JP2013071886A - Hollow granular particle and method for manufacturing the same, and gas treatment device comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide hollow granular particles having a large effective specific surface area in the spherical particles of the hollow structure, a high catalytic function when they are used as a catalyst, high mechanical durability, and further capable of performing the detoxification of various materials included in an exhaust gas exhausted from an internal combustion engine or the like and efficient reaction to organic gas of propylene or the like, to provide a manufacturing method therefor, and to provide a gas treatment device comprising the particles.SOLUTION: The hollow granular particle is configured to include secondary hollow particles 4 having a particle diameter of ≥0.2 and ≤20 μm, the particle 4 being produced by aggregating primary particles 2 in a shelly shape, the particle 1 being produced by further aggregating the particles 4 in a shelly shape and having a particle diameter of ≥3 and ≤500 μm. The thickness tof shelly part of this hollow granular particle 1 is ≥1/4 and ≤2/3 of its particle radius r.

Description

  The present invention relates to hollow granular particles, a method for producing the same, and a gas processing device including the same, and more particularly, by controlling the pore diameter and porosity of hollow spherical particles to a suitable range, thereby providing a gas processing device. That is, an exhaust gas purification device for treating and purifying various substances contained in exhaust gas discharged from an internal combustion engine, for example, a filter that efficiently collects and removes particulate matter (PM) generated from a diesel engine or the like Reaction for exhaust gas purification to treat carbon monoxide (CO) and hydrocarbon (HC) generated from the body, gasoline engines, etc., or to reduce nitrogen oxides (NOx), or to treat various gases Hollow granular particles suitable for use as an apparatus, for example, an oxidation catalyst for oxidative decomposition of organic gas such as propylene or a reduction catalyst for hydrogenation, and its production method And to a gas treatment apparatus having the same.

In general, a composite used as a catalyst particle, a catalyst particle carrier, a filter body, or the like (hereinafter sometimes referred to as “catalyst particles, etc.”) constituting an exhaust gas purification device or a gas reaction device which is a gas treatment device. The oxide fine particles are obtained by a coprecipitation method.
Here, in order to increase the contact frequency between exhaust gas discharged from an internal combustion engine or the like, or various gases for processing (hereinafter, sometimes referred to as “processing gas or the like”) and catalyst particles, etc., the catalyst When an exhaust gas purification device or a gas treatment device is configured by directly using fine primary particles as particles, etc., the gas diffusion coefficient of the space is small due to the small pore diameter, and especially when used as a column, the permeation pressure is low. As a result, the space velocity becomes high and a sufficient space velocity cannot be obtained, resulting in a decrease in processing capacity.

On the other hand, when a large number of primary particles are irregularly agglomerated into secondary particles, the primary particles present on the surface of the secondary particles are in sufficient contact with the exhaust gas, but the primary particles buried inside are the exhaust gas. There was a problem that the catalyst function as a whole of the secondary particles could not be satisfactorily contacted and the catalyst function as the whole secondary particles was lowered.
Further, when the secondary particles are exposed to a high temperature, there is a problem that a relatively small specific surface area is originally further reduced. The reason is considered to be that the primary particles constituting the secondary particles are solid particles, so that the primary particles are easily sintered with each other, and the obtained sintered body has an extremely small specific surface area.

  Therefore, a catalyst layer containing a metal composite oxide, alumina, and a catalyst metal made of rhodium is formed on the catalyst support, and at least a part of the metal composite oxide is a hollow shell composed of primary particles. And an exhaust gas purifying catalyst that is used as a catalyst in at least one of its fragments has been proposed (see Patent Document 1).

  Further, the primary particles of the metal composite oxide having a particle size of 3 to 15 nm are aggregated to form an aggregate of secondary particles having a particle size of 30 to 100 nm, and the porous composite oxidation having mesopores between the secondary particles An exhaust gas purification catalyst made of a material has been proposed (see Patent Document 2). This exhaust gas-purifying catalyst forms primary particles of a composite oxide precursor from a hydroxide by a hydrolysis method or a neutralization method, and then agglomerates the secondary particles while maintaining a sufficient distance between the primary particles. It is produced by forming particles and further aggregating the secondary particles. In this method, in order to form sufficiently large pores between the secondary particles during hydrolysis, the volume of the organic phase outside the reverse micelle is set to the volume of the aqueous phase in the reverse micelle and the volume of the surfactant. Is getting bigger.

JP 2005-334791 A JP 2004-345890 A

However, in the exhaust gas purifying catalyst described in Patent Document 1 described above, the hollow shell has a substantially spherical shape with a diameter of 0.05 μm or more and 3.0 μm or less, and the thickness of the shell wall is 50 nm or less. Therefore, the number of primary particles existing in the thickness direction of the shell wall is suppressed to about 10 or less, and therefore the volume of the shell relative to the volume of the hollow particles is small. Therefore, there is a problem that the catalyst capacity per unit volume is lowered.
In addition, the mechanical strength of the hollow shell is weak, and therefore the mechanical durability is low, and the catalyst layer composed of at least one of the hollow shell and its fragments tends to be uneven.

  On the other hand, in the exhaust gas purifying catalyst described in Patent Document 2 described above, since the produced primary particles are precursors of complex oxides containing a large amount of hydroxyl groups, pores having sufficiently large pores between the secondary particles during hydrolysis. Even if the dehydration reaction between the precursors does not occur, the reverse micelle shape hardly remains, and further, due to the shrinkage of the particle volume in the dehydration condensation and the thermal history for crystallization of the composite particles, There was a problem that it was difficult to control the air gap. Further, there is a problem that secondary particles are likely to be joined to each other, and a post-treatment process such as pulverization and classification for refining the joined secondary particles is required.

  The present invention has been made in order to solve the above-mentioned problems, and has a large effective specific surface area in a spherical spherical particle and has a sufficient space velocity, so that it can be used as a catalyst. High function and high mechanical durability. Furthermore, various substances contained in exhaust gas discharged from an internal combustion engine, such as particulate matter (PM), carbon monoxide (CO), hydrocarbon ( HC), hollow granular particles capable of efficiently carrying out reactions such as detoxification treatment such as nitrogen oxide (NOx) and various gases such as oxidative decomposition and hydrogenation of organic gases such as propylene, and a method for producing the same It is another object of the present invention to provide a gas processing apparatus including the same.

  As a result of intensive studies in order to solve the above problems, the present inventors combined primary particles in a shell shape to form hollow secondary particles having a particle diameter of 0.2 μm or more and 20 μm or less. The secondary particles are further combined in a shell shape to form hollow granular particles having a particle diameter of 3 μm or more and 500 μm or less. Further, the thickness of the shell-shaped portion of the hollow granular particles is set to When the radius is ¼ or more and 2/3 or less, the effective specific surface area of the hollow spherical particles is large, and having a sufficient space velocity, the catalytic function when used as a catalyst is high, Moreover, it is found that the mechanical durability is high, and furthermore, the detoxification treatment of various substances contained in the exhaust gas discharged from the internal combustion engine or the like, and the reaction to an organic gas such as propylene can be performed efficiently. The present invention This has led to the formation.

  That is, the hollow granular particles of the present invention are hollow secondary particles having a particle diameter of 0.2 μm or more and 20 μm or less formed by bonding primary particles in a shell shape, and the hollow secondary particles are further bonded in a shell shape. The hollow granular particles having a particle diameter of 3 μm or more and 500 μm or less, and the thickness of the shell-shaped portion of the hollow granular particles is not less than 1/4 of the particle radius of the hollow granular particles and 2/3 It is characterized by the following.

The thickness of the shell-shaped portion of the hollow secondary particle is preferably not less than 1/4 and not more than 2/3 of the particle radius of the hollow secondary particle.
The average particle diameter of the primary particles is preferably 0.003 μm or more and 5 μm or less.
The primary particles are present as an oxide, carbide or nitride containing one or more elements selected from Group 3 to 14 elements excluding carbon, or as a composite containing two or more kinds. It is preferable.
It is preferable that metal fine particles adhere to the surface of the primary particles.

  In the method for producing hollow granular particles of the present invention, a primary particle dispersion obtained by dispersing primary particles in a dispersion medium together with a first organic polymer is spray-dried and then fired to form primary particles in a shell shape. A secondary particle dispersion is obtained by forming hollow secondary particles having a particle diameter of 0.2 μm or more and 20 μm or less, and then dispersing the hollow secondary particles together with a second organic polymer in a dispersion medium. It is spray-dried and then fired to form hollow granular particles having a particle diameter of 3 μm or more and 500 μm or less formed by combining hollow secondary particles in a shell shape.

  The gas processing apparatus of the present invention is characterized by comprising the hollow granular particles of the present invention.

According to the hollow granular particles of the present invention, hollow secondary particles having a particle diameter of 0.2 μm or more and 20 μm or less formed by combining primary particles in a shell shape are further combined in a shell shape. The hollow granular particles having a particle diameter of 3 μm or more and 500 μm or less are formed, and the thickness of the shell-shaped portion of the hollow granular particles is ¼ or more and 2/3 or less of the particle radius of the hollow granular particles. As a result, the effective specific surface area of the hollow structure spherical particles can be increased, and a sufficient space velocity can be obtained. Therefore, the catalyst function when this hollow granular particle is used as a catalyst can be enhanced.
Further, since the hollow granular particles have a high catalytic function and a high mechanical durability, the detoxification treatment of various substances contained in the exhaust gas discharged from an internal combustion engine or the like, and an organic matter such as propylene Reaction to gas can be performed efficiently over a long period of time.

  According to the method for producing hollow granular particles of the present invention, a primary particle dispersion obtained by dispersing primary particles in a dispersion medium together with a first organic polymer is spray-dried, and then fired to shell the primary particles. Secondary particle dispersion in which hollow secondary particles having a particle diameter of 0.2 μm or more and 20 μm or less formed by bonding in a shape are dispersed, and then the hollow secondary particles are dispersed in a dispersion medium together with a second organic polymer. Since the liquid is spray-dried and then fired, the effective specific surface area can be increased, and a sufficient space velocity can be provided, so that the catalytic function when used as a catalyst can be enhanced, Hollow granular particles having a high mechanical durability and a particle size of 3 μm or more and 500 μm or less can be easily produced.

  According to the gas treatment device of the present invention, since the hollow granular particles of the present invention are provided, the detoxification treatment of various substances contained in the exhaust gas discharged from an internal combustion engine or the like, and the reaction to an organic gas such as propylene are performed. It can be carried out efficiently over a long period of time.

It is a schematic diagram which shows the hollow granular particle of one Embodiment of this invention. It is a schematic diagram which shows the gas flow-type catalyst reaction apparatus used for evaluation of catalyst performance.

The form for implementing the hollow granular particle of this invention, its manufacturing method, and the gas processing apparatus provided with the same is demonstrated.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[Hollow granular particles]
FIG. 1 is a schematic view showing a hollow granular particle according to an embodiment of the present invention. The hollow granular particle 1 is a particle having primary particles 2 bonded in a shell shape and having a substantially spherical void 3 therein. The hollow secondary particles 4 have a diameter of 0.2 μm or more and 20 μm or less, and the hollow secondary particles 4 are bonded in a shell shape and have a substantially spherical void 5 inside. The particle diameter is 3 μm or more and 500 μm. The following hollow particles are used.
That is, the hollow granular particles 1 and the hollow secondary particles 4 have a property as a self-similar shape.

Here, as the primary particles 2, only one kind or two kinds or more of oxides, carbides or nitrides containing one kind or two or more kinds of elements selected from Group 3 to 14 elements excluding carbon are present. It is preferably present as a composite.
Examples thereof include oxides or composite oxides such as zirconium, aluminum, silicon, titanium, cerium, tungsten, calcium, and iron, carbides such as silicon, zirconium, and boron, and nitrides such as silicon, aluminum, and vanadium. These may be used alone or in a combination of two or more. Further, a composite composition such as oxynitride may be used.

Among these, when using the hollow granular particles of the present embodiment (including the case where a catalyst metal described later is added) as an oxidation catalyst, a substance having an oxygen storage property as the hollow granular particles themselves, for example, Oxides or composite oxides such as cerium oxide (CeO ₂ ), cerium oxide-zirconium oxide (CeO ₂ —ZrO ₂ ), mayenite (Ca ₁₂ Al ₁₄ O ₃₃ ), calcium ferrite (Ca ₂ Fe ₂ O ₅ ), etc. More preferably, it is used.

  In addition, when the hollow granular particles of this embodiment (including the case where a catalyst metal described later is added) are used as a reduction catalyst, zirconium, aluminum, silicon that does not have an oxygen releasing ability under the use environment. More preferably, oxides such as titanium and tungsten, carbides such as silicon, zirconium and boron, and nitrides such as silicon, aluminum and vanadium are used.

The primary particles 2 may have metal fine particles, metal compounds, inorganic fine particles such as silicon, or compounds thereof attached to the surfaces thereof. The metal fine particles mainly have one or both of the following effects.
As the first effect, the provision of catalyst characteristics can be given. Among these, examples of the material having a reduction catalytic action include noble metals, nickel, copper-chromium oxide and the like, and examples of the noble metals include platinum, palladium, rhodium, ruthenium, and these metals or metal compounds. May be used alone or in combination of two or more. In addition, as described above, these metals and metal compounds are often combined with primary particles that do not have oxygen release ability under the usage environment. For example, as in the case of a three-way catalyst in an exhaust purification device, oxygen storage properties It may be combined with primary particles made of a material having
Moreover, platinum, palladium, rhodium etc. can be mentioned as a material which has an oxidation catalytic action.

The particle diameter of the metal fine particles or metal compound fine particles is preferably 30 nm or less, more preferably 10 nm or less.
Here, the reason why the particle diameter of the metal fine particles or metal compound fine particles is preferably 30 nm or less is that the surface activity is exhibited by increasing the ratio of free atoms in the particles.

As the second effect, it is possible to obtain hollow granular particles 1 having high compressive strength by increasing the binding force between the primary particles 2 and the hollow secondary particles 4. Examples of the material having this function include metal materials such as aluminum, zirconium, and titanium, and semimetal materials such as silicon. These metal materials and metalloid materials, or fine particles of metal compounds containing these materials It is only necessary that the fine particles containing one or two or more are attached.
The fine particles of these metal materials, metalloid materials, or metal compounds containing these materials are attached to the surface of the primary particles, so that when the primary particles 2 are fired to form the hollow secondary particles 4, When the secondary particles 4 are fired to form the hollow granular particles 1, these fine particles are partially melted to act as a binder or as a sintering aid, so that hollow granules having a high compressive strength can be obtained. Shaped particles 1 can be obtained.

The specific surface area of the primary particles 2 is preferably 1 m ² / g or more and 1500 m ² / g or less, more preferably 5 m ² / g or more and 1000 m ² / g or less, further preferably 10 m ² / g or more and 500 m. ² / g or less.
Here, the reason why the specific surface area of the primary particles 2 is 1 m ² / g or more and 1500 m ² / g or less is that the catalyst in the hollow granular particles formed using the primary particles when the specific surface area is less than 1 m ² / g. This is because the reaction rate is delayed because the action is reduced, and on the other hand, if the specific surface area exceeds 1500 m ² / g, the heat resistance of the hollow granular particles formed using the primary particles is lowered.

The average particle diameter of the primary particles 2 is preferably 0.003 μm or more and 5 μm or less, more preferably 0.01 μm or more and 1 μm or less, and further preferably 0.02 μm or more and 0.5 μm or less.
Here, the reason why the average particle size of the primary particles 2 is set to 0.003 μm or more and 5 μm or less is that the heat resistance is lowered when the average particle size of the primary particles 2 is less than 0.003 μm, while the average particles This is because when the diameter exceeds 1 μm, the reaction rate is delayed because the action as a catalyst is reduced.

  The reason why the particle diameter of the hollow secondary particles 4 is 0.2 μm or more and 20 μm or less is that this range is a suitable range for obtaining hollow secondary particles having a substantially spherical void inside. Here, when the particle diameter is less than 0.2 μm, solid secondary particles are likely to be obtained, and it is difficult to obtain hollow secondary particles having a large specific surface area having a substantially spherical void inside. On the other hand, when the particle diameter exceeds 20 μm, the particles become coarse and it is difficult to obtain hollow secondary particles having a substantially spherical void inside.

The thickness t ₁ of the shell-shaped portion of the hollow secondary particle 4 is preferably not less than 1/4 and not more than 2/3 of the particle radius r ₁ of the hollow secondary particle 4.
Here, the reason why the thickness t ₁ of the shell-shaped portion is ¼ or more and 2/3 or less of the particle radius r ₁ is that the shell occupies the volume of the entire hollow secondary particle when it is less than ¼. This is because the volume of the portion is reduced, so that the effectiveness of the catalyst is lowered and the mechanical strength of the hollow secondary particles is lowered. On the other hand, when the volume is 2/3 or more, it is effectively the same as the solid particles. This is because the gas diffusion coefficient is small, and when used as a column, the permeation pressure becomes high, a sufficient space velocity cannot be obtained, and the efficiency with respect to the catalyst weight decreases.

In addition, the specific surface area of the hollow granular particle 1 of the present embodiment is preferably ² m ² / g or more and 1300 m ² / g or less, more preferably 5 m ² / g or more and 1000 m ² / g or less, and still more preferably. Is 10 m ² / g or more and 500 m ² / g or less.
Here, the reason why the specific surface area of the hollow granular particles 1 is 2 m ² / g or more and 1300 m ² / g or less is that when the specific surface area is less than 2 m ² / g, the catalytic action of the hollow granular particles is reduced. This is because the reaction rate is delayed, and when the specific surface area exceeds 1300 m ² / g, the heat resistance of the hollow granular particles is lowered.

  Here, the hollow granular particles 1 have a particle diameter of 3 μm or more and 500 μm or less, and this range is a hollow secondary particle having a substantially spherical void 3 inside and having a particle diameter of 0.2 μm or more and 20 μm or less. This is because it is a value suitable for obtaining hollow granular particles having a substantially spherical void 5 inside based on 4. Here, when the particle diameter is less than 3 μm, it is difficult to obtain the hollow granular particles 1 having the desired shape and characteristics even if the hollow secondary particles 4 aggregate. On the other hand, when the particle diameter exceeds 500 μm, the particles are coarsened, and it is difficult to obtain hollow particles having a substantially spherical void inside.

The thickness t ₂ of the shell-shaped portion of the hollow granular particle 1 of the present embodiment is preferably not less than 1/4 and not more than 2/3 of the particle radius r ₂ of the hollow granular particle 1.
Here, the reason why the thickness t ₂ of the shell-shaped portion is set to ¼ or more and 2/3 or less of the particle radius r ₂ is less than ¼, the shell occupying the volume of the entire hollow granular particle This is because the volume of the portion is reduced, and thus the effectiveness of the catalyst is reduced, and the mechanical strength of the hollow granular particles is reduced. Similarly, the gas diffusion coefficient is small, and when used as a column, the permeation pressure becomes high, a sufficient space velocity cannot be obtained, and the efficiency in terms of catalyst weight decreases.

The compressive strength of the hollow granular particles 1 is preferably 0.5 g / mm ² or more and 1000 g / mm ² or less, more preferably 5 g / mm ² or more and 500 g / mm ² or less.
Here, the reason why the compression strength of the hollow granular particles 1 is 0.5 g / mm ² or more and 1000 g / mm ² or less is that the compression strength of the hollow granular particles 1 is less than 0.5 g / mm ² , This is because the packing pressure in the column container is limited, making it difficult to handle. On the other hand, when the compressive strength exceeds 1000 g / mm ² , the volume of the joint between primary particles increases and the pore volume between the particles decreases. This is because it becomes difficult to secure a gas diffusion path and the frequency of contact with the reaction gas decreases.

[Method for producing hollow granular particles]
In the method for producing hollow granular particles of the present embodiment, a primary particle dispersion obtained by dispersing primary particles in a dispersion medium together with a first organic polymer is spray-dried and then fired to form primary particles in a shell shape. Secondary particle dispersion liquid in which hollow secondary particles having a particle diameter of 0.2 μm or more and 20 μm or less formed by bonding to the same are dispersed in a dispersion medium together with the second organic polymer. By spray-drying and then firing, hollow granular particles having a particle diameter of 3 μm or more and 500 μm or less formed by combining the hollow secondary particles in a shell shape can be obtained.

Here, the method for forming the hollow secondary particles or the hollow granular particles is not particularly limited, but a spray drying method is preferable.
In this spray drying method, fine droplets containing sprayed dispersed particles are rapidly dried to form an outer shell made of dispersed particles on the outer periphery of the droplets, and then the internal dispersion medium is vaporized and removed. Therefore, hollow substantially spherical aggregated particles can be easily obtained.
In addition, various characteristics of the dispersion (for example, dispersed particle amount (concentration), dispersed particle diameter, type and amount of dispersion medium, type and addition amount of organic polymer, viscosity of dispersion liquid, etc.), spray conditions (for example, spray rate) And droplet size, etc.) and by controlling various characteristics and conditions of drying conditions (for example, drying temperature, drying air volume, etc.), the size and shell thickness of the resulting hollow agglomerated particles can be easily controlled. It is.

  When strictly controlling the size, shell thickness, etc. of the hollow secondary particles and hollow granular particles, for example, the resin particles serving as the core of the aggregated particles coexist in the dispersion, and the dispersion is sprayed. After drying, an aggregated particle layer made of dispersed particles is formed on the surface of the resin particles, and then a method of burning or volatilizing and removing the resin particles at the time of firing may be used.

Next, the manufacturing method of the hollow granular particle of this embodiment is demonstrated in detail.
"Preparation of primary particle dispersion"
First, primary particles are put into a dispersion medium to be dispersed, and then the first organic polymer is added to the dispersion and mixed and stirred to obtain a primary particle dispersion.
As already described, the primary particles are oxides, carbides or nitrides containing one or more elements selected from Group 3-14 elements excluding carbon, or a composite containing two or more elements. The specific surface area may be 1 m ² / g or more and 1500 m ² / g or less, and the average particle diameter may be 0.003 μm or more and 5 μm or less. For example, zirconium, aluminum, silicon, titanium, cerium, tungsten And oxides or composite oxides such as calcium and iron, carbides such as silicon, zirconium and boron, and nitrides such as silicon, aluminum and vanadium.

In addition, metal fine particles, metal compounds, inorganic fine particles such as silicon, or compounds thereof may adhere to the surfaces of the primary particles in order to impart catalyst characteristics and increase the binding force between the primary particles. As a method for attaching metal fine particles, metal compounds, inorganic fine particles and compounds thereof to the surface of the primary particles, known methods can be used. For example, when attaching metal fine particles, the primary particles are used as raw materials for metal fine particles. After being immersed in an aqueous solution containing a metal salt to be dried, the metal salt is adhered to the surface of the primary particles, the primary particles are heat-treated in a reducing atmosphere to reduce the metal salt, and metal fine particles are formed on the surface of the primary particles. A method of generating can be exemplified.
Alternatively, a metal salt as a raw material for the metal fine particles may be added to the dispersion of primary particles, and the metal salt may be attached to the surfaces of the primary particles (hollow aggregates) by spray drying, and then reduced.

  As the dispersion medium, water and an organic solvent can be used. Examples of the organic solvent include monohydric alcohols such as methanol, ethanol, 2-propanol, butanol, and octanol and modified products thereof; alcohols belonging to monocyclic monoterpenes such as α-terpineol; carbs such as butyl carbitol. Tolls; Esters such as ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, butyl carbitol acetate, γ-butyrolactone; diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), Ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monomethyl ether, diethyl Ethers such as lenglycol monoethyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone and cyclohexanone; aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; dimethylformamide, N, N-dimethylacetamide, Amides such as N-methylpyrrolidone are preferably used, and one or more of these solvents can be used.

As means for introducing and dispersing the primary particles in a dispersion medium, known dispersion means and apparatuses can be used. As these apparatuses, a sand mill disperser, an ultrasonic homogenizer, a bead mill, an ultra high pressure pulverizer and the like are preferably used.
During the dispersion, additives such as a surface treatment agent and a dispersant may be added within a range that does not hinder the formation of hollow agglomerated particles during spray drying.
Here, the ratio of the primary particles in the dispersion may be determined in consideration of various characteristics of the above-mentioned dispersion, spraying conditions, drying conditions, and the like in accordance with the desired size and shell thickness of the hollow agglomerated particles. As an example of the ratio of this primary particle, it is preferable that it is the range of 1 mass% or more and 80 mass% or less, for example, More preferably, it is 5 mass% or more and 70 mass% or less, More preferably, it is 40 mass% or more and 60% by mass or less.

Next, the first organic polymer is added to the dispersion and mixed and stirred to obtain a primary particle dispersion.
The first organic polymer is not particularly limited as long as it dissolves in a dispersion medium, binds primary particles after spray drying, and is removed by volatilization, decomposition, combustion, or the like in a subsequent firing step. Although there is no limitation, when using polar solvents, such as water and alcohol, as a dispersion medium, polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), etc. are used suitably.

The amount of the first organic polymer added to the dispersion is preferably 0.1% by mass or more and 70% by mass or less, more preferably 1% by mass with respect to the total mass of the primary particles that are solids in the dispersion. It is not less than 50% by mass and not more than 50% by mass, more preferably not less than 2% by mass and not more than 10% by mass, and most preferably not less than 2% by mass and not more than 5% by mass.
Here, the reason why the addition amount of the first organic polymer is 0.1% by mass or more and 70% by mass or less is that the addition amount of the first organic polymer is less than 0.1% by mass. The amount of the first organic polymer added to the primary particles is not preferable because the amount is too small relative to the primary particles, and the effect as a binder cannot be exhibited. In addition to excessively increasing the viscosity of the above dispersion, spraying may be difficult, and excessive removal of the organic polymer during subsequent baking is required, and the shrinkage is large. Therefore, it is not preferable because hollow secondary particles are difficult to form.

"Production of hollow secondary particles"
Next, this primary particle dispersion is spray-dried.
As the spray drying means, a spray dryer such as a spray dryer is preferably used.
By spray-drying this primary particle dispersion, the inner dispersion medium is vaporized and removed after the outer shell of the primary particles is formed on the outer periphery of the droplets, so that these primary particles are arranged in a shell shape. A substantially spherical hollow agglomerated particle, that is, a spherical secondary agglomerated particle having a particle diameter of 0.2 μm or more and 20 μm or less formed by agglomerating primary particles in a shell shape is formed.

  The spray drying conditions are such that the primary particle dispersion liquid spray amount, droplet size, drying temperature, drying air volume so that hollow secondary particles of the desired shape and size can be obtained from the primary particle dispersion liquid prepared above. Etc. are adjusted appropriately. That is, various conditions such as the type and particle size of primary particles, the amount (concentration) and particle size of dispersed particles in the primary particle dispersion, the type and amount of dispersion medium, the type and addition amount of organic polymer, the viscosity of the dispersion, etc. The spray drying conditions may be determined from the device characteristics of the spray dryer. The spray drying conditions are difficult to show because there are many parameters, they interact with each other, and the device dependency is high. For example, the capacity of the drying chamber is 50 to 100 L, the moisture evaporation In the case of a small spray dryer having an amount of about 2 to 5 kg / hour, in the case of an aqueous dispersion using ceramic particles having an average dispersed particle diameter of several tens of nm to several μm as the primary particle dispersion, A range of 50 mL / min and a drying temperature of 50 to 250 ° C. can be shown.

Next, the obtained spray-dried product (hollow secondary aggregated particles) is fired under an oxidizing atmosphere, a reducing atmosphere, or an inert atmosphere. The firing temperature may be a temperature at which the first organic polymer is removed by volatilization, decomposition, combustion, etc., and the primary particles are partially sintered, and is selected from a temperature range of 300 ° C. or more and 1500 ° C. or less. It is preferable to do.
In addition, when fine particles, metal compounds, or inorganic fine particles such as silicon or compounds for enhancing the binding force between the primary particles are attached to the surface of the primary particles, the primary particles are bonded to each other by these substances. What is necessary is just to sinter primary particles.

  As described above, hollow secondary particles having a particle diameter of 0.2 μm or more and 20 μm or less formed by combining primary particles in a shell shape, and the thickness of the shell portion is the particle radius of the secondary particles. The spherical hollow secondary particles having a mechanical strength of 1/4 or more and 2/3 or less of the above are obtained.

"Production of hollow granular particles"
Next, the same operation as the above primary particles is performed again on the hollow secondary particles.
That is, the hollow secondary particles are charged and dispersed in a dispersion medium so that the content is 1% by mass or more and 80% by mass or less. As the dispersing means, since it is necessary to uniformly disperse the hollow secondary particles without destroying them, a propeller stirrer, an ultrasonic disperser, a homogenizer disperser, or the like is preferably used.
The more preferable range of the ratio between the hollow secondary particles and the dispersion medium and other conditions are the same as in the case of the primary particles described above, and the dispersion medium is the same as the dispersion medium described above. Is omitted.

Next, the second organic polymer is added to the dispersion and mixed and stirred to obtain a secondary particle dispersion.
Since the conditions required for the second organic polymer are the same as those for the first organic polymer, they may be the same as the first organic polymer described above, and if the conditions are satisfied, the first organic polymer described above is satisfied. However, considering the uniformity of the quality of the obtained particles, it is preferably the same as the first organic polymer, and in particular, polyvinyl alcohol (PVA) and polyethylene glycol (PEG) are preferred. .

Next, this secondary particle dispersion is spray-dried in the same manner as the primary particle dispersion described above.
By spray-drying this secondary particle dispersion, hollow agglomerated particles in which spherical hollow secondary particles are arranged in a shell shape, that is, spherical hollow secondary particles are agglomerated in a shell shape to form a substantially spherical void inside. It becomes a hollow tertiary aggregate particle having a particle diameter of 3 μm or more and 500 μm or less.
The spray-drying conditions are appropriately adjusted such as the spray amount of the secondary particle dispersion, the size of the droplets, the drying temperature, and the amount of drying air so that hollow tertiary aggregate particles having a desired shape can be obtained. The various conditions and parameters examined here are basically the same as in the case of the primary particles described above, but the spray particles are secondary particles, and the resulting particles are tertiary aggregate particles, which are primary particles and secondary particles, respectively. Compared to the case of primary particles, the spray amount, spray pressure, drying temperature, etc. are increased due to the fact that the particle size is larger and heavier than the particles and there is a possibility that a dispersion medium exists inside the secondary particles. It is normal to set.

  Next, the obtained spray-dried product (hollow tertiary aggregated particles) is fired under an oxidizing atmosphere, a reducing atmosphere, or an inert atmosphere. The firing temperature may be a temperature at which the second organic polymer is removed by volatilization, decomposition, combustion, or the like, and the secondary particles are partially sintered, for example, a temperature of 300 ° C. or more and 1500 ° C. or less. It is preferable to select from a range.

  As described above, the primary particles are combined in a shell shape to form hollow secondary particles having a substantially spherical void inside and having a particle diameter of 0.2 μm or more and 20 μm or less. Further, these hollow secondary particles are formed into a shell shape. The particle diameter is 3 μm or more and 500 μm or less, and the shell-shaped portion has a substantially spherical void inside, and the thickness of the shell-shaped part is ¼ or more and 2/3 or less of the particle radius of the tertiary aggregated particles. Hollow granular particles with excellent mechanical strength can be obtained.

In addition, when attaching fine particles, metal compounds, inorganic fine particles such as silicon, and compounds for imparting catalytic characteristics to the surface of the primary particles, they may be attached at the time of the primary particles as described above. However, an adhesion treatment may be performed on the hollow granular particles thus obtained.
As a method of attaching, a known method can be used. For example, in the case of metal fine particles, the hollow granular particles are immersed in an aqueous solution containing a metal salt as a raw material for the metal fine particles and then dried to adhere the metal salt, and the hollow granular particles are heat-treated in a reducing atmosphere. Then, a method of reducing the metal salt to produce fine metal particles can be mentioned. Even in this case, since the primary particles constituting the hollow secondary particles and the hollow secondary particles constituting the hollow granular particles both have voids between the particles, the catalyst properties are imparted. Metal fine particles and the like can be attached not only to the surface of the hollow granular particles but also to the entire surface of the primary particles forming the hollow granular particles.

[Gas treatment equipment]
The gas processing apparatus of this embodiment is an apparatus provided with the hollow granular particles of this embodiment.
As this gas processing apparatus, for example, by using the hollow granular particles, particulate matter (PM) generated from a diesel engine or the like can be efficiently collected and removed, or carbon monoxide generated from a gasoline engine or the like. An exhaust purification device that oxidizes (CO) or hydrocarbon (HC) or reduces nitrogen oxide (NOx) can be used.
Moreover, the gas reaction apparatus which performs the oxidation process of various gas, etc. which use this hollow granular particle as an oxidation catalyst which oxidatively decomposes organic gas, such as propylene, and a reduction catalyst which hydrogenates, etc. are mentioned.

  In this gas processing apparatus, by providing the hollow granular particles of this embodiment, efficient collection and removal of particulate matter (PM), carbon monoxide (CO) and hydrocarbon ( HC) oxidation, nitrogen oxide (NOx) reduction, organic gas oxidative decomposition, reduction catalyst function during hydrogenation, and the like can be performed efficiently over a long period of time.

As described above, according to the hollow granular particles of the present embodiment, the hollow secondary particles 4 having a particle diameter of 0.2 μm or more and 20 μm or less formed by agglomerating the primary particles 2 in a shell shape are used. The secondary particles 4 are further agglomerated into shells to form hollow granular particles 1 having a particle diameter of 3 μm or more and 500 μm or less. The thickness t ₂ of the shell-shaped portion of the hollow granular particles 1 is defined as the hollow granular particles. 1/4 or more and since the 2/3 or less of the particle radius r ₂ of the can to increase the effective specific surface area as spherical particles having a hollow structure, and can have a sufficient space velocity. Therefore, the catalyst function when this hollow granular particle 1 is used as a catalyst can be enhanced.

In addition, the primary particles (fine particles) are not used as they are, but by assembling the particles in multiple stages, the obtained hollow granular particles 1 are three-dimensionally continuous from micropores to mesopores and from mesopores to micropores. A pore distribution can be formed.
Therefore, by using the hollow granular particles 1 for the catalyst layer, a homogeneous, high compressive strength and uniform gas-permeable catalyst layer can be formed by high space velocity, catalytic effect and spherical particles.
In addition, since a three-dimensional pore distribution is formed, particulate matter generated in an internal combustion engine such as a diesel engine can be collected with high efficiency.

  Furthermore, since the hollow granular particles 1 have high catalytic function and high mechanical durability, the detoxification treatment of various substances contained in exhaust gas discharged from an internal combustion engine, propylene, etc. The reaction with respect to the organic gas can be efficiently performed over a long period of time.

According to the method for producing hollow granular particles of this embodiment, the primary particles 2 are dispersed in a dispersion medium together with the first organic polymer to form a primary particle dispersion, and the primary particle dispersion is spray-dried and fired. The hollow secondary particles 4 having a particle diameter of 0.2 μm or more and 20 μm or less formed by bonding the primary particles in a shell shape are dispersed in the dispersion medium together with the second organic polymer. Thus, a secondary particle dispersion is obtained, and the secondary particle dispersion is spray-dried and fired, so that an effective specific surface area can be increased. Moreover, since sufficient space velocity can be given, the catalyst function at the time of using as a catalyst can be improved. Accordingly, the mechanical durability is high, a hollow granular particles 1 thickness t ₂ is less than 1/4 and 2/3 of the particle radius r ₂ parts: and Karajo than 3μm particle size and 500μm Can be easily manufactured.
Further, by using a spray drying method as a granulation process, a stress applied to the particles is small, and a homogeneous particle layer can be formed, so that the hollow granular particles 1 having a three-dimensionally homogeneous property are expressed. be able to.

  According to the gas treatment apparatus of the present embodiment, since the hollow granular particles 1 of the present embodiment are provided, detoxification treatment of various substances contained in exhaust gas discharged from an internal combustion engine or the like, or organic gas such as propylene Can be efficiently performed over a long period of time.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.

"Example 1"
Zirconia (ZrO ₂ ) fine particles containing 20 mol% of cerium oxide (CeO ₂ ) (average primary particle diameter: 20 nm, specific surface area: 52 m ² / g, manufactured by Sumitomo Osaka Cement), 1,000 g, pure water 3,900 g, and dispersion 100 g of the agent W287 (manufactured by Adeka) was put into a bead mill together with 5,000 g of beads having a diameter of 0.1 mm and dispersed at a rotational speed of 2,000 rpm for 8 hours, and then the beads were separated to obtain a dispersion.
When the dispersed particle size of this dispersion was measured with a particle size distribution analyzer LB-550 (manufactured by Horiba, Ltd.), the particle size at a cumulative percentage of 50% (D50) of the particle size distribution was 25 nm.

Next, 100 g of polyvinyl alcohol (PVA: degree of polymerization 500) was dissolved in 3,000 g of this dispersion to obtain a primary particle dispersion.
Subsequently, this primary particle dispersion was spray-dried with a spray dryer to obtain secondary agglomerated particles. As the spray dryer, MDL-050 (manufactured by Fujisaki Electric Co., Ltd.) equipped with a four-fluid nozzle (dispersion x 2, spray air x 2) capable of forming fine droplets is used. 100 ° C., exhaust temperature 48 ° C., supply air volume 0.95 m ² / min, spray air 1: pressure 1 MPaG, flow rate 10 NL / min, spray air 2: pressure 1 MPaG, flow rate 100 NL / min, dispersion 1: flow rate 5 mL / min , Dispersion 2: Flow rate was 5 ml / min.

Next, the secondary agglomerated particles were calcined in the atmosphere at 500 ° C. for 6 hours to obtain secondary particles.
Subsequently, when the specific surface area of this secondary particle was measured using the specific surface area measuring apparatus (BET meter), it was 50 m < ² > / g.
Further, when the dispersed particle size of the dispersion obtained by ultrasonically dispersing the secondary particles in water was measured with a particle size distribution measuring device LA-300 (manufactured by Horiba Ltd.), the dispersed particles at a cumulative percentage of 50% (D50). The diameter was 1.3 μm.

Further, when the particle diameter of the secondary particles was measured using a scanning electron microscope (SEM), spherical particles having a particle diameter of 1.5 μm were confirmed.
Furthermore, when a cross section obtained by breaking the secondary particles was observed using a scanning electron microscope, it was confirmed that the inside had a substantially spherical void. Further, the thickness of the shell of the secondary particles was measured and found to be 0.4 μm.

Next, 300 g of these secondary particles were put into a PVA aqueous solution in which 30 g of PVA was dissolved in 670 g of pure water, and stirred with a propeller stirrer to obtain a secondary particle dispersion.
When the dispersed particle size of the secondary particle dispersion was measured with a particle size distribution measuring device LB-550 (manufactured by Horiba Ltd.), the dispersed particle size at a cumulative percentage of 50% (D50) of the particle size distribution was 1.5 μm. there were.

Subsequently, this secondary particle dispersion was spray-dried with a spray dryer to obtain tertiary agglomerated particles. The spray dryer uses MDL-050 (Fujisaki Electric Co., Ltd.) equipped with a four-fluid nozzle, and spray drying conditions are an inlet temperature of 200 ° C., an exhaust temperature of 101.1 ° C., a supply air volume of 1.03 m ² / min, and a spray. Air 1: pressure 0.7 MPaG, flow rate 30 NL / min, spraying air 2: pressure 0.7 MPaG, flow rate 30 NL / min, dispersion 1: flow rate 15 mL / min, dispersion 2: flow rate 15 mL / min.

Next, the tertiary agglomerated particles were calcined in the atmosphere at 500 ° C. for 6 hours to obtain granular particles (tertiary particles).
Subsequently, when the specific surface area of this granular particle was measured using the specific surface area measuring apparatus (BET meter), it was 50 m < ² > / g.
Moreover, when the particle diameter of the granular particles was measured using a scanning electron microscope (SEM), spherical particles having a particle diameter of 10 μm were confirmed.
Furthermore, when a cross section obtained by breaking the granular particles was observed using a scanning electron microscope (SEM), it was confirmed that the particles had a substantially spherical void inside. The thickness of the granular particle shell was measured to be 3 μm.

"Example 2"
1,000 g of silicon carbide (SiC) fine particles (average primary particle diameter: 35 nm, specific surface area: 54 m ² / g, manufactured by Sumitomo Osaka Cement), 3,900 g of pure water, and 100 g of dispersant W287 (manufactured by Adeka) Then, it was put into a bead mill together with 5,000 g of beads having a diameter of 0.1 mm and dispersed at a rotational speed of 2,000 rpm for 8 hours, and then the beads were separated to obtain a dispersion.
When the dispersed particle size of this dispersion was measured with a particle size distribution analyzer LB-550 (manufactured by Horiba Ltd.), the particle size at a cumulative percentage of 50% (D50) of the particle size distribution was 42 nm.

Next, 100 g of polyvinyl alcohol (PVA: degree of polymerization 500) was dissolved in 3,000 g of this dispersion to obtain a primary particle dispersion.
Subsequently, this primary particle dispersion was spray-dried with a spray dryer to obtain secondary agglomerated particles. The spray dryer used was MDL-050 (Fujisaki Electric Co., Ltd.) equipped with a 4-fluid nozzle, and spray drying conditions were an inlet temperature of 100 ° C., an exhaust temperature of 46 ° C., an air supply rate of 0.95 m ² / min, and a spray air of 1 : Pressure 1 MPaG, Flow rate 10 NL / min, Spraying air 2: Pressure 1 MPaG, Flow rate 110 NL / min, Dispersion 1: Flow rate 5 mL / min, Dispersion 2: Flow rate 5 mL / min.
Next, the secondary agglomerated particles were calcined in the atmosphere at 500 ° C. for 6 hours to obtain secondary particles.
Subsequently, when the specific surface area of this secondary particle was measured using the specific surface area measuring apparatus (BET meter), it was 54 m < ² > / g.

Further, when the particle diameter of the secondary particles was measured using a scanning electron microscope (SEM), spherical particles having a particle diameter of 1 μm were confirmed.
Furthermore, when a cross section obtained by breaking the secondary particles was observed using a scanning electron microscope (SEM), it was confirmed that the inside had a substantially spherical void. Further, the thickness of the secondary particle shell was measured and found to be 0.3 μm.

Next, 300 g of the secondary particles are put into a PVA aqueous solution in which 30 g of PVA is dissolved in 670 g of pure water, dispersed with an ultrasonic dispersing device, and then stirred with a propeller stirrer to obtain a secondary particle dispersion. It was.
When the dispersed particle size of this secondary particle dispersion was measured with a particle size distribution analyzer LB-550 (manufactured by Horiba Ltd.), the dispersed particle size at a cumulative percentage of 50% (D50) of the particle size distribution was 1.1 μm. there were.

Subsequently, this secondary particle dispersion was spray-dried with a spray dryer to obtain tertiary agglomerated particles. The spray dryer uses MDL-050 (Fujisaki Electric Co., Ltd.) equipped with a four-fluid nozzle, and spray drying conditions are an inlet temperature of 200 ° C., an exhaust temperature of 101.1 ° C., a supply air volume of 1.03 m ² / min, and a spray. Air 1: pressure 0.7 MPaG, flow rate 30 NL / min, spray air 2: pressure 0.7 MPaG, flow rate 30 NL / min, dispersion 1: flow 1515 mL / min, dispersion 2: flow 15 mL / min.
Next, the tertiary agglomerated particles were calcined at 500 ° C. for 6 hours in the air, and then calcined at 1700 ° C. for 1 hour in an argon (Ar) atmosphere to obtain granular particles (tertiary particles).
Subsequently, when the specific surface area of this granular particle was measured using the specific surface area measuring apparatus (BET meter), it was 50 m < ² > / g.

Further, when the particle diameter of the granular particles was measured using a scanning electron microscope (SEM), spherical particles having a particle diameter of 9 μm were confirmed.
Moreover, when the cross section which divided this granular particle | grain was observed using the scanning electron microscope (SEM), it was confirmed that it has a substantially spherical space | gap inside. The thickness of the granular particle shell was measured to be 3 μm.
Further, when the dispersed particle size of the dispersion obtained by ultrasonically dispersing the hollow granular particles in water was measured with a particle size distribution measuring apparatus LA-300 (manufactured by Horiba, Ltd.), the dispersion at a cumulative percentage of 50% (D50). The particle size was 7.2 μm.

  Next, 100 g of the hollow granular particles were dispersed in 900 g of water. Next, a dinitrodiamine platinum aqueous solution was added to and mixed with the dispersion so that platinum was 0.015 mol with respect to 1 mol in terms of silicon carbide of the hollow granular particles. Subsequently, this mixture was evaporated to dryness using an evaporator, crushed, and then reduced at 600 ° C. for 12 hours to obtain hollow granular particles in which platinum adhered to the surface of primary particles constituting the hollow granular particles. Obtained.

"Example 3"
1,000 g of calcium aluminum silicate (Ca ₁₂ Al ₁₀ Si ₄ O ₃₅ ; average primary particle size: 80 nm, specific surface area: 40 m ² / g, manufactured by Sumitomo Osaka Cement), 3,900 g of pure water, and dispersant W287 (ADEKA) 100 g) was put into a bead mill together with 5,000 g of beads having a diameter of 0.1 mm and dispersed at a rotational speed of 2,000 rpm for 8 hours, and then the beads were separated to obtain a dispersion.
When the dispersed particle size of this dispersion was measured with a particle size distribution analyzer LB-550 (manufactured by Horiba, Ltd.), the particle size at a cumulative percentage of particle size distribution of 50% (D50) was 90 nm.

Next, 100 g of polyvinyl alcohol (PVA: degree of polymerization 500) was dissolved in 3,000 g of this dispersion to obtain a primary particle dispersion.
Subsequently, this primary particle dispersion was spray-dried with a spray dryer to obtain secondary agglomerated particles. The spray dryer uses MDL-050 (Fujisaki Electric Co., Ltd.) equipped with a four-fluid nozzle. Spray drying conditions are an inlet temperature of 100 ° C., an exhaust temperature of 52 ° C., a supply air volume of 0.95 m ² / min, and a spray air of 1 : Pressure 1 MPaG, Flow rate 10 NL / min, Spray air 2: Pressure 1 MPaG, Flow rate 60 NL / min, Dispersion 1: Flow rate 55 mL / min, Dispersion 2: Flow rate 55 mL / min.
Next, the secondary agglomerated particles were calcined in the atmosphere at 500 ° C. for 6 hours to obtain secondary particles.
Subsequently, when the specific surface area of this secondary particle was measured using the specific surface area measuring apparatus (BET meter), it was 39 m < ² > / g.

Further, when the particle diameter of the secondary particles was measured using a scanning electron microscope (SEM), spherical particles having a particle diameter of 1.5 μm were confirmed.
Furthermore, when a cross section obtained by breaking the secondary particles was observed using a scanning electron microscope (SEM), it was confirmed that the inside had a substantially spherical void. Further, the thickness of the shell of the secondary particles was measured and found to be 0.4 μm.

Next, 300 g of these secondary particles were put into a PVA aqueous solution in which 30 g of PVA was dissolved in 670 g of pure water, and stirred with a propeller stirrer to obtain a secondary particle dispersion.
When the dispersed particle size of the secondary particle dispersion was measured with a particle size distribution measuring device LB-550 (manufactured by Horiba Ltd.), the dispersed particle size at a cumulative percentage of 50% (D50) of the particle size distribution was 1.8 μm. there were.

Subsequently, this secondary particle dispersion was spray-dried with a spray dryer to obtain tertiary agglomerated particles. The spray dryer used was MDL-050 (Fujisaki Electric Co., Ltd.) equipped with a four-fluid nozzle. Spray drying conditions were an inlet temperature of 200 ° C., an exhaust temperature of 110.6 ° C., an air supply rate of 1.03 m ² / min, and a spray. Air 1: pressure 0.7 MPaG, flow rate 25 NL / min, spray air 2: pressure 0.7 MPaG, flow rate 25 NL / min, dispersion 1: flow 15 mL / min, dispersion 2: flow 15 mL / min.
Next, the tertiary aggregated particles were fired at 800 ° C. for 6 hours in the air to obtain granular particles (tertiary particles).
Subsequently, it was 38 m < ² > / g when the specific surface area of this granular particle was measured using the specific surface area measuring apparatus (BET meter).

Moreover, when the particle diameter of the granular particles was measured using a scanning electron microscope (SEM), spherical particles having a particle diameter of 12 μm were confirmed.
Furthermore, when a cross section obtained by breaking the granular particles was observed using a scanning electron microscope (SEM), it was confirmed that the particles had a substantially spherical void inside. Further, the thickness of the granular particle shell was measured and found to be 4 μm.

“Comparative Example 1”
Prepare zirconia (ZrO ₂ ) fine particles (average primary particle size: 20 nm, specific surface area: 52 m ² / g, manufactured by Sumitomo Osaka Cement Co., Ltd.) containing 20 mol% of cerium oxide (CeO ₂ ). The particles of Example 1 were obtained.

“Comparative Example 2”
Calcium aluminum silicate (Ca ₁₂ Al ₁₀ Si ₄ O ₃₅ ; average primary particle size: 80 nm, specific surface area: 40 m ² / g, manufactured by Sumitomo Osaka Cement Co., Ltd.) was prepared, and the particles of Comparative Example 2 were not particularly granulated. It was.

“Comparative Example 3”
100 g of silicon carbide (SiC) fine particles (average primary particle size: 35 nm, specific surface area: 54 m ² / g, manufactured by Sumitomo Osaka Cement) were put into 900 g of pure water and stirred with a propeller stirrer to obtain a dispersion.
Next, a dinitrodiamine platinum aqueous solution was added to and mixed with this dispersion so that platinum was 0.015 mol with respect to 1 mol of silicon carbide (SiC) fine particles. Next, this mixture was evaporated to dryness and pulverized using an evaporator, and then subjected to reduction treatment at 600 ° C. for 12 hours to obtain particles having platinum adhered to the surface of silicon carbide fine particles.

"Evaluation of catalyst performance"
Catalyst performance was evaluated about each granular particle (catalyst sample) of Examples 1-3 and Comparative Examples 1-3.
FIG. 2 is a schematic diagram showing a gas flow-type catalytic reaction apparatus used for evaluating the catalyst performance, and is an apparatus for examining the catalytic activity of the above sample against propylene oxidation.
This gas flow type catalytic reactor 11 includes a propylene / helium (C ₃ H ₆ / He) mixed gas pipe 12, an oxygen (O ₂ ) gas pipe 13, a helium (He) gas pipe 14, and these A gas mixer 15 for mixing the sample gas, an electric furnace 16, a reaction tube 17 made of quartz glass heated to a predetermined temperature in the electric furnace 16, an FID gas chromatograph 18 for detecting organic gas, and a reaction tube 17 A pressure loss meter 19 and a flow meter 20 provided on the injection side. In addition, this reaction tube 17 can be made into column 17 'by filling a catalyst.

Next, a method for evaluating the catalyst performance of each of the catalyst samples of Examples 1 to 3 and Comparative Examples 1 to 3 using the gas flow type catalytic reactor 11 will be described.
First, each catalyst sample is filled in the reaction tube 17 to produce a column 17 ′. Here, the reaction tube 7 is U-shaped with an inner diameter of 8 mm and a height of about 150 mm, and the six reaction tubes 17 are filled with the catalyst samples of any one of Examples 1 to 3 and Comparative Examples 1 to 3, respectively. The height of the packed bed of the catalyst sample was measured, and it was set as column 17 'of each of Examples 1-3 and Comparative Examples 1-3. The top and bottom of the packed bed were packed with an appropriate amount of rock wool.

These columns 17 ′ were then placed in the electric furnace 16. The packed bed temperature in these columns 17 ′ was measured by a thermocouple attached to the inner wall of the reaction tube 17, and the temperature in the electric furnace 16 was controlled using a temperature controller.
Since the pressure loss of the packed bed varies depending on the type and state of the catalyst sample, the total gas amount of the sample gas was adjusted to 20 mL (liter) / min, and the pressure loss was measured. Table 1 shows the pressure loss (Pa) of each of Examples 1 to 3 and Comparative Examples 1 to 3.

Next, a mixed gas of oxygen and helium (10% by volume O ₂ -90% by volume He) is adjusted in each of these columns 17 ′ by adjusting the flow rates of the O ₂ gas pipe 13 and the He gas pipe 14 respectively. And the inside of the column 17 ′ was purged.
Next, the electric furnace 16 is heated to reach a predetermined temperature (900 ° C.), and then the propylene / helium mixed gas is added to the above-mentioned mixed gas of oxygen and helium, and the composition of the inlet gas of the column 17 ′ is changed to propylene. : 1000 ppm, oxygen: 10 vol%. This state was maintained for 30 minutes to be stabilized, and the catalyst performance of each of the catalyst samples of Examples 1 to 3 and Comparative Examples 1 to 3 was evaluated in this steady state.

In evaluating the catalyst performance, the concentration of propylene (C ₃ H ₆ ) contained in each of the gas on the inlet side and the gas on the outlet side of the column 17 ′ was measured by the FID gas chromatograph 18. The column temperature of the FID gas chromatograph 18 was 100 ° C. The chromatograph was recorded and analyzed using an integrator, and each gas concentration was calculated from the peak area of propylene (C ₃ H ₆ ).

Next, the catalytic activity of each catalyst sample was evaluated from the respective gas concentrations and the propylene (C ₃ H ₆ ) decomposition rate defined by the following formula (1).
Propylene (C ₃ H ₆ ) decomposition rate (%)
= (1- _(C 3 _{H 6} concentration of the reaction tube outlet) / (reaction tube inlet of _C 3 _{H 6} concentration) × 100 (%) ...... (1)
Here, the temperature in the column 17 ′ when the propylene decomposition rate reached 50% was measured, and the catalyst activity of each catalyst sample was evaluated based on the temperature in the column 17 ′. The evaluation results are shown in Table 1.

The pressure loss of each of Examples 1 to 3 was as low as less than 1 Pa and had a sufficient space velocity. The 50% decomposition temperature indicating catalytic activity was in the range of 270 ° C to 420 ° C.
On the other hand, in Comparative Examples 1 and 2 using raw material fine particles as they were, the pressure loss was as high as 5 Pa or more, and a sufficient space velocity was not obtained. Moreover, in Comparative Example 3, the pressure loss was 2.1 Pa, which was also higher than Examples 1 to 3, and a sufficient space velocity was not obtained. The reason why the pressure loss of Comparative Example 3 is lower than that of Comparative Examples 1 and 2 is that the raw material powder is dried and then crushed after being liquefied, so that the particles are aggregated to some extent. It is done.
Moreover, the 50% decomposition temperature of Comparative Examples 1 to 3 was 30 to 90 ° C. higher than the decomposition temperatures of the corresponding Examples 1 to 3, indicating that the catalytic activity in Examples 1 to 3 was high.

DESCRIPTION OF SYMBOLS 1 Hollow granular particle 2 Primary particle 3 Cavity 4 Hollow secondary particle 5 Cavity 11 Gas flow-type catalytic reactor 12 C ₃ H ₆ / He mixed gas piping 13 O ₂ gas piping 14 He gas piping 15 Gas mixer 16 Electric furnace 17 Reaction tube 17 'Column 18 FID gas chromatograph 19 Pressure loss meter 20 Flowmeter t ₁ Thickness of shell-shaped portion of hollow secondary particles r ₁ Particle radius of secondary particles t ₂ Shell-shaped portion of hollow granular particles Thickness r ₂ Radius radius of hollow granular particles

Claims (7)

A hollow secondary particle having a particle diameter of 0.2 μm or more and 20 μm or less formed by combining primary particles in a shell shape, and a particle diameter formed by further combining the hollow secondary particles in a shell shape is 3 μm or more and 500 μm or less. Hollow granular particles,
A hollow granular particle characterized in that the thickness of the shell-shaped portion of the hollow granular particle is not less than 1/4 and not more than 2/3 of the particle radius of the hollow granular particle.   The hollow granular particle according to claim 1, wherein the thickness of the shell-shaped portion of the hollow secondary particle is not less than 1/4 and not more than 2/3 of the particle radius of the hollow secondary particle.   3. The hollow granular particle according to claim 1, wherein an average particle diameter of the primary particles is 0.003 μm or more and 5 μm or less.   The primary particles are present as an oxide, carbide or nitride containing one or more elements selected from Group 3 to 14 elements excluding carbon, or as a composite containing two or more kinds. The hollow granular particle according to any one of claims 1 to 3, wherein the hollow granular particle is formed.   The hollow granular particle according to any one of claims 1 to 4, wherein fine metal particles are attached to the surface of the primary particle.   A primary particle dispersion liquid in which primary particles are dispersed in a dispersion medium together with a first organic polymer is spray-dried, and then fired to have a particle diameter of 0.2 μm or more formed by binding primary particles in a shell shape. Hollow secondary particles having a diameter of 20 μm or less are formed, and then a secondary particle dispersion obtained by dispersing the hollow secondary particles in the dispersion medium together with the second organic polymer is spray-dried, and then fired to form a hollow secondary particle. A method for producing hollow granular particles, characterized by forming hollow granular particles having a particle diameter of 3 µm or more and 500 µm or less formed by binding particles in a shell shape.   A gas processing apparatus comprising the hollow granular particles according to any one of claims 1 to 4.

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