CN114433063B - Cerium-zirconium composite oxide and preparation method thereof - Google Patents

Cerium-zirconium composite oxide and preparation method thereof Download PDF

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CN114433063B
CN114433063B CN202210034296.3A CN202210034296A CN114433063B CN 114433063 B CN114433063 B CN 114433063B CN 202210034296 A CN202210034296 A CN 202210034296A CN 114433063 B CN114433063 B CN 114433063B
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zirconium
cerium
composite oxide
oxide
zirconium composite
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CN114433063A (en
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谭志伟
黄英强
陈涛
谭程校
万国江
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Jiangmen Kanhoo Industry Co ltd
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
    • 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
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • 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
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/64—Platinum group metals with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/656—Manganese, technetium or rhenium
    • B01J23/6562—Manganese
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    • 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
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
    • B01J35/40—
    • B01J35/613—
    • B01J35/635—
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/03—Precipitation; Co-precipitation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/101—Three-way catalysts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
    • F23G7/06—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases
    • F23G7/07—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases in which combustion takes place in the presence of catalytic material
    • 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
    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
    • Y—GENERAL 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • Y—GENERAL 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Abstract

The invention discloses a cerium-zirconium composite oxide and a preparation method thereof, belonging to the field of composite oxide materials. The cerium-zirconium composite oxide comprises the following components in percentage by weight: 50-80% of zirconium dioxide, 10-40% of cerium dioxide, 1-20% of rare earth metal oxide except cerium and 0-10% of transition metal oxide except zirconium. In the preparation method of the cerium-zirconium composite oxide, a zirconium precursor with the median particle size of 0.5-8 mu m is prepared, then the zirconium precursor, rare earth metal ions and transition metal ions are subjected to coprecipitation reaction to prepare cerium-zirconium composite hydroxide with the median particle size of 1-8 mu m, and a cerium-zirconium composite oxide blocky finished product with the secondary particle size of 1-8 mu m can be obtained by roasting. After the finished product is crushed to the median particle size of 3-5 mu m, the product still has larger pore volume and specific surface area, and the specific surface area attenuation rate after aging for 4 hours at 1100 ℃ before and after fine crushing is lower than 10%.

Description

Cerium-zirconium composite oxide and preparation method thereof
Technical Field
The invention belongs to the field of composite oxide materials, and particularly relates to a cerium-zirconium composite oxide and a preparation method thereof.
Background
The cerium-zirconium composite oxide is a functional material with oxygen storage capacity, can realize high dispersion of noble metals so as to improve the utilization efficiency of the noble metals, and is widely applied to the field of catalyst carriers. The catalytic material is generally required to operate for a long time under high temperature conditions, and therefore the cerium-zirconium composite oxide material is required to have good heat resistance and a low specific surface area decay rate to provide good catalytic capability. In the application of automobile exhaust purification, the cerium-zirconium composite oxide is applied to a three-way catalyst as an oxygen storage material. The three-way catalyst needs to work at 400-800 ℃ for a long time, and a high specific surface area and a rich porous structure must be maintained even under severe aging conditions of 1000 ℃ or more. In the field of catalytic combustion of organic volatile matters, the cerium-zirconium composite oxide serving as a catalyst carrier realizes catalytic degradation of the organic volatile matters for a long time at the temperature of about 500 ℃. The cerium-zirconium composite oxide has the phenomena of pore collapse and specific surface area reduction after long-time high-temperature aging, so that noble metals loaded on the surface and pore channels of the cerium-zirconium composite oxide are embedded. The noble metal loses catalytic activity after being embedded, so that the catalytic effect of the catalyst is reduced. Therefore, the thermal decay rate of the specific surface area of the cerium-zirconium composite oxide has a great influence on the performance thereof after high-temperature aging.
At present, the industrial preparation method of the cerium-zirconium composite oxide mainly comprises an ammonia-water complex coprecipitation method, a sulfate coordination coprecipitation method and a hydrothermal method. The ammonia water complex coprecipitation method is characterized in that ammonia water is used as a precipitator, a mixed solution of zirconium and rare earth ions is dripped into the ammonia water for precipitation reaction, hydroxide precipitate with uniformly distributed elements is obtained, and then the hydroxide precursor is roasted at high temperature to obtain a composite oxide with large specific surface area; the hydrothermal method is to crystallize the amorphous hydroxide powder after the coprecipitation reaction is finished under the conditions of high temperature and high pressure to obtain the hydroxide powder with high crystallinity. Then, carrying out high-temperature roasting to obtain a finished product of the composite oxide; the sulfate coordination coprecipitation method is to coordinate sulfate and zirconium ions into a complex, then to use sodium hydroxide as a precipitant to precipitate and convert zirconium and rare earth elements to obtain a porous hydroxide precursor, and then to roast to obtain the product.
The secondary particle size of the cerium-zirconium composite oxide prepared by the existing ammonia water complex coprecipitation method, hydrothermal method and sulfate coordination coprecipitation method is about 15-40 μm, and the finished product has larger pore volume and aging specific surface area when the median particle size is larger than 20 μm. However, when the cerium-zirconium composite oxide is finely pulverized, the secondary particle size is pulverized from about 15 to 40 μm to 5 μm or less. The mechanical grinding action in the crushing process can destroy the secondary particle structure of the cerium-zirconium composite oxide, so that the pore volume of the material and the specific surface area after high-temperature aging at 1100 ℃ are greatly reduced. Because the cerium-zirconium composite oxide is generally required to be crushed to the median particle size of about 3-5 μm at the application end, the reduction of the pore volume and the aging specific surface area caused in the crushing process can influence the performance of the noble metal-loaded catalyst. Therefore, there is an urgent need to develop a pulverization-resistant cerium-zirconium composite oxide having a small secondary particle size, which can prevent a material from being deteriorated to a large extent in specific surface area after being pulverized into small particles.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a cerium-zirconium composite oxide and a preparation method thereof.
In order to realize the purpose, the invention adopts the technical scheme that: a cerium-zirconium composite oxide comprises the following components in percentage by weight: 50-80% of zirconium dioxide, 10-40% of cerium dioxide, 1-20% of oxides of rare earth metals except cerium and 0-10% of oxides of transition metals except zirconium; the secondary particle size of the cerium-zirconium composite oxide is 1-8 mu m; the cerium-zirconium composite oxide is crushed to the median particle size of 3-5 mu m or less, and the attenuation of the specific surface area is lower than 10 percent after aging for 4 hours at 1100 ℃.
The cerium-zirconium composite oxide prepared by the invention comprises zirconium dioxide, cerium dioxide, oxides of other rare earth metals except cerium and oxides of other transition metals except zirconium. The cerium-zirconium composite oxide prepared by the invention has the secondary particle size of 1-8 mu m, and has smaller secondary particle size compared with the cerium-zirconium composite oxide prepared by the traditional method. Therefore, when the bulk cerium-zirconium composite oxide is pulverized to a median particle size of 3 to 5 μm, the secondary particles of the cerium-zirconium composite oxide are not damaged so much, and the large pore volume and specific surface area before pulverization are retained after pulverization, and the specific surface area decay rate after high-temperature aging is also lower.
In a preferred embodiment of the present invention, the transition metal oxide other than zirconium includes at least one of niobium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, and copper oxide; the rare earth metal oxide other than cerium comprises at least one of yttrium oxide, lanthanum oxide, praseodymium oxide and neodymium oxide.
The inventors have found through studies that a series of cerium-zirconium composite oxides containing the above-mentioned different kinds of transition metals and rare earth metals are prepared by the present invention. The cerium-zirconium composite oxide contains adjustable types and contents of components, the prepared composite oxide can keep large pore volume and high comparative area after being crushed, and the specific surface area attenuation rate is low after high-temperature aging.
The invention also provides a preparation method of the cerium-zirconium composite oxide, which comprises the following steps:
(1) Adding alkali into a zirconium salt solution, and reacting at 90-100 ℃ for 2-6h to obtain zirconium hydroxide sol;
(2) Uniformly mixing the zirconium hydroxide sol obtained in the step (1) with sulfuric acid and/or a sulfate solution, and curing at 95-100 ℃ for 15-120min to obtain zirconium precursor slurry;
(3) Uniformly mixing the zirconium precursor slurry obtained in the step (2) with a rare earth metal salt solution and a transition metal salt solution at 40-60 ℃, adding an alkali solution for reaction, filtering and washing to obtain a precipitate;
(4) Uniformly mixing the precipitate obtained in the step (3) with a solvent and a structure regulator to obtain mixed slurry; the structure modifier comprises an organic acid or an organic base;
(5) And (4) sequentially filtering, washing, roasting and crushing the mixed slurry obtained in the step (4) to obtain the cerium-zirconium composite oxide.
The inventor finds that the secondary particle size of the cerium-zirconium composite oxide prepared by the traditional ammonia water complexing coprecipitation method, the hydrothermal method and the sulfate coordination coprecipitation method is large, and although the particle size of the finished product is larger than 10 mu m and has larger pore volume and aging specific surface area, when the finished product is finely crushed, the reduction of the secondary particle size and the structural damage of the secondary particle can cause the great reduction of the pore volume of the material and the specific surface area after high-temperature aging at 1100 ℃. Firstly, preparing a zirconium precursor with the median particle size of 0.5-8 mu m through precipitation and curing, and then carrying out coprecipitation reaction on the zirconium precursor, rare earth ions and transition metal ions to prepare a cerium-zirconium composite hydroxide precipitate with the median particle size of 1-8 mu m; modifying the obtained precipitate with a structure regulator, and roasting to obtain a cerium-zirconium composite oxide blocky finished product with the secondary particle size of 1-8 mu m, wherein the finished product is crushed to the median particle size of 3-5 mu m on the application end without causing great reduction of the pore volume and the specific surface area. The preparation method is simple and efficient, and can prepare the cerium-zirconium composite oxide containing different transition metals and rare earth metal elements.
As a preferred embodiment of the present invention, in the step (1), the zirconium salt includes zirconium oxychloride and/or zirconium nitrate.
As a preferred embodiment of the present invention, in the steps (1) and (3), the alkali includes at least one of urea, ammonia water, sodium hydroxide, and potassium hydroxide.
In a preferred embodiment of the present invention, in the step (1), the base is urea.
The inventor finds that the solution is clear after urea is added into a zirconium salt solution at room temperature, the urea is slowly hydrolyzed into ammonia and carbon dioxide in the process of heating to 90-100 ℃ and preserving heat for 2-6h, at the moment, the ammonia and zirconium ions generate homogeneous reaction to generate zirconium hydroxide white colloidal solution, and a zirconium precursor with the median particle size of 0.5-8 mu m can be prepared after further reaction with sulfate radicals, so that the particle size of secondary particles of a product can be continuously controlled at the beginning of preparation of the precursor of the product.
As a preferred embodiment of the present invention, in the step (1), the molar ratio of the alkali to the zirconium salt is (0.5 to 0.8): 1.
the inventor finds that the molar ratio of alkali to zirconium salt is less than 0.5:1, the zirconium salt can not be completely precipitated, and the molar ratio is more than 0.8: the particle size of the zirconium precursor formed in the step 1 is increased, so that the particle size in the subsequent preparation process is increased, and the pore volume and the specific surface area are greatly attenuated after crushing.
In a preferred embodiment of the present invention, in the step (2), the sulfate includes at least one of ammonium sulfate, sodium sulfate, potassium sulfate, and sulfuric acid.
As a preferred embodiment of the present invention, the molar ratio of sulfate in the sulfuric acid and/or sulfate solution in step (2) to the zirconium salt in step (1) is (0.45-0.7): 1.
the inventor finds that if the dosage of the sulfate radical is low, the zirconium ion reaction is incomplete, and the final product cannot form a solid solution.
As a preferred embodiment of the present invention, in the step (2), the median particle size of the zirconium precursor in the slurry of zirconium precursor is 0.5 to 8 μm.
The inventor finds that a zirconium precursor with the median particle size of 0.5-8 mu m is prepared, then the zirconium precursor, rare earth ions and transition metal ions are subjected to coprecipitation reaction to prepare the cerium-zirconium composite hydroxide with the median particle size of 1-8 mu m, and the cerium-zirconium composite hydroxide is roasted to obtain a cerium-zirconium composite oxide blocky finished product with the secondary particle size of 1-8 mu m.
As a preferred embodiment of the present invention, in the step (2), the median particle size of the zirconium precursor in the slurry of zirconium precursor is 3 to 7 μm.
The inventor finds that when the median particle size of a zirconium precursor in zirconium precursor slurry is 3-7 mu m, the subsequently prepared cerium-zirconium composite hydroxide has more uniform median particle size distribution, the cerium-zirconium composite oxide has uniform secondary particle size distribution, and the aging specific surface area attenuation rate is low before and after crushing to 3-5 mu m.
As a preferred embodiment of the present invention, in the step (3), the rare earth metal salt solution and the transition metal salt solution include a chloride salt and/or a nitrate salt solution.
In a preferred embodiment of the present invention, in the step (3), the concentration by mass of the rare earth metal salt solution and the transition metal salt solution is 10 to 30%.
As a preferred embodiment of the present invention, in the step (3), the median particle size of the precipitate is 1 to 8 μm.
The inventors have found that, since the particle size of the secondary particles of the cerium-zirconium composite hydroxide is substantially the same as that of the secondary particles of the cerium-zirconium oxide obtained by calcination, the smaller the median particle size of the precipitate of the cerium-zirconium composite oxide prepared by the present invention is, the smaller the particle size of the finally prepared cerium-zirconium composite hydroxide is, the more effectively prevented is the problem that the secondary particle structure after pulverization is destroyed, the pore structure collapses, and the aging specific surface area becomes lower as the pore volume and pore diameter become smaller.
As a preferred embodiment of the present invention, in the step (3), the median particle size of the precipitates is 3 to 7 μm.
As a preferred embodiment of the present invention, in the step (4), the solvent includes water and/or ethanol.
As a preferred embodiment of the present invention, in the step (4), the organic acid includes at least one of 6-aminocaproic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, octadecanoic acid, oleic acid, and citric acid; the organic alkali comprises at least one of dodecylamine, oleylamine, trioctyl decyl tertiary amine, n-decyl amine, tetramethyl ammonium hydroxide and hexadecyl trimethyl ammonium hydroxide.
In the step (4), the mass ratio of the structure-controlling agent to the product cerium-zirconium composite oxide is (0.2-0.5): 1.
The inventor researches and discovers that the structure regulator accounts for less than 20% of the target product, namely the cerium-zirconium composite oxide, sintering phenomenon can be generated in the roasting process, and the product granularity is increased. The structure regulator exceeding 50% has no influence on the product particle size, but the preparation cost is increased.
As a preferred embodiment of the present invention, in the step (5), the calcination is performed at 700 to 800 ℃ for 4 hours.
Compared with the prior art, the invention has the beneficial effects that:
(1) The cerium-zirconium composite oxide of the present invention has a large pore volume and a large specific surface area when pulverized to a small particle size, and has a specific surface area of 80 to 90m when pulverized to a median particle size of 3 to 5 μm 2 Per g, pore volume of 0.5-0.6cm 3 G, the specific surface area is 30-40m after aging for 4h at 1100 DEG C 2 /g。
(2) The cerium-zirconium composite oxide has low attenuation rate of aging surface area before and after crushing, and the attenuation rate of specific surface area after aging for 4 hours at 1100 ℃ before and after crushing is lower than 10%.
Detailed Description
To better illustrate the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to specific examples and comparative examples.
The cerium-zirconium composite oxide in examples 1 to 5 includes the following components in percentage by weight: 50-80% of zirconium dioxide, 10-40% of cerium dioxide, 1-20% of oxides of rare earth metals except cerium and 0-10% of oxides of transition metals except zirconium. The specific preparation method of the embodiments 1-5 of the invention comprises the following steps: preparing a zirconium precursor with the median particle size of 0.5-8 mu m, curing, then carrying out coprecipitation reaction on the zirconium precursor, rare earth ions and transition metal ions to prepare cerium-zirconium composite hydroxide with the median particle size of 1-8 mu m, and treating and roasting the cerium-zirconium composite hydroxide by using a structure regulator to obtain a cerium-zirconium composite oxide blocky finished product with the secondary particle size of 1-8 mu m.
Example 1
Embodiment 1 is an embodiment of the cerium-zirconium composite oxide of the present invention, which includes the following components in percentage by weight: 60% of zirconium oxide, 30% of cerium oxide, 5% of lanthanum oxide and 5% of yttrium oxide.
The preparation method comprises the following steps: (1) To a 4% by weight solution of zirconium oxychloride was added urea in a molar ratio of urea to zirconium oxychloride of 0.5. Stirring and heating to 95 ℃, and then preserving heat for reaction for 6 hours to obtain the zirconium hydroxide sol. (2) Then, adding a 20wt% sulfuric acid solution to the zirconium hydroxide slurry, wherein the molar ratio of sulfate to zirconium salt is 0.56:1. and continuously stirring and curing for 60min at the temperature of 95 ℃ to obtain a zirconium precursor. (3) And (3) after the temperature of the zirconium precursor slurry is reduced to 60 ℃, adding a cerium chloride solution, a lanthanum chloride solution and a yttrium chloride solution, and stirring and mixing uniformly. Then adding 15Wt% sodium hydroxide solution into the mixed metal salt solution until the pH value of the slurry reaches above 12 to obtain the cerium-zirconium composite hydroxide precipitate. Filtering the cerium-zirconium composite hydroxide, and washing with deionized water to remove impurity ions. (4) And (3) dispersing the washed cerium-zirconium composite hydroxide in absolute ethyl alcohol by using a high-speed dispersion machine. Then the slurry was heated to 50 ℃ and oleic acid was added and stirred for 60min. The addition amount of oleic acid was 50% by weight of the target product. (5) Filtering the slurry treated by the structure regulator, and then drying in vacuum to remove the solvent. And then roasting the filter cake of the cerium-zirconium composite hydroxide after vacuum drying at 800 ℃ for 4 hours to obtain the porous cerium-zirconium composite oxide. And (3) crushing the calcined zirconium-based rare earth composite oxide into powder by using a crusher.
Example 2
Embodiment 2 is an embodiment of the cerium-zirconium composite oxide of the present invention, which includes the following components in percentage by weight: 50% of zirconium oxide, 40% of cerium oxide, 5% of lanthanum oxide and 5% of yttrium oxide.
The preparation method comprises the following steps: (1) To a solution of zirconium oxychloride with a concentration of 6% by weight, urea is added, the molar ratio of urea to zirconium oxychloride being 0.8. Stirring and heating to 90 ℃, and then preserving heat for reaction for 3 hours to obtain the zirconium hydroxide sol. (2) Then, a mixed solution of sulfuric acid and sodium sulfate having a concentration of 20wt% was added to the zirconium hydroxide slurry, wherein the molar ratio of the sulfate to the zirconium salt was 0.7:1, the molar ratio of sulfuric acid to sodium sulfate is 1. And continuously stirring and curing for 15min at the temperature of 95 ℃ to obtain a zirconium precursor. (3) And (3) cooling the zirconium precursor slurry to 50 ℃, adding a cerium chloride solution, a lanthanum chloride solution and a yttrium chloride solution, and stirring and mixing uniformly. Then adding a sodium hydroxide solution with the concentration of 25Wt% into the obtained mixed metal salt solution until the PH value of the slurry reaches more than 12, and obtaining the cerium-zirconium composite hydroxide precipitate. Filtering the cerium-zirconium composite hydroxide, and washing with deionized water to remove impurity ions. (4) And (3) dispersing the washed cerium-zirconium composite hydroxide in absolute ethyl alcohol by using a high-speed dispersion machine. Then the slurry was heated to 50 ℃ and stearic acid was added and stirred for 60min. The addition amount of the octadecanoic acid is 40% of the weight of the target product. (5) Filtering the slurry treated by the structure regulator, and then drying in vacuum to remove the solvent. And then roasting the filter cake of the cerium-zirconium composite hydroxide after vacuum drying at 800 ℃ for 4 hours to obtain the porous cerium-zirconium composite oxide. And (3) crushing the calcined zirconium-based rare earth composite oxide into powder by using a crusher.
Example 3
Embodiment 3 is an embodiment of the cerium-zirconium composite oxide of the present invention, including the following components in percentage by weight: 80% of zirconium oxide, 10% of cerium oxide, 2% of lanthanum oxide and 8% of yttrium oxide.
The preparation method comprises the following steps: (1) To a 5% by weight solution of zirconium oxychloride was added urea in a molar ratio of urea to zirconium oxychloride of 0.6. Stirring and heating to 95 ℃, and then preserving heat for reaction for 4 hours to obtain zirconium hydroxide sol. (2) Then adding a 20wt% sulfuric acid solution to the zirconium hydroxide slurry, wherein the molar ratio of sulfate to zirconium salt is 0.45:1. and continuously stirring and curing for 120min at the temperature of 95 ℃ to obtain a zirconium precursor. (3) And (3) cooling the zirconium precursor slurry to 50 ℃, adding a cerium chloride solution, a lanthanum chloride solution and a yttrium chloride solution, and stirring and mixing uniformly. Then adding a sodium hydroxide solution with the concentration of 10Wt% into the obtained mixed metal salt solution until the PH value of the slurry reaches more than 12, and obtaining the cerium-zirconium composite hydroxide precipitate. Filtering the cerium-zirconium composite hydroxide, and washing with deionized water to remove impurity ions. (4) And (3) dispersing the washed cerium-zirconium composite hydroxide in absolute ethyl alcohol by using a high-speed dispersion machine. Then the slurry is heated to 50 ℃, and dodecylamine and octadecanoic acid are added and stirred for 60min. The addition amount of the dodecylamine and the octadecanoic acid is 40% of the weight of the target product, and the molar ratio of the dodecylamine to the octadecanoic acid is 1. (5) Filtering the slurry treated by the structure regulator, and then drying in vacuum to remove the solvent. And then roasting the filter cake of the cerium-zirconium composite hydroxide after vacuum drying at 700 ℃ for 4h to obtain the porous cerium-zirconium composite oxide. And (3) crushing the calcined zirconium-based rare earth composite oxide into powder by using a crusher.
Example 4
Embodiment 4 is an embodiment of the cerium-zirconium composite oxide of the present invention, which includes the following components in percentage by weight: 60% of zirconium oxide, 25% of cerium oxide, 2% of lanthanum oxide, 3% of yttrium oxide and 10% of manganese dioxide.
The preparation method comprises the following steps: (1) To a 5% by weight solution of zirconium oxychloride was added urea in a molar ratio of urea to zirconium oxychloride of 0.5. Stirring and heating to 100 ℃, and then keeping the temperature for reaction for 5 hours to obtain the zirconium hydroxide sol. (2) Then, a 20wt% sulfuric acid solution was added to the zirconium hydroxide slurry, wherein the molar ratio of sulfate to zirconium salt was 0.62:1. and continuously stirring and curing for 120min at the temperature of 95 ℃ to obtain a zirconium precursor. (3) And (3) cooling the zirconium precursor slurry to 50 ℃, adding cerium chloride, lanthanum chloride, yttrium chloride and manganese chloride solution, and stirring and mixing uniformly. Then adding a sodium hydroxide solution with the concentration of 20Wt% into the obtained mixed metal salt solution until the PH value of the slurry reaches more than 12, and obtaining the cerium-zirconium composite hydroxide precipitate. Filtering the cerium-zirconium composite hydroxide, and washing with deionized water to remove impurity ions. (4) And (3) dispersing the washed cerium-zirconium composite hydroxide in deionized water by using a high-speed dispersion machine. Then the slurry is heated to 50 ℃, and 6-aminocaproic acid is added and stirred for 30min. The addition amount of the 6-aminocaproic acid is 50 percent of the weight of the target product. (5) Filtering the slurry treated by the structure regulator, and then drying in vacuum to remove the solvent. And roasting the filter cake of the cerium-zirconium composite hydroxide after vacuum drying at 800 ℃ for 4 hours to obtain the porous cerium-zirconium composite oxide. And (3) crushing the calcined zirconium-based rare earth composite oxide into powder by using a crusher.
Example 5
Embodiment 5 is an embodiment of the cerium-zirconium composite oxide of the present invention, including the following components in weight percent: 50% of zirconium oxide, 28% of cerium oxide, 10% of lanthanum oxide, 10% of yttrium oxide and 2% of iron oxide.
The preparation method comprises the following steps: (1) To a 5% by weight solution of zirconium oxychloride was added urea in a molar ratio of urea to zirconium oxychloride of 0.5. Stirring and heating to 100 ℃, and then preserving heat for reaction for 6 hours to obtain the zirconium hydroxide sol. (2) Then, a 20wt% sulfuric acid solution was added to the zirconium hydroxide slurry, wherein the molar ratio of sulfate to zirconium salt was 0.64:1. and continuously stirring and curing for 30min at the temperature of 100 ℃ to obtain the zirconium precursor. (3) And (3) cooling the zirconium precursor slurry to 40 ℃, adding cerium chloride, lanthanum chloride, yttrium chloride and ferric chloride solution, and stirring and mixing uniformly. Then adding 30Wt% sodium hydroxide solution into the mixed metal salt solution until the pH value of the slurry reaches above 12 to obtain the cerium-zirconium composite hydroxide precipitate. Filtering the cerium-zirconium composite hydroxide, and washing with deionized water to remove impurity ions. (4) And dispersing the washed cerium-zirconium composite hydroxide into deionized water by using a high-speed dispersion machine. The slurry was then warmed to 40 ℃ and stirred for 30min with cetyl trimethylammonium hydroxide. The amount of cetyltrimethylammonium hydroxide added was 20% by weight of the target product. (5) Filtering the slurry treated by the structure regulator, and then drying in vacuum to remove the solvent. And roasting the filter cake of the cerium-zirconium composite hydroxide after vacuum drying at 800 ℃ for 4 hours to obtain the porous cerium-zirconium composite oxide. And (3) crushing the calcined zirconium-based rare earth composite oxide into powder by using a crusher.
Comparative example 1
Comparative example 1 is a comparative example of the cerium-zirconium composite oxide of the present invention, comprising the following components in percentage by weight: 50% of zirconium oxide, 40% of cerium oxide, 5% of lanthanum oxide and 5% of yttrium oxide.
The preparation method comprises the following steps: (1) To a solution of zirconium oxychloride with a concentration of 4% by weight, the temperature was raised to 95 ℃ and a solution of sodium sulfate with a concentration of 20% by weight was added, the amount of sodium sulfate being 70% by weight of the zirconium oxide. (2) And continuously stirring and curing for 60min at the temperature of 95 ℃ to obtain a zirconium precursor. (3) And (3) after the temperature of the zirconium precursor slurry is reduced to 60 ℃, adding a cerium chloride solution, a lanthanum chloride solution and a yttrium chloride solution, and stirring and mixing uniformly. Then adding 15Wt% sodium hydroxide solution into the mixed metal salt solution until the pH value of the slurry reaches above 12 to obtain the cerium-zirconium composite hydroxide precipitate. Filtering the cerium-zirconium composite hydroxide, and washing with deionized water to remove impurity ions. (4) And (3) dispersing the washed cerium-zirconium composite hydroxide in absolute ethyl alcohol by using a high-speed dispersion machine. Then the slurry was warmed to 50 ℃ and oleic acid was added and stirred for 60min. The addition amount of oleic acid was 50% by weight of the target product. (5) Filtering the slurry treated by the structure regulator, and then drying in vacuum to remove the solvent. And roasting the filter cake of the cerium-zirconium composite hydroxide after vacuum drying at 800 ℃ for 4 hours to obtain the porous cerium-zirconium composite oxide. And (3) crushing the calcined zirconium-based rare earth composite oxide into powder by using a crusher.
Comparative example 2
Comparative example 2 is a comparative example of the cerium zirconium composite oxide of the present invention, comprising the following components in weight percent: 50% of zirconium oxide, 40% of cerium oxide, 5% of lanthanum oxide and 5% of yttrium oxide.
The preparation method comprises the following steps: (1) Preparing a mixed metal salt solution of zirconium nitrate, ammonium ceric nitrate, lanthanum nitrate and yttrium nitrate with the concentration of 10%. (2) Preparing 10% ammonia water solution, and the ammonia water is excessive by 30%. (3) And (3) adding the mixed metal salt solution obtained in the step (1) into the ammonia water solution obtained in the step (2) to obtain precipitation slurry. (4) And (4) adding oleic acid into the precipitation slurry obtained in the step (3) and stirring for 60min, wherein the addition amount of the oleic acid is 50% of the weight of the target product. (5) Filtering the slurry treated by the structure regulator, and then drying in vacuum to remove the solvent. And then roasting the filter cake of the cerium-zirconium composite hydroxide after vacuum drying at 800 ℃ for 4 hours to obtain the porous cerium-zirconium composite oxide. The calcined cerium-zirconium composite oxide was pulverized into powder by a pulverizer.
The inventors carried out particle size and specific surface area tests on the products of examples 1 to 5 and comparative examples 1 to 2 finely pulverized to a median particle size of about 3 to 5 μm. The specific conditions of aging are: and heating the sample to be detected to 1000 ℃ or 1100 ℃ and preserving the temperature for 4h, wherein the heating time is 4h. The specific surface area test method comprises the following steps: detection was performed using a TriStar 3020 fully automated specific surface area and void analyzer at 77K using nitrogen as the adsorbed gas. The sample is degassed at 200 deg.C for 2 hr to remove water and air in the material channel before nitrogen adsorption and desorption testing. The specific surface area is calculated by the multipoint BET method. The particle size test method comprises the following steps: the sample is subjected to ultrasonic treatment in a sodium hexametaphosphate aqueous solution for 3min, and then particle size detection is carried out by using an Euromex LS-POP (9) laser particle size analyzer. The test results of examples 1 to 5 and comparative examples 1 to 2 are shown in tables 1 to 2.
TABLE 1 BET and median particle size test results for examples 1-5 and comparative examples 1-2
Figure BDA0003465874770000111
TABLE 2 results of particle size and aged specific surface area tests before and after fine pulverization of examples 1 to 5 and comparative examples 1 to 2
Figure BDA0003465874770000112
Figure BDA0003465874770000121
As can be seen from table 1, the median particle sizes of the secondary particles of cerium zirconium composite hydroxide in the preparation process of the present invention were all less than 8 μm, which was much smaller than that of the cerium zirconium composite hydroxide in comparative examples 1-2. Since the secondary particle size of the cerium-zirconium composite hydroxide is substantially the same as that of the cerium-zirconium oxide obtained by calcination, the secondary particles of the cerium-zirconium composite oxide prepared by the present invention have a smaller particle size than that of comparative example 1-2. As is clear from examples 1 to 5, the cerium-zirconium composite oxide obtained by the preparation method of the present invention slightly increased the fresh specific surface area by finely pulverizing the cerium-zirconium composite oxide to a particle size of about 3 to 5 μm, and the pore volume and the pore diameter were substantially maintained. The cerium-zirconium composite oxide prepared by the traditional method according to the proportion of 1-2 has the particle size of secondary particles far larger than 10 mu m, and the secondary particle structure is damaged in the process of crushing to 3-5 mu m, so that the pore volume and the pore diameter are reduced, and the aging specific surface area at 1000 ℃ is lowered. Compared with the cerium-zirconium composite oxide prepared by the traditional method of comparative examples 1-2, the synthesis method of the invention has larger specific surface area which is larger than 88m 2 (iv) g. The cerium-zirconium composite oxides of examples 1 to 5 have larger pore volumes and pore diameters than those of comparative examples 1 to 2, and the pore volumes are 0.50cm 3 More than g, and the aperture reaches more than 23.9 nm.
As can be seen from table 2, in examples 1 to 5, since the secondary particles of the cerium-zirconium composite oxide were small, when the bulk cerium-zirconium composite oxide was pulverized to a median particle size of 3 to 5 μm, the secondary particles of the cerium-zirconium composite oxide were not damaged so much, and therefore, the pulverized cerium-zirconium composite oxide had a large pore volume and a large specific surface area, and the specific surface area decay rate after aging at 1100 ℃ for 4 hours was less than 10%, which is significantly superior to that of comparative examples 1 to 2.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims (6)

1. The cerium-zirconium composite oxide is characterized by comprising the following components in percentage by weight: 50-80% of zirconium dioxide, 10-40% of cerium dioxide, 1-20% of oxides of rare earth metals except cerium and 0-10% of oxides of transition metals except zirconium; the secondary particle size of the cerium-zirconium composite oxide is 1-8 mu m; the cerium-zirconium composite oxide is crushed to the median particle size of 3-5 mu m, and the attenuation of the specific surface area after aging for 4h at 1100 ℃ is lower than 10 percent; the oxide of the transition metal other than zirconium comprises at least one of niobium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide and copper oxide; the oxide of other rare earth metal except cerium comprises at least one of yttrium oxide, lanthanum oxide, praseodymium oxide and neodymium oxide;
the preparation method of the cerium-zirconium composite oxide comprises the following steps:
(1) Adding alkali into a zirconium salt solution, and reacting at 90-100 ℃ for 2-6h to obtain zirconium hydroxide sol;
(2) Uniformly mixing the zirconium hydroxide sol obtained in the step (1) with sulfuric acid and/or a sulfate solution, and curing at 95-100 ℃ for 15-120min to obtain zirconium precursor slurry;
(3) Uniformly mixing the zirconium precursor slurry obtained in the step (2) with a rare earth metal salt solution and a transition metal salt solution at 40-60 ℃, adding an alkali solution for reaction, filtering and washing to obtain a precipitate;
(4) Uniformly mixing the precipitate obtained in the step (3) with a solvent and a structure regulator to obtain mixed slurry; the structure modifier comprises an organic acid or an organic base;
(5) Filtering, washing, roasting and crushing the mixed slurry obtained in the step (4) in sequence to obtain a cerium-zirconium composite oxide;
in the step (1), the molar ratio of alkali to zirconium salt is (0.5-0.8): 1;
the molar ratio of sulfate radicals in the sulfuric acid and/or sulfate salt solution in the step (2) to zirconium salt in the step (1) is (0.45-0.7): 1.
2. the cerium-zirconium composite oxide according to claim 1, wherein the base in steps (1) and (3) comprises at least one of urea, aqueous ammonia, sodium hydroxide, and potassium hydroxide.
3. The cerium-zirconium composite oxide according to claim 1, wherein in the step (2), the median particle size of the zirconium precursor in the zirconium precursor slurry is 0.5 to 8 μm.
4. The cerium-zirconium composite oxide according to claim 1, wherein in the step (3), the median particle size of the precipitate is 1 to 8 μm.
5. The cerium-zirconium composite oxide according to claim 1, wherein in the step (4), the structure-regulating agent comprises an organic acid or an organic base; the organic acid comprises at least one of 6-aminocaproic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, stearic acid, oleic acid and citric acid; the organic alkali comprises at least one of dodecylamine, oleylamine, trioctyl decyl tertiary amine, n-decyl amine, tetramethyl ammonium hydroxide and hexadecyl trimethyl ammonium hydroxide.
6. The cerium-zirconium composite oxide according to claim 1, wherein in the step (4), the mass ratio of the structure modifier to the product cerium-zirconium composite oxide is (0.2-0.5): 1.
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