CN114671452A - Method for preparing massive cerium oxide aerogel by taking epoxy compound as gel accelerator - Google Patents

Method for preparing massive cerium oxide aerogel by taking epoxy compound as gel accelerator Download PDF

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CN114671452A
CN114671452A CN202210201933.1A CN202210201933A CN114671452A CN 114671452 A CN114671452 A CN 114671452A CN 202210201933 A CN202210201933 A CN 202210201933A CN 114671452 A CN114671452 A CN 114671452A
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epoxy compound
gel
solution
cerium oxide
oxide aerogel
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CN114671452B (en
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王晓青
洪樟连
支明佳
夏尚
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Chuzhou University
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    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01FCOMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F17/00Compounds of rare earth metals
    • C01F17/20Compounds containing only rare earth metals as the metal element
    • C01F17/206Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
    • C01F17/224Oxides or hydroxides of lanthanides
    • C01F17/235Cerium oxides or hydroxides
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    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J13/00Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
    • B01J13/0091Preparation of aerogels, e.g. xerogels
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/10Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
    • B01J35/23
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01FCOMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F17/00Compounds of rare earth metals
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    • C01PINDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00Physical properties of inorganic compounds
    • C01P2006/10Solid density
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    • C01INORGANIC CHEMISTRY
    • C01PINDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00Physical properties of inorganic compounds
    • C01P2006/12Surface area
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01PINDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00Physical properties of inorganic compounds
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00Technologies relating to chemical industry
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    • Y02P20/54Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids

Abstract

The invention discloses a method for preparing massive cerium oxide aerogel by using an epoxy compound as a gel accelerator through a sol-gel method, which comprises the following steps: 1) dissolving inorganic cerium salt as metal source in anhydrous alcohol; epoxy compound is used as a gel accelerator, formamide, polyvinyl alcohol PEG-X with different molecular weights and polyacrylic acid with different molecular weights are used as additives; 2) rapidly adding the epoxy compound solution into an inorganic metal cerium salt/absolute ethyl alcohol solution containing an additive, rapidly stirring, sealing and then putting into an oven to obtain wet gel; 3) aging the wet gel; 4) and (3) taking absolute ethyl alcohol and carbon dioxide as supercritical fluid media, and performing supercritical drying treatment on the aged wet gel to finally obtain the bulk cerium oxide aerogel. By adjusting the proportion of the metal cerium salt and the epoxy compound, the blocky cerium oxide aerogel with low density, high specific surface area and high porosity can be successfully prepared.

Description

Method for preparing massive cerium oxide aerogel by taking epoxy compound as gel accelerator
Technical Field
The invention relates to the technical field of aerogel preparation, in particular to a method for preparing bulk cerium oxide aerogel by taking an epoxy compound as a gel accelerator.
Background
Research shows that the ceria-catalyzed CO oxidation reaction follows the Mars-van Krevelen mechanism, i.e., lattice oxygen on the ceria surface oxidizes CO to form holes after the CO is consumed, and oxygen in the atmosphere or bulk lattice oxygen continues to oxidize CO after the oxygen vacancies are activated.
In recent years, the realization of CO oxidation at relatively low temperatures has been attracting attention. And CeO2The base material is very suitable for CO oxidation reaction. Cerium oxide (CeO)2) Is a yellow-white rare earth oxide, and the crystal structure of the rare earth oxide is fluorite. Cerium ions are easy to realize conversion between trivalent and quadrivalent under different redox conditions, so that high oxygen storage capacity is endowed to cerium dioxide. Ce in cerium oxide crystals3+The more oxygen defects are formed, the more oxygen vacancies are formed, and the ceria may lose part of the lattice oxygen under the condition of containing less oxygen, thereby forming a lot of oxygen vacancies. When the oxygen content is high, ceria can store a large amount of oxygen, and thus ceria has a strong redox ability. In which CeO is present2The specific surface area, the structural defects and the oxygen vacancies of the carbon dioxide have important influence on the CO oxidation. For example, Zhang et al compared two different CeO2The CO oxidation performance of the one-dimensional nano material to obtain CeO 2The single-wall/multi-wall hollow microspheres can ensure that the conversion rate of CO reaches 100 percent at 230 ℃, and the bulk CeO2The same conversion needs to be achieved at 500 ℃ because the hollow microsphere structure provides more available oxygen and oxygen defects for CO oxidation [ Zhang Y, Cheng T, Hu Q, Fang Z, Han K, Study of the Preparation and Properties of CeO2Single/Multiwall Hollow Microspheres,Journal of Materials Research,2011,22,1472-1478]. Further, CeO2One of the best soot combustion catalysts is considered, which can significantly lower the reaction temperature.
CeO2Has better storageOxygen capacity and good ionic conductivity. CeO (CeO)2The most important characteristic is its oxygen storage capacity. It is clear that this property is associated with CeO2The oxygen migration capability of crystal lattice on the surface of the material is related, the oxygen vacancy concentration from the surface to the body is gradually reduced, the gradient causes the crystal lattice oxygen to diffuse from the outside to the surface, and the oxygen ions lead Ce4+Reduction to Ce3+Resulting in the generation of surface oxygen vacancies, making this material suitable for most electrochemical and photochemical applications. In addition, it is well known that the catalytic activity of the nanoparticles depends to a great extent on the size and morphology of the material, and therefore, CeO is regulated2The size and morphology of nanoporous materials have become a focus of research.
By utilizing advanced synthesis technology, researchers can reasonably design and synthesize the high-efficiency cerium dioxide catalyst with specific morphology, size, structure, components and crystal face. To study CeO 2The relationship between the morphology and the catalytic performance, researchers synthesize various CeO with different morphologies and novel structures2Nanomaterials, including rods [ Li, j; zhang, z; tian, Z.; zhou, x.; zheng, z.; ma, y; qu, Y., Low compressed porous nanoparticles of center with high reduction and large oxygen storage capacity. journal of Materials Chemistry A2014, 2(39),16459-]Spherical [ Yang, f.; wei, J.; liu, w.; guo, j.; yang, Y., compressor-mounted bacteria, surface devices, proteinaceous catalytic activity and a top layer application. journal of Materials Chemistry A2014, 2(16),5662-]A cube [ Wu, q.; zhang, f.; xiao, p.; tao, h.; wang, x.; hu, z.; lu, Y., Great influx of atoms for controlling synthesis of CeO2nanostructures:from nanorods to nanocubes.The Journal of Physical Chemistry C 2008,112(44),17076-17080]Tablet [ Huang, y.c.; long, b.; tang, m.n.; rui, z.b.; balogun, m. -s.; tong, y.x.; ji, H.B., Bifunctional catalytic material an ultrastable and high-performance surface defect CeO2nanosheets for formaldehyde thermal oxidation and photocatalytic oxidation.Applied Catalysis B:Environmental 2016,181,779-787]Tubular [ Wan, C.;Cheng,D.G.;Chen,F.Q.;Zhan,X.L.,Fabrication of CeO2 nanotube supported Pt catalyst encapsulated with silica for high and stable performance.Chemical Communications 2015,51(48),9785-9788]And fibrous [ Lu, p.; qiao, b.; lu, n.; hyun, d.c.; wang, j.; kim, m.j.; liu, j.; xia, Y, Photochemical position of high purity dispersed Pt nanoparticles on CeO 2 nanofibers for the water-gas shift reaction.Advanced Functional Materials 2015,25(26),4153-4162]。CeO2The difference in morphology and size often causes differences in atomic arrangement, energy level structure, interface properties and the like on the surface of the crystal, thereby affecting the physicochemical properties of the material. For example, Guo et al [ Hu, z.; liu, x.; meng, d.; guo, y.; guo, y.; lu, G., Effect of center crystal plate on the physical and catalytic properties of Pd/center for CO and propane oxidation ACS Catalysis 2016,6(4),2265-]CeO carrying Pd was investigated2The performance of the different crystal faces of the catalyst for the catalytic oxidation of CO and propane. The research shows that the rod-shaped cerium oxide CeO is surrounded by the (110) and (100) crystal faces2-RHas the highest CO catalytic oxidation activity, and in contrast, octahedral cerium oxide CeO with exposed (111) crystal face2Has the highest activity for the catalytic oxidation of propane. In order to further increase CeO2Two strategies are generally adopted for the catalytic performance of (a): firstly, optimizing the structure and the appearance of cerium oxide; secondly, other metal ions, such as noble metals or transition metal oxides, are doped into the cerium oxide lattices. Various CeO with specific shape and size2And based on CeO2The multi-component metal oxide has been reported and widely applied to CO oxidation, CO selective oxidation, three-way catalysts, low-temperature water-vapor conversion reaction, biomedicine, water treatment, solid fuel cells, photocatalysis, organic catalytic reaction and the like.
The sol-gel method has wide application in wet chemical synthesis. In a typical sol-gel synthesis method, precursor metal salt is hydrolyzed, dehydrated and condensed to gradually form sol, gel is formed along with the further condensation reaction, and then drying and roasting treatment are carried out to obtain the required nano material. General solutionThe gel-gel reaction is to obtain cerium dioxide nanocrystals with porous structures. However, conventional sol-gel processes generally yield CeO in powder form2And the specific surface area is generally small.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: a process for preparing the block-shaped ceric oxide aerogel by using inorganic or organic metal cerium salt as precursor and epoxy compound as gel promoter features low cost and simple reaction.
In order to solve the technical problems, the invention provides the following technical scheme:
a method for preparing bulk cerium oxide aerogel by taking an epoxy compound as a gel accelerator comprises the following specific preparation steps:
1) dissolving inorganic or organic metal cerium salt in absolute ethyl alcohol to prepare a metal cerium salt precursor solution, wherein the concentration of the metal salt is 0.01-10.0 mol/L;
2) Respectively adding different additives with different contents and different types into the metal cerium salt precursor solution; the additive is one or more of formamide, polyvinyl alcohol with different molecular weights and polyacrylic acid with different molecular weights;
3) adding the epoxy compound solution into the solution obtained in the step 2), quickly stirring, sealing, and then placing in an environment of 25-70 ℃ for treatment for a certain time to obtain wet gel; the volume ratio of the epoxy compound solution to the solution obtained in the step 2) is 1/100-1/1;
4) immersing the obtained wet gel in an aging solution at the temperature of 25-70 ℃, and performing aging treatment for 2-7 d; the aging liquid is one or more of isopropanol, absolute ethyl alcohol or absolute methyl alcohol;
5) putting the wet gel after the aging treatment into a high-pressure reaction kettle of a supercritical drying device, and performing supercritical drying by adopting ethanol or carbon dioxide as a supercritical medium, wherein the temperature of the ethanol supercritical drying is 260-300 ℃, the heat preservation time is 10-120min, and the pressure is 7-12 MPa; the temperature of carbon dioxide supercritical drying is 45-75 deg.C, the heat preservation time is 90-150min, and the pressure is 10-15 MPa; and after drying, discharging the gas in the high-pressure reaction kettle to obtain the massive metal oxide aerogel.
Preferably, the inorganic or organometallic cerium salt employed is Ce2(SO4)3,Ce2(SO4)3·8H2O,Ce(COOCH3)3,Ce(Ac)3·nH2O,Ce(NO3)3,Ce(NO3)3·6H2O,CeCl3,CeCl3·7H2O,Ce2(CO3)3,Ce2(CO3)3·xH2O,Ce2(C2O4)3,Ce2(C2O4)3·xH2Any one or more of O.
Preferably, the epoxy compound includes one or more of ethylene oxide, propylene oxide, epichlorohydrin and butylene oxide, and the concentration of the epoxy compound is 0-30 mol/L.
Preferably, the aging liquid used is isopropanol, absolute ethyl alcohol and absolute methyl alcohol or their mixture in different proportions.
Preferably, the final concentration of the additive in the step 2) is 0-30 mol/L.
The invention has the following beneficial effects:
the preparation method disclosed by the invention aims to further search a preparation process of the cerium dioxide bulk aerogel material with low cost and stable structure and the cerium dioxide aerogel material, and introduces formamide, polyethylene glycol with different molecular weights and polyacrylic acid with different molecular weights into the preparation process of the cerium oxide aerogel from the aspects of regulating and controlling the sol-gel process and the gel structure of the inorganic cerium salt raw material and the characteristics of the cerium dioxide aerogel material product, so that the formation of powder in the processes of gelation and drying is avoided, and the bulk cerium oxide aerogel is obtained. The prepared cerium oxide aerogel material has the characteristics of large specific surface area and high porosity, and can be used as a catalyst carrier in CO oxidation reaction.
The invention takes metal salt containing cerium as a precursor and takes an epoxy compound as a gel accelerator for preparationHas a low density (0.05-0.3 g/cm)3) High porosity (95-99%), large specific surface area (100-1000 m)2/g), and the like, and has wide application prospect.
Drawings
FIG. 1 is a scanning electron micrograph of the cerium oxide aerogel material prepared in example 1.
Detailed Description
The following examples are included to provide further detailed description of the present invention and to provide those skilled in the art with a more complete, concise, and exact understanding of the principles and spirit of the invention.
Example 1
(1) Preparing a cerium salt precursor solution: 0.261g of Ce (NO)3)3·6H2O is added to 60mL of absolute ethanol, wherein [ Ce ]3+]Sealing the solution with preservative film at 0.01mol/L, and stirring the solution on a magnetic stirrer until the solution is completely dissolved.
(2) Formamide was added in an additional 5mL and stirred until the solution was clear.
(3) And (3) adding 10mL of propylene oxide into the precursor solution containing the cerium salt in the step (2), and stirring for 1min until the mixture is uniform to form sol.
(4) Pouring the sol into a culture dish, sealing with a preservative film, and putting into an oven at 60 ℃ to form wet gel.
(5) And (3) putting the wet gel into a glass vessel filled with absolute ethyl alcohol, sealing, and then putting into an oven at 40 ℃ for aging for 5 d.
(6) And (3) putting the wet gel obtained after aging into a high-pressure reaction kettle of a supercritical drying device, performing supercritical drying by adopting supercritical ethanol, wherein the supercritical drying temperature is 260 ℃, the heat preservation time is 60min, and the pressure is 7MPa, and discharging the gas in the high-pressure reaction kettle after the drying is finished to obtain the bulk cerium oxide aerogel.
(7) The obtained bulk ceria aerogel has a density of 0.325g/cm3The specific surface area is 320m2(ii) a porosity of 93.5%.
Example 2
(1) Preparing a cerium salt precursor solution: 11.17g of CeCl3·7H2O is added to 60mL of absolute ethanol, wherein [ Ce ]3+]Sealing the solution with preservative film at 0.5mol/L, and stirring the solution on a magnetic stirrer until the solution is completely dissolved.
(2) A further 6mL polyacrylic acid PAA (M) was addedV4000000) and stirred until the solution became clear.
(3) And (3) adding 5mL of epoxy chloropropane into the precursor solution containing the cerium salt in the step (2), and stirring for 1min until the solution is uniform to form sol.
(4) Pouring the sol into a culture dish, sealing with a preservative film, and forming wet gel at room temperature of 25 ℃.
(5) The wet gel was placed in a glass dish of absolute ethanol and aged in an oven at 40 ℃ for 5 days.
(6) And (3) putting the wet gel obtained after aging into a high-pressure reaction kettle of a supercritical drying device, performing supercritical drying in an absolute ethyl alcohol atmosphere, wherein the supercritical drying temperature is 260 ℃, the heat preservation time is 80min, the pressure is 8MPa, and after drying is finished, discharging gas in the high-pressure reaction kettle to obtain the cerium oxide aerogel.
(7) The bulk ceria aerogel obtained had a density of 0.163g/cm3A specific surface area of 260m2The porosity was 96.4%.
Example 3
(1) Preparing a cerium salt precursor solution: 22.86g of Ce2(C2O4)3·xH2O is added to 60mL of absolute ethanol, wherein [ Ce ]3+]Sealing the solution with preservative film at 0.7mol/L, and stirring the solution on a magnetic stirrer until the solution is completely dissolved.
(2) Add 5mL of additional polyethylene glycol (M)n10000) was stirred until the solution was clear.
(3) 8mL of 1, 2-epoxybutane was added to the precursor solution containing cerium salt in (2), and stirred for 1min until homogeneous, to form a sol.
(4) Pouring the sol into a culture dish, sealing with a preservative film, and putting into an oven at 60 ℃ to form wet gel.
(5) The wet gel was placed in a glass dish containing absolute ethanol/tetraethyl orthosilicate (V/V ═ 7:3) and aged in an oven at 25 ℃ for 7 d.
(6) And (3) putting the wet gel obtained after aging into a high-pressure reaction kettle of a supercritical drying device, performing supercritical drying by adopting supercritical ethanol, wherein the supercritical drying temperature is 270 ℃, the heat preservation time is 90min, and the pressure is 9MPa, and discharging the gas in the high-pressure reaction kettle after the drying is finished to obtain the cerium oxide aerogel.
(7) The bulk ceria aerogel obtained had a density of 0.213g/cm3A specific surface area of 360m2(ii) a porosity of 97.1%.
Example 4
(1) Preparing a cerium salt precursor solution: 5.22g of Ce (NO)3)3·6H2O is added to 60mL of absolute ethanol, wherein [ Ce ]3+]Sealing the solution with preservative film at 0.2mol/L, and stirring the solution on a magnetic stirrer until the solution is completely dissolved.
(2) Add 3mL of polyethylene glycol (M) furthern4000) stirring until the solution is clear.
(3) And (3) adding 15mL of propylene oxide into the precursor solution containing the cerium salt in the step (2), and stirring for 1min until the mixture is uniform to form sol.
(4) Pouring the sol into a culture dish, sealing with a preservative film, and putting into an oven at 60 ℃ to form wet gel.
(5) And (3) putting the wet gel into a glass dish containing absolute ethyl alcohol, and putting the glass dish into an oven at 70 ℃ for aging for 2 d.
(6) And (3) putting the wet gel obtained after aging into a high-pressure reaction kettle of a supercritical drying device, performing supercritical drying in an absolute ethyl alcohol atmosphere, wherein the supercritical drying temperature is 280 ℃, the heat preservation time is 100min, and the pressure is 10MPa, and discharging the gas in the high-pressure reaction kettle after drying is finished to obtain the bulk cerium oxide aerogel.
(7) The density of the obtained bulk ceria composite aerogel is 0.235g/cm 3And a specific surface area of 386m2(iv) a porosity of 98.1%.
Example 5
(1) Preparing a cerium salt precursor solution: will be provided with27.62g Ce2(CO3)3·xH2O was added to 60mL of anhydrous ethanol, wherein [ Ce ]3+]Sealing the solution with preservative film at 1.0mol/L, and stirring the solution on a magnetic stirrer until the solution is completely dissolved.
(2) Addition of 3mL polyacrylic acid PAA (M) was continuedn130000), stir until the solution is clear.
(3) And (3) adding 12mL of propylene oxide into the precursor solution containing the cerium salt in the step (2), and stirring for 1min until the mixture is uniform to form sol.
(4) Pouring the sol into a culture dish, sealing with a preservative film, and forming wet gel at room temperature.
(5) The wet gel was placed in a glass dish containing absolute ethanol/absolute methanol (V/V ═ 3:1) and aged in an oven at 40 ℃ for 5 days.
(6) And (3) putting the wet gel obtained after aging into a high-pressure reaction kettle of a supercritical drying device, performing supercritical drying in an absolute ethyl alcohol atmosphere, wherein the supercritical drying temperature is 300 ℃, the heat preservation time is 120min, the pressure is 12MPa, and discharging the gas in the high-pressure reaction kettle after drying is finished to obtain the bulk cerium oxide aerogel.
(7) The obtained bulk ceria aerogel had a density of 0.129g/cm3The specific surface area is 5000m2(ii) a porosity of 98.2%.
Example 6
(1) Preparing a cerium salt precursor solution: 43.83g of Ce2(SO4)3·8H2O is added to 60mL of absolute ethanol, wherein [ Ce ]3+]Sealing the solution by using a preservative film, and putting the solution on a magnetic stirrer to stir until the solution is completely dissolved.
(2) 0.6mL polyacrylic acid PAA (M) was addedn3000) until the solution is clear.
(3) And (3) adding 8mL of propylene oxide into the precursor solution containing the cerium salt in the step (2), and stirring for 1min until the mixture is uniform to form sol.
(4) Pouring the sol into a culture dish, sealing with a preservative film, and forming wet gel at room temperature.
(5) The wet gel was placed in a glass dish containing absolute ethanol/isopropanol (V/V ═ 3:1) and aged in an oven at 40 ℃ for 5 days.
(6) Putting the aged wet gel into a high-pressure reaction kettle of a supercritical drying device, and adding CO when the temperature of the high-pressure reaction kettle reaches 45 DEG C2Pumping into a high-pressure reaction kettle, and when the pressure of the high-pressure reaction kettle reaches 10MPa, enabling the system to reach a supercritical state; maintaining for 90 min; after the drying is finished, discharging CO in the high-pressure reaction kettle2And obtaining the bulk cerium oxide aerogel.
(7) The obtained bulk ceria aerogel had a density of 0.145g/cm3The specific surface area is 450m2The porosity was 96.3%.
Example 7
(1) Preparing a cerium salt precursor solution: 5.71g of Ce (Ac) 3·nH2O was added to 60mL of anhydrous ethanol, wherein [ Ce ]3+]Sealing the solution with preservative film at 0.3mol/L, and stirring the solution on a magnetic stirrer until the solution is completely dissolved.
(2) 5mL of formamide was added and stirred until the solution was clear.
(3) And (3) adding 3mL of propylene oxide into the precursor solution containing cerium salt in the step (2), and stirring for 1min until the solution is uniform to form sol.
(4) Pouring the sol into a culture dish, sealing by using a preservative film, and forming wet gel at room temperature.
(5) The wet gel was placed in a glass dish containing anhydrous methanol and aged in an oven at 40 ℃ for 5 days.
(6) Putting the aged wet gel into a high-pressure reaction kettle of a supercritical drying device, and adding CO when the temperature of the high-pressure reaction kettle reaches 60 DEG C2Pumping into a high-pressure reaction kettle, and when the pressure of the high-pressure reaction kettle reaches 12MPa, enabling the system to reach a supercritical state; maintaining for 120 min; after the drying is finished, discharging CO in the high-pressure reaction kettle2And obtaining the bulk cerium oxide aerogel.
(7) The bulk ceria aerogel obtained had a density of 0.185g/cm3Having a specific surface area of 445m2Per g, porosity 96.7%.
Example 8
(1) Preparation of cerium salt precursorBody solution: 52.2g of Ce (NO)3)3·6H2O is added to 60mL of absolute ethanol, wherein [ Ce ]3+]Sealing the solution with a preservative film, and putting the solution on a magnetic stirrer to stir until the solution is completely dissolved, wherein the concentration of the preservative film is 2.0 mol/L.
(2) Formamide was added in an additional 5mL and stirred until the solution was clear.
(3) And (3) adding 30mL of propylene oxide into the precursor solution containing the cerium salt in the step (2), and stirring for 1min until the mixture is uniform to form sol.
(4) Pouring the sol into a culture dish, sealing with a preservative film, and putting into an oven at 70 ℃ to form wet gel.
(5) The wet gel was placed in a glass dish with isopropanol and placed in an oven at 40 ℃ for aging for 5 days.
(6) Putting the aged wet gel into a high-pressure reaction kettle of a supercritical drying device, and adding CO when the temperature of the high-pressure reaction kettle reaches 75 DEG C2Pumping into a high-pressure reaction kettle, and when the pressure of the high-pressure reaction kettle reaches 15MPa, enabling the system to reach a supercritical state; maintaining for 150 min; after the drying is finished, discharging CO in the high-pressure reaction kettle2And obtaining the bulk cerium oxide aerogel.
(7) The bulk ceria aerogel obtained had a density of 0.321g/cm3A specific surface area of 313m2The porosity was 94.2%.
Comparative example: the rest was the same as example 1 except that additives such as formamide, polyethylene glycol and polyacrylic acid were not added. Because no additives such as formamide, polyethylene glycol, polyacrylic acid and the like are added, gel cannot be obtained, and only precipitation can be obtained. The density of the powder was 0.67g/cm 3A specific surface area of 10m2/g。
As can be seen from the comparison between the comparative examples and the ceria aerogel prepared in examples 1 to 8, the addition of the additives such as polyacrylic acid can form a three-dimensional network structure on the wet gel, so that the ceria aerogel is finally bulk, rather than powder. The formation of the bulk aerogel can effectively increase the specific surface area and porosity of cerium dioxide and reduce the density of the aerogel. The key performances are mainly promoted by adding the additive, the additive is added into the system to form the effects of hydrogen bond and coordination bond, and then the propylene oxide gel accelerator is added to form a three-dimensional network structure.
Fig. 1 is a microscopic morphology of the aerogel sample obtained in example 1, and it can be seen that the structure formed by stacking nanoparticles is obtained, which is consistent with the microscopic morphology of the aerogel prepared in the conventional sense.
The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby, and any modification made on the basis of the technical scheme according to the technical idea proposed by the present invention falls within the protection scope of the present invention; the technology not related to the invention can be realized by the prior art.

Claims (5)

1. A method for preparing bulk cerium oxide aerogel by taking an epoxy compound as a gel accelerator is characterized by comprising the following specific preparation steps:
1) dissolving inorganic or organic metal cerium salt in absolute ethyl alcohol to prepare a metal cerium salt precursor solution, wherein the concentration of the metal cerium salt is 0.01-10.0 mol/L;
2) respectively adding additives with different contents and different types into the metal cerium salt precursor solution; the additive is one or more of formamide, polyvinyl alcohol with different molecular weights and polyacrylic acid with different molecular weights;
3) adding the epoxy compound solution into the solution obtained in the step 2), quickly stirring, sealing, and then placing in an environment of 25-70 ℃ for treatment for a certain time to obtain wet gel; the volume ratio of the epoxy compound solution to the solution obtained in the step 2) is 1/100-1/1;
4) immersing the obtained wet gel in an aging solution at the temperature of 25-70 ℃, and performing aging treatment for 2-7 d; the aging liquid is one or more of isopropanol, absolute ethyl alcohol or absolute methyl alcohol;
5) putting the wet gel after the aging treatment into a high-pressure reaction kettle of a supercritical drying device, and performing supercritical drying by adopting ethanol or carbon dioxide as a supercritical medium, wherein the temperature of the ethanol supercritical drying is 260-300 ℃, the heat preservation time is 10-120min, and the pressure is 7-12 MPa; the temperature of carbon dioxide supercritical drying is 45-75 deg.C, the heat preservation time is 90-150min, and the pressure is 10-15 MPa; and after drying, discharging the gas in the high-pressure reaction kettle to obtain the massive metal oxide aerogel.
2. The method for preparing a bulk cerium oxide aerogel using an epoxy compound as a gel promoter according to claim 1, wherein: the inorganic or organic metal cerium salt is Ce2(SO4)3,Ce2(SO4)3·8H2O,Ce(COOCH3)3,Ce(Ac)3·nH2O,Ce(NO3)3,Ce(NO3)3·6H2O,CeCl3,CeCl3·7H2O,Ce2(CO3)3,Ce2(CO3)3·xH2O,Ce2(C2O4)3,Ce2(C2O4)3·xH2Any one or more of O.
3. The method for preparing a bulk cerium oxide aerogel using an epoxy compound as a gel promoter according to claim 1, wherein: the epoxy compound comprises one or more of ethylene oxide, propylene oxide, epichlorohydrin and butylene oxide, and the concentration of the epoxy compound is 0-30 mol/L.
4. The method for preparing a bulk cerium oxide aerogel using an epoxy compound as a gel promoter according to claim 1, wherein: the adopted aging liquid contains isopropanol, absolute ethyl alcohol and absolute methyl alcohol or mixed liquid of the isopropanol, the absolute ethyl alcohol and the absolute methyl alcohol in different proportions.
5. The method for preparing a bulk cerium oxide aerogel using an epoxy compound as a gel promoter according to claim 1, wherein: the final concentration of the additive in the step 2) is 0-30 mol/L.
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