WO2020080620A1 - Preparation method of metal ion-doped ceria using solvothermal synthesis - Google Patents

Abstract

The present invention relates to a method of preparing metal ion-doped ceria using solvothermal synthesis, the method comprising the steps of: (a) regulating the pH of a cerium acetate solution by adding an alkaline material thereto; (b) regulating the pH of a metal-ion precursor solution by adding an alkaline material thereto; and (c) after dispersing each solution obtained in steps (a) and (b) in a solvent, conducting a solvothermal reaction at 90-160℃ to form metal ion-doped ceria. According to the present invention, the metal ion-doped ceria having a high specific surface area and crystallinity can be economically synthesized via solvothermal synthesis at relatively lower temperatures (90-160℃) compared to conventional solvothermal synthesis temperatures, without surfactant or additional heat treatment, wherein, in particular, the specific surface area of the metal ion-doped ceria can be dramatically improved by using cerium acetate as a cerium precursor.

Description

Method for manufacturing metal ion doped ceria using solvent heat synthesis

The present invention, (i) the National R & D project implemented by the Ministry of Education (project identification number: 1345272855, project name: regional creative innovation manpower development project, research project name: development of catalyst application oxide particle manufacturing technology by chemical process, research management agency: Korea Research Foundation, Host organization: Changwon University Industry-University Cooperation Foundation, Research Period: 2015.05.01. ~ 2018.04.30.), (Ii) National R & D Project by Ministry of Science and ICT (Detailed Number: 2018R1A5A6075959, Project: Leading Research Center Support project, research project name: Mechatronics Convergence Components Research Center, Research Management Agency: Korea Research Foundation, Host Organization: Changwon University Industry-Academy Cooperation Foundation, Research Period: 2018.09.01. ~ 2021.08.31.), (Iii) Industry Trade National R & D project conducted by the Ministry of Resources and Energy (Detailed number: 20174030201460, Project name: Energy manpower training project, Research project name: Gas turbine high-temperature parts high-efficiency convergence research and manpower training advanced track, research management agency: Korea Institute of Industrial Technology Evaluation Won, Organized by: Changwon University Industry-University Cooperation Foundation, Research Period: 2017.04.01. ~ 2021.12.31.), And (iv) National R & D Project by Ministry of Education Support project, research project name: Development of a ceramic mold for precision casting and a binder system for 3D printer for core production, research management agency: Korea Research Foundation, Host organization: Changwon University Industry-University Cooperation Foundation, Research period: 2018.09.01. ~ 2019.10 As a result of Changwon University under the research and development support of .31.), It is about a method of manufacturing a metal ion doped ceria.

 Cerium oxide, that is, ceria, is applied to a very wide range of fields, such as a solid oxide fuel cell (SOFC), an oxygen gas sensor, an ultraviolet absorber, and an abrasive, due to its unique physical and chemical properties. . Ceria oxidizes / reduces oxygen according to the surrounding oxygen concentration, has excellent oxygen storage capacity, and is widely used as a catalyst that decomposes exhaust gases of automobiles and converts them into non-toxic gases. At this time, since the activity of the catalyst depends on the surface area, it is essential to obtain a high specific surface area. Nano-sized ceria has been studied with constant interest because it has better performance of oxidation / reduction and oxygen storage (OSC) when compared to bulk powder.

On the other hand, as a method for synthesizing ceria nanoparticles, a precipitation method, a sol-gel method, and the like are representatively known, but the precipitation method and the sol-gel method require an additional high-temperature reaction process to make a powder having high crystallinity. In this process, the particles aggregate to lower the surface energy and form irregular shapes. To control this, a surfactant is added, and a process for removing the surfactant is required.

The technical problem to be solved by the present invention is that metal ion doping ceria is superior in thermal stability at high temperatures and has a large specific surface area, high purity and crystallinity, and is relatively free from surfactants or additional heat treatment, unlike the prior art. It is to provide a method for manufacturing at a low temperature.

In order to achieve the above technical problem, the present invention comprises the steps of (a) adding a basic material to a cerium acetate solution to adjust the pH; (b) adding a basic substance to the metal ion precursor solution to adjust the pH; And (c) dispersing the solution obtained in each of steps (a) and (b) in a solvent, followed by a solvent heat reaction at a temperature of 90 to 160 ° C. to form a metal ion-doped ceria; A method of manufacturing a metal ion doped ceria using a synthetic method is proposed.

In addition, in the step (b), the metal ion precursor is an acetate-based precursor, an alkoxide-based precursor, a halide-based precursor, an oxyhalide-based precursor, or a nitrate-based precursor. (nitrate based) A method of manufacturing a metal ion doped ceria using a solvent heat synthesis method, which is a precursor, is proposed.

In addition, the solvent proposes a method for producing a metal ion doped ceria using a solvent heat synthesis method, characterized in that it is water or a mixed solvent of water and alcohol.

In addition, the mixed solvent proposes a method for producing a metal ion doped ceria using a solvent heat synthesis method, characterized in that it contains less than 75% by volume of ethanol (EtOH).

In addition, the basic material is ammonium hydroxide (NH ₄ OH), sodium hydroxide (NaOH) or potassium hydroxide (KOH), it is proposed a method for producing a metal ion doped ceria using a solvent heat synthesis method.

In addition, the solvent heat reaction proposes a method for producing a metal ion doped ceria using a solvent heat synthesis method characterized in that it is carried out for 2 to 10 hours.

And, the present invention proposes a metal ion doped ceria produced by the above manufacturing method in another aspect of the invention.

Furthermore. In another aspect of the invention, the present invention proposes a catalyst for purification of exhaust gas comprising the metal ion-doped ceria as an oxygen storage capacity (OSC) material.

According to the present invention, metal ion-doped ceria having a high specific surface area and crystallinity can be economically synthesized at a temperature lower than the existing hydrothermal synthesis temperature (90-160 ° C) through a solvent heat synthesis method without a surfactant or additional heat treatment. , By using cerium acetate as a cerium precursor, it is possible to dramatically improve the specific surface area of the metal ion-doped ceria.

In addition, according to the present invention, it has various particle sizes and specific surface areas through control of process parameters such as the type of metal ions to be doped, the mixing ratio between solvents in a mixed solvent, pH, and reaction time, and exhibits higher OSC catalyst characteristics than pure ceria. Metal ion doped ceria can be synthesized.

1 is a process flow diagram of a method for producing a metal ion doped ceria using a solvent heat synthesis method according to the present invention.

2 is a process flow diagram showing each detailed process of metal ion doping ceria synthesis using a solvent heat synthesis method in the present embodiment.

3 is an X-ray diffraction analysis (XRD) result for the synthesized ruthenium doped ceria (Ru-doped CeO ₂ ) nano powder synthesized in the present example.

4 to 8 are Ru doped amount of ruthenium doped ceria (Ru-doped CeO ₂ ) nano-powder synthesized in the present embodiment (Fig. 4: 5 mol%, Fig. 5: 10 mol%, Fig. 6: 15 mol%, Figure 7: FE-TEM photograph showing the change in microstructure according to 20 mol%, Figure 8: 25 mol%).

In the description of the present invention, when it is determined that detailed descriptions of related known functions or configurations may unnecessarily obscure the subject matter of the present invention, detailed descriptions thereof will be omitted.

The embodiments according to the concept of the present invention may be modified in various ways and have various forms, and thus, specific embodiments will be illustrated in the drawings and described in detail in the present specification or application. However, this is not intended to limit the embodiment according to the concept of the present invention to a specific disclosure form, and it should be understood to include all modifications, equivalents, or substitutes included in the spirit and scope of the present invention.

The terms used in this specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “include” or “have” are intended to indicate that a feature, number, step, action, component, part, or combination thereof described is present, and one or more other features or numbers. It should be understood that it does not preclude the presence or addition possibilities of, steps, actions, components, parts or combinations thereof.

Hereinafter, the present invention will be described in detail.

The present invention relates to a novel method capable of manufacturing a metal ion doped ceria having a high specific surface area through a more economical and simple process than the conventional synthetic method.

Specifically, as shown in Figure 1, a method of manufacturing a metal ion doped ceria using a solvent heat synthesis method according to the present invention includes: (a) adding a basic substance to a cerium acetate solution to adjust the pH; (b) adding a basic substance to the metal ion precursor solution to adjust the pH; And (c) dispersing the solutions obtained in steps (a) and (b) in a solvent, followed by solvent heat reaction at a temperature of 90 to 160 ° C. to form metal ion-doped ceria.

In step (a), after preparing a cerium acetate solution as a cerium precursor, a basic substance is added to the solution to adjust the pH to 7 to 11.

In the present invention, by using cerium acetate as the cerium precursor, a metal ion doped ceria with a significantly increased specific surface area can be prepared compared to the case of using other precursors such as cerium nitrate.

In particular, when water is used as a dispersion medium in step (c) to be described later, the effect of increasing the specific surface area of the metal ion doped ceria is maximized by using cerium acetate as a cerium precursor, which is an organic polymer having a long unit of cerium acetate in water. This is because the dispersion is largely caused by the dielectric constant and the chains are blocked between cerium hydroxide, thereby effectively suppressing particle growth and agglomeration of the powder by the steric effect, thereby reducing the overall particle size.

Next, in step (b), after preparing a precursor solution of a metal ion doped with ceria, a basic substance is added to the solution to adjust the pH to 7-11.

The type of the metal ion precursor may be appropriately selected according to the type of metal to be doped into ceria, for example, an acetate-based precursor, an alkoxide-based precursor, or a halogenation containing the metal ion to be doped. It may be a water based (halide based) precursor, an oxyhalide based precursor or a nitrate based precursor.

The metal ion precursor is an acetate-based precursor, an alkoxide-based precursor, a halide-based precursor, an oxyhalide-based precursor containing the metal ion according to the type of metal ion to be doped to ceria ( oxyhalide based precursors or nitrate based precursors.

However, when doping metal ions having an oxidation number of +2 (Ru, Zn, Cu, Ag, Ba, Sr, Sn, etc.), it is possible to synthesize metal ion doping ceria that is superior to catalytic properties than pure ceria. The smaller the ion radius of the metal ion to be doped than the ion radius, the more the lattice shrinkage increases, thereby reducing the particle size and increasing the specific surface area. As a result, catalytic reactivity can be further increased. It is more preferable to use a precursor.

On the other hand, the basic material added for the pH adjustment of each solution in the above steps (a) and (b) is not particularly limited, for example, ammonium hydroxide (NH ₄ OH), potassium hydroxide (KOH), hydroxide Sodium (NaOH) or the like can be used.

Next, in step (c), the pH-adjusted cerium acetate solution obtained in step (a) and the pH-adjusted metal ion precursor solution in step (b) are mixed in and dispersed in a solvent, followed by 90 to 160 Metal ion-doped ceria is synthesized by a solvent heat reaction at a temperature of ℃.

The solvent for dispersing the cerium acetate solution and the metal ion precursor solution prior to the solvent heating process in step (c) may be water or a mixed solvent of water and alcohol, wherein the alcohol is methanol, ethanol, propanol. , A mixture of one or two or more of known alcohols such as butanol and ethylene glycol can be used.

In addition, the content ratio of the cerium acetate solution and the metal ion precursor solution dispersed in the solvent in step (c) can be appropriately adjusted according to the desired metal ion doping amount.

In addition, when the reaction temperature of the solvent heat reaction performed in step (c) is less than 90 ° C., there is a problem that the solvent heat reaction is difficult to occur, and when it exceeds 160 ° C., the solvent heat reaction rate rapidly increases due to excessive heat, resulting in particles. There is a problem that the stability of the.

In addition, if the reaction time of the solvent heat reaction is less than 2 hours, there is a problem in that particle formation is difficult due to insufficient reaction, and when it exceeds 10 hours, the particle size is excessively large and the stability of the particle is also reduced. Can occur.

According to the above-described method for preparing a metal ion doping ceria using a solvent heat synthesis method according to the present invention, a metal ion doping ceria having a high specific surface area and crystallinity is lower than the existing hydrothermal synthesis temperature through a solvent heat synthesis method without a surfactant or additional heat treatment. It can be synthesized economically at a temperature (90 ~ 160 ℃), and in particular, by using cerium acetate as a cerium precursor, it is possible to dramatically improve the specific surface area of metal ion doping ceria, and also doped metal ion Metal ion doped ceria having various particle size and specific surface area and showing higher OSC catalyst characteristics than pure ceria can be synthesized through control of process variables such as, mixture ratio between solvents of mixed solvent, pH, reaction time, etc.

Hereinafter, the present invention will be described in more detail with reference to Examples.

The embodiments according to the present specification may be modified in various other forms, and the scope of the present specification is not interpreted to be limited to the embodiments described below. The embodiments of the present specification are provided to more fully describe the present specification to those skilled in the art.

<Example>

In this example, ceria nanopowders doped with ruthenium (Ru) ions were synthesized according to the process flow chart shown in FIG. 2.

Cerium (III) acetate hy-drate [Ce (CH ₃ CO ₂ ) ₃ · xH ₂ O] as cerium precursor, and Ruthenium (III) chloride [RuCl ₃ · nH ₂ O] as ruthenium ion precursor. Secondary distilled water was used as the water.

First, an aqueous solution of cerium precursor and an aqueous solution of ruthenium ion precursor were prepared, and then the pH of each solution was adjusted to 11 using NH ₄ OH. Subsequently, the aqueous solution of the cerium precursor and the solution of the ruthenium ion precursor are redispersed in a solvent (water) so that the molar ratio of Ce and Ru is 95: 5, 90:10, 85:15, 80:20 or 75:25 and stirred, followed by Teflon. It was placed in a container and subjected to a solvent heat reaction at 120 ° C. for 2 hours. Thereafter, washing was performed 5 times using water and ethanol, and drying was performed in a dryer for 24 hours to collect ceria nano powders doped with ruthenium ions.

Zn, Cu or Ag doped ceria is a metal ion precursor, respectively, Zinc nitrate hexahydrate [Zn (NO ₃ ) ₂ · 6H ₂ O], Copper nitrate [Cu (NO ₃ ) ₂ ] or Silver nitrate hexahydrate [Ag (NO ₃ ) ₂ · 6H ₂ O] was prepared according to the same synthesis method as above.

3 is a synthesized ruthenium doping ceria (Ru-doped CeO ₂ ) synthesized under the conditions of 95: 5, 90:10, 85:15, 80:20, 75:25 in the molar ratio of Ru to Ce as described above. It is the result of X-ray diffraction analysis (XRD) for the nano powder. When the observed XRD phase was compared with ICSD 98-005-3995, the same peak appeared at all positions, and thus it was confirmed that ceria of a fluorite structure without a secondary phase was synthesized.

Table 1 below (specific surface area and catalytic characterization results of Ru-doped CeO ₂ nanopowder) shows the particle size, specific surface area and H ₂ -TPR catalytic characterization results calculated using the Scherrer formula. The average particle size of the prepared ruthenium-doped ceria (Ru-doped CeO ₂ ) was less than 9 nm, which was confirmed to be smaller than that of pure ceria. The ionic radii of Ce ⁴⁺ and Ce ³⁺ are 111 and 128.3 Å at the 8th coordinate, respectively, and Ru ⁴⁺ and Ru ³⁺ are 76 Å and 82 에 at the 6th coordinate. Considering the ion radius, it seems that the relatively small size of Ru ions is substituted in the ceria lattice, resulting in lattice shrinkage, resulting in a smaller particle size as the amount of Ru doping increases.

As the doping amount of ceria increased to 20 mol%, the specific surface area increased from 135.56 m ² / g to 209.73 m ² / g, but the particle size increased to 8.76 nm when compared to 20 mol% at 25 mol%. The specific surface area was reduced to 157.72 m ² / g. Nevertheless, it was confirmed that the specific surface area was much higher than that of the existing pure ceria (90-100 m ² / g).

In addition, it was confirmed that the catalytic properties of ruthenium doped ceria (Ru-doped CeO ₂ ) having a Ru doping amount of 15 mol% or less is 2-3 times higher than the catalytic properties of H pure ceria (H ₂ consumption: 243.27 umol / g).

4 to 8 are FE-TEM measurement results of ruthenium doped ceria (Ru-doped CeO ₂ ), it was confirmed that the occurrence of the rod (rod) increases as the Ru content increases. The EDS measurement showed that the rod phase was a pure ceria phase.

Table 2 (Metal (Ru, Zn, Cu or Ag) ion doped ceria nano powder and pure ceria nano powder specific surface area and catalytic properties analysis results) metal (Ru, Zn, Cu or Ag) ion is 15 mol% doped The calculated particle size, specific surface area, and H ₂ -TPR catalyst characterization results for ceria nano powder and pure ceria nano powder are shown. According to this, although the difference in specific surface area and catalytic properties is large between metal ion doped ceria according to the type of doped metal ions, it was confirmed that all metal ion doped ceria have higher specific surface area and catalytic properties than pure ceria.

According to the method of manufacturing a metal ion doping ceria using a solvent heat synthesis method according to the present invention, a metal ion doping ceria having a high specific surface area and crystallinity and exhibiting OSC catalyst characteristics higher than that of pure ceria is lower than the existing hydrothermal synthesis temperature (90 ~ 160 ° C).

Claims (8)

1. (A) adding a basic material to the cerium acetate solution to adjust the pH;

   (b) adding a basic substance to the metal ion precursor solution to adjust the pH; And

   (c) dispersing the solutions obtained in steps (a) and (b) in a solvent, followed by solvent heat reaction at a temperature of 90 to 160 ° C. to form metal ion-doped ceria;

   Method for producing a metal ion doped ceria using a solvent heat synthesis method comprising a.
2. According to claim 1,

   The metal ion precursor in the step (b),

   Solvent heat synthesis method characterized by being an acetate-based precursor, an alkoxide-based precursor, a halide-based precursor, an oxyhalide-based precursor, or a nitrate-based precursor Method of manufacturing a metal ion doped ceria using.
3. According to claim 1,

   The solvent is a method of producing a metal ion doped ceria using a solvent heat synthesis method, characterized in that a mixed solvent of water or water and alcohol.
4. According to claim 3,

   The mixed solvent is 75% by volume or less of ethanol (EtOH) method of manufacturing a metal ion doped ceria using a solvent heat synthesis method, characterized in that.
5. According to claim 1,

   The basic material is ammonium hydroxide (NH ₄ OH), sodium hydroxide (NaOH) or potassium hydroxide (KOH), characterized in that the metal ion doping ceria production method using a solvent heat synthesis method.
6. According to claim 1,

   The method of producing a metal ion doped ceria using a solvothermal synthesis method, characterized in that the solvothermal reaction is performed for 2 to 10 hours.
7. A metal ion-doped ceria produced by the method according to claim 1.
8. A catalyst for purification of exhaust gas comprising the metal ion doping ceria of claim 7 as an oxygen storage capacity (OSC) material.

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