JP2000203810A - Hollow oxide powder particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To advantageously increase the specific surface area of a hollow oxide powder particle which is a nearly spherical particle containing a principal component composed of at least one kind of alumina, a spinel, iron oxide, yttrium oxide and titanium oxide while reducing the weight thereof by providing the particle with a peridium dividing a hollow chamber having a specific value or below of thickness. SOLUTION: This hollow oxide powder particle is obtained by adding an organic solvent to an aqueous solution prepared by dissolving and/or suspending a metal salt, as necessary, using a dispersing agent, forming a W/O type emulsion having 100 nm to 10 μm waterdrop diameter, then spraying and burning the W/O type emulsion and oxidizing metal ions. The resultant hollow oxide powder particle is composed of at least one kind of alumina, a spinel, iron oxide, yttrium oxide and titanium oxide as a principal component. The hollow oxide powder particle is nearly spherical and the average diameter is 50 nm to 5 μm. The thickness of a peridium dividing a hollow chamber is <=20 μm and the specific surface area of the particle based on 1 g weight can be regulated to 130-400 m2/g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to hollow oxide powder particles.

[0002]

2. Description of the Related Art Hollow oxide powder particles have a larger specific surface area than solid particles (non-hollow particles). The specific surface area means (surface area / weight). Utilizing the specific surface area, the hollow oxide powder particles are expected to be used in various aspects. For example, catalyst carriers, masking agents, microcapsules and the like.

[0003] Conventionally, many techniques relating to hollow oxide powder particles have been reported. However, the shell thickness is 20n
m or less ultra-thin hollow oxide powder particles have not been reported. According to JP-A-63-258842, an organic solvent is added to and mixed with an aqueous solution of an inorganic compound to form an O / W emulsion, and then the O / W emulsion is added to an organic solvent containing a lipophilic surfactant. To produce an O / W / O emulsion, and the O / W / O emulsion is
A technique is disclosed in which an aqueous solution of a compound capable of forming a precipitate of a water-insoluble precursor is added and mixed to form hollow particles. However, according to this technique, hollow particles having a shell thickness of 20 nm or less have not been obtained.

According to JP-A-3-47528, an emulsion is formed by mixing an aqueous solution of a metal compound with a first oil and a second oil, and water and oil are removed from the emulsion and decomposed to form a metal oxide. A technique for obtaining a ceramic hollow sphere is disclosed. Even in this technique, hollow particles having a shell thickness of 20 nm or less have not been obtained. According to JP-A-60-122779, an alumina / magnesia spinel porous powder obtained by spray pyrolysis is used as a starting material, which is molded and fired to obtain a pore diameter,
A technique for forming a porous body with good control of the pore size distribution has been disclosed. In this technique, the size of the water droplet to be sprayed becomes one reaction field. However, the size of the spray water droplet is several tens μm under an efficient condition, and the reaction field is one order of magnitude larger than that of the emulsion combustion method. Although there is no description about the thickness of the crust in this publication, it is considered that hollow particles having a crust thickness of 20 nm or less cannot be obtained in consideration of one sprayed water droplet becoming one particle. Can be

[0005] JP-A-8-91821 discloses a technique for producing hollow silica by an alkoxide sol-gel method. In this publication, there is no description about the thickness of the crust, but the particle size of the obtained silica powder particles is 2 to
Since it is as large as 8 μm, it is hard to imagine a hollow particle having a shell thickness of 20 nm or less. Ceram.In
ter., vol., 14 (1988), 239-244, discloses a technique for producing hollow alumina by an emulsion evaporation method. However, judging from the SEM photograph of this document, the thickness of the crust is several hundred nm or more.

[0006]

In the above-mentioned prior art, there is a demand for further increasing the specific surface area of the hollow oxide powder particles. The present invention has been made in view of the above circumstances, and has as its object to provide hollow oxide powder particles that are advantageous for further increasing the specific surface area.

[0007]

The inventor has been diligently developing the production of hollow oxide powder particles having an extremely thin shell. Then, the present inventor forms a W / O emulsion having an appropriate water droplet diameter by adding an organic solvent to an aqueous solution in which a metal salt is dissolved or suspended,
By spraying and burning this W / O emulsion, it was found that hollow oxide powder particles having an extremely thin crust with a thickness of 20 nm or less can be formed, and confirmed by a test. The oxide powder particles were completed.

That is, the hollow oxide powder particles according to the present invention have a crust for partitioning the hollow chamber, and the crust has a thickness of 20 n.
m or less. The thickness is 1
It means the average thickness of the crust in individual particles. Hollow oxide powder particles according to the present invention, because the thickness of the shell is thin,
It has a large specific surface area compared to solid particles. Therefore, as compared with solid particles, it is lightweight and easy to handle for its volume. Further, it is effective for a catalyst carrier, an adsorbent, and the like that require a high specific surface area. Further, since it is hollow, it has low thermal conductivity and is effective as an additive to a heat insulating material.

Further, when the thickness of the shell is small, the elasticity of the hollow oxide powder particles is generally improved as compared with the case where the shell is thick. Therefore, even when a large external force is applied to the hollow oxide powder particles, the particles are less likely to be damaged or broken as compared with a case where the shell of the particles is thick. The thickness of the shell of the hollow oxide powder particles according to the present invention is 20 nm or less. The thickness of the crust is different depending on manufacturing conditions, for example, factors such as the composition and concentration of the water phase and the oil phase constituting the emulsion, spraying conditions, and combustion conditions.
It can be 18 nm or less, 16 nm or less. Alternatively, it can be 14 nm or less, or 12 nm or less.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The particle diameter (each particle diameter or average diameter) of the hollow oxide powder particles according to the present invention can be appropriately selected, and the lower limit of the particle diameter can be 40 nm, 50 nm, 60 nm, and the upper limit. Values of 5 μm and 10 μm can be adopted. Although the hollow oxide powder particles according to the present invention vary depending on the production conditions, they are preferably substantially spherical, or preferably pseudo-spherical, but are not limited thereto.
A slightly deformed shape may be used.

A main component of the shell constituting the hollow oxide powder particles according to the present invention is an oxide. The oxide may be a simple oxide or a composite oxide. For example, it can be composed of at least one of alumina, spinel, iron oxide, yttrium oxide and titanium oxide. In particular, alumina can be used. Alternatively, a composite oxide containing aluminum as a main component can be used.

The shell may be in a smooth form. Alternatively, the shell may be in a form having fine irregularities or a porous form. In this case, the specific surface area of the hollow oxide powder particles tends to increase, and the specific surface area of the particles per 1 g of weight can be set to, for example, 130 to 400 m ² / g, depending on the degree of unevenness and porosity. In producing the hollow oxide powder particles according to the present invention, the following method can be adopted. That is, an emulsification step is performed in which an organic solvent is added to an aqueous solution in which a metal salt is dissolved and / or suspended to form a W / O emulsion having a predetermined water droplet diameter. Thereafter, a powdering step of forming a hollow oxide powder particle by spraying and burning the W / O emulsion is performed.

In the emulsification step, an organic solvent is added to and mixed with an aqueous solution in which a metal forming an oxide is dissolved to be ionic or finely suspended, and the mixture is mixed with an organic solvent as a matrix. This is a step of forming an / O emulsion. The water droplet diameter in this W / O emulsion is preferably 100 nm or more. Especially 100 nm to 10 μm
Can be. If the water droplet diameter is less than 100 nm, the water droplets are completely shrunk before the formation of the oxide crust on the surface side of the water droplets, and the oxide is not hollow and tends to be solid particles, which is not preferable. On the other hand, if the water droplet diameter is larger than 10 μm, the reaction field becomes too large, and it takes time to form an oxide, and the composition of the product may be non-uniform.

In order to obtain the above-mentioned water droplet diameter, if necessary,
It is preferable to adjust the particle size of the water droplet using a dispersant. The type and amount of the dispersant are not limited. For example, any of a cationic surfactant, an anionic surfactant, and a nonionic surfactant can be used,
Depending on the type of the aqueous solution and the organic solvent and the required water droplet diameter, the type and amount of the dispersant can be changed and used.

The above-described emulsion combustion method is a short-time process in which heating of water droplets containing a metal salt, water evaporation, and metal oxidation are instantaneously generated by burning an organic solvent in a W / O emulsion. In other words, the hollow oxide particles are referred to as 1) water evaporation on the surface of the water droplet, 2) shrinkage of the water droplet and nucleation of crystallites on the surface of the water droplet, 3) growth and sintering of the crystallites generated. It is thought to be synthesized by a mechanism.

The above-mentioned powdering step is a step of forming a hollow oxide powder by spraying and burning the W / O emulsion. When the W / O emulsion is sprayed into the heated reactor, the water droplets containing the metal are generally coated with an organic solvent on the outside, so that the organic solvent burns and the metal salt on the organic solvent side is formed. It is presumed that oxidation and evaporation of water occur, so that the oxide is formed in a shell shape to form a hollow oxide.

Since one water droplet diameter (several nm to several μm) of the W / O emulsion becomes the size of one reaction field, the occurrence of variation in temperature distribution can be suppressed, and a more uniform oxide powder can be obtained. The type of the metal salt is not particularly limited and can be selected according to the material of the hollow oxide powder particles.
For example, any water-soluble metal salt such as metal nitrate, metal acetate, metal sulfate and metal chloride can be used. The metal salt concentration of the metal salt aqueous solution is not limited. When the metal salt is in a suspended state, the particle size of the metal salt is preferably 1 μm or less, more preferably 0.1 μm or less. The type of the organic solvent used is not limited as long as it is hardly soluble in water and can form a W / O emulsion. For example, hydrocarbon-based organic solvents such as hexane, octane, kerosene, and gasoline are preferable. The mixing ratio of the aqueous solution component and the organic solvent component to be mixed when preparing the emulsion is not particularly limited. However, when the ratio of the water to be mixed exceeds 70%, the disperse phase of the emulsion and the dispersing medium may be inverted. In order to stably obtain a W / O emulsion, the water ratio is desirably 70% or less by volume.

The combustion temperature in the emulsion combustion is not particularly limited, but is preferably from 600 to 1000 ° C. 6
If the temperature is lower than 00 ° C., the combustion temperature is too low, and the organic solvent may not completely burn. On the other hand, when the temperature exceeds 1000 ° C.,
The synthetic powder tends to aggregate, which is not preferable. The combustion atmosphere is not particularly limited, but if oxygen is not sufficient, carbon components in the organic solvent may remain due to incomplete combustion. Therefore, it is desirable to supply oxygen (air) to such an extent that the organic solvent in the emulsion can be completely burned.

According to the emulsion combustion, when the oxide is alumina or a composite oxide containing aluminum as a main component, very thin hollow particles can be formed. Although the cause is not clear at present, it is presumed that the aluminum oxide has a high rate of forming a surface oxide film, so that a surface oxide film is formed at a stage where water droplet shrinkage is small, and as a result, the thickness becomes extremely thin.

The shell of the hollow oxide powder particles according to the present invention has, as described above, a form having fine irregularities, or
A porous form can also be adopted. In producing the hollow oxide powder particles of this embodiment, the following can be performed. A step of mixing an aqueous solution in which a metal salt is dissolved with an organic solvent to form a W / O emulsion;
In the step of synthesizing the oxide powder by spraying and burning the O-type emulsion, by appropriately selecting the spraying and burning conditions of the emulsion, oxide particles in which the progress of the oxidation reaction is insufficient are obtained. A contact step (hereinafter also referred to as water treatment) of bringing the oxide particles obtained in this step into contact with a solution containing water is performed. In the contacting step, the hydroxyl group remaining on the crystallite surface of the synthetic particles, the bond of the undecomposed metal salt is broken, and fine irregularities or a porous structure appear on the particle surface, so that the specific surface area of the particle is dramatically improved. Inferred.

The structural change of the particles due to the water treatment occurs on the particle surface. Therefore, the effect of the water treatment is small for solid particles having a small area ratio of the surface to the particle volume. On the other hand, since the hollow particles synthesized by emulsion combustion have a very small shell thickness, the area ratio of the surface to the particle volume is very large, and the effect of the water treatment is increased.

The type of solution used for water treatment is not particularly limited, except that it contains water. The solution is water,
At least one of deionized water, an acidic aqueous solution, an alkaline aqueous solution, and a mixed solution of water and an alcohol can be employed. Neutral water may be used, or an acidic solution such as nitric acid or hydrochloric acid, or an alkaline solution such as aqueous ammonia or aqueous sodium hydroxide may be used. Further, a solution obtained by mixing these solutions with a water-soluble organic solvent such as ethanol at an arbitrary ratio may be used. Further, the water treatment temperature and the water treatment time are not particularly limited. The state of the surface structure of the hollow oxide particles can be controlled by changing the type of the solution, the water treatment temperature, and the water treatment time. The method of contacting with a solution containing water is not particularly limited. For example, the synthesized oxide powder may be mixed with a solution containing water, or may be brought into contact with a sprayed solution.

[0023]

The present invention will be described more specifically with reference to the following examples. (Example 1) The hollow oxide powder particles according to Example 1
Alumina hollow particles having a crust thickness of 10 nm were manufactured through the following emulsification and powdering steps.

(Emulsification Step) In the aqueous phase, commercially available aluminum nitrate nonahydrate was added to deionized water at a concentration of 0.1 to 0.1%.
An aluminum nitrate aqueous solution dissolved at 2 mol / liter was used. Commercial kerosene was used as the organic solvent. As a dispersant for forming an emulsion, Sunsoft No. 818H manufactured by Taiyo Kagaku Co., Ltd. was used in an amount of 5 to 10% by weight based on kerosene. The kerosene containing the dispersant was used as an oil phase.

The water phase and the oil phase were mixed in such a manner that the aqueous phase / oil phase = (40-70) / (60-30) (%) by volume. The mixed solution of the aqueous phase and the oil phase was prepared using a homogenizer at a rotational speed of 1000 to 20000 rpm and 5 to 3 times.
The mixture was stirred for 0 minutes to obtain a W / O emulsion. From the result of observation with an optical microscope, the diameter of the water droplet in the emulsion was about 1 to 2 μm.

(Powdering step) W obtained as described above
Using an emulsion combustion reactor developed by the present inventors, the / O type emulsion was sprayed into an emulsion to burn the oil phase, and oxidized metal ions present in the aqueous phase to form oxide powder. . In this case, the sprayed emulsion completely burns and the flame temperature is 700
The spraying of the emulsion, the amount of air (the amount of oxygen) and the like were controlled so that the temperature became constant at ~ 1000 ° C. The obtained powder was collected by a bag filter installed at the rear of the reaction tube.

The shape of the obtained oxide powder was observed using a transmission electron microscope (TEM). FIG. 1 shows a low magnification TEM image of the produced powder. As shown in FIG. 1, the prepared powder was clearly thin hollow particles because the back side of the particles could be clearly observed. FIG. 2 shows a high magnification TEM image of the produced powder. The hollow particles had a shell thickness of about 10 nm.

(Example 2) The hollow oxide powder particles according to Example 2 are spinel powder particles having a shell thickness of about 20 nm, and were manufactured as follows. Commercially available aluminum nitrate nonahydrate and magnesium nitrate hexahydrate were converted to Al /
It was weighed so that Mg = 2/1 (molar ratio). This was dissolved in deionized water to prepare a mixed aqueous solution of aluminum nitrate and magnesium nitrate having a concentration of 0.1 to 2 mol / liter, which was used as an aqueous phase. In the oil phase, the emulsifying step, and the powdering step, the synthesis of the oxide powder was performed under the same conditions as in Example 1.

FIG. 3 shows a high magnification TE of the produced oxide powder.
An M image is shown. As in Example 1, the produced oxide powder was very thin hollow particles, and the thickness of the crust was less than 20 nm. (Example 3) Synthesis of other hollow oxide powder particles will be described as Example 3.

Magnesium nitrate hexahydrate was dissolved in deionized water, and a 0.1 to 2 mol / L aqueous metal solution was used as an aqueous phase. In the oil phase, the emulsifying step, and the powdering step, powder synthesis was performed under the same conditions as in Example 1. as a result,
It was confirmed that hollow oxide powder particles of magnesium oxide were obtained. The thickness of the crust was less than 20 nm. Iron nitrate nonahydrate is dissolved in deionized water, and 0.1 to 2 mol /
A metal aqueous solution of L was prepared and used as an aqueous phase. In the oil phase, the emulsifying step, and the powdering step, powder synthesis was performed under the same conditions as in Example 1. As a result, it was confirmed that hollow oxide powder particles of iron oxide were obtained. The thickness of the crust was less than 20 nm.

Yttrium nitrate hexahydrate was dissolved in deionized water, and a 0.1 to 2 mol / L aqueous metal solution was used as an aqueous phase. In the oil phase, the emulsifying step, and the powdering step, powder synthesis was performed under the same conditions as in Example 1. as a result,
It was confirmed that hollow oxide powder particles of yttrium oxide were obtained. The thickness of the crust was less than 20 nm. A metal aqueous solution of 0.1 to 2 mol / L was prepared by diluting titanium tetrachloride with deionized water, and this was used as an aqueous phase. In the oil phase, the emulsifying step, and the powdering step, powder synthesis was performed under the same conditions as in Example 1. As a result, it was confirmed that hollow oxide powder particles of titanium oxide were obtained.
The thickness of the crust was less than 20 nm.

Example 4 In Example 4, the aqueous phase and the organic solvent of Example 1 were used, and NP6 (polyoxyethylene (6) nonylphenyl ether) was used as a dispersant to be added. The molar ratio of water to NP6 is water / N
An emulsion having a water droplet diameter of 100 to 400 nm was obtained by adjusting P6 between 10 and 100. The powdering step was performed under the same conditions as in Example 1. As a result, as in Example 1, it was confirmed that hollow alumina particles having a shell thickness of 20 nm or less (about 15 nm) were obtained.

Comparative Example 1 In Comparative Example 1, the water droplet diameter was 100
Alumina powder particles were synthesized using the emulsion in a state smaller than nm. NP6 (polyoxyethylene (6) nonylphenyl ether) was used as a dispersant. In the same emulsification step as in Example 5,
An emulsion having a water droplet diameter of 30 to 80 nm was obtained by adjusting the molar ratio of water to NP6 between water and NP6 = 10 to 100. The powdering step was performed under the same conditions as in Example 1. As a result, the obtained particles did not become hollow.

Example 5 In Example 5, 0.1 to 0.1% of aluminum nitrate was prepared by dissolving aluminum nitrate in deionized water.
A 2 mol / L aqueous solution of aluminum nitrate was used as the aqueous phase.
Commercial kerosene was used as the organic solvent. As the dispersant, sun soft No. manufactured by Taiyo Kagaku Co., Ltd. 818H was used. The addition amount was 5 to 10 Wt% with respect to kerosene. The kerosene containing the dispersant was used as an oil phase. The water phase and the oil phase were mixed at a volume ratio such that water phase / oil phase = 50 to 70/50 to 30 (%). The mixed solution was mixed with a homogenizer for 10 minutes.
The mixture was stirred at a rotation speed of 00 to 20000 rpm for 5 to 30 minutes to obtain a W / O emulsion. According to the result of observation with an optical microscope, the water droplet diameter in the emulsion is about 1 to 2 μm.
Met.

The prepared emulsion was sprayed and burned using an emulsion combustion reactor to synthesize an oxide powder. The synthesis is performed so that the sprayed emulsion is completely burned and the flame temperature is a constant temperature of 600 to 800 ° C.
The test was performed while controlling the flow rate of the emulsion and the amount of air (the amount of oxygen). The obtained powder was collected by a bag filter installed at the rear of the reaction tube. As a result of TEM observation, the alumina powder synthesized under these conditions was hollow particles having a shell thickness of about 10 nm.

As is clear from the photograph in FIG. 5, the surface of the hollow oxide powder particles according to Example 5 in which the water treatment was not performed is very smooth. The specific surface area of the powder according to Example 5 in which the water treatment was not performed was 46 m.
² / g. This value is based on the assumption that the crust is smooth and nitrogen adsorption occurs on both sides (inside and outside) of the crust when measuring the specific surface area, the amount of aluminum ion in one water droplet, the particle size of the synthetic powder, the crust thickness, It almost corresponded to the specific surface area calculated from the density. Therefore, the particle surface was considered to be smooth from the viewpoint of the determined specific surface area.

Example 6 Deionized water was used as a water treatment solution. Then, 1 to 10 g of the synthetic powder according to Example 5 manufactured as described above was added to 10 to 100 of deionized water.
0 cc and water treatment. Using a magnetic stirrer, obtain the suspension at room temperature from 1 to 240
Stirred for minutes. The suspension after stirring was filtered and further washed several times with deionized water. The powder remaining on the filter paper is dried and crushed, and the shape is observed (SEM) and the specific surface is measured (B
ET). The SEM photograph in FIG. 4 is a photograph showing the particle structure obtained after the water treatment in Example 6. In the water treatment powder according to Example 6, as shown in FIG. 4, it can be seen that the smooth surface structure is broken and a structure with irregularities on the order of tens of nm (about 10 to 60 nm) appears.

(Examples 7 to 9) In Example 7, the powder synthesized by emulsion combustion in Example 5 was
Water treatment was performed in the same process as in Example 6. However, the water treatment solution was changed from deionized water to a 1 mol / L nitric acid aqueous solution. In Example 8, the powder synthesized by emulsion combustion in Example 5 was subjected to water treatment in the same process as in Example 6. However, the water treatment solution was changed from deionized water to a 1 mol / L aqueous ammonia solution.

In Example 9, the powder synthesized by emulsion combustion in Example 5 was subjected to water treatment in the same process as in Example 6. However, the water treatment solution was changed from deionized water to a mixed solution of deionized water and ethanol (1: 1 by volume). (Examples 10 to 13) In Example 10, the aqueous phase in the emulsion was converted from a 0.1 to 2 mol / L aluminum nitrate aqueous solution to a 0.1 to 2 mol / L aqueous solution of aluminum nitrate and sodium nitrate (mixing ratio). : Na in molar ratio
/ Al = 1/99), and Na-containing alumina particles were synthesized under the same conditions as in Example 5. The synthetic powder was hollow particles having a very thin crust (thickness of the crust: about 12 nm) as in Example 5. Of the obtained synthetic powder,
Example 10 was a synthetic powder which was not subjected to the subsequent water treatment.

In Example 11, the synthetic powder according to Example 10 was treated with deionized water in the same manner as in Example 6. As Example 12, the synthetic powder according to Example 10 was treated with a 1 mol / L nitric acid aqueous solution in the same manner as in Example 7. As Example 13, the synthetic powder according to Example 10 was treated with water using a 1 mol / L aqueous ammonia solution as in Example 8.

(Examples 14 to 17) The aqueous phase in the emulsion was converted from a 0.1 to 2 mol / L aqueous solution of aluminum nitrate to a 0.1 to 2 mol / L aqueous solution of aluminum nitrate and magnesium nitrate (mixing ratio: mol Mg / Al ratio
= 1/99), and Mg-containing alumina particles were synthesized under the same conditions as in Example 5. The synthetic powder was hollow particles having a very thin crust (thickness of the crust: about 12 nm). Among the obtained synthetic powders, those not subjected to water treatment were used as Example 14.

The remaining synthetic powder was subjected to the following water treatment to obtain Examples 15-17. That is, as Example 15, the synthetic powder obtained in Example 14 was treated with deionized water in the same manner as in Example 6. Example 1
As Example 6, the synthetic powder obtained in Example 14 was used in Example 7
Water treatment was carried out using a 1 mol / L nitric acid aqueous solution in the same manner as described above.

In Example 17, the synthetic powder obtained in Example 14 was treated with water using a 1 mol / L aqueous ammonia solution as in Example 8. With respect to the powders measured in the above Examples 5 to 17, specific surface areas of particles per 1 g of weight were measured, and the results are shown in Table 1.

[0044]

[Table 1] As shown in Table 1, Examples 5, 10, and 14 showed the specific surface area of the powder before water treatment, and was 45 to 50 (m ² / g).
Example 6-9, Example 11-13, and Example 15-17
The specific surface area of the powder after water treatment was shown.
It was 30~253 (m ² / g). Thus, it can be seen that the specific surface area of the powder after the water treatment has been dramatically improved (about 4 to 5 times) as compared with the specific surface area of the powder before the water treatment.

Examples 6 to 9, Examples 11 to 13, and Example 1
When the powder of No. 5-17 was observed by SEM, the powder composition and the degree of treatment differed depending on the conditions of water treatment.
Collapse of the surface structure (unevenness or porous form) was observed. Further, when the particles are subjected to water treatment using a mixed solution of water and alcohol as in Example 9, since the chance of direct contact between the particles and water is small, the collapse of the surface structure of the particles is small. , Compared to treatment with water only,
It was found that the increase in the specific surface area of the particles was small. This means that the surface structure is controlled by changing the mixing ratio of water and alcohol, and an arbitrary specific surface area can be obtained between the untreated product and the water-treated product. Further, although the cause is not clear, the specific surface area was large in the order of the aqueous ammonia treated product> the deionized water treated product> the nitric acid aqueous treated product in the range of the examples. This means that the specific surface area can be controlled by the pH of the solution used for the water treatment.

(Examples 18 to 21) The alumina powder synthesized in Example 5 was subjected to a heat treatment for 4 hours in the air at a temperature of 700 to 1000 ° C using an electric furnace. The powder after the heat treatment was water-treated using deionized water, and the specific surface area of the particles per 1 g of the weight was measured. Table 2 shows the measured specific surface areas. The heat treatment temperature in each example was 700 ° C. in Example 18, and 800 ° C. in Example 19.
° C, 900 ° C in Example 20, and 1000 ° C in Example 21.
° C.

[0047]

[Table 2] As can be seen from Table 2, it can be seen that the specific surface area of any of the powders after the heat treatment is improved by the water treatment. In addition, the specific surface area of the powder after water treatment decreases as the heat treatment temperature increases. When the powder of Example 18-21 was observed by SEM, as in Example 6, the structure of the particle surface was disrupted, although the degree varied depending on the heat treatment conditions.

However, as the heat treatment temperature was increased, the collapse of the structure of the particle surface became smaller. This is considered to be because the oxidation reaction partially proceeds by the heat treatment, the hydroxyl groups, undecomposed metal salts, and the like remaining on the crystallite surface are reduced, and the surface structure is less likely to collapse. This result means that the surface structure can be controlled also by heat treatment after synthesis, and any arbitrary specific surface area can be obtained between the untreated product and the water-treated product.

(Supplementary Note) The following technical idea can be understood from the above description.・ Has a shell that partitions the hollow chamber, and the thickness of the shell is 20 nm
A catalyst carrier formed of the following hollow oxide powder particles. According to this catalyst carrier, it is advantageous for weight reduction while securing the specific surface area of the particles.

[0050]

According to the hollow oxide powder particles of the present invention, the thickness of the shell is not more than 20 nm, which is advantageous for increasing the specific surface area while reducing the weight. Furthermore, the hollow oxide powder particles according to the present invention have elasticity as compared with the case where the thickness of the crust is large.

[Brief description of the drawings]

FIG. 1 shows a low magnification T of alumina particles synthesized in Example 1.
3 shows an EM image.

FIG. 2 shows a high-magnification T of the alumina particles synthesized in Example 1.
3 shows an EM image.

FIG. 3 shows a TEM image of the spinel powder synthesized in Example 2.

FIG. 4 is an SEM photograph showing the surface structure of the hollow oxide powder particles obtained in Example 6 where water treatment was performed.

FIG. 5 is an SEM photograph showing the surface structure of the hollow oxide powder particles obtained in Example 5 without performing water treatment.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 14, 1999 (1999.7.1)
4)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2

[Procedure amendment 3]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3

[Procedure amendment 4]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

[Procedure amendment 5]

[Document name to be amended] Drawing

[Correction target item name] Fig. 5

[Correction method] Change

[Correction contents]

FIG. 5

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B01J 13/04 B01J 32/00 32/00 13/02 A (72) Inventor Nobuo Kamiya Aichi, Aichi 4F005 AA01 AB05 AB13 BA20 BB06 DA12Z DA14Y DC01W EA06 4G042 DA01 DA02 DD13 4G047 CA02 CC03 CD03 CD04 4G069 AA01 BA01A BA01B04B04A BB06A BB06B BC10A BC10B BC16A BC16B BC40A BC40B BC50A BC50B BC66A BC66B EA02X EA02Y EA04X EA04Y EB03 EB06 EB18X EB18Y 4G076 AA02 AA18 CA03 CA06 CA26 CA30 CA40 DA01

Claims (5)

[Claims] 1. Hollow oxide powder particles having a shell defining a hollow chamber, wherein the shell has a thickness of 20 nm or less. 2. The hollow oxide powder particles according to claim 1, wherein the average diameter of the hollow oxide powder particles is 50 nm to 5 μm. 3. The hollow oxide powder particles according to claim 1, wherein the hollow oxide powder particles are substantially spherical. 4. A hollow according to claim 1, wherein a main component of the shell is at least one of alumina, spinel, iron oxide, yttrium oxide and titanium oxide. Oxide powder particles. 5. The hollow oxide powder particles according to claim 1, wherein said crust has fine irregularities.