JP2014000552A - Catalyst carrier for exhaust gas purification, catalyst for exhaust gas purification using the same, production method of catalyst carrier for exhaust gas purification - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst carrier for exhaust gas purification that can obtain a transition metal carrier catalyst that shows excellent catalytic activity even when being exposed to high temperature, especially high catalytic activity from comparatively cold temperature.SOLUTION: A catalyst carrier for exhaust gas purification comprises a complex metal oxide porous body including alumina, ceria, and zirconia, an inclusion ratio of the alumina being 30-80 mass%, wherein in the complex metal oxide porous body after burning for 5 hours in air at 1100°C, in 100 fine small regions (one fine small region is length 300 nm×width 330 nm) obtained from an energy dispersion type X-ray analysis performed by a scan transmission electron microscope with a spherical surface aberration correction device, a condition in which standard deviations of an inclusion ratio (unit: at%) of an aluminum element, a cerium element and a zirconium element are all at most 19 is satisfied.

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.

  On the other hand, noble metals as described above have been widely used as the metal to be supported on the catalyst carrier, but recently, transition metals such as copper, which are cheaper than noble metals, are also effective as exhaust gas purification catalysts. Are known. However, transition metals such as copper are inferior in heat resistance as compared with noble metals and are likely to grow grains, so that when exposed to high temperatures, the catalytic activity may decrease.

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 it is possible to obtain a transition metal-supported catalyst that exhibits excellent catalytic activity even when exposed to high temperatures, particularly high catalytic activity from a relatively low temperature. An object of the present invention is to provide a catalyst support for exhaust gas purification and a method for producing the same.

  As a result of intensive studies to achieve the above object, the inventors of the present invention are composite metal oxide porous bodies containing alumina, ceria and zirconia, and the content of alumina is within a predetermined range, and the high temperature By using as a support a composite metal oxide porous body in which alumina, ceria and zirconia are arranged in a finely and uniformly dispersed state after heat treatment (for example, 1100 ° C.), a transition metal is added to the support. It has been found that the supported catalyst exhibits excellent catalytic activity even after being exposed to a high temperature for a long time (for example, after an endurance test at 900 ° C. for 5 hours), in particular, high catalytic activity from a relatively low temperature, The present invention has been completed.

That is, the exhaust gas purifying catalyst carrier of the present invention comprises alumina, ceria and zirconia, and is composed of a composite metal oxide porous body having an alumina content of 30 to 80% by mass,
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 19 or less. It is a feature. Moreover, it is preferable that all the said standard deviations of the content rate (unit: at%) of a cerium element and a zirconium element are 15 or less.

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 having a pore diameter in the range of 0.1 μm to 10 μm measured by the mercury intrusion method is 0.18 cm ³ / g or more. It is preferable to satisfy the condition of 3 cm ³ / g or more.

  Further, the exhaust gas purifying catalyst of the present invention comprises the exhaust gas purifying catalyst carrier of the present invention and a transition metal supported on the catalyst carrier, and the transition Copper is preferred as the metal.

The method for producing the 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,
Preparing a first raw material solution containing aluminum ions, cerium ions, and zirconium ions so that the content of alumina in the composite metal oxide porous body is 30 to 80% by mass;
A step of preparing a second raw material solution containing a polymer dispersant;
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.

  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, polyacrylic acid, etc.) used in the present invention is also presumed to adsorb to the nanoparticles and suppress aggregation, but the polymer dispersant is added and normal stirring is performed. Only the particles tend to form aggregates having a large particle size. 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 body in which these pores each have a relatively large total pore volume can be obtained even after the heat treatment in FIG. 1 is not necessarily clear, but the present 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. Since this composite metal oxide porous body contains a predetermined amount of alumina having excellent heat resistance, the macropores are not easily destroyed even when heat treatment is performed at a high temperature. It is presumed that a relatively large total pore volume can be obtained because the grain growth of ceria and zirconia is suppressed by the diffusion barrier function of the dispersed alumina.

  The reason why such a transition metal-supported catalyst (exhaust gas purifying catalyst) comprising a composite metal oxide porous body as a carrier exhibits excellent catalytic activity even after being exposed to high temperatures is not necessarily clear. The inventors speculate as follows. That is, in the exhaust gas purifying catalyst of the present invention, it is presumed that transition metals are supported on alumina, ceria, and zirconia that are arranged with a high degree of mutual fine dispersion. In such an exhaust gas purifying catalyst, the transition metal is presumed to exhibit an excellent catalytic activity by promoting the activation of the transition metal active species by the interaction with ceria and zirconia. The exhaust gas purifying catalyst of the present invention maintains a high degree of mutual fine dispersion of alumina, ceria and zirconia even when exposed to high temperatures. Therefore, the transition metals supported on alumina, ceria and zirconia are respectively It is presumed that the state in which the grains are difficult to grow and is arranged finely and uniformly is maintained. For this reason, it is surmised that the catalyst for exhaust gas purification of the present invention hardly shows a decrease in catalytic activity even when exposed to high temperatures and exhibits excellent catalytic activity.

  On the other hand, when the mutual fine dispersion degree of alumina, ceria and zirconia is low, it is assumed that alumina does not function effectively as a diffusion barrier for ceria and zirconia at high temperatures, so that ceria and zirconia grow. As a result, in transition metal supported catalysts exposed to high temperatures, the transition metal is supported nonuniformly on alumina, ceria, and zirconia (specifically, it is supported on these with the growth of ceria and zirconia grains). It is presumed that the interaction between the transition metal and ceria and zirconia is not sufficiently obtained, and the catalytic activity is lowered.

  Similarly, when the content of alumina is low, it is presumed that the diffusion barrier function of alumina does not sufficiently function, and ceria and zirconia grow at a high temperature. As a result, in transition metal supported catalysts exposed to high temperatures, the transition metals supported on alumina, ceria and zirconia are in a non-uniform state (specifically, they are supported on ceria and zirconia along with the grain growth). Therefore, it is assumed that the catalytic activity decreases.

  According to the present invention, there is provided an exhaust gas purifying catalyst carrier capable of obtaining a transition metal-supported catalyst exhibiting excellent catalytic activity, in particular, high catalytic activity from a relatively low temperature, even when exposed to high temperatures, and a method for producing the same. It becomes possible to provide.

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. 2 is a scanning transmission electron micrograph showing a state after heat treatment at a high temperature of a composite metal oxide porous body obtained in Example 2. FIG.

  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 catalyst carrier for exhaust gas purification of the present invention comprises a composite metal oxide porous body containing alumina, ceria and zirconia, and the alumina content is 30 to 80% by mass. When the content of alumina is less than the lower limit, the function of alumina as a diffusion barrier is reduced. Therefore, the exhaust gas purifying catalyst exposed to high temperature has reduced pore volume and specific surface area, and transition metal grain growth occurs. It is not sufficiently suppressed and the catalytic activity is reduced. On the other hand, when the content of alumina exceeds the upper limit, the content of ceria and zirconia is relatively reduced, so that the interaction between the transition metal, ceria and zirconia is reduced, and the catalytic activity is reduced. Further, from the viewpoint that the activity of the exhaust gas purifying catalyst exposed to high temperature becomes higher, the alumina content is preferably 40 to 70% by mass.

  In the exhaust gas purifying catalyst carrier of the present invention, the content of ceria in the composite metal oxide porous body is not particularly limited, but is preferably 10 to 60% by mass, and more preferably 20 to 50% by mass. When the content of ceria is less than the lower limit, the interaction between the transition metal and ceria decreases, and the catalytic activity tends to decrease. On the other hand, if the ceria content exceeds the above upper limit, the zirconia content decreases, so the stabilization effect of ceria obtained by solid solution of zirconia in ceria decreases, and ceria grows at high temperatures. For this reason, the activity of the exhaust gas purifying catalyst exposed to high temperature tends to decrease. In addition, since the alumina content also decreases, the function of alumina as a diffusion barrier is reduced, and the catalyst for exhaust gas purification exposed to high temperatures has reduced pore volume and specific surface area, resulting in sufficient transition metal grain growth. However, the catalytic activity tends to decrease.

  Furthermore, the content of zirconia in the composite metal oxide porous body is not particularly limited, but is preferably 5 to 40% by mass, and more preferably 5 to 30% by mass. When the content of zirconia is less than the lower limit, the effect of stabilizing ceria decreases, and the activity of the exhaust gas purifying catalyst exposed to high temperatures tends to decrease. On the other hand, when the content of zirconia exceeds the upper limit, the content of ceria decreases, so that the interaction between the transition metal, ceria and zirconia decreases, and the catalytic activity tends to decrease. In addition, since the alumina content also decreases, the function of alumina as a diffusion barrier is reduced, and the catalyst for exhaust gas purification exposed to high temperatures has reduced pore volume and specific surface area, resulting in sufficient transition metal grain growth. However, the catalytic activity tends to decrease.

  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.), and preferably contains at least one metal oxide selected from the group consisting of oxides. From the viewpoint of further improving the heat resistance of the catalyst, yttria (Y ₂ O ₃ ) and It is more preferable to further include at least one of lantana (La ₂ O ₃ ), and it is particularly preferable to further include 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 region (one micro region is 300 nm long by 330 nm wide) are all 19 or less (preferably 18 or less) It satisfies the condition of being. 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. Even when it is used (for example, after an endurance test at 900 ° C. for 5 hours), it exhibits excellent catalytic activity, particularly high catalytic activity from a relatively low temperature of 375 ° C. or lower. Also, from the viewpoint of further improving the activity of the exhaust gas purifying catalyst, the composite metal oxide porous body subjected to the heat treatment at the high temperature under the above conditions is a standard for the content ratio (unit: at%) of the cerium element and the zirconium element. It is preferable that all the deviations are 15 or less (more preferably 14 or less), and the standard deviation of the zirconium element content (unit: at%) is 9 or less (particularly preferably 7 or less). More preferably, it satisfies the condition of being.

  Such a standard deviation is specifically obtained by the following method. That is, first, using 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”). 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 0.18 cm ³ / g or more, and the total pore volume of pores (macropores) having a pore diameter in the range of 0.1 μm to 10 μm measured by mercury porosimetry is It is 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 high temperature, the growth of transition metal particles is not sufficiently suppressed, and the catalytic activity 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 ³ cm ³ / g or less, and the total pore volume of macropores is preferably 4 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 25 m ² / g or more. When the BET specific surface area is less than the above lower limit, the catalyst exposed to a high temperature does not sufficiently suppress the growth of transition metal grains, and the catalytic activity 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 transition 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 BET specific surface area are comparatively large composite metal oxides. Therefore, even when exposed to high temperatures, transition metal grain growth hardly occurs and an excellent catalyst. It shows high activity, particularly from a relatively low temperature of 375 ° C. or lower.

  Examples of the transition metal include Cu, Fe, Ni, Co, Mn, Zn, W, Mo, Nb, Sn, Ta, and Ag. These transition metals may be used individually by 1 type, or may use 2 or more types together. Among these, Cu and Ni are preferable from the viewpoint of exhibiting high NOx reduction performance, and Cu, Fe, Ni, and Mn are preferable from the viewpoint of having high oxidation performance of CO and CH compounds.

The transition metal may be supported as a single metal or as a metal compound. Examples of the transition metal compounds include oxides of the transition metals; salts of hydroxides, chlorides, nitrates, sulfates, organic acid salts, etc .; carbides; nitrides; sulfides; and intermediate products thereof, and Examples thereof include complex oxides of the transition metals. _{Specifically, CuO, Cu 2 O, Cu} (OH) 2, CuCO 3, CuFe 2 O 4, CuAl 2 O 4 and the like. As such a transition metal compound, CuO, CuAl ₂ O ₄ , Cu ₂ O, or Cu (OH) ₂ is preferably used from the viewpoint that the obtained catalyst is useful as a catalyst for exhaust gas purification. .

  The amount of the transition metal supported is not particularly limited and is appropriately adjusted according to the use of the obtained catalyst, and is about 0.1 to 10 parts by mass with respect to 100 parts by mass of the exhaust gas purification catalyst carrier. preferable.

  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,
Preparing a first raw material solution containing aluminum ions, cerium ions, and zirconium ions so that the content of alumina in the composite metal oxide porous body is 30 to 80% by mass;
A step of preparing a second raw material solution containing a polymer dispersant;
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.

(First raw material solution preparation process)
The first raw material solution containing the aluminum ion, cerium ion, and zirconium ion is obtained by dissolving an aluminum compound, a cerium compound, a zirconium compound, and, if necessary, another metal compound in a solvent. It is done.

  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 0.5 mol / L, and 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. On the other hand, when the cation concentration exceeds the upper limit, the crystallites of the metal compound in the colloidal solution and / or aggregates thereof (hereinafter referred to as the cation concentration). 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.

(Second raw material solution preparation step)
The second raw material solution containing the polymer dispersant includes a polymer dispersant and, if necessary, an ammonium salt (ammonium acetate, ammonium nitrate, etc.), an animonia water, an acid (acetic acid, nitric acid, etc.), a hydrogen peroxide solution. Etc. are dissolved in a solvent. As the polymer dispersant, polyalkyleneimine, polyacrylic acid, polyvinylpyrrolidone, and polyethylene glycol are preferable, and from the viewpoint that high dispersion performance can be exhibited in the liquid, polyalkyleneimine and polyacrylic acid are more preferable, Polyalkyleneimine is particularly preferred from the viewpoint that the colloidal solution obtained under pH conditions is particularly excellent in storage stability.

  The weight average molecular weight of the polyalkyleneimine is preferably 3000 to 15000, and more preferably 8000 to 12000. When the weight average molecular weight of the polyalkyleneimine is within 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 polyalkyleneimine is less than the lower limit, even if the polyalkyleneimine is adsorbed to the metal compound fine particles, the repulsive force due to steric hindrance is not sufficiently expressed, and the metal compound fine particles tend to aggregate, If the upper limit is exceeded, the polyalkyleneimine tends to form a crosslinked structure and 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 polyalkyleneimine in the second raw material solution is such that the content of the polyalkyleneimine in the resulting colloidal solution is 5 to 35 mg / m ² (more preferably 5 to the unit surface area of the crystallite of the metal compound). It is preferable to adjust so that it may become -15mg / m < ² >). When the polyalkyleneimine content in the colloidal solution falls within the above range, the metal compound crystallites are dispersed in a state of uniform aggregates with a small diameter, and a colloidal solution having excellent storage stability can be obtained. On the other hand, when the polyalkyleneimine content in the colloidal solution is less than the lower limit, the surface of the metal compound fine particles cannot be sufficiently covered with the polyalkyleneimine, and the metal compound fine particles aggregate to form larger aggregates. On the other hand, when the above upper limit is exceeded, a large amount of free polyalkyleneimine is present in the colloidal solution, so that the cross-linking reaction of polyalkyleneimine proceeds remarkably and aggregates having a large particle size are formed. There is a tendency.

  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 an acid to the colloid solution obtained in the colloid solution preparation step, but in advance so that the colloid solution obtained in the colloid solution preparation step has a pH of 3 to 5. It is preferable to add an acid to at least one of the first and second raw material solutions.

(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 tends 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 pores 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 is 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, so that the sintering proceeds when the catalyst is used, and the catalytic activity is significantly reduced. On the other hand, when the temperature exceeds the upper limit, the specific surface area is decreased, the total pore volume is decreased, and as a result, the catalytic activity is decreased. Moreover, as such heat processing temperature, it is especially preferable that it is 800-1050 degreeC from a viewpoint that the more outstanding catalyst activity 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 transition metal on the surface of an exhaust gas purification catalyst carrier obtained by the production method of the present invention. The specific method for supporting such a transition metal is not particularly limited. For example, a solution obtained by dissolving a transition metal salt (nitrate, chloride, acetate, etc.) or a transition metal complex in a solvent such as water or alcohol. A method is preferably used in which the exhaust gas-purifying catalyst carrier is dipped in, the solvent is removed, and the mixture is fired and pulverized. In the step of supporting the transition metal, the drying condition for removing the solvent is preferably within 30 minutes at 30 to 150 ° C. The firing condition is 250 in an oxidizing atmosphere (for example, air). It is preferably about 30 to 180 minutes at ~ 600 ° C. Further, such a transition metal supporting step may be repeated until a desired amount is supported.

  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, 9.32 g of ammonium cerium nitrate, 1.94 g of zirconyl oxynitrate, 1.1 g of yttrium nitrate, and 27.38 g of aluminum nitrate are dissolved in 500 g of ion-exchanged water and contain a cation that is a raw material for the composite metal oxide. A raw material solution 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 = 47.39: 37.32: 11.45: 3.85 (mass ratio). Equivalent to. 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)
In the same manner as in Example 1, a metal compound nanocolloid solution (pH 4) was prepared. Ethylenediamine was quickly added to the nanocolloid solution while propeller stirring (300 rpm) to adjust the pH to 7, and a cloudy suspension was obtained. 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.

(Example 3)
In the same manner as in Example 1, a metal compound nanocolloid solution (pH 4) was prepared. Triethanolamine was quickly added to the nanocolloid solution while stirring with a propeller (300 rpm) to adjust the pH to 7, and a cloudy suspension was obtained. 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)
A transparent nanocolloid solution of a metal compound (pH 1) in the same manner as in Example 1 except that 32.22 g of ammonium nitrate, 62.5 g of polyethyleneimine, and 115 g of nitric acid were dissolved in 323 g of ion-exchanged water. ) Was prepared. 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 cloudy 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 2)
In the same manner as in Example 1, 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 and Comparative Examples by an automatic specific surface area / pore distribution measuring device (trade name “Autosorb-1” manufactured by Cantachrome Co., Ltd.) and a constant volume gas adsorption method at a liquid nitrogen temperature (−196 ° C.) The nitrogen adsorption isotherm of the composite metal oxide porous material powder obtained in step 1 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 Table 1.

  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 Table 1.

<Average crystallite size>
An X-ray diffraction (XRD) pattern of the composite metal oxide porous powder (before heat treatment at a high temperature) obtained in Examples and Comparative Examples was converted into a powder X-ray diffractometer (trade name “RINT-2200” manufactured by Rigaku Corporation). Is used 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, and zirconia solid solution ceria particles (CZ particles). From the half width of the peak derived from the (111) plane of), 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 Table 1.

(Heat treatment of composite metal oxide porous body at high temperature)
The composite metal oxide porous powders obtained in Examples and Comparative Examples 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 Table 1.

<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 2 (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 Table 1. 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)
Using an aqueous copper nitrate solution prepared by dissolving 0.951 g of copper nitrate (Cu (NO ₃ ) ₂ .3H ₂ O) in 100 g of ion-exchanged water, 5 g of the composite metal oxide porous powder obtained in Examples and Comparative Examples Then, copper was supported so as to be 0.25 g and calcined in air at 600 ° C. for 5 hours to obtain a Cu-supported composite metal oxide porous material powder. This powder was molded at 1000 kgf / cm ² using a cold isostatic press, and then pulverized to obtain a pellet-shaped Cu-supported catalyst having a diameter of 0.5 to 1 mm.

<Durability test>
2 g of the obtained Cu-supported catalyst was filled in a quartz reaction tube, and a 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 900 ° 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 catalytic activity>
1 g of the Cu-supported catalyst after the durability test was placed in an atmospheric pressure fixed bed flow type reaction apparatus (manufactured by Vest Sokki Co., Ltd.), CO (0.7 vol%), H ₂ (0.23 vol%), NO (0.12% by volume), C ₃ H ₆ (0.16% by volume), O ₂ (0.64% by volume), CO ₂ (10% by volume), H ₂ O (3% by volume) and N ₂ ( The model gas consisting of the remainder was supplied at a flow rate of 3500 mL / min, adjusted so that the gas temperature with catalyst became 100 ° C., and the CO concentration and NO concentration of the gas with catalyst were measured. Thereafter, while increasing the temperature of the gas containing the catalyst to 600 ° C. at a temperature increase rate of 15 ° C./min, the CO concentration and the NO concentration of the catalyst output gas are measured, and the measured values of the catalyst input gas and the catalyst output gas are measured. The CO purification rate and the NO purification rate were calculated from the difference. Then, the temperatures (T50-CO and T50-NO) at which the CO purification rate and the NO purification rate in the supplied model gas reached 50% were measured. The results are shown in Table 1.

<Specific surface area>
The BET specific surface area of the Cu-supported catalyst after the durability test was calculated according to the above method. The results are shown in Table 1.

  As can be seen from the results shown in Table 1, the composite metal oxide porous bodies obtained in Examples 1 to 3 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). Further, as shown in FIG. 5, the composite metal oxide porous body after the heat treatment at high temperature has mesopores (primary pores) having a pore diameter of 1 nm to 0.1 μm formed between primary particles. And macropores (secondary pores) with a pore diameter of 0.1 μm to 10 μm formed between secondary particles, and the total pore volume of the mesopores and the macropores are compared It was confirmed to be a big one. 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.

  Further, by using such a composite metal oxide porous body as a carrier, a transition metal-supported catalyst (exhaust gas) exhibiting high catalytic activity from a relatively low temperature of 375 ° C. or lower even after endurance treatment (900 ° C., 5 hours). It was confirmed that a purification catalyst) was obtained. In particular, when the nanocolloid solution is adjusted to pH 7 using ethylenediamine or triethanolamine (Examples 2 to 3), the pH is adjusted to 9 using aqueous ammonia (Comparative Example 1), and the polymer dispersant The transition metal-supported catalyst after the endurance test has a higher catalytic activity from a lower temperature than when a pH 10 nanocolloid solution was prepared using ammonia water as the second raw material solution (comparative example 2). showed that. The reason is presumed as follows. That is, in the composite metal oxide porous bodies obtained in Comparative Examples 1 and 2, the total pore volume of the macropores is reduced by the heat treatment at a high temperature, and the mutual fine dispersion degree between the alumina particles and the CZ particles is reduced. From the decrease, it is presumed that alumina did not function sufficiently as a diffusion barrier for CZ particles. This is because in the composite metal oxide porous body obtained in Comparative Example 1, the nanocolloid solution was adjusted to pH 9 using aqueous ammonia, and also in the composite metal oxide porous body obtained in Comparative Example 2. In the obtained composite metal oxide porous body, by preparing a nanocolloid solution having a pH of 10 using aqueous ammonia, alumina particles are aggregated, and the mutual fine dispersion of alumina, ceria and zirconia is high. It is guessed that it decreased. Even in the transition metal supported catalyst, the aggregated alumina particles did not sufficiently function as a diffusion barrier for the CZ particles. Therefore, the CZ particles grew as a result of the durability test, and the transition metal became the alumina particles and the CZ particles. Since it is in a non-uniformly supported state (specifically, the state in which the transition metal supported on these particles grows with the growth of CZ particles), the interaction between the transition metal and the CZ particles is sufficient. It is assumed that the catalytic activity after the durability test was lowered.

  On the other hand, in the composite metal oxide porous body obtained in Examples 2-3, the total pore volume of the macropores is relatively large even after the heat treatment at high temperature, and the alumina particles and the CZ particles The mutual fine dispersion was also high. From this, it is surmised that the composite metal oxide porous bodies obtained in Examples 2 to 3 functioned satisfactorily as the diffusion barrier of the CZ particles in the highly finely dispersed alumina particles in the heat treatment at high temperature. . This is presumably due to the adjustment of the nanocolloid solution to pH 7 using ethylenediamine or triethanolamine in the composite metal oxide porous bodies obtained in Examples 2-3. Also in the transition metal supported catalyst, the highly finely dispersed alumina particles functioned sufficiently as a diffusion barrier for the CZ particles, so that a high degree of mutual fine dispersion between the alumina particles and the CZ particles is maintained even when the durability test is performed. It is presumed that the transition metal supported on these particles was kept finely and uniformly dispersed, and excellent catalytic activity was obtained even after the durability test.

  As described above, according to the present invention, an exhaust gas purifying catalyst capable of obtaining a transition metal-supported catalyst exhibiting excellent catalytic activity, particularly, high catalytic activity from a relatively low temperature, even when exposed to high temperatures. It is possible to provide a carrier 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 (7)

Containing alumina, ceria and zirconia, comprising a composite metal oxide porous body having an alumina content of 30 to 80% by mass,
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 19 or less. A catalyst carrier for exhaust gas purification characterized. 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. 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 not less than 18 cm ³ / g and not less than 0.3 cm ³ / g 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 was determined by the energy dispersive X-ray analysis, and the content of cerium element and zirconium element in 100 minute regions (unit: at 3. The exhaust gas purifying catalyst carrier according to claim 1 or 2, characterized in that all the standard deviations of%) are 15 or less.   An exhaust gas purification catalyst comprising the exhaust gas purification catalyst carrier according to any one of claims 1 to 3 and a transition metal supported on the catalyst carrier.   The exhaust gas purifying catalyst according to claim 4, wherein the transition metal is copper. A method for producing a catalyst carrier for exhaust gas purification comprising a porous composite metal oxide containing alumina, ceria and zirconia,
Preparing a first raw material solution containing aluminum ions, cerium ions, and zirconium ions so that the content of alumina in the composite metal oxide porous body is 30 to 80% by mass;
A step of preparing a second raw material solution containing a polymer dispersant;
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,
Preparing a first raw material solution containing aluminum ions, cerium ions, and zirconium ions so that the content of alumina in the composite metal oxide porous body is 30 to 80% by mass;
A step of preparing a second raw material solution containing a polymer dispersant;
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.