JP4265541B2 - Method for producing nanoparticles - Google Patents

Description

  The present invention relates to nano particles used for automobile exhaust purification, fuel cell, and environmental purification, and more particularly, to nanometer order catalyst particles.

  For example, noble metals such as Pt, Pd, and Rh are used as catalysts for purifying harmful components such as HC, CO, and NOx contained in automobile exhaust gas. In order to increase the contact area with the exhaust gas, these noble metals for catalyst are supported as particles on the surface of a carrier such as alumina to purify harmful components.

  In recent years, exhaust gas regulations for automobiles and the like are becoming stricter, and it is desired for exhaust gas purification catalysts to purify harmful components with higher efficiency.

  Similarly, it is necessary to further improve the purification performance and function of a catalyst for a fuel cell (for example, a catalyst such as a reaction between hydrogen and oxygen or a methanol reforming catalyst) or a catalyst for environmental purification. Development of catalysts is expected.

  As one of the measures for improving the efficiency of the noble metal catalyst, it is conceivable to make the noble metal particles fine and increase the contact area with harmful components.

  However, in the conventional loading method, only noble metal particles of submicron order (several hundreds nm) can be obtained, which hinders further improvement of the specific surface area of the catalyst. For this reason, nanometer order ( The appearance of a noble metal fine particle catalyst of nano order (about 100 nm or less) is desired.

  Therefore, in the background as described above, the development of nano-order noble metal particles having a large contact area is progressing with the aim of further increasing the activation.

For example, a method of supporting nano-order metal fine particles on γAl ₂ O ₃ using a sputtering method has been proposed (see, for example, Patent Document 1). Further, a method has been proposed in which fine particles of 20 nm or less are supported on a carrier such as Al ₂ O ₃ by using an electron beam simultaneous irradiation method (see, for example, Patent Document 2).

  However, in each of the above patent documents, nano-order noble metal fine particles can be supported on a carrier, but the configuration (shape, specificity, etc.) of the surface of the noble metal fine particles is not particularly limited.

  In addition, for example, the presence of a cocatalyst is indispensable for simultaneously purifying a plurality of harmful substances such as HC, CO, and NOx. .

  From the above, it can be said that the catalyst design at the thin film level or the atomic level is necessary to develop a nanocomposite catalyst with higher activity. In response to such a demand, a catalyst particle having higher activity and capable of exhibiting activity against a plurality of types of substances has been proposed (see Patent Document 3).

This includes a single particle having a primary particle size of nanometer order or two or more solid solution fine particles, and one or more metals or their derivatives covering at least a part of the surface of the basic particle. The catalyst particles and the method for producing the same are provided.
Special table 2000-510042 gazette JP 2000-15098 A Japanese Patent Laid-Open No. 2003-80077

  However, the method for producing catalyst particles described in the above-mentioned Patent Document 3 is a method in the gas phase in which the structure is easily controlled, and is not necessarily a satisfactory method when mass production is considered. Therefore, there is an urgent need to develop a production method in a liquid phase that is excellent in mass productivity.

  However, in the liquid phase, the primary particles of nano-order aggregate due to intermolecular force, ζ (zeta) potential, etc., and form secondary particles. Therefore, it is necessary to monodisperse as primary particles.

  The present invention has been made in view of the above problems, and is a kind of single-particulate fine particles or two or more kinds of solid solution or composite particles having a primary particle size of nanometer order, that is, nano-particles. It aims at providing the manufacturing method of the nanoparticle which can be disperse | distributed appropriately in it.

To achieve the above object, the invention described in claim 1, the a kind of single particles or two or more kinds of solid solutions or composite particles aggregates of fine particles having a primary particle size of 1 nm~100 nm, liquid phase The liquid is injected into the liquid phase by ultrasonic waves, pressure or agitation to generate bubbles in the liquid phase, and the agglomerates are crushed using the jet stream to obtain individual fine particles ( was dispersed in 1),
The dispersed fine particles (1) are present in the liquid phase together with the metal precursor, and the jet stream is generated again in the liquid phase, and the metal precursor is reduced and dispersed using the jet stream. on the surface of the individual particles (1), the metal precursor is characterized Rukoto precipitating metal coating layer made of the fine metal particles or a few atomic layers of 1nm~100nm a metal was reduced (2).

According to this, since the aggregates of nano-particles are crushed using a jet flow in the liquid phase, the nanoparticles can be dispersed as individual particles (1). Further, the surface of the nano fine particles (1) is provided with a metal coating layer (2) having a catalytic function, and for example, nano fine particles functioning as catalyst fine particles can be produced.

Further, as in the invention according to claim 2 , in the method for producing nano-particles according to claim 1 , the liquid temperature of the liquid phase is preferably 20 ° C. or more and 60 ° C. or less.

It is preferable as defined in claim 3, in the method of manufacturing nanoparticles according to claim 1 to claim 2, wherein as the fine particles (1), Ce, Zr, Al, Ti, Si, Mg , W, Fe, Sr and Y can be used alone, or a metal oxide composed of two or more solid solutions or composites can be used.

Here, as in the invention according to claim 4 , in the method for producing nano-particles according to claims 1 to 3 , the metal precursor includes a metal oxide, a metal chloride, and a metal ammonium salt. , Selected from metal nitrates and derivatives thereof.

It is preferable as defined in claim 5, in the method of manufacturing nanoparticles according to claims 1 to 4, wherein the metal coating layer (2) is consisted of a transition metal, Pt , Pd, Rh, Ir, Ru, Au, Ag, Re, Os, Co, Ni, Fe, Cu, Mn, Cr, V, Mo, W, or one or more solid solutions. Can be a thing.

Furthermore, in the invention according to claim 6, in the manufacturing method of the nanoparticles according to claims 1 to 5, wherein the dispersed with individual particles (1) and the metal precursor, the liquid phase reducing agent And the reduction of the metal precursor is performed using the reducing agent.

  In order to reduce the metal precursor, it is preferable to add a reducing agent in this way and perform the reduction using this reducing agent.

Here, as in the invention according to claim 7 , in the method for producing nano-particles according to claim 6 , the reducing agent is selected from alcohols, amines, saccharides and surfactants. Can be used.

Further, as in the invention according to claim 8 , in the method for producing nano-particles according to claim 6 or 7 , the ratio of the reducing agent is 0.01 wt% or more in the liquid phase. It is preferable.

  In addition, the code | symbol in the bracket | parenthesis of each said means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram schematically showing nano-particles as catalyst particles according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes nano-particles, and the nano-particles 1 are one kind of simple particles having a primary particle diameter of nanometer order (hereinafter referred to as nano-order), or two or more kinds of solid solution or composite particles.

  Here, the primary particle diameter of the nano fine particles 1 is the diameter of one nano fine particle 1, and the primary particle diameter being nano-order usually means that the primary particle diameter is 100 nm or less. In this example, the primary particle diameter of the nano fine particles 1 is about 1 nm to 50 nm.

  In addition, as the nanoparticle 1, a kind of simple particle is a kind of fine particle made of an element or compound such as a ceramic or metal, and two or more kinds of solid solution fine particles are two or more kinds of ceramic or metal. A fine particle in which an element or a compound is in a solid solution. The composite fine particles are fine particles in which two or more kinds of elements or compounds such as ceramics and metals are mixed.

  Such nanoparticle 1 can be made of a metal oxide, specifically, one kind of simple substance selected from Ce, Zr, Al, Ti, Si, Mg, W, Fe, Sr, Y, or Two or more solid solutions or composites can be employed.

  The method for producing the nano fine particles 1 that are such nano-order fine particles is not particularly limited, but includes a coprecipitation method, a sol-gel method, a hydrothermal synthesis method, a plating method, an atmospheric pressure plasma method, a vacuum evaporation method, and the like. Can be given.

  In addition, the properties and composition ratios of the two or more solid solutions are not particularly limited, and the properties and composition ratios of the two or more solid solutions are set in order to improve the purification performance such as temperature characteristics and durability characteristics. What is necessary is just to adjust suitably.

  In the present embodiment, at least a part of the surface of the nanoparticle 1 is coated with a metal coating layer 2 made of one or more metals. Here, the one or more metals may be precious metals having a catalytic function.

  The metal coating layer 2 is attached to the surface of the nanoparticle 1 as nanoparticle metal particles, for example, ultrafine particles having a particle diameter of less than 50 nm, or is formed on the surface of the nanoparticle 1 as a coating layer consisting of several atomic layers. It is attached.

  Thus, when the metal coating layer 2 composed of ultrafine particles or several atomic layers is formed on the nano-order nano-particles 1, highly active catalyst particles can be realized. This reason is described in Patent Document 3 (Japanese Patent Laid-Open No. 2003-80077) described above.

  And such a metal coating layer 2 consists of a metal which reduced the metal precursor by the method mentioned later.

  This metal precursor is a precursor for precipitating the metal coating layer 2 on the surface of the nanoparticle 1 and was selected from metal oxide, metal chloride, metal ammonium salt, metal nitrate and derivatives thereof. Is.

  If these compounds are used, the structure is not particularly limited. When Pt is used as an example, platinum acid is used as the metal oxide, platinum chloride is used as the metal chloride, tetraamminedichloroplatinum is used as the metal ammonium salt, Examples of the metal nitrate include dinitrodiamine platinum.

  The metal coating layer 2 deposited on the nanoparticle 1 by reducing such a metal precursor is made of a transition metal, specifically, Pt, Pd, Rh, Ir, Ru, Au, Ag, Re, , Os, Co, Ni, Fe, Cu, Mn, Cr, V, Mo, and W. One or more simple substances or two or more solid solutions.

  In the present embodiment, the nanoparticles 1 can also have catalytic activity, and the nanoparticles 1 and the metal coating layer 2 are selected so as to exhibit catalytic activity against different substances. Therefore, one type of catalyst particle can exhibit activity against a plurality of types of substances.

  Although this detailed mechanism is not well understood, in practice, the catalytic function can be synergistically improved, and catalyst particles having high decomposition activity can be realized for a plurality of toxic substances.

Specifically, the combination of the nano fine particles 1 coated with the metal coating layer 2 that can be expected to have a synergistic effect on the catalyst function includes CeO ₂ fine particles coated with Pt and CeO ₂ —ZrO ₂ coated with Pt. Examples thereof include solid solution fine particles, TiO ₂ fine particles coated with Au, and carbon particles coated with Pt.

  Thus, according to the present embodiment, it is possible to provide catalyst fine particles that have higher activity and can exhibit activity against a plurality of types of substances.

  Next, the manufacturing method of the nanoparticle 1 of this embodiment is demonstrated.

  The manufacturing method of the nano fine particles 1 in this embodiment is a kind of single fine particles or two or more kinds of solid solution or composite particles, and aggregates of the nano fine particles 1 having a primary particle size on the order of nanometers in the liquid phase. A jet stream is generated in the liquid phase, and aggregates are crushed using this jet stream and dispersed into individual fine particles.

  Here, the aggregate of the nano fine particles 1 can be obtained as a commercial product. As described above, since the nanoparticle 1 is more energetically stable when aggregated by intermolecular force, ζ (zeta) potential, or the like, the aggregate of the nanoparticle 1 is easily available.

  Moreover, water, an organic solvent, etc. can be used as a liquid phase. And the said aggregate is thrown into such a solvent, a jet flow is made, and the said aggregate is disintegrated. Although the details of this mechanism are unknown, it is considered that the aggregates are crushed by the impact when the high-temperature and high-pressure cavities (bubbles) generated by the jet flow disappear.

  And according to this manufacturing method, since the aggregate of the nanoparticle 1 is crushed using a jet flow in a liquid phase, the nanoparticle 1 can be dispersed as individual particles. That is, according to this embodiment, it is possible to provide a method for producing nano-particles in which the nanoparticles 1 can be appropriately dispersed in the liquid phase.

  Here, in the method for producing nanoparticles according to the present embodiment, the jet flow can be generated by an explosion of cavitation generated in the liquid phase or a physical internal shear force generated in the liquid phase. More specifically, ultrasonic waves, pressure, agitation, or the like can be employed as a jet flow generation source.

  Moreover, in the manufacturing method of the nanoparticle of this embodiment, it is preferable to set it as 20 to 60 degreeC as liquid temperature of a liquid phase. When the temperature is low, the viscosity of the liquid phase increases and it becomes difficult to disintegrate. On the other hand, when the temperature is high, problems such as a problem on the apparatus side and that the fine particles themselves easily aggregate occur. is there.

  Further, as shown in FIG. 1, in order to form catalyst fine particles in which the metal coating layer 2 is deposited on the surface of the nano fine particles 1, the individual nano fine particles 1 dispersed by the above production method are combined with the metal precursor. The metal which is present in the liquid phase, generates a jet flow again in the liquid phase, reduces the metal precursor using this jet flow, and the metal precursor is reduced on the surface of the dispersed fine particles. Then, the metal coating layer 2 composed of metal fine particles of nanometer order or several atomic layers is deposited.

  According to this, the surface of the nanoparticle 1 is provided with the metal coating layer 2 having a catalytic function and the like, and the nanoparticle 1 functioning as the catalyst particle as shown in FIG. 1 can be manufactured.

  Here, the jet flow for reducing the metal precursor can also be generated by an explosion of cavitation generated in the liquid phase or a physical internal shear force generated in the liquid phase. More specifically, as the generation source of the jet flow, ultrasonic waves, pressure, stirring, or the like can be employed as described above.

  Here, in the method for producing nano-particles of the present embodiment, a reducing agent is present in the liquid phase together with the dispersed individual fine particles and the metal precursor, and the reduction of the metal precursor is performed using the reducing agent. You may make it perform.

  In order to reduce the metal precursor, it is preferable to add a reducing agent in this way and perform the reduction using this reducing agent. Such a reducing agent is not particularly limited, and examples thereof include alcohols, amines, saccharides, and surfactants.

  Specifically, the alcohols include ethanol, propanol, the amines include diethanolamine, the saccharides include sucrose, and the surfactant includes an alkaline surfactant.

  Further, the amount of such a reducing agent added is not particularly limited, and may be 0.01 wt% (wt%) or more with respect to the solvent, that is, 0.01 wt% or more in the liquid phase. It ’s fine.

  However, by controlling the ratio of the reducing agent, it is possible to control the metal particle size that is reduced and deposited, and it is desirable to select the ratio of the reducing agent to the desired metal particle size.

  When the ratio of the reducing agent is large, the reaction becomes faster, so that the growth of the metal particles is promoted and the metal particle size is increased. On the other hand, when the ratio of the reducing agent is small, the growth of the metal particles is slow and the precipitation to other active sites is promoted more than the growth, so that the metal particle size tends to be small.

  Although the details of the mechanism of formation of the metal coating layer 2 by such a jet flow are unknown, it is considered that the metal precursor is reduced and precipitated by the following presumed mechanism.

For example, an example using CeO ₂ as a nanoparticle and PtCl ₂ as a metal precursor will be described. When a nanoparticle and a metal precursor are mixed in a solvent, CeO ₂ and Pt ²⁺ ions Cl ⁻ ions are dissolved in the solvent. It is in a dispersed state.

Then, the reducing agent contained in the solvent reduces and atomizes (metalizes) Pt ²⁺ ions using the active sites on the CeO ₂ surface as nuclei, thereby depositing Pt metal as a metal coating layer on the CeO ₂ surface. To do. Further, Pt atomized by the impact of the jet stream is driven into the CeO ₂ surface.

Then, precipitation of Pt metal proceeds. At this time, a cavity is generated on the CeO ₂ surface by the jet flow. Due to the presence of the cavity, Pt metal is dispersed and precipitated on the CeO ₂ surface, and the crystal growth of the Pt metal is suppressed by the impact of the disappearance of the cavity.

It is considered that Pt metal is deposited on the CeO ₂ surface by the atomization by the reducing agent and the jetting effect by the jet flow, and thus a metal coating layer is formed on the surface of the nano fine particles.

  Thus, according to this embodiment, an aggregate of nano fine particles 1 having a single particle size or two or more solid solution or composite particles and having a primary particle size on the order of nanometers is put into the liquid phase. In addition, it is possible to provide a method for producing nano-particulates, characterized in that a jet stream is generated in the liquid phase, aggregates are crushed using the jet stream, and dispersed into individual micro-particles.

  And according to this manufacturing method, since the aggregate of the nanoparticle 1 is disintegrated in the liquid phase using a jet stream, the nanoparticle 1 can be appropriately dispersed in the liquid phase. A method can be provided.

  Further, in the manufacturing method of the present embodiment, as described above, as a generation source of the jet flow, an explosion of cavitation generated in the liquid phase, or a physical internal shear force generated in the liquid phase, specifically In other words, it is one of the characteristics to employ ultrasonic waves, pressure, or stirring.

  Moreover, in the manufacturing method of this embodiment, as mentioned above, it is also one of the characteristics that the liquid temperature of the liquid phase is 20 ° C. or more and 60 ° C. or less. Furthermore, the nanoparticle 1 includes a metal oxide composed of a single element selected from Ce, Zr, Al, Ti, Si, Mg, W, Fe, Sr, and Y, or two or more solid solutions or composites. It is one of the features to use.

  Further, according to the present embodiment, the aggregates of the nano fine particles 1 are charged into the liquid phase, a jet flow is generated in the liquid phase, and the aggregates are crushed using the jet flow to obtain individual fine particles. Next, the dispersed individual nanoparticles 1 are made to exist together with the metal precursor in the liquid phase, a jet flow is generated again in the liquid phase, and the metal precursor is reduced using this jet flow. Then, on the surface of each dispersed fine particle, a metal fine particle having a reduced metal precursor and having a nanometer-order metal fine particle or a metal coating layer 2 consisting of several atomic layers is deposited. A method is provided.

  According to this, the nanoparticles 1 can be appropriately dispersed in the liquid phase, and the nanoparticles 1 having the metal coating layer 2 having a catalytic function or the like on the surface thereof can be produced.

  Here, in the manufacturing method of the present embodiment, one of the features is that a metal precursor selected from metal oxides, metal chlorides, metal ammonium salts, metal nitrates, and derivatives thereof is employed. As described above.

  Further, as described above, in the manufacturing method of the present embodiment, the metal coating layer 2 is made of a transition metal, and Pt, Pd, Rh, Ir, Ru, Au, Ag, Re, Os, Co, It is also one of the characteristics that it is one or more simple substances selected from Ni, Fe, Cu, Mn, Cr, V, Mo, and W, or two or more solid solutions.

  Furthermore, in the production method of the present embodiment, the reduction of the metal precursor using a reducing agent, the use of a reducing agent selected from alcohols, amines, sugars and surfactants, the reducing agent It is also one of the features that the ratio of is 0.01 wt% or more in the liquid phase.

  Examples of nanoparticles that can be used as a catalyst will be described below together with a comparative example. These nanoparticles are applicable to a wide variety of fields such as exhaust gas purification, environmental purification, and fuel cells. Needless to say, the present invention is not limited to the examples.

Agglomerates of CeO ₂ fine particles having a primary particle diameter of several nanometers as nano-fine particles were mixed in water and pulverized by generating a jet stream by stirring using a high-speed rotating mixer. The stirring time by jet flow was 30 minutes, and the water temperature was 20 ° C.

Aggregates of CeO ₂ .ZrO ₂ solid solution fine particles having a primary particle diameter of several nanometers as nanoparticles were mixed in water and pulverized by generating a jet stream by stirring using a high-speed rotating mixer. The stirring time by jet flow was 30 minutes, and the water temperature was 20 ° C.

Aggregates of CeO ₂ .ZrO ₂ solid solution fine particles having a primary particle size of several nanometers as nano-fine particles were mixed in water, and pulverized by generating a jet stream by ultrasonic waves using an ultrasonic irradiation device. The stirring time by jet flow was 30 minutes, and the water temperature was 20 ° C.

Agglomerates of CeO ₂ · ZrO ₂ solid solution fine particles with a primary particle size of several nanometers as nanoparticles are mixed in water, and this mixed solution is compressed and then passed through a slit to generate a jet flow by pressure. And crushed.

Aggregates of CeO ₂ / ZrO ₂ solid solution fine particles with a primary particle size of several nanometers partially coated with Pt as nano fine particles are mixed in water, and jet flow is generated by ultrasonic waves using an ultrasonic irradiation device. And crushed. The stirring time by jet flow was 30 minutes, and the water temperature was 20 ° C.

(Comparative Example 1)
An aggregate of CeO ₂ .ZrO ₂ solid solution fine particles having a primary particle diameter of several nanometers as nanoparticles was mixed in water and crushed by a ball mill using ZrO ₂ balls.

PtCl ₂ as a metal precursor is mixed in water in an aqueous solution containing CeO ₂ · ZrO ₂ solid solution fine particles having a primary particle size of several nanometers crushed in Example 2 above, and uniformly using a rotor or the like. Dispersed.

Next, ethanol is mixed as a reducing agent, a jet flow is generated by stirring using a high-speed rotating mixer to reduce the metal precursor, and a metal coating layer made of Pt is formed on the CeO ₂ · ZrO ₂ solid solution fine particles. Precipitated. Here, the stirring time by the jet flow was 30 minutes, and the water temperature was 20 ° C.

PtCl ₂ and RhCl ₃ .3H ₂ O as a metal precursor were mixed in water in an aqueous solution containing CeO ₂ .ZrO ₂ solid solution fine particles having a primary particle diameter of several nanometers crushed in Example 2 above, and the rotor Etc. to uniformly disperse.

Next, ethanol is mixed as a reducing agent, a jet flow is generated by stirring using a high-speed rotating mixer, the metal precursor is reduced, and a metal coating layer composed of Pt and Rh on CeO ₂ · ZrO ₂ solid solution fine particles Was precipitated. The stirring time by jet flow was 30 minutes, and the water temperature was 20 ° C.

PtCl ₂ and RhCl ₃ .3H ₂ O as a metal precursor were mixed in water in an aqueous solution containing CeO ₂ .ZrO ₂ solid solution fine particles having a primary particle diameter of several nanometers crushed in Example 2 above, and the rotor Etc. to uniformly disperse.

Next, in this example, ethanolamine is mixed as a reducing agent, a jet flow is generated by stirring using a high-speed rotary mixer, the metal precursor is reduced, and Pt and Rh are formed on CeO ₂ · ZrO ₂ solid solution fine particles. A metal coating layer was deposited. The stirring time by jet flow was 30 minutes, and the water temperature was 20 ° C.

(Comparative Example 2)
Other using an aqueous solution containing CeO ₂ · ZrO ₂ solid solution particles of the primary particles size of several nm that is disintegrated in Comparative Example 1, in the same manner as in Example 6, CeO ₂ · ZrO ₂ on solid solution particles The metal coating layer which consists of Pt was deposited on this.

(Observation of monodisperse state)
In order to confirm the particle diameters and the like of the fine particles produced in Examples 1 to 5 and Comparative Example 1, particle size distribution measurement by a light scattering method and TEM observation were performed.

  In Comparative Example 1, although the average particle diameter is 140 nm and it can be slightly crushed by ball milling, since the ball mill particles themselves are large, crushing to the nano-order is very difficult.

  In contrast, when the nanoparticle aggregates were crushed using the jet flow according to Examples 1 to 5, the average particle size of the pulverized nanoparticles was 3.8 nm, and the primary particle size was reduced to the primary particle size. It was confirmed that it was monodispersed.

(Evaluation of purification performance of toxic substances)
In order to confirm that the above examples show high activity against harmful gases, the purification performance was evaluated using the catalyst fine particles produced in the above Examples 6 to 8 and Comparative Example 2.

  After removing water from the aqueous solutions containing the fine particles of Examples 6 to 8 and Comparative Example 2 and drying, pellets having a diameter of 10 mm and a thickness of 6 mm made of the fine particles were produced. Thereafter, this pellet was pulverized to φ0.85 mm to 1.7 mm using a sieve, and 5 cc of the pulverized granule was set in a quartz glass tube.

  Under conditions of 50 ° C. to 400 ° C. in an infrared image furnace, propylene gas is allowed to flow from the inlet side of the glass tube, and the gas amount and gas components coming out from the outlet side of the glass tube are analyzed by gas chromatography. The temperature at which propylene gas was purified by 50% (purification temperature) was measured. This is called the initial purification temperature.

  Further, in order to evaluate the stability of the catalyst fine particles at a high temperature, the same measurement was carried out after leaving in a furnace at 1000 ° C. for 24 hours. The purification temperature obtained by this measurement will be referred to as the purification temperature after aging. The lower the purification temperature, the better the purification performance.

  The results of measuring the purification temperature for each of Examples 6 to 8 and Comparative Example 2 were as follows.

  In Example 6, the initial purification temperature was 165 ° C., and the purification temperature after aging was 199 ° C.

  In Example 7, the initial purification temperature was 157 ° C., and the purification temperature after aging was 188 ° C.

  In Example 8, the initial purification temperature was 158 ° C., and the purification temperature after aging was 190 ° C.

  In Comparative Example 2, the initial purification temperature was 176 ° C., and the purification temperature after aging was 208 ° C.

  Compared to Comparative Example 2, in Examples 6 to 8, the purification temperature after the initial stage and after aging was low, and it was confirmed that the purification performance was improved by crushing and reduction by jet flow. This is presumably because high dispersion in reduction of the metal precursor was made possible by monodispersion in an aqueous solution.

  In addition, as is clear from the evaluation results of the examples and comparative examples, when purification at the same temperature is considered, it can be said that the catalyst according to this example functions in a small amount compared to the existing one, which reduces the cost. Can also be expected to contribute.

  As described above, the present invention provides a method for monodispersing nanoparticle having a primary particle size of nano-order in a liquid phase and a method for forming a nanocomposite particle by forming a metal coating layer on the nanoparticle. It is.

  Specifically, it is characterized in that a fine particle aggregate having a primary particle size of nano-order is pulverized and monodispersed using a jet flow. In addition, in the case of jet flow, when it is desired to form a metal coating layer on fine particles having a primary particle size of nano-order as well as monodisperse, it is also possible to form a metal coating layer by combining with a reducing agent. .

It is a figure which shows typically the nanoparticle as a catalyst particle concerning embodiment of this invention.

Explanation of symbols

  1 ... nano fine particles, 2 ... metal coating layer.

Claims (8)

A kind of single particles or two or more of a solid solution or a composite particle aggregates of fine particles having a primary particle size of 1 nm~100 nm, was introduced in the liquid phase,
A jet stream is generated in the liquid phase by ultrasonic waves, pressure, or stirring to generate bubbles in the liquid phase, and the aggregate is crushed using the jet stream to form individual fine particles (1). Disperse ,
The dispersed individual fine particles (1) are present together with a metal precursor in the liquid phase, and again, the jet stream is generated in the liquid phase,
The metal precursor is reduced using this jet stream, and the metal particles reduced from the metal precursor and having a thickness of 1 nm to 100 nm or several atomic layers are formed on the surface of the dispersed fine particles (1). method for producing nanoparticles, wherein Rukoto precipitate metallized layer (2) made. The method for producing nanoparticles according to claim 1 , wherein the liquid temperature of the liquid phase is 20 ° C. or more and 60 ° C. or less. The fine particles (1) are a single oxide selected from Ce, Zr, Al, Ti, Si, Mg, W, Fe, Sr, and Y, or a metal oxide composed of two or more solid solutions or composites. The method for producing nano-particles according to claim 1 or 2 . The metal precursor, metal oxides, metal chlorides, nano according to any one of claims 1 to 3, characterized in that selected from metal salts, metal nitrates and their derivatives A method for producing fine particles. The metal coating layer (2) is made of a transition metal, and is made of Pt, Pd, Rh, Ir, Ru, Au, Ag, Re, Os, Co, Ni, Fe, Cu, Mn, Cr, V, The method for producing nanoparticles according to any one of claims 1 to 4, wherein the method is one or more simple substances selected from Mo and W, or two or more solid solutions. Claim 1, with individual particles (1) and the metal precursor described above dispersion, the reducing agent is present in the liquid phase, the reduction of the metal precursor, and carrying out using the reducing agent The manufacturing method of the nanoparticle as described in any one of thru | or 5 . The method for producing nanoparticles according to claim 6 , wherein the reducing agent is selected from alcohols, amines, sugars and surfactants. The method for producing nanoparticles according to claim 6 or 7 , wherein a ratio of the reducing agent is 0.01 wt% or more in the liquid phase.

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