JP2012158500A - Composite having cerium oxide nanoparticle dispersed into zeolite, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite having fine particle sizes in such a nano level that the particle sizes are 1-20 nm, in which nanoparticles of cerium oxide CeOwhose particle sizes are uniform exist in a dispersed form in zeolite.SOLUTION: A "Linde Q" type zeolite having a composition of KO-AlO-2SiO-xHO and hexagonal plate-like crystal form is dipped into aqueous solution of a soluble salt of Ce, and ion exchange of Kor Naand Ceion in the zeolite is performed at a temperature of ≤100°C, to thereby allow Ce ion to exist in the zeolite with at least 10% exchange rate. The ion exchanger is fired at a temperature of ≥200°C under an oxidative atmosphere to oxidize cerium (III) into cerium (IV), and thereby this composite in which cerium oxide nanoparticles are dispersed into zeolite is obtained. Further, the cerium oxide nanoparticles can be obtained as a single substance by dissolving and removing the zeolite.

Description

The present invention relates to a cerium oxide nanoparticle-zeolite composite in which cerium oxide nanoparticles are dispersed in a zeolite crystal structure, and a method for producing the same. Of particular importance as this composite is a cerium oxide nanoparticle-plate-like zeolite composite obtained by using a zeolite having a plate-like crystal form.

The present invention also relates to a nanoparticle in which metal oxide solid solution cerium oxide in which a metal oxide other than cerium coexists in cerium oxide as a solid solution is present in the form of nanoparticles dispersed in a zeolite crystal structure. The present invention also relates to a zeolite composite and a method for producing the same.

The present invention further provides an oxide having a fine and uniform particle size distribution at a nanometer level obtained separately from the cerium oxide nanoparticle-plate-like zeolite composite or the metal oxide solid solution cerium oxide nanoparticle-plate-like zeolite composite. The present invention relates to a cerium nanoparticle or a metal oxide solid solution cerium oxide nanoparticle itself and a production method thereof.

Nanoparticulation technology has been developed for the purpose of improving the properties of cerium oxide, especially the catalytic properties. A conventional method for producing cerium oxide has been carried out by adding chlorine and sodium hydroxide to an aqueous solution of cerium salt to form a precipitate of cerium hydroxide, which is calcined and pulverized. It was not possible to control the morphology and particle size of One of the methods proposed as a nanoparticulate technique is a method of producing a cerium oxide precursor in the presence of an organic solvent and producing cerium oxide nanoparticles having a particle size of about 30 to 300 nm by a hydrothermal reaction (Patent Literature). 1). Since cerium oxide obtained by this technique has a wide particle size distribution, it is not possible to obtain cerium oxide having a uniform particle size. Another technique is a method for producing cerium oxide nanoparticles having an average particle diameter of 100 nm or less by a synthesis reaction in an organic solvent (Patent Document 2). This technique also has a wide cerium oxide particle size distribution and is uniform. It is not possible to provide a product with a small particle size.

As a method for producing fine particles having a particle size within a range of 1 to 200 nm from metal oxides, not limited to cerium oxide, a technique including mechanical pulverization treatment in the process has been developed (Patent Document 3). However, mechanical treatment does not give a metal oxide powder with a uniform particle size even in principle. As a technique different from this, it has been devised to produce a metal oxide solid solution by continuously reacting a reaction mixture under pressure (Patent Document 4). In addition to requiring a high-pressure device, there is a disadvantage that workability is poor due to high-pressure processing.

As a technique capable of producing cerium oxide nanocrystals having a uniform particle size, an anhydrous and hydrous sol-gel reaction method has been proposed (Patent Document 5). However, this method uses an organic solvent and is complicated in operation. As a method for synthesizing metal oxide nanoparticles having a narrow particle size distribution, a method of irradiating a solution containing a metal salt or metal complex with an ultraviolet region wavelength laser has also been proposed (Patent Document 6). This also requires special equipment for synthesis.

On the other hand, since zeolite can easily disperse various metal elements uniformly in its cavity (pore) by ion exchange, an ion exchanger using zeolite as a mother crystal or raw material is a phosphor. It has been prototyped in various fields including manufacturing. The one obtained by exchanging zeolite with cerium ions is particularly useful as a catalyst. For example, there is a proposal to use β-type zeolite ion exchanged with cerium ions as an exhaust gas purifying catalyst (Patent Document 7). . However, this is not a technique for synthesizing cerium oxide. As for the exhaust gas purifying catalyst, there is a technology for producing a catalyst containing a compound supported on cerium oxide while performing ion exchange of zeolite with cerium ions (Patent Document 8). It does not synthesize nanoparticles.

In recent years, there has been concern about the harmfulness of ultraviolet rays on the human body triggered by the problem of ozone layer destruction. Resins and paints are also affected by ultraviolet rays when exposed to sunlight, and there is a problem that they deteriorate over time, causing discoloration or cracks. Therefore, various organic and inorganic ultraviolet shielding materials are being developed as a measure for preventing such damage. The fine particles of cerium oxide, together with fine particles of metal oxides such as titanium dioxide, zinc oxide, and iron oxide, are known as substances having a large ultraviolet shielding effect, and are effective substances as inorganic ultraviolet shielding materials.

On the other hand, fine particles of metal oxides such as cerium oxide have photocatalytic or thermal catalytic action, and when they are simply blended into cosmetics, paint materials, plastics, etc., the organic substance components in them are contained. There is a problem that there is a possibility of deterioration and alteration. In order to improve the shielding efficiency of ultraviolet rays, it is desirable to make the particles as small as possible. In general, however, these metal oxide fine particles are very likely to aggregate and should be uniformly dispersed in the substance to be added. For this reason, there was a problem that the inherent ultraviolet shielding effect could not be fully exhibited.

Therefore, as means for solving such problems, attempts have been made to coat metal oxide fine particles with an inorganic compound having no catalytic activity and to control the form. One example is a proposal of composite particles in which a metal or metal oxide having an ultraviolet shielding function is encapsulated with silica (Patent Document 9). The composite particles are characterized in that the primary particles have a scale-plate shape, but are produced by hydrothermal synthesis, and the dispersion state of the metal or metal oxide is not clear.

Regarding metal oxide particles coated with silica, there is a method of producing modified silica-coated particles by applying a sol-gel reaction (Patent Document 10). However, since a process of pulverizing the coated powder is required, it is not effective from the viewpoint of controlling the form and particle size. An ultraviolet shielding material in which cerium oxide fine particles and cerium-containing composite oxide fine particles are coated with an amorphous or crystalline inorganic compound by hydrothermal synthesis has been considered (Patent Document 11). It is not suitable for controlling the diameter.

It has been continuously attempted to coat metal oxide fine particles with silica, and has a structure in which one or a plurality of cerium oxides or titanium oxides are contained in particles having a particle diameter of 20 to 100 nm made of silica. Fine particles have been proposed (Patent Document 12). This technique does not extend to the control of particle morphology and particle size. In a technique in which a metal oxide powder is coated with silica having a film thickness of 0.1 to 100 nm, the silica is selectively deposited on the surface by bringing the metal oxide powder into contact with the composition for forming a silica film. It was also manufactured (Patent Document 13). However, even with this technique, the form and particle size of the silica-coated metal oxide of the product cannot be clearly controlled.

The widespread use of cerium compounds, especially ceria, ie cerium oxide, in various fields is summarized in a recent review (Non-Patent Document 1).
JP-A-2005-519845 JP 2002-201023 Special Table 2002-515393 Special table 2007-504091 Special table 2009-5111403 JP2008-044817 JP 2006-281127 A JP 2004-313971 A Japanese Patent Laid-Open No. 11-11927 JP 2000-319128 A JP2001-139926 JP 2003-253249 A JP 2004-115541 A Masakuni Ozawa "Material Integration" Vol. 23, No. 1 (2010) 40-45

The object of the present invention is, firstly, a cerium oxide nanoparticle-zeolite composite having nano-scale fine particle diameters and having cerium oxide nanoparticles having a uniform particle diameter dispersed in zeolite. Is to provide. Providing a method for producing this complex is also included in the object of the present invention.

Secondly, the object of the present invention is that nano-level cerium oxide nanoparticles having a fine particle size and uniform particle size are made of a metal other than Ce, that is, Ca, Pr, Nd, Sm or Gd. It is an object of the present invention to provide a metal oxide solid solution cerium oxide nanoparticle-zeolite composite which exists in a form dispersed in zeolite as particles in which the oxide is incorporated as a solid solution. Providing a method for producing this complex is also included in the object of the present invention.

Thirdly, the object of the present invention is to obtain a nano-sized fine particle diameter separated from the cerium oxide nanoparticle-zeolite composite or metal oxide solid solution cerium oxide nanoparticle-zeolite composite described above, The object is to provide cerium oxide nanoparticles or metal oxide solid solution cerium oxide nanoparticles having a uniform diameter. Providing a method for producing these nanoparticles is also included in the object of the present invention.

The purpose of the application of the present invention is to provide a cerium oxide nanoparticle-zeolite composite or metal oxide solid solution cerium oxide nanoparticle-zeolite composite of the above-described form, or cerium oxide nanoparticle or metal oxide solid solution. By providing cerium oxide nanoparticles, it is difficult to handle the common handling of nanoparticles, which are generally strong in cohesion, and they exhibit excellent performance as an ultraviolet shielding material, while suppressing the catalytic activity by surface coating. To provide a substance.

The cerium oxide nanoparticle-zeolite complex in which cerium oxide nanoparticles are mixed in a zeolite form of the present invention exists in a form in which cerium oxide CeO ₂ nanoparticles having a particle diameter of 1 to ₂₀ nm are dispersed in the zeolite. It is a complex. The composite zeolite may be the one that maintains the original crystal structure, or may be one that has been destroyed by heating, for example, or the intermediate microstructure has been destroyed. However, it may be in a stage where the apparent crystal form is maintained.

The metal oxide solid solution cerium oxide nanoparticle-zeolite composite, which is present in the form in which the cerium oxide nanoparticles of the present invention are dispersed in zeolite as a solid solution of a metal oxide other than Ce, has the same particle size. It is a cerium oxide CeO ₂ nanoparticle of 1 to ₂₀ nm, and is a composite that exists in a form dispersed in zeolite as particles in which an oxide of Ca, Pr, Nd, Sm, or Gd is incorporated as a solid solution. Also in this case, the composite zeolite may maintain the original crystal structure, as described above, or may be, for example, a material whose crystal structure has been destroyed by heating, It may be of the stage.

The method of the present invention for producing a cerium oxide nanoparticle-zeolite composite in which cerium oxide nanoparticles are dispersed in zeolite is immersed in an aqueous solution of a soluble salt of Ce, and is 100 ° C. or less. After performing ion exchange between K ⁺ or Na ⁺ and Ce ³⁺ ions in the zeolite at a temperature of at least 10%, Ce ions were present at an exchange rate of at least 10%, and then in an oxidizing atmosphere, It comprises forming cerium oxide CeO ₂ nanoparticles by firing at a temperature.

The present invention for producing a metal oxide solid solution cerium oxide nanoparticle-zeolite composite in which cerium oxide nanoparticles are dispersed in zeolite as particles in which a metal oxide other than Ce is incorporated as a solid solution In the method, the zeolite is immersed in an aqueous solution containing a mixture of a soluble salt of Ce and at least one salt selected from metals other than Ce, ie, soluble salts of Ca, Pr, Nd, Sm, and Gd. Perform ion exchange between K ⁺ or Na ⁺ and Ce ³⁺ ions and ions of metals other than Ce in zeolite at a temperature of ℃ or less, and Ce ions and ions of metals other than Ce exist at an exchange rate of at least 10%. After that, by firing at a temperature of 200 ° C. or higher in an oxidizing atmosphere, a metal oxide other than Ce is taken in as a solid solution. It consists in forming a cerium oxide CeO ₂ nanoparticles.

The method for producing cerium oxide nanoparticles having a fine particle size at a nano level and having a uniform particle size according to the present invention is obtained by allowing an acid or an alkali to act on the above cerium oxide nanoparticle-zeolite composite. And the cerium oxide nanoparticles remaining without being dissolved are separated and obtained by filtration. The method for producing metal oxide solid solution cerium oxide nanoparticles having a fine particle size of nano level and uniform particle size of the present invention is similar to the above metal oxide solid solution cerium oxide nanoparticles. -An acid or alkali is allowed to act on the zeolite composite to dissolve the zeolite, and the metal oxide solid solution cerium oxide nanoparticles remaining without being dissolved are separated and obtained by filtration.

In the cerium oxide nanoparticles of the present invention, cerium (III) given to zeolite by ion exchange between K ⁺ or Na ⁺ ions and cerium ions Ce ³⁺ oxidizes cerium (IV) by calcination in an oxidizing atmosphere. It is formed by the mechanism of becoming an object. In general, when a zeolite ion-exchanged with metal ions is heated, after the zeolite structure is decomposed, usually an aluminosilicate metal salt or an aluminate metal salt is produced, and an ion-exchanged metal oxide is not produced. The present invention realizes cerium oxide nanoparticles for the first time by a novel route that could not be predicted from the knowledge that those skilled in the art had so far. The ion exchange between the zeolite and the cerium ion Ce ³⁺ and the calcination thereof are simple operations, and no special apparatus or operation is required, and the present invention can be easily implemented at low cost.

The fine particles of cerium oxide known so far are difficult to control the particle size, and when they are made fine particles, they tend to aggregate and only those having insufficient dispersibility can be obtained. According to the present invention, cerium oxide nanoparticles mixed in a well-dispersed state in zeolite are obtained, and if desired, a composite in which cerium oxide nanoparticles are dispersed therein while maintaining the crystal form and particle size of zeolite. Therefore, it is possible to provide an additive in the form of a fine powder that exhibits an ultraviolet shielding effect in a state where the catalytic performance of cerium oxide is suppressed.

As seen in the examples described later, when the composite of the present invention obtained using Linde Q zeolite is observed with a transmission electron microscope, nano-sized crystal particles of several tens of nanometers are dispersed inside the hexagonal plate-like particles. The particle size is extremely uniform. When the light reflectance of the obtained sample was measured, it was confirmed that excellent shielding ability was exhibited in the ultraviolet region.

As described above, the composite of the present invention in which nanoparticles of cerium oxide are dispersed in zeolite serves as an ultraviolet shielding material, and as described in the recently published review (Non-Patent Document 1). Furthermore, it has uses as an abrasive, a catalyst, and a fuel cell electrode material. When this composite is added to a plastic material, it exhibits the action of preventing its oxidation, and can be used, for example, in the production of a plastic film with improved weather resistance.

This fact is the same when the cerium oxide is a metal oxide solid solution cerium oxide. The composite of the present invention in which cerium oxide nanoparticles are dispersed in zeolite as particles in which a metal oxide other than Ce is incorporated as a solid solution has unique characteristics corresponding to the type of the solid solution metal. It has. For example, when Pr or Nd is dissolved in Ce, the performance as a catalyst is improved. When Gd or Sm is dissolved, the conductivity is increased, and when Ca is dissolved, the whiteness is increased, and the catalyst performance is decreased, and the tendency to decompose organic substances such as fats and oils is reduced. In particular, it is suitable as an ultraviolet shielding material in cosmetics.

If desired, the nanoparticles of the cerium oxide or metal oxide solid solution cerium oxide of the present invention can be obtained as a simple substance by separating from the complex with the zeolite. The performances possessed can be used for the various applications described above.

As the zeolite used in the present invention, any zeolite can be selected as long as it can incorporate cerium ions into its structure by ion exchange. In order to produce a plate-like composite suitable for applications such as an ultraviolet shielding material, zeolite having a plate-like crystal form such as clinoptilolite is suitable. Of these, Linde Q zeolite is preferred. Linde Q zeolite has a hexagonal plate-like crystal itself and a large ion exchange capacity. The zeolite preferably has a diameter of 0.5 to 10 μm, a thickness of 10 to 200 nm, and an aspect ratio of 5 or more.

In order to exchange K ⁺ ions and Na ⁺ ions pre-existing in the zeolite with Ce ³⁺ ions, the zeolite is dispersed and suspended in an aqueous solution of a soluble salt such as cerium nitrate or chloride, and the temperature is below 100 ° C. Ion exchange with. By selecting the cerium ion concentration of the ion exchange solution, the Ce ion exchange rate of the zeolite, that is, the Ce ion content can be controlled.

After the ion exchange, the ion exchanger is calcined in an oxidizing atmosphere or in the air to oxidize cerium (III) → (IV) to generate cerium oxide particles. If the calcination temperature is selected from 800 to 900 ° C., it is possible to achieve both the production of cerium oxide and the maintenance of the morphology and particle size of the zeolite. By adjusting the calcination temperature and additionally adjusting the ion exchange rate, it is possible to obtain a composite that maintains the zeolite structure, or to obtain a composite that is made amorphous by decomposing the zeolite. You can also. When maintaining the zeolite structure, if desired, metal ions such as silver ions having antibacterial properties can be incorporated into the structure by ion exchange.

In the following examples, sample characterization and performance tests were performed as follows.
[Measurement of ion exchange rate]
An ion exchange sample is decomposed with an acid, and Ce and K are quantified with an inductively coupled plasma emission spectrometer (“ICPS-8000” manufactured by Shimadzu Corporation) to obtain an ion exchange rate.
[Identification of crystalline phases of ion exchange and heated samples]
Using powder X-ray diffraction (XRD) (Mac Science MXP3A, Rigaku Denki RINT-2550H).
[Observation of crystal morphology]
Observed with a scanning electron microscope (SEM) (JEOL JSM-6100) and a transmission electron microscope (TEM) (JEOL JEM-2100EX).
[Reflection characteristics]
The reflection spectrum of the heated sample is measured with a self-recording spectrophotometer (with JASCO V-570 integrating sphere).

Composite of cerium oxide nanoparticles and zeolite (1)
The average particle diameter of 1.17 .mu.m, K-type Linde Q zeolite having a hexagonal plate-like crystal form having a thickness of about _{100nm (K 2 O · Al 2} O 3 · 2SiO 2 · xH 2 O hereinafter abbreviated as "Linde Q") Was synthesized. In each 60 mL of an aqueous solution in which the concentration of cerium nitrate Ce (NO ₃ ) ₃ was selected to be 0.025, 0.05, 0.1, 0.15, 0.2 and 0.25 mol / L, 8 g of the above Linde Q was added. Each was charged and kept in a constant temperature bath at 90 ° C. for 24 hours for ion exchange treatment. The ion-exchanged sample was filtered through a membrane filter, washed with distilled water, and then dried at 50 ° C. to obtain cerium-exchanged Linde Q. (Hereinafter referred to as “ion exchange sample”)

The ion exchange rate of the above ion exchange sample was determined, the crystal phases of the ion exchange sample and the heated sample were identified, and the crystal morphology was observed. Furthermore, the reflection spectrum of the heated sample was measured.
Table 1 shows the results of quantitative analysis of the ion exchange sample. It was confirmed that K ⁺ in Linde Q was exchanged with Ce ³⁺ .

Table 1 Chemical analysis of Ce-exchanged Linde Q zeolite

In FIG. 1, the XRD pattern of the sample which heated the ion exchange sample at 800 degreeC is shown. From this figure, the sample with an ion exchange rate of 11.3% is beginning to lose its structure when heated to 800 ° C., but the sample with an ion exchange rate of 25.4% or more maintains the zeolite structure. Recognize. Linde Q is known to have improved thermal stability by ion exchange with Eu ³⁺ and Tb ³⁺ , but it has been clarified that thermal stability is improved in Ce ³⁺ ion exchange as well. Since the crystallinity of the heated sample differs depending on the ion exchange rate, it has been found that the degree of improvement in the thermal stability of Linde Q depends on the Ce content.

In FIG. 2, the SEM photograph of the heating sample heated at 800 degreeC is shown. It was confirmed that all the 800 ° C. heated samples maintained the hexagonal plate shape of Linde Q over the entire range of the tested Ce ion exchange rate of 11.3 to 80.5%.

Next, the influence of the heating temperature was examined using a sample having an ion exchange rate of 47.6%. The ion exchange sample was heated to a predetermined temperature in the range of 50-1000 ° C. FIG. 3 shows an XRD pattern of the heated sample, and FIG. 4 shows an SEM observation image.

The Ce ion exchange sample having an ion exchange rate of 47.6% was found to maintain the crystal structure up to 800 ° C. This improvement in thermal stability is almost similar to Eu and Tb exchanged Linde Q. Furthermore, although the structure began to break upon heating at 850 ° C., it was found that the hexagonal plate shape was maintained even at 900 ° C. heating. By heating at 1000 ° C., the structure of Linde Q was completely decomposed and the hexagonal plate was melted. A wide peak appeared in the vicinity of 28.6 °, 33.1 °, 47.5 °, and 56.3 ° from the heated sample at 850 ° C. or higher, confirming the formation of cerium oxide. The diffraction peak of cerium oxide becomes stronger as the heating temperature increases, and the growth of crystals is estimated.

Table 2 shows the result of obtaining the crystallite size from the diffraction peak width. It was estimated that cerium oxide was a nanoparticle having a crystal grain size of about 15 to 30 nm. It has also been found that the higher the heating temperature and the higher the ion exchange rate, in other words, the larger the Ce content, the larger the size of the cerium oxide crystallite, that is, the complete crystal.

Table 2 Crystallite size of cerium oxide

Next, FIG. 5 shows a TEM observation image of a 900 ° C. heated sample having an ion exchange rate of 47.6%. It has been clarified that cerium oxide particles having a size of several tens of nanometers are formed and dispersed in the structure of the hexagonal plate-shaped Linde Q. The cerium oxide particles had a uniform particle size and a distribution of about ± 2 nm.

FIG. 6 shows reflection spectra of samples obtained by heating ion exchange samples ion-exchanged at various exchange rates to 800 ° C. It was confirmed that the heated sample of Ce ion-exchanged Linde Q absorbs ultraviolet rays. Furthermore, the higher the Ce ion exchange rate, the higher the ultraviolet absorption rate. This increase in UV absorption seems to correlate with the content of cerium oxide present in the Linde Q structure. On the other hand, the reflection spectrum of a sample obtained by heating an ion exchange sample having a Ce ion exchange rate of 47.6% to various temperatures of 200 ° C. to 1000 ° C. was obtained, and the result of FIG. 7 was obtained.

On the other hand, a TEM observation was performed on a sample obtained by heating an ion exchange sample having a Ce ion exchange rate of 47.6% to 200 ° C. to obtain a photograph of FIG. In this TEM image, cerium oxide crystals are not clearly visible. The XRD pattern of FIG. 3 also does not show the formation of cerium oxide crystals. However, as shown in the reflection spectrum of FIG. 7, this sample has the ability to absorb ultraviolet rays. From these facts, it is understood that in the sample heated at 200 ° C., cerium oxide was generated, but crystals did not develop. That is, it is considered that the Ce—O bond absorbs ultraviolet rays. In short, the cerium oxide in the composite of the present invention is not limited to the case where a clear crystal is formed, and even in the case where the crystal is not developed as in this example, the cerium oxide is one having a Ce-O bond. It is a word that encompasses all.

Composite of cerium oxide nanoparticles and zeolite (2)
Na zeolite _{X (Na 2 O · Al 2} O 3 · 2.5SiO 2 · xH 2 O) Teflon sealed container to 8g weighed, Ce (NO _{3) 3} ion exchange solution (Ce (NO ₃ ) ₃ concentration: 0.1 mol / L) was added in an amount of 60 ml, and ion exchange treatment was performed in a thermostat at 90 ° C. for 24 hours. The ion exchange sample was dried at 50 ° C. after filtration and washing. An ion exchange sample obtained by ion exchange was heated to 900 ° C. for 1 hour in the air to obtain a heated sample.

When this heated sample was observed by X-ray diffraction analysis, it was found that the zeolite X peak was lost and the zeolite structure was completely destroyed. Instead, broad peaks appeared in the vicinity of 28.6 °, 33.1 °, 47.5 °, and 56.3 °, confirming the formation of cerium oxide.

In a solution for ion exchange prepared at a concentration of 0.1 mol / L of cerium oxide nanoparticles Ce (NO ₃ ) ₃ in which other metal oxides are dissolved , ions of metals other than Ce (Ca ions, Pr ions, Nd Ion, Sm ion, or Gd ion) was added in an internal ratio of 20 mol% to prepare a solution in which two kinds of metal ions were mixed. 8 g of K-type Linde Q (K ₂ O.Al ₂ O ₃ .2SiO ₂ .xH ₂ O) is weighed into a Teflon (registered trademark) sealed container, 60 mL of the above mixed solution is added, and it is kept in a constant temperature bath at 90 ° C. for 24 hours. The ion exchange treatment was performed. The ion exchange sample was filtered and washed, and then dried at 50 ° C. to obtain a cerium-other metal ion composite exchange zeolite. This ion composite exchanged zeolite was heated to 900 ° C. for 1 hour in the air to obtain a heated sample.

When these heated samples were analyzed by X-ray diffraction, it was found that the structure of Linde Q was completely destroyed by heating at 900 ° C. or higher. Also in this case, instead of the Linde Q peak, a wide range of peaks appeared around 28.6 °, 33.1 °, 47.5 °, and 56.3 °, confirming the formation of cerium oxide. . As a result of observation with a scanning electron microscope, it was found that samples obtained from all the mixed solutions maintained a hexagonal plate shape.

When composition analysis was performed by energy dispersive X-ray fluorescence analysis attached to the scanning electron microscope, the following data was obtained, and it was confirmed that cerium and other metals coexisted in any sample.

Table 3 X-ray fluorescence analysis of metal oxide solid solution cerium oxide nanoparticles

Separation of cerium oxide nanoparticles The Linde Q zeolite obtained in Example 1, which was ion exchanged with Ce at an ion exchange rate of 71.4%, was heated to 900C. To 0.1 g of the obtained cerium oxide-zeolite composite, 5 mL of 46% HF solution and 5 mL of 36% HCl solution were added and heated to dissolve the zeolite. After evaporation to dryness, 10 mL of water and a small amount of HCl were added to dissolve and remove soluble components, followed by filtration and washing. The obtained cerium oxide nanoparticles alone were observed with a TEM to obtain a photograph of FIG.

Each figure is data of the embodiment of the present invention and has the following contents.
In Example 1, the XRD chart of the sample which heated the ion exchange sample which carried out the ion exchange of the Linde Q zeolite with cerium at various exchange rates at 800 degreeC. FIG. 2 is an SEM photograph of a heated sample whose XRD chart is shown in FIG. 1 and having a Ce ion exchange rate of 11.3% and 80.5%. In Example 1, the XRD chart of the sample which heated the sample ion-exchanged by Ce ion exchange rate 47.6% to the various temperature of the range of 50-1000 degreeC. FIG. 4 is an SEM photograph of a heated sample whose XRD chart is shown in FIG. 3 and heated to 200 ° C., 850 ° C., 900 ° C. or 1000 ° C. In Example 3, the TEM photograph of the sample which heated the ion exchange sample whose Ce ion exchange rate is 47.6% to 900 degreeC. The lower row is an enlarged view in the upper white frame. The reflection spectrum of the sample which heated the ion exchange sample obtained in Example 1 by ion exchange with various exchange rates at 800 degreeC. The reflection spectrum of the sample obtained in Example 1 which heated the ion exchange sample of Ce ion exchange rate 47.6% to various temperatures (200 degreeC-1000 degreeC). 4 is a TEM photograph of a sample obtained by heating an ion exchange sample obtained in Example 1 having a Ce ion exchange rate of 47.6% to 200 ° C. FIG. In Example 4, the TEM photograph of the cerium oxide nanoparticle simple substance obtained by heating an ion exchange sample with a Ce ion exchange rate of 71.4% to 900 ° C., and then dissolving and removing the zeolite by applying an acid.

Claims (13)

A cerium oxide nanoparticle-zeolite composite in which cerium oxide CeO ₂ nanoparticles having a particle diameter of 1 to ₂₀ nm are present in a dispersed form in zeolite. As the zeolite, “Linde Q” type zeolite having the composition of K ₂ O.Al ₂ O ₃ .2SiO ₂ .xH ₂ O and having a hexagonal plate-like crystal form is used, and the zeolite maintains its original crystal form. The cerium oxide nanoparticle-zeolite composite according to claim 1. The cerium oxide nanoparticle-zeolite composite according to claim 1, wherein the zeolite in which the cerium oxide nanoparticles are dispersed therein loses its original crystal form upon heating. A method for producing a composite in which cerium oxide nanoparticles are mixed in a form dispersed in zeolite according to any one of claims 1 to 3, wherein the zeolite is immersed in an aqueous solution of a soluble salt of Ce and is 100 ° C or lower. After ion exchange between K ⁺ or Na ⁺ and Ce ³⁺ ions in the zeolite at a temperature of 10 ° C., Ce ions were present in the zeolite at an exchange rate of at least 10%, and then in an oxidizing atmosphere, 200 ° C. A production method comprising forming a cerium oxide CeO ₂ nanoparticle-zeolite complex by firing at the above temperature. A method for producing cerium oxide CeO ₂ nanoparticles having a particle diameter of 1 to ₂₀ nm, wherein an acid or an alkali is allowed to act on the cerium oxide nanoparticle-zeolite complex according to any one of claims 1 to 3. A production method comprising dissolving and obtaining cerium oxide nanoparticles remaining undissolved by filtration. In a form in which nanoparticles of cerium oxide CeO ₂ having a particle diameter of 1 to 20 nm are dispersed in zeolite as particles in which an oxide of Ca, Pr, Nd, Sm or Gd (hereinafter “metal other than Ce”) is incorporated as a solid solution. Metal oxide solid solution cerium oxide nanoparticle-zeolite complex present. As the zeolite, a “Linde Q” type zeolite having a composition of K ₂ O.Al ₂ O ₃ .2SiO ₂ .xH ₂ O and having a hexagonal plate-like crystal form is used, and the zeolite has its original crystal form. The metal oxide solid solution cerium oxide nanoparticle-zeolite composite of claim 6 maintained. The metal oxide solid solution cerium oxide nanoparticle-zeolite composite according to claim 6, wherein the zeolite in which the cerium oxide nanoparticles are dispersed therein loses its original crystal form upon heating. A method for producing a composite in which cerium oxide CeO ₂ nanoparticles according to any one of claims 6 to 8 are present in a form dispersed in zeolite as particles in which an oxide of a metal other than Ce is incorporated as a solid solution. And immersing the zeolite in an aqueous solution containing a mixture of a soluble salt of Ce and a salt selected from at least one soluble salt of a metal other than Ce, and K ⁺ in the zeolite at a temperature of 100 ° C. or lower. After performing ion exchange between Na ⁺ and Ce ³⁺ ions and ions of metals other than Ce, Ce ions and ions of metals other than Ce exist in the zeolite at an exchange rate of at least 10%, and then an oxidizing atmosphere below, by firing at 200 ° C. or higher, the metal oxide solid solution of cerium oxide CeO ₂ Na incorporating an oxide of a metal other than Ce solid solution Particles - production method consists in forming the zeolite complex. A method for producing a metal oxide solid solution cerium oxide CeO ₂ nanoparticle having a particle diameter of 1 to ₂₀ nm, wherein an acid or an alkali is added to the cerium oxide nanoparticle-zeolite complex according to any one of claims 6 to 8. A production method comprising dissolving zeolite by acting, and separating and obtaining metal oxide solid solution cerium oxide nanoparticles remaining without being dissolved. A sunscreen cosmetic comprising the cerium oxide nanoparticle-zeolite composite according to claim 2 or 3 or the metal oxide solid solution cerium oxide nanoparticle-zeolite composite according to claim 7 or 8 added to a cosmetic base. Deterioration due to ultraviolet rays formed by dispersing the cerium oxide nanoparticle-zeolite composite according to claim 2 or 3 or the metal oxide solid solution cerium oxide nanoparticle-zeolite composite according to claim 7 or 8 in a vehicle. Prevented paint. Deterioration due to ultraviolet rays formed by kneading and molding a cerium oxide nanoparticle-zeolite composite according to claim 2 or 3 or a metal oxide solid solution cerium oxide nanoparticle-zeolite composite according to claim 7 or 8 into a plastic material. Prevents plastic molded products.

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