Nano material and preparation method thereof, and catalytic oxidation method of cycloparaffin
阅读说明：本技术 一种纳米材料及其制备方法和环烷烃的催化氧化方法 (Nano material and preparation method thereof, and catalytic oxidation method of cycloparaffin ) 是由 史春风 康振辉 刘阳 周赟杰 王肖 孙悦 黄慧 蔺晓玲 于 2020-03-31 设计创作，主要内容包括：本发明涉及一种制备纳米材料的方法,该方法包括：将硝酸铋、钒酸铵和酸溶液混合,得到第一混合物,在耐热密闭反应器中,使第一混合物与第一碱溶液在150-250℃下反应10-120小时,去除溶剂,得到第一固体；将第一导电物和第二导电物分别与直流电源的正极和负极连接后置于电解液中,在2-50V的电压下电解1-15天,得到碳点溶液；其中,第一导电物为石墨棒,电解液含有第一无机酸；将碳点溶液、镍盐、第二碱溶液和第一固体混合,得到第二混合物；将第二混合物进行冷冻干燥处理后,再进行真空干燥。本发明的方法可以制备得到具有良好的催化性能的纳米材料,将其用于环烷烃的催化氧化过程,环烷烃的转化率和目的产物的转化率高。(The invention relates to a method for preparing a nano material, which comprises the following steps: mixing bismuth nitrate, ammonium vanadate and an acid solution to obtain a first mixture, reacting the first mixture with a first alkali solution in a heat-resistant closed reactor at the temperature of 150-250 ℃ for 10-120 hours, and removing a solvent to obtain a first solid; respectively connecting the first conductive substance and the second conductive substance with the anode and the cathode of a direct current power supply, placing the two conductive substances into an electrolyte, and electrolyzing for 1-15 days under the voltage of 2-50V to obtain a carbon dot solution; wherein the first conductor is a graphite rod, and the electrolyte contains a first inorganic acid; mixing the carbon dot solution, the nickel salt, the second alkali solution and the first solid to obtain a second mixture; the second mixture was freeze-dried and then vacuum-dried. The method can prepare the nano material with good catalytic performance, and the nano material is used in the catalytic oxidation process of the cycloalkane, so that the conversion rate of the cycloalkane and the conversion rate of the target product are high.)
1. A method of preparing a nanomaterial, the method comprising:
(1) mixing bismuth nitrate, ammonium vanadate and an acid solution to obtain a first mixture, reacting the first mixture with a first alkali solution in a heat-resistant closed reactor at the temperature of 150-250 ℃ for 10-120 hours, and removing a solvent to obtain a first solid;
(2) respectively connecting the first conductive object and the second conductive object with the anode and the cathode of a direct current power supply, placing the connected objects in an electrolyte, and electrolyzing for 1-15 days under the voltage of 2-50V to obtain a carbon dot solution; wherein the first conductor is a graphite rod, and the electrolyte contains a first inorganic acid;
(3) mixing the carbon dot solution, the nickel salt, the second alkali solution and the first solid to obtain a second mixture;
(4) and after the second mixture is subjected to freeze drying treatment, carrying out vacuum drying.
2. The method according to claim 1, wherein in step (1), the bismuth nitrate, the ammonium vanadate, the acid solution and the first alkali solution are used in a mass ratio of 1: (0.1-5): (0.1-2): (0.1-2), the acid solution is counted by acid, and the alkali solution is counted by alkali.
3. The method according to claim 1, wherein in step (2), the concentration of the first inorganic acid in the electrolyte is 0.1 to 5% by weight, based on the total weight of the electrolyte; the first inorganic acid is selected from one or more of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid and perchloric acid.
4. The method of claim 1, wherein step (3) comprises: and mixing the carbon dot solution and the nickel salt, dropwise adding the second alkali solution, and mixing and stirring the obtained mixed solution and the first solid to obtain the second mixture.
5. The method according to claim 1 or 4, wherein in step (3), the carbon dot solution, the nickel salt, the second alkali solution and the first solid are used in a weight ratio of 100: (2-100): (10-500): (5-100).
6. The method of claim 1, wherein step (4) comprises: sequentially carrying out first vacuum drying and second vacuum drying on the freeze-dried solid;
the first vacuum drying is carried out at the temperature of 20-100 ℃ for 5-25 hours at the vacuum degree of 10-1000 Pa; the temperature of the second vacuum drying is 300-500 ℃, the time is 1-6 hours, and the vacuum degree is 100-5000 Pa.
7. The method of claim 1, wherein the freeze-drying is at a temperature of from-50 ℃ to-5 ℃ for a period of from 1 to 72 hours under a vacuum of from 10 to 1000 Pa.
8. The process according to claim 1, wherein the nickel salt is selected from organic and/or inorganic nickel salts; the inorganic nickel salt is selected from one or more of nickel nitrate, nickel phosphate, nickel chloride and nickel sulfate; the organic nickel salt is nickel acetate and/or nickel citrate;
the acid solution contains a second inorganic acid and/or a second organic acid, the second inorganic acid is selected from one or more of nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid and perchloric acid, and the second organic acid is selected from one or more of formic acid, acetic acid, citric acid and ascorbic acid;
the first alkali solution and the second alkali solution are respectively and independently selected from one or more of ammonia water, urea aqueous solution and hydrazine hydrate.
9. The process of claim 1, wherein the graphite rod is 2-20mm in diameter and 2-100cm in length; the second conductive object is an iron rod, an iron plate, a graphite rod, a graphite plate, a copper plate or a copper rod.
10. A nanomaterial produced by the method of any one of claims 1 to 9.
11. A process for the catalytic oxidation of a cycloalkane, the process comprising: contacting a cycloalkane with an oxidizing agent in the presence of a catalyst to effect an oxidation reaction, said catalyst comprising the nanomaterial of claim 10.
12. The method of claim 11, wherein the oxidation reaction conditions comprise: the temperature is 50-200 ℃, the pressure is 0-20MPa, and the time is 1-72 hours.
13. The process of claim 11, wherein the oxidant is an oxygen-containing gas, the oxygen concentration of the oxygen-containing gas is greater than 10% by volume, the molar ratio of oxygen in the oxygen-containing gas to the cycloalkanes is greater than 1;
the weight ratio of the cycloalkane to the catalyst is 100: (5-100).
14. The method of claim 11, wherein the cycloalkane is a C5-C12 monocycloparaffin and/or a C8-C16 bicycloalkane.
Technical Field
The invention relates to a nano material and a preparation method thereof, and a catalytic oxidation method of cycloalkane.
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 also 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 with the size less than 10nm discovered when the single-layer carbon nano-tube is purified by an electrophoresis method are firstly named as carbon quantum dots (carbon dots for short) and are a novel small-size carbon nano-material. Carbon quantum dots are also referred to as fluorescent carbon quantum dots (FCDs) because of their excellent fluorescent properties. From their discovery to the short years of utilization, FCDs have become a new star of the carbon nanofamily. Compared to organic dyes and conventional semiconductor Quantum Dots (QDs), FCDs have unique optical and electrical properties in addition to good water solubility, high stability, low toxicity and good biocompatibility. Therefore, much attention has been paid to the study of the properties and utilization of FCDs. A series of high-activity composite catalytic materials are designed in a subject group, so that the absorption of the composite materials to light is enhanced, and the catalytic efficiency of the reaction is effectively improved.
The oxidation catalysis material can adopt pollution-free low-concentration hydrogen peroxide as an oxidant in the oxidation reaction of organic matters, can catalyze various types of organic oxidation reactions, such as olefin epoxidation, alkane partial oxidation, alcohol oxidation, phenol hydroxylation and the like, avoids the problems of complex oxidation process and environmental pollution, has the advantages of incomparable energy conservation, economy, environmental friendliness and the like of a traditional oxidation system, and has good reaction selectivity, so that the oxidation catalysis material has great industrial utilization prospect. But the repeatability, stability, cost and the like of the existing synthesis method of the oxidation catalytic material are not ideal. Therefore, the development of the oxidation catalyst material is key to the improvement of the corresponding synthesis method.
The combination of the carbon nanomaterial and the improvement of the oxidation catalyst material can produce unexpected technical effects on the catalytic performance of the oxidation catalyst material.
Disclosure of Invention
The invention aims to provide a nano material and a preparation method thereof and a catalytic oxidation method of cyclic hydrocarbon.
In order to achieve the above object, a first aspect of the present invention provides a method for preparing a nanomaterial, the method comprising:
(1) mixing bismuth nitrate, ammonium vanadate and an acid solution to obtain a first mixture, reacting the first mixture with a first alkali solution in a heat-resistant closed reactor at the temperature of 150-250 ℃ for 10-120 hours, and removing a solvent to obtain a first solid;
(2) respectively connecting the first conductive object and the second conductive object with the anode and the cathode of a direct current power supply, placing the connected objects in an electrolyte, and electrolyzing for 1-15 days under the voltage of 2-50V to obtain a carbon dot solution; wherein the first conductor is a graphite rod, and the electrolyte contains a first inorganic acid;
(3) mixing the carbon dot solution, the nickel salt, the second alkali solution and the first solid to obtain a second mixture;
(4) and after the second mixture is subjected to freeze drying treatment, carrying out vacuum drying. In the step (1), the mass ratio of the bismuth nitrate to the ammonium vanadate to the acid solution to the first alkali solution is 1: (0.1-5): (0.1-2): (0.1-2), the acid solution is counted by acid, and the alkali solution is counted by alkali.
Optionally, in the step (2), the concentration of the first inorganic acid in the electrolyte is 0.1-5 wt% based on the total weight of the electrolyte; the first inorganic acid is selected from one or more of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid and perchloric acid.
Optionally, step (3) comprises: and mixing the carbon dot solution and the nickel salt, dropwise adding the second alkali solution, and mixing and stirring the obtained mixed solution and the first solid to obtain the second mixture.
Optionally, in the step (3), the carbon dot solution, the nickel salt, the second alkali solution and the first solid are used in a weight ratio of 100: (2-100): (10-500): (5-100).
Optionally, step (4) comprises: sequentially carrying out first vacuum drying and second vacuum drying on the freeze-dried solid;
the first vacuum drying is carried out at the temperature of 20-100 ℃ for 5-25 hours at the vacuum degree of 10-1000 Pa; the temperature of the second vacuum drying is 300-500 ℃, the time is 1-6 hours, and the vacuum degree is 100-5000 Pa.
Optionally, the freeze drying temperature is 50-5 deg.C below zero, the time is 1-72 hr, and the vacuum degree is 10-1000 Pa.
Optionally, the nickel salt is selected from an organic nickel salt and/or an inorganic nickel salt; the inorganic nickel salt is selected from one or more of nickel nitrate, nickel phosphate, nickel chloride and nickel sulfate; the organic nickel salt is nickel acetate and/or nickel citrate;
the acid solution contains a second inorganic acid and/or a second organic acid, the second inorganic acid is selected from one or more of nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid and perchloric acid, and the second organic acid is selected from one or more of formic acid, acetic acid, citric acid and ascorbic acid;
the first alkali solution and the second alkali solution are respectively and independently selected from one or more of ammonia water, urea aqueous solution and hydrazine hydrate.
Optionally, the graphite rod has a diameter of 2-20mm and a length of 2-100 cm; the second conductive object is an iron rod, an iron plate, a graphite rod, a graphite plate, a copper plate or a copper rod.
In a second aspect, the present invention provides a nanomaterial prepared by the method provided in the first aspect of the present invention.
In a third aspect, the present invention provides a process for the catalytic oxidation of a cycloalkane, the process comprising: the oxidation reaction is carried out by contacting a cycloalkane with an oxidant in the presence of a catalyst comprising a nanomaterial provided by the second aspect of the present invention.
Optionally, the conditions of the oxidation reaction include: the temperature is 50-200 ℃, the pressure is 0-20MPa, and the time is 1-72 hours.
Optionally, the oxidant is an oxygen-containing gas, the oxygen concentration of the oxygen-containing gas is greater than 10% by volume, and the molar ratio of oxygen in the oxygen-containing gas to the cycloalkanes is greater than 1;
the weight ratio of the cycloalkane to the catalyst is 100: (5-100).
Optionally, the cycloalkane is a C5-C12 monocycloparaffin and/or a C8-C16 bicycloalkane.
Through the technical scheme, when the nano material prepared by the method is used for catalytic reaction of cycloalkane, selective oxidation of cycloalkane can be realized under mild conditions, the conversion rate of raw materials and the selectivity of target products are high, and especially the selectivity of acids is high.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
In a first aspect, the present invention provides a method for preparing a nanomaterial, the method comprising:
(1) mixing bismuth nitrate, ammonium vanadate and an acid solution to obtain a first mixture, reacting the first mixture with a first alkali solution in a heat-resistant closed reactor at the temperature of 150-250 ℃ for 10-120 hours, and removing a solvent to obtain a first solid;
(2) respectively connecting the first conductive object and the second conductive object with the anode and the cathode of a direct current power supply, placing the connected objects in an electrolyte, and electrolyzing for 1-15 days under the voltage of 2-50V to obtain a carbon dot solution; wherein the first conductor is a graphite rod, and the electrolyte contains a first inorganic acid;
(3) mixing the carbon dot solution, the nickel salt, the second alkali solution and the first solid to obtain a second mixture;
(4) and freeze-drying the second mixture, and then carrying out vacuum drying.
According to the present invention, the kind of the heat-resistant closed reactor is not particularly limited, and may be, for example, a high-pressure reactor. The nano material prepared by the method has good catalytic performance, and when the nano material is used for catalytic oxidation reaction of cycloalkane, the conversion rate of cycloalkane is high, the conversion rate of a target product is high, and particularly the selectivity of acids is high.
In one embodiment, step (1) comprises: and centrifuging and washing the reacted mixture, and then performing vacuum drying for 2-48 hours in a drying oven at the temperature of 20-100 ℃ to obtain a first solid. The liquid used for the washing is not particularly limited, and may be, for example, ethanol, deionized water, or the like.
According to the invention, in step (1), the mass ratio of the amounts of bismuth nitrate, ammonium vanadate, acid solution and first base solution used may vary within a wide range, preferably 1: (0.1-5): (0.1-2): (0.1-2), more preferably 1: (0.2-2): (0.2-1): (0.2-1), the acid solution is counted by acid, and the alkali solution is counted by alkali. In one embodiment, the acid solution may contain a second inorganic acid and/or a second organic acid, and the second inorganic acid may be a strong acid solution, for example, one or more of nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid and perchloric acid, and is preferably a nitric acid solution; the second organic acid may be one or more selected from formic acid, acetic acid, citric acid and ascorbic acid. The first alkali solution may be a weak alkali solution, and may be one or more of ammonia water, an aqueous solution of urea, and hydrazine hydrate, preferably ammonia water.
According to the present invention, in the step (2), the concentration of the first inorganic acid in the electrolyte may be 0.1 to 5% by weight, preferably 0.5 to 2.5% by weight, based on the total weight of the electrolyte; the first inorganic acid may be one or more selected from nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid and perchloric acid.
According to the present invention, the step (3) may include: and mixing the carbon dot solution and the nickel salt, dropwise adding a second alkali solution, and mixing and stirring the mixed solution and the first solid to obtain a second mixture. The time for dropping the second alkali solution is not particularly limited, and may be, for example, 1 to 60 min. In the step (3), the temperature and time of mixing are not particularly limited, and for example, mixing may be carried out at 10 to 60 ℃ for 1 to 120 min. In a preferred embodiment, after mixing the carbon dot solution and the nickel salt, slowly stirring and dropping the second alkali solution at 100-.
According to the invention, in step (3), the weight ratio of the amounts of the carbon dot solution, the nickel salt, the second base solution and the first solid used may vary within a wide range, and is preferably 100: (2-100): (10-500): (5-100), more preferably 100: (5-50): (20-200): (10-50). The second alkali solution can be one or more of ammonia water, urea and hydrazine hydrate, and is preferably ammonia water; the nickel salt can be organic nickel salt and/or inorganic nickel salt, the organic nickel salt can be nickel acetate and/or nickel citrate, the inorganic nickel salt is one or more selected from nickel nitrate, nickel phosphate, nickel chloride and nickel sulfate, and nickel nitrate is preferred.
According to the present invention, the step (4) may include: and sequentially carrying out primary vacuum drying and secondary vacuum drying on the solid subjected to freeze drying treatment. In a specific embodiment, the temperature of the first vacuum drying is 20-100 ℃, the time can be 5-25 hours, and the vacuum degree is 10-1000 Pa; the temperature of the second vacuum drying is 300-.
According to the present invention, lyophilization is well known to those skilled in the art, and the temperature of lyophilization may be from-50 ℃ to-5 ℃ for 1 to 72 hours, and the vacuum may be from 10 to 1000Pa, preferably, the temperature of lyophilization is from-40 ℃ to-10 ℃ for 6 to 48 hours, and the vacuum is from 20 to 200 Pa.
According to the present invention, the diameter and length of the graphite rod are not particularly limited, and in one embodiment, the graphite rod has a diameter of 2 to 20mm and a length of 2 to 100 cm. The second conductive material is not limited to a specific type, and may be any material that can conduct electricity, and may be, for example, a common rod or plate. Preferably, the second conductor is an iron rod, an iron plate, a graphite rod, a graphite plate, a copper plate, or a copper rod, more preferably an iron rod, a graphite rod, or a copper rod, and further preferably a graphite rod matching the size of the first conductor. During the electrolysis, the first and second conductors may be held at a distance which may vary within a relatively large range, for example 3-10 cm.
In a second aspect, the present invention provides a nanomaterial prepared by the method provided in the first aspect of the present invention.
In a third aspect, the present invention provides a process for the catalytic oxidation of a cycloalkane, the process comprising: the oxidation reaction is carried out by contacting cycloalkane with an oxidant in the presence of a catalyst comprising nanomaterial provided by the second aspect of the present invention.
The method can realize the catalytic oxidation of the cycloalkane under mild conditions, and has high conversion rate of the cycloalkane and high selectivity of target products, especially high selectivity of acids.
According to the present invention, the catalyst may also contain a catalyst for catalytic oxidation of alkane, which is conventionally used by those skilled in the art, and may be, for example, one or more of titanium silicalite, high-valence transition metal salt, transition metal oxide, heteropoly acid and heteropoly acid salt; the high-valence transition metal salt can be one or more of sodium tungstate, potassium vanadate, potassium permanganate and potassium dichromate, the transition metal oxide can be one or more of copper oxide, iron oxide, titanium oxide and zinc oxide, the heteropoly acid can be one or more of phosphotungstic heteropoly acid, phosphomolybdic heteropoly acid, silicotungstic heteropoly acid and silicomolybdic heteropoly acid, and the heteropoly acid salt can be one or more of phosphotungstic heteropoly acid sodium, phosphomolybdic heteropoly acid potassium and phosphotungstic heteropoly acid cesium. In a preferred embodiment, the catalyst is a nanomaterial of the present invention, and the weight ratio of cycloalkane to catalyst may be 100: (5-100), preferably 100: (10-50).
According to the present invention, the oxidation reaction can be carried out in any conventional catalytic reactor, for example, in a batch tank reactor, a fixed bed reactor, a moving bed reactor, a suspended bed reactor, or a slurry bed reactor. The amount of the catalyst to be used may be appropriately selected depending on the amounts of the cycloalkane and the oxidizing agent, and the reactor.
In one embodiment, the oxidation reaction is carried out in a slurry bed reactor, and the amount of catalyst used may be 2 to 40g, preferably 5 to 25g, based on 100mL of cycloalkane, based on the nanomaterial of the present invention contained in the catalyst.
In another embodiment, the catalytic oxidation reaction is carried out in a fixed bed reactor and the weight hourly space velocity of the cycloalkane may be in the range of 0.01 to 100h-1Preferably 0.1 to 50h-1More preferably 0.2 to 25 hours-1。
According to the present invention, the conditions of the oxidation reaction include: the temperature is 50-200 ℃, the pressure is 0-20MPa, and the time is 1-72 hours. Preferably, the temperature is 60-180 ℃, the pressure is 0-10MPa, and the time is 2-24 hours. The oxidation reaction may be carried out under stirring conditions to allow the reaction to proceed more fully.
According to the present invention, the oxidizing agent is conventionally used by those skilled in the art, for example the oxidizing agent is an oxygen-containing gas, preferably air or oxygen, the oxygen concentration of which may be greater than 10% by volume. The molar ratio of the cycloalkane to the oxygen-containing gas of the medium oxygen can vary within wide limits, for example the molar amount of oxygen in the oxygen-containing gas can be from 1 to 20 times the theoretical oxygen demand for oxidation of the cycloalkane to the desired product. In one embodiment, the molar ratio of cycloalkane to oxygen-containing gas is from 1: (2-15), preferably 1: (4-12).
According to the invention, the cycloalkane may be a substituted or unsubstituted C5-C12 monocycloparaffin and/or a substituted or unsubstituted C8-C16 bicycloalkane. Further, when the cycloalkane is a monocyclic cycloalkane selected from substituted C5-C12 and/or substituted bicyclic cycloalkane selected from substituted C8-C16, the substituent may be halogen or methyl. In a preferred embodiment, the cycloalkane may be cyclohexane, cyclopentane, bicyclohexane, methylcyclohexane, halocyclohexane, methylcyclopentane, bromocyclohexane, chlorocyclopentane, and the like, preferably cyclohexane.
The invention is further illustrated by the following examples, but is not to be construed as being limited thereto.
The reagents adopted by the invention are all commercial analytical pure reagents.
Preparation examples 1 to 8 are for illustrating the nanomaterial of the present invention and the preparation method thereof, and preparation comparative examples 1 to 3 are for illustrating nanomaterials different from the present invention.
Preparation of example 1
(1) Mixing bismuth nitrate, ammonium vanadate and a nitric acid solution in a high-pressure reaction kettle for 10min, dropwise adding ammonia water into the high-pressure reaction kettle, reacting at 180 ℃ for 48h, centrifuging and cleaning the obtained mixture, and performing vacuum drying at 60 ℃ for 12h to obtain a first solid; wherein the mass ratio of the dosages of the bismuth nitrate, the ammonium vanadate, the nitric acid solution and the ammonia water is 1: 0.2: 0.5: 0.8, nitric acid solution is calculated by nitric acid, ammonia water is calculated by NH4 +And (6) counting.
(2) Adding 500mL of distilled water and concentrated nitric acid (the content of nitric acid in the concentrated nitric acid is 36 wt%) into a beaker as electrolyte, placing an anode graphite rod (the diameter is 8mm, and the length is 50cm) and a cathode graphite rod (the diameter is 8mm, and the length is 50cm) into the beaker, 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, connecting the cathode graphite rod with the negative pole of the direct current power supply, and applying 25V voltage to carry out electrolysis for 5 days to obtain a carbon dot solution; the concentration of nitric acid is 2 wt% based on the total weight of the electrolyte;
(3) uniformly mixing the carbon dot solution and nickel nitrate at room temperature (about 20 ℃), slowly dropwise adding ammonia water, continuously mixing for 10min in the stirring process to form a precipitate, mixing the obtained mixture with a first solid, and violently stirring to obtain a second mixture; wherein the weight ratio of the carbon dot solution, the nickel nitrate, the ammonia water and the first solid is 100: 20: 50: 25.
(4) and (3) freeze-drying the second mixture at-25 ℃ and a vacuum degree of 200Pa for 24h, putting the second mixture into a magnetic boat, performing first vacuum drying at 60 ℃ and a vacuum degree of 100Pa for 12h, washing the obtained solid by using absolute ethyl alcohol, and performing second vacuum drying at 350 ℃ and a vacuum degree of 500Pa for 6h to obtain the nano-material A1.
Preparation of example 2
Nanomaterial a2 was prepared in the same manner as in preparation example 1, except that in step (2), the concentration of nitric acid was 0.06 wt% based on the total weight of the electrolyte.
Preparation of example 3
Nanomaterial a3 was prepared in the same manner as in preparation example 1, except that in step (2), the concentration of nitric acid was 5.5 wt% based on the total weight of the electrolyte.
Preparation of example 4
The nanomaterial a4 was prepared by the same method as in preparation example 1, except that in step (1), the molar ratio of the amounts of bismuth nitrate, ammonium vanadate, nitric acid solution and aqueous ammonia was 1: 0.06: 2.5: 2.2 nitric acid solution in nitric acid, ammonia in NH4 +And (6) counting.
Preparation of example 5
A nanomaterial a5 was prepared in the same manner as in preparation example 1, except that, in step (3), the weight ratio of the amounts of the carbon dot solution, nickel nitrate, aqueous ammonia, and the first solid was 100: 107: 8: 25.
preparation of example 6
Nanomaterial a6 was prepared using the same method as in preparation example 1, except that, in step (4), the first vacuum drying and the second vacuum drying were performed under the same conditions: the temperature is 350 ℃, the vacuum degree is 500Pa, and the time is 6 h.
Preparation of example 7
Nanomaterial a7 was prepared by the same method as in preparation example 1, except that in step (4), vacuum drying was performed only once under the following conditions: the temperature is 350 ℃, the vacuum degree is 500Pa, and the time is 6 h.
Preparation of example 8
Nanomaterial A8 was prepared by the same method as in preparation example 1, except that in step (4), vacuum drying was performed only once under the following conditions: the temperature is 60 ℃, the vacuum degree is 100Pa, and the time is 12 h.
Preparation of comparative example 1
Preparing a nanomaterial DA1 according to the method of preparation example 1, except that the step (2) is omitted, in the step (3), deionized water and nickel nitrate are uniformly mixed at room temperature (about 20 ℃), then ammonia water is slowly dropped, the mixture is continuously mixed for 10min during stirring to form a precipitate, the obtained mixture is mixed with a first solid, and the mixture is vigorously stirred to obtain a second mixture; wherein the weight ratio of the deionized water to the nickel nitrate to the ammonia water to the first solid is 100: 20: 50: 25.
preparation of comparative example 2
A nanomaterial DA2 was prepared according to the method of preparation example 1, except that step (2) and step (3) were omitted, and the first solid obtained in step (1) was directly freeze-dried at-25 ℃ under a vacuum degree of 200Pa for 24 hours, and then put into a magnetic boat under a vacuum degree of 100Pa for 12 hours at 60 ℃, and the obtained solid was washed with absolute ethanol, and then subjected to second vacuum drying at 350 ℃ under a vacuum degree of 500Pa for 6 hours.
Preparation of comparative example 3
The nanomaterial DA3 was prepared according to the method of preparation example 1, except that the first vacuum drying and the second vacuum drying in step (4) were omitted, i.e., only freeze-drying was performed.
Examples 1-8 are presented to illustrate the process of catalytic oxidation of cycloalkanes using nanomaterials of the invention. Comparative examples 1 to 3 are for explaining the process for catalytically oxidizing cycloalkane using a catalytic material different from that of the present invention.
In the following examples and comparative examples, the oxidation products were analyzed by gas chromatography (GC: Agilent, 7890A) and gas chromatography-mass spectrometer (GC-MS: Thermo Fisher Trace ISQ). Conditions of gas chromatography: nitrogen carrier gas, temperature programmed: 60 ℃, 10 minutes, 15 ℃/minute, 180 ℃, 15 minutes; split ratio, 10: 1; the injection port temperature is 300 ℃; the detector temperature, 300 ℃, the results are listed in table 1.
On the basis, the conversion rate of raw materials and the selectivity of target products are calculated by respectively adopting the following formulas:
cyclohexane conversion (molar amount of cyclohexane added before reaction-molar amount of cyclohexane remaining after reaction)/molar amount of cyclohexane added before reaction x 100%,
adipic acid selectivity (molar amount of adipic acid formed after the reaction)/molar amount of cycloalkane added before the reaction × 100%.
Example 1
5g of the nanomaterial A1 as a catalyst and 100mL of cyclohexane were added to a 250mL autoclave, the autoclave was sealed, oxygen was introduced (the molar ratio of oxygen to cyclohexane was 10: 1), the mixture was stirred at 130 ℃ and 2.0MPa for 2 hours, the temperature was lowered, the pressure was released, a sample was taken, and the catalyst was separated by centrifugation and filtration, and the results of analysis of the oxidation products are shown in Table 1.
Examples 2 to 8
Examples 2 to 8 each performed catalytic oxidation of cyclohexane in the same manner as in example 1, except that in example 2, nanomaterial a2 was used as a catalyst, nanomaterial A3 was used as a catalyst in example 3, nanomaterial a4 was used as a catalyst in example 4, nanomaterial a5 was used as a catalyst in example 5, nanomaterial a6 was used as a catalyst in example 6, nanomaterial a7 was used as a catalyst in example 7, and nanomaterial A8 was used as a catalyst in example 8.
Comparative examples 1 to 3
Comparative examples 1 to 3 catalytic oxidation of cyclohexane was carried out in the same manner as in example 1, except that comparative example 1 used nanomaterial DA1 as a catalyst, comparative example 2 used nanomaterial DA2 as a catalyst, and comparative example 3 used nanomaterial DA3 as a catalyst, respectively.
TABLE 1
Catalyst numbering
Cyclohexane conversion rate%
Adipic acid selectivity,%
Example 1
A1
86
92
Example 2
A2
80
86
Example 3
A3
74
78
Example 4
A4
81
84
Example 5
A5
68
72
Example 6
A6
75
80
Example 7
A7
79
82
Example 8
A8
71
75
Comparative example 1
DA1
45
68
Comparative example 2
DA2
21
33
Comparative example 3
DA3
38
25
As can be seen from table 1, the method of the present invention can significantly improve the conversion of cyclohexane and has high selectivity of adipic acid.
As can be seen from comparison between example 1 and examples 4-5, preferably, when the amounts of bismuth nitrate, ammonium vanadate, acid solution and first alkali solution used in step (1) are in mass ratio, the prepared nanomaterial has better catalytic performance, and when the nanomaterial is used in catalytic oxidation reaction of cycloalkane such as cyclohexane, the conversion rate of raw materials and the selectivity of target product such as adipic acid are higher; as can be seen from comparison between example 1 and examples 2 to 3, preferably, when the concentration of the first inorganic acid in the electrolyte in step (2) is 0.1 to 5 wt% based on the total weight of the electrolyte, the prepared nanomaterial has better catalytic performance, and when the nanomaterial is used for catalytic oxidation of cycloalkane such as cyclohexane, the conversion rate of the raw material and the selectivity of the target product such as adipic acid are higher; as can be seen from comparison between example 1 and example 5, preferably, when the carbon dot solution, the nickel salt, the second alkali solution and the first solid are used in the step (3) in the weight ratio, the prepared nanomaterial has better catalytic performance, and when the nanomaterial is used for catalytic oxidation of cycloalkane such as cyclohexane, the conversion rate of raw materials and the selectivity of target products such as adipic acid are higher; as can be seen from comparison between example 1 and examples 6-8, preferably, when step (4) comprises sequentially subjecting the freeze-dried solid to first vacuum drying and second vacuum drying, the prepared nanomaterial has better catalytic performance, and when the nanomaterial is used for catalytic oxidation of cycloalkanes such as cyclohexane, the conversion rate of raw materials and the selectivity of target products such as adipic acid are higher.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.