JP5859487B2 - Exhaust gas purification catalyst carrier, exhaust gas purification catalyst using the same, and method for producing exhaust gas purification catalyst carrier - Google Patents

Description

  The present invention relates to an exhaust gas purification catalyst carrier, an exhaust gas purification catalyst using the same, and a method for producing an exhaust gas purification catalyst carrier.

  As a catalyst for exhaust gas purification, a three-way catalyst in which a noble metal such as platinum, rhodium and palladium is supported on a metal oxide carrier made of alumina, titania, silica, zirconia, ceria or the like is widely known. In addition, for the purpose of improving the catalytic activity, a plurality of types of metal oxide supports are mixed or laminated and the characteristics of each metal oxide support are used. For example, ceria has an oxygen storage ability (OSC ability) that stores oxygen when the oxygen concentration in the exhaust gas is high and releases oxygen when the oxygen concentration in the exhaust gas is low, but has relatively low heat resistance. Is. Therefore, the heat resistance of the catalyst is improved by using ceria and zirconia or alumina as a solid solution or mixed.

  Japanese Patent Laid-Open No. 2001-170500 (Patent Document 1) discloses a carrier prepared by mixing an alumina mesoporous powder and a ceria-zirconia solid solution, and an exhaust gas purifying catalyst having a noble metal supported on the carrier. It is disclosed. Japanese Patent Application Laid-Open No. 2010-29844 (Patent Document 2) discloses a carrier made of an inorganic oxide prepared by mixing boehmite or alumina powder and zirconia powder stabilized with Y or Ce, and the carrier. Discloses a catalyst for catalytic partial oxidation of hydrocarbons in which an active metal such as a noble metal is supported. Further, JP-A-2006-298759 (Patent Document 3) contains alumina, ceria and zirconia prepared by mixing an alumina compound such as aluminum nitrate or activated alumina powder, cerium nitrate, and zirconium nitrate. And an exhaust gas purifying catalyst obtained by impregnating the composite oxide with a noble metal. JP-A-2002-160922 (Patent Document 4) discloses a composite oxide containing alumina and a ceria-zirconia solid solution prepared by a coprecipitation method using an aluminum compound, a cerium compound, and a zirconium compound, and An exhaust gas purifying catalyst in which a noble metal is supported on this composite oxide is disclosed.

  However, a catalyst including a carrier prepared by a powder mixing method (Patent Documents 1 to 3) or a coprecipitation method (Patent Documents 3 to 4) is not necessarily excellent in heat resistance. In some cases, the OSC ability decreased.

JP 2001-170500 A JP 2010-29844 A JP 2006-298759 A JP 2002-160922 A

  The present invention has been made in view of the above-mentioned problems of the prior art, and an exhaust gas purifying catalyst carrier capable of obtaining a catalyst exhibiting an excellent oxygen storage capacity (OSC capacity) even when exposed to high temperatures, and It aims at providing the manufacturing method.

  As a result of intensive studies to achieve the above object, the inventors of the present invention contain a predetermined amount of alumina, ceria and zirconia, and after heat treatment at a high temperature (for example, 1100 ° C.), alumina, ceria and zirconia By using a composite metal oxide porous body disposed in a state of being finely and uniformly dispersed with each other as a support, a catalyst in which a noble metal is supported on the support is exposed to a high temperature for a long time (for example, 1100 It was found that excellent OSC ability was exhibited even after an endurance test at 5 ° C. for 5 hours, and the present invention was completed.

That is, the catalyst carrier for exhaust gas purification of the present invention comprises a composite metal oxide porous body containing 5 to 30% by mass of alumina, 25 to 39% by mass of ceria, and 33 to 51% by mass of zirconia,
100 microscopic regions obtained by energy dispersive X-ray analysis of a composite metal oxide porous body after calcination in air at 1100 ° C. for 5 hours using a scanning transmission electron microscope with a spherical aberration corrector The standard deviation of the content ratio (unit: at%) of aluminum element, cerium element, and zirconium element for (one minute region is 300 nm in length × 330 nm in width) satisfies the condition that all are 18.5 or less. It is characterized by this.

In the exhaust gas purifying catalyst carrier of the present invention, the composite metal oxide porous body after calcination in air at 1100 ° C. for 5 hours has a pore diameter in the range of 1 nm to 0.1 μm measured by a nitrogen adsorption method. The total pore volume of the pores is 0.1 cm ³ / g or more, and the total pore volume of pores having a pore diameter in the range of 0.1 μm to 10 μm measured by mercury porosimetry is 0.1 cm ^3. / G or more is preferable.

Moreover, in the exhaust gas purifying catalyst carrier of the present invention, the composite metal oxide porous body after calcination in air at 1100 ° C. for 5 hours has a BET specific surface area of 2 m ² / g or more measured by a nitrogen adsorption method. It is preferable that the condition is satisfied.

  Further, the exhaust gas purifying catalyst of the present invention is characterized by comprising such an exhaust gas purifying catalyst carrier of the present invention and a noble metal supported on the catalyst carrier. Is preferably palladium.

Further, the method for producing an exhaust gas purification catalyst carrier of the present invention is a method for producing an exhaust gas purification catalyst carrier comprising a composite metal oxide porous material containing alumina, ceria and zirconia,
Aluminum ion and cerium ion so that the content of alumina in the composite metal oxide porous body is 5 to 30% by mass, the content of ceria is 25 to 39% by mass, and the content of zirconia is 33 to 51% by mass. And a step of preparing a first raw material solution containing zirconium ions,
Preparing a second raw material solution containing a polymer dispersant having a weight average molecular weight of 3000 to 15000;
A step of directly introducing the first raw material solution and the second raw material solution directly into a region having a shear rate of 1000 to 200000 sec ⁻¹ and homogeneously mixing them to obtain a metal compound colloidal solution;
Adjusting the pH of the colloidal solution to 3-5;
If necessary, adding an organic amine to the colloidal solution and subjecting it to a gelation treatment to obtain a suspension of a metal compound;
degreasing the pH-adjusted colloidal solution or the suspension of the metal compound, and heat-treating at 700 to 1050 ° C. in an oxidizing atmosphere to obtain the composite metal oxide porous body. is there.

  In the method for producing a catalyst carrier for exhaust gas purification of the present invention, it is preferable that at least one of the first and second raw material solutions further contains a low molecular dispersant having a molecular weight of 40 to 200, It is particularly preferable that the low molecular dispersant is contained in the first raw material solution.

  By the production method of the present invention, even after heat treatment at high temperature (in air, 1100 ° C., 5 hours), alumina, ceria and zirconia have a high degree of mutual fine dispersion (that is, a state in which they are finely and uniformly dispersed with each other). Although the reason why the composite metal oxide porous body arranged in (1) is obtained is not necessarily clear, the present inventors infer as follows. That is, nanoparticles such as metal compound crystallites easily aggregate in an aqueous solution such as water, and usually a polymer dispersant is added and adsorbed on the nanoparticles to suppress aggregation. The polymer dispersant (polyalkyleneimine, polyethylene glycol, polyacrylic acid, etc.) used in the present invention is also presumed to adsorb to the nanoparticles and suppress aggregation. Only by stirring, aggregates having a large particle size tend to be formed. This is because the polymer dispersant is usually larger than the primary particles and easily forms a crosslinked structure, so that the nanoparticles adsorbed by the polymer dispersant are agglomerated with the crosslinking reaction of the polymer dispersant, This is presumably because the polymer dispersant is adsorbed simultaneously on a plurality of metal compound crystallites.

  On the other hand, in the production method of the present invention, since a predetermined shearing force is applied to the reaction field in addition to the addition of the polymer dispersant, the aggregate structure of the metal compound crystallites is destroyed at the same time. Since the dispersant is adsorbed on the nanoparticles and the pH of the colloidal solution is adjusted to a predetermined condition, it is assumed that the nanoparticles are present in the colloidal solution in the form of aggregates with a relatively small particle size. The In addition, since the polymer dispersant is stably present in the colloidal solution, aggregates having a large particle size are not easily formed. Further, in the production method of the present invention, such a colloidal solution exhibits a dispersed state in the liquid. It is presumed that the nanoparticles are stably dispersed in the colloidal solution in the form of aggregates having a relatively small particle size because of the pH conditions that can be maintained. In the production method of the present invention, since colloidal solution in which such nanoparticles are uniformly dispersed is degreased and heat-treated at a specific temperature condition, alumina, ceria and zirconia are arranged with a high degree of mutual fine dispersion. It is presumed that a composite metal oxide porous body is obtained.

  In addition, when an organic amine is added to the colloid solution and gelation is performed, the composite metal oxide porous body in which alumina, ceria and zirconia are arranged with a high degree of mutual fine dispersion even after heat treatment at a high temperature is obtained. The reason why it is obtained is not necessarily clear, but the present inventors speculate as follows. That is, when a basic solution such as aqueous ammonia is added to the colloidal solution to adjust the pH to 7 or more, it is assumed that the polymer dispersant such as polyalkyleneimine is separated from the colloidal particles and aggregates. At this time, colloidal particles that have lost the polymer dispersant are also agglomerated, so it is assumed that the colloidal solution becomes a suspension. In particular, it is presumed that agglomeration is remarkable in alumina which is considered to have lower crystallinity than the ceria / zirconia colloid precursor. And in the composite metal oxide porous body obtained using such a suspension, it is speculated that the alumina particles are aggregated. When such a composite metal oxide porous body is heat-treated at a high temperature, the grain growth of alumina is promoted, the diffusion barrier function by alumina does not sufficiently function, and ceria and zirconia also grow, and alumina It is speculated that the mutual fine dispersion degree of ceria and zirconia is lowered. On the other hand, in the production method of the present invention, an organic amine is added to the colloidal solution, so even if the polymer dispersant such as polyalkyleneimine is detached from the colloidal particles, the organic amine is similar to the polymer dispersant. It is presumed that excessive aggregation of alumina, ceria and zirconia colloids is suppressed. As a result, in the obtained composite metal oxide porous body, it is presumed that alumina, ceria and zirconia are arranged with high mutual fine dispersion. Such a composite metal oxide porous body has high heat resistance because the grain growth of ceria and zirconia is sufficiently suppressed by the diffusion barrier function of highly finely dispersed alumina even when heat treatment is performed at high temperature. It is presumed that high mutual fine dispersion of alumina, ceria and zirconia is maintained even after heat treatment at high temperature.

  Further, according to the production method of the present invention, there are pores having a pore diameter of 1 nm to 0.1 μm (mesopores) and pores having a pore diameter of 0.1 μm to 10 μm (macropores), The reason why a porous composite metal oxide having a relatively large total pore volume and a relatively large specific surface area can be obtained even after the heat treatment in FIG. The inventors speculate as follows. That is, in the production method of the present invention, the nanoparticles were agglomerated by degreasing the colloidal solution in which the nanoparticles were uniformly dispersed in a state of an aggregate having a relatively small particle diameter, and heat-treating at a specific temperature condition. It is inferred that a composite metal oxide porous body is formed, and voids between the nanoparticles form the mesopores. Further, it is presumed that macropores are formed in the composite metal oxide porous body by removing the polymer dispersant when the colloidal solution is degreased. The composite metal oxide porous body contains a predetermined amount of alumina having excellent heat resistance, and the alumina has high crystallinity and a stable secondary aggregate structure. Even if it is applied, the macropores are not easily destroyed, and the grain barrier growth of ceria and zirconia is suppressed by the diffusion barrier function of highly finely dispersed alumina, so that a relatively large total pore volume and specific surface area are obtained. Presumed to be obtained.

  Further, although the reason why the exhaust gas purifying catalyst including such a composite metal oxide porous body as a support exhibits excellent OSC ability even after being exposed to high temperature is not necessarily clear, the present inventors have I guess so. That is, in the composite metal oxide porous body according to the present invention, a high degree of mutual fine dispersion of alumina, ceria and zirconia is ensured even after heat treatment at high temperature. This means that during heat treatment at a high temperature, one of the particles arranged with high mutual fine dispersion functions effectively as the other diffusion barrier, and the grain growth of each other is effective. This is presumed to be suppressed. For this reason, in the composite metal oxide porous body according to the present invention, it is speculated that the surface areas of ceria and zirconia are sufficiently secured even after heat treatment at high temperature. Usually, in order to effectively express the OSC ability, a noble metal such as Pd and Pt is supported on a composite metal oxide having an OSC ability such as ceria and zirconia. The OSC ability is more effectively emitted as the contact interface between the composite metal oxide having the OSC ability and the noble metal, that is, the OSC active point increases. In the exhaust gas purifying catalyst of the present invention, noble metals are supported on a carrier that sufficiently secures the surface area of ceria and zirconia even after heat treatment at a high temperature as described above. The contact area between the zirconia and the noble metal is sufficiently secured, and the noble metal is supported on a carrier that effectively suppresses the grain growth of each other particles at the time of heat treatment at a high temperature. However, it is presumed that the grain growth of the noble metal itself is also suppressed. For this reason, in the exhaust gas purifying catalyst of the present invention, even when exposed to high temperatures, thermal degradation is unlikely to occur, a sufficient amount of OSC active sites exist, and it is estimated that excellent OSC performance is exhibited. The Moreover, in the composite metal oxide porous body according to the present invention, the total pore volume after heat treatment at a high temperature (particularly, the total pore volume of macropores) is relatively large. In the exhaust gas-purifying catalyst, it is presumed that gas diffusibility inside the carrier is sufficiently secured, a large amount of reaction gas easily reaches the active point inside the carrier, and excellent OSC ability is obtained. Furthermore, the composite metal oxide porous body according to the present invention has a relatively large specific surface area after heat treatment at a high temperature. This indicates that the exhaust gas purifying catalyst after being exposed to a high temperature has an excellent OSC ability. It is inferred that this is a factor.

  According to the present invention, it is possible to provide an exhaust gas purifying catalyst carrier capable of obtaining a catalyst exhibiting an excellent oxygen storage capacity (OSC capacity) even when exposed to high temperatures, and a method for producing the same.

It is a schematic longitudinal cross-sectional view which shows suitable one Embodiment of the manufacturing apparatus of the colloidal solution used for this invention. FIG. 2 is an enlarged longitudinal sectional view showing a tip portion (stirring portion) of the homogenizer 10 shown in FIG. 1. It is a side view of the inner side stator 13 shown in FIG. It is a cross-sectional view of the inner stator 13 shown in FIG. It is a scanning transmission electron micrograph which shows the state after heat processing at the high temperature of the composite metal oxide porous body obtained in Example 3.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

  First, the exhaust gas purifying catalyst carrier of the present invention will be described. The exhaust gas purifying catalyst carrier of the present invention is composed of a composite metal oxide porous body containing 5 to 30% by mass of alumina, 25 to 39% by mass of ceria, and 33 to 51% by mass of zirconia. When the content of alumina is less than the lower limit, the function of alumina as a diffusion barrier is reduced, and therefore, the exhaust gas purifying catalyst exposed to high temperature has a reduced pore volume and specific surface area, resulting in decreased OSC ability. On the other hand, if the content of alumina exceeds the upper limit, the content of ceria decreases, so the OSC ability of the catalyst decreases and the content of zirconia also decreases. The OSC ability of the exposed catalyst is further reduced. On the other hand, when the ceria content is less than the lower limit, the OSC ability of the catalyst decreases. On the other hand, when the ceria content exceeds the upper limit, the zirconia content decreases, so that the heat resistance of the catalyst decreases, and the OSC ability of the catalyst exposed to high temperatures decreases. Further, since the content of alumina is also reduced, the function of alumina as a diffusion barrier is reduced, and the exhaust gas purifying catalyst exposed to high temperature is further reduced in pore capacity and specific surface area to further lower the OSC ability. Furthermore, when the content of zirconia is less than the lower limit, the heat resistance of the catalyst is lowered, and the OSC ability of the catalyst exposed to a high temperature is lowered. On the other hand, when the upper limit is exceeded, the ceria content decreases, the OSC ability of the catalyst decreases, and the alumina content decreases, so the function of alumina as a diffusion barrier is reduced and exposed to high temperatures. The exhaust gas purifying catalyst has a reduced pore volume and specific surface area, and the OSC ability is lowered.

  Moreover, in such a composite metal oxide porous body, it is preferable that ceria and zirconia form a solid solution. That is, the composite metal oxide porous body according to the present invention preferably contains alumina particles and zirconia solid solution ceria particles (CZ particles). This tends to improve the heat resistance of the catalyst.

Furthermore, from the viewpoint of improving the heat resistance of the catalyst, the composite metal oxide porous body includes oxides of rare earth elements (La, Pr, Y, Sc, etc.) other than cerium and alkaline earth metals (Sr, Ca). , Ba, etc.) is preferably further contained at least one metal oxide selected from the group consisting of oxides. From the viewpoint of further improving the oxygen storage capacity and heat resistance of the catalyst, yttria (Y ₂ O ₃₎ and lanthana (it is more preferable to contain at least one of _La 2 _{O 3),} further it is particularly preferably contained yttria _(Y 2 _{O 3).} The content of such a metal oxide is appropriately set so that the effect is obtained.

  In the exhaust gas purifying catalyst carrier of the present invention, alumina, ceria and zirconia are arranged with a high degree of mutual dispersion (that is, in a state of being finely and uniformly dispersed with each other) even after calcination in air at 1100 ° C. for 5 hours. It is made of a composite metal oxide porous body. Specifically, 100 composite metal oxide porous bodies subjected to heat treatment at high temperature under the above conditions were obtained by energy dispersive X-ray analysis performed using a scanning transmission electron microscope with a spherical aberration corrector. Standard deviations of aluminum element content, cerium element content, and zirconium element content (unit: at%) for each micro area (one micro area is 300 nm in length × 330 nm in width) are all 18.5 or less (preferably, 15 or less ). As described above, the exhaust gas purifying catalyst is exposed to a high temperature for a long time by using the composite metal oxide porous body in which alumina, ceria and zirconia are arranged with a high degree of mutual dispersion even after heat treatment at a high temperature. When it is used (for example, after an endurance test at 1100 ° C. for 5 hours), it exhibits excellent OSC ability. From the viewpoint of further improving the OSC ability of such a catalyst, the composite metal oxide porous body subjected to the heat treatment under the above-described conditions is a standard deviation in the content (unit: at%) of the cerium element and the zirconium element. Are preferably those satisfying the condition that all are 10 or less.

  Such a standard deviation is specifically obtained by the following method. That is, first, an energy dispersive X-ray analyzer (EDX) attached to a scanning transmission electron microscope with a spherical aberration correction device (for example, Cs-STEM manufactured by Hitachi High-Technologies Corporation, trade name “HD2700”) is used. Then, elemental analysis of the composite metal oxide porous powder after heat treatment at high temperature is performed, and EDX mapping is performed in an analysis field of view at a predetermined magnification (vertical 100 pixels × horizontal 128 pixels). The magnification is set so that when the analysis field of view is divided into 100 minute regions (vertical 10 divisions × horizontal 10 divisions), the size of one minute region is 300 nm vertical by 330 nm horizontal. Further, when the analysis spot area of EDX is smaller than one pixel of the analysis visual field, the obtained EDX mapping data is averaged for each pixel. Next, the EDX mapping data is averaged for each minute region to calculate the content of each metal element, and the standard deviation of the content of each metal element for 100 minute regions is calculated. It shows that the smaller the standard deviation of the metal element content, the finer and more uniformly dispersed each metal oxide is.

In the composite metal oxide porous body that has been heat-treated at the high temperature under the above conditions, the total number of pores (mesopores) having a pore diameter in the range of 1 nm to 0.1 μm measured by the nitrogen adsorption method The pore volume is preferably 0.1 cm ³ / g or more (more preferably 0.2 cm ³ / g or more), and has a pore diameter in the range of 0.1 μm to 10 μm measured by mercury porosimetry. The total pore volume of the pores (macropores) is preferably 0.1 cm ³ / g or more (more preferably 0.3 cm ³ / g or more). When the total pore volume (particularly, the total pore volume of macropores) is less than the lower limit, in the catalyst exposed to a high temperature, the gas diffusibility into the support decreases and the OSC ability decreases. There is a tendency. The upper limit of the total pore volume is not particularly limited, but the composite metal oxide porous body having a large total pore volume is bulky and is difficult to coat a full-size honeycomb substrate. The total pore volume is preferably 2 cm ³ / g or less, and the total pore volume of macropores is preferably 3 cm ³ / g or less.

Furthermore, in the composite metal oxide porous body that has been heat-treated at a high temperature under the above conditions, the BET specific surface area measured by the nitrogen adsorption method is preferably 2 m ² / g or more. When the BET specific surface area is less than the lower limit, the OSC ability of the catalyst exposed to a high temperature tends to decrease. Moreover, the one where a BET specific surface area is larger is preferable, and although there is no restriction | limiting in particular about an upper limit, Usually, it is 200 m < ² > / g or less.

  The BET specific surface area and the total pore volume of mesopores are determined by the following method. That is, first, the composite metal oxide porous body is cooled to a liquid nitrogen temperature (−196 ° C.), nitrogen gas is introduced at a predetermined pressure, and the nitrogen adsorption amount at the equilibrium pressure is determined by a constant volume gas adsorption method or a gravimetric method. Ask for. Next, the pressure of the introduced nitrogen gas is gradually increased, and the nitrogen adsorption amount at each equilibrium pressure is obtained. The nitrogen adsorption isotherm can be obtained by plotting the obtained nitrogen adsorption amount against the equilibrium pressure. Next, the specific surface area of the composite metal oxide porous body is determined from the obtained nitrogen adsorption isotherm by the BET isotherm adsorption equation. Further, a pore size distribution curve is obtained from the nitrogen adsorption isotherm by the BJH method, and the total pore volume of mesopores is obtained from this pore size distribution curve.

  Further, the total pore volume of the macropores is determined by a mercury intrusion method. That is, mercury is injected into the composite metal oxide porous body at a high pressure, and the relationship between the applied pressure and the amount of mercury injected is determined. The pore diameter is calculated from the applied pressure, the pore volume is calculated from the amount of mercury injected, and these are plotted to obtain a pore size distribution curve. From this pore size distribution curve, the total pore volume of the macropores is calculated. Ask.

  Next, the exhaust gas purifying catalyst of the present invention will be described. The exhaust gas purifying catalyst of the present invention comprises the exhaust gas purifying catalyst carrier of the present invention and a noble metal supported on the surface of the carrier. In the exhaust gas purifying catalyst of the present invention, alumina, ceria and zirconia are arranged with high mutual fine dispersion even after heat treatment at high temperature, and preferably the total pore volume after heat treatment at high temperature (especially , The total pore volume of the mesopores) and the composite metal oxide having a relatively large BET specific surface area, and therefore exhibits excellent OSC ability even when exposed to high temperatures.

  Examples of the noble metal include platinum, rhodium, palladium, osmium, iridium, and gold. These noble metals may be used alone or in combination of two or more. Among these, platinum, rhodium, and palladium are preferable and palladium is more preferable from the viewpoint that the obtained catalyst is useful as a catalyst for purifying exhaust gas. The amount of the noble metal supported is not particularly limited and is appropriately adjusted according to the use of the obtained catalyst, but is preferably about 0.1 to 10 parts by mass with respect to 100 parts by mass of the exhaust gas purification catalyst carrier. .

  In the exhaust gas purifying catalyst of the present invention, the form thereof is not particularly limited. For example, the catalyst may be used in the form of particles, or the honeycomb-shaped monolith catalyst supporting the catalyst on a base material, You may use as a form of the pellet catalyst etc. which shape | molded the catalyst in the pellet shape. The base material used here is not particularly limited, and a particulate filter base material (DPF base material), a monolithic base material, a pellet base material, a plate base material, and the like can be suitably used. The material of such a substrate is not particularly limited, but a substrate made of a ceramic such as cordierite, silicon carbide, aluminum titanate, mullite, or a substrate made of a metal such as stainless steel containing chromium and aluminum. Can be suitably employed. Furthermore, in the exhaust gas purifying catalyst of the present invention, other components (for example, NOx occlusion material) that can be used for various catalysts within a range not impairing the effect thereof may be appropriately supported.

Next, a method for producing the exhaust gas purifying catalyst carrier of the present invention will be described. The method for producing an exhaust gas purifying catalyst carrier of the present invention is a method for producing an exhaust gas purifying catalyst carrier comprising a composite metal oxide porous body containing alumina, ceria and zirconia,
Aluminum ion and cerium ion so that the content of alumina in the composite metal oxide porous body is 5 to 30% by mass, the content of ceria is 25 to 39% by mass, and the content of zirconia is 33 to 51% by mass. And a step of preparing a first raw material solution containing zirconium ions,
Preparing a second raw material solution containing a polymer dispersant having a weight average molecular weight of 3000 to 15000;
A step of directly introducing the first raw material solution and the second raw material solution directly into a region having a shear rate of 1000 to 200000 sec ⁻¹ and homogeneously mixing them to obtain a metal compound colloidal solution;
Adjusting the pH of the colloidal solution to 3-5;
If necessary, adding an organic amine to the colloidal solution and subjecting it to a gelation treatment to obtain a suspension of a metal compound;
degreasing the pH-adjusted colloidal solution or the suspension of the metal compound, and heat-treating at 700 to 1050 ° C. in an oxidizing atmosphere to obtain the composite metal oxide porous body. is there. According to this method, it is possible to obtain the exhaust gas purifying catalyst carrier of the present invention comprising a porous composite metal oxide in which alumina, ceria and zirconia are arranged with a high degree of mutual fine dispersion even after heat treatment at a high temperature. it can.

  In the method for producing an exhaust gas purifying catalyst carrier of the present invention, it is preferable that at least one of the first and second raw material solutions further contains a low molecular dispersant having a molecular weight of 40 to 200. From the viewpoint of obtaining an exhaust gas purifying catalyst carrier with better heat resistance, it is more preferable that the low molecular weight dispersant is contained in the first raw material solution. The low molecular dispersant must be one that does not significantly change the pH of the raw material solution. Examples of such low molecular dispersants include aminocarboxylic acids (for example, 6-aminocaproic acid and 10-aminodecanoic acid). In addition, intramolecular dehydration condensates (for example, lactams such as aminocaproic acid lactam (ε-caprolactam) and aminodecanoic acid lactam) are preferable, and 6-aminocaproic acid and ε-caprolactam are more preferable.

(First raw material solution preparation process)
The first raw material solution containing the aluminum ion, the cerium ion, and the zirconium ion includes an aluminum compound, a cerium compound, a zirconium compound, another metal compound as necessary, and the low molecular weight as necessary. It can be obtained by dissolving the dispersant in a solvent.

  As such aluminum compounds, cerium compounds, zirconium compounds, and other metal compounds, salts of these metals (acetates, nitrates, chlorides, sulfates, sulfites, inorganic complex salts, etc.) are preferably used. From the viewpoint of not producing a corrosive solution such as HCl as a by-product and not containing sulfur as a performance deterioration component when used as a catalyst support for exhaust gas purification, acetate or nitrate is particularly preferable.

  Examples of the solvent used for the first raw material solution include water, a water-soluble organic solvent (methanol, ethanol, propanol, isopropanol, butanol, acetone, acetonitrile, etc.), a mixed solvent of water and the water-soluble organic solvent, and the like. Can be mentioned.

  Each concentration of aluminum compound, cerium compound, zirconium compound, and other metal compounds in the first raw material solution is such that the content of alumina, ceria, zirconia, and other metal oxides in the obtained composite metal oxide porous body is It adjusts suitably so that it may become a predetermined value.

  The cation concentration of the first raw material solution is preferably 0.005 to 1.0 mol / L, more preferably 0.005 to 0.5 mol / L, and still more preferably 0.01 to 0.3 mol / L. . When the cation concentration is in the above range, the metal compound crystallites are dispersed in the liquid in the form of uniform aggregates having a small diameter, and a colloidal solution having excellent storage stability can be obtained. On the other hand, when the cation concentration is less than the lower limit, the yield of the crystallites of the metal compound tends to decrease. In some cases, the distance between the metal compound fine particles) is shorter than the association size of the polymer dispersant, so that the steric hindrance repulsion due to the adsorption of the polymer dispersant does not act effectively, and crystallites and aggregates are Further, it tends to aggregate.

  Furthermore, when the first raw material solution contains the low molecular dispersant, the concentration of the low molecular dispersant is a molar concentration of 0.1 to 0.5 times the cation concentration of the first raw material solution. preferable. When the concentration of the low molecular dispersant is less than the lower limit, the low molecular dispersant cannot cover the surface of the colloidal particles, the function as a protective agent becomes insufficient, and the colloidal particles tend to aggregate with each other. When the upper limit is exceeded, a large amount of viscous tar-like substance is generated during the degreasing treatment, and the specific surface area of the resulting composite metal oxide porous body tends to decrease.

(Second raw material solution preparation step)
The second raw material solution containing the polymer dispersant is obtained by dissolving the polymer dispersant, the pH adjuster as necessary, and the low molecular dispersant as needed. It is done. As the polymer dispersant, polyalkyleneimine, polyacrylic acid, polyvinylpyrrolidone, and polyethylene glycol are preferable, and polyalkyleneimine, polyethylene glycol, and polyacrylic acid are more preferable from the viewpoint that high dispersion performance can be exhibited in the liquid. Polyalkyleneimine and polyethylene glycol are particularly preferred from the viewpoint that the colloidal solution obtained under a predetermined pH condition is particularly excellent in storage stability.

  The weight average molecular weight of the polymer dispersant is preferably 3000 to 15000, and more preferably 8000 to 12000. When the weight average molecular weight of the polymer dispersant is in the above range, the metal compound crystallites are dispersed in the form of uniform aggregates having a small diameter, and a colloidal solution having excellent storage stability can be obtained. On the other hand, when the weight average molecular weight of the polymer dispersant is less than the lower limit, even if the polymer dispersant is adsorbed to the metal compound fine particles, repulsion due to steric hindrance is not sufficiently expressed, and the metal compound fine particles tend to aggregate, On the other hand, when the above upper limit is exceeded, the polymer dispersant tends to form a crosslinked structure and form a large aggregate. The weight average molecular weight is gel permeation chromatography (GPC) (device name: molecular weight distribution measurement system (manufactured by Shimadzu Corporation), solvent: THF, column: GPC-80M, temperature: 40 ° C., speed: 1 ml / min) It is a value converted by a standard substance (trade name: shodex STANDARD, manufactured by Showa Denko KK).

The concentration of the polymer dispersant in the second raw material solution is such that the content of the polymer dispersant in the obtained colloid solution is 5 to 35 mg / m ² (more preferably, relative to the unit surface area of the crystallite of the metal compound). 5 to 15 mg / m ² ). When the content of the polymer dispersant in the colloidal solution falls within the above range, the metal compound crystallites are dispersed in a state of uniform aggregates having a small diameter, and a colloidal solution having excellent storage stability can be obtained. On the other hand, when the content of the polymer dispersant in the colloidal solution is less than the lower limit, the surface of the metal compound fine particles cannot be sufficiently covered with the polymer dispersant, and the metal compound fine particles are aggregated to cause larger aggregation. On the other hand, when the above upper limit is exceeded, a large amount of free polymer dispersant is present in the colloidal solution, so that the crosslinking reaction of the polymer dispersant proceeds remarkably and the aggregate having a large particle size is formed. There is a tendency for aggregates to form.

  In addition, as a pH adjuster used in the second raw material solution, animonia water, bases such as organic amines (eg, ethylenediamine, hexamethylenediamine), acids such as acetic acid and nitric acid, ammonium salts (eg, ammonium acetate, ammonium nitrate) ), Hydrogen peroxide solution and the like. The concentration of the pH adjusting agent in the second raw material solution is appropriately adjusted so that the pH of the resulting colloidal solution is 3-5.

  Furthermore, when the second raw material solution contains the low molecular dispersant, the content of the low molecular dispersant is 0.1 to 0.5 times the cation content in the first raw material solution. Is preferred. When the content of the low molecular dispersant is less than the lower limit, the low molecular dispersant cannot cover the surface of the colloidal particles, the function as a protective agent becomes insufficient, and the colloidal particles tend to aggregate together, When the upper limit is exceeded, a lot of viscous tar-like substances are generated during the degreasing treatment, and the specific surface area of the resulting composite metal oxide porous body tends to decrease.

  Examples of the solvent used for the second raw material solution include water, a water-soluble organic solvent (methanol, ethanol, propanol, isopropanol, butanol, acetone, acetonitrile, etc.), a mixed solvent of water and the water-soluble organic solvent, and the like. .

(Colloid solution preparation process)
In the step of obtaining the colloidal solution, the first raw material solution and the second raw material solution are directly and independently introduced into a region having a shear rate of 1000 to 200,000 sec ⁻¹ and mixed homogeneously. Such homogeneous mixing makes it possible to disperse metal compound crystallites in a liquid in a state of uniform aggregates having a smaller diameter even in a solvent in which metal compound crystallites such as water easily aggregate. .

  As an apparatus used for such a mixing method, for example, the apparatus shown in FIG. Hereinafter, an apparatus suitable for the present invention will be described in detail with reference to the drawings. In the following description and drawings, the same or corresponding elements are denoted by the same reference numerals, and duplicate descriptions are omitted.

  The manufacturing apparatus shown in FIG. 1 includes a homogenizer 10 as a stirring device, and a front end portion (stirring portion) of the homogenizer 10 is disposed in the reaction vessel 20. As shown in FIG. 2, the front end of the homogenizer 10 includes a concave outer stator 12 disposed so that a predetermined gap region is formed between the concave rotor 11 and the outer periphery of the rotor 11, and the rotor. 11 and a convex inner stator 13 arranged so that a predetermined gap region is formed between the inner periphery of the inner stator 11 and the inner periphery. Further, the rotor 11 is connected to a motor 15 via a rotating shaft 14 and has a structure capable of rotating.

  In the manufacturing apparatus shown in FIG. 1, a plurality of nozzles, that is, a nozzle 16 </ b> A for introducing the raw material solution A and a nozzle 16 </ b> B for introducing the raw material solution B are opposed to the rotor 11 in the inner stator 13. It is provided on each surface. Further, a supply device (not shown) for the raw material solution A is connected to the nozzle 16A via a flow path 17A, and a supply device (not shown) for the raw material solution B is connected to the nozzle 16B via a flow path 17B. The raw material solution A and the raw material solution B can be directly and independently introduced into the region between the rotor 11 and the inner stator 13.

  Further, in the manufacturing apparatus shown in FIG. 1, as shown in FIGS. 3 and 4, the nozzle 16 </ b> A and the nozzle 16 </ b> B are orthogonal to the rotation axis X of the rotor 11 on the surface facing the rotor 11 in the inner stator 13. The predetermined surfaces Y are alternately provided in the outer peripheral direction.

  3 and 4, 12 nozzles 16A and 12 nozzles 16B are provided (24-hole type), but the number of nozzles 16A and nozzles 16B is not particularly limited. Accordingly, it is only necessary to provide one nozzle 16A and one nozzle 16B (two-hole type), but the time from when the raw material solution A and the raw material solution B are introduced into the region until homogeneous mixing is further reduced. From the viewpoint of being able to do so, the number of nozzles 16A and 16B is preferably 10 or more, and more preferably 20 or more. On the other hand, the upper limit of the number of each of the nozzles 16A and 16B is not particularly limited and varies depending on the size of the device, but from the viewpoint of more reliably preventing nozzle clogging, the alternately arranged nozzles 16A. It is preferable that the diameter of the opening of the nozzle 16B can take a dimension of about 0.1 mm or more. As described above, the diameter of the opening of the nozzle is not particularly limited and varies depending on the size of the apparatus, but is preferably about 0.1 to 1 mm from the viewpoint of more reliably preventing nozzle clogging. .

  3 and 4, the nozzles 16 </ b> A and the nozzles 16 </ b> B are alternately provided in a row in the outer peripheral direction of one surface Y orthogonal to the rotation axis X of the rotor 11. It may be provided alternately in a plurality of rows in the outer circumferential direction.

In the manufacturing apparatus shown in FIG. 1 described above, regions where the raw material solution A and the raw material solution B are respectively introduced from the nozzle 16A and the nozzle 16B, that is, the inner periphery of the rotor 11 and the inner stator 13 in FIGS. in the region between the outer periphery of, is set to a shear rate becomes 1000～200000Sec ^-1, and more preferably is set so that 2000~100000sec ^-1. When the shear rate in this region is less than the lower limit, the aggregation of the metal compound crystallites and the structure in which the polymer dispersant is adsorbed on the plurality of crystallites are not destroyed, and larger aggregates remain. On the other hand, when the shear rate in this region exceeds the above upper limit, the polymer dispersant is destroyed, and sufficient repulsive force cannot be applied to the metal compound fine particles, and a larger aggregate is formed and a stable colloid. A solution cannot be obtained. In particular, when polyalkyleneimine is used as the polymer dispersant, it is more preferable that the shear rate is set to 20000 sec ⁻¹ or less in each region where the raw material solution A and the raw material solution B are introduced. It is particularly preferable to set it to be 15000 sec ⁻¹ or less.

  Conditions for achieving such a shear rate are affected by the rotational speed of the rotor and the size of the gap between the rotor and the stator. There is a need to. The specific rotation speed of the rotor 11 is not particularly limited and varies depending on the size of the apparatus. For example, the outer diameter of the inner stator 13 is 12.0 mm, and the gap between the rotor 11 and the outer stator 12 is 0. In the case of 2 mm, a gap of 0.5 mm between the rotor 11 and the inner stator 13, and an inner diameter of the outer stator 12 of 18.8 mm, the rotational speed of the rotor 11 is preferably 2000 to 20000 rpm, more preferably 3000 to 15000 rpm. By setting it, it becomes possible to achieve the shear rate. Further, if the gap between the inner stator 13 and the rotor 11 is 0.2 mm, the maximum rotational speed of the rotor 11 can be lowered to preferably 8387 rpm, more preferably 6291 rpm.

  Further, the size of the gap between the rotor 11 and the inner stator 13 is not particularly limited, and varies depending on the size of the device, but is preferably 0.2 to 1.0 mm, 0.5 to 1 More preferably, it is 0.0 mm. Further, the size of the gap between the rotor 11 and the outer stator 12 is not particularly limited, and varies depending on the size of the device, but is preferably 0.2 to 1.0 mm, 0.5 to 1 More preferably, it is 0.0 mm. By adjusting the rotational speed of the rotor 11 in response to the change in the size of the gap, it becomes possible to achieve the shear speed in the above range. If these gaps are less than the lower limit, clogging of the nozzle tends to occur, and if the gap exceeds the upper limit, effective shearing force tends not to be applied.

  Further, in the manufacturing apparatus shown in FIG. 1, the raw material solution A and the raw material solution B respectively supplied from the nozzle 16A and the nozzle 16B are within 1 msec (particularly preferably within 0.5 msec) after being introduced into the region. It is preferable that the nozzle 16A and the nozzle 16B are arranged so as to be homogeneously mixed. Here, the time from when the raw material solution is introduced into the region until it is homogeneously mixed is the nozzle 16B adjacent to the raw material solution A (or raw material solution B) introduced from the nozzle 16A (or nozzle 16B). (Or nozzle 16A) The time until it reaches the position of the nozzle and is mixed with the raw material solution B (or raw material solution A) introduced from the nozzle 16B (or nozzle 16A).

  As described above, the apparatus suitably used in the present invention has been described. In the present invention, the first raw material solution is used as the raw material solution A and the second raw material solution is used as the raw material solution B. There may be. Further, the present invention is not limited to the method using the manufacturing apparatus shown in FIG. For example, in the manufacturing apparatus shown in FIG. 1, the nozzle 16 </ b> A and the nozzle 16 </ b> B are respectively provided on the surface facing the rotor 11 in the inner stator 13, but the nozzle 16 </ b> A and the nozzle 16 </ b> B are respectively rotors in the outer stator 12. 11 may be provided respectively on the surface facing 11. If comprised in that way, it will become possible to introduce the raw material solution A and the raw material solution B directly into the area | region between the rotor 11 and the outer side stator 12, respectively independently. Note that the shear rate in that region needs to be set so as to satisfy the above condition.

  The feeding speed of each raw material solution in the first raw material solution and the second raw material solution is not particularly limited, but is preferably 1.0 to 30 ml / min. If the feed rate of the raw material solution is less than the lower limit, the production efficiency of the metal compound crystallite aggregate tends to decrease, whereas if the upper limit is exceeded, the particle diameter of the metal compound crystallite aggregate tends to increase. It is in.

(PH adjustment step)
In the production method of the present invention, the colloidal solution obtained in the colloidal solution preparation step is adjusted to pH 3-5. When the pH of the colloidal solution is in the above range, the polymer dispersant is adsorbed on the metal compound crystallites, and the metal compound crystallites are dispersed in the form of uniform aggregates with a small diameter, and have excellent storage stability. A solution can be obtained. In particular, when polyalkyleneimine is used as a polymer dispersant, polyalkyleneimine dissociates and NH ₃ ⁺ groups are formed, so that it adsorbs to negatively charged sites or neutral sites of metal compound crystallites. It is easy to do and the dispersion effect is easily given. On the other hand, when the pH is 1 or more and less than 3, since the neutralization point of aluminum is not reached, alumina (or aluminum hydroxide) particles tend not to be sufficiently nucleated. In the composite metal oxide porous body obtained by subjecting such a colloid solution to the heat treatment described later, the heat resistance of alumina is insufficient, and the mutual fine dispersion of alumina, ceria and zirconia tends to be low. When the pH is less than 1, ceria (or cerium hydroxide) particles also tend not to nucleate sufficiently. In a composite metal oxide porous body obtained by subjecting such a colloid solution to a heat treatment described later, ceria and zirconia tend not to be sufficiently dissolved. On the other hand, when the upper limit is exceeded, the polymer dispersant is difficult to adsorb on the metal compound crystallites, and sufficient repulsive force is not expressed between the metal compound crystallites, and the metal compound crystallites tend to aggregate. In particular, when polyalkyleneimine is used as the polymer dispersant, the degree of dissociation of polyalkyleneimine is small, and the amount of polyalkyleneimine adsorbed on metal compound fine particles tends to decrease.

  This pH adjustment may be performed by adding the pH adjusting agent to the colloid solution obtained in the colloid solution preparation step, but the colloid solution obtained in the colloid solution preparation step has a pH of 3 to 5. In addition, it is preferable to add the pH adjuster to at least one of the first and second raw material solutions (more preferably, the second raw material solution) in advance.

  In the production method of the present invention, if necessary, a polymer compound such as polyalkyleneimine, polyacrylic acid, polyvinylpyrrolidone, or polyethylene glycol is added to the colloidal solution adjusted to pH 3 to 5. Is preferred. Such a polymer compound acts as a template for forming macropores, and can be formed in the composite metal oxide porous body by removing it in a heat treatment step described later. .

  The weight average molecular weight of the template polymer compound is preferably 3000 to 15000, and more preferably 8000 to 12000. When the weight average molecular weight of the polymer compound for the template is less than the lower limit, a sufficient amount of macropores tend not to be formed. On the other hand, when the upper limit is exceeded, a hardly decomposable tar-like substance is formed and agglomerated. Tend to progress and a sufficient amount of pores are not formed. The weight average molecular weight is gel permeation chromatography (GPC) (device name: molecular weight distribution measurement system (manufactured by Shimadzu Corporation), solvent: THF, column: GPC-80M, temperature: 40 ° C., speed: 1 ml / min) It is a value converted by a standard substance (trade name: shodex STANDARD, manufactured by Showa Denko KK).

  The amount of the template polymer compound added is preferably 50 to 250 g, more preferably 100 to 200 g based on 1 L of the colloidal solution. If the amount of the template polymer compound added is less than the lower limit, a sufficient amount of macropores tend not to be formed. On the other hand, if the amount exceeds the upper limit, the template polymer compound is not sufficiently decomposed and tar is added. A particulate material is formed, agglomeration proceeds, and a sufficient amount of pores tend not to be formed.

(Hydrothermal process)
In the production method of the present invention, hydrothermal treatment may be performed on the colloidal solution adjusted to pH 3 to 5 as necessary. Thereby, an aluminum compound can fully be crystallized. The hydrothermal treatment temperature in this hydrothermal treatment step needs to be in the range of 70 to 90 ° C. When the temperature is lower than the lower limit, the crystallization of the aluminum compound becomes insufficient, and the rearrangement of atoms hardly occurs when a ceria / zirconia solid solution is formed. On the other hand, when the temperature exceeds the above upper limit, the specific surface area of the catalyst carrier is reduced, and furthermore, only the ceria is separated and deposited alone, so that the heat resistance of the catalyst is likely to be lowered. In addition, the hydrothermal treatment temperature is such that when an aluminum compound is precipitated, the specific surface area is increased, and a solid solution of ceria and zirconia is formed, the rearrangement of atoms is promoted and voids are formed. From the viewpoint that it can be suppressed, it is particularly preferably 80 to 90 ° C.

  Furthermore, the hydrothermal treatment time in such a hydrothermal treatment step can be appropriately adjusted according to the hydrothermal treatment temperature, but is preferably in the range of 360 to 1800 minutes, and preferably in the range of 1200 to 1440 minutes. More preferred. If the hydrothermal treatment time is less than the lower limit, the effect of promoting the dissolution and reprecipitation of the composite metal oxide porous precursor tends to be insufficient. On the other hand, if the upper limit is exceeded, the hydrothermal treatment effect becomes saturated. , Productivity tends to decline.

(Geling process)
In the production method of the present invention, if necessary, an organic amine is added to the colloidal solution adjusted to pH 3-5 or the colloidal solution subjected to hydrothermal treatment, and the pH is adjusted to 6-9.5 again. It may be adjusted and gelled. As a result, in the colloid solution, the polymer dispersant is detached from the aggregate of the metal compound crystallites, and the aggregate of the metal compound crystallites aggregates instantaneously, but the organic amine plays a role similar to that of the polymer dispersant. Therefore, excessive aggregation is suppressed, and a suspension containing an aggregate of metal compound crystallites having an appropriate size can be obtained. The temperature and time at that time are not particularly limited, and for example, it is preferable to fix the uniformly dispersed state by stirring at a temperature of 10 to 40 ° C. for about 5 to 60 seconds. Moreover, as said organic amine, ethylenediamine, triethanolamine, etc. are preferable.

(Heat treatment process)
In the method for producing a catalyst carrier for exhaust gas purification according to the present invention, the colloidal solution adjusted to pH 3 to 5 or the metal compound suspension obtained in the gelation treatment step is degreased and heat treated. The catalyst carrier for exhaust gas purification of the present invention is obtained.

  Although it does not restrict | limit especially as degreasing conditions in this process, In an oxidizing atmosphere (for example, air), it drys on the conditions for 1 to 10 hours at 80-100 degreeC, and is 1-5 hours after that at 200-400 degreeC. It is preferable to degrease under conditions. By performing such degreasing treatment, the polymer dispersant and the template polymer compound are removed, and the macropores are formed.

  As the heat treatment condition, it is necessary that the temperature is 700 to 1050 ° C. in an oxidizing atmosphere (for example, air). If the temperature is less than the lower limit, sintering is not completed, and thus the sintering progresses when the catalyst is used, and the OSC ability is significantly reduced. On the other hand, when the temperature exceeds the upper limit, the specific surface area is reduced, the total pore volume is reduced, and as a result, the OSC ability is lowered. Moreover, as such heat processing temperature, it is especially preferable that it is 800-1050 degreeC from a viewpoint that the more outstanding OSC capability exists in the tendency.

  Furthermore, the heat treatment time is not particularly limited, but it is preferable to maintain the temperature for about 1 to 10 hours. If this time is less than the lower limit, the metal compound after the degreasing treatment tends not to be a metal oxide sufficiently. On the other hand, if the upper limit is exceeded, performance tends to be accompanied by performance degradation such as sintering due to high temperature / oxidation atmosphere. It is in.

  Next, the manufacturing method of the exhaust gas purifying catalyst of the present invention will be described. The method for producing an exhaust gas purification catalyst of the present invention is a method including a step of supporting a noble metal on the surface of an exhaust gas purification catalyst carrier obtained by the production method of the present invention. A specific method for supporting such a noble metal is not particularly limited. For example, the exhaust gas is dissolved in a solution of a noble metal salt (nitrate, chloride, acetate, etc.) or a noble metal complex dissolved in a solvent such as water or alcohol. A method of immersing the purification catalyst carrier, removing the solvent, and firing and pulverizing is suitably used. In the step of supporting the noble metal, the drying condition for removing the solvent is preferably within 30 minutes at 30 to 150 ° C. The firing condition is 250 to 250 in an oxidizing atmosphere (for example, air). About 600 minutes and 30 to 180 minutes are preferable. Moreover, you may repeat such a noble metal carrying | support process until it becomes a desired carrying amount.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
First, 13.75 g of ammonium cerium nitrate, 12.43 g of zirconyl oxynitrate, 0.82 g of yttrium nitrate, 8.78 g of aluminum nitrate, and 1.24 g of lanthanum nitrate are dissolved in 500 g of ion-exchanged water and used as a raw material for the composite metal oxide. A first raw material solution containing ions was prepared. These added amount cation concentration _{0.1mol / L, Al 2 O 3} : CeO 2: ZrO 2: Y 2 O 3: La 2 O 3 = 10.0: 36.2: 47.9: 2.0 : It corresponds to 3.9 (mass ratio). Next, 62.5 g of polyethyleneimine having a weight average molecular weight of 10000 represented by the following formula (1) and 78 g of nitric acid were dissolved in 360 g of ion-exchanged water to prepare a second raw material solution.

  Next, the metal compound nanocolloid solution was produced using the production apparatus (super agitation reactor) shown in FIG. The stator 13 used was a 48-hole type in which 24 nozzles 16A and 24 nozzles 16B were provided. Then, as shown in FIG. 1, the tip of the homogenizer 10 is set so as to be immersed in a 100 ml beaker 20, and the rotor 11 in the homogenizer 10 is rotated at a rotational speed of 3400 rpm while the first raw material solution and the second The raw material solution is fed to the region between the rotor 11 and the inner stator 13 from the nozzle 16A and the nozzle 16B using a tube pump (not shown) at a supply rate of 12.5 ml / min, and mixed. A transparent nanocolloid solution (pH 4) of a metal compound was prepared.

The outer diameter of the rotor 11 is 18.0 mm, the inner diameter of the outer stator 12 is 18.8 mm, the gap between the rotor 11 and the outer stator 12 is 0.4 mm, and the shear rate in the region between them is 8000 sec. ^-1 . The outer diameter of the inner stator 13 is 11.8 mm, the inner diameter of the rotor 11 is 12.2 mm, the gap between the rotor 11 and the inner stator 13 is 0.2 mm, and the shear rate in the region between them is 4600 sec. ^-1 . Moreover, the time from the introduction of the first raw material solution and the second raw material solution into the region until the homogeneous mixing was 0.37 msec. Here, the time until homogeneous mixing is defined as the time until the raw material solution A or the raw material solution B discharged from the nozzle 16A or the nozzle 16B reaches the adjacent nozzle 16B or the nozzle 16A by the rotation of the rotor 11. It is what is done.

  The obtained nanocolloid solution was degreased at 350 ° C. for 5 hours in the air, and the obtained metal compound powder was fired at 900 ° C. for 5 hours in the air to obtain a composite metal oxide porous body powder.

(Example 2)
A cation used as a raw material of the composite metal oxide was prepared by dissolving 10.58 g of ammonium cerium nitrate, 9.51 g of zirconyl oxynitrate, 0.71 g of yttrium nitrate, 1.07 g of lanthanum nitrate, and 15.27 g of aluminum nitrate in 500 g of ion-exchanged water. An aqueous solution containing was prepared. These addition amounts are as follows: cation concentration 0.1 mol / L, Al ₂ O ₃ : CeO ₂ : ZrO ₂ : Y ₂ O ₃ : La ₂ O ₃ = 20.0: 31.9: 42.2: 2.0 : It corresponds to 3.9 (mass ratio). A transparent nanocolloid solution (pH 4) of a metal compound was prepared in the same manner as in Example 1 except that this aqueous solution was used as the first raw material solution, and then a composite metal oxide porous powder was prepared.

(Example 3)
Cation of ammonium cerium nitrate 8.22 g, zirconyl oxynitrate 7.38 g, yttrium nitrate 0.65 g, lanthanum nitrate 1.00 g, and aluminum nitrate 20.03 g in ion-exchanged water 500 g to form a cation as a raw material for the composite metal oxide An aqueous solution containing was prepared. The amount of these added is such that the cation concentration is 0.1 mol / L, Al ₂ O ₃ : CeO ₂ : ZrO ₂ : Y ₂ O ₃ : La ₂ O ₃ = 29.5: 27.9: 36.9: 2.0 : It corresponds to 3.9 (mass ratio). A transparent nanocolloid solution (pH 4) of a metal compound was prepared in the same manner as in Example 1 except that this aqueous solution was used as the first raw material solution, and then a composite metal oxide porous powder was prepared.

Example 4
In the same manner as in Example 3, a transparent nanocolloid solution (pH 4) of the metal compound was prepared. Ethylenediamine was quickly added to this nanocolloid solution with propeller stirring (300 rpm) to prepare a pH 7 suspension. The suspension was degreased in the same manner as in Example 1, and then the resulting metal compound powder was fired in the same manner as in Example 1 to obtain a composite metal oxide porous powder.

(Comparative Example 1)
An aqueous solution containing a cation serving as a raw material of the composite metal oxide was prepared by dissolving 18.63 g of ammonium cerium nitrate, 16.84 g of zirconyl oxynitrate, 0.50 g of yttrium nitrate, and 0.75 g of lanthanum nitrate in 500 g of ion-exchanged water. These added amount cation concentration _{0.1mol / L, Al 2 O 3} : CeO 2: ZrO 2: Y 2 O 3: La 2 O 3 = 0.0: 40.5: 53.6: 2.0 : It corresponds to 3.9 (mass ratio). A transparent nanocolloid solution (pH 2) of the metal compound was prepared in the same manner as in Example 1 except that this aqueous solution was used as the first raw material solution and a second raw material solution in which the amount of nitric acid was changed to 85 g was used. After the preparation, a composite metal oxide porous powder was prepared.

(Comparative Example 2)
Dissolve 5.01 g of ammonium cerium nitrate, 4.30 g of zirconyl oxynitrate, 0.53 g of yttrium nitrate, 0.80 g of lanthanum nitrate, and 26.86 g of aluminum nitrate in 500 g of ion-exchanged water to obtain a cation as a raw material for the composite metal oxide. An aqueous solution containing was prepared. These added amount cation concentration _{0.1mol / L, Al 2 O 3} : CeO 2: ZrO 2: Y 2 O 3: La 2 O 3 = 47.6: 20.4: 25.8: 2.0 : It corresponds to 3.9 (mass ratio). A transparent nanocolloid solution (pH 4) of a metal compound was prepared in the same manner as in Example 1 except that this aqueous solution was used as the first raw material solution, and then a composite metal oxide porous powder was prepared.

(Comparative Example 3)
A transparent nanocolloid solution (pH 1) of the metal compound was prepared in the same manner as in Example 3 except that the second raw material solution in which the amount of nitric acid was changed to 115 g was used. Aqueous ammonia was quickly added to the resulting nanocolloid solution with propeller stirring (300 rpm) to adjust to pH 9 to obtain a suspension. The suspension was degreased in the same manner as in Example 1, and then the resulting metal compound powder was fired in the same manner as in Example 1 to obtain a composite metal oxide porous powder.

(Comparative Example 4)
A transparent nanocolloid solution (pH 1) of the metal compound was prepared in the same manner as in Example 3 except that the second raw material solution in which the amount of nitric acid was changed to 115 g was used. The obtained nanocolloid solution was sealed in a pressure vessel made of Teflon (registered trademark), and hydrothermally treated by heating at 80 ° C. for 24 hours. Aqueous ammonia was quickly added to the nanocolloid solution after hydrothermal treatment with propeller stirring (300 rpm) to adjust to pH 9 to obtain a suspension. The suspension was degreased in the same manner as in Example 1, and then the resulting metal compound powder was fired in the same manner as in Example 1 to obtain a composite metal oxide porous powder.

(Comparative Example 5)
In the same manner as in Example 3, a first raw material solution containing a cation serving as a raw material for the composite metal oxide was prepared. Next, 40 g of ammonia water was dissolved in 460 g of ion exchange water to prepare a second raw material solution. The second raw material solution was quickly added to the first raw material solution, and propeller stirring (300 rpm) was performed for 24 hours to obtain a cloudy suspension (pH 10). The suspension was degreased in the same manner as in Example 1, and then the resulting metal compound powder was fired in the same manner as in Example 1 to obtain a composite metal oxide porous powder.

<Specific surface area, pore volume>
Examples 1 to 4 were performed by a constant volume gas adsorption method using a liquid nitrogen temperature (−196 ° C.) using an automatic specific surface area / pore distribution measuring device (trade name “Autosorb-1” manufactured by Cantachrome Co., Ltd.). And the nitrogen adsorption isotherm of the composite metal oxide porous body powder obtained in Comparative Examples 1 to 5 was determined. The composite metal oxide porous powder was vacuum degassed at 120 ° C. for 2 hours before measurement. From the obtained nitrogen adsorption isotherm, the specific surface area of the composite metal oxide porous powder (before the heat treatment at high temperature) by the BET method and the pore size distribution curve by the BJH method are obtained, and further 1 nm from the obtained pore size distribution curve The total pore volume of pores having pore diameters in the range of ˜0.1 μm was determined. These results are shown in Tables 1-2.

  Further, a pore diameter distribution curve of the composite metal oxide porous powder (before heat treatment at high temperature) was determined using a mercury porosimeter (trade name “Pore Master 60GT” manufactured by Cantachrome Co., Ltd.), and the obtained pore diameter From the distribution curve, the total pore volume of pores having a pore diameter in the range of 0.1 μm to 10 μm was determined. The results are shown in Tables 1-2.

<Average crystallite size>
X-ray diffraction (XRD) patterns of the composite metal oxide porous powders (before heat treatment at high temperature) obtained in Examples 1 to 4 and Comparative Examples 1 to 5 were converted into powder X-ray diffractometers (manufactured by Rigaku Corporation, products) Using the name “RINT-2200”, measurement was performed under the conditions of a scan step of 0.01 °, a divergence and scattering slit of 1 deg, a light receiving slit of 0.15 mm, a CuKα ray, 40 kV, 20 mA, and a scan speed of 1 ° / min. From the full width at half maximum of the peak derived from the (111) plane of the molten ceria particles (CZ particles), Scherrer's formula:
D = 0.9λ / βcos θ
(In the formula, D represents the crystallite diameter, λ represents the used X-ray wavelength, β represents the half width of the XRD measurement sample, and θ represents the diffraction angle)
Was used to calculate the average crystallite size of the CZ particles. The results are shown in Tables 1-2.

(Heat treatment of composite metal oxide porous body at high temperature)
The composite metal oxide porous body powders obtained in Examples 1 to 4 and Comparative Examples 1 to 5 were heat-treated in air at 1100 ° C. for 5 hours.

<Specific surface area, pore volume, average crystallite diameter>
The BET specific surface area of the composite metal oxide porous powder after the heat treatment at high temperature, the total pore volume measured by the nitrogen adsorption method and the mercury intrusion method, and the average crystallite size of the CZ particles were calculated according to the above methods. These results are shown in Tables 1-2.

<Electron microscope observation>
The composite metal oxide porous powder after heat treatment at high temperature was observed using a scanning transmission electron microscope with a spherical aberration correction device (Cs-STEM manufactured by Hitachi High-Technologies Corporation, trade name “HD2700”). A STEM photograph of the composite metal oxide porous powder of Example 3 (after heat treatment at high temperature) is shown in FIG.

<Standard deviation of metal element content>
First, the composite metal oxide porous powder after heat treatment at high temperature is subjected to elemental analysis using an energy dispersive X-ray analyzer (EDX, analysis spot diameter: 0.5 nm) attached to the Cs-STEM, EDX mapping was performed in an analysis visual field (vertical 100 pixels × horizontal 128 pixels) at a magnification of 30,000. The obtained EDX mapping data was averaged for each pixel. The analysis field was extracted so that about 100 particles were included at a magnification of 30,000. Next, the analysis visual field is divided into 100 minute areas (10 vertical parts × 10 horizontal parts), and the EDX mapping data is averaged for each minute area (one minute area is 300 nm long × 330 nm wide). The content of each metal element was calculated. The standard deviation of the content of each metal element for 100 minute regions was calculated. The results are shown in Tables 1-2. In addition, it has shown that each metal oxide is arrange | positioned in the state finely and uniformly disperse | distributed mutually, so that the standard deviation of the content rate of a metal element is small.

(Catalyst preparation)
A composite metal oxide porous body obtained in Examples 1 to 4 and Comparative Examples 1 to 5 using a dinitrodiamine palladium (Pd (NH ₃ ) ₂ (NO ₂ ) ₂ ) acid aqueous solution (Pd concentration: 50 g / L) Palladium was supported so as to be 0.42 g with respect to 100 g of the powder, and calcined in the atmosphere at 300 ° C. for 3 hours to obtain a Pd-supported composite metal oxide porous powder. This powder was molded at 1000 kgf / cm ² using a cold isostatic press, and then pulverized to obtain a pellet-shaped Pd-supported catalyst having a diameter of 0.5 to 1 mm.

<Durability test>
2 g of the obtained Pd-supported catalyst was packed in a quartz reaction tube, and rich gas (H ₂ (2%), CO ₂ (10%), H ₂ O (3%) and N ₂ (remainder)) and lean gas (CO ₂ (10%), O ₂ (1%), H ₂ O (3%) and N ₂ (remainder)) at a temperature of 1100 ° C. The durability test was conducted by alternately supplying 5 hours at a time under the condition of space velocity (SV) of 10000 h ⁻¹ for 5 minutes.

<Measurement of oxygen storage capacity>
A quartz reaction tube is filled with 0.5 g of a Pd-supported catalyst after the endurance test, and rich gas (CO (2%) and N ₂ (remainder)) is used using a fixed bed flow reactor (manufactured by Vest Sokki Co., Ltd.). And lean gas (O ₂ (1%) and N ₂ (remainder)) are alternately supplied at a temperature of 500 ° C. or 600 ° C. and a gas flow rate of 10 L / min for 3 minutes, and CO ₂ produced in a rich atmosphere The amount was measured using an automobile exhaust gas analyzer (made by Best Instrument Co., Ltd., trade name “Bex5900Csp”), and the oxygen storage / release amount (OSC-c) and the oxygen storage / release rate (OSC-r) were calculated. . These results are shown in Tables 1-2.

<Specific surface area, average crystallite diameter>
The BET specific surface area of the Pd-supported catalyst after the durability test and the average crystallite size of the CZ particles were calculated according to the above methods. These results are shown in Tables 1-2.

  As can be seen from the results shown in Table 1, the composite metal oxide porous bodies obtained in Examples 1 to 4 were treated with alumina particles even after heat treatment at high temperature (in air, 1100 ° C., 5 hours). It was confirmed that the CZ particles are arranged with a high degree of mutual fine dispersion (that is, finely and uniformly dispersed with each other). In addition, the composite metal oxide porous body after heat treatment at high temperature has a relatively large BET specific surface area, and further, as shown in FIG. 5, the pore diameter formed between the primary particles is Having mesopores (primary pores) of 1 nm to 0.1 μm and macropores (secondary pores) having a pore diameter of 0.1 μm to 10 μm formed between secondary particles; It was confirmed that the total pore volume of the pores and the macropores was relatively large. In addition, it is guessed that the said macropore was formed when the polymer dispersing agent was removed at the time of a degreasing process. Moreover, by using such a composite metal oxide porous material as a carrier, a noble metal-supported catalyst (catalyst for exhaust gas purification) excellent in oxygen storage / release ability (OSC ability) even after endurance treatment (1100 ° C., 5 hours) It was confirmed that

  On the other hand, as is clear from the results shown in Table 2, in the noble metal-supported catalyst (Comparative Example 1) provided with a composite metal oxide porous body containing no alumina as a support, Examples 1 to 4 In comparison, the oxygen storage and release amount after the durability test was large, but the oxygen storage and release rate was slow. The reason is presumed as follows. That is, since the composite metal oxide porous body obtained in Comparative Example 1 has a higher content of CZ particles having OSC ability than the composite metal oxide porous bodies obtained in Examples 1 to 4, it is durable. It is presumed that the amount of oxygen stored and released from the noble metal supported catalyst after the test increased. On the other hand, since the composite metal oxide porous body obtained in Comparative Example 1 does not contain alumina, the composite metal oxide porous body does not have a diffusion barrier function, and grain growth occurs due to heat treatment at a high temperature, and the total pores of the composite metal oxide porous body It is inferred that the capacity and the BET specific surface area have decreased. As a result, even in the noble metal supported catalyst, the BET specific surface area was reduced by the durability test, so that the active site was not sufficiently secured in the support, and the total pore volume was reduced, so that the gas diffusibility inside the support was reduced. It is assumed that the oxygen storage and release rate became slower. On the other hand, in Examples 1 to 4, since the diffusion barrier function by alumina acts to suppress grain growth during the durability test, the noble metal-supported catalyst has a relatively large BET specific surface area even after the durability test. It is presumed that the active sites are sufficiently secured inside, and the total pore volume is relatively large, so that the gas diffusibility inside the carrier is sufficiently secured. As a result, a large amount of reaction gas easily reaches the active point inside the support, so that it is presumed that the noble metal-supported catalyst showed excellent OSC ability even after the endurance test.

  In addition, the noble metal-supported catalyst (Comparative Example 2) provided with the composite metal oxide porous body having a low content of ceria and zirconia as a support was inferior in OSC ability as compared with Examples 1 to 4. This is presumably because the composite metal oxide porous body obtained in Comparative Example 2 had a low content of CZ particles having OSC ability, and the active sites were not sufficiently secured on the carrier. On the other hand, in Examples 1 to 4, since a predetermined amount of ceria and zirconia was included, the active site was sufficiently secured on the support, and the noble metal-supported catalyst showed excellent OSC ability even after the durability test. Inferred.

  Furthermore, when the nanocolloid solution was adjusted to pH 9 using aqueous ammonia (Comparative Examples 3 to 4), the noble metal-supported catalyst after the durability test was also compared to the case where pH was adjusted to 7 using ethylenediamine (Example 4). The OSC ability was inferior. The reason is presumed as follows. That is, in the composite metal oxide porous body obtained in Comparative Example 3, due to the heat treatment at high temperature, the mutual fine dispersion degree of the alumina particles and the CZ particles was lowered, and the total pore volume of the macropores was reduced. From this, it is presumed that alumina did not function sufficiently as a diffusion barrier for CZ particles. This is because alumina particles are aggregated in the obtained composite metal oxide porous body by adjusting the nanocolloid solution to pH 9 using aqueous ammonia, and the mutual fine dispersion of alumina, ceria and zirconia is high. It is guessed that it decreased. Also in the noble metal-supported catalyst, the aggregated alumina particles did not sufficiently function as a diffusion barrier for the CZ particles. Therefore, the contact area between the CZ particles and the noble metal was reduced by reducing the surface area of the CZ particles by the durability test, that is, In addition, OSC active sites are not sufficiently secured, and noble metal supported on the CZ particles grows due to the growth of the CZ particles, and further, the total pore volume of the macropores decreases, thereby reducing the inside of the support. It is presumed that the gas diffusivity to the surface also decreased and the OSC ability decreased. Even when hydrothermal treatment was performed before pH adjustment with aqueous ammonia (Comparative Example 4), the OSC ability of the noble metal-supported catalyst after the durability test was inferior to that of Example 4. This is because, in the composite metal oxide porous body obtained in Comparative Example 4, the total pore volume of macropores was increased compared to Comparative Example 3, so that the crystallinity of alumina was increased by hydrothermal treatment, and the alumina particles It is inferred that the agglomeration of the particles was improved to some extent, but it was not sufficiently improved to suppress the decrease in the mutual fine dispersion between the alumina particles and the CZ particles, and the decrease in the surface area of the CZ particles could not be sufficiently suppressed. Inferred.

  Further, when a nanocolloid solution having a pH of 10 was prepared using ammonia water as the second raw material solution without using a polymer dispersant (Comparative Example 5), the precious metal after the durability test was also compared with Example 4. The OSC ability of the supported catalyst was inferior. The reason is presumed as follows. That is, in the composite metal oxide porous body obtained in Comparative Example 5, since the polymer dispersant was not used, the total pore volume was reduced even before the heat treatment at high temperature, and further using ammonia water. Since a nanocolloid solution having a pH of 10 was prepared, the alumina particles were aggregated, and it is presumed that the alumina did not sufficiently function as a diffusion barrier for the CZ particles as in Comparative Example 3. As a result, also in Comparative Example 5, as in Comparative Example 3, the OSC active site was not sufficiently secured by the durability test, and noble metal supported on the CZ particles was grown, and further, the inside of the carrier was further increased. It is presumed that the gas diffusibility also decreased and the OSC ability of the noble metal supported catalyst decreased.

  On the other hand, in the composite metal oxide porous body obtained in Example 4, since the nanocolloid solution was adjusted to pH 7 using ethylenediamine, the composite metal oxide in which the alumina particles and the CZ particles were arranged with a high degree of mutual fine dispersion. It is inferred that a porous body was obtained. Even if this composite metal oxide porous body is subjected to a heat treatment at a high temperature, the diffusion barrier of highly finely dispersed alumina functions sufficiently to suppress the growth of CZ particles, and the alumina particles and the CZ particles It is inferred that a high degree of mutual fine dispersion was maintained. As a result, even in the noble metal supported catalyst after the durability test, the diffusion barrier of the highly finely dispersed alumina functioned sufficiently and the growth of CZ particles was suppressed, so that the surface area of CZ particles was sufficiently secured. As a result, a sufficient active site is secured in the carrier, and a sufficient total pore volume of the macropores is secured, so that gas diffusibility inside the carrier is also sufficiently secured. It is presumed that a large amount of reaction gas easily reached, and further supported by highly finely dispersed alumina particles and CZ particles, the grain growth of noble metals was suppressed and an excellent OSC ability was obtained.

(Example 5)
First, ammonium ion cerium nitrate, zirconyl oxynitrate, yttrium nitrate, aluminum nitrate, lanthanum nitrate are added to ion-exchanged water, the cation concentration is 1.0 mol / L, and the addition amount of metal salt is Al ₂ O ₃ : CeO ₂ : ZrO _2. : Y ₂ O ₃ : La ₂ O ₃ = 29.5: 27.9: 36.9: 2.0: It dissolves so that it may become a mass ratio equivalent to 2.0: 3.9, and also 6-amino caproic acid is set to 0. A first raw material solution containing a cation and a low molecular dispersant, which were dissolved to 4 mol / L and used as a raw material for the composite metal oxide, was prepared. Next, a second raw material solution was prepared by dissolving polyethylene diamine having a weight average molecular weight of 8000 in the same amount of ion-exchanged water so as to be 20 g / L and ethylene diamine so as to be 45 g / L.

Next, a transparent nanocolloid solution (pH 3.6) of the metal compound was used in the same manner as in Example 1 except that the first and second raw material solutions were used and the rotation speed of the rotor 11 was changed to 10,000 rpm. Was prepared. The shear rate in the region between the rotor 11 and the outer stator 12 was 23500 sec ⁻¹ , and the shear rate in the region between the rotor 11 and the inner stator 13 was 13500 sec ⁻¹ .

  After adding polyethyleneglycol to the obtained nanocolloid solution so that it might become 175 g / L and fully stirring, ethylenediamine was dripped, stirring, and pH7 suspension was prepared. Thereafter, stirring was continued for 30 minutes. The resulting suspension was degreased in the same manner as in Example 1, and then the obtained metal compound powder was fired in the same manner as in Example 1 to obtain a composite metal oxide porous body powder.

  With respect to this composite metal oxide porous powder, the specific surface area, pore volume, and average crystallite diameter before and after heat treatment at high temperature (in air, 1100 ° C., 5 hours) were measured according to the above methods. As the mercury porosimeter, “AutoPore iv9500” manufactured by Micromeritics was used. Moreover, the standard deviation of the content rate of each metal element of the composite metal oxide porous material powder after heat treatment at high temperature (in air, 1100 ° C., 5 hours) was calculated according to the above method. These results are shown in Table 3.

  A pellet-shaped Pd-supported catalyst was prepared according to the above method except that the obtained composite metal oxide porous powder was used. The oxygen storage capacity (600 ° C.) of this Pd-supported catalyst was measured according to the above method. In addition, after the durability test (1100 ° C., 5 hours) was performed on the Pd-supported catalyst according to the above method, the oxygen storage capacity (600 ° C.) after the durability test was measured according to the above method. These results are shown in Table 3.

  As is apparent from the results shown in Table 3, when the low molecular weight dispersant is contained in the first raw material solution containing a cation that is a raw material of the composite metal oxide (Example 5), it is more heat resistant. It turned out that the composite metal oxide porous body excellent in property is obtained. Furthermore, it was found that a noble metal-supported catalyst using this composite metal oxide porous body as a carrier is also superior in heat resistance.

  As described above, according to the present invention, a catalyst exhibiting excellent oxygen storage capacity (OSC capacity) even when exposed to high temperatures (particularly, a catalyst exhibiting excellent OSC capacity even with a small amount of noble metal supported) can be obtained. It is possible to provide a catalyst carrier for exhaust gas purification that can be used and a method for producing the same.

  DESCRIPTION OF SYMBOLS 10 ... Homogenizer, 11 ... Rotor, 12 ... Outer stator, 13 ... Inner stator, 14 ... Rotating shaft, 15 ... Motor, 16A, 16B ... Nozzle, 17A, 17B ... Flow path (supply pipe), 20 ... Reaction vessel, A , B ... reaction solution, X ... rotation axis, Y ... surface perpendicular to the rotation axis X.

Claims (10)

A composite metal oxide porous body containing 5 to 30% by mass of alumina, 25 to 39% by mass of ceria, and 33 to 51% by mass of zirconia,
100 microscopic regions obtained by energy dispersive X-ray analysis of a composite metal oxide porous body after calcination in air at 1100 ° C. for 5 hours using a scanning transmission electron microscope with a spherical aberration corrector The standard deviation of the content ratio (unit: at%) of aluminum element, cerium element, and zirconium element for (one minute region is 300 nm in length × 330 nm in width) satisfies the condition that all are 18.5 or less. A catalyst carrier for exhaust gas purification characterized by the above. The total pore volume of pores having a pore diameter in the range of 1 nm to 0.1 μm as measured by the nitrogen adsorption method of the composite metal oxide porous body after calcination at 1100 ° C. for 5 hours in the air is 0.00. 1 cm ³ / g or more, and satisfying the condition that the total pore volume of pores having a pore diameter in the range of 0.1 μm to 10 μm measured by mercury porosimetry is 0.1 cm ³ / g or more The exhaust gas-purifying catalyst carrier according to claim 1, wherein The composite metal oxide porous body after calcination at 1100 ° C. for 5 hours in air satisfies a condition that a BET specific surface area measured by a nitrogen adsorption method is 2 m ² / g or more. Item 3. An exhaust gas purifying catalyst carrier according to Item 1 or 2.   The composite metal oxide porous body after calcination at 1100 ° C. for 5 hours in air was determined by the energy dispersive X-ray analysis, and the content of cerium element and zirconium element in 100 minute regions (unit: at 4) The exhaust gas purifying catalyst carrier according to any one of claims 1 to 3, which satisfies a condition that all standard deviations of%) are 10 or less.   An exhaust gas purifying catalyst comprising the exhaust gas purifying catalyst carrier according to any one of claims 1 to 4 and a noble metal supported on the catalyst carrier.   The exhaust gas purifying catalyst according to claim 5, wherein the noble metal is palladium. A method for producing a catalyst carrier for exhaust gas purification comprising a porous composite metal oxide containing alumina, ceria and zirconia,
Aluminum ion and cerium ion so that the content of alumina in the composite metal oxide porous body is 5 to 30% by mass, the content of ceria is 25 to 39% by mass, and the content of zirconia is 33 to 51% by mass. And a step of preparing a first raw material solution containing zirconium ions,
Preparing a second raw material solution containing a polymer dispersant having a weight average molecular weight of 3000 to 15000;
A step of directly introducing the first raw material solution and the second raw material solution directly into a region having a shear rate of 1000 to 200000 sec ⁻¹ and homogeneously mixing them to obtain a metal compound colloidal solution;
Adjusting the pH of the colloidal solution to 3-5;
and a step of degreasing the colloidal solution after pH adjustment and heat-treating at 700 to 1050 ° C. in an oxidizing atmosphere to obtain the composite metal oxide porous body. A method for producing a catalyst carrier for exhaust gas purification comprising a porous composite metal oxide containing alumina, ceria and zirconia,
Aluminum ion and cerium ion so that the content of alumina in the composite metal oxide porous body is 5 to 30% by mass, the content of ceria is 25 to 39% by mass, and the content of zirconia is 33 to 51% by mass. And a step of preparing a first raw material solution containing zirconium ions,
Preparing a second raw material solution containing a polymer dispersant having a weight average molecular weight of 3000 to 15000;
A step of directly introducing the first raw material solution and the second raw material solution directly into a region having a shear rate of 1000 to 200000 sec ⁻¹ and homogeneously mixing them to obtain a metal compound colloidal solution;
Adjusting the pH of the colloidal solution to 3-5;
Adding an organic amine to the colloidal solution and subjecting it to a gelation treatment to obtain a suspension of a metal compound;
And a step of degreasing the suspension and heat-treating at 700 to 1050 ° C. in an oxidizing atmosphere to obtain the composite metal oxide porous body.   9. The exhaust gas purifying catalyst carrier according to claim 7 or 8, wherein at least one of the first and second raw material solutions further contains a low molecular weight dispersant having a molecular weight of 40 to 200. Production method.   The method for producing a catalyst carrier for exhaust gas purification according to claim 9, wherein the low molecular dispersant is contained in the first raw material solution.