refinements, these improvements and refinements should also be considered within the scope of the present application.

Claims

1. Use of a cobalt-based catalyst in the catalytic selective oxidation of cyclohexane, characterized in that, The preparation method of the cobalt-based catalyst comprises the following steps: 20mg of the Al2O3 carrier is weighed, ultrasonically dispersed using ethanol to obtain a carrier slurry with a concentration of 1g / L; the carrier slurry is coated on the surface of a silicon wafer with a size of 8cm*8cm and a coating thickness of 0.8mm, and dried at 25°C; The above carrier sample was placed in an ALD reaction cavity, high-purity nitrogen gas with a purity of 99.999% generated by a nitrogen generator was used as a carrier gas, the carrier gas flow was set to 50 sccm, the heating temperature of the cobaltocene was set to 90°C, the pulse time of the cobaltocene was 50 s, the holding time was 60 s, and the purge time was 70 s; after the cobaltocene precursor pulse entered the reaction cavity and reacted, ozone was pulsed again, and the cobaltocene was oxidized to CoO x by using ozone, the oxidation temperature was 190°C, the ozone was generated by high-purity oxygen with a purity of 99.99% through an ozone generator, the flow rate was 15 sccm, the pulse time was 25 s, the holding time was 75 s, and the purge time was 60 s; the above pulse cobaltocene-pulse ozone process was repeated to prepare 5Co / Al2O3 ultrafine nanoparticle cobalt-based catalyst, wherein "5" represents the number of alternating pulses, and the Co content of the cobalt-based catalyst was 0.52 wt%.

2. A process for the selective oxidation of cyclohexane, characterized in that, Comprising the following steps: The cobalt-based catalyst and cyclohexane are mixed, and a selective oxidation reaction is carried out in an oxygen atmosphere to obtain a liquid phase product; the liquid phase product comprises cyclohexanol and / or cyclohexanone; The preparation method of the cobalt-based catalyst comprises the following steps: 20mg of the Al2O3 carrier is weighed, ultrasonically dispersed using ethanol to obtain a carrier slurry with a concentration of 1g / L; the carrier slurry is coated on the surface of a silicon wafer with a size of 8cm*8cm and a coating thickness of 0.8mm, and dried at 25°C; The above carrier sample was placed in an ALD reaction cavity, high-purity nitrogen gas with a purity of 99.999% generated by a nitrogen generator was used as a carrier gas, the carrier gas flow was set to 50 sccm, the heating temperature of the cobaltocene was set to 90°C, the pulse time of the cobaltocene was 50 s, the holding time was 60 s, and the purge time was 70 s; after the cobaltocene precursor pulse entered the reaction cavity and reacted, ozone was pulsed again, and the cobaltocene was oxidized to CoO x by using ozone, the oxidation temperature was 190°C, the ozone was generated by high-purity oxygen with a purity of 99.99% through an ozone generator, the flow was 15 sccm, the pulse time was 25 s, the holding time was 75 s, and the purge time was 60 s; the above pulse cobaltocene-pulse ozone process was repeated to prepare 5Co / Al2O3 ultrafine nanoparticle cobalt-based catalyst, wherein "5" represents the number of alternating pulses, and the Co content of the cobalt-based catalyst was 0.52 wt%.

3. The method of claim 2, wherein, The mass ratio of the cobalt-based catalyst to cyclohexane is 1:500~1000.

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