CN112742465A - Modified oxidation catalytic material and preparation method thereof - Google Patents
Modified oxidation catalytic material and preparation method thereof Download PDFInfo
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Abstract
The present disclosure relates to a method for modifying an oxidation catalyst material and a modified oxidation catalyst material prepared by the method, the method comprising: a. preparing a carbon dot solution; b. mixing the carbon dot solution with an organic base and optionally water to obtain a first mixture; c. mixing the first mixture with an oxidation catalyst material to obtain a second mixture; d. and carrying out hydrothermal treatment on the second mixture in a heat-resistant closed container, collecting a solid product, washing, drying and roasting to obtain the modified oxidation catalytic material. The modified oxidation catalytic material disclosed by the invention is used as a catalyst for catalyzing the hydroxylation reaction of phenol, the hydroxylation of phenol can be realized under mild conditions, and the conversion rate of raw materials and the selectivity of a target product, namely hydroquinone, are higher.
Description
Technical Field
The disclosure relates to a modified oxidation catalyst material and a preparation method thereof.
Background
The carbon nano material is fine carbon particles with the size of nano-scale (1-100 nm), is similar to common nano materials, and has special properties such as quantum size effect, small size effect, macroscopic quantum tunneling effect and the like in the aspects of optics, electricity, magnetism and the like.
The fine carbon nano particles having a size of less than 10nm, which were found when the single-walled carbon nano tube was purified by the electrophoresis method in 2004, were first named carbon dots, which is a new type of small-sized carbon nano material. Carbon dots are also called fluorescent carbon dots because of their excellent fluorescent properties. Fluorescent carbon dots have become a new star of the carbon nanofamily for as little as a decade from their discovery to their implementation. The materials for synthesizing the fluorescent carbon dots are more and more abundant, and the preparation methods are also infinite. The nature and application of fluorescent carbon dots in all aspects are also being studied more and more carefully and comprehensively, and finally significant progress has been made. Compared with organic dyes and traditional semiconductor quantum dots, the fluorescent carbon dots have unique optical and electrical properties besides good water solubility, high stability, low toxicity and good biocompatibility. Therefore, the research on the properties and applications of the fluorescent carbon dots is receiving more and more attention.
In recent years, fluorescent carbon dots have been used as a novel and unique fluorescent probe or fluorescent marker based on their excellent and tunable fluorescence properties, and have been widely used in biological imaging, detection, and drug delivery. 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 characteristic 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 dot can be effectively quenched by a known electron acceptor or electron donor, which shows that the fluorescent carbon dot has excellent photogenerated electron transfer characteristics and can be used as the electron donor and the electron acceptor. Based on the fluorescent carbon dots, the fluorescent carbon dots can also be applied to the related fields of energy problems, environmental protection, photovoltaic devices and the like.
The green oxidation catalytic material titanium-silicon molecular sieve is developed in the beginning of the last eighties, not only has the catalytic oxidation effect of titanium, but also has the shape-selective effect and excellent stability. In the oxidation reaction of organic matters, pollution-free low-concentration hydrogen peroxide can be used as an oxidant, so that the problems of complex process and environmental pollution in the oxidation process are solved, and the method has the advantages of incomparable energy conservation, economy, environmental friendliness and the like of the traditional oxidation system, and has good reaction selectivity, so that the method has great industrial application prospect. But the repeatability, stability, cost and the like of the existing synthetic method are not ideal. Therefore, improving the corresponding synthesis method is the key to material development.
Disclosure of Invention
An object of the present disclosure is to provide a modified oxidation catalytic material having excellent catalytic activity, stability and reproducibility for a catalytic reaction of phenol, and a method for preparing the same.
In order to achieve the above object, the present disclosure provides, in a first aspect, a method for modifying an oxidation catalyst material, the method comprising the steps of:
a. connecting a first conductive object with the positive electrode of a direct current power supply, connecting a second conductive object with the negative electrode of the direct current power supply, putting the second conductive object into an electrolyte, applying a voltage of 0.1-110V, preferably 5-80V, to electrolyze for 1-30 days, preferably 5-15 days, and concentrating the obtained electrolyzed electrolyte to obtain a carbon dot solution, wherein the first conductive object is a graphite rod;
b. mixing the carbon dot solution obtained in step a with an organic base and optionally water to obtain a first mixture;
c. mixing the first mixture obtained in the step b with an oxidation catalyst material to obtain a second mixture;
d. and c, carrying out hydrothermal treatment on the second mixture obtained in the step c at 80-200 ℃ for 2-360 h, collecting a solid product, washing, drying and roasting to obtain the modified oxidation catalysis material.
Optionally, in the step a, the diameter of the graphite rod is 2-20 mm, and the length of the graphite rod is 2-100 cm; and/or the presence of a gas in the gas,
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 first conductive material in size.
Optionally, in step a, the electrolyzed electrolyte is an aqueous solution, and the water content of the aqueous solution is more than 85 wt%; and/or
The carbon dot concentration of the carbon dot solution is 0.01-5 mg/mL, preferably 0.05-1 mg/mL.
Optionally, in step b, the organic base is urea, a quaternary ammonium base compound, a quaternary ammonium salt compound, a fatty amine compound or an alcohol amine compound, or a combination of two or three of them.
Optionally, in step b, 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 tetraethylammonium chloride, the tetraethylammonium bromide, the tetrapropylammonium chloride and the tetrabutylammonium bromide;
the aliphatic amine compound is ethylamine, n-butylamine, butanediamine or hexanediamine, or a combination of two or three of the ethylamine, the n-butylamine, the butanediamine and the hexanediamine;
the alcohol amine compound is monoethanolamine, diethanolamine or triethanolamine, or a combination of two or three of the monoethanolamine, diethanolamine and triethanolamine.
Optionally, in the steps b and c, the amount of the organic base is 0.01 to 10.0mol, preferably 0.02 to 2.0mol, relative to 100g of the oxidation catalyst material; the using amount of the carbon dot solution is 1-1000 g, preferably 10-500 g; the amount of the water is 0-10000 g, preferably 200-5000 g.
Optionally, in step b, the weight ratio of the carbon dot solution to the organic base is 1: (0.1 to 1000), preferably 1: (0.5 to 500).
Optionally, in step c, the oxidation catalyst material is a titanium-containing molecular sieve, an iron-containing molecular sieve, a vanadium-containing molecular sieve or a tin-containing molecular sieve, or a combination of two or three of them.
Optionally, in step d, 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.
In a second aspect of the present disclosure: there is provided a modified oxidative catalytic material prepared by the method of the first aspect of the present disclosure.
Through the technical scheme, the oxidation catalysis material is treated by using the carbon dots and the organic base, so that the quantity of reaction active centers of the oxidation catalysis material is favorably increased, more porous structures such as holes or defects are introduced in the process, the diffusion of reactant molecules is promoted, the distribution of the active centers is improved, and the improvement of the catalytic performance of the modified oxidation catalysis material is favorably realized. The modified oxidation catalytic material disclosed by the invention is used as a catalyst for catalyzing the hydroxylation reaction of phenol, the hydroxylation of phenol can be realized under mild conditions, and the conversion rate of raw materials and the selectivity of a target product, namely hydroquinone, are higher.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows.
Detailed Description
Hereinafter, specific embodiments of the present disclosure will be described in detail. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.
In a first aspect of the present disclosure, a method for modifying an oxidation catalyst material is provided, which specifically includes the following steps:
a. connecting a first conductive object with the positive electrode of a direct current power supply, connecting a second conductive object with the negative electrode of the direct current power supply, putting the second conductive object into an electrolyte, applying a voltage of 0.1-110V, preferably 5-80V, to electrolyze for 1-30 days, preferably 5-15 days, and concentrating the obtained electrolyzed electrolyte to obtain a carbon dot solution, wherein the first conductive object is a graphite rod;
b. mixing the carbon dot solution obtained in step a with an organic base and optionally water to obtain a first mixture;
c. mixing the first mixture obtained in the step b with an oxidation catalyst material to obtain a second mixture;
d. and c, carrying out hydrothermal treatment on the second mixture obtained in the step c at 80-200 ℃ for 2-360 h, collecting a solid product, washing, drying and roasting to obtain the modified oxidation catalysis material.
According to the disclosure, in step a, the graphite rod is a rod made of graphite, and the size of the rod can vary in a large range, for example, 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.
According to the present disclosure, in step a, the second conductive material may be any of various common conductive materials, and has no material or shape requirement, for example, the second conductive material may be a common rod or plate, specifically, an iron rod, an iron plate, a graphite rod, a graphite plate, a copper rod, and the like, preferably a rod such as an iron rod, a graphite rod, a copper rod, and the like, further preferably a graphite rod, and is not particularly limited in size, and most preferably a graphite rod matching the size of the first conductive material. When the electrolysis is carried out, a certain distance, for example 3-10 cm, can be kept between the first conductor and the second conductor.
According to the present disclosure, in the step a, the electrolyte may have a resistivity of 0 to 20M Ω & cm-1The aqueous solution of (3), further, the water content of the aqueous solution may be 85% by weight or more. The aqueous solution may also contain common inorganic acids (such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc.), inorganic bases (such as sodium hydroxide, potassium hydroxide, oxyhydrogen, etc.), and mixtures thereofCalcium chloride, etc.), inorganic salts (such as sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, etc.) or organic solvents (such as alcohols, ketones, aldehydes, esters, etc.). 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, in step a, the concentration treatment is a common technical means in the art, such as concentration by membrane separation, and the like, and the details of the present disclosure are not repeated herein. The carbon dot concentration of the carbon dot solution obtained by the concentration treatment is 0.01-5 mg/mL, preferably 0.1-1 mg/mL.
According to the present disclosure, in step b, the organic base species may vary within a wide range, and may be at least one of urea, quaternary ammonium base compounds, quaternary ammonium salt compounds, fatty amine compounds, and alcohol amine compounds, for example. Wherein, the quaternary ammonium base compound, the quaternary ammonium salt compound, the fatty amine compound and the alcohol amine compound can be respectively conventional types.
In one embodiment, the quaternary ammonium base compound can be (R)1)4NOH wherein R1May be selected from C1-C4Straight chain alkyl of (2) and C3-C4At least one of the branched alkyl groups of (2), e.g. R1And may be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl or methallyl. Preferably, R1Is n-propyl, i.e. the quaternary ammonium base compound is tetrapropyl quaternary ammonium base.
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 aliphatic amine compound may be R2(NH2)nWherein R is2Can be C1-C6Alkyl of (2), e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butylAlkyl, tert-butyl, n-pentyl or n-hexyl, R2May also be C1-C6For example methylene, ethylene, n-propylene, n-butylene or n-hexylene, 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 thereof.
In one embodiment, the alkanolamine compound may be (HOR)3)mNH(3-m)Wherein R is3Can be C1-C4M is an integer of 1, 2 or 3. For example, the alkanolamine compound is monoethanolamine, diethanolamine or triethanolamine, or a combination of two or three thereof.
According to the disclosure, in the steps b and c, the amount of the organic base may be 0.01 to 10.0mol, preferably 0.02 to 2.0mol, relative to 100g of the oxidation catalyst material; the using amount of the carbon dot solution can be 1-1000 g, and preferably 10-500 g; the amount of the water can be 0-10000 g, preferably 200-5000 g.
According to the present disclosure, the weight ratio of the carbon dot solution to the organic base may vary within a wide range, for example, the weight ratio of the carbon dot solution to the organic base may be 1: (0.1 to 1000), and in a preferred embodiment, the weight ratio of the carbon dot solution to the organic base may be 1: (0.5 to 500).
In step c, the oxidation catalyst material is known to those skilled in the art, i.e., the catalyst material in the oxidation reaction can be applied, and the oxidation catalyst material can be, but is not limited to, a titanium-containing molecular sieve, an iron-containing molecular sieve, a vanadium-containing molecular sieve or a tin-containing molecular sieve, or a combination of two or three of them.
According to the present disclosure, in step d, the hydrothermal reaction may be carried out in a conventional reactor, for example, in a polytetrafluoroethylene reaction kettle. The pressure of the hydrothermal reaction process is not particularly limited, and may be the autogenous pressure of the system, or may be under an additional applied pressure condition, and preferably, the hydrothermal reaction process is performed under the autogenous pressure (generally, in a closed vessel). The method of collecting the solid product after the hydrothermal reaction may be carried out by a conventional method such as filtration, centrifugation and the like. The conditions for drying and calcining the solid product may be conventional in the art, for example, the calcining conditions may include: the temperature is 300-800 ℃, and preferably 350-650 ℃; the time is 0.1 to 12 hours, preferably 1 to 8 hours.
In a second aspect of the present disclosure: there is provided a modified oxidative catalytic material prepared by the method of the first aspect of the present disclosure.
The modified oxidation catalytic material disclosed by the invention can be used as a catalyst for catalyzing the hydroxylation reaction of phenol, can realize the catalysis of phenol under mild conditions, and has higher raw material conversion rate and higher selectivity of a target product, namely hydroquinone.
In the hydroxylation reaction of catalytic oxidation phenol, the economic value of a target product hydroquinone is obviously higher than that of catechol, however, when a conventional catalyst is applied, the catechol is generally more than the hydroquinone in the product distribution, 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 only by adjusting the structure or the shape of the same type of catalyst, generally the selectivity of the hydroquinone is improved by less than 5 percent, and in most cases, the selectivity of the hydroquinone is improved by less than 2 percent. The oxidation catalysis material is treated by utilizing the carbon dots and the organic base, so that the quantity of reaction active centers of the oxidation catalysis material is favorably increased, more porous structures such as holes or defects are introduced in the process, the diffusion of reactant molecules is promoted, the distribution of the active centers is improved, the improvement of the catalysis performance of the modified oxidation catalysis material is favorably realized, and the selectivity of hydroquinone in a product is obviously improved. The modified oxidation catalysis material has excellent catalytic activity, stability and repeatability for the hydroxylation reaction of phenol.
The following examples will further illustrate the present disclosure, but are not intended to limit the same.
Examples 1-6 are provided to illustrate the modified oxidation catalyst materials of the present disclosure and methods of making the same.
In the preparation examples, the mesoporous specific surface area was calculated by the BJH method using a nitrogen adsorption capacity method (see petrochemical analysis method (RIPP test method), RIPP151-90, scientific Press, 1990).
Example 1
The oxidation catalyst material in this example is a titanium-containing molecular sieve, i.e., titanium silicalite TS-1 (prepared as described in Thangaraj A, Eapen M J, Sivasanker S, et al. Studies on the synthesis of titanium silicalite, TS-1[ J ] Zeolite, 1992,12(8): 943-950).
500mL of a glass having a resistivity of 18 M.OMEGA.cm was added to a beaker-1Placing an anode graphite rod (with the diameter of 10mm and the length of 30cm) and a cathode graphite rod (with the diameter of 10mm and the length of 30cm) in the ultrapure water, keeping the distance between the anode graphite rod and the cathode graphite rod at 10cm, connecting the anode graphite rod with the positive pole of a direct current power supply and connecting the cathode graphite rod with the negative pole 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 the carbon dot concentration of 0.5 mg/mL; mixing the carbon dot solution with an aqueous solution containing tetrapropylammonium hydroxide to obtain a first mixture, wherein the proportion of the first mixture is the carbon dot solution (g): tetrapropylammonium hydroxide (mol): water (g) ═ 20: 0.2: 600 and then mixing the first mixture with an oxidation catalyst material, wherein the weight ratio of the carbon dot solution to the oxidation catalyst material in the first mixture is 20: 100, transferring the obtained second mixture into a hydrothermal kettle, carrying out hydrothermal reaction for 48 hours at 150 ℃ under the autogenous pressure, collecting a solid product, washing with deionized water, naturally drying, and roasting at 550 ℃ for 3 hours to obtain the modified oxidation catalytic material C1. The mesoporous specific surface area accounts for 38 percent of the total specific surface area by detection, which shows that the mesoporous silicon dioxide has rich mesoporous structure.
Example 2
The oxidation catalyst material in this example was the same titanium-containing molecular sieve TS-1 as in example 1.
1500mL of a glass beaker with a resistivity of 18 M.OMEGA.cm was added-1The positive electrode graphite rod (diameter 8mm and length 50cm) and the negative electrode graphite rod (diameter 8mm and length 50cm) were placed in the ultrapure water of (4), and the positive electrode was heldThe distance between the anode graphite rod and the cathode graphite rod is 30cm, the anode graphite rod is connected with the positive pole of a direct current power supply, the cathode graphite rod is connected with the negative pole of the direct current power supply, 50V voltage is applied for electrolysis for 8 days, and the obtained electrolyte after electrolysis is concentrated to obtain a carbon dot solution with the carbon dot concentration of 0.04 mg/mL; mixing the carbon dot solution with an aqueous solution containing tetraethylammonium bromide to obtain a first mixture, wherein the proportion of the first mixture is the carbon dot solution (g): tetraethylammonium bromide (mol): water (g) ═ 20: 0.2: 600 and then mixing the first mixture with an oxidation catalyst material, wherein the weight ratio of the carbon dot solution to the oxidation catalyst material in the first mixture is 20: 100, transferring the obtained second mixture into a hydrothermal kettle, carrying out hydrothermal reaction for 48 hours at 150 ℃ under the autogenous pressure, collecting a solid product, washing with deionized water, naturally drying, and roasting at 550 ℃ for 3 hours to obtain the modified oxidation catalytic material C1. The detection shows that the mesoporous specific surface area accounts for 35 percent of the total specific surface area, which indicates that the mesoporous silicon dioxide has rich mesoporous structure.
Example 3
The oxidation catalyst material in this example was the same titanium-containing molecular sieve TS-1 as in example 1.
500mL of a glass having a resistivity of 18 M.OMEGA.cm was added to a beaker-1Placing an anode graphite rod (with the diameter of 20mm and the length of 30cm) and a cathode graphite rod (with the diameter of 20mm and the length of 30cm) in the ultrapure water, keeping the distance between the anode graphite rod and the cathode graphite rod at 10cm, connecting the anode graphite rod with the positive pole of a direct current power supply and connecting the cathode graphite rod with the negative pole of the direct current power supply, applying a voltage of 30V for electrolysis for 5 days, and concentrating the obtained electrolyzed electrolyte to obtain a carbon dot solution with the carbon dot concentration of 6.0 mg/mL; mixing the carbon dot solution with an aqueous solution containing ethylenediamine to obtain a first mixture, wherein the carbon dot solution (g) is prepared from the following components in parts by weight: ethylenediamine (mole): water (g) ═ 20: 0.2: 600 and then mixing the first mixture with an oxidation catalyst material, wherein the weight ratio of the carbon dot solution to the oxidation catalyst material in the first mixture is 20: 100, transferring the obtained second mixture into a hydrothermal kettle, carrying out hydrothermal reaction for 48 hours at the temperature of 150 ℃ under the autogenous pressure, and collecting the solid productAnd washing the material with deionized water, naturally drying, and roasting at 350 ℃ for 8h to obtain the modified oxidation catalytic material C1. The detection shows that the mesoporous specific surface area accounts for 36 percent of the total specific surface area, which indicates that the mesoporous silicon dioxide has rich mesoporous structure.
Example 4
The oxidation catalyst material in this example was the same titanium-containing molecular sieve TS-1 as in example 1.
500mL of a glass having a resistivity of 18 M.OMEGA.cm was added to a beaker-1Placing an anode graphite rod (with the diameter of 10mm and the length of 30cm) and a cathode graphite rod (with the diameter of 10mm and the length of 30cm) in the ultrapure water, keeping the distance between the anode graphite rod and the cathode graphite rod at 10cm, connecting the anode graphite rod with the positive pole of a direct current power supply and connecting the cathode graphite rod with the negative pole 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 the carbon dot concentration of 0.5 mg/mL; mixing the carbon dot solution with an aqueous solution containing tetrapropylammonium hydroxide to obtain a first mixture, wherein the proportion of the first mixture is the carbon dot solution (g): tetrapropylammonium hydroxide (mol): water (g) 10: 0.02: 500 and then mixing the first mixture with an oxidation catalyst material, wherein the weight ratio of the carbon dot solution to the oxidation catalyst material in the first mixture is 10: 100, transferring the obtained second mixture into a hydrothermal kettle, carrying out hydrothermal reaction for 48 hours at 150 ℃ under the autogenous pressure, collecting a solid product, washing with deionized water, naturally drying, and roasting at 650 ℃ for 1 hour to obtain the modified oxidation catalytic material C1. The detection shows that the mesoporous specific surface area accounts for 34 percent of the total specific surface area, which indicates that the mesoporous silicon dioxide has rich mesoporous structure.
Example 5
The oxidation catalyst material in this example was the same titanium-containing molecular sieve TS-1 as in example 1.
500mL of a glass having a resistivity of 18 M.OMEGA.cm was added to a beaker-1The positive electrode graphite rod (diameter 10mm and length 30cm) and the negative electrode graphite rod (diameter 10mm and length 30cm) are placed in the ultrapure water, the distance between the positive electrode graphite rod and the negative electrode graphite rod is kept at 30cm, the positive electrode graphite rod is connected with the positive electrode of a direct current power supply, and the negative electrode graphite rod is connected with the negative electrode of the direct current power supplyApplying a voltage of 50V to carry out electrolysis for 8 days, and concentrating the obtained electrolyzed electrolyte to obtain a carbon dot solution with the carbon dot concentration of 0.5 mg/mL; mixing the carbon dot solution with an aqueous solution containing tetrapropylammonium hydroxide to obtain a first mixture, wherein the proportion of the first mixture is the carbon dot solution (g): tetrapropylammonium hydroxide (mol): water (g) 500: 2.0: 200 and then mixing the first mixture with an oxidation catalyst material, wherein the weight ratio of the carbon dot solution to the oxidation catalyst material in the first mixture is 500: 100, transferring the obtained second mixture into a hydrothermal kettle, carrying out hydrothermal reaction for 48 hours at 150 ℃ and 2.0MPa, collecting a solid product, washing with deionized water, naturally drying, and roasting at 550 ℃ for 3 hours to obtain the modified oxidation catalytic material C1. The detection shows that the mesoporous specific surface area accounts for 29 percent of the total specific surface area, which indicates that the mesoporous silicon dioxide has rich mesoporous structure.
Example 6
The oxidation catalyst material in this example was an untreated tin-containing molecular sieve, i.e., the tin-silicon molecular sieve Sn-MFI (prepared as described in Mal N K, Ramasumamy V, Rajamohan P R, et al. Sn-MFI molecular sieves: synthesis methods,29Si liquid and solid MAS-NMR,119Sn static and MAS NMR students [ J ]. microporosius materials,1997,12(4-6): 331-340).
500mL of a glass having a resistivity of 18 M.OMEGA.cm was added to a beaker-1Placing an anode graphite rod (with the diameter of 10mm and the length of 30cm) and a cathode graphite rod (with the diameter of 10mm and the length of 30cm) in the ultrapure water, keeping the distance between the anode graphite rod and the cathode graphite rod at 10cm, connecting the anode graphite rod with the positive pole of a direct current power supply and connecting the cathode graphite rod with the negative pole 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 the carbon dot concentration of 0.5 mg/mL; mixing the carbon dot solution with an aqueous solution containing tetrapropylammonium hydroxide to obtain a first mixture, wherein the proportion of the first mixture is the carbon dot solution (g): tetrapropylammonium hydroxide (mol): water (g) ═ 5: 0.5: 1000 and then mixing the first mixture with an oxidation catalyst material, wherein the weight ratio of the carbon dot solution to the oxidation catalyst material in the first mixture is 100: 5, mixing the raw materialsAnd transferring the obtained second mixture into a hydrothermal kettle, carrying out hydrothermal reaction for 48h at 150 ℃ under the autogenous pressure, collecting a solid product, washing with deionized water, naturally drying, and roasting at 550 ℃ for 3h to obtain the modified oxidation catalytic material C1. The detection shows that the mesoporous specific surface area accounts for 31 percent of the total specific surface area, which indicates that the mesoporous silicon dioxide has rich mesoporous structure.
Comparative example 1
The oxidation catalyst material in this example was an untreated titanium-containing molecular sieve, i.e., titanium silicalite TS-1 (prepared as described in Thangaraj A, Eaen M J, Sivasaker S, et al. Studies on the synthesis of titanium silicalite, TS-1[ J ] Zeolite, 1992,12(8): 943-950) as a comparison, and was prepared as follows:
tetraethyl orthosilicate (22.5 g) was mixed with tetrapropylammonium hydroxide (7.0 g) as a template agent at room temperature, and then 59.8g of distilled water was added thereto, followed by stirring and mixing, followed by hydrolysis at 60 ℃ for 1 hour to obtain a hydrolysis solution of tetraethyl orthosilicate. To the hydrolysis solution was slowly added a solution consisting of 1.1g tetrabutyl titanate and 5.0g anhydrous isopropanol with vigorous stirring, and the resulting mixture was stirred at 75 ℃ for 3h to give a clear and transparent colloid. Placing the colloid in a stainless steel sealed reaction kettle, and standing at a constant temperature of 170 ℃ for 72h to obtain a mixture of crystallized products. And filtering the obtained mixture, collecting a solid product, washing the solid product with water, drying the solid product at 110 ℃ for 60min, and roasting the solid product at 500 ℃ for 3h to obtain the titanium silicalite TS-1, namely the unmodified oxidation catalytic material D1. The mesoporous specific surface area accounts for 7 percent of the total specific surface area by detection, which shows that the mesoporous structure is less.
Comparative example 2
The oxidation catalyst material in this example is a titanium-containing molecular sieve, i.e., titanium silicalite TS-1 (prepared as described in Thangaraj A, Eapen M J, Sivasanker S, et al. Studies on the synthesis of titanium silicalite, TS-1[ J ] Zeolite, 1992,12(8): 943-950).
500mL of a glass having a resistivity of 18 M.OMEGA.cm was added to a beaker-1The positive electrode graphite rod (diameter 10mm and length 30cm) and the negative electrode graphite rod (diameter 10mm and length 30cm) were placed in the ultrapure water of (4), and the positive electrode graphite rod was heldThe distance between the anode graphite rod and the cathode graphite rod is 10cm, the anode graphite rod is connected with the positive pole of a direct current power supply, the cathode graphite rod is connected with the negative pole of the direct current power supply, 50V voltage is applied for electrolysis for 8 days, and the obtained electrolyte after electrolysis is concentrated to obtain a carbon dot solution with the carbon dot concentration of 0.5 mg/mL; mixing the carbon dot solution with an oxidation catalytic material, wherein the weight ratio of the carbon dot solution to the oxidation catalytic material is 20: 100, transferring the obtained mixture into a hydrothermal kettle, carrying out hydrothermal reaction for 48h at 150 ℃ under the autogenous pressure, collecting a solid product, washing with deionized water, naturally drying, and roasting for 3h at 550 ℃ to obtain a comparative oxidation catalytic material D2. The detection shows that the specific surface area of the mesopores accounts for 11 percent of the total specific surface area, which indicates that the mesopores have fewer structures.
Comparative example 3
The oxidation catalyst material in this example is a titanium-containing molecular sieve, i.e., titanium silicalite TS-1 (prepared as described in Thangaraj A, Eapen M J, Sivasanker S, et al. Studies on the synthesis of titanium silicalite, TS-1[ J ] Zeolite, 1992,12(8): 943-950).
Mixing an aqueous solution containing tetrapropylammonium hydroxide with an oxidation catalyst material to obtain a mixture, wherein the ratio of tetrapropylammonium hydroxide (mol): water (g): oxidation catalytic material (g) ═ 0.2: 600: 100, transferring the obtained mixture into a hydrothermal kettle, carrying out hydrothermal reaction for 48h at 150 ℃ under the autogenous pressure, collecting a solid product, washing with deionized water, naturally drying, and roasting for 3h at 550 ℃ to obtain a comparative oxidation catalytic material D3. The mesoporous specific surface area accounts for 19 percent of the total specific surface area by detection, which shows that the mesoporous structure is less.
Test example 1
The modified oxidation catalytic materials C1-C6 obtained in examples 1-6 and the samples D1-D3 obtained by the method of the comparative example are used as fresh catalysts for the catalytic effect of the hydroxylation reaction of phenol.
The hydroxylation reaction of phenol is carried out in a 250ml three-mouth bottle reaction device with an automatic temperature control water bath, magnetic stirring and condensation reflux system. Carrying out the following steps of mixing a modified oxidation catalytic material, acetone serving as a solvent and phenol according to a weight ratio of 1: 20: 16, sequentially adding the mixture into a three-neck bottle, putting the three-neck bottle into a water bath kettle with the preset reaction temperature of 80 ℃, and slowly adding hydrogen peroxide (the mass fraction is 30%) into a reaction system, wherein the molar ratio of the hydrogen peroxide to the phenol is 0.39: 1, after the reaction was completed for 2 hours, the reaction was stopped by cooling, and the reaction results are shown in Table 1.
The reaction product was analyzed by gas chromatography (GC: Agilent, 7890A) and gas chromatography-mass spectrometer (GC-MS: Thermo Fisher Trace ISQ). Conditions of gas chromatography: nitrogen carrier gas, temperature programmed at 140K: 60 ℃,1 minute, 15 ℃/minute, 180 ℃, 15 minutes; split ratio, 10: 1; the injection port temperature is 300 ℃; detector temperature, 300 ℃. On the basis, the conversion rate of raw materials and the selectivity of target products are calculated by respectively adopting the following formulas:
phenol conversion (%)% of phenol (molar amount of phenol added before reaction-molar amount of phenol remaining after reaction)/molar amount of phenol added before reaction × 100%;
the selectivity% for hydroquinone (molar amount of hydroquinone formed after the reaction)/the molar amount of phenol added before the reaction × 100%.
TABLE 1
| Sources of catalyst | Phenol conversion rate,% | Selectivity for hydroquinone,% |
| Example 1 | 24.7 | 63 |
| Example 2 | 23.5 | 59 |
| Example 3 | 24.5 | 61 |
| Example 4 | 23.5 | 57 |
| Example 5 | 23.2 | 54 |
| Example 6 | 22.5 | 56 |
| Comparative example 1 | 17.5 | 47 |
| Comparative example 2 | 19.3 | 49 |
| Comparative example 3 | 18.2 | 47 |
As can be seen from table 1, the present disclosure adopts a specific modified oxidation catalyst material as a catalyst to catalyze the hydroxylation reaction of phenol, which can realize the selective catalysis of phenol under mild conditions, and has high conversion rate of raw materials and high selectivity of hydroquinone as a target product. Further comparison results show that the modified oxidation catalytic material disclosed by the disclosure has excellent catalytic performance in the hydroxylation reaction of phenol, and under the condition that the preferable mesoporous specific surface area accounts for not less than 25% of the total specific surface area, the activity of the catalyst can be further improved, the conversion rate of phenol and the selectivity of a target product hydroquinone can be further improved, and the subsequent separation energy consumption is reduced.
Test example 2
The modified oxidation catalyst materials C1-C6 obtained in examples 1-6 and the samples D1-D3 obtained by the method of the comparative example are used as the recovered catalyst after being repeatedly used for the catalytic effect of the hydroxylation reaction of phenol.
The catalytic reaction conditions of phenol were the same as in test example 1, except that the catalyst used was a recovered catalyst. The catalyst reacted in test example 1 was washed with water and dried, and then used again for the above-mentioned catalytic reaction of phenol, and after 6 times of such recycling, the obtained nanomaterial was used as a recovered catalyst for the above-mentioned hydroxylation reaction of phenol, and the reaction results are listed in table 2.
TABLE 2
| Sources of catalyst | Phenol conversion rate,% | Selectivity for hydroquinone,% |
| Example 1 | 24.1 | 65 |
| Example 2 | 23.0 | 62 |
| Example 3 | 24.2 | 61 |
| Example 4 | 23.1 | 59 |
| Example 5 | 22.8 | 57 |
| Example 6 | 22.0 | 58 |
| Comparative example 1 | 11.3 | 45 |
| Comparative example 2 | 12.6 | 48 |
| Comparative example 3 | 15.1 | 47 |
As can be seen from table 2, the modified oxidation catalytic material of the present disclosure can still maintain excellent catalytic activity after repeated use for many times, and surprisingly, the selectivity of the target product hydroquinone is still slightly improved, the catalytic activity of the sample in the comparative example is obviously reduced, and the selectivity of the target product hydroquinone is not changed or even slightly reduced, which indicates that the modified oxidation catalytic material of the present disclosure has good stability and reusability.
The preferred embodiments of the present disclosure have been described in detail above, however, the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present disclosure within the technical idea of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.
It should be noted that, in the foregoing embodiments, various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various combinations that are possible in the present disclosure are not described again.
In addition, any combination of various embodiments of the present disclosure may be made, and the same should be considered as the disclosure of the present disclosure, as long as it does not depart from the spirit of the present disclosure.
Claims (10)
1. A method of modifying an oxidation catalyst material, the method comprising the steps of:
a. connecting a first conductive object with the positive electrode of a direct current power supply, connecting a second conductive object with the negative electrode of the direct current power supply, putting the second conductive object into an electrolyte, applying a voltage of 0.1-110V, preferably 5-80V, to electrolyze for 1-30 days, preferably 5-15 days, and concentrating the obtained electrolyzed electrolyte to obtain a carbon dot solution, wherein the first conductive object is a graphite rod;
b. mixing the carbon dot solution obtained in step a with an organic base and optionally water to obtain a first mixture;
c. mixing the first mixture obtained in the step b with an oxidation catalyst material to obtain a second mixture;
d. and c, carrying out hydrothermal treatment on the second mixture obtained in the step c at 80-200 ℃ for 2-360 h, collecting a solid product, washing, drying and roasting to obtain the modified oxidation catalysis material.
2. The method according to claim 1, wherein in the step a, the diameter of the graphite rod is 2-20 mm, and the length of the graphite rod is 2-100 cm; and/or the presence of a gas in the gas,
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 first conductive material in size.
3. The method according to claim 1, wherein in step a, the electrolyzed electrolyte is an aqueous solution having a water content of 85 wt% or more; and/or
The carbon dot concentration of the carbon dot solution is 0.01-5 mg/mL, preferably 0.05-1 mg/mL.
4. The method according to claim 1, wherein in step b, the organic base is urea, a quaternary ammonium base compound, a quaternary ammonium salt compound, a fatty amine compound or an alcohol amine compound, or a combination of two or three thereof.
5. The method according to claim 4, wherein in step b, 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 tetraethylammonium chloride, the tetraethylammonium bromide, the tetrapropylammonium chloride and the tetrabutylammonium bromide;
the aliphatic amine compound is ethylamine, n-butylamine, butanediamine or hexanediamine, or a combination of two or three of the ethylamine, the n-butylamine, the butanediamine and the hexanediamine;
the alcohol amine compound is monoethanolamine, diethanolamine or triethanolamine, or a combination of two or three of the monoethanolamine, diethanolamine and triethanolamine.
6. The method according to claim 1, wherein the organic base is used in an amount of 0.01 to 10.0mol, preferably 0.02 to 2.0mol, relative to 100g of the oxidation catalyst material in steps b and c; the using amount of the carbon dot solution is 1-1000 g, preferably 10-500 g; the amount of the water is 0-10000 g, preferably 200-5000 g.
7. The method of claim 1, wherein in step b, the weight ratio of the carbon dot solution to the organic base is 1: (0.1 to 1000), preferably 1: (0.5 to 500).
8. The method of claim 1, wherein in step c, the oxidative catalytic material is a titanium-containing molecular sieve, an iron-containing molecular sieve, a vanadium-containing molecular sieve, or a tin-containing molecular sieve, or a combination of two or three thereof.
9. The method of claim 1, wherein in step d, the firing conditions comprise: the temperature is 300-800 ℃, preferably 350-650 ℃; the time is 0.1 to 12 hours, preferably 1 to 8 hours.
10. A modified oxidative catalytic material prepared by the method of any one of claims 1 to 9.
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