JP6615060B2 - Method for producing catalyst carrier for exhaust gas purification - 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.

  Conventionally, as a catalyst for exhaust gas purification for purifying gas containing harmful substances discharged from internal combustion engines such as automobiles, a composite made of alumina, titania, silica, zirconia, ceria, etc. with noble metals such as platinum, rhodium and palladium Three-way catalysts supported on metal oxide supports are widely known. As a method for producing a catalyst carrier comprising such a composite metal oxide, a powder mixing method, a coprecipitation method, and the like are known. However, a catalyst carrier produced by these methods is not necessarily sufficient in heat resistance. However, the oxygen storage capacity sometimes deteriorated when exposed to high temperatures. For this reason, a catalyst carrier made of a composite metal oxide having more excellent heat resistance has been demanded.

  For example, in International Publication 2011/030875 (Patent Document 1), a raw material solution containing an aluminum ion and a raw material solution containing a polymer dispersant are directly and independently provided in a region having a predetermined high shear rate. A first colloidal solution is prepared by introducing and homogeneously mixed, and a raw material solution containing zirconium ions and a raw material solution containing a polymer dispersant are added to a region having a predetermined high shear rate. A second colloidal solution was prepared by direct introduction independently and homogeneously mixed, and the obtained first colloidal solution and the second colloidal solution were mixed under a predetermined pH condition to prepare a colloidal solution. Thereafter, an aggregate is prepared by adjusting the pH of the colloidal solution to a predetermined condition, and the aggregate is heat-treated to obtain first ultrafine particles containing alumina. A composite metal oxide porous body in which the second ultrafine particles containing luconia are uniformly mixed with extremely high dispersibility is obtained. This composite metal oxide porous body has high catalytic activity and high temperature durability. It is described as being useful as a catalyst support resulting in an ideal catalyst realized at the standard. However, even in such a composite metal oxide porous body, the heat resistance is not always sufficient, and when exposed to high temperatures, the dispersibility of the metal element may decrease and the oxygen storage capacity may decrease. It was.

  JP-A-2014-24058 (Patent Document 2) discloses a first raw material solution containing aluminum ions, cerium ions and zirconium ions, and a second raw material solution containing a polymer dispersant. Prepare a colloidal solution of a metal compound by directly introducing it into a region with a predetermined high shear rate and mixing it homogeneously, and adjust the pH of the obtained colloidal solution to a predetermined condition. This is a composite in which alumina, ceria, and zirconia are finely and evenly dispersed with each other even when exposed to high temperatures by heat treatment in an oxidizing atmosphere after adding an organic amine and gelling. A metal oxide porous body is obtained, and this composite metal oxide porous body is useful as a catalyst support exhibiting excellent oxygen storage ability even when exposed to high temperatures. There has been described. However, even in such a composite metal oxide porous body, the heat resistance is not always sufficient, and when exposed to high temperature for a long time, the specific surface area is greatly reduced or the pore diameter is greatly increased. For this reason, the catalyst in which a noble metal is supported on the composite oxide porous body has a low oxygen release rate, and may not be able to quickly cope with a transient change in oxygen partial pressure around the catalyst.

International Publication No. 2011/030875 JP 2014-24058 A

  The present invention has been made in view of the above-mentioned problems of the prior art, and has a high oxygen release rate (OSC-r) even when exposed to high temperatures for a long time (for example, 1100 ° C. for 50 hours). It is an object of the present invention to provide an exhaust gas purifying catalyst, an exhaust gas purifying catalyst carrier capable of forming such a catalyst, and a method for producing the same.

  As a result of intensive studies to achieve the above object, the present inventors have neutralized a first raw material solution containing aluminum ions, cerium ions and zirconium ions and a second raw material solution containing hydrogen peroxide. By introducing the third raw material solution containing the agent directly into the region where the shear rate is high and mixing it homogeneously, each metallic element is mutually fine and uniform (that is, high mutual fine dispersion). Catalyst support for exhaust gas purification comprising a composite metal oxide porous body that has a reduced specific surface area and a small increase in pore diameter even when exposed to high temperatures (for example, 1100 ° C.) The exhaust gas-purifying catalyst having a noble metal supported on the catalyst carrier exhibits a high oxygen release rate (OSC-r) even when exposed to a high temperature for a long time (for example, 1100 ° C. for 50 hours). This The heading, which resulted in the completion of the present invention.

The method for producing the exhaust gas purifying catalyst carrier of the present invention comprises:
Preparing a first raw material solution containing aluminum ions, cerium ions and zirconium ions;
Preparing a second raw material solution containing hydrogen peroxide;
Preparing a third raw material solution containing a neutralizing agent;
A step of obtaining a metal compound nano-slurry by directly and independently introducing the first raw material solution, the second raw material solution, and the third raw material solution independently into a region having a shear rate of 5000 to 40000 sec ^−1. When,
Degreasing the nanoslurry and heating in an oxidizing atmosphere to obtain a composite metal oxide porous body containing alumina, ceria and zirconia;
It is the method characterized by including. Here, the value of the shear rate according to the present invention is a value calculated on the assumption that the flow in a predetermined region (reaction field) is a laminar flow.

  In such a method for producing an exhaust gas purifying catalyst carrier of the present invention, the third raw material solution preferably further contains a dispersant (more preferably a dicarboxylic acid), and the second raw material solution It is preferable that the raw material solution further contains glycerol, and further, the first raw material solution further contains at least one metal ion selected from the group consisting of lanthanum ions and yttrium ions. Is preferred.

  Moreover, in the manufacturing method of the exhaust gas purifying catalyst carrier of the present invention, 47 to 65 mol% is chloride ion and 35 to 53 mol% is nitrate ion among all counter anions in the first raw material solution. It is preferable that

  The reason why the exhaust gas purification catalyst of the present invention exhibits a high oxygen release rate (OSC-r) even when it is exposed to a high temperature for a long time (for example, 50 hours at 1100 ° C.) is not necessarily clear, The present inventors infer as follows. That is, in the exhaust gas purifying catalyst carrier of the present invention, each metal element is dispersed finely and uniformly (that is, with a high degree of mutual fine dispersion) and is exposed to a high temperature (eg, 1100 ° C.). Even if it is a case, it is comprised with the composite metal oxide porous body with a small fall of a specific surface area and a small increase in a pore diameter. In the exhaust gas purifying catalyst of the present invention, noble metal is supported on such a composite metal oxide porous body, and even when exposed to high temperatures for a long time (for example, 1100 ° C. for 50 hours) Since the decrease in the specific surface area and the increase in the pore diameter of the metal oxide porous body are small, it is presumed that noble metal sintering hardly occurs and the high dispersibility of the noble metal on the catalyst support is maintained. For this reason, it is speculated that the exhaust gas purifying catalyst of the present invention exhibits a high oxygen release rate (OSC-r) even when exposed to high temperatures for a long time (for example, at 1100 ° C. for 50 hours).

  According to the present invention, an exhaust gas purifying catalyst showing such a high oxygen release rate (OSC-r) even when exposed to a high temperature for a long time (for example, at 1100 ° C. for 50 hours), such a catalyst is formed. It is possible to obtain an exhaust gas purifying catalyst carrier that can be used.

It is a schematic cross-sectional view which shows one suitable embodiment of the manufacturing apparatus of the nano slurry used for this invention. FIG. 2 is an enlarged longitudinal sectional view showing a tip portion (stirring portion) of the outer nozzle type homogenizer 10 shown in FIG. 1. It is a cross-sectional view of the front-end | tip part (stirring part) of the outer nozzle type homogenizer 10 shown in FIG. It is a schematic cross section which shows an example of the manufacturing apparatus of the conventional colloidal solution. FIG. 5 is an enlarged longitudinal sectional view showing a tip portion (stirring portion) of the inner nozzle type homogenizer 40 shown in FIG. 4. It is a side view of the inner side stator 43 shown in FIG. FIG. 5 is a transverse sectional view of an inner stator 43 shown in FIG. 4.

  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 comprises a composite metal oxide porous body containing alumina, ceria and zirconia. Such a composite metal oxide porous body is preferably a mixture of first ultrafine particles containing alumina and second ultrafine particles containing ceria and zirconia. Is preferably zirconia solid-solution ceria ultrafine particles. A catalyst in which a noble metal is supported on a catalyst carrier made of such a composite metal oxide porous body is excellent in heat resistance. The “ultrafine particles” used herein refer to primary particles of metal oxide or composite metal oxide crystallites or minute secondary particles composed of aggregates of several crystallites. The composite metal oxide porous body according to the present invention is composed of an aggregate of ultrafine particles obtained by aggregating these ultrafine particles at intervals.

Further, the composite metal oxide porous body includes oxides and alkaline earths of rare earth elements other than Ce (La, Pr, Y, Sc, etc.) from the viewpoint of improving the heat resistance of the catalyst supporting the noble metal. It is preferable that at least one other metal oxide selected from the group consisting of oxides of similar metals (Sr, Ca, Ba, etc.) is further included, and the oxygen storage capacity and heat resistance of the catalyst are further increased. From the viewpoint of improving, it is more preferable that at least one of yttria (Y ₂ O ₃ ) and lantana (La ₂ O ₃ ) is further included, and yttria (Y ₂ O ₃ ) is further included. It is particularly preferable. The content of such other metal oxides is appropriately set so as to obtain the effect. For example, in the case of lantana (La ₂ O ₃ ), 2.5 atomic% or less in terms of lanthanum atoms. In the case of yttria (Y ₂ O ₃ ), it is preferably 2.0 atomic% or less in terms of yttrium atoms. When the content of Lantana (La ₂ O ₃ ) or yttria (Y ₂ O ₃ ) exceeds the above upper limit, not only the heat resistance improvement effect is improved, but the content of zirconia solid solution ceria which is a main constituent component is reduced. There is a tendency for negative factors to stand out.

When the composite metal oxide porous body is a mixture of the first ultrafine particles and the second ultrafine particles, the rare earth element and alkaline earth metal other than Ce are the first ultrafine particles and the second ultrafine particles. Oxygen storage capacity and heat resistance of a catalyst in which a noble metal is supported on a catalyst carrier made of such a composite metal oxide porous body may be contained in one or both of the ultrafine particles. From the viewpoint of further improving the properties, it is preferable that at least one of yttria (Y ₂ O ₃ ) and lantana (La ₂ O ₃ ) is further included in at least the second ultrafine particles. Y ₂ O ₃₎ is more preferably is further included, the second ultrafine particles _{CeO 2 -ZrO 2 -Y 2 O 3} 3 -component composite metal oxide and _{CeO 2} -ZrO 2 -La 2 O ₃ Ternary duplex A mixed metal oxide is more preferable, and a CeO ₂ —ZrO ₂ —La ₂ O ₃ —Y ₂ O ₃ quaternary composite metal oxide is particularly preferable. Further, the first ultrafine particles may further contain lantana (La ₂ O ₃ ).

  When the first ultrafine particles are a composite metal oxide or a metal oxide mixture containing alumina and another metal oxide, the content of alumina in the first ultrafine particles is preferably 30 mol% or more. When the second ultrafine particles are a composite metal oxide or a metal oxide mixture containing ceria, zirconia and other metal oxides, the ceria content in the second ultrafine particles is 30 mol% or more. It is preferable that the content of zirconia is 30 mol% or more.

When the composite metal oxide porous body is a mixture of the first ultrafine particles and the second ultrafine particles, the mixing ratio of the first ultrafine particles and the second ultrafine particles is not particularly limited, but the resulting mixture It is preferable that the content ratio of alumina in the mixture is 30 to 70% by volume (corresponding to 22 to 61% by mass in terms of the mass ratio of Al ₂ O ₃ ). When the content of alumina is less than the lower limit, the function of alumina as a diffusion barrier tends to be reduced. On the other hand, a catalyst in which a noble metal is supported on a catalyst carrier having an alumina content exceeding the upper limit tends to have smaller functions due to ceria and zirconium such as oxygen storage ability and stable adsorption ability of the noble metal.

  The catalyst carrier for exhaust gas purification of the present invention is an energy dispersive X using a scanning transmission electron microscope with a spherical aberration correction function for all metal elements contained in the composite metal oxide porous body in an amount of 0.1% by mass or more. A condition that the standard deviation of the content of each metal element obtained by measuring the content (mass%) of the metal element in a minute analysis range of 20 nm square by line spectroscopic analysis at 100 measurement points is 10 or less. It satisfies. In addition, it means that each metal element is disperse | distributing finely and uniformly mutually (namely, mutual fine dispersion degree is high), so that the value of the standard deviation of the content rate of this metal element is small. A catalyst carrier that satisfies such conditions, that is, a catalyst for purifying an exhaust gas in which a noble metal is supported on a catalyst carrier in which each metal element is dispersed with a high degree of mutual fine dispersion, is exposed to high temperatures (for example, 1100 ° C. for 5 hours). Even if it is, it has an excellent oxygen storage capacity, in particular, exhibits a high oxygen release rate (OSC-r), and can respond quickly to transient changes in oxygen partial pressure around the catalyst. it can. On the other hand, a catalyst in which a noble metal is supported on a catalyst carrier in which the standard deviation of the content of each metal element exceeds the upper limit has a reduced oxygen storage capacity when exposed to a high temperature (eg, 1100 ° C. for 5 hours). The oxygen release rate (OSC-r) is low, and it is not possible to quickly cope with a transient change in the oxygen partial pressure around the catalyst.

  Such a standard deviation is specifically obtained by the following method. That is, first, using a scanning transmission electron microscope equipped with a spherical aberration correction device (“JEM-2100F-Cs collector” manufactured by JOEL) equipped with an energy dispersive X-ray analyzer (EDS), the composite metal oxide porous STEM observation of the body is performed, and further, EDS mapping is performed on all the metal elements contained in the composite metal oxide porous body in an amount of 0.1 mass% or more. In the obtained EDS mapping image, the content of each metal element within a 20 nm square microanalysis range is determined. The content of this metal element is determined for 100 measurement points (20 nm square microanalysis range) extracted at random. The standard deviation of the content rate of each metal element is calculated by using the content rate of each metal element obtained from the charged amount or the content rate of each metal element obtained by ICP emission spectroscopic analysis as the average content rate.

In the exhaust gas purification catalyst carrier of the present invention, the specific surface area (BET specific surface area) of the composite metal oxide porous body determined by the BET method from the nitrogen adsorption isotherm is 30 m ² / g or more. An exhaust gas purifying catalyst in which a noble metal is supported on a catalyst carrier that satisfies such conditions exhibits a high oxygen release rate (OSC-r) and a saturated oxygen storage amount (OSC-c). On the other hand, a catalyst in which a noble metal is supported on a catalyst carrier whose specific surface area of the composite metal oxide porous body is less than the lower limit has a low oxygen release rate (OSC-r) and a saturated oxygen storage amount (OSC-c). Further, from the viewpoint of obtaining an exhaust gas purifying catalyst showing a higher oxygen release rate (OSC-r) and saturated oxygen storage amount (OSC-c), the BET specific surface area of the composite metal oxide porous body is 35 m ^2. / G or more is preferable, and 40 m ² / g or more is more preferable. In addition, although there is no restriction | limiting in particular as an upper limit of the BET specific surface area of the said composite metal oxide porous body, It is preferable that it is 200 m < ² > / g or less.

  Furthermore, in the exhaust gas purifying catalyst carrier of the present invention, the reduction rate of the specific surface area (BET specific surface area) of the composite metal oxide porous body by firing at 1100 ° C. for 5 hours in the air is 50% or less. A catalyst carrier that satisfies such conditions is excellent in heat resistance because the change in the aggregate structure of the microcrystals and the aggregates of microcrystals due to firing at a high temperature is small. Therefore, such an exhaust gas purifying catalyst having a noble metal supported on such a catalyst carrier has a high oxygen release rate (OSC-r) even when exposed to high temperatures for a long time (for example, at 1100 ° C. for 50 hours). Indicates. On the other hand, in the catalyst carrier in which the reduction rate of the specific surface area of the composite metal oxide porous body exceeds the upper limit, the aggregate structure of the microcrystals and the aggregates of the microcrystals is changed by firing at a high temperature, and the heat resistance decreases. To do. For this reason, a catalyst in which a noble metal is supported on such a catalyst carrier exhibits a relatively high oxygen release rate (OSC-r) when exposed to a high temperature (for example, 1100 ° C. for 5 hours), but at a high temperature. When exposed for a long time (for example, at 1100 ° C. for 50 hours), the oxygen release rate (OSC-r) decreases. Further, from the viewpoint of obtaining an exhaust gas purifying catalyst exhibiting a higher oxygen release rate (OSC-r) even when exposed to a high temperature for a long time (for example, at 1100 ° C. for 50 hours), the composite metal The reduction rate of the specific surface area (BET specific surface area) of the oxide porous body is preferably 40% or less.

In the exhaust gas purifying catalyst carrier of the present invention, the following conditions:
Reducing atmosphere (rich atmosphere): H ₂ (2% by volume) + CO ₂ (10% by volume) + H ₂ O (3% by volume) + N ₂ (remainder), 1 atmosphere oxidizing atmosphere (lean atmosphere): O ₂ (1% by volume) ) + CO ₂ (10% by volume) + H ₂ O (3% by volume) + N ₂ (remainder) While alternately switching a reducing atmosphere (R) of 1 atm and an oxidizing atmosphere (L) every 5 minutes (hereinafter referred to as this The atmosphere is abbreviated as “R / L atmosphere.”) The reduction rate of the specific surface area (BET specific surface area) of the composite metal oxide porous body by heating at 1100 ° C. for 5 hours is 55% or less. A catalyst carrier that satisfies such conditions is excellent in heat resistance because the change in the aggregate structure of microcrystals and aggregates of microcrystals due to heating at a high temperature (for example, 1100 ° C. for 5 hours) in an R / L atmosphere is small. ing. Therefore, such an exhaust gas purifying catalyst having a noble metal supported on such a catalyst carrier has a high oxygen release rate (OSC-r) even when exposed to high temperatures for a long time (for example, at 1100 ° C. for 50 hours). Indicates. On the other hand, in the catalyst support in which the reduction rate of the specific surface area of the composite metal oxide porous body exceeds the upper limit, the aggregate structure of the microcrystals and the aggregates of microcrystals has a high temperature (for example, at 1100 ° C.) in an R / L atmosphere. 5 hours), the heat resistance decreases. For this reason, a catalyst in which a noble metal is supported on such a catalyst carrier exhibits a relatively high oxygen release rate (OSC-r) when exposed to a high temperature (for example, 1100 ° C. for 5 hours), but at a high temperature. When exposed for a long time (for example, at 1100 ° C. for 50 hours), the oxygen release rate (OSC-r) decreases.

  Furthermore, in the exhaust gas purifying catalyst carrier of the present invention, the composite metal oxidation by heating at 1100 ° C. for 50 hours while alternately switching the reducing atmosphere (R) and oxidizing atmosphere (L) under the above conditions every 5 minutes. The reduction rate of the specific surface area (BET specific surface area) of the porous object is 80% or less. A catalyst carrier that satisfies such conditions has a small change in the aggregate structure of microcrystals and aggregates of microcrystals due to heating at high temperatures for a long time (for example, 1100 ° C. for 50 hours) in an R / L atmosphere, and is heat resistant. Is excellent. Therefore, such an exhaust gas purifying catalyst having a noble metal supported on such a catalyst carrier has a high oxygen release rate (OSC-r) even when exposed to high temperatures for a long time (for example, at 1100 ° C. for 50 hours). Indicates. On the other hand, the catalyst support in which the reduction rate of the specific surface area of the composite metal oxide porous body exceeds the upper limit is such that the aggregate structure of the microcrystals and the aggregates of the microcrystals is a long time at a high temperature in an R / L atmosphere (for example, It is changed by heating at 1100 ° C. for 50 hours, and the heat resistance is lowered. For this reason, a catalyst in which a noble metal is supported on such a catalyst carrier exhibits a relatively high oxygen release rate (OSC-r) when exposed to a high temperature (for example, 1100 ° C. for 5 hours), but at a high temperature. When exposed for a long time (for example, at 1100 ° C. for 50 hours), the oxygen release rate (OSC-r) decreases. Further, from the viewpoint of obtaining an exhaust gas purifying catalyst exhibiting a higher oxygen release rate (OSC-r) even when exposed to a high temperature for a long time (for example, at 1100 ° C. for 50 hours), the composite metal The reduction rate of the specific surface area (BET specific surface area) of the oxide porous body is preferably 75% or less.

In the present invention, the rate of decrease of the specific surface area due to the firing or heating is determined according to the following formula.
Reduction ratio (%) of specific surface area = (specific surface area before firing (or heating) −specific surface area after firing (or heating)) / specific surface area before firing (or heating) × 100.

  Further, in the exhaust gas purifying catalyst carrier of the present invention, the maximum frequency pore diameter in the differential pore volume distribution of the composite metal oxide porous body obtained from the nitrogen adsorption isotherm by the BJH method is 0.001 to 0.2 μm. It is preferable to be within the range. In the present invention, the “maximum frequency pore diameter” means the pore diameter at the peak (peak top) at which the frequency (differential pore volume) is maximum in the differential pore volume distribution. A catalyst carrier that satisfies such a condition tends to be excellent in gas diffusibility in the pores. For this reason, the exhaust gas purifying catalyst having a noble metal supported on such a catalyst carrier tends to exhibit a high oxygen release rate (OSC-r) and a saturated oxygen storage amount (OSC-c). On the other hand, the catalyst carrier in which the maximum frequency pore diameter of the composite metal oxide porous body is less than the lower limit tends to decrease the gas diffusibility in the pores. For this reason, a catalyst in which a noble metal is supported on such a catalyst carrier tends to have a low oxygen release rate (OSC-r) and a saturated oxygen storage amount (OSC-c). On the other hand, the catalyst carrier in which the maximum frequency pore diameter of the composite metal oxide porous body exceeds the upper limit also tends to reduce the gas diffusibility in the pores. For this reason, a catalyst in which a noble metal is supported on such a catalyst carrier tends to have a low oxygen release rate (OSC-r) and a saturated oxygen storage amount (OSC-c).

  Furthermore, in the exhaust gas purifying catalyst carrier of the present invention, it is preferable that the increase rate of the maximum frequency pore diameter of the composite metal oxide porous body by firing at 1100 ° C. for 5 hours in the atmosphere is 90% or less, 75 % Or less is more preferable, and 50% or less is particularly preferable. A catalyst carrier that satisfies such conditions tends to be excellent in heat resistance because the pore structure and the aggregate structure of the microcrystals that form the catalyst carrier are not easily changed by firing at a high temperature. Therefore, such an exhaust gas purifying catalyst having a noble metal supported on such a catalyst carrier has a high oxygen release rate (OSC-r) even when exposed to high temperatures for a long time (for example, at 1100 ° C. for 50 hours). Tend to show. On the other hand, the catalyst carrier in which the increase rate of the maximum frequency pore diameter of the composite metal oxide porous body exceeds the upper limit is such that the pore structure and the agglomeration structure of the microcrystals forming the same are easily changed by firing at high temperature, Tend to decrease. For this reason, a catalyst in which a noble metal is supported on such a catalyst carrier exhibits a relatively high oxygen release rate (OSC-r) when exposed to a high temperature (for example, 1100 ° C. for 5 hours), but at a high temperature. When exposed for a long time (for example, at 1100 ° C. for 50 hours), the oxygen release rate (OSC-r) tends to decrease.

  Further, in the exhaust gas purifying catalyst carrier of the present invention, the composite metal oxidation by heating at 1100 ° C. for 5 hours while alternately switching the reducing atmosphere (R) and oxidizing atmosphere (L) under the above conditions every 5 minutes. The increase rate of the maximum frequency pore diameter of the porous material is preferably 100% or less, more preferably 90% or less, and particularly preferably 80% or less. The catalyst carrier satisfying such conditions is such that the pore structure and the aggregate structure of the microcrystals forming the same are not easily changed by heating at a high temperature (eg, 1100 ° C. for 5 hours) in an R / L atmosphere. It tends to be excellent. Therefore, such an exhaust gas purifying catalyst having a noble metal supported on such a catalyst carrier has a high oxygen release rate (OSC-r) even when exposed to high temperatures for a long time (for example, at 1100 ° C. for 50 hours). Tend to show. On the other hand, the catalyst carrier in which the increase rate of the maximum frequency pore diameter of the composite metal oxide porous body exceeds the upper limit has a pore structure and an agglomerated structure of microcrystals forming the same in an R / L atmosphere at a high temperature (for example, It tends to change due to heating at 1100 ° C. for 5 hours, and the heat resistance tends to decrease. For this reason, a catalyst in which a noble metal is supported on such a catalyst carrier exhibits a relatively high oxygen release rate (OSC-r) when exposed to a high temperature (for example, 1100 ° C. for 5 hours), but at a high temperature. When exposed for a long time (for example, at 1100 ° C. for 50 hours), the oxygen release rate (OSC-r) tends to decrease.

  Furthermore, in the exhaust gas purifying catalyst carrier of the present invention, the composite metal oxidation by heating at 1100 ° C. for 50 hours while alternately switching the reducing atmosphere (R) and oxidizing atmosphere (L) under the above conditions every 5 minutes. The increase rate of the maximum frequency pore diameter of the porous material is preferably 260% or less, more preferably 200% or less, and particularly preferably 150% or less. In the catalyst carrier that satisfies such conditions, the pore structure and the aggregate structure of the microcrystals that form the catalyst carrier are unlikely to change by heating at a high temperature for a long time (eg, 1100 ° C. for 50 hours) in an R / L atmosphere. The heat resistance tends to be excellent. Therefore, such an exhaust gas purifying catalyst having a noble metal supported on such a catalyst carrier has a high oxygen release rate (OSC-r) even when exposed to high temperatures for a long time (for example, at 1100 ° C. for 50 hours). Tend to show. On the other hand, the catalyst carrier in which the increase rate of the maximum frequency pore diameter of the composite metal oxide porous body exceeds the upper limit has a long pore structure and an agglomerated structure of microcrystals forming it at a high temperature in an R / L atmosphere. It tends to change due to heating for a period of time (eg, 1100 ° C. for 50 hours), and the heat resistance tends to decrease. For this reason, a catalyst in which a noble metal is supported on such a catalyst carrier exhibits a relatively high oxygen release rate (OSC-r) when exposed to a high temperature (for example, 1100 ° C. for 5 hours), but at a high temperature. When exposed for a long time (for example, at 1100 ° C. for 50 hours), the oxygen release rate (OSC-r) tends to decrease.

In the present invention, the increasing rate of the maximum frequency pore diameter by the firing or heating is determined according to the following formula.
Increase rate (%) of maximum frequency pore diameter = (maximum frequency pore diameter after firing (or heating) −maximum frequency pore diameter before firing (or heating)) / maximum frequency pore diameter before firing (or heating) × 100 .

  In the exhaust gas purifying catalyst carrier of the present invention, the fine pore diameter of 0.001 to 0.2 μm in the differential pore volume distribution of the composite metal oxide porous body determined by the BJH method from the nitrogen adsorption isotherm. The total pore volume of the pores is preferably 0.2 ml / g or more. A catalyst carrier that satisfies such a condition tends to be excellent in gas diffusibility in the pores. For this reason, the exhaust gas purifying catalyst having a noble metal supported on such a catalyst carrier tends to exhibit a high oxygen release rate (OSC-r) and a saturated oxygen storage amount (OSC-c). On the other hand, a catalyst carrier having a total pore volume of the composite metal oxide porous body that is less than the lower limit tends to have low gas diffusibility in the pores. For this reason, a catalyst in which a noble metal is supported on such a catalyst carrier tends to have a low oxygen release rate (OSC-r) and a saturated oxygen storage amount (OSC-c).

  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 catalyst carrier. In the exhaust gas purifying catalyst of the present invention, the catalyst carrier has each metal element dispersed with a high degree of mutual fine dispersion, and the specific surface area is reduced even when exposed to high temperatures (eg, 1100 ° C.). And a high release rate of oxygen (OSC-r) even when exposed to a high temperature for a long time (for example, 50 hours at 1100 ° C.). Indicates.

  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 a 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 etc.) 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 the exhaust gas purifying catalyst carrier of the present invention comprises:
Preparing a first raw material solution containing aluminum ions, cerium ions and zirconium ions;
Preparing a second raw material solution containing hydrogen peroxide;
Preparing a third raw material solution containing a neutralizing agent;
A step of obtaining a metal compound nano-slurry by directly and independently introducing the first raw material solution, the second raw material solution, and the third raw material solution independently into a region having a shear rate of 5000 to 40000 sec ^−1. When,
And degreasing the nano-slurry and heating in an oxidizing atmosphere to obtain a composite metal oxide porous body containing alumina, ceria and zirconia. According to this method, each metal element is dispersed with a high degree of mutual fine dispersion, and even when exposed to high temperatures (for example, 1100 ° C.), the decrease in specific surface area and the increase in pore diameter are small. The exhaust gas purifying catalyst carrier of the present invention comprising a composite metal oxide porous body can be obtained.

[First raw material solution preparation step]
The first raw material solution containing aluminum ions, cerium ions and zirconium ions (preferably, a raw material solution further containing at least one metal ion selected from the group consisting of lanthanum ions and yttrium ions) is an aluminum compound. Selected from the group consisting of compounds of rare earth elements other than Ce (La, Pr, Y, Sc, etc.) and compounds of alkaline earth metals (Sr, Ca, Ba, etc.) It can be obtained by dissolving in a solvent at least one other metal compound.

As such aluminum compounds, cerium compounds, zirconium compounds and other metal compounds, salts of those metals (acetates, nitrates, chlorides, sulfates, sulfites, inorganic complex salts, etc.) are preferred, and nitrates and chlorides. Nitrate and chloride so that 47 to 65 mol% of chloride ions and 35 to 53 mol% of nitrate ions are out of all counter anions in the first raw material solution. It is particularly preferred to use together. Thereby, the thermal runaway reaction at the time of a degreasing process in case nitrate ion exists excessively is suppressed, and abnormal grain growth is suppressed. On the other hand, in the absence of nitrate ions, the stabilization of Ce ⁴⁺ is insufficient with hydrogen peroxide alone, and the solid solubility of ceria in zirconia decreases. Therefore, it is particularly preferable to adjust the ratio of chloride ions and nitrate ions within the above range.

  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. .

  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 What is necessary is just to adjust 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 0.01 to 0.3 mol / L. Further preferred. When the cation concentration is in the above range, the metal compound crystallites are dispersed in the solvent in the form of uniform aggregates having a small diameter, and a nano slurry 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 metal compound colloid particles tends to decrease, and when it exceeds the upper limit, the metal compound colloid particles tend to further aggregate.

[Second raw material solution preparation step]
The second raw material solution containing hydrogen peroxide can be obtained by dissolving hydrogen peroxide and, if necessary, glycerol in a solvent. In the method for producing a catalyst carrier for exhaust gas purification according to the present invention, hydrogen peroxide functions as an oxidizing agent that changes Ce (III) of cerium chloride or cerium nitrate to Ce (IV), and glycerol increases pore volume. It functions as a pore-forming agent.

  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. .

  The concentration of hydrogen peroxide in the second raw material solution is such that the molar amount of hydrogen peroxide contained in the resulting nanoslurry is equivalent to the cerium ion equivalent contained in the first raw material solution (more preferably, in the first raw material solution). It is preferable to adjust so that the total cation equivalent contained). As a result, the solid solubility of cerium and zirconium is increased, homogeneous zirconia solid solution ceria can be obtained, wasteful consumption of hydrogen peroxide is suppressed, and foaming in the resulting nanoslurry is prevented. Can do.

  The concentration of glycerol in the second raw material solution is 10 parts by mass or more (more preferably 20 parts by mass) with respect to 100 parts by mass of the composite metal oxide porous body finally obtained in the resulting nanoslurry. Part or more) is preferably adjusted. When the glycerol content in the obtained nano-slurry is less than the lower limit, the pore volume of the obtained composite metal oxide porous body tends to be small. However, when the third raw material solution contains an acid as a dispersant, it is not necessary to add this glycerol (the content of glycerol is 0% by mass). Moreover, although there is no restriction | limiting in particular as an upper limit of glycerol content in the obtained nano slurry, From a viewpoint of suppressing the heat_generation | fever (thermal runaway reaction) at the time of a degreasing process, and preventing generation | occurrence | production of high concentration combustible mist, 50 mass parts or less are preferable with respect to 100 mass parts of composite metal oxide porous bodies finally obtained.

[Third raw material solution preparation step]
The 3rd raw material solution containing the said neutralizing agent can be obtained by melt | dissolving a neutralizing agent and a dispersing agent as needed in a solvent. As the neutralizing agent, ammonia is preferable. Examples of the dispersant include monoethanolamine, diethanolamine, triethanolamine, dicarboxylic acid (for example, succinic acid, maleic acid, malonic acid, oxalic acid, glutaric acid, tartaric acid, malic acid), tricarboxylic acid (for example, citric acid). Acid) and the like. Among them, monoethanolamine, diethanolamine, and dicarboxylic acid are preferable, and monoethanolamine, diethanolamine, and maleic acid are more preferable.

  Examples of the solvent used for the third 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. .

The concentration of the neutralizing agent in the third raw material solution is preferably adjusted so that the pH of the resulting nanoslurry is 7.5 or higher (more preferably 8.5 or higher). When the pH of the resulting nano-slurry is less than the lower limit, yttria (Y ₂ O ₃ ), lantana (La ₂ O ₃ ) and the like are not sufficiently precipitated, and segregation tends to be remarkable. The upper limit of the pH of the obtained nanoslurry is not particularly limited, but even if the concentration of the neutralizing agent is increased, the pH of the obtained nanoslurry usually does not exceed 9, so The agent tends to be wasted.

  The concentration of the dispersant in the third raw material solution is 20 to 30 parts by mass with respect to 100 parts by mass of the composite metal oxide porous body finally obtained in the resulting nanoslurry. It is preferable to adjust. When the content of the dispersing agent in the obtained nano-slurry is less than the lower limit, the dispersing agent cannot cover the surface of the colloidal particles and the aggregation of the colloidal particles tends to become remarkable, and the resulting composite metal oxide porous body The pore volume of these tends to be insufficient. On the other hand, when the content of the dispersant in the obtained nano-slurry exceeds the above upper limit, when an amine-based dispersant is used as the dispersant, a lot of viscous tar-like material is generated during the degreasing treatment, and during the degreasing treatment. Inflammable mist is generated at a high concentration and dangerous, and the resulting composite metal oxide porous body tends to have a small specific surface area. When a carboxylic acid dispersant is used, there is no particular inconvenience, Dispersants tend to be wasted.

[Nano slurry preparation process]
In the step of obtaining the nano-slurry, the first raw material solution, the second raw material solution, and the above in a region having a shear rate of 5000 to 40000 sec ⁻¹ (hereinafter referred to as “high shear rate region”). The third raw material solution is directly introduced independently and mixed homogeneously. By such homogeneous mixing, in a state of an aggregate having a smaller metal compound crystallite diameter, uniform and appropriate voids (preferably, alumina (boehmite) ultrafine particles and zirconia solid solution ceria ultrafine particles are mutually It is possible to obtain a metal compound nanoslurry dispersed in a solvent (good).

  Examples of the apparatus used for such a mixing method include the nano-slurry manufacturing apparatus (outer nozzle type super agitation reactor) shown in FIGS. 1 to 3. Is not limited to the method using the nano-slurry manufacturing apparatus shown in FIGS. 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 nano-slurry production apparatus shown in FIG. 1 includes an outer nozzle type homogenizer 10 as a high-speed stirring apparatus, and the tip (stirring part) of the outer nozzle type homogenizer 10 is disposed in the reaction vessel 20. As shown in FIG. 2, the distal end portion of the outer nozzle type homogenizer 10 includes a rotor 11 and an outer stator 12 arranged so that a predetermined gap region is formed between the outer periphery of the rotor 11. However, there is no member (for example, a stator) that obstructs the flow of liquid by forming a predetermined gap region between the inner periphery of the rotor 11 and the inner periphery of the rotor 11. Furthermore, the rotor 11 is connected to a motor 14 via a rotating shaft 13 and can rotate at a high speed.

  In the nano-slurry manufacturing apparatus shown in FIG. 1, as shown in FIGS. 2 and 3, a nozzle 15 </ b> A without branch for introducing the raw material solution A and a nozzle without branch for introducing the raw material solution B are used. 15B and an unbranched nozzle 15C for introducing the raw material solution C are provided on the surface of the outer stator 12 facing the rotor 11 respectively. Here, the “no-branch nozzle” has one inlet and one outlet, and is connected to a raw material solution supply device via a non-branch channel as will be described later. This refers to a nozzle that can discharge the raw material solution supplied from the inlet through the flow path without any branching from the outlet. Further, as shown in FIG. 3, the rotor 11 and the outer stator 12 are provided with slits 11a and 12a. However, no slit is provided between the nozzle 15A and the nozzle 15B of the outer stator 12 and between the nozzle 15A and the nozzle 15C.

  In the nano-slurry manufacturing apparatus shown in FIGS. 1 to 3, the supply device (not shown) of the raw material solution A is connected to the nozzle 15 </ b> A through a flow path 16 </ b> A that is not branched, and the nozzle 15 </ b> B is not flowed A supply device (not shown) for the raw material solution B is connected to the supply device 16 (not shown) via the nozzle 16C, and a supply device (not shown) for the raw material solution C is connected independently to the nozzle 15C via the flow path 16C. The raw material solution A, the raw material solution B, and the raw material solution C can be independently and directly introduced into the region between the rotor 11 and the outer stator 12. Here, the “flow path without branching” is one flow path connecting one raw material solution supply apparatus and one nozzle, and the raw material solution sent out from one raw material solution supply apparatus is It means a flow path that can be supplied to one nozzle without branching along the way. In addition, the nano-slurry manufacturing apparatus shown in FIGS. 1 to 3 does not have a space in which the raw material solution A, the raw material solution B, and the raw material solution C stay in the channel 16A, the channel 16B, and the channel 16C, respectively. Is preferred.

  Further, in the nano-slurry manufacturing apparatus shown in FIG. 1, each nozzle does not have to be arranged in the same plane orthogonal to the rotation axis of the rotor 11 on the surface of the outer stator 12 facing the rotor 11. However, in order to more reliably mix the raw material solution in a short time, as shown in FIGS. 2 and 3, the nozzle 15 </ b> A, the nozzle 15 </ b> B, and the nozzle 15 </ b> C are connected to the rotation axis X of the rotor 11. It is preferable to arrange in the same plane Y orthogonal. 3 is a cross-sectional view of the tip (stirring portion) of the outer nozzle homogenizer 10 on the surface Y in FIG. Further, each nozzle may be arranged in a plurality of rows in a direction along the inner circumference of the outer stator 12 on a plurality of surfaces orthogonal to the rotation axis of the rotor 11 on the surface of the outer stator 12 facing the rotor 11. However, in order to more reliably mix the raw material solution in a short time, as shown in FIGS. 2 and 3, at least one set of nozzles including the nozzle 15A, the nozzle 15B, and the nozzle 15C It is preferable that they are arranged in a line in a direction along the inner circumference of the outer stator 12 on the same surface Y orthogonal to the rotation axis X of the rotor 11.

  In the nano-slurry manufacturing apparatus shown in FIGS. 1 to 3, two sets of nozzles including three nozzles are provided, and the number of nozzles should be set appropriately according to the number of raw material solutions. It is only necessary to install at least as many nozzles without branching as the number of raw material solutions. In addition, at least one nozzle set may be provided, but when the size (diameter) of the outer stator is sufficiently large, it is possible to provide two or more nozzle sets. Thereby, the processing capability of the apparatus can be improved. Furthermore, in order to increase the number of nozzle sets, it is possible to increase the size (diameter) of the rotor and the outer stator.

  The size of the nozzle opening (diameter in the case of a circle and the length of the short axis in the case of an ellipse) is not particularly limited and varies depending on the size of the device. From the viewpoint of more reliably preventing clogging, the thickness is preferably 0.4 to 2 mm. In addition, the distance between adjacent nozzles is not particularly limited and varies depending on the size of the apparatus. However, in order to more reliably mix raw material solutions in a minute time, adjacent nozzle holes It is preferable that it is 0-10 mm in the distance between, and a smaller value is especially preferable among the said ranges.

In the method of manufacturing the exhaust gas purifying catalyst carrier of the present invention, the raw material solution A, the raw material solution B, and the raw material solution C are respectively formed from the nozzle 15A, the nozzle 15B, and the nozzle 15C of the nano-slurry manufacturing apparatus shown in FIGS. In a region to be introduced, that is, a region between the outer periphery of the rotor 11 and the inner periphery of the outer stator 12 in the nano-slurry manufacturing apparatus illustrated in FIGS. 1 to 3, the shear rate may be 5000 to 40000 sec ^−1. It is particularly preferable that the shear rate is 10,000 to 40,000 sec ⁻¹ . When the shear rate in such a region is less than the lower limit, it is difficult to rapidly mix the raw material solution in a minute time, and it contains sufficiently fine and highly uniform colloidal particles or colloidal particle aggregates. It becomes difficult to obtain a colloidal solution or nanoslurry. The shear rate is a value calculated on the assumption that the flow in the predetermined gap region is a laminar flow.

  The conditions for forming such a high shear rate region are affected by the rotational speed of the rotor and the size of the gap between the rotor and the outer stator, so that the shear rate of the region satisfies the above condition. You need to set them. The specific rotation speed of the rotor 11 is not particularly limited and varies depending on the size of the apparatus. Therefore, the lower limit of the peripheral speed of the rotation speed of the rotor 11 is not particularly limited, but generally it is preferably 3 m / sec or more. Also, the upper limit is not particularly limited and is preferably as large as possible. However, it is more preferably in a range in which boil-in, bubble overload, and boiling due to solution overheating do not occur.

  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 0.25 to 0.5 mm. When the outer nozzle type homogenizer is enlarged in a similar shape, it is preferable to increase the size of the cap by the ratio.

  Further, in the nano-slurry manufacturing apparatus shown in FIGS. 1 to 3, the raw material solution A, the raw material solution B, and the raw material solution C respectively supplied from the nozzle 15A, the nozzle 15B, and the nozzle 15C are in the high shear rate region. It is preferable that the nozzle 15A, the nozzle 15B, and the nozzle 15C are arranged so as to be homogeneously mixed within 1 msec (particularly preferably within 0.3 msec) after the introduction. Here, the time from when the raw material solution is introduced into the high shear rate region until it is homogeneously mixed is, for example, in FIG. 3, the raw material solution A introduced from the nozzle 15A is adjacent to the adjacent nozzle 15B. After reaching the position and being mixed with the raw material solution B introduced from the nozzle 15B, it further means the time from reaching the position of the adjacent nozzle 15C and being mixed with the raw material solution C introduced from the nozzle 15C. .

  In the nano-slurry manufacturing apparatus shown in FIG. 1 to FIG. 3, there is a member that inhibits the flow of liquid by forming a predetermined gap region between the rotor 11 and the inner periphery of the rotor 11. not exist. That is, when a member (for example, a stator) is present inside the rotor 11, the size of the gap between the member and the inner periphery of the rotor 11 is usually 2.5 mm, although it varies depending on the size of the device. If it is below, the flow of the liquid tends to be hindered. Accordingly, in the nano-slurry manufacturing apparatus shown in FIGS. 1 to 3, it is preferable that no member exists inside the rotor 11 (for example, the inside of the rotor 11 is a cavity). When a member is present, the flow of the liquid is less likely to be inhibited if the size of the gap between the member and the inner periphery of the rotor 11 exceeds 2.5 mm.

  In the nano slurry manufacturing apparatus shown in FIGS. 1 to 3 described above, a high shear rate region is formed between the rotor 11 and the outer stator 12 by rotating the rotor 11 at a high speed. The raw material solution A, the raw material solution B, and the raw material solution C are directly introduced into the speed region independently from the nozzle 15A, the nozzle 15B, and the nozzle 15C, respectively. Thereby, in the high shear rate region, the raw material solution A, the raw material solution B, and the raw material solution C are rapidly homogeneously mixed in a minute time and the reaction proceeds, and the colloidal particles or colloid derived from the raw material in the raw material solution It is possible to produce a solution (nano slurry) containing particle aggregates.

  As described above, the nano-slurry manufacturing apparatus used in the present invention has been described. However, in the method for manufacturing an exhaust gas purifying catalyst carrier of the present invention, the first raw material solution is used as the raw material solution A and the second raw material solution B is used as the second raw material solution B. A raw material solution may be used, a third raw material solution may be used as the raw material solution C, a second raw material solution may be used as the raw material solution A, a first raw material solution may be used as the raw material solution B, and a first raw material solution C may be used. Three raw material solutions may be used, or other combinations (correspondence between the raw material solutions A to C and the first to third raw material solutions) may be used.

Moreover, although there is no restriction | limiting in particular as each supply rate of a 1st raw material solution, a 2nd raw material solution, and a 3rd raw material solution, it changes also with the magnitude | size of an apparatus. For example, when the size of the gap between the rotor 11 and the outer stator 12 is 0.5 mm, 50 to 300 ml / min is preferable. When the supply rate of the raw material solution is less than the lower limit, the production efficiency of the metal compound colloidal particles tends to decrease, and when the upper limit is exceeded, the particle diameter of the metal compound colloidal particles tends to increase. When the size of the outer nozzle type homogenizer is changed to n times (for example, when the size of the gap is increased n times by scaling up a similar shape), the feed rate of the raw material solution is increased to n ³ times. It is preferable to set.

[Heat treatment process]
In the method for producing an exhaust gas purifying catalyst carrier of the present invention, in the nanoslurry preparation step, a first raw material solution containing aluminum ions, cerium ions and zirconium ions, and a second raw material solution containing hydrogen peroxide, Since the third raw material solution containing the neutralizing agent is mixed at once in the high shear rate region, the obtained metal compound nanoslurry is already neutralized (the pH of the metal compound nanoslurry is preferably Is 7.5-9, more preferably 8.5-9). For this reason, it is not necessary to adjust pH by adding a neutralizing agent to the obtained metal compound nanoslurry.

  That is, in the method for producing a catalyst carrier for exhaust gas purification of the present invention, the metal compound nanoslurry obtained in the nanoslurry preparation step is degreased without adjusting pH, and then subjected to heat treatment in an oxidizing atmosphere. By applying, the exhaust gas purifying catalyst carrier of the present invention can be obtained.

  Although it does not restrict | limit especially as said degreasing process, It dries on the conditions for 1 to 10 hours at 80-200 degreeC under oxidizing atmosphere (for example, air), and then degreases on the conditions for 1 to 5 hours at 200-400 degreeC. It is preferable to do.

  Moreover, as said heat processing, it is preferable to heat at the temperature of 700-1050 degreeC by oxidizing atmosphere (for example, air). When the heating temperature is less than the lower limit, sintering is not completed, so that the sintering proceeds during use of the catalyst and the oxygen storage capacity tends to be remarkably reduced. On the other hand, when the upper limit is exceeded, the composite metal oxide porous body There is a tendency that the specific surface area and the total pore volume of the material become smaller, and the oxygen storage capacity tends to decrease. Moreover, as a heating temperature, 800-1050 degreeC is especially preferable from a viewpoint that the outstanding oxygen storage ability is obtained. Further, the heating time is not particularly limited, but 1 to 10 hours is preferable. When the heating time is less than the lower limit, the metal compound after the degreasing treatment tends not to be sufficiently converted to a metal oxide. On the other hand, when the upper limit is exceeded, performance degradation such as sintering is likely to occur due to high temperature and oxidizing atmosphere. Tend to be.

  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
Cerium chloride heptahydrate (manufactured by Mitsuwa Chemicals Co., Ltd.) 111.8 g (0.30 mol), zirconium oxychloride octahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) 178.6 g (0.55) Mol), lanthanum chloride heptahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) 16.4 g (0.044 mol), yttrium chloride hexahydrate (manufactured by Mitsuwa Chemicals) 9.8 g (0 0.032 mol), aluminum chloride hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) 62.8 g (0.26 mol), and aluminum nitrate nonahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) 300 g ( 0.80 mol) was dissolved in ion exchange water to prepare 1100 ml of a first raw material solution. Further, 112 g of 30% hydrogen peroxide water (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in ion-exchanged water to prepare 1100 ml of a second raw material solution. Further, 42.23 g (0.43 mol) of maleic anhydride (manufactured by Wako Pure Chemical Industries, Ltd.) and 450 g of 28% ammonia water (manufactured by Wako Pure Chemical Industries, Ltd.) were dissolved in ion-exchanged water to obtain 1100 ml. A third raw material solution was prepared.

  A metal compound nano-slurry was produced using the production apparatus (outer nozzle type super agitation reactor) shown in FIGS. Note that a rotor 11 having an outer diameter of 42 mm was used, and a gap between the rotor 11 and the outer stator 12 was set to 0.5 mm. Further, as the outer stator 12, one having two nozzles 15A, two nozzles 15B, and two nozzles 15C was used.

  First, the first raw material solution is used as the raw material solution A, the second raw material solution is used as the raw material solution B, the third raw material solution is used as the raw material solution C, and the nozzle on the upstream side in the rotation direction of the rotor 11 is used. The raw material solution A, the raw material solution B, and the raw material solution C are discharged in order, and a raw material solution A feeding hose (not shown) is fed to the flow path 16A connected to the nozzle 15A. A liquid hose (not shown) was connected to the flow path 16B connected to the nozzle 15B, and a liquid supply hose (not shown) of the raw material solution C was connected to the flow path 16C connected to the nozzle 15C. In addition, an independent liquid feeding pump was connected to each liquid feeding hose.

Next, 700 ml of ion-exchanged water as a start-up liquid was placed in a 1 L beaker 20, and the tip of the outer nozzle type homogenizer 10 was set so as to be immersed in the start-up liquid. While rotating the rotor 11 in the outer nozzle type homogenizer 10 at 8000 rpm, the raw material solution A, the raw material solution B, and the raw material solution C are respectively supplied at a supply rate of 50 ml / min using a liquid feed pump, the nozzles 15A, 15B, and Liquid was fed from the nozzle 15 </ b> C to a region between the rotor 11 and the outer stator 12. The shear rate calculated on the assumption that the flow in the region between the rotor 11 and the outer stator 12 is a laminar flow was 35186 sec ⁻¹ .

  The metal compound nano-slurry overflowing from the beaker 20 was collected by a 5 L beaker (not shown) set under the beaker 20. 500 g of the obtained nanoslurry was put in a 1 L glass beaker, dried in a degreasing furnace at 150 ° C. for 10 hours, and then baked at 350 ° C. for 3 hours to perform a degreasing treatment. Further, the degreased composite metal oxide powder was put in an alumina crucible and calcined at 900 ° C. for 2 hours to obtain a catalyst carrier powder.

(Example 2)
In the same manner as in Example 1, 1100 ml of the first raw material solution was prepared. Further, 112 g of 30% hydrogen peroxide water (manufactured by Wako Pure Chemical Industries, Ltd.) and 80 g of glycerol (manufactured by Wako Pure Chemical Industries, Ltd.) are dissolved in ion-exchanged water to prepare 1100 ml of a second raw material solution. did. Furthermore, 200 g (1.90 mol) of diethanolamine (manufactured by Wako Pure Chemical Industries, Ltd.), 50 g (0.82 mol) of monoethanolamine (manufactured by Wako Pure Chemical Industries, Ltd.), and 28% ammonia water (Japanese 190 g (manufactured by Kojun Pharmaceutical Co., Ltd.) was dissolved in ion-exchanged water to prepare 1100 ml of a third raw material solution.

  The catalyst carrier was the same as in Example 1 except that the second raw material solution was used as the raw material solution A, the first raw material solution was used as the raw material solution B, and the third raw material solution was used as the raw material solution C. A powder was prepared.

(Comparative Example 1)
Cerium chloride heptahydrate (manufactured by Mitsuwa Chemicals Co., Ltd.) 111.8 g (0.30 mol), zirconium oxychloride octahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) 178.6 g (0.55) Mol), lanthanum chloride heptahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) 16.4 g (0.044 mol), yttrium chloride hexahydrate (manufactured by Mitsuwa Chemicals) 9.8 g (0 0.032 mol), aluminum chloride hexahydrate (Wako Pure Chemical Industries, Ltd.) 62.8 g (0.26 mol), aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd.) 300 g (0 .80 mol) and 112 g of 30% hydrogen peroxide water (manufactured by Wako Pure Chemical Industries, Ltd.) were dissolved in ion-exchanged water to prepare 1750 ml of raw material solution a. Further, 240 g (2.28 mol) of diethanolamine (manufactured by Wako Pure Chemical Industries, Ltd.) and 80 g (1.06 mol) of glycine (manufactured by Wako Pure Chemical Industries, Ltd.) were dissolved in ion-exchanged water to obtain 17500 ml of raw material. Solution b was prepared.

  A colloidal solution of a metal compound was prepared using the conventional manufacturing apparatus (inner nozzle type super agitation reactor) shown in FIGS. A rotor 41 having an outer diameter of 42 mm and an inner diameter of 37 mm was used, and the gap between the rotor 41 and the inner stator 43 was set to 0.5 mm. Further, as the inner stator 43, a 48-hole type in which 24 nozzles 45a and 24 nozzles 45b were provided, respectively, was used.

  First, the liquid supply hose (not shown) of the raw material solution a is connected to the flow path 46a connected to the nozzle 45a, and the liquid supply hose (not shown) of the raw material solution b is connected to the flow path 46b connected to the nozzle 45b. Each connected. In addition, an independent liquid feeding pump was connected to each liquid feeding hose.

Next, a 500 ml polypropylene beaker 20 was charged with start-up liquid adjusted to pH 4 by adding nitric acid to 300 ml ion-exchanged water, and the tip of the inner nozzle type homogenizer 40 was set so as to be immersed in the start-up liquid. While rotating the rotor 41 of the inner nozzle type homogenizer 40 at 8000 rpm, the raw material solution a and the raw material solution b are respectively fed from the nozzle 45a and the nozzle 45b to the rotor 41 and the inner stator at a supply rate of 50 ml / min. The solution was fed to the area between 43. The shear rate calculated on the assumption that the flow in the region between the rotor 41 and the inner stator 43 is a laminar flow was 30997 sec ⁻¹ .

  The reddish brown transparent colloidal solution overflowing from the beaker 20 was collected by a 5 L beaker (not shown) set under the beaker 20. To the obtained colloidal solution, 220 g (3.6 mol) of monoethanolamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added while stirring (3000 rpm) using a homomixer (manufactured by Primics Co., Ltd.). The pH was adjusted to 7 or more to obtain a nano slurry. 500 g of the obtained nanoslurry was put into a 1 L glass beaker, dried in a degreasing furnace at 150 ° C. for 10 hours, and then baked at 350 ° C. for 3 hours to perform a degreasing treatment. Further, the degreased composite metal oxide powder was put in an alumina crucible and calcined at 900 ° C. for 2 hours to obtain a catalyst carrier powder.

(Comparative Example 2)
In the same manner as in Example 1, a first raw material solution, a second raw material solution, and a third raw material solution were prepared. The first raw material solution is used as the raw material solution A, the second raw material solution is used as the raw material solution B, and the third raw material solution is used as the raw material solution C. The liquid hose, the liquid supply hose of the raw material solution B, and the liquid supply hose of the raw material solution C were fixed, respectively.

  Next, 700 ml of ion-exchanged water is added to the beaker as a start-up liquid, and the beaker is fed with the raw material solution A, the raw material solution B, and the raw material solution C at a supply rate of 50 ml / min with propeller stirring (300 rpm). And 4 L of slurry was obtained. 500 g of the obtained slurry was put into a 1 L glass beaker, dried in a degreasing furnace at 150 ° C. for 10 hours, and then baked at 350 ° C. for 3 hours to perform a degreasing treatment. Further, the degreased composite metal oxide powder was put in an alumina crucible and calcined at 900 ° C. for 2 hours to obtain a catalyst carrier powder.

<Standard deviation of metal element content>
The obtained catalyst carrier powder was pulverized in a mortar, and the obtained fine particles were placed on a Cu grid having a carbon film for a transmission electron microscope (TEM), and an energy dispersive X-ray analyzer (EDS) was mounted. STEM image observation and EDS mapping of the fine particles were performed using a scanning transmission electron microscope with a spherical aberration correction device (“JEM-2100F-Cs collector” manufactured by JOEL). In the obtained EDS mapping image, the content of Al, Zr, Ce, Y, and La within a 20 nm square microanalysis range was determined, and 100 measurement points (20 nm square microanalysis were randomly extracted). Range). The standard deviation of the content rate of each metal element was computed by making the content rate calculated | required from the preparation amount or the content rate calculated | required by ICP emission spectral analysis into an average content rate. The results are shown in Table 1.

<Preparation of catalyst carrier pellets>
70 g of 0.5 mm diameter alumina balls are put into a 250 ml polypropylene container, and further 10 g of the obtained catalyst carrier powder and 20 g of water are added, and 4 at 100 rpm so that the size of the catalyst carrier powder becomes 1 to 30 μm. Time grinding was applied. The obtained slurry was transferred to a 300 ml beaker, and water was added so that the volume of the slurry was 100 ml. Alumina sol (“A520” manufactured by Nissan Chemical Industries, Ltd.) is added to this slurry, and the mass ratio of the dry weight of the catalyst carrier powder to Al ₂ O ₃ in the alumina sol is catalyst carrier: Al ₂ O ₃ = 9: 1. After the addition, the mixture was stirred for 30 minutes at 300 rpm using a magnetic stirrer. The obtained slurry was evaporated to dryness at 150 ° C. for 3 hours, and then pulverized, and catalyst support pellets having a diameter of 0.5 to 1 mm were collected using a sieve having an opening of 1 mm and 0.5 mm.

<Specific surface area and differential pore volume distribution>
Using an automatic specific surface area / pore distribution measuring device (“Tristar II3020” manufactured by Micromeritics), the nitrogen adsorption isotherm of the obtained catalyst support pellet was determined. From this nitrogen adsorption isotherm, the multipoint specific surface area (BET specific surface area) is obtained by the BET method and the differential pore volume distribution is obtained by the BJH method. Further, the maximum frequency pore diameter and 0.001 are obtained from the obtained differential pore volume distribution. The total pore volume of pores having a pore diameter of ˜0.2 μm was determined. The results are shown in Table 1.

<Heat resistance test (1)>
The obtained catalyst carrier pellets were placed in an alumina crucible and subjected to a firing treatment at 1100 ° C. for 5 hours in the air in an electric furnace.

<Heat resistance test (2)>
1.5 g of the obtained catalyst carrier pellets were filled in a quartz tube having an inner diameter of 7 mm, and the filling part was sandwiched between quartz wool. In this quartz tube, reducing atmosphere gas (H ₂ (2% by volume) + CO ₂ (10% by volume) + H ₂ O (3% by volume) + N ₂ (remainder))) under the conditions of 1 atm and gas flow rate of 500 ml / min. Oxidizing atmosphere gas (O ₂ (1% by volume) + CO ₂ (10% by volume) + H ₂ O (3% by volume) + N ₂ (remainder)) is alternately switched every 5 minutes to flow into the catalyst carrier pellets. Heat treatment was performed at 1100 ° C. for 5 hours.

<Heat resistance test (3)>
Except for changing the heating time to 50 hours, the catalyst support pellets were heat-treated at 1100 ° C. in an R / L atmosphere in the same manner as in the heat resistance test (2).

<Decrease rate of specific surface area by heat test and increase rate of maximum frequency pore diameter>
The BET specific surface area and the maximum frequency pore diameter of each catalyst support pellet after the heat resistance tests (1) to (3) are obtained according to the above method, and the decrease rate of the specific surface area by the heat resistance test and the increase rate of the maximum frequency pore diameter by the heat resistance test are determined. It calculated | required according to the following formula. These results are shown in Table 1.
Reduction ratio of specific surface area (%) = (specific surface area before heat test−specific surface area after heat test) / specific surface area before heat test × 100.
Increase rate (%) of maximum frequency pore diameter = (maximum frequency pore diameter after heat test−maximum frequency pore diameter before heat test) / maximum frequency pore diameter before heat test × 100.

<Catalyst preparation>
70 g of 0.5 mm diameter alumina balls are put into a 250 ml polypropylene container, and further 10 g of the obtained catalyst carrier powder and 20 g of water are added, and 4 at 100 rpm so that the size of the catalyst carrier powder becomes 1 to 30 μm. Time grinding was applied. The obtained slurry was transferred to a 300 ml beaker, and water was added so that the volume of the slurry was 100 ml. Alumina sol (“A520” manufactured by Nissan Chemical Industries, Ltd.) is added to this slurry, and the mass ratio of the dry weight of the catalyst carrier powder to Al ₂ O ₃ in the alumina sol is catalyst carrier: Al ₂ O ₃ = 9: 1. At the same time, palladium nitrate was added so that the amount of Pd supported was 0.42 parts by mass with respect to 100 parts by mass of the catalyst carrier powder, and then stirred at 300 rpm for 30 minutes using a magnetic stirrer. The obtained slurry was evaporated to dryness at 150 ° C. for 3 hours, and then the solid content was transferred to a magnetic crucible and calcined at 500 ° C. for 2 hours to immobilize Pd on the catalyst carrier. Thereafter, a pulverization process was performed, and Pd-supported catalyst pellets having a diameter of 0.5 to 1 mm were collected using a sieve having an opening of 1 mm and 0.5 mm.

<Heat resistance test (4)>
The Pd-supported catalyst pellets were heat-treated at 1100 ° C. for 5 hours in an R / L atmosphere in the same manner as in the heat resistance test (2) except that the obtained Pd-supported catalyst pellets were used instead of the catalyst support pellets. gave.

<Heat resistance test (5)>
In the same manner as in the heat resistance test (3) except that the obtained Pd-supported catalyst pellet was used instead of the catalyst support pellet, the Pd-supported catalyst pellet was subjected to heat treatment at 1100 ° C. for 50 hours in an R / L atmosphere. gave.

<Oxygen release rate and saturated oxygen storage amount of Pd-supported catalyst after heat test>
After the heat resistance test (4) to (5), 0.5 g of each Pd-supported catalyst pellet was filled in a quartz tube having an inner diameter of 10 mm to prepare a catalyst bed. As a pretreatment, a reducing atmosphere gas (CO (2% by volume) + CO ₂ (10% by volume) + H ₂ O (3% by volume) + N is applied to the catalyst bed as a pretreatment under the conditions of a catalyst bed temperature of 600 ° C. and a gas flow rate of 10 L / min. ₂ (remainder)) and oxidizing atmosphere gas (O ₂ (1 vol%) + CO ₂ (10 vol%) + H ₂ O (3 vol%) + N ₂ (remainder))) are alternately switched every minute for 10 Circulated for 5 minutes (5 cycles). Next, after changing the temperature of the catalyst bed to 500 ° C. in a nitrogen gas atmosphere, the oxidizing atmosphere gas is applied to the catalyst bed for 3 minutes, the nitrogen gas is applied for 1 minute, and the reducing atmosphere at a gas flow rate of 10 L / min. Gas was continuously passed for 3 minutes and nitrogen gas for 1 minute, and this was repeated 3 times (3 cycles). During the second (second cycle) reducing atmosphere gas flow, the initial CO ₂ generation rate for 5 seconds (CO ₂ generation amount for 5 seconds / 5 seconds) and the CO ₂ generation amount for 3 minutes were measured. The oxygen release rate (OSC-r) and the saturated oxygen storage amount (OSC-c) were used, respectively. The results are shown in Table 1.

  As is apparent from the results shown in Table 1, a first raw material solution containing Al ions, Ce ions and Zr ions, a second raw material solution containing hydrogen peroxide, and a raw material solution containing a neutralizing agent, In the catalyst support (Examples 1 and 2) prepared by supplying each independently to a high shear rate region, each metal element is finely and uniformly dispersed in each other, and a heat resistance test (in air or R / L atmosphere) Even when the heat treatment at 1100 ° C. was performed for a long time, it was confirmed that the decrease rate of the specific surface area and the increase rate of the maximum frequency pore diameter were small and excellent in heat resistance. In addition, by supporting a noble metal on such a catalyst carrier, a high oxygen release rate (OSC-r) can be obtained even when a heat resistance test (in the air or in an R / L atmosphere, heat treatment at 1100 ° C.) is performed for a long time. It was also confirmed that an exhaust gas purifying catalyst having the following can be obtained.

  On the other hand, a catalyst carrier prepared by independently supplying a raw material solution containing Al ions, Ce ions, Zr ions and hydrogen peroxide and a raw material solution containing a neutralizing agent to the high shear rate region (Comparative Example 1) Although each metal element is finely and uniformly dispersed in each other, the specific surface area is remarkably reduced by the heat resistance test (in the air or in an R / L atmosphere at 1100 ° C.), and the maximum frequency pore diameter Significantly increased and the heat resistance was poor. In addition, the catalyst in which a noble metal is supported on such a catalyst carrier is compared with the exhaust gas purifying catalyst (Examples 1 and 2) of the present invention after a heat resistance test (heat treatment at 1100 ° C. in an R / L atmosphere). Was found to have a slow oxygen release rate (OSC-r).

  A catalyst prepared by mixing a first raw material solution containing Al ions, Ce ions, and Zr ions, a second raw material solution containing hydrogen peroxide, and a raw material solution containing a neutralizing agent by propeller stirring. The carrier (Comparative Example 2) had low dispersibility of Al and Zr. Compared with the exhaust gas purifying catalyst of the present invention (Examples 1 and 2), the catalyst in which the noble metal is supported on such a catalyst carrier is subjected to a heat treatment (in particular, heat treatment at 1100 ° C. in an R / L atmosphere (in particular 50 It was found that the oxygen release rate (OSC-r) after the heat treatment for a time)) was slow, and the saturated oxygen storage amount (OSC-c) was small.

  As described above, according to the present invention, the metal elements are finely and uniformly dispersed with each other, and even when exposed to high temperatures, the decrease in specific surface area and the increase in pore diameter are small. It becomes possible to obtain a catalyst carrier for exhaust gas purification comprising a composite metal oxide porous body.

  Therefore, the exhaust gas purifying catalyst of the present invention is such that a noble metal is supported on such an exhaust gas purifying catalyst carrier, and exhibits a high oxygen release rate even when exposed to a high temperature for a long time. The present invention is useful as an exhaust gas purifying catalyst for purifying gas containing harmful substances discharged from an internal combustion engine, particularly as an exhaust gas purifying catalyst used for a long time in a high temperature environment.

  10: outer nozzle type homogenizer, 11: rotor, 11a: slit, 12: outer stator with nozzle, 12a: slit, 13: rotating shaft, 14: motor, 15A, 15B, 15C: nozzle without branching, 16A, 16B, 16C: Unbranched flow path, 20: Reaction vessel, 40: Inner nozzle type homogenizer, 41: Rotor, 42: Outer stator, 43: Inner stator, 45a, 45b: Nozzle, 46a, 46b: Flow path

Claims (5)

Preparing a first raw material solution containing aluminum ions, cerium ions and zirconium ions;
Preparing a second raw material solution containing hydrogen peroxide;
Preparing a third raw material solution containing a neutralizing agent;
A step of obtaining a metal compound nano-slurry by directly and independently introducing the first raw material solution, the second raw material solution, and the third raw material solution independently into a region having a shear rate of 5000 to 40000 sec ^−1. When,
Degreasing the nanoslurry and heating in an oxidizing atmosphere to obtain a composite metal oxide porous body containing alumina, ceria and zirconia;
A method for producing an exhaust gas purifying catalyst carrier, comprising: The method for producing an exhaust gas purifying catalyst carrier according to claim 1 , wherein the third raw material solution further contains a dispersant. The method for producing an exhaust gas purifying catalyst carrier according to claim 1 or 2 , wherein the second raw material solution further contains glycerol. Of all the counter anion of the first raw material solution, a 47 to 65 mole percent chloride ions, any of the preceding claims, characterized in that 35 to 53 mol% are nitrate ions A method for producing an exhaust gas purifying catalyst carrier according to claim 1. To any one of claims 1 to 4, characterized in that said first raw material solution is one which further contains at least one metal ion selected from the group consisting of lanthanum ions and yttrium ions The manufacturing method of the catalyst carrier for purification | cleaning of exhaust gas as described.