CN112744803B - Nanometer material and preparation method thereof - Google Patents

Nanometer material and preparation method thereof Download PDF

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CN112744803B
CN112744803B CN201911038934.3A CN201911038934A CN112744803B CN 112744803 B CN112744803 B CN 112744803B CN 201911038934 A CN201911038934 A CN 201911038934A CN 112744803 B CN112744803 B CN 112744803B
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source
mixture
silicon source
carbon dot
graphite rod
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CN112744803A (en
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史春风
康振辉
黄慧
王肖
孙悦
周赟杰
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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China Petroleum and Chemical Corp
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/18—Carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
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    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/65—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing carbon

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Abstract

The present disclosure relates to a method of preparing a nanomaterial and nanomaterial prepared by the method, the method comprising: a. preparing a carbon dot solution; b. uniformly mixing a silicon source, an active center source, organic alkali and optional water to obtain a first mixture; c. mixing the carbon dot solution with the first mixture to perform hydrolysis reaction to obtain a second mixture; d. and carrying out hydrothermal treatment on the second mixture, collecting a solid product, washing, drying and roasting to obtain the nano material. The nano material disclosed by the invention has excellent catalytic activity in the phenol oxidation reaction, and meanwhile, the catalytic stability and repeatability are good.

Description

Nanometer material and preparation method thereof
Technical Field
The present disclosure relates to a nanomaterial and a method of preparing the same.
Background
The carbon nanomaterial is similar to the common nanomaterial in optical, electrical, magnetic and other aspects and has special properties such as quantum size effect, small size effect, macroscopic quantum tunneling effect and the like. In 2004, fine carbon nano particles with the size smaller than 10nm, which are found when single-layer carbon nano tubes are purified by an electrophoresis method, are named as carbon dots for the first time, and are novel small-size carbon nano materials. The carbon dots are also referred to as fluorescent carbon dots because of their excellent fluorescent properties. Fluorescent carbon dots have become a new star of the carbon nano-family in the last ten years from the discovery of fluorescent carbon dots to the realization of the application. The materials for synthesizing the fluorescent carbon dots are more and more abundant, and the preparation method is also endless. The nature and application of the fluorescent carbon dots in various aspects have also been studied more and more carefully and comprehensively, and significant progress has been made in the end. Compared with organic dyes and traditional semiconductor quantum dots, the fluorescent carbon dots have unique optical and electrical characteristics besides good water solubility, high stability, low toxicity and good biocompatibility. Therefore, research on the properties and applications of fluorescent carbon dots is getting more and more attention.
In recent years, fluorescent carbon dots have been used as a novel and unique fluorescent probe or fluorescent marker, and have been widely used in bioimaging, detection and medical delivery, based on their excellent and tunable fluorescent properties. Besides the excellent down-conversion fluorescence property, the fluorescent carbon dots also show the excellent up-conversion fluorescence property, and researchers design a series of high-activity composite catalysts based on the property of the fluorescent carbon dots, so that the absorption of the composite material to light is enhanced, and the catalytic efficiency of the reaction is effectively improved. Under illumination, the fluorescence of the fluorescent carbon dots can be effectively quenched by known electron acceptors or electron donors, indicating that the fluorescent carbon dots have excellent photogenerated electron transfer properties, and can serve as both electron donors and electron acceptors. Based on the fluorescent carbon dots, the fluorescent carbon dots can be applied to the related fields of energy conversion, environmental protection, photovoltaic devices and the like.
The green catalytic oxidation material titanium silicon molecular sieve is developed in the beginning of the eighties of the last century, and has the catalytic oxidation function of titanium and the shape selective function. As the pollution-free low-concentration hydrogen peroxide can be used as the oxidant in the oxidation reaction of the organic matters, the problems of complex process and environmental pollution in the oxidation process are avoided, and the method has the advantages of incomparable energy conservation, economy, environmental friendliness and the like of the traditional oxidation system, has good reaction selectivity and has great industrial application prospect. However, the repeatability, stability, cost and other aspects of the synthesis method are not ideal at present. Therefore, it is a key to develop materials to improve the corresponding synthetic methods.
Disclosure of Invention
The aim of the present disclosure is to provide a nanomaterial and a method for preparing the same, which has excellent catalytic activity in the oxidation reaction of phenol, and simultaneously has good stability and repeatability.
In order to achieve the above object, a first aspect of the present disclosure provides a method for preparing a nanomaterial, the method comprising the steps of:
a. connecting a first conductive object with a positive electrode of a direct current power supply, connecting a second conductive object with a negative electrode of the direct current power supply, placing the second conductive object in an electrolyte, applying a voltage of 0.1-60V, preferably 5-40V, for electrolysis for 1-20 days, preferably 2-10 days, and concentrating the obtained electrolyzed electrolyte to obtain a carbon dot solution, wherein the first conductive object is a graphite rod, and the electrolyte optionally contains a first organic base;
b. uniformly mixing a silicon source, an active center source, a second organic base and optional water to obtain a first mixture;
c. mixing the carbon dot solution obtained in the step a with the first mixture obtained in the step b, and carrying out hydrolysis reaction for 0.1-12 h at 20-100 ℃ to obtain a second mixture;
d. and c, carrying out hydrothermal treatment on the second mixture obtained in the step c in a heat-resistant closed container at 80-200 ℃ for 2-360 hours, collecting a solid product, washing, drying and roasting to obtain the nanomaterial.
Optionally, in the step a, the diameter of the graphite rod is 2-20 mm, and the length is 2-100 cm; and/or the number of the groups of groups,
the second conductive material is an iron rod, an iron plate, a graphite rod, a graphite plate, a copper plate or a copper rod, preferably an iron rod, a graphite rod or a copper rod, and more preferably a graphite rod matched with the size of the first conductive material.
Optionally, in step a, the mass fraction of the first organic base in the electrolyte is 0 to 10 wt%, preferably 0.1 to 5 wt%; and/or the number of the groups of groups,
the carbon dot concentration of the carbon dot solution is 0.01 to 5mg/mL, preferably 0.1 to 1mg/mL.
Optionally, the first organic base and the second organic base are each independently selected from one or more of urea, a quaternary ammonium base compound, a quaternary ammonium salt compound, a fatty amine compound and an alcohol amine compound.
Optionally, the quaternary ammonium base compound is tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, or a combination of two or three thereof;
the quaternary ammonium salt compound is tetraethylammonium chloride, tetraethylammonium bromide, tetrapropylammonium chloride, tetrapropylammonium bromide, tetrabutylammonium chloride or tetrabutylammonium bromide, or a combination of two or three of the above;
the fatty amine compound is ethylamine, n-butylamine, butanediamine or hexamethylenediamine or a combination of two or three of the above;
the alcohol amine compound is monoethanolamine, diethanolamine or triethanolamine, or a combination of two or three of the monoethanolamine, diethanolamine or triethanolamine.
Optionally, in step b, the silicon source is an inorganic silicon source and/or an organic silicon source; the inorganic silicon source is silica sol and/or silica gel, and the organic silicon source is organic silicon ester;
preferably, the silicon source is tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, or dimethoxy diethoxy silane, or a combination of two or three thereof;
more preferably, the silicon source is tetraethyl orthosilicate.
Optionally, in step b, the active center source is an aluminum source, a titanium source, an iron source, a zirconium source, a chromium source, a copper source, or a zinc source, or a combination of two or three thereof.
Optionally, in step b, the weight ratio of the silicon source, the active center source, the organic base, and the water is 100: (0.005-10.0): (0.01-100): (0 to 10000), preferably 100: (0.01-5.0): (0.05-20): (200-5000).
Optionally, in step c, the weight ratio of the carbon dot solution to the silicon source in the first mixture is (0.01-2): 1, preferably (0.05 to 1): 1.
optionally, in step d, the drying conditions include: the temperature is 100-200 ℃, preferably 110-150 ℃; the time is 1 to 24 hours, preferably 2 to 12 hours; the roasting conditions include: the temperature is 300-800 ℃, preferably 350-650 ℃; the time is 0.1 to 12 hours, preferably 1 to 8 hours.
A second aspect of the present disclosure: there is provided a nanomaterial made by the method of the first aspect of the present disclosure.
According to the technical scheme, the carbon points are introduced in the initial material mixing stage, the hydrolysis of the raw materials including the silicon source and the active center source is promoted, porous structures such as holes or defects are introduced in the process, the improvement of the catalytic performance of the nano material is facilitated, the nano material prepared by the method has a rich mesoporous structure, the diffusion of reactant molecules is facilitated, the distribution of the active centers is improved, the nano material has excellent catalytic activity in the phenol oxidation reaction, and meanwhile, the catalytic stability and the repeatability are good.
Additional features and advantages of the present disclosure will be set forth in the detailed description which follows.
Detailed Description
Specific embodiments of the present disclosure will be described in detail below. It should be understood that the detailed description and specific examples, while indicating and illustrating the disclosure, are not intended to limit the disclosure.
The first aspect of the present disclosure: the preparation method of the nano material comprises the following steps:
a. connecting a first conductive object with a positive electrode of a direct current power supply, connecting a second conductive object with a negative electrode of the direct current power supply, placing the second conductive object in an electrolyte, applying a voltage of 0.1-60V, preferably 5-40V, for electrolysis for 1-20 days, preferably 2-10 days, and concentrating the obtained electrolyzed electrolyte to obtain a carbon dot solution, wherein the first conductive object is a graphite rod, and the electrolyte optionally contains a first organic base;
b. uniformly mixing a silicon source, an active center source, a second organic base and optional water to obtain a first mixture;
c. mixing the carbon dot solution obtained in the step a with the first mixture obtained in the step b, and carrying out hydrolysis reaction for 0.1-12 h at 20-100 ℃ to obtain a second mixture;
d. and c, carrying out hydrothermal treatment on the second mixture obtained in the step c in a heat-resistant closed container at 80-200 ℃ for 2-360 hours, collecting a solid product, washing, drying and roasting to obtain the nanomaterial.
According to the present disclosure, in the step a, the graphite rod is a rod made of graphite, and the size thereof may vary within a wide range, for example, the diameter of the graphite rod may be 2 to 20mm, and the length thereof may be 2 to 100cm, wherein the length refers to the axial length of the graphite rod.
According to the present disclosure, in the step a, the second conductive material may be various common conductive materials, and there is no requirement on the material and shape, for example, the shape may be a common rod or plate, specifically, an iron rod, an iron plate, a graphite rod, a graphite plate, a copper rod, etc., preferably, a rod like iron rod, a graphite rod, a copper rod, etc., further preferably, a graphite rod, and further preferably, there is no special limitation on the size, and most preferably, a graphite rod matching the size of the first conductive material. The electrolysis may be performed with a distance between the first and second conductors, for example 3-10 cm.
According to the present disclosure, in the step a, the electrolyte may have a resistivity of 0 to 20mΩ·cm -1 The amount of the electrolyte is not particularly limited and may be adjusted according to the material and size of the conductive material and the electrolysis conditions.
According to the present disclosure, the mass fraction of the first organic base in the electrolyte may vary widely according to practical situations, for example, the mass fraction of the first organic base in the electrolyte may be 0 to 10 wt%, and in a preferred embodiment, the mass fraction of the first organic base in the electrolyte may be 0.1 to 5 wt%.
The organic alkali is added in the preparation process of the carbon dot solution, so that the preparation condition of the carbon dot is more relaxed, the required preparation voltage is effectively reduced, the preparation time is shortened, the carbon dot structure is improved, the obtained carbon dot solution can more effectively exert the effect in the subsequent utilization process, the nano material prepared by adopting the carbon dot solution has excellent catalytic performance in catalytic reaction, particularly in phenol hydroxylation reaction, and the selectivity of hydroquinone in the product is higher.
In step a, the concentration treatment is a common technical means in the art, such as concentration by membrane separation, etc., and the disclosure will not be repeated here. The carbon dot concentration of the carbon dot solution obtained by the concentration treatment may be 0.01 to 5mg/mL, and in a preferred embodiment, the carbon dot concentration of the carbon dot solution obtained by the concentration treatment may be 0.1 to 1mg/mL.
According to the present disclosure, the first organic base and the second organic base are common organic bases in the art, and the first organic base and the second organic base may be each independently selected from one or more of urea, a quaternary ammonium compound, a fatty amine compound, and an alcohol amine compound, wherein the quaternary ammonium compound, the fatty amine compound, and the alcohol amine compound may be conventional types, respectively.
In one embodiment, the quaternary ammonium base compound may be (R 1 ) 4 NOH, where R 1 Can be selected from C 1 -C 4 Straight chain alkyl and C 3 -C 4 For example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl or methallyl. Preferably, R 1 Is n-propyl, i.e., the quaternary ammonium base compound may be tetrapropylammonium hydroxide.
In one embodiment, the quaternary ammonium salt compound may be tetraethylammonium chloride, tetraethylammonium bromide, tetrapropylammonium chloride, tetrapropylammonium bromide, tetrabutylammonium chloride, or tetrabutylammonium bromide, or a combination of two or three thereof. Preferably, the quaternary ammonium salt compound may be tetrapropylammonium bromide.
In one embodiment, the fatty amine compound may be R 2 (NH 2 ) n Wherein R is 2 May beC 1 -C 6 Alkyl of (2), e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl or n-hexyl, R 2 May also be C 1 -C 6 Alkylene of (a), such as methylene, ethylene, n-propylene, n-butylene or n-hexylene, n is an integer of 1 or 2. Preferably, the fatty amine compound may be ethylamine, n-butylamine, butanediamine or hexamethylenediamine, or a combination of two or three thereof.
In one embodiment, the alcohol amine compound may be (HOR 3 ) m NH (3-m) Wherein R is 3 May be C 1 -C 4 M is an integer of 1, 2 or 3. For example, the alcohol amine compound may be monoethanolamine, diethanolamine or triethanolamine, or a combination of two or three thereof.
In accordance with the present disclosure, the silicon source is well known to those skilled in the art, and in step b, the silicon source may be selected from at least one of an inorganic silicon source and an organic silicon source, wherein the inorganic silicon source may be selected from at least one of silicate, silica sol and silica gel, the organic silicon source may be an organic silicon grease, and in a preferred embodiment, the silicon source may be tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate or dimethoxydiethoxysilane, or a combination of two or three thereof, more preferably, the silicon source may be tetraethyl orthosilicate.
According to the present disclosure, in step b, the active center source may be, but is not limited to, an aluminum source, a titanium source, an iron source, a zirconium source, a chromium source, a copper source, or a zinc source, or a combination of two or three thereof, preferably the active center source is a titanium source. The weight ratio of the silicon source, the active center source, the organic base, and the water may vary over a wide range, and the weight ratio of the silicon source, the active center source, the organic base, and the water may be 100: (0.005-10.0): (0.01-100): (0 to 10000), in a preferred embodiment, the weight ratio of the silicon source, the active center source, the organic base, and the water may be 100: (0.01-5.0): (0.05-20): (200-5000).
According to the present disclosure, in step c, the weight ratio of the carbon dot solution to the silicon source in the first mixture may be (0.01 to 2): 1, preferably (0.05 to 1): 1.
in step d, according to the present disclosure, the hydrothermal reaction may be performed in a conventional reactor, for example in a polytetrafluoroethylene reaction vessel. Moreover, the pressure of the hydrothermal reaction process is not particularly limited, and may be the autogenous pressure of the system or may be performed under additional applied pressure conditions, and preferably, the hydrothermal reaction process is performed under autogenous pressure (usually performed in a closed vessel). The method of collecting the solid product after the hydrothermal reaction may be carried out by conventional methods such as filtration, centrifugation, etc. The conditions for drying and calcining the solid product may be conventional in the art, for example, the conditions for drying may include: the temperature is 100-200 ℃, preferably 110-150 ℃; the time is 1 to 24 hours, preferably 2 to 12 hours; the conditions of the firing may include: the temperature is 300-800 ℃, preferably 350-650 ℃; the time is 0.1 to 12 hours, preferably 1 to 8 hours.
A second aspect of the present disclosure: there is provided a nanomaterial made by the method of the first aspect of the present disclosure.
The nano material disclosed by the disclosure has a rich mesoporous structure, and the specific surface area of mesopores is not less than 60m 2 And/g, the nano material disclosed by the invention is used as a catalyst for catalyzing the oxidation reaction of phenol, so that the catalysis of phenol can be realized under mild conditions, and the raw material conversion rate and the target product hydroquinone selectivity are higher.
In the hydroxylation reaction of the catalytic oxidation phenol, the economic value of the target product hydroquinone is obviously higher than that of catechol, however, when a conventional catalyst is used, the catechol in the product distribution is generally more than that of hydroquinone, and the selectivity of the hydroquinone is relatively difficult to improve, especially under the same oxidation reaction condition, the selectivity of the hydroquinone is difficult to effectively improve by only adjusting the structure or morphology of the same type of catalyst, the selectivity of the hydroquinone is generally improved by less than 5 percent, and the selectivity of the hydroquinone is generally improved by less than 2 percent. According to the method, carbon points are introduced in the initial material mixing stage, hydrolysis of raw materials including a silicon source and an active center source is promoted, porous structures such as holes or defects are introduced in the process, the catalytic performance of the nano material is improved, the nano material prepared by the method has a rich mesoporous structure, the diffusion of reactant molecules is facilitated, the distribution of the active centers is improved, the shape selectivity of the nano material is facilitated, the selectivity of hydroquinone in a product is obviously improved, and the nano material has excellent catalytic activity in the oxidation reaction of phenol, and meanwhile, the catalytic stability and repeatability are good.
The following examples will further illustrate the disclosure, but are not thereby limiting the disclosure.
Examples 1 to 7 are provided to illustrate the nanomaterial of the present disclosure and a method of preparing the same.
In the preparation examples, the specific surface area of the mesoporous was calculated by BJH method (see petrochemical analysis method (RIPP test method), RIPP151-90, published by scientific Press, 1990) using nitrogen adsorption capacity method.
Example 1
950mL of the mixture having a resistivity of 18MΩ cm was added to a beaker -1 Then 50g of a 10 wt% tetraethylammonium hydroxide solution was added to form 0.5 wt% tetraethylammonium hydroxide-containing electrolyte, an anode graphite rod (diameter 10mm length 30 cm) and a cathode graphite rod (diameter 10mm length 30 cm) were placed therein, the distance between the anode graphite rod and the cathode graphite rod was maintained at 10cm, the anode graphite rod was connected to the positive electrode of a direct current power supply and the cathode graphite rod was connected to the negative electrode of the direct current power supply, electrolysis was performed for 3 days by applying a voltage of 20V, and the resulting electrolyzed electrolyte was concentrated to obtain a carbon dot solution having a carbon dot concentration of 0.5 mg/mL; mixing tetraethyl orthosilicate 22.5g, tetrabutyl titanate 1.1g, tetrapropylammonium hydroxide (25% aqueous solution) 7g and deionized water 50g to obtain a first mixture, adding 10g of the carbon dot solution into the first mixture under vigorous stirring at a stirring speed of 800 rpm, performing hydrolysis reaction at 75 ℃ for 3h to obtain a second mixture, and mixing the second mixture with deionized waterTransferring the mixture into a stainless steel reaction kettle, performing hydrothermal reaction at 170 ℃ for 72 hours, collecting a solid product, washing the solid product with deionized water, drying at 110 ℃ for 2 hours, and roasting at 550 ℃ for 3 hours to obtain the nanomaterial C1. Detecting that the specific surface area of the mesoporous is 83m 2 And/g, indicating that the polymer has a rich mesoporous structure.
Example 2
995mL of a 18 M.OMEGA.cm resistivity was added to the beaker -1 Then adding 5g of a 10 wt% tetraethylammonium hydroxide solution to form 0.05 wt% tetraethylammonium hydroxide-containing electrolyte, placing an anode graphite rod (diameter 10mm length 30 cm) and a cathode graphite rod (diameter 10mm length 30 cm) in the electrolyte, keeping the distance between the anode graphite rod and the cathode graphite rod at 30cm, connecting the anode graphite rod with the positive electrode of a direct current power supply and the cathode graphite rod with the negative electrode of the direct current power supply, applying a voltage of 60V to electrolyze for 2 days, and concentrating the obtained electrolyzed electrolyte to obtain a carbon point solution with the carbon point concentration of 0.5 mg/mL; 22.5g of tetraethyl orthosilicate, 1.1g of tetraethyl titanate, 7g of tetrapropylammonium hydroxide (25% aqueous solution) and 50g of deionized water are mixed to obtain a first mixture, 30g of the carbon dot solution is added into the first mixture under vigorous stirring with the stirring speed of 800 r/min, hydrolysis reaction is carried out at 75 ℃ for 3h to obtain a second mixture, the second mixture is transferred into a stainless steel reaction kettle, hydrothermal reaction is carried out at 170 ℃ for 72h, solid products are collected, washed by deionized water, dried at 110 ℃ for 2h and baked at 550 ℃ for 3h to obtain the nanomaterial C1. Detecting that the specific surface area of the mesoporous is 75m 2 And/g, indicating that the polymer has a rich mesoporous structure.
Example 3
400mL of a 18M omega cm resistivity was added to the beaker -1 Then 600g of a 10 wt% tetraethylammonium hydroxide solution was added to form 6 wt% tetraethylammonium hydroxide-containing electrolyte, an anode graphite rod (diameter 10mm length 30 cm) and a cathode graphite rod (diameter 10mm length 30 cm) were placed therein, the distance between the anode graphite rod and the cathode graphite rod was maintained at 10cm, the anode graphite rod was connected to the positive electrode of a DC power supply and the cathode graphite rod was connected to the negative electrode of the DC power supplyThen, applying a voltage of 20V to carry out electrolysis for 3 days, and concentrating the obtained electrolyzed electrolyte to obtain a carbon dot solution with the carbon dot concentration of 0.5 mg/mL; 22.5g of tetraethyl orthosilicate, 1.1g of tetrabutyl titanate, 2g of ethylenediamine and 50g of deionized water are mixed to obtain a first mixture, 0.1g of carbon dot solution is taken and added into the first mixture under vigorous stirring with the stirring speed of 800 revolutions per minute, hydrolysis reaction is carried out for 3 hours at 75 ℃ to obtain a second mixture, the second mixture is transferred into a stainless steel reaction kettle, hydrothermal reaction is carried out for 72 hours at 170 ℃, solid products are collected, washed by deionized water and then dried for 2 hours at 110 ℃, and roasting is carried out for 3 hours at 550 ℃, thus obtaining the nanomaterial C1. Detecting that the specific surface area of the mesoporous is 85m 2 And/g, indicating that the polymer has a rich mesoporous structure.
Example 4
950mL of the mixture having a resistivity of 18MΩ cm was added to a beaker -1 Then 50g of a 10 wt% tetraethylammonium hydroxide solution was added to form 0.5 wt% tetraethylammonium hydroxide-containing electrolyte, an anode graphite rod (diameter 10mm length 30 cm) and a cathode graphite rod (diameter 10mm length 30 cm) were placed therein, the distance between the anode graphite rod and the cathode graphite rod was maintained at 10cm, the anode graphite rod was connected to the positive electrode of a direct current power supply and the cathode graphite rod was connected to the negative electrode of the direct current power supply, a voltage of 20V was applied to carry out electrolysis for 3 days, and the resulting electrolyzed electrolyte was concentrated to obtain a carbon dot solution having a carbon dot concentration of 2 mg/mL; mixing 22.5g of tetrapropyl orthosilicate, 1.5g of tetrabutyl titanate, 20g of tetrapropylammonium hydroxide (25% aqueous solution) and 50g of deionized water to obtain a first mixture, adding 10g of the carbon dot solution into the first mixture under vigorous stirring at a stirring speed of 800 r/min, carrying out hydrolysis reaction at 75 ℃ for 3h to obtain a second mixture, transferring the second mixture into a stainless steel reaction kettle, carrying out hydrothermal reaction at 170 ℃ for 72h, collecting a solid product, washing with deionized water, drying at 110 ℃ for 2h, and roasting at 550 ℃ for 3h to obtain the nanomaterial C1. Detecting that the specific surface area of the mesoporous is 85m 2 And/g, indicating that the polymer has a rich mesoporous structure.
Example 5
950mL of electricity was added to the beakerThe resistivity is 18MΩ & cm -1 Then 50g of a 10 wt% tetraethylammonium hydroxide solution was added to form 0.5 wt% tetraethylammonium hydroxide-containing electrolyte, an anode graphite rod (diameter 10mm length 30 cm) and a cathode graphite rod (diameter 10mm length 30 cm) were placed therein, the distance between the anode graphite rod and the cathode graphite rod was maintained at 10cm, the anode graphite rod was connected to the positive electrode of a direct current power supply and the cathode graphite rod was connected to the negative electrode of the direct current power supply, electrolysis was performed for 3 days by applying a voltage of 20V, and the resulting electrolyzed electrolyte was concentrated to obtain a carbon dot solution having a carbon dot concentration of 0.05 mg/mL; 90g of tetraethyl orthosilicate, 0.01g of tetrabutyl titanate, 0.04g of tetrapropylammonium hydroxide (25% aqueous solution) and 5000g of deionized water are mixed to obtain a first mixture, 10g of the carbon dot solution is added into the first mixture under vigorous stirring with the stirring speed of 800 r/min, hydrolysis reaction is carried out at 60 ℃ for 4h to obtain a second mixture, the second mixture is transferred into a stainless steel reaction kettle, hydrothermal reaction is carried out at 170 ℃ for 72h, solid products are collected, washed by deionized water, dried at 110 ℃ for 2h and baked at 550 ℃ for 3h to obtain the nanomaterial C1. Detecting that the specific surface area of the mesoporous is 78m 2 And/g, indicating that the polymer has a rich mesoporous structure.
Example 6
950mL of the mixture having a resistivity of 18MΩ cm was added to a beaker -1 Then 50g of a 10 wt% tetraethylammonium hydroxide solution was added to form 0.5 wt% tetraethylammonium hydroxide-containing electrolyte, an anode graphite rod (diameter 10mm length 30 cm) and a cathode graphite rod (diameter 10mm length 30 cm) were placed therein, the distance between the anode graphite rod and the cathode graphite rod was maintained at 10cm, the anode graphite rod was connected to the positive electrode of a direct current power supply and the cathode graphite rod was connected to the negative electrode of the direct current power supply, electrolysis was performed for 3 days by applying a voltage of 20V, and the resulting electrolyzed electrolyte was concentrated to obtain a carbon dot solution having a carbon dot concentration of 0.5 mg/mL; 4.5g of tetraethyl orthosilicate, 1.1g of tetrabutyl titanate, 10g of tetrapropylammonium hydroxide (25% aqueous solution) and 20g of deionized water are mixed to obtain a first mixture, and 2g of the carbon dot solution is taken and added into the mixture under vigorous stirring at a stirring speed of 800 revolutions per minuteAnd (3) carrying out hydrolysis reaction on the first mixture at 75 ℃ for 3 hours to obtain a second mixture, transferring the second mixture into a stainless steel reaction kettle, carrying out hydrothermal reaction at 150 ℃ for 60 hours, collecting a solid product, washing with deionized water, drying at 160 ℃ for 1 hour, and roasting at 700 ℃ for 8 hours to obtain the nano material C1. Detecting that the specific surface area of the mesoporous is 80m 2 And/g, indicating that the polymer has a rich mesoporous structure.
Example 7
500mL of a 18 M.OMEGA.cm resistivity was added to the beaker -1 Placing an anode graphite rod (diameter 10mm length 30 cm) and a cathode graphite rod (diameter 10mm length 30 cm) therein, maintaining the distance between the anode graphite rod and the cathode graphite rod at 10cm, connecting the anode graphite rod with the positive electrode of a direct current power supply, connecting the cathode graphite rod with the negative electrode of the direct current power supply, applying a voltage of 50V for electrolysis for 8 days, and concentrating the obtained electrolyzed electrolyte to obtain a carbon dot solution with a carbon dot concentration of 0.5 mg/mL; 22.5g of tetraethyl orthosilicate, 1.1g of tetrabutyl titanate, 7g of tetrapropylammonium hydroxide (25% aqueous solution) and 50g of deionized water are mixed to obtain a first mixture, 10g of the carbon dot solution is added into the first mixture under vigorous stirring at the stirring speed of 800 r/min, hydrolysis reaction is carried out at 75 ℃ for 3h to obtain a second mixture, the second mixture is transferred into a stainless steel reaction kettle, hydrothermal reaction is carried out at 170 ℃ for 72h, solid products are collected, washed by deionized water, dried at 110 ℃ for 1h and baked at 550 ℃ for 3h to obtain the nanomaterial D2 serving as a comparison. Detecting that the specific surface area of the mesoporous is 72m 2 And/g, indicating that the polymer has a rich mesoporous structure.
Comparative example 1
22.5g of tetraethyl orthosilicate, 1.1g of tetrabutyl titanate, 7g of tetrapropylammonium hydroxide (25% aqueous solution) and 50g of deionized water are mixed to obtain a first mixture, hydrolysis reaction is carried out at 75 ℃ for 3 hours under vigorous stirring with the stirring speed of 800 revolutions per minute to obtain a second mixture, the second mixture is transferred into a stainless steel reaction kettle, hydrothermal reaction is carried out at 170 ℃ for 72 hours, a solid product is collected, and the solid product is dried at 110 ℃ for 1 hour and baked at 550 ℃ for 3 hours after being washed by deionized water, so as to obtain the nano material D1 for comparison. Detecting the specific surface area of the mesoporous15m of 2 And/g, showing less mesoporous structure.
Test case
The nanomaterials C1 to C7 obtained in examples 1 to 7 and the sample D1 obtained in the method of comparative example were used as fresh catalysts for the catalytic effect of the oxidation reaction of phenol.
The phenol oxidation reaction was carried out in a 250ml three-necked flask reaction apparatus with an automatic temperature control water bath, magnetic stirring and condensate reflux system. The nano material, solvent acetone and phenol are mixed according to the weight ratio of 1:25:10 sequentially adding three bottles, putting the bottles into a water bath kettle with the preset reaction temperature of 60 ℃, slowly adding hydrogen peroxide (mass fraction of 50%) into a reaction system, wherein the molar ratio of the hydrogen peroxide to the phenol is 1:3, after 2 hours of reaction, the reaction was stopped by cooling, and the reaction results are shown in Table 1.
The catalyst after the above reaction was washed with water and dried and then used again for the oxidation reaction of phenol, and thus recycled 5 times to obtain a nanomaterial as an unrenewed catalyst for the oxidation reaction of phenol, and the reaction results are shown in table 1.
The oxidation products were analyzed by gas chromatography (GC: agilent, 7890A) and gas chromatography-mass spectrometry (GC-MS: thermo Fisher Trace ISQ). Conditions of gas chromatography: nitrogen carrier gas, temperature rise at 140K procedure: 60 ℃,1 minute, 15 ℃/minute, 180 ℃ and 15 minutes; split ratio, 10:1, a step of; the temperature of the sample inlet is 300 ℃; detector temperature, 300 ℃. The following formulas are used on this basis to calculate the feedstock conversion and target product selectivity, respectively:
% phenol conversion = (molar amount of phenol added before reaction-molar amount of phenol remaining after reaction)/molar amount of phenol added before reaction x 100%;
hydroquinone selectivity% = (molar amount of hydroquinone formed after reaction)/molar amount of phenol added before reaction x 100%.
TABLE 1
As can be seen from Table 1, the use of the nanomaterial of the present disclosure as a catalyst can catalyze phenol under mild conditions, and has high raw material conversion rate and hydroquinone selectivity as a target product, and has high activity after 5 times of cyclic utilization, and the conversion rate and the selectivity of the target product are reduced slightly. In the preparation process of the nano material, carbon points are introduced in the initial material mixing stage, the hydrolysis of the raw materials including a silicon source and an active center source is promoted, mesoporous porous structures such as holes or defects are introduced in the process, the improvement of the catalytic performance is facilitated, the nano material prepared by the method has rich mesoporous structures, and the mesoporous specific surface area of the nano material is not less than 60m preferably 2 Under the condition of/g, the activity of the catalyst can be further improved, the selectivity of hydroquinone with higher economic value in the catalytic product of phenol is also obviously increased, and the subsequent separation difficulty is reduced. The nano material disclosed by the invention can still maintain excellent catalytic activity after being repeatedly used for many times, and has good stability and repeatability.
The preferred embodiments of the present disclosure have been described in detail above, but the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and all the simple modifications belong to the protection scope of the present disclosure.
In addition, the specific features described in the foregoing embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, the present disclosure does not further describe various possible combinations.
Moreover, any combination between the various embodiments of the present disclosure is possible as long as it does not depart from the spirit of the present disclosure, which should also be construed as the disclosure of the present disclosure.

Claims (22)

1. A method for preparing a nanomaterial, the method comprising the steps of:
a. connecting a first conductive object with a positive electrode of a direct current power supply, connecting a second conductive object with a negative electrode of the direct current power supply, placing the second conductive object in electrolyte, applying a voltage of 0.1-60V for electrolysis for 1-20 days, and concentrating the obtained electrolyzed electrolyte to obtain a carbon dot solution, wherein the first conductive object is a graphite rod, and the electrolyte contains first organic alkali;
b. uniformly mixing a silicon source, an active center source, a second organic base and optional water to obtain a first mixture;
c. mixing the carbon dot solution obtained in the step a with the first mixture obtained in the step b, and carrying out hydrolysis reaction at 20-100 ℃ for 0.1-12 h to obtain a second mixture;
d. c, carrying out hydrothermal treatment on the second mixture obtained in the step c in a heat-resistant closed container at 80-200 ℃ for 2-360 hours, collecting a solid product, washing, drying and roasting to obtain a nano material;
in the step b, the active center source is an aluminum source, a titanium source, an iron source, a zirconium source, a chromium source, a copper source or a zinc source, or a combination of two or three of the above sources;
the weight ratio of the silicon source, the active center source, the second organic base, and the water is 100: (0.005-10.0): (0.01-100): (0-10000);
in the step c, the weight ratio of the carbon dot solution to the silicon source in the first mixture is (0.01-2): 1.
2. the method of claim 1, wherein in step a, the voltage is 5-40 v.
3. The method according to claim 1, wherein in step a, the electrolysis is performed for a period of 2 to 10 days.
4. A method according to any one of claims 1 to 3, wherein in step a, the graphite rod has a diameter of 2 to 20mm and a length of 2 to 100cm; and/or the number of the groups of groups,
the second conductive object is an iron rod, an iron plate, a graphite rod, a graphite plate, a copper plate or a copper rod.
5. The method of claim 4, wherein the second conductive object is an iron rod, a graphite rod, or a copper rod.
6. The method of claim 5, wherein the second conductive object is a graphite rod that matches the size of the first conductive object.
7. The method according to any one of claims 1 to 3, wherein in step a, the mass fraction of the first organic base in the electrolyte is 0.1 to 10 wt%; and/or the number of the groups of groups,
the carbon dot concentration of the carbon dot solution is 0.01-5 mg/mL.
8. The method according to claim 7, wherein in the step a, the mass fraction of the first organic base in the electrolyte is 0.1 to 5 wt%.
9. The method according to claim 7, wherein in the step a, the carbon dot concentration of the carbon dot solution is 0.1 to 1mg/mL.
10. The method according to any one of claims 1 to 3, wherein the first organic base and the second organic base are each independently selected from one or more of urea, a quaternary ammonium base compound, a quaternary ammonium salt compound, an aliphatic amine compound, and an alcohol amine compound.
11. The method of claim 10, wherein the quaternary ammonium base compound is tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, or a combination of two or three thereof;
the quaternary ammonium salt compound is tetraethylammonium chloride, tetraethylammonium bromide, tetrapropylammonium chloride, tetrapropylammonium bromide, tetrabutylammonium chloride or tetrabutylammonium bromide, or a combination of two or three of the above;
the fatty amine compound is ethylamine, n-butylamine, butanediamine or hexamethylenediamine or a combination of two or three of the above;
the alcohol amine compound is monoethanolamine, diethanolamine or triethanolamine, or a combination of two or three of the monoethanolamine, diethanolamine or triethanolamine.
12. A method according to any one of claims 1 to 3, wherein in step b, the silicon source is an inorganic silicon source and/or an organic silicon source; the inorganic silicon source is silica sol and/or silica gel, and the organic silicon source is organic silicon ester.
13. The method of claim 12, wherein the silicon source is tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, or dimethoxydiethoxysilane, or a combination of two or three thereof.
14. The method of claim 13, wherein the silicon source is tetraethyl orthosilicate.
15. The method of claim 1, wherein in step b, the weight ratio of the silicon source, the active center source, the second organic base, and the water is 100: (0.01 to 5.0): (0.05-20): (200-5000).
16. The method of claim 1, wherein in step c, the weight ratio of the carbon dot solution to the silicon source in the first mixture is (0.05-1): 1.
17. a method according to any one of claims 1 to 3, wherein in step d, the drying conditions include: the temperature is 100-200 ℃ and the time is 1-24 hours; the roasting conditions include: the temperature is 300-800 ℃ and the time is 0.1-12 h.
18. The method of claim 17, wherein in step d, the drying temperature is 110-150 ℃.
19. The method of claim 17, wherein in step d, the drying time is 2-12 hours.
20. The method of claim 17, wherein in step d, the baking temperature is 350-650 ℃.
21. The method of claim 17, wherein in step d, the roasting time is 1-8 hours.
22. A nanomaterial made by the method of any of claims 1-21.
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CN105457618A (en) * 2014-09-09 2016-04-06 华东理工大学 Carbon quantum dot and titanium codoped mesoporous silica composite photocatalyst
CN105602558A (en) * 2016-03-03 2016-05-25 东南大学 Fluorescent carbon dot narrow in full width at half maximum and preparation method and application thereof

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