CN109516490B - Preparation method of cerium dioxide nano particles with controllable structures - Google Patents
Preparation method of cerium dioxide nano particles with controllable structures Download PDFInfo
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- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 title claims abstract description 55
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 title claims abstract description 55
- 239000002105 nanoparticle Substances 0.000 title claims abstract description 44
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims abstract description 88
- 239000000243 solution Substances 0.000 claims abstract description 46
- 238000006243 chemical reaction Methods 0.000 claims abstract description 42
- 239000002244 precipitate Substances 0.000 claims abstract description 30
- 238000000034 method Methods 0.000 claims abstract description 27
- 238000000926 separation method Methods 0.000 claims abstract description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000001354 calcination Methods 0.000 claims abstract description 14
- 239000011259 mixed solution Substances 0.000 claims abstract description 11
- 230000008569 process Effects 0.000 claims abstract description 11
- QQZMWMKOWKGPQY-UHFFFAOYSA-N cerium(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O QQZMWMKOWKGPQY-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000001291 vacuum drying Methods 0.000 claims abstract description 7
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 38
- 238000010438 heat treatment Methods 0.000 claims description 32
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 15
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 15
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 15
- 238000003756 stirring Methods 0.000 claims description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 9
- 150000002466 imines Chemical class 0.000 claims description 7
- 238000006555 catalytic reaction Methods 0.000 claims description 3
- 238000002156 mixing Methods 0.000 abstract description 9
- 239000004094 surface-active agent Substances 0.000 abstract description 6
- 239000012043 crude product Substances 0.000 abstract description 4
- 239000000376 reactant Substances 0.000 abstract description 4
- 238000005406 washing Methods 0.000 abstract description 4
- 239000008367 deionised water Substances 0.000 abstract description 3
- 229910021641 deionized water Inorganic materials 0.000 abstract description 3
- 239000007864 aqueous solution Substances 0.000 abstract description 2
- 238000005265 energy consumption Methods 0.000 abstract 1
- 238000004519 manufacturing process Methods 0.000 abstract 1
- 239000002245 particle Substances 0.000 description 18
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 13
- 229910000420 cerium oxide Inorganic materials 0.000 description 11
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 description 8
- 239000003054 catalyst Substances 0.000 description 7
- 230000003197 catalytic effect Effects 0.000 description 7
- 238000001027 hydrothermal synthesis Methods 0.000 description 7
- 239000000047 product Substances 0.000 description 6
- 238000009210 therapy by ultrasound Methods 0.000 description 6
- 238000005054 agglomeration Methods 0.000 description 5
- 230000002776 aggregation Effects 0.000 description 5
- 239000002086 nanomaterial Substances 0.000 description 5
- 239000003513 alkali Substances 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 230000033558 biomineral tissue development Effects 0.000 description 3
- 238000003980 solgel method Methods 0.000 description 3
- 238000003786 synthesis reaction Methods 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000005119 centrifugation Methods 0.000 description 2
- 238000000975 co-precipitation Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 2
- 238000000593 microemulsion method Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000002073 nanorod Substances 0.000 description 2
- -1 polyethylene pyrrolidone Polymers 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000010532 solid phase synthesis reaction Methods 0.000 description 2
- 231100000419 toxicity Toxicity 0.000 description 2
- 230000001988 toxicity Effects 0.000 description 2
- 150000000703 Cerium Chemical class 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 125000000218 acetic acid group Chemical group C(C)(=O)* 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000012736 aqueous medium Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229940045348 brown mixture Drugs 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000003301 hydrolyzing effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000693 micelle Substances 0.000 description 1
- 239000011858 nanopowder Substances 0.000 description 1
- 231100000956 nontoxicity Toxicity 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000002957 persistent organic pollutant Substances 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
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- 230000035484 reaction time Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
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- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/20—Compounds containing only rare earth metals as the metal element
- C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
-
- 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
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
-
- B01J35/40—
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
Abstract
The invention relates to a preparation method of cerium dioxide nano particles with controllable structures, which comprises the following steps: (1) adding a surfactant into ethylene glycol, and uniformly mixing to obtain a solution A; putting cerium nitrate hexahydrate in an aqueous solution of ethylene glycol, and uniformly mixing to obtain a solution B; (2) pouring the solution B into the solution A, simultaneously adding a mineralizer, placing the obtained mixed solution into a microwave reactor for reaction, and obtaining a crude product after the obtained precipitate is subjected to centrifugal separation, washing and vacuum drying; (3) and calcining the crude product to obtain the cerium dioxide nano particles with controllable structures. Compared with the prior art, the cerium dioxide nano particle is formed under the condition of microwave ultrasonic step division, is simple, rapid, environment-friendly, low in process energy consumption and high in production safety, and the components of reactants are controlled according to different volume ratios of ethylene glycol and deionized water.
Description
Technical Field
The invention relates to the technical field of nano materials, in particular to a preparation method of structure-controllable cerium dioxide nano particles.
Background
The performance of the nano material is greatly improved compared with that of the bulk nano material, and the nano material with ultra-small particle size often has many new physical and chemical properties, so that the preparation of the nano material with ultra-small particle size has become one of the research hotspots in the nano field in recent years. The nano cerium dioxide has more oxygen vacancies and higher specific surface area, and is widely applied to the fields of automobile exhaust control, sewage treatment, electrode materials, anticorrosive coatings and the like. Because of the characteristics of no toxicity and high stability, the catalyst also receives more and more attention in the aspect of catalyzing and degrading organic pollutants. The shape and the particle size of the nanometer have important correlation with the property thereof, and in recent years, the research on the preparation and the application of the nanometer is very wide.
The main synthesis methods of cerium dioxide include hydrothermal method, coprecipitation method, sol-gel method, solid phase method, microemulsion method, etc., wherein the hydrothermal synthesis methods are reported more. For example, patent application No. 201710971094.0 discloses a hydrothermal method for preparing cerium dioxide with different morphologies by adding Ce (NO)3)3.6H2Dispersing O in NaOH solution, carrying out hydrothermal reaction at different temperatures, washing, drying, and calcining at different high temperatures to obtain cerium dioxide with different morphologies. Patent application No. 201610260014.6 discloses the synthesis of spherical cerium oxide: (1) mixing cerium salt, water, ethylene glycol, polyethylene pyrrolidone and short-chain organic acid, stirring for dissolving, transferring into a hydrothermal kettle for hydrothermal reaction (2), reacting at 160-240 ℃ for 1-8 hours, cooling, centrifuging to obtain precipitate, and drying the precipitate to obtain the spherical cerium dioxide. Patent application No. 201510970764.8 discloses a method for preparing a cerium dioxide nanorod, which comprises mixing cerium nitrate with tetraethyl hydroxide, hydrolyzing, storing the brown mixture at constant temperature, and calcining the obtained product to obtain a cerium dioxide nanorod with a regular and complete structure. However, the hydrothermal method, the coprecipitation method, the sol-gel method, the solid phase method and the microemulsion method require a long time for preparing the nano cerium dioxide (Applied Catalysis B: Environmental, 2018, 227, 209-217), and the yield is low.
Patent application No. 200710118268 discloses cerium oxide nanoparticles obtained by mixing a cerium ion solution with an alkali solution, then placing the mixture into a microwave high-pressure reaction tank, and carrying out microwave-assisted reaction. The invention uses organic amine as alkali source, and mixes with alkali liquor, and uses alkali source as mineralizer, so the catalytic effect of the synthesized catalyst is poor.
Disclosure of Invention
The present invention aims at overcoming the demerits of available technology, and provides process of preparing cerium dioxide nanometer particle with high yield, high safety and controllable structure.
The purpose of the invention can be realized by the following technical scheme: a method for preparing cerium dioxide nano particles with controllable structures comprises the following steps:
(1) adding a surfactant into ethylene glycol, and uniformly mixing to obtain a solution A; putting cerium nitrate hexahydrate in an aqueous solution of ethylene glycol, and uniformly mixing to obtain a solution B;
(2) pouring the solution B into the solution A, simultaneously adding a mineralizer, placing the obtained mixed solution into a microwave reactor for reaction, and obtaining a crude product after the obtained precipitate is subjected to centrifugal separation, washing and vacuum drying;
(3) and calcining the crude product to obtain the cerium dioxide nano particles with controllable structures.
The invention uses acetic acid as mineralizer, which is easy to synthesize pure substance, easy to volatilize, easy to crystallize and separate, low in price, low in toxicity, easy to recover, safe to operate, and good in catalytic effect of the synthesized catalyst. In addition, acetic acid can promote the generation of precipitate, and water is added into ethylene glycol to reduce the particle size and accelerate the mineralization of the ethylene glycol. Meanwhile, the invention adopts microwave ultrasonic method to synthesize in steps, which can greatly shorten the synthesis time.
Preferably, the surfactant is polyvinylpyrrolidone, and the K value of the polyvinylpyrrolidone is K10-K14. The reason why polyvinylpyrrolidone is selected as the surfactant is that the nano powder has small particle size and high surface energy and is easy to agglomerate, and after the polyvinylpyrrolidone is added, the polyvinylpyrrolidone is coated on the powder to prevent agglomeration and also control the shape of the powder. Has certain dispersing and stabilizing effects.
Preferably, in the solution a, the molar concentration of the polyvinylpyrrolidone is 0.008 to 0.024 mol/L.
Preferably, the molar concentration of the cerium nitrate in the solution B is 0.2-0.6 mol/L, and the volume ratio of the ethylene glycol to the water in the solution B is 4-24: 1. The aqueous medium has high relative dielectric constant (about 80) and self-recovery capability, is widely applied to a pulse power system, is beneficial to the absorption of microwaves, has the boiling point of ethylene glycol of 197.3 ℃, and can be applied to higher-temperature reaction by mixing the ethylene glycol and deionized water. Water is added into glycol to reduce particle size and accelerate mineralization.
Preferably, the mineralizer is acetic acid. The mineralizer can promote the synthesis of the precipitate, the acetic acid is the mineralizer, the pure substances are easy to synthesize, the acetic acid is easy to volatilize and crystallize and separate, the cost is low, the toxicity is low, the recovery is easy, the operation is safe, and the catalytic effect of the synthesized catalyst is good.
Preferably, the mass ratio of the surfactant to the cerium nitrate to the mineralizer in the mixed solution is 1-3: 2.17-6.51: 0.002 to 0.006.
Preferably, the microwave power of the microwave reactor is 250-1000W, the reaction time is 10-50 min, and the reaction temperature is 150-190 ℃. The invention adds water into glycol, which can reduce particle size and accelerate mineralization; the invention is mainly synthesized by a microwave and ultrasonic method, and is an open system, so that the invention is safer compared with the microwave high-pressure reaction tank (closed system) in the prior invention; the ultrasonic device of the instrument can generate cavitation during reaction, namely, a micro-bubble nucleus in liquid generates vibration under the action of ultrasonic waves, when sound pressure reaches a certain value, bubbles rapidly expand and then suddenly close, shock waves are generated when the bubbles close, a series of dynamic processes such as expansion, closing, oscillation and the like greatly improve heterogeneous reaction rate, realize uniform mixing among heterogeneous reactants, accelerate the diffusion of the reactants and products, promote the formation of a solid new phase, and can control the size and distribution of particles; the microwave and ultrasonic auxiliary mode can avoid the agglomeration of nano particles during high-temperature reaction, and the obtained cerium dioxide nano particles have good dispersibility; the microwave instrument can be programmed in different steps, and the advantage is that the temperature can be raised in different stages, so that more experiment requirements can be met; according to the method, different components of reactants are different according to different volume ratios of ethylene glycol and deionized water, so that the lowest surface micelle concentration of the surfactant is different, and different nano cerium dioxide products are obtained.
More preferably, an ultrasonic auxiliary mode is adopted, the frequency of the ultrasonic is 20-30 KHz, and the time of the ultrasonic is 10-50 min. The auxiliary mode can prevent agglomeration among the nano-particles during reaction, and the obtained cerium dioxide nano-particles have good dispersibility. . The auxiliary mode can prevent agglomeration among the nano-particles during reaction, and the obtained cerium dioxide nano-particles have good dispersibility.
Preferably, the rotating speed of centrifugal separation is 8000-11000 rpm, the time of centrifugal separation is 5-15 min, absolute ethyl alcohol is adopted for washing, the vacuum degree of vacuum drying is 0-133 Pa, the temperature of vacuum drying is 50-90 ℃, and the time of vacuum drying is 6-24 h.
Preferably, the calcining temperature is 300-800 ℃, and the calcining time is 0.5-6 h.
Compared with the prior art, the beneficial effects of the invention are embodied in the following aspects:
(1) the time required for preparing the nano cerium dioxide with the controllable structure is shorter than that of the traditional hydrothermal method and sol-gel method, and only ten minutes to dozens of minutes are needed.
(2) The nano cerium dioxide with controllable structure prepared by the invention takes cerium nitrate as a raw material, and reacts under the assistance of microwaves to obtain nano cerium dioxide particles with ultra-small particle size. Wherein, the microwave and ultrasonic auxiliary mode can avoid the agglomeration among the nano particles during high temperature reaction, and the obtained cerium dioxide nano particles have good dispersibility.
(3) The nano cerium dioxide with controllable structure prepared by the invention has good application prospect in the aspects of catalysts, polishing materials, automobile exhaust purification catalysts and the like.
(4) The invention has simple preparation process, does not introduce and generate toxic and harmful substances, and meets the requirement of green chemistry.
Drawings
Fig. 1 is an SEM image of cerium oxide nanoparticles prepared in example 1;
FIG. 2 is an SEM photograph of cerium oxide nanoparticles prepared in example 2;
FIG. 3 is an SEM photograph of cerium oxide nanoparticles prepared in example 4;
FIG. 4 is an X-ray diffraction pattern of cerium oxide nanoparticles prepared in examples 1 to 5;
FIG. 5 is a graph showing the catalytic performance of the cerium oxide nanoparticles prepared in examples 1 to 5.
Detailed Description
The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.
Example 1
In this embodiment, the preparation of the ceria nanoparticles is performed by the following method, which specifically includes the following steps:
(1) adding 1g of polyvinylpyrrolidone into 14mL of ethylene glycol, and uniformly stirring to obtain a solution A;
(2) 2.1711g of cerous nitrate hexahydrate is added into 20mL of ethylene glycol and 1mL of water, and the mixture is uniformly stirred to obtain a solution B;
(3) slowly adding the solution B into the solution A, and slowly adding 2mL of acetic acid to obtain a mixed solution;
(4) the reaction is carried out by a microwave reactor, and the microwave reaction operation is a step-by-step reaction:
(a) heating to 100 deg.C for 10min, and maintaining the temperature for 10 min;
(b) heating to 150 deg.C for 10min, and keeping the temperature for 10 min.
Dispersing the obtained cerium dioxide nanoparticles in absolute ethyl alcohol, performing ultrasonic treatment for 15min, performing centrifugal separation at 9500rpm for 5min, and repeating the above centrifugal separation method to obtain precipitate. This process was repeated 4 times and dried under vacuum at 60 c for 12 hours to obtain a precipitate.
(5) And placing the dried precipitate in a muffle furnace, setting the heating rate to be 2 ℃/min, and calcining for 1h under the condition of heating to 500 ℃ in air to obtain the nano-scale cerium dioxide.
The cerium oxide nanoparticles prepared in example 1 were characterized by using a scanning electron microscope, and as a result, as shown in fig. 1, it can be seen that the particles have a small and uniform particle size of about 0.38 μm.
Example 2
In this embodiment, the preparation of the ceria nanoparticles is performed by the following method, which specifically includes the following steps:
(1) adding 1g of polyvinylpyrrolidone into 13mL of ethylene glycol, and uniformly stirring to obtain a solution A;
(2) 2.1711g of cerous nitrate hexahydrate is added into 20mL of ethylene glycol and 2mL of water, and the mixture is uniformly stirred to obtain a solution B;
(3) slowly adding the solution B into the solution A, and slowly adding 2mL of acetic acid to obtain a mixed solution;
(4) the reaction is carried out by a microwave reactor, and the microwave reaction operation is a step-by-step reaction:
(a) heating to 100 deg.C for 10min, and maintaining the temperature for 10 min;
(b) heating to 160 deg.C for 10min, and maintaining the temperature for 20 min.
Dispersing the obtained cerium dioxide nanoparticles in absolute ethyl alcohol, performing ultrasonic treatment for 15min, performing centrifugal separation at 9500rpm for 5min, and repeating the above centrifugal separation method to obtain precipitate. This process was repeated 4 times and dried under vacuum at 60 c for 12 hours to obtain a precipitate.
(5) And placing the dried precipitate in a muffle furnace, setting the heating rate to be 2 ℃/min, and calcining for 1h under the condition of heating to 500 ℃ in air to obtain the nano-scale cerium dioxide.
The cerium oxide nanoparticles prepared in example 2 were characterized by using a scanning electron microscope, and as a result, as shown in fig. 2, it can be seen that the particles have a small and uniform particle size of about 0.28 μm.
Example 3
In this embodiment, the preparation of the ceria nanoparticles is performed by the following method, which specifically includes the following steps:
(1) adding 1g of polyvinylpyrrolidone into 12mL of ethylene glycol, and uniformly stirring to obtain a solution A;
(2) 2.1711g of cerous nitrate hexahydrate is added into 20mL of ethylene glycol and 3mL of water, and the mixture is uniformly stirred to obtain a solution B;
(3) slowly adding the solution B into the solution A, and slowly adding 2mL of acetic acid to obtain a mixed solution;
(4) the reaction is carried out by a microwave reactor, and the microwave reaction operation is a step-by-step reaction:
(a) heating to 100 deg.C for 10min, and maintaining the temperature for 10 min;
(b) heating to 170 deg.C for 10min, and maintaining the temperature for 30 min.
Dispersing the obtained cerium dioxide nanoparticles in absolute ethyl alcohol, performing ultrasonic treatment for 15min, performing centrifugal separation at 9500rpm for 5min, and repeating the above centrifugal separation method to obtain precipitate. This process was repeated 4 times and dried under vacuum at 60 c for 12 hours to obtain a precipitate.
(5) And placing the dried precipitate in a muffle furnace, setting the heating rate to be 2 ℃/min, and calcining for 1h under the condition of heating to 500 ℃ in air to obtain the nano-scale cerium dioxide.
Example 4
In this embodiment, the preparation of the ceria nanoparticles is performed by the following method, which specifically includes the following steps:
(1) adding 1g of polyvinylpyrrolidone into 11mL of ethylene glycol, and uniformly stirring to obtain a solution A;
(2) 2.1711g of cerous nitrate hexahydrate is added into 20mL of ethylene glycol and 4mL of water and stirred uniformly to obtain a solution B;
(3) slowly adding the solution B into the solution A, and slowly adding 2mL of acetic acid to obtain a mixed solution;
(4) the reaction is carried out by a microwave reactor, and the microwave reaction operation is a step-by-step reaction:
(a) heating to 100 deg.C for 10min, and maintaining the temperature for 10 min;
(b) heating to 180 deg.C for 10min, and keeping the temperature for 40 min.
Dispersing the obtained cerium dioxide nanoparticles in absolute ethyl alcohol, performing ultrasonic treatment for 15min, performing centrifugal separation at 9500rpm for 5min, and repeating the above centrifugal separation method to obtain precipitate. This process was repeated 4 times and dried under vacuum at 60 c for 12 hours to obtain a precipitate.
(5) And placing the dried precipitate in a muffle furnace, setting the heating rate to be 2 ℃/min, and calcining for 1h under the condition of heating to 500 ℃ in air to obtain the nano-scale cerium dioxide.
The cerium oxide nanoparticles prepared in example 4 were characterized by using a scanning electron microscope, and as a result, as shown in fig. 3, it can be seen that the particles have a small and uniform particle size of about 0.34 μm.
Example 5
In this embodiment, the preparation of the ceria nanoparticles is performed by the following method, which specifically includes the following steps:
(1) adding 1g of polyvinylpyrrolidone into 10mL of ethylene glycol, and uniformly stirring to obtain a solution A;
(2) 2.1711g of cerous nitrate hexahydrate is added into 20mL of ethylene glycol and 5mL of water and stirred uniformly to obtain a solution B;
(3) slowly adding the solution B into the solution A, and slowly adding 2mL of acetic acid to obtain a mixed solution;
(4) the reaction is carried out by a microwave reactor, and the microwave reaction operation is a step-by-step reaction:
(a) heating to 100 deg.C for 10min, and maintaining the temperature for 10 min;
(b) heating to 190 deg.C for 10min, and maintaining the temperature for 50 min.
Dispersing the obtained cerium dioxide nanoparticles in absolute ethyl alcohol, performing ultrasonic treatment for 15min, performing centrifugal separation at 9500rpm for 5min, and repeating the above centrifugal separation method to obtain precipitate. This process was repeated 4 times and dried under vacuum at 60 c for 12 hours to obtain a precipitate.
(5) And placing the dried precipitate in a muffle furnace, setting the heating rate to be 2 ℃/min, and calcining for 1h under the condition of heating to 500 ℃ in air to obtain the nano-scale cerium dioxide.
In order to verify that the nanoparticles prepared in examples 1 to 5 were cerium oxide, the product was subjected to X-ray diffraction analysis, and the result is shown in fig. 4, where each characteristic peak corresponds to a characteristic peak of a standard card (JCPDS No. 34-0394). And no hetero-peak exists, which indicates that the cerium dioxide with higher purity can be rapidly synthesized by microwave. In addition, the XRD diffraction peak of the sample is broad, further illustrating that the particle size of the synthesized product is small.
To test the catalytic performance of the ceric oxides prepared in examples 1 to 5, the products were subjected toThe result of the analysis of the imine catalysis experiment is shown in FIG. 5, and the conversion of the imine is example 2(3.99 mmol. multidot.g)-1h-1)>Example 3(2.96 mmol. multidot.g)-1h-1)>Example 4(2.48 mmol. multidot.g)-1h-1)>Example 5(1.71 mmol. multidot.g)-1h-1)>Example 1(1.26 mmol. multidot.g)-1h-1). The catalyst imine conversion rate of all the examples is far higher than 0.46 mmol-g reported in the literature-1h-1(Angew.Chem.-Int.Edit.2015，54，864-867)。
Example 6
A similar preparation method to that of example 1 was employed, except that:
(1) adding 0.00008mol of polyvinylpyrrolidone into 10mL of ethylene glycol, and uniformly stirring to obtain a solution A;
(2) adding 0.004mol of cerous nitrate hexahydrate into 16mL of ethylene glycol and 4mL of water, and uniformly stirring to obtain a solution B;
(3) slowly adding the solution B into the solution A, and slowly adding 2mL of acetic acid to obtain a mixed solution;
(4) the reaction is carried out by a microwave reactor, and the microwave reaction operation is a step-by-step reaction:
(a) heating to 100 deg.C for 10min, and maintaining the temperature for 25 min;
(b) heating to 190 deg.C for 10min, and maintaining the temperature for 25 min.
Dispersing the obtained cerium dioxide nanoparticles in absolute ethyl alcohol, performing ultrasonic treatment for 10min, performing centrifugal separation at 9500rpm for 5min, and repeating the above centrifugal separation method to obtain precipitate. This process was repeated 4 times and dried under vacuum at 60 c for 12 hours to obtain a precipitate.
(5) And placing the dried precipitate in a muffle furnace, setting the heating rate to be 2 ℃/min, and calcining for 1h under the air condition of heating to 300 ℃ to obtain the nano-scale cerium dioxide.
Through detection, the nano-scale cerium dioxide prepared by the embodiment has good dispersibility and good imine catalytic performance.
Example 7
A similar preparation method to that of example 1 was employed, except that:
(1) adding 0.00024mol of polyvinylpyrrolidone into 10mL of ethylene glycol, and uniformly stirring to obtain a solution A;
(2) adding 0.024mol of cerous nitrate hexahydrate into 24mL of ethylene glycol and 1mL of water, and uniformly stirring to obtain a solution B;
(3) slowly adding the solution B into the solution A, and slowly adding 6mL of acetic acid to obtain a mixed solution;
(4) the reaction is carried out by a microwave reactor, and the microwave reaction operation is a step-by-step reaction:
(a) heating to 100 deg.C for 10min, and maintaining the temperature for 15 min;
(b) heating to 190 deg.C for 10min, and maintaining the temperature for 15 min.
Dispersing the obtained cerium dioxide nanoparticles in absolute ethyl alcohol, performing ultrasonic centrifugation for 50min at 9500rpm for 5min, and repeating the above centrifugation method to obtain precipitate. This process was repeated 4 times and dried under vacuum at 60 c for 12 hours to obtain a precipitate.
(5) And placing the dried precipitate in a muffle furnace, setting the heating rate to be 2 ℃/min, and calcining for 1h under the condition of heating to 800 ℃ and air to obtain the nano-scale cerium dioxide.
Through detection, the nano-scale cerium dioxide prepared by the embodiment has good dispersibility and good imine catalytic performance.
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (4)
1. A preparation method of cerium dioxide nano particles with controllable structures is characterized by comprising the following steps:
(1) adding 1g of polyvinylpyrrolidone into 13mL of ethylene glycol, and uniformly stirring to obtain a solution A;
(2) adding 2.1711g of cerous nitrate hexahydrate into 20mL of ethylene glycol and 2mL of water, and uniformly stirring to obtain a solution B;
(3) slowly adding the solution B into the solution A, and slowly adding 2mL of acetic acid to obtain a mixed solution;
(4) the reaction is carried out by a microwave reactor, and the microwave reaction operation is a step-by-step reaction:
(a) heating to 100 deg.C for 10min, and maintaining the temperature for 10 min;
(b) heating to 160 deg.C for 10min, and maintaining the temperature for 20 min;
dispersing the obtained cerium dioxide nanoparticles in absolute ethyl alcohol, performing ultrasonic separation for 15min, performing centrifugal separation at 9500rpm for 5min, and repeating the centrifugal separation method to obtain precipitate; the process is repeated for 4 times, and then vacuum drying is carried out for 12 hours at the temperature of 60 ℃ to obtain a precipitate;
(5) placing the dried precipitate in a muffle furnace, setting a heating rate of 2 ℃/min, and calcining for 1h under the condition of heating to 500 ℃ in air to obtain nano-scale cerium dioxide;
the reaction in the microwave reaction instrument adopts an ultrasonic auxiliary mode, and the frequency of the ultrasonic is 20-30 KHz;
the cerium dioxide nano particles are in a fusiform structure and used for imine catalysis, and the conversion rate of imine is 3.99mmol ∙ g- 1h-1。
2. The method for preparing cerium dioxide nanoparticles with controllable structures according to claim 1, wherein the polyvinylpyrrolidone has a K value of K10-K14.
3. The method for preparing cerium dioxide nanoparticles with controllable structures according to claim 1, wherein the microwave power of the microwave reactor is 250-1000W.
4. The method for preparing cerium dioxide nanoparticles with controllable structures according to claim 1, wherein the vacuum degree of vacuum drying is 0-133 Pa.
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