阅读说明：本技术 一种纳米材料及其制备方法和环烷烃的催化氧化方法 (Nano material and preparation method thereof, and catalytic oxidation method of cycloparaffin ) 是由 史春风 康振辉 刘阳 黄慧 周赟杰 孙悦 蔺晓玲 王肖 于 2020-04-30 设计创作，主要内容包括：本发明涉及一种纳米材料及其制备方法和环烷烃的催化氧化方法,该方法包括：将第一导电物与直流电源的正极连接,将第二导电物与直流电源的负极连接后,将所述第一导电物和所述第二导电物置于电解液中,在10-80V的电压下电解1-10天,得到碳点溶液；其中,第一导电物为石墨棒,电解液为无机酸的水溶液；将碳点溶液、有机酸与钴源混合得到第一混合物,收集第一混合物中的第一固体；将第一固体、无机碱、过氧化氢和溶剂混合,在10-80℃保持1-10小时,得到第二混合物；将铂源与第二混合物混合,收集第二混合物中的第二固体并进行干燥。本发明的方法可以制备得到具有良好的催化性能的纳米材料。(The invention relates to a nano material and a preparation method thereof and a catalytic oxidation method of cycloparaffin, wherein the method comprises the following steps: connecting a first conductive object with the positive electrode of a direct current power supply, connecting a second conductive object with the negative electrode of the direct current power supply, placing the first conductive object and the second conductive object in an electrolyte, and electrolyzing for 1-10 days under the voltage of 10-80V to obtain a carbon dot solution; wherein the first conductor is a graphite rod, and the electrolyte is an aqueous solution of inorganic acid; mixing the carbon dot solution, the organic acid and the cobalt source to obtain a first mixture, and collecting a first solid in the first mixture; mixing the first solid, inorganic base, hydrogen peroxide and solvent, and keeping the mixture at the temperature of 10-80 ℃ for 1-10 hours to obtain a second mixture; a source of platinum is mixed with the second mixture, and a second solid in the second mixture is collected and dried. The method can prepare the nano material with good catalytic performance.)

1. A method of preparing a nanomaterial, the method comprising:

s1, connecting the first conducting object with the positive pole of a direct current power supply, connecting the second conducting object with the negative pole of the direct current power supply, placing the first conducting object and the second conducting object in electrolyte, and electrolyzing for 1-10 days under the voltage of 10-80V to obtain a carbon dot solution; wherein the first conductor is a graphite rod, and the electrolyte is an aqueous solution of inorganic acid;

s2, mixing the carbon dot solution, the organic acid and a cobalt source to obtain a first mixture, and collecting a first solid in the first mixture;

s3, mixing the first solid, inorganic base, hydrogen peroxide and solvent, and keeping the mixture at 0-90 ℃ for 1-24 hours to obtain a second mixture;

s4, mixing a platinum source with the second mixture, collecting the solid and drying.

2. The method of claim 1, wherein, in S1, the concentration of the carbon dot solution is 10-1000 mg/L; the concentration of the inorganic acid aqueous solution is 5-1000 mmol/L.

3. The method of claim 1, wherein S2 includes: dividing the carbon dot solution into a first part of carbon dot solution and a second part of carbon dot solution;

mixing the organic acid with the first part of the carbon dot solution to obtain a third mixture, mixing the cobalt source with the second part of the carbon dot solution to obtain a fourth mixture, and mixing the third mixture with the fourth mixture to obtain a first mixture.

4. The method of claim 1, wherein in S2, the weight ratio of the carbon dot solution, the organic acid, and the cobalt source is 100: (1-200): (1-100).

5. The method of claim 1, wherein the weight ratio of the first solid, the inorganic base, and the hydrogen peroxide in S3 is 100: (5-200): (1-100).

6. The method of claim 1, wherein S4 includes: collecting a second solid in the second mixture and vacuum drying; the vacuum drying conditions include: the temperature is 20-200 ℃, the pressure is 0-0.1MPa, and the time is 1-24 hours;

the weight ratio of the platinum source to the second mixture is 100: (20-1000).

7. The method according to claim 1, wherein the inorganic acid is selected from one or more of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, perchloric acid, hydrobromic acid, hydroiodic acid, nitrous acid, phosphorous acid and sulfurous acid;

the organic acid is selected from one or more of oxalic acid, acetic acid, adipic acid, ascorbic acid, citric acid and lactic acid;

the cobalt source is selected from one or more of cobalt sulfate, cobalt nitrate, cobalt phosphate and cobalt chloride;

the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, ammonia water and hydrazine hydrate;

the platinum source is selected from one or more of chloroplatinic acid, platinum nitrate, platinum acetylacetonate, platinum chloroaminoxide and platinum acetate.

8. The nanomaterial prepared by the method of any one of claims 1 to 7.

9. A process for the catalytic oxidation of a cycloalkane, the process comprising: contacting a cycloalkane with an oxidizing agent in the presence of a catalyst to effect an oxidation reaction, said catalyst comprising the nanomaterial defined in claim 8.

10. The method of claim 9, wherein the oxidation reaction conditions comprise: the temperature is 60-200 ℃, the pressure is 0.1-5MPa, and the time is 0.1-24 hours;

the cycloalkane is C5-C12 monocycloparaffin and/or C8-C16 bicycloalkane;

the weight ratio of the cycloalkane to the catalyst is 100: (0.1-20);

the oxidant is an oxygen-containing gas having an oxygen concentration greater than 10% by volume; the weight ratio of oxygen in the oxygen-containing gas to the cycloalkane is greater than 1.

Technical Field

The invention relates to a nano material and a preparation method thereof, and a catalytic oxidation method of cycloalkane.

Background

In the fields of hydrocarbon selective oxidation catalysis application and the like, carbon dots and other nano-carbon materials have good application prospects, but the existing carbon nano-materials need to be improved and optimized in the aspects of material performance and the like, and further research and development need to be carried out by vast scientific and technological workers to promote industrial upgrading transformation of the petrochemical industry. In the selective oxidation reaction of hydrocarbons, the oxidation conversion of cycloalkanes to ketones and the oxidation conversion of acids such as cyclohexane to cyclohexanone, adipic acid and other oxygen-containing organic chemicals play an important role in national production. The existing air oxidation method and catalytic oxidation preparation technology and the like need to be improved in many aspects.

Disclosure of Invention

The invention aims to provide a nano material, a preparation method thereof and a catalytic oxidation method of cycloalkane, the nano material with good catalytic performance can be prepared by the method, and the conversion rate of raw materials and the selectivity of target products, especially acids, can be improved by applying the nano material to the catalytic oxidation process of cycloalkane.

In order to achieve the above object, a first aspect of the present invention provides a method for preparing a nanomaterial, the method comprising:

s1, connecting the first conducting object with the positive pole of a direct current power supply, connecting the second conducting object with the negative pole of the direct current power supply, placing the first conducting object and the second conducting object in electrolyte, and electrolyzing for 1-10 days under the voltage of 10-80V to obtain a carbon dot solution; wherein the first conductor is a graphite rod, and the electrolyte is an aqueous solution of inorganic acid;

s2, mixing the carbon dot solution, the organic acid and a cobalt source to obtain a first mixture, and collecting a first solid in the first mixture;

s3, mixing the first solid, inorganic base, hydrogen peroxide and solvent, and keeping the mixture at 0-90 ℃ for 1-24 hours to obtain a second mixture;

s4, mixing a platinum source with the second mixture, collecting the solid and drying.

Optionally, in S1, the concentration of the carbon dot solution is 10-1000 mg/L; the concentration of the inorganic acid aqueous solution is 5-1000 mmol/L.

Optionally, S2 includes: dividing the carbon dot solution into a first part of carbon dot solution and a second part of carbon dot solution;

mixing the organic acid with the first part of the carbon dot solution to obtain a third mixture, mixing the cobalt source with the second part of the carbon dot solution to obtain a fourth mixture, and mixing the third mixture with the fourth mixture to obtain a first mixture.

Optionally, in S2, the weight ratio of the carbon dot solution, the organic acid, and the cobalt source is 100: (1-200): (1-100).

Optionally, in S3, the weight ratio of the first solid, the inorganic base, and the hydrogen peroxide is 100: (5-200): (1-100).

Optionally, S4 includes: collecting a second solid in the second mixture and vacuum drying; the vacuum drying conditions include: the temperature is 20-200 ℃, the pressure is 0-0.1MPa, and the time is 1-24 hours;

the weight ratio of the platinum source to the second mixture is 100: (20-1000).

Optionally, the inorganic acid is selected from one or more of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, perchloric acid, hydrobromic acid, hydroiodic acid, nitrous acid, phosphorous acid and sulfurous acid;

the organic acid is selected from one or more of oxalic acid, acetic acid, adipic acid, ascorbic acid, citric acid and lactic acid;

the cobalt source is selected from one or more of cobalt sulfate, cobalt nitrate, cobalt phosphate and cobalt chloride;

the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, ammonia water and hydrazine hydrate;

the platinum source is selected from one or more of chloroplatinic acid, platinum nitrate, platinum acetylacetonate, platinum chloroaminoxide and platinum acetate.

In a second aspect, the invention provides a nanomaterial prepared by the method provided in the first aspect of the invention.

In a third aspect, the present invention provides a process for the catalytic oxidation of a cycloalkane, the process comprising: the oxidation reaction is carried out by contacting a cycloalkane with an oxidant in the presence of a catalyst comprising a nanomaterial provided by the second aspect of the present invention.

Optionally, the conditions of the oxidation reaction include: the temperature is 60-200 ℃, the pressure is 0.1-5MPa, and the time is 0.1-24 hours;

the cycloalkane is C5-C12 monocycloparaffin and/or C8-C16 bicycloalkane;

the weight ratio of the cycloalkane to the catalyst is 100: (0.1-20);

the oxidant is an oxygen-containing gas having an oxygen concentration greater than 10% by volume; the weight ratio of oxygen in the oxygen-containing gas to the cycloalkane is greater than 1.

Through the technical scheme, the method can prepare the nano material with better catalytic performance, and when the nano material is used for catalytic oxidation of cycloalkane, the conversion rate of reactants is high, the selectivity of products is higher, and especially the selectivity of acids is high.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

In a first aspect, the present invention provides a method for preparing a nanomaterial, the method comprising:

s1, connecting the first conducting object with the positive pole of a direct current power supply, connecting the second conducting object with the negative pole of the direct current power supply, placing the first conducting object and the second conducting object in electrolyte, and electrolyzing for 1-10 days under the voltage of 10-80V to obtain a carbon dot solution; wherein the first conductor is a graphite rod, and the electrolyte is an aqueous solution of inorganic acid;

s2, mixing the carbon dot solution, the organic acid and the cobalt source to obtain a first mixture, and collecting a first solid in the first mixture;

s3, mixing the first solid, inorganic base, hydrogen peroxide and solvent, and keeping the mixture at 0-90 ℃ for 1-24 hours to obtain a second mixture;

s4, mixing a platinum source with the second mixture, collecting the solid and drying.

The method can prepare the nano material with good catalytic performance, can realize the oxidation of cycloalkane under mild conditions, has high cyclohexane conversion rate, and has high selectivity of target products, particularly high selectivity of acids.

The amount of the electrolyte used according to the present invention is not particularly limited, and may be selected according to the actual requirements, for example, the size of the first conductor and the second conductor and the electrolysis conditions. In a preferred embodiment, the dimensions of the first conductor are matched to those of the second conductor, and the dimensions of the first conductor may vary over a wide range, for example, the graphite rod may have a diameter of 3 to 20mm and a length of 5 to 50cm, where length refers to the axial length of the graphite rod. The second conductive material is not particularly limited in kind and shape, and may be any conductive material, for example, iron, copper, platinum, graphite, and the like, and graphite is preferable, and the shape may be rod-like, plate-like, and the like, and is preferably rod-like. When the electrolysis is performed, a certain distance may be maintained between the first conductive object and the second conductive object, and may be, for example, 5 to 40 cm.

According to the present invention, in S1, the inorganic acid is well known to those skilled in the art, and may be, for example, one or more selected from sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, perchloric acid, hydrobromic acid, hydroiodic acid, nitrous acid, phosphorous acid and sulfurous acid, and is preferably sulfuric acid.

According to the present invention, the concentration of the carbon dot solution in S1 may be 10 to 1000mg/L, preferably 50 to 500 mg/L. In a preferred embodiment, the concentration of the aqueous solution of the inorganic acid may be in the range of 5 to 1000mmol/L, preferably 20 to 200 mmol/L.

In a preferred embodiment, S2 includes: dividing the carbon dot solution into a first part of carbon dot solution and a second part of carbon dot solution; mixing an organic acid with the first portion of the carbon dot solution to obtain a third mixture, mixing a cobalt source with the second portion of the carbon dot solution to obtain a fourth mixture, and mixing the third mixture and the fourth mixture to obtain the first mixture. Preferably, the organic acid is mixed with the first part of the carbon dot solution and the cobalt source is mixed with the second part of the carbon dot solution under stirring; stirring is well known to those skilled in the art and may be, for example, mechanical stirring. The nanometer material with better catalytic performance can be prepared by adopting the method.

According to the present invention, in S2, the method for collecting the first solid is not particularly limited, for example, the first solid may be collected by centrifugation or filtration, preferably, the collected first solid may be washed and dried, the solution used for washing is not particularly limited, for example, deionized water may be used for washing, and drying may be performed in a vacuum drying oven, preferably, vacuum drying is performed at a temperature of 40 to 160 ℃ and a pressure of 0 to 0.1MPa for 1 to 24 hours.

According to the invention, the weight ratio of the carbon dot solution, the organic acid and the cobalt source in S2 may vary within a wide range, and may be, for example, 100: (1-200): (1-100); preferably, the weight ratio of the carbon dot solution, the organic acid and the cobalt source is 100: (5-100): (2-50), more preferably 100: (10-80): (5-30). Among them, the organic acid is well known to those skilled in the art, and may be selected from one or more of oxalic acid, acetic acid, adipic acid, ascorbic acid, citric acid, lactic acid, and the like, preferably oxalic acid; the cobalt source is a compound containing cobalt, and may be one or more selected from cobalt sulfate, cobalt nitrate, cobalt phosphate, cobalt chloride, and the like, for example, and is preferably cobalt sulfate. The nano material with better catalytic performance can be prepared in the dosage range.

In a preferred embodiment, S3 includes: mixing the first solid, an inorganic base and a solvent to sufficiently disperse the first solid, adding hydrogen peroxide to the resulting mixture, and holding at 0-90 deg.C for 1-24 hours, preferably, at 10-80 deg.C for 2-12 hours. The solvent is not particularly limited, and may be deionized water or an organic solvent, such as ketone, alcohol, acid, ester, sulfone, ether, etc., preferably deionized water.

According to the invention, the weight ratio of the amounts of first solid, inorganic base and hydrogen peroxide in S3 may vary within a wide range, and may be, for example, 100: (5-200): (1-100), preferably 100: (10-100): (2-50), more preferably 100: (20-80): (5-30). Among them, inorganic bases are well known to those skilled in the art, and may be selected from one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, ammonia water and hydrazine hydrate, for example.

According to the present invention, S4 may include: collecting the second solid in the second mixture and vacuum drying; the conditions for vacuum drying may include: the temperature is 20-200 deg.C, pressure is 0-0.1MPa, and time is 1-24 hr, preferably, temperature is 40-100 deg.C, pressure is 0-0.08MPa, and time is 2-12 hr. The vacuum drying can be carried out in an apparatus conventionally used by those skilled in the art, and for example, the vacuum drying can be carried out in a vacuum drying oven.

According to the invention, in S4, the platinum source is one or more selected from chloroplatinic acid, platinum nitrate, platinum acetylacetonate, platinum chloroamidinate and platinum acetate, and is preferably chloroplatinic acid. The weight ratio of the platinum source to the second mixture is 100: (20-1000), preferably 100: (50-500).

In a second aspect, the present invention provides a nanomaterial prepared by the method provided in the first aspect of the present invention.

In a third aspect, the present invention provides a process for the catalytic oxidation of a cycloalkane, the process comprising: the oxidation reaction is carried out by contacting a cycloalkane with an oxidant in the presence of a catalyst comprising a nanomaterial provided by the second aspect of the present invention.

According to the invention, the cycloalkane may be a C5-C12 monocycloparaffin and/or a C8-C16 bicycloalkane. Further, when the cycloalkane is a monocyclic cycloalkane selected from substituted C5-C12 and/or substituted bicyclic cycloalkane selected from substituted C8-C16, the substituent may be halogen or methyl. In a preferred embodiment, the cycloalkane may be cyclohexane, cyclopentane, bicyclohexane, methylcyclohexane, halocyclohexane, methylcyclopentane, bromocyclohexane, chlorocyclopentane, and the like, preferably cyclohexane.

According to the present invention, the catalyst may also contain a catalyst for catalytic oxidation of alkane, which is conventionally used by those skilled in the art, and may be, for example, one or more of titanium silicalite, high-valence transition metal salt, transition metal oxide, heteropoly acid and heteropoly acid salt; the high-valence transition metal salt can be one or more of sodium tungstate, potassium vanadate, potassium permanganate and potassium dichromate, the transition metal oxide can be one or more of copper oxide, iron oxide, titanium oxide and zinc oxide, the heteropoly acid can be one or more of phosphotungstic heteropoly acid, phosphomolybdic heteropoly acid, silicotungstic heteropoly acid and silicomolybdic heteropoly acid, and the heteropoly acid salt can be one or more of phosphotungstic heteropoly acid sodium, phosphomolybdic heteropoly acid potassium and phosphotungstic heteropoly acid cesium.

In a preferred embodiment, the catalyst is a nanomaterial of the present invention, and the weight ratio of cycloalkane to catalyst may be 100: (0.1-20), preferably 100: (0.5-5).

According to the present invention, the oxidation reaction can be carried out in a catalytic reactor well known to those skilled in the art, for example, in a batch tank reactor, a fixed bed reactor, a moving bed reactor, a suspended bed reactor or a slurry bed reactor. The amount of the catalyst to be used may be appropriately selected depending on the amounts of the cycloalkane and the oxidizing agent, and the reactor.

In one embodiment, the oxidation reaction is carried out in a slurry bed reactor, and the amount of catalyst used may be in the range of 0.1 to 20g, preferably 0.5 to 5g, based on 100mL of cycloalkane, based on the nanomaterial of the present invention contained in the catalyst.

In another embodiment, the oxidation reaction is carried out in a fixed bed reactor and the weight hourly space velocity of the cyclic hydrocarbon may be in the range of from 0.01 to 10h^-1Preferably 0.05 to 2h^-1。

According to the present invention, the conditions of the oxidation reaction may include: the temperature is 60-200 ℃, the pressure is 0.1-5MPa, and the time is 0.1-24 hours; preferably, the temperature is 80-180 ℃, the pressure is 0.5-3MPa, and the time is 1-12 hours.

According to the present invention, the oxidizing agent is conventionally used by those skilled in the art, for example, the oxidizing agent is an oxygen-containing gas, preferably air or oxygen, in which case the oxidation reaction can be performed without using an initiator, the effect is similar to that in the presence of an initiator, the addition of the initiator can be avoided, and the subsequent separation and purification process can be simplified. In one embodiment, the oxygen concentration of the oxygen-containing gas may be greater than 10% by volume. The molar ratio of the cycloalkane to the oxygen-containing gas of the medium oxygen can vary within wide limits, for example the molar amount of oxygen in the oxygen-containing gas can be from 1 to 20 times the theoretical oxygen demand for oxidation of the cycloalkane to the desired product. In one embodiment, the mass ratio of oxygen to cycloalkanes in the oxygen-containing gas is greater than 1, preferably (2-10): 1.

the invention is further illustrated by the following examples, but is not to be construed as being limited thereto.

The reagents adopted by the invention are all commercial analytical pure reagents.

Examples 1 to 7 are for illustrating the nanomaterial of the present invention and the method of preparing the same, and comparative examples 1 to 6 are for illustrating the nanomaterial different from the present invention and the method of preparing the same.

Example 1

S1, adding 5000mL of sulfuric acid aqueous solution with the concentration of 120mmol/L into a beaker to serve as electrolyte, placing an anode graphite rod (with the diameter of 8mm and the length of 50cm) and a cathode graphite rod (with the diameter of 8mm and the length of 50cm) into the beaker, keeping the distance between the anode graphite rod and the cathode rod to be 10cm, connecting the anode graphite rod with the positive electrode of a direct current power supply, connecting the cathode rod with the negative electrode of the direct current power supply, and applying 25V voltage to electrolyze for 5 days to obtain carbon dot solution; the concentration of the carbon dot solution is 210 mg/L;

s2, dividing the carbon dot solution into two parts with equal volume, mixing cobalt sulfate with the first part of the carbon dot solution, and stirring in an auxiliary manner in the process to obtain a third mixture; mixing oxalic acid and the second part of carbon dot solution, wherein stirring can be assisted in the process to obtain a fourth mixture; and slowly and uniformly mixing the third mixture and the fourth mixture to obtain a first mixture, centrifuging the first mixture to collect a solid, washing the solid with deionized water, and performing vacuum drying at 60 ℃ and 0.05MPa for 8 hours to obtain a first solid, wherein the weight ratio of the carbon dot solution to the use amount of oxalic acid to the use amount of cobalt sulfate is 100: 16: 45, a first step of;

s3, mixing the first solid, sodium hydroxide and deionized water under stirring, adding hydrogen peroxide into the mixture, and keeping the mixture at 60 ℃ for 16 hours to obtain a second mixture, wherein the weight ratio of the first solid to the amount of the sodium hydroxide to the amount of the hydrogen peroxide is 100: 25: 12;

s4, mixing chloroplatinic acid and the second mixture, centrifuging the mixture at 15 ℃ to collect a second solid, washing the second solid by absolute ethyl alcohol, and performing vacuum drying at 80 ℃ and 0.02MPa for 6 hours to obtain the nanometer material A1. Wherein the weight ratio of the chloroplatinic acid to the second mixture is 100: 425.

example 2

Nanomaterial a2 was prepared in the same manner as in example 1, except that in S2, the weight ratio of the first solid, the carbon dot solution, the oxalic acid, and the cobalt sulfate was 100: 220: 45.

example 3

Nanomaterial a3 was prepared in the same manner as in example 1, except that in S3, the weight ratio of the amounts of the first solid, sodium hydroxide and hydrogen peroxide was 100: 210: 105.

example 4

Nanomaterial a4 was prepared in the same manner as in example 1, except that in S4, the weight ratio of the amount of chloroplatinic acid and the amount of the second mixture was 100: 10.

example 5

Nanomaterial a5 was prepared in the same manner as in example 1, except that, in S2, the carbon dot solution was not divided into two equal parts by volume, but the carbon dot solution, cobalt sulfate, and oxalic acid were mixed to obtain a first mixture.

Example 6

A nanomaterial A6 was prepared in the same manner as in example 1, except that 5000mL of an aqueous solution of sulfuric acid having a concentration of 4mmol/L was added as an electrolyte in a beaker in S1.

Example 7

A nano-material A7 was prepared in the same manner as in example 1, except that 5000mL of an aqueous solution of hydroiodic acid having a concentration of 120mmol/L was added as an electrolyte in a beaker in S1.

Comparative example 1

The nanomaterial DA1 was prepared in the same manner as in preparation example 1, except that in S2, a carbon dot solution, hydrochloric acid, and a cobalt source were mixed to obtain a first mixture.

Comparative example 2

Nanomaterial DA2 was prepared in the same manner as in preparative example 1, except that in S3, hydrogen peroxide was not used, but the first solid, inorganic base and deionized water were mixed and maintained at 60 ℃ for 16 hours to give a second mixture.

Comparative example 3

Nanomaterial DA3 was prepared using the same method as in preparative example 1, except that no S4 was used, and the solids in the second mixture were collected directly and dried.

Comparative example 4

Nanomaterial DA4 was prepared in the same manner as in preparative example 1, except that no S3 was used, the first solid obtained in S2 was mixed with a platinum source, and the solid was collected and dried.

Comparative example 5

Nanomaterial DA5 was prepared in the same manner as in preparative example 1, except that in S3, the first solid, inorganic base, hydrogen peroxide and deionized water were mixed and maintained at 110 ℃ for 10 hours to give a second mixture.

Comparative example 6

Nanomaterial DA6 was prepared in the same manner as in preparative example 1, except that in S3, the first solid, propylamine, hydrogen peroxide and deionized water were mixed and maintained at 60 ℃ for 16 hours to give a second mixture.

In the following test examples, the oxidation products were analyzed by gas chromatography (GC: Agilent, 7890A) and gas chromatography-mass spectrometer (GC-MS: Thermo Fisher Trace ISQ). Conditions of gas chromatography: nitrogen carrier gas, temperature programmed at 140K: 60 ℃, 1 minute, 15 ℃/minute, 180 ℃, 15 minutes; split ratio, 10: 1; the injection port temperature is 300 ℃; detector temperature, 300 ℃. On the basis, the conversion rate of raw materials and the selectivity of target products are calculated by respectively adopting the following formulas:

naphthene conversion = (molar amount of naphthene added before reaction-molar amount of naphthene remaining after reaction)/molar amount of naphthene added before reaction × 100%;

target product selectivity ═ mol of target product formed after the reaction)/mol of cycloalkane added before the reaction × 100%.

Test example

50mg of the nanomaterial prepared in examples 1 to 7 and comparative examples 1 to 6 was charged as a catalyst and 100mL of cyclohexane, respectively, into a 250mL autoclave, sealed, charged with oxygen (molar ratio of oxygen to cyclohexane was 8: 1), and after stirring the mixture at 130 ℃ and 2.5MPa for reaction for 3 hours, the catalyst was separated by centrifugation and filtration after cooling, pressure-releasing sampling, and the results of analysis of the oxidized product are shown in Table 1.

TABLE 1

	Catalyst numbering	Cyclohexane conversion rate%	Adipic acid selectivity,%
				Example 1	A1	37	64
Example 2	A2	31	60
				Example 3	A3	29	51
Example 4	A4	30	57
				Example 5	A5	28	56
Example 6	A6	32	55
				Example 7	A7	33	60
Comparative example 1	DA1	21	28
				Comparative example 2	DA2	24	39
Comparative example 3	DA3	9	12
				Comparative example 4	DA4	26	33
Comparative example 5	DA5	25	37
				Comparative example 6	DA6	22	25

As can be seen from the data in Table 1, when the nanomaterial prepared by the method of the invention is used in the catalytic oxidation process of cycloalkane, the conversion rate of cyclohexane is high, and the selectivity of adipic acid is high. Comparing the results of examples 2-7 with those of example 1, the weight ratio of the carbon dot solution, the organic acid and the cobalt source is preferably 100: (1-200): (1-100), the prepared nano material has better catalytic performance; preferably, the weight ratio of the first solid, the inorganic base and the hydrogen peroxide is 100: (5-200): (1-100), the prepared nano material has better catalytic performance; preferably, the weight ratio of the platinum source to the amount of the second mixture is 100: (20-1000), the prepared nano material has better catalytic performance; preferably, the carbon dot solution is divided into a first part of carbon dot solution and a second part of carbon dot solution and then is respectively mixed with the organic acid and the cobalt source, so that the prepared nano material has better catalytic performance; when the concentration of the aqueous solution of the inorganic acid is preferably 5-1000mmol/L, the prepared nano material has better catalytic performance; in S2, when the inorganic acid is preferably sulfuric acid, the prepared nano material has better catalytic performance.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.