A nanomaterial, a preparation method and application thereof

Abstract

The application relates to a nanomaterial and a preparation method and application thereof, and the method comprises the following steps: S1, connecting a graphite forming body and a conductive object connected with a positive electrode and a negative electrode of a direct current power supply respectively, and then placing the graphite forming body and the conductive object in an electrolyte containing an organic alkali, electrolyzing at a voltage of 25-50 V for 1-10 days to obtain a first mixture containing carbon dots and the organic alkali; S2, mixing a silicon source and an active center source, and mixing the obtained mixture with the first mixture to obtain a second mixture; S3, performing hydrothermal reaction on the second mixture, cooling the obtained reaction product, performing solid-liquid separation on the reaction product, obtaining a solid-phase product and a liquid-phase product, and roasting the solid-phase product to obtain the nanomaterial; and S4, contacting the liquid-phase product with a porous material, and the pore size of the porous material is larger than that of the nanomaterial. The nanomaterial prepared by the method has relatively optimal catalytic reaction activity, and wastewater generated in the preparation process can be directly discharged.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of nanomaterial and its preparation method and application. BACKGROUND

[0002] Carbon nanomaterial is similar to ordinary nanomaterial, but has quantum size effect, small size effect and macroscopic quantum tunneling effect and other special properties in optics, electricity, magnetism etc. Now carbon nanoparticles with size less than 10nm are called carbon quantum dots, i.e. carbon dots, which are new small size carbon nanomaterial. Due to its excellent fluorescent properties, carbon quantum dots are also called fluorescent carbon quantum dots (CDs). Compared with organic dyes and traditional semiconductor quantum dots (QDs), CDs have unique optical and electrical properties in addition to high stability, good water solubility and good biocompatibility. Therefore, more and more people begin to study CDs, and CDs can also be applied to energy problems, environmental protection, photovoltaic devices and other related fields. The research on green catalytic oxidation materials started in the early 1980s of last century. Green catalytic oxidation materials not only have catalytic oxidation effect, but also have shape selection and better stability. However, the production of green catalytic oxidation materials contains organic template agent in the filtered waste liquid, and the COD content is 5000-100000 mg / L, which is difficult to be biologically treated. It cannot be directly discharged into the conventional biochemical wastewater treatment unit, and needs to be diluted with a large amount of fresh water before being discharged into the biochemical wastewater treatment unit. This greatly limits the production of green catalytic oxidation materials, and there is an urgent need for new green catalytic oxidation material production technology that can be directly discharged. SUMMARY

[0003] The purpose of the present application is to provide a kind of nanomaterial and its preparation method and application. The nanomaterial prepared by the method has not only better catalytic reaction activity, but also the wastewater produced in the preparation process can be directly discharged.

[0004] To achieve the above purpose, the first aspect of the present application provides a method for preparing nanomaterial, which comprises:

[0005] S1, connect the graphite shaped body and the conductive material connected with the positive and negative poles of the direct current power source respectively, and then place them in the electrolyte containing organic alkali. First electrolysis at a voltage of 25-50V for 1-10 days to obtain a first mixture containing carbon dots and organic alkali;

[0006] S2, mix the silicon source and the active center source at 5-50℃ for 0.1-12 hours, and then mix the obtained mixture with the first mixture at 20-90℃ for 1-24 hours to obtain a second mixture;

[0007] S3, subjecting the second mixture to hydrothermal reaction at 120-200℃ for 6-96 hours in a heat-resistant closed container, allowing the obtained reaction product to cool, and then performing solid-liquid separation to obtain a solid-phase product and a liquid-phase product, and subjecting the solid-phase product to calcination to obtain a nanomaterial;

[0008] S4, contacting the liquid-phase product with a porous material, the porous material having a pore size larger than that of the nanomaterial.

[0009] Optionally, in step S1, the content of carbon dots in the first mixture is 10-1000 mg / L, and the content of the organic base is 20-1500 mmol / L.

[0010] Optionally, in step S2, the silicon source and the active center source are subjected to first mixing at 10-45℃ for 1-8 hours, and the obtained mixture is subjected to second mixing with the first mixture at 25-80℃ for 2-10 hours.

[0011] The weight ratio of the use amount of the first mixture, the silicon source and the active center source is (20-2000) : 100 : (0.1-10).

[0012] Optionally, in step S3, the calcination of the solid-phase product comprises: sequentially performing first calcination and second calcination on the solid-phase product.

[0013] The temperature of the first calcination is 250-450℃, the time is 1-24 hours, and the atmosphere is inert; the temperature of the second calcination is 460-800℃, the time is 1-12 hours, and the atmosphere is air.

[0014] Optionally, in step S4, the weight ratio of the use amount of the liquid-phase product and the porous material is 100 : (1-50).

[0015] Optionally, in step S4, the contacting conditions include: temperature of 15-100℃, and time of 10-600 min.

[0016] Optionally, the organic base is selected from one or more of urea, quaternary ammonium base compounds, fatty amine compounds and alcohol amine compounds.

[0017] The quaternary ammonium base compound is tetraethylammonium hydroxide, tetrapropylammonium hydroxide or tetrabutylammonium hydroxide, or a combination of two or three thereof; the fatty amine compound is ethylamine, n-butylamine, butanediamine or hexanediamine, or a combination of two or three thereof; and the alcohol amine compound is monoethanolamine, diethanolamine or triethanolamine, or a combination of two or three thereof.

[0018] The silicon source is an organic silicon source and / or an inorganic silicon source.

[0019] the organic silicon source is selected from tetramethyl silicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate or dimethoxydiethoxysilane, or is a combination of two or three of them; the inorganic silicon source is selected from silica sol and / or silica gel;

[0020] the active center source is selected from one or several of a titanium source, an iron source, a chromium source and a vanadium source;

[0021] Preferably, the active center source is selected from one or several of ferric chloride, ferric nitrate, ferric sulfate, titanium chloride, titanium sulfate, vanadate, chromate, ferrate, titanate, titanate ester, iron naphthenate and chromium acetylacetonate;

[0022] the porous material is selected from one or several of Y molecular sieve, β molecular sieve, mesoporous molecular sieve, carbon nanotube and activated carbon.

[0023] The second aspect of the present application provides a nanomaterial prepared by the method provided in the first aspect of the present application.

[0024] Optionally, the nanomaterial has a pore size of 0.5-0.7 nm.

[0025] The third aspect of the present application provides an application of the nanomaterial provided in the second aspect of the present application in the oxidation of phenol to produce diphenol.

[0026] By the above technical solution, the method of the present application is simple and suitable for industrial production. The nanomaterial prepared by the method has a uniform distribution of active centers, has a relatively optimal catalytic reaction activity, and the wastewater generated in the preparation of the nanomaterial can be directly discharged.

[0027] Other features and advantages of the present application will be described in detail in the subsequent specific implementation manner part. DETAILED DESCRIPTION

[0028] The specific implementation manner of the present application is described in detail below. It should be understood that the specific implementation manner described herein is only used to illustrate and explain the present application, and is not used to limit the present application.

[0029] The first aspect of the present application provides a method for preparing a nanomaterial, which comprises:

[0030] S1, connecting a graphite forming body and a conductive object connected with the positive and negative poles of a direct current power supply respectively, and then placing them in an electrolyte containing an organic base, and electrolyzing at a voltage of 25-50 V for 1-10 days to obtain a first mixture containing carbon dots and an organic base;

[0031] S2, mixing the silicon source and the active center source at 5-50℃ for 0.1-12 hours to obtain a first mixture, and mixing the obtained mixture with the first mixture at 20-90℃ for 1-24 hours to obtain a second mixture;

[0032] S3, hydrothermally reacting the second mixture in a heat-resistant closed container at 120-200℃ for 6-96 hours, and then solid-liquid separating the obtained reaction product to obtain a solid phase product and a liquid phase product, and calcining the solid phase product to obtain the nanomaterial;

[0033] S4, contacting the liquid phase product with a porous material, the porous material having a pore size larger than that of the nanomaterial.

[0034] The pore size of the porous material and the nanomaterial in the method of the present application refers to the size of the pore opening of the pores of the material at the outer surface, i.e. the size of the pore opening of the pores exposed on the outer surface of the material, which is generally measured by the maximum distance between any two points of the pore opening, and is known to those skilled in the art. The pore size of the porous material and the nanomaterial prepared by the method of the present application can be calculated by XRD method or characterized by high-resolution electron microscopy. The nanomaterial prepared by the method of the present application has a more uniform distribution of active centers, good catalytic reaction activity, and the wastewater generated during the preparation process can be directly discharged, which is suitable for industrial production.

[0035] According to the present application, in step S2, the first mixing of the silicon source and the active center source at 5-50℃ for 0.1-12 hours refers to mixing the silicon source and the active center source to form a slurry, and then mixing the slurry at 5-50℃ for 0.1-12 hours.

[0036] In one specific embodiment of the present application, the electrolyte is well known to those skilled in the art, such as an aqueous solution. The amount of electrolyte is not specifically limited, and can be selected according to actual needs, for example, according to the size of the first conductive object and the second conductive object and the electrolysis conditions.

[0037] According to the present application, the graphite shaped body can be a graphite rod or a graphite plate, and the size of the graphite shaped body and the conductive object is not specifically limited, preferably, the size of the graphite shaped body matches the size of the conductive object, and the size of the graphite shaped body can vary in a large range, for example, when the graphite shaped body is a graphite rod, the diameter of the graphite rod can be 2-20 mm, and the length can be 2-100 cm, wherein the length refers to the axial length of the graphite rod; when the graphite shaped body is a graphite plate, the length of the graphite plate can be 5-100 cm, the width can be 1-100 cm, and the thickness can be 0.01-10 mm. The type and shape of the conductive object are not specifically limited, and can be any conductive material, for example, can be iron, copper, graphite, etc., preferably graphite, and the shape can be rod-shaped, plate-shaped, etc., preferably rod-shaped. When electrolysis is performed, a certain distance needs to be maintained between the graphite shaped body and the conductive object, for example, can be 3-10 cm.

[0038] In one specific embodiment of the present application, in step S1, the content of carbon dots in the first mixture is 10-1000 mg / L, preferably 50-500 mg / L, and more preferably 50-130 mg / L, and the content of the organic base is 20-1500 mmol / L, preferably 100-1000 mmol / L. The content of carbon dots in the first mixture can be measured by methods such as evaporative drying and weighing.

[0039] In a preferred specific embodiment of the present application, in step S2, the silicon source and the active center source are mixed at 15-45°C for 1-8 hours, and the obtained mixture is mixed with the first mixture at 25-80°C for 2-10 hours.

[0040] In one specific embodiment of the present application, in step S2, the weight ratio of the use amount of the first mixture, the silicon source and the active center source can vary in a large range, for example, can be (20-2000) : 100 : (0.1-10), preferably (100-1500) : 100 : (0.2-6), and further preferably (200-1000) : 100 : (0.5-3). The nano-material prepared in the above use amount ratio range has a more optimal active center distribution, which is beneficial to further improve its catalytic performance.

[0041] In one specific embodiment of the present application, in step S3, the heat-resistant sealed container is well known to those skilled in the art, for example, the reaction is carried out in a polytetrafluoroethylene reaction kettle. The pressure of the hydrothermal reaction process is not specifically limited, and can be the autogenous pressure of the system, or can be carried out under an additional applied pressure, preferably, the hydrothermal reaction process is carried out under autogenous pressure (usually in a sealed container). Preferably, the hydrothermal reaction is carried out at a temperature of 150-200°C for 10-90 hours.

[0042] In a preferred embodiment, the solid phase product obtained from the hydrothermal reaction is washed, dried and then calcined. The washing solution can be deionized water, ethanol or the like, and the drying can be performed in a constant temperature drying oven, with conditions including a temperature of 100-200°C and a time of 1-48 hours.

[0043] In an embodiment of the present application, in step S3, the calcination of the solid phase product includes first calcination and second calcination in sequence. The first calcination can be performed at a temperature of 250-450°C for a time of 1-24 hours in an inert atmosphere. The second calcination can be performed at a temperature of 460-800°C for a time of 1-12 hours in an air atmosphere. The inert atmosphere is well known to those skilled in the art, for example, it can be an oxygen-free atmosphere, and the gas in the inert atmosphere can be one or more of helium, argon, nitrogen and carbon dioxide. The calcination can be performed in a muffle furnace or a tube furnace, and other calcination methods are not described here. The two-stage calcination of the solid phase product can further improve the catalytic activity of the nanomaterial prepared.

[0044] In an embodiment of the present application, in step S4, the weight ratio of the liquid phase product to the porous material can vary in a wide range, for example, it can be 100:(1-50), and preferably 100:(5-27). In the method of the present application, the liquid phase product is also contacted with the porous material to remove organic ammonia nitrogen and other pollutants in the liquid phase product, achieving clean discharge of wastewater in the preparation of nanomaterials, which is conducive to the clean industrial application of the method of the present application.

[0045] In an embodiment of the present application, in step S4, the contacting conditions can include a temperature of 15-100°C and a time of 10-600 minutes, and preferably a temperature of 50-90°C and a time of 60-500 minutes. Preferably, the COD content of the liquid product obtained after the liquid phase product and the porous material are contacted is less than 50 ppm.

[0046] According to the present application, the organic base is selected from one or more of urea, quaternary ammonium base compounds, fatty amine compounds and alcohol amine compounds. In an embodiment, the molecular formula of the quaternary ammonium base compound can be (R 1 )4NOH, wherein R 1at least one of a C1-C4 linear alkyl group and a C3-C4 branched alkyl group, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, or methylallyl. Preferably, the quaternary ammonium base compound can be tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, or a combination of two or three thereof.

[0047] The molecular formula of the fatty amine compound can be R 2 (NH2) n wherein R 2 may be at least one of a C1-C6 linear alkyl group and a C3-C6 branched alkyl group, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, n-pentyl, or n-hexyl, R 2 may also be a C1-C6 alkylene group, such as methylene, ethylene, n-propylene, n-butylene, or n-hexylene, and n is an integer of 1 or 2. Preferably, the fatty amine compound can be ethylamine, n-butylamine, butanediamine, or hexanediamine, or a combination of two or three thereof.

[0048] The molecular formula of the alcohol amine compound can be (HOR 3 ) m NH (3-m) wherein R 3 may be a C1-C4 alkyl group, and m is an integer of 1, 2, or 3. Preferably, the alcohol amine compound can be monoethanolamine, diethanolamine, or triethanolamine, or a combination of two or three thereof.

[0049] In one embodiment of the present application, the silicon source is an organic silicon source and / or an inorganic silicon source. The organic silicon source can include, but is not limited to, tetramethyl silicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, or dimethoxydiethoxysilane, or a combination of two or three thereof; and the inorganic silicon source can include, but is not limited to, silica sol and / or silica gel.

[0050] According to the present application, the active center source can be selected from one or more of a titanium source, an iron source, a chromium source, and a vanadium source, preferably a titanium source. In one embodiment of the present application, the active metal source is an inorganic active metal source, which can be an inorganic salt containing the active metal, such as one or more of iron chloride, iron nitrate, iron sulfate, titanium chloride, titanium sulfate, vanadate, chromate, ferrate, and titanate; in another embodiment, the active metal source can be an organic acid salt containing the active metal and / or an ester containing the active metal, which can include, but is not limited to, one or more of titanate (such as tetrabutyl titanate, tetrapropyl titanate), iron naphthenate, and chromium acetylacetonate.

[0051] In one embodiment of the present application, the porous material is selected from one or more of Y molecular sieve, beta molecular sieve, mesoporous molecular sieve, carbon nanotube and activated carbon.

[0052] The present application provides a nanomaterial prepared by the method of the first aspect of the present application.

[0053] In one embodiment of the present application, the nanomaterial has a pore size of 0.5-0.7 nm.

[0054] The present application provides the use of the nanomaterial of the second aspect of the present application in the oxidation of phenol to produce diphenol.

[0055] The present application will be further described by way of examples, but the present application is not limited in any way by the examples.

[0056] The reagents used in the present application are commercially available analytical reagents.

[0057] Example 1

[0058] S1, 1000 mL of distilled water was added to a beaker, and an anode graphite rod (diameter 8 mm, length 50 cm) and a cathode graphite rod (diameter 8 mm, length 50 cm) were placed in the beaker, keeping the distance between the anode graphite rod and the cathode rod at 5 cm, connecting the anode graphite rod to the positive pole of a direct current power supply and the cathode rod to the negative pole of the direct current power supply, then adding tetrapropylammonium hydroxide to the electrolyte, electrolyzing at a voltage of 25 V for 6 days to obtain a first mixture containing organic base and carbon dots; the concentration of carbon dots in the first mixture was 130 mg / L, and the concentration of tetrapropylammonium hydroxide was 400 mmol / L;

[0059] S2, 1.7 g of tetraisopropyl titanate was mixed with 25 g of tetraethyl orthosilicate at 15°C for 6 hours, then the obtained mixture was added to 50 mL of the first mixture and mixed at 80°C for 3 hours to obtain a second mixture; wherein the weight ratio of the first mixture, the silicon source and tetraisopropyl titanate is 200:100:6.8;

[0060] S3, the second mixture was transferred to a stainless steel reaction kettle, and hydrothermal reaction was carried out at 170°C for 3 days to obtain a hydrothermal reaction product; the hydrothermal reaction product was filtered to obtain a solid phase product and a liquid phase product, the solid phase product was washed with water, and dried at 110°C for 3 hours, then first calcination was carried out at 350°C for 12 hours in a nitrogen atmosphere, and then second calcination was carried out at 600°C for 2 hours in an air atmosphere to obtain a nanomaterial A, which has a pore size of 0.55 nm.

[0061] S4, the liquid phase product is contacted with NaY molecular sieve (pore size is 0.74 nm) at 50℃ for 6h, the weight ratio of the liquid phase product to NaY molecular sieve is 15:4, and the COD of the clear liquid after contact is less than 50ppm, which can be directly discharged.

[0062] Example 2

[0063] S1, 1000mL of distilled water is added to a beaker, an anode graphite rod (diameter 8mm, length 50cm) and a cathode graphite rod (diameter 8mm, length 50cm) are placed in it, the distance between the anode graphite rod and the cathode rod is kept at 5cm, the anode graphite rod is connected with the positive electrode of a direct current power supply and the cathode rod is connected with the negative electrode of the direct current power supply, then triethanolamine is added to the electrolyte, and electrolysis is carried out at a voltage of 45V for 4 days to obtain a first mixture containing organic base and carbon dots; the concentration of carbon dots in the first mixture is 110mg / L, and the concentration of triethanolamine is 1200mmol / L;

[0064] S2, 1.1g of ammonium vanadate is mixed with 25g of tetraethyl orthosilicate at 50℃ for 1h, then the obtained mixture is added to 24mL of the first mixture and mixed at 80℃ for 3h to obtain a second mixture; the weight ratio of the amount of the first mixture, tetraethyl orthosilicate and ammonium vanadate is 96:100:4.4;

[0065] S3, the second mixture is transferred to a stainless steel reaction kettle, and hydrothermal reaction is carried out at 140℃ for 5 days to obtain a hydrothermal reaction product; the hydrothermal reaction product is filtered to obtain a solid phase product and a liquid phase product, the solid phase product is washed with water and dried at 120℃ for 2h, then first calcination is carried out at 280℃ for 10h in a carbon dioxide atmosphere, and then second calcination is carried out at 700℃ for 1h in an air atmosphere to obtain a nanomaterial B, and the pore size of the nanomaterial B is 0.56nm.

[0066] S4, the liquid phase product is contacted with NaY molecular sieve (pore size is 0.74 nm) at 25℃ for 6h, the weight ratio of the liquid phase product to NaY molecular sieve is 10:1, and the COD of the clear liquid after contact is less than 50ppm, which can be directly discharged.

[0067] Example 3

[0068] S1, 1000 mL of distilled water was added to a beaker, an anode graphite rod (diameter 8 mm, length 50 cm) and a cathode graphite rod (diameter 8 mm, length 50 cm) were placed therein, the distance between the anode graphite rod and the cathode rod was kept at 5 cm, the anode graphite rod was connected to the positive electrode of a direct current power supply and the cathode rod was connected to the negative electrode of the direct current power supply, then ethylenediamine was added to the electrolyte, electrolysis was carried out at a voltage of 50 V for 4 days to obtain a first mixture containing organic base and carbon dots; the concentration of carbon dots in the first mixture was 90 mg / L, and the concentration of ethylenediamine was 800 mmol / L;

[0069] S2, 3.5 g of ferric chloride was mixed with 25 g of tetraethyl orthosilicate at 25℃ for 12 hours, then the obtained mixture was added to 100 mL of the first mixture and mixed at 90℃ for 2 hours to obtain a second mixture; the weight ratio of the dosages of the first mixture, tetraethyl orthosilicate and ferric chloride was 400:100:14;

[0070] S3, the second mixture was transferred to a stainless steel reaction kettle, and hydrothermal reaction was carried out at 140℃ for 5 days to obtain a hydrothermal reaction product; the hydrothermal reaction product was filtered to obtain a solid phase product and a liquid phase product, the solid phase product was washed with water and dried at 110℃ for 2 hours, and then the first calcination was carried out at 280℃ for 10 hours in a carbon dioxide atmosphere, and then the second calcination was carried out at 700℃ for 1 hour in an air atmosphere, to obtain a nanomaterial C, the pore size of which was 0.55 nm.

[0071] S4, the liquid phase product was contacted with NaY molecular sieve (pore size 0.74 nm) at 80℃ for 3h, the weight ratio of the liquid phase product to the NaY molecular sieve was 25:1, and the COD of the clear liquid after the contact was less than 50 ppm, which could be directly discharged.

[0072] Example 4

[0073] S1, 5000 mL of distilled water was added to a beaker, an anode graphite rod (diameter 8 mm, length 50 cm) and a cathode graphite rod (diameter 8 mm, length 50 cm) were placed therein, the distance between the anode graphite rod and the cathode rod was kept at 5 cm, the anode graphite rod was connected to the positive electrode of a direct current power supply and the cathode rod was connected to the negative electrode of the direct current power supply, then tetrabutylammonium hydroxide was added to the electrolyte, electrolysis was carried out at a voltage of 20 V for 4 days to obtain a first mixture containing organic base and carbon dots; the concentration of carbon dots in the first mixture was 125 mg / L, and the concentration of tetrabutylammonium hydroxide was 1 mol / L;

[0074] S2, 1.7 g of tetrabutyl titanate was mixed with 25 g of tetraethyl orthosilicate at 15 °C for 5 hours, and the obtained mixture was added into 50 mL of the first mixture to mix at 60 °C for 6 hours to obtain a second mixture; the weight ratio of the first mixture, the tetraethyl orthosilicate and the tetrabutyl titanate was 200:100:6.8;

[0075] S3, the second mixture was transferred into a stainless steel reaction kettle to perform hydrothermal reaction at 140 °C for 5 days to obtain a hydrothermal reaction product; the hydrothermal reaction product was filtered to obtain a solid phase product and a liquid phase product, the solid phase product was washed with water to obtain a washed solid phase product, and the washed solid phase product was dried at 110 °C for 2 hours, and then was subjected to first calcination in a carbon dioxide atmosphere at 280 °C for 10 hours, and then was subjected to second calcination in an air atmosphere at 700 °C for 1 hour to obtain a nanomaterial D, the pore size of which was 0.58 nm.

[0076] S3, the liquid phase product was contacted with Naβ molecular sieve (the pore size of which was 0.65 nm) at 40 °C for 12 hours, the weight ratio of the liquid phase product and the Naβ molecular sieve was 50:1, and the COD of the clear solution after the contacting was less than 50 ppm, which could be directly discharged.

[0077] Example 5

[0078] The nanomaterial E was prepared by the same method as that in Example 1, except that in step S2, 4 g of tetraisopropyl titanate was mixed with 25 g of tetraethyl orthosilicate at 20 °C for 1 hour, and the obtained mixture was added into 500 mL of the first mixture to obtain a second mixture; the weight ratio of the first mixture, the tetraethyl orthosilicate and the tetraisopropyl titanate was 2000:100:16. The pore size of the nanomaterial E was 0.55 nm.

[0079] Example 6

[0080] The nanomaterial F was prepared by the same method as that in Example 1, except that in step S1, the voltage of the electrolysis was 25 V, and the time was 3 days. The concentration of the carbon dots in the obtained first mixture was 70 mg / L, and the concentration of the tetrapropyl ammonium hydroxide was 450 mmol / L. The pore size of the nanomaterial F was 0.55 nm.

[0081] Example 7

[0082] The nanomaterial G was prepared by the same method as that in Example 1, except that in step S2, 1.7 g of tetraisopropyl titanate was mixed with 25 g of tetraethyl orthosilicate at 10 °C for 6 hours, and the obtained mixture was added into 50 mL of the first mixture to mix at 85 °C for 3 hours to obtain a second mixture.

[0083] Example 8

[0084] The nanomaterial H was prepared by the same method as in Example 1, except that in step S3, the first calcination was performed at a temperature of 250°C for 13 hours, and the second calcination was performed at a temperature of 460°C for 12 hours. The nanomaterial H has a pore size of 0.55 nm.

[0085] Comparative Example 1

[0086] The nanomaterial a was prepared by the same method as in Example 1, except that in step S1, the first mixture containing organic base and carbon dots was obtained by electrolysis at a voltage of 5V for 5 days. The concentration of carbon dots in the first mixture was 10 mg / L, and the concentration of tetrapropylammonium hydroxide was 400 mmol / L.

[0087] Comparative Example 2

[0088] The nanomaterial b was prepared by the same method as in Example 1, except that in step S1, the first mixture containing organic base and carbon dots was obtained by electrolysis at a voltage of 80V for 2 days. The concentration of carbon dots in the first mixture was 150 mg / L, and the concentration of tetrapropylammonium hydroxide was 410 mmol / L.

[0089] Comparative Example 3

[0090] The nanomaterial c was prepared by the same method as in Example 1, except that in step S1, no tetrapropylammonium hydroxide was added to the electrolyte, and the first mixture containing carbon dots was obtained by electrolysis at a voltage of 30V for 6 days. The concentration of carbon dots in the first mixture was 130 mg / L.

[0091] In step S2, 1.7 g of tetraisopropyl titanate and 25 g of tetraethyl orthosilicate were mixed at 10°C for 6 hours, and then the mixture was mixed with 50 mL of the first mixture and tetrapropylammonium hydroxide at 80°C for 3 hours to obtain a second mixture. The amount of tetrapropylammonium hydroxide used was the same as the amount of tetrapropylammonium hydroxide contained in 50 mL of the first mixture in Comparative Example 1.

[0092] Comparative Example 4

[0093] The nanomaterial d was prepared by the same method as in Example 1, except that in step S2, 1.7 g of tetraisopropyl titanate, 25 g of tetraethyl orthosilicate, and 50 mL of the first mixture were mixed at 80°C for 3 hours to obtain a second mixture.

[0094] Comparative Example 5

[0095] The nanomaterial was prepared by the same method as in Example 1, except that step S4 was omitted. The COD was greater than 8000 ppm, and the nanomaterial could not be directly discharged.

[0096] Test Example

[0097] In the following test examples, gas chromatography (GC: Agilent, 7890A) and gas chromatography-mass spectrometry (GC-MS: Thermo Fisher Trace ISQ) were used to analyze the oxidation products.

[0098] This test example illustrates the effect of the nanomaterial prepared in the examples and comparative examples on the catalytic oxidation reaction for phenol hydroxylation. The materials were mixed in a three-necked flask with a condenser at a weight ratio of nanomaterial: phenol: acetone = 1:20.0:20.0, heated to 75°C, and then 30% hydrogen peroxide was added at a molar ratio of phenol: hydrogen peroxide = 3:1 under stirring at this temperature for 2 hours, and the results are shown in Table 1.

[0099] Table 1

[0100]

[0101] As can be seen from Table 1, the nanomaterial prepared by the method of the present application has high reactivity, and can improve the conversion rate of raw materials and the selectivity of hydroquinone, especially the selectivity of p-hydroquinone, when used in the oxidation of phenol to produce hydroquinone. The preparation method is simple and easy to operate, the wastewater generated during the preparation process can be directly discharged, and is suitable for industrial production. In Comparative Example 5, the liquid phase product is not in contact with the porous material, and the COD is greater than 8000 ppm, which cannot achieve direct discharge of industrial wastewater, indirectly increasing the production cost.

[0102] The preferred embodiments of the present application are described in detail above, but the present application is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, and these simple modifications all belong to the protection scope of the present application.

[0103] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the present application will not further describe various possible combinations.

[0104] In addition, various different embodiments of the present application can also be combined in any manner, as long as they do not deviate from the technical concept of the present application, and they should also be considered as disclosed by the present application.

Claims

1. A method for preparing nanomaterials, comprising: S1, connecting a graphite forming body and a conductive material to the positive and negative poles of a direct current power source respectively, and then placing them in an electrolyte containing an organic base, and electrolyzing at a voltage of 25-50 V for 1-10 days to obtain a first mixture containing carbon dots and an organic base; S2, mixing a silicon source and an active center source at 15-45 ℃ for 1-8 hours to obtain a first mixture, and then mixing the obtained mixture with the first mixture at 25-80 ℃ for 2-10 hours to obtain a second mixture; wherein the weight ratio of the first mixture, the silicon source and the active center source is (20-2000) : 100: (0.1-10) ; S3, hydrothermally reacting the second mixture in a heat-resistant sealed container at 120-200 ℃ for 6-96 hours, and then performing solid-liquid separation on the obtained reaction product to obtain a solid phase product and a liquid phase product, and then sequentially performing first calcination and second calcination on the solid phase product to obtain nanomaterials; the first calcination is performed at a temperature of 250-450 ℃ for 1-24 hours in an inert atmosphere; the second calcination is performed at a temperature of 460-800 ℃ for 1-12 hours in an air atmosphere; S4, contacting the liquid phase product with a porous material, wherein the pore size of the porous material is larger than that of the nanomaterials; the weight ratio of the liquid phase product and the porous material is 100: (5-27), and the contacting conditions include a temperature of 50-90 ℃ and a time of 60-500 min; the porous material is selected from one or more of Y molecular sieve, β molecular sieve and mesoporous molecular sieve; the organic base is selected from one or more of urea, quaternary ammonium base compounds, fatty amine compounds and alcohol amine compounds; and the active center source is selected from one or more of titanium source, iron source, chromium source and vanadium source. In step S1, the content of carbon dots in the first mixture is 10-1000 mg / L, and the content of the organic base is 20-1500 mmol / L. The quaternary ammonium base compound is tetraethylammonium hydroxide, tetrapropylammonium hydroxide or tetrabutylammonium hydroxide, or a combination of two or three thereof; the fatty amine compound is ethylamine, n-butylamine, butanediamine or hexanediamine, or a combination of two or three thereof; and the alcohol amine compound is monoethanolamine, diethanolamine or triethanolamine, or a combination of two or three thereof. The silicon source is an organic silicon source and / or an inorganic silicon source; the organic silicon source is selected from tetramethyl silicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate or dimethoxydiethoxysilane, or a combination of two or three thereof; and the inorganic silicon source is selected from silica sol and / or silica gel. The active center source is selected from one or more of iron chloride, iron nitrate, iron sulfate, titanium chloride, titanium sulfate, vanadate, chromate, ferrate, titanate, titanate ester, iron naphthenate and chromium acetylacetone. 4.Nanomaterials prepared by the method of any one of claims 1-3. ​ ​ ​ ​ ​ 2. The method of claim 1, wherein, ​ 3. The method of claim 1, wherein, ​ ​ ​ ​ ​ 5. The nanomaterial of claim 4, wherein, The nanoparticle has a pore size of 0.5-0.7 nm.

6. Use of the nanoparticle according to claim 4 or 5 for the oxidation of phenol to dihydric phenols.

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