Iron-containing porous nanomaterials, their preparation methods, and their application in the preparation of phenol from benzene by N2O oxidation.

Abstract

This invention relates to a method for preparing iron-containing porous nanomaterials. The method includes: (1) placing a first conductive material and a second conductive material, respectively connected to the positive and negative electrodes of a DC power supply, in an aqueous solution of an organic base containing a silicon source, and electrolyzing at a voltage of 1-36V for 1-8 days to obtain a carbon dot solution containing a silicon source and an organic base; wherein the first conductive material is a graphite molded body; (2) directly mixing an iron source, a polyhydroxy aliphatic compound, and the carbon dot solution containing a silicon source and an organic base to obtain a liquid mixture; (3) placing the liquid mixture in a pressure-resistant and heat-resistant sealed container and subjecting it to a hydrothermal reaction at 100-200℃ for 6-48 hours, and then removing the solid. The method of this invention has a good catalytic effect in the oxidation of benzene to phenol using N2O, which is beneficial to improving the conversion rate of benzene and the selectivity of phenol.

Description

Technical Field

[0001] This application relates to an iron-containing porous nanomaterial, its preparation method, and its application in the preparation of phenol by N2O oxidation of benzene. Background Technology

[0002] The petrochemical industry is a pillar industry in my country, closely related to people's production and daily lives. Basic organic raw materials and chemicals play a vital role in petrochemical production; modern life, including clothing, food, housing, and transportation, is inseparable from these components. There is an urgent need to develop clean and efficient new preparation processes to promote the upgrading and transformation of the petrochemical industry.

[0003] The development of new processes requires innovative catalysts, and new catalytic materials are the source of innovation in both catalysts and processes. The emergence of nano-carbon materials provides new opportunities for the upgrading and transformation of the petrochemical industry. Nano-carbon materials refer to tiny carbon particles with sizes in the nanometer range (1-100 nm). Similar to ordinary nanomaterials, they also possess unique properties such as quantum size effects, small size effects, and macroscopic quantum tunneling effects in optics, electricity, and magnetism. In 2004, tiny carbon nanoparticles smaller than 10 nm, discovered during the purification of monolayer carbon nanotubes by electrophoresis, were first named carbon dots, a novel type of small-sized carbon nanomaterial. Based on this, carbon dots are expected to be applied in energy issues, environmental protection, photovoltaic devices, and other related fields. In areas such as selective catalysis of hydrocarbons, porous materials such as molecular sieves are important catalytic materials. However, existing porous materials such as molecular sieves still need improvement and optimization in terms of material properties. Nano-carbon materials such as carbon dots also have great potential in the preparation and modification of porous materials, and deserve in-depth research and industrial development by a wide range of scientific and technological workers to promote technological development in areas such as selective catalysis of hydrocarbons. Summary of the Invention

[0004] The purpose of this invention is to provide an iron-containing porous nanomaterial, its preparation method, and its application in the N2O oxidation of benzene to phenol. The iron-containing porous nanomaterial prepared by the method of this invention has good catalytic effect in the N2O oxidation of benzene to phenol, which is beneficial to improving the conversion rate of benzene and the selectivity of phenol.

[0005] To achieve the above objectives, a first aspect of the present invention provides a method for preparing iron-containing porous nanomaterials, the method comprising:

[0006] (1) The first conductive material and the second conductive material, which are respectively connected to the positive and negative terminals of the DC power supply, are placed in an aqueous solution of organic base containing silicon source and electrolyzed for 1-8 days at a voltage of 1-36V to obtain a carbon dot solution containing silicon source and organic base; wherein, the first conductive material is a graphite molded body.

[0007] (2) The iron source, the polyhydroxy aliphatic compound and the carbon point solution containing the silicon source and organic base are directly mixed to obtain a liquid mixture;

[0008] (3) Place the liquid mixture in a pressure-resistant and heat-resistant sealed container and carry out a hydrothermal reaction at 100-200℃ for 6-48 hours, then remove the solid.

[0009] Optionally, in step (1), the concentration of the organic base in the aqueous solution containing the silicon source is 10-2500 mmol / L, preferably 50-1500 mmol / L; the concentration of the silicon source is 0.1-10 mol / L, preferably 0.5-5 mol / L.

[0010] The concentration of carbon dots in the carbon dot solution is 1-1000 mg / L, preferably 10-500 mg / L.

[0011] Optionally, in step (2), the weight ratio of the iron source, the polyhydroxy aliphatic compound, and the carbon dot solution is 1:(0.1-10):(10-200); preferably, the weight ratio of the iron source, the polyhydroxy aliphatic compound, and the carbon dot solution is 1:(0.2-5):(20-150).

[0012] Optionally, in step (3), the temperature of the hydrothermal reaction is 120-180℃ and the time is 12-36 hours.

[0013] Optionally, step (2) includes: first mixing the iron source with the polyhydroxy aliphatic compound, then mixing the resulting mixture with the carbon dot solution to obtain a liquid mixture;

[0014] The temperature of the first mixing is 10-95℃ and the time is 1-10 min; the temperature of the second mixing is 20-60℃ and the time is 5-30 min.

[0015] Optionally, the silicon source is an organosilicon source and / or an inorganic silicon source; the organosilicon source is tetramethyl silicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, or dimethoxydiethoxysilane, or a combination of two or three of them; the inorganic silicon source is silica sol and / or silica gel.

[0016] The iron source includes one or more of ferric nitrate, ferric chloride, ferric sulfate, ferric phosphate, and ferric acetate, preferably ferric nitrate;

[0017] The polyhydroxy aliphatic compound includes one or more of ethylene glycol, glycerol, propylene glycol, hexanediol, and cyclohexanediol, preferably ethylene glycol;

[0018] The organic base is selected from quaternary ammonium bases, aliphatic amines, or alkanolamines, or a combination of two or three of them; wherein the quaternary ammonium base is tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, or a combination of two or three of them; the aliphatic amine is ethylamine, n-butylamine, butanediamine, or hexamethylenediamine, or a combination of two or three of them; and the alkanolamine is selected from monoethanolamine, diethanolamine, or triethanolamine, or a combination of two or three of them.

[0019] Optionally, in step (1), the electrolysis voltage is 5-25V and the time is 2-5 days.

[0020] The second aspect of the present invention provides an iron-containing porous nanomaterial prepared by the method provided in the first aspect of the present invention.

[0021] Optionally, the iron content of the iron-containing porous nanomaterial, calculated as Fe2O3, is 0.1-5% by weight, preferably 0.5-2.5% by weight; the distribution deviation of iron element inside and on the surface of the iron-containing porous nanomaterial particles is not greater than 50%, preferably not greater than 30%; the average particle size of the iron-containing porous nanomaterial is 50-200 nm, preferably 80-150 nm.

[0022] The third aspect of this invention provides the application of the iron-containing porous nanomaterials provided in the second aspect of this invention in the preparation of phenol by N2O oxidation of benzene.

[0023] Through the above technical solution, the method of the present invention can effectively reduce the amount of polyhydroxy aliphatic compounds used, shorten the hydrothermal reaction time, and obtain iron-containing porous nanomaterials with small particle size and uniform distribution. The iron element distribution deviation inside and on the surface of the particles is no more than 50% (i.e., the difference between the iron content inside the particles and the iron content on the surface of the iron-containing porous nanomaterials is less than or equal to 50%). This is beneficial to improving the accessibility of the active centers of the iron-containing porous nanomaterials, which is conducive to the diffusion of reactants and products, thereby improving its catalytic reaction performance. When used in benzene oxidation reaction, it can improve the conversion rate of benzene and the selectivity of the target product phenol.

[0024] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0025] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0026] The first aspect of this invention provides a method for preparing iron-containing porous nanomaterials, the method comprising:

[0027] (1) The first and second conductive materials, which are respectively connected to the positive and negative terminals of a DC power supply, are placed in an aqueous solution of an organic base containing a silicon source and electrolyzed for 1-8 days at a voltage of 1-36V to obtain a carbon dot solution containing a silicon source and an organic base; wherein, the first conductive material is a graphite molded body; (2) The iron source, the polyhydroxy aliphatic compound and the carbon dot solution containing a silicon source and an organic base are directly mixed to obtain a liquid mixture; (3) The liquid mixture is placed in a pressure-resistant and heat-resistant sealed container and subjected to a hydrothermal reaction at 100-200℃ for 6-48h, and the solid is taken out.

[0028] This invention breaks away from the traditional material mixing steps in the synthesis of porous materials. Firstly, it uses an electrolyte containing a silicon source and an organic base to electrolyze graphite to prepare a carbon dot solution. This effectively controls the hydrolysis process of the silicon source, organically integrating it with the graphite electrolysis process, eliminating the need for a separate silicon source hydrolysis time. When introducing the iron source, a small amount of polyhydroxy aliphatic compound is used for protection, reducing the mixing time for iron source introduction and shortening the hydrothermal reaction time, which is more conducive to the preparation of iron-containing porous nanomaterials. The iron-containing porous nanomaterials prepared using this method have small and uniform particle sizes, with iron elements distributed uniformly both inside and on the surface of the particles, with a deviation of no more than 50%. The increased accessibility of the active centers in the obtained iron-containing porous nanomaterials also facilitates the diffusion of reactants and products, thereby improving their catalytic performance. When used in benzene oxidation reactions, it can improve the conversion rate of benzene and the selectivity of the target product phenol.

[0029] According to the present invention, there are no specific limitations on the type and shape of the second conductive material, which can be made of any conductive material, such as iron, copper, graphite, etc., preferably graphite, and can be rod-shaped, plate-shaped, etc., preferably rod-shaped. There are also no specific limitations on the amount of electrolyte used, which can be selected according to actual needs, such as based on the dimensions of the first and second conductive materials and the electrolysis conditions. In a preferred embodiment, the dimensions of the first conductive material match the dimensions of the second conductive material. The dimensions of the first conductive material can vary within a wide range; for example, the graphite molding body is a graphite rod with a diameter of 55 mm and a length of 15-90 cm, where the length refers to the axial length of the graphite rod. During electrolysis, a certain distance can be maintained between the first and second conductive materials, for example, 10-50 cm.

[0030] According to the present invention, there are no specific limitations on the method of removing the solid; for example, the solid can be removed by centrifugation or filtration. In one specific embodiment of the present invention, the removed solid is sequentially washed, dried, and calcined. There are no specific limitations on the washing solution; for example, deionized water can be used. Drying can be carried out in a vacuum drying oven, preferably at a temperature of 80-160°C and a pressure of 0-0.1 MPa for 1-25 hours. Calcination can be carried out in a muffle furnace or a tube furnace at a temperature of 350-800°C and a pressure of 0-0.2 MPa. Calcination can be carried out in an air atmosphere or an inert atmosphere, and the inert gas contained in the inert atmosphere can be nitrogen, argon, helium, carbon dioxide, etc.

[0031] According to the present invention, the concentration of the aqueous solution of the organic base can vary within a wide range. In a specific embodiment of the present invention, in step (1), the concentration of the organic base in the aqueous solution containing the silicon source is 10-2500 mmol / L, preferably 50-1500 mmol / L; the concentration of the added silicon source is 0.1-10 mol / L, preferably 0.5-5 mol / L; and the concentration of carbon dots in the carbon dot solution is 1-1000 mg / L, preferably 10-500 mg / L.

[0032] According to the present invention, in step (2), the weight ratio of the iron source, the polyhydroxy aliphatic compound, and the carbon dot solution containing an organic base can vary within a wide range. In one specific embodiment of the present invention, in step (2), the weight ratio of the iron source, the polyhydroxy aliphatic compound, and the carbon dot solution containing an organic base is 1:(0.1-10):(10-200); preferably, the weight ratio of the iron source, the polyhydroxy aliphatic compound, and the carbon dot solution is 1:(0.2-5):(20-150).

[0033] According to the present invention, the hydrothermal reaction is well known to those skilled in the art, and the hydrothermal reaction is carried out in a pressure-resistant sealed container, which can be a high-pressure reactor with a polytetrafluoroethylene liner. In a specific embodiment of the present invention, in step (3), the conditions of the hydrothermal reaction include: a temperature of 120-180°C and a time of 12-36 hours. The present invention does not specifically limit the range of reaction pressure; for example, it can be an applied pressure or an autogenous pressure.

[0034] In one specific embodiment of the present invention, step (2) includes: first mixing the iron source with the polyhydroxy aliphatic compound, then mixing the resulting mixture with the carbon dot solution to obtain a liquid mixture; the temperature of the first mixing is 10-95℃ and the time is 1-10 min; the temperature of the second mixing is 20-60℃ and the time is 5-30 min.

[0035] According to the present invention, the silicon source is an organosilicon source and / or an inorganic silicon source. In one specific embodiment of the present invention, the organosilicon source is tetramethyl silicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, or dimethoxydiethoxysilane, or a combination of two or three thereof; the inorganic silicon source is silica sol and / or silica gel.

[0036] In one specific embodiment of the present invention, the iron source includes one or more of ferric nitrate, ferric chloride, ferric sulfate, ferric phosphate, and ferric acetate, preferably ferric nitrate.

[0037] In one specific embodiment of the present invention, the polyhydroxy aliphatic compound includes one or more of glycerol, ethylene glycol, propylene glycol, hexanediol and cyclohexanediol, preferably ethylene glycol.

[0038] According to the present invention, the organic base is selected from quaternary ammonium bases, aliphatic amines, or alkanolamines, or a combination of two or three of them. In one specific embodiment of the present invention, the general formula of the quaternary ammonium base is (R 1 )4NOH, where R 1 It can be at least one of a straight-chain alkyl group having 1-4 carbon atoms and a branched alkyl group having 3-4 carbon atoms. Preferably, the quaternary ammonium base compound is tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, or a combination of two or three of them. The general formula of the aliphatic amine compound is R. 2 (NH2) n , where R 2 It can be an alkyl group or an alkylene group with 1-6 carbon atoms, where n is an integer of 1 or 2. Preferably, the aliphatic amine compound is ethylamine, n-butylamine, butanediamine, or hexamethylenediamine, or a combination of two or three of them. The general formula for alcohol amine compounds is (HOR... 3 ) m NH (3-m) , where R 3 It can be at least one of alkyl groups having 1-4 carbon atoms and alkylene groups having 3-4 carbon atoms, where m is 1, 2, or 3. Preferably, the alkanolamine compound is selected from monoethanolamine, diethanolamine, or triethanolamine, or a combination of two or three of them.

[0039] In one specific embodiment of the present invention, in step (1), the electrolysis voltage is 5-25V and the time is 2-5 days.

[0040] The second aspect of the present invention provides an iron-containing porous nanomaterial prepared by the method provided in the first aspect of the present invention.

[0041] The iron-containing porous nanomaterials of the present invention have good particle size uniformity and uniform iron distribution, which is conducive to the diffusion of reactants and products, and is particularly beneficial to further improving the selectivity of the target product.

[0042] In one specific embodiment of the present invention, the iron content of the iron-containing porous nanomaterial, calculated as Fe2O3, is 0.1-5% by weight, preferably 0.5-2.5% by weight; the distribution deviation of iron element inside and on the surface of the iron-containing porous nanomaterial particles is not greater than 50%, preferably not greater than 30%; the average particle size of the iron-containing porous nanomaterial is 50-200 nm, preferably 80-150 nm.

[0043] The third aspect of this invention provides the application of the iron-containing porous nanomaterials provided in the second aspect of this invention in the preparation of phenol by N2O oxidation of benzene.

[0044] In one specific embodiment of the present invention, the conditions for preparing phenol by oxidizing benzene with N2O include: a temperature of 80-250°C, a pressure of 0.1-3 MPa, a time of 1-24 hours, a molar ratio of N2O to benzene of (1-10):1, and an amount of iron-containing porous nanomaterial of 1-10 g relative to 100 g of benzene. Preferably, the temperature is 100-200°C, the pressure is 0.5-2 MPa, the time is 2-12 hours, the molar ratio of N2O to benzene is (1-5):1, and the amount of iron-containing porous nanomaterial of 2-6 g relative to 100 g of benzene.

[0045] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0046] Unless otherwise specified, the reagents used in the following examples and comparative examples of this invention are all commercially available analytical grade reagents.

[0047] Example 1

[0048] (1) Add 25g of tetraethyl orthosilicate and an appropriate amount of tetrapropylammonium hydroxide aqueous solution to a 1000mL beaker as electrolyte. Place the anode graphite rod (8mm in diameter and 30cm in length) and the cathode graphite rod (8mm in diameter and 30cm in length) in the beaker, keeping the distance between the anode graphite rod and the cathode rod at 8cm. Connect the anode graphite rod to the positive terminal of the DC power supply and the cathode rod to the negative terminal of the DC power supply. Apply a voltage of 15V and electrolyze for 4 days to obtain a carbon point solution. The concentration of the carbon point solution is 40mg / L, the concentration of tetrapropylammonium hydroxide in the aqueous solution of organic base is 200mmol / L, and the concentration of tetraethyl orthosilicate is 1.2mol / L.

[0049] (2) First, mix 1g of ferric nitrate and 1g of ethylene glycol evenly, then add 60g of the carbon dot solution obtained in step (1) and mix evenly to obtain a mixture; wherein, the weight ratio of ferric nitrate, ethylene glycol and carbon dot solution is 1:1:60.

[0050] (3) The mixture was placed in a stainless steel reactor and kept at a constant temperature of 170°C for 36 hours. The solid obtained by hydrothermal reaction was filtered, washed with deionized water, dried at 110°C for 1 hour, and calcined in air at 550°C for 3 hours to obtain iron-containing porous nanomaterial A1.

[0051] Example 2

[0052] Iron-containing porous nanomaterial A2 was prepared using the same method as in Example 1. The only difference was that in step (2), 1g of ferric chloride and 6g of ethylene glycol were mixed first, and then 30g of carbon dot solution was added and mixed evenly to obtain a mixture. The weight ratio of ferric chloride, ethylene glycol and carbon dot solution was 1:6:30.

[0053] Example 3

[0054] Iron-containing porous nanomaterial A3 was prepared using the same method as in Example 1, except that in step (3), the hydrothermal reaction temperature was 200°C and the time was 2 hours.

[0055] Example 4

[0056] Iron-containing porous nanomaterial A4 was prepared using the same method as in Example 1. The only difference was that in step (2), instead of stepwise mixing, the materials were directly mixed evenly to obtain a mixture.

[0057] Comparative Example 1

[0058] Iron-containing porous nanomaterial DA1 was prepared using the same method as in Example 1, except that ethylene glycol was not added in step (2).

[0059] Comparative Example 2

[0060] Nanomaterial DA2 was prepared using the same method as in Example 1, except that in step (1), no silicon source was added to the electrolyte; in step (2), an equal amount of tetraethyl orthosilicate as in step (1) of Example 1 was mixed with 1g of ethylene glycol and 1g of ferric nitrate, and then mixed with 60g of carbon dot solution to obtain a mixture, wherein the weight ratio of ferric nitrate, ethylene glycol and carbon dot solution was 1:1:60.

[0061] Comparative Example 3

[0062] Nanomaterial DA3 was prepared using the same method as in Example 1, except that no organic base was added to the electrolyte in step (1); in step (2), ethylene glycol and iron source were mixed and then tetrapropylammonium hydroxide of the same amount as in step (2) of Example 1 was added and mixed with carbon dot solution to obtain a mixture.

[0063] Comparative Example 4

[0064] The porous nanomaterial DA4 was prepared using the same method as in Example 1, except that no iron source was added in step (2).

[0065] Test case

[0066] Five g of the nanomaterials synthesized in the above examples and comparative examples were placed into a 250 ml slurry bed high-pressure reactor as catalysts. 100 g of benzene was added, and then N2O was introduced into the reactor at a molar ratio of benzene:N2O = 1:2. The reactor was then sealed and reacted at 120 °C for 4 hours with stirring to obtain the oxidation product.

[0067] Oxidation products were analyzed using gas chromatography (GC: Agilent, 7890A) and gas chromatography-mass spectrometry (GC-MS: ThermoFisher Trace ISQ). GC conditions were as follows: nitrogen carrier gas; programmed temperature rise: 60℃ for 1 minute, 15℃ / minute, 180℃ for 15 minutes; split ratio: 10:1; injector temperature: 300℃; detector temperature: 300℃. The test results are shown in Table 1.

[0068] The content of iron in the interior and surface of iron-containing porous nanomaterials was determined by XPS. The surface iron content was directly measured by XPS, while the interior iron content was measured by XPS after ion sputtering etching to 50 nm.

[0069] The following formulas are used to calculate the distribution deviation of iron element inside and on the surface of the iron-containing porous nanomaterial particles, the raw material conversion rate, and the target product selectivity:

[0070] Iron distribution deviation = (surface iron content - internal iron content) / surface iron content × 100%;

[0071] Benzene conversion rate = (Amount of benzene added before reaction - Amount of benzene remaining after reaction) / Amount of benzene added before reaction × 100%;

[0072] The selectivity of phenol = the amount of phenol produced after the reaction / (the amount of benzene added before the reaction - the amount of benzene remaining after the reaction) × 100%.

[0073] Table 1

[0074]

[0075] As can be seen from the data in Table 1, the iron-containing porous nanomaterials prepared by the method of the present invention have good catalytic performance in the preparation of phenol by N2O oxidation of benzene.

[0076] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0077] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0078] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing iron-containing porous nanomaterials, the method comprising: (1) The first conductive material and the second conductive material, which are respectively connected to the positive and negative terminals of the DC power supply, are placed in an aqueous solution of organic base containing silicon source and electrolyzed for 1-8 days at a voltage of 1-36V to obtain a carbon dot solution containing silicon source and organic base; wherein, the first conductive material is a graphite molded body. (2) The iron source, the polyhydroxy aliphatic compound and the carbon point solution containing the silicon source and the organic base are directly mixed to obtain a liquid mixture; (3) Place the liquid mixture in a pressure-resistant and heat-resistant sealed container and carry out a hydrothermal reaction at 100-200℃ for 6-48 hours, and then take out the solid.

2. The method according to claim 1, wherein, In step (1), the concentration of the organic base in the aqueous solution containing the silicon source is 10-2500 mmol / L; the concentration of the silicon source is 0.1-10 mol / L. The concentration of carbon dots in the carbon dot solution is 1-1000 mg / L.

3. The method according to claim 2, wherein, In step (1), the concentration of the organic base in the aqueous solution containing the silicon source is 50-1500 mmol / L; the concentration of the silicon source is 0.5-5 mol / L. The concentration of carbon dots in the carbon dot solution is 10-500 mg / L.

4. The method according to claim 1, wherein, In step (2), the weight ratio of the iron source, the polyhydroxy aliphatic compound and the carbon dot solution is 1:(0.1-10):(10-200).

5. The method according to claim 1, wherein, The weight ratio of the iron source, the polyhydroxy aliphatic compound, and the carbon dot solution is 1:(0.2-5):(20-150).

6. The method according to claim 1, wherein, In step (3), the temperature of the hydrothermal reaction is 120-180℃ and the time is 12-36 hours.

7. The method according to claim 1, wherein, Step (2) includes: first mixing the iron source with the polyhydroxy aliphatic compound, then mixing the resulting mixture with the carbon dot solution to obtain a liquid mixture; The temperature of the first mixing is 10-95℃ and the time is 1-10 min; the temperature of the second mixing is 20-60℃ and the time is 5-30 min.

8. The method according to claim 1, wherein, The silicon source is an organosilicon source and / or an inorganic silicon source; the organosilicon source is tetramethyl silicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, or dimethoxydiethoxysilane, or a combination of two or three of them; the inorganic silicon source is silica sol and / or silica gel. The iron source includes one or more of ferric nitrate, ferric chloride, ferric sulfate, ferric phosphate, and ferric acetate; The polyhydroxy aliphatic compound includes one or more of ethylene glycol, glycerol, propylene glycol, hexanediol, and cyclohexanediol; The organic base is selected from quaternary ammonium bases, aliphatic amines, or alkanolamines, or a combination of two or three of them; wherein the quaternary ammonium base is tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, or a combination of two or three of them; the aliphatic amine is ethylamine, n-butylamine, butanediamine, or hexamethylenediamine, or a combination of two or three of them; and the alkanolamine is selected from monoethanolamine, diethanolamine, or triethanolamine, or a combination of two or three of them.

9. The method according to claim 1, wherein, The iron source is ferric nitrate; the polyhydroxy aliphatic compound is ethylene glycol.

10. The method according to claim 1, wherein, In step (1), the electrolysis voltage is 5-25V and the time is 2-5 days.

11. The iron-containing porous nanomaterial prepared by the method according to any one of claims 1-10.

12. The iron-containing porous nanomaterial according to claim 11, wherein, The iron content of the iron-containing porous nanomaterial, calculated as Fe2O3, is 0.1-5% by weight; the distribution deviation of iron element inside and on the surface of the iron-containing porous nanomaterial particles is no more than 50%; the average particle size of the iron-containing porous nanomaterial is 50-200 nm.

13. The iron-containing porous nanomaterial according to claim 11, wherein, The iron content of the iron-containing porous nanomaterial, calculated as Fe2O3, is 0.5-2.5% by weight; the distribution deviation of iron element inside and on the surface of the iron-containing porous nanomaterial particles is no more than 30%; the average particle size of the iron-containing porous nanomaterial is 80-150 nm.

14. The application of the iron-containing porous nanomaterial according to any one of claims 11-13 in the preparation of phenol by N2O oxidation of benzene.

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