JP5652271B2 - Exhaust gas purification catalyst carrier, exhaust gas purification catalyst using the same, and method for producing exhaust gas purification catalyst carrier - Google Patents

Description

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

  Conventionally, 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 capacity (OSC capacity) 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 a relatively low heat resistance. Therefore, the heat resistance of a catalyst is improved by using ceria and zirconia or alumina as a solid solution or mixed.

  JP-A-2006-43654 (Patent Document 1) includes a first metal oxide support made of ceria or zirconia and a second metal oxide support made of alumina, ceria or zirconia, An exhaust gas purifying catalyst carrier is disclosed in which both the first and second metal oxide carriers have a primary particle size of less than 100 nm and the primary particles are mixed with each other. Furthermore, Japanese Patent Application Laid-Open No. 2006-298759 (Patent Document 2) discloses a composite oxide obtained by a coprecipitation method, which is made of alumina, ceria and zirconia as an exhaust gas purification catalyst carrier.

  JP 2009-242226 A (Patent Document 3) discloses a method for producing alumina particles used as a catalyst carrier in a state where the particles are dispersed in a liquid containing alumina particles and a metal component such as cerium. A method for obtaining alumina particles having a particle size of 10 to 100 nm by heating while applying pressure in the presence of a liquid is disclosed. Furthermore, in JP 2008-12527 A (Patent Document 4), a liquid containing metal compound particles such as alumina and a dispersant is adjusted to a pH at which the particles are dispersed, and in the presence of the liquid. A method for obtaining metal oxide particles having a particle size of about 20 nm by heating while applying pressure is disclosed.

On the other hand, as the metal supported on the catalyst carrier, the above-mentioned noble metals are widely known. However, in recent years, copper-based catalysts made of copper, which are cheaper than noble metals, are also effective as exhaust gas purification catalysts. It is disclosed that there is. For example, Japanese Patent Laid-Open No. 10-28842 (Patent Document 5) discloses a spinel made of a transition metal such as copper and aluminum and having a catalytic activity, and a support material in which a noble metal such as ceria is additionally added to spinel. Yes. Japanese Patent Application Laid-Open No. 2010-51864 (Patent Document 6) discloses an alumina as a base material, a copper layer, and zinc oxide, CuAl ₂ O ₄ , CuAlO _2, and Al ₂ O ₃ below the copper layer. A layer composed in a form having at least a composite layer containing at least one selected from the group consisting of: a mixed layer having zinc and Al ₂ O ₃ on the surface of the lower substrate of the composite layer A reduction precipitation type copper catalyst is disclosed. However, such a copper-based catalyst has a problem that the catalytic activity, particularly the NOx reduction activity, is not sufficient as compared with the catalyst using the noble metal.

JP 2006-43654 A JP 2006-298759 A JP 2009-242226 A JP 2008-12527 A JP-A-10-28842 JP 2010-51864 A

  In the conventional catalyst carrier as described above, for example, when ceria and zirconia are used as a solid solution or mixed, the size (crystallite diameter) of primary particles obtained by solidifying ceria and zirconia is small. It is known that the catalytic activity becomes higher. However, in the conventional composite metal oxide supports as described in Patent Documents 1 to 4 above, the crystallite size of the primary particles and the dispersion of the particles are not controlled at the nanosize level. The present inventors have found that the catalyst activity of a catalyst obtained using such a complex metal oxide as a support is not always sufficient, and there is a limit to improvement in heat resistance. Further, in such a conventional catalyst carrier, it is difficult to obtain sufficient catalytic activity particularly when a transition metal compound such as copper is used as a catalyst component.

  The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to obtain a catalyst having a high level of catalytic activity even when a transition metal compound is used as a supported catalyst component. It is an object of the present invention to provide an exhaust gas purifying catalyst carrier and a method for producing the same.

  As a result of intensive studies to achieve the above object, the present inventors have obtained a first raw material solution containing aluminum ions and cerium ions, and a second raw material solution containing a polymer dispersant, The colloidal solution, which is directly and independently introduced into the region where the specific shear rate is obtained, is adjusted to a predetermined pH condition, and then the resulting colloidal solution is hydrothermally treated. By degreasing the solution and heat-treating, the ultrafine particles containing alumina and the ultrafine particles containing ceria are uniformly mixed with extremely high dispersibility, and the crystallite diameter and specific surface area are controlled at the nanosize level. It has been found that an exhaust gas purifying catalyst carrier can be obtained. And when the catalyst carrier for exhaust gas purification is used, it has been found that a catalyst having a high level of catalytic activity can be obtained even when a transition metal compound such as copper is used as a catalyst component. It came to be completed.

That is, the catalyst carrier for exhaust gas purification of the present invention is
A catalyst carrier for exhaust gas purification comprising a mixture of first ultrafine particles containing alumina and second ultrafine particles containing ceria,
All metal elements contained in the carrier in an amount of 0.1% by mass or more are analyzed by energy dispersive X-ray spectroscopy using a scanning transmission electron microscope with a spherical aberration correction function. The first ultrafine particles and the second fine particles are so satisfied that the standard deviation of the content of each metal element obtained by measuring the content (mass%) at 300 measurement points is 10 or less. Ultra fine particles are uniformly dispersed,
The specific surface area determined by the BET method is 110 m ² / g or more,
The second ultrafine particles have an average crystallite diameter of 5 to 11 nm determined by an X-ray diffraction method.

In the exhaust gas purifying catalyst carrier of the present invention, the center pore diameter determined by the nitrogen adsorption method is preferably 8 to 20 nm, and the pore volume is preferably 0.2 to 0.6 cm ³ / g. Furthermore, it is more preferable that the second ultrafine particles further contain zirconia and / or yttria, and it is particularly preferable that the content of alumina is 30 to 80% by mass.

  The exhaust gas purifying catalyst of the present invention comprises the exhaust gas purifying catalyst carrier of the present invention and any one selected from the group consisting of metals and transition metal compounds supported on the surface of the carrier. It is a feature.

Furthermore, the method for producing the exhaust gas purifying catalyst carrier of the present invention comprises:
A first raw material solution containing aluminum ions and cerium ions and a second raw material solution containing a polymer dispersant are directly and independently introduced into a region having a shear rate of 1000 to 200000 sec ^−1. Mixing the mixture homogeneously to obtain a colloidal solution;
Adjusting the pH of the colloidal solution to a pH condition capable of maintaining the state in which the colloidal solution is dispersed in the liquid;
Hydrothermally treating the colloidal solution at a temperature of 70 to 90 ° C .;
And degreasing the colloidal solution after the hydrothermal treatment and heat-treating it in an oxidizing atmosphere at a temperature of 700 to 1050 ° C. to obtain an exhaust gas-purifying catalyst carrier.

  In the method for producing the exhaust gas purifying catalyst carrier of the present invention, it is preferable that the first raw material solution further contains zirconium ions and / or yttrium ions.

  Further, in the method for producing an exhaust gas purifying catalyst carrier of the present invention, the step of adjusting the pH of the colloidal solution after the hydrothermal treatment to a pH condition in which the colloidal solution cannot maintain a dispersed state in the liquid, It is preferable to further provide after the hydrothermal treatment step.

  Further, in the method for producing an exhaust gas purifying catalyst carrier of the present invention, the polymer dispersant is at least one polyalkyleneimine having a weight average molecular weight of 3000 to 15000, and the colloidal solution is dispersed in the liquid. It is preferable that the pH condition capable of maintaining the pH is 1.0 to 6.0, and the pH condition where the colloidal solution cannot be dispersed in the liquid is 9.0 to 11.0.

  Furthermore, in the method for producing an exhaust gas purifying catalyst carrier of the present invention, the polymer dispersant is at least one polyacrylic acid having a weight average molecular weight of 1000 to 5000, and the colloidal solution is dispersed in the liquid. It is preferable that the pH condition that can maintain the temperature is 5.0 to 10.0.

  The reason why the production method of the present invention can provide the exhaust gas-purifying catalyst carrier of the present invention in which ultrafine particles containing alumina and ultrafine particles containing ceria are uniformly mixed with extremely high dispersibility is obtained. Although not necessarily certain, 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. It is inferred that the dispersant is adsorbed on the nanoparticles, and the nanoparticles are present in the colloidal solution as it is or in the form of an aggregate having a relatively small particle diameter. 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 as it is or in the form of aggregates having a relatively small particle size because of the pH conditions that can be maintained.

  Further, usually, the specific surface area of the support tends to increase due to hydrothermal treatment, but the regularity of the porous body tends to decrease. However, in the production method of the present invention, the above-mentioned colloidal solution in which the nanoparticles are uniformly dispersed is hydrothermally treated under a specific low temperature condition, so that crystallization of each particle is promoted and more uniform without voids. The present inventors speculate that since a complete crystal is formed, a porous body having a large specific surface area and heat resistance and a uniform pore diameter can be obtained. Then, the colloidal solution after such hydrothermal treatment is degreased and heat-treated at a specific temperature condition, whereby the ultrafine particles containing alumina and the ultrafine particles containing ceria are uniformly mixed with extremely high dispersibility. The present inventors infer that the exhaust gas-purifying catalyst carrier of the present invention can be obtained.

  Further, it is not always clear why an ideal catalyst that achieves high catalytic activity and durability at high temperatures can be obtained by using the exhaust gas purifying catalyst carrier of the present invention as a catalyst carrier. However, the present inventors infer as follows. That is, in the exhaust gas purifying catalyst carrier of the present invention, the ultrafine particles containing alumina and the ultrafine particles containing ceria are uniformly mixed at a nano level with extremely high dispersibility. Functions as a diffusion barrier, and particle growth is suppressed even in a high temperature atmosphere, so that a high specific surface area is maintained up to a high temperature. Also, when the primary particle has a small crystallite size, when the copper compound is used as a catalyst, the affinity between the copper compound and the primary particle becomes strong and the reducibility of the copper oxide deteriorates. Although the reduction performance of the copper oxide particles in the particles (ceria-containing particles) is deteriorated, the present invention can suppress such a decrease in catalytic activity because the crystallite size of the primary particles is in a specific range. Furthermore, by arranging the ultrafine particles with small agglomeration and a small gap between the particles, a large pore volume can be achieved, and at the same time, the pore diameter is maintained even at high temperatures, so that gas diffusibility is achieved. Is suppressed. For this reason, the present inventors presume that by using such an exhaust gas purifying catalyst carrier of the present invention as a catalyst carrier, ideal catalyst activity is realized in the diffusion-controlled region and its high-temperature durability becomes high. To do.

  According to the present invention, an exhaust gas purifying catalyst carrier capable of obtaining a catalyst having a high level of catalytic activity even when a transition metal compound is used as a supported catalyst component, and a method for producing the same Can be provided.

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. In the catalysts obtained using the exhaust gas purifying catalyst carriers obtained in Examples 1 to 5 and Comparative Examples 1 to 6, the relationship between the average crystallite diameter of the second ultrafine particles in the carrier and the NO50% purification temperature is shown. It is a graph to show.

  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 support for exhaust gas purification of the present invention is a composite metal oxide porous body comprising a mixture of first ultrafine particles containing alumina and second ultrafine particles containing ceria. The “ultrafine particles” referred to here are primary particles of metal oxide or composite metal oxide crystallites or independent secondary particles without being bonded to each other.

The first ultrafine particles only need to contain alumina (Al ₂ O ₃ ), but rare earth elements other than cerium (La, Pr, Y, Sc, etc.) from the viewpoint of obtaining a heat-resistant catalyst carrier. And at least one metal oxide selected from the group consisting of oxides of alkaline earth metals (Sr, Ca, Ba, etc.). When the first ultrafine particles are a composite metal oxide or a metal oxide mixture containing alumina and another metal oxide, the alumina content in the first ultrafine particles is preferably 95 mol% or more.

The second ultrafine particles only need to contain ceria (CeO ₂ ), but zirconia (ZrO ₂ ), oxides of rare earth elements other than cerium (La, Pr, Y, Sc, etc.) and alkaline earth metals ( Sr, Ca, Ba, etc.) may further contain at least one metal oxide selected from the group consisting of oxides. Among these, from the viewpoint of having oxygen storage ability and heat resistance, it may further contain at least one selected from the group consisting of zirconia (ZrO ₂ ), yttria (Y ₂ O ₃ ), and lantana (La ₂ O ₃ ). Preferably, zirconia (ZrO ₂ ) and / or yttria (Y ₂ O ₃ ) is further contained. Such second ultrafine _{particles, CeO 2 -ZrO 2 -Y 2 O} 3 -La 2 O 3 4 -component composite metal _{oxide; CeO 2 -ZrO 2 -Y 2 O} 3 3 -component complex metal oxide It is particularly preferable that it is made of a binary complex metal oxide such as CeO ₂ —ZrO ₂ , CeO ₂ —Y ₂ O ₃ and CeO ₂ —La ₂ O ₃ . When the second ultrafine particles are a composite metal oxide or metal oxide mixture containing ceria and another metal oxide, the ceria content in the second ultrafine particles is preferably 10 mol% or more.

  The content of the first ultrafine particles in the exhaust gas purification catalyst carrier of the present invention is not particularly limited, but the content of alumina in the obtained exhaust gas purification catalyst carrier is 30 to 80% by mass. It is more preferable that the content is 37 to 71% by mass. If 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, if the content of alumina exceeds the upper limit, ceria and / or ceria and other metal oxides are added. Since the amount of the composite metal oxide or metal oxide mixture contained decreases, the OSC ability of ceria tends not to be sufficiently exhibited, and further, the reduction performance of the noble metal or transition metal compound serving as the catalyst component tends to decrease. It is in.

  The content of the second ultrafine particles in the exhaust gas purification catalyst carrier of the present invention is not particularly limited, but the content of ceria in the obtained exhaust gas purification catalyst carrier is 20 to 70% by mass. It is more preferable that the content is 20 to 60% by mass. If the content of ceria is less than the lower limit, the OSC ability of ceria tends to be insufficiently exhibited, and the reduction performance tends to decrease when copper oxide is used as a catalyst component. When the value exceeds the upper limit, the heat resistance of the catalyst carrier decreases, and the OSC ability of ceria tends to decrease.

When the second ultrafine particles are made of CeO ₂ —ZrO ₂ —Y ₂ O ₃ , the content of ceria in the obtained exhaust gas purification catalyst carrier is 20 to 70% by mass, and the content of zirconia The amount is 6 to 40% by mass, and the yttria content is preferably 1 to 5% by mass. Further, when the second ultrafine particles are made of CeO ₂ —ZrO ₂ , the content of ceria in the obtained exhaust gas purification catalyst carrier is 20 to 75% by mass, and the content of zirconia is 6 to 40%. It is preferable that it is mass%. In the exhaust gas purification catalyst carrier of the present invention, when the second ultrafine particles are made of CeO ₂ —Y ₂ O ₃ , the content of ceria in the obtained exhaust gas purification catalyst carrier is 20 to 75% by mass. The yttria content is preferably 1 to 5% by mass.

  In the exhaust gas purifying catalyst carrier of the present invention, the first ultrafine particles and the second ultrafine particles are uniformly dispersed, and for all the metal elements contained in the porous body in an amount of 0.1% by mass or more, Measurement points of the content (mass%) of the metal element in a 20 nm square microanalysis range by energy dispersive X-ray spectroscopy (EDS) using a scanning transmission electron microscope (STEM) with a spherical aberration correction function The standard deviation of the content rate of each metal element obtained by measuring in the above condition is 10 or less. Thus, since the first ultrafine particles and the second ultrafine particles are uniformly mixed with extremely high dispersibility, the exhaust gas purifying catalyst carrier of the present invention is excellent in heat resistance, and the carrier is used as the catalyst carrier. As a result, it is possible to obtain a catalyst that achieves a high level of catalytic activity and durability at high temperatures.

  In addition, such a standard deviation can be obtained by using an EDS apparatus (200 KV TEM, ADF-STEM image) attached to STEM (manufactured by JEOL, JEM-2100F Cs collector) of Al, Ce, Zr, and Y in a 20 nm square area. Each content rate (content rate in terms of metal (% by mass)) is measured at 300 measurement points, and the standard deviation of the measurement values at all measurement points calculated on the basis of the content rate of each metal in the entire carrier is there. The content of each metal in the entire support is the content (% by mass) of Al, Ce, Zr, and Y with respect to the total mass of the metal in the support, using an ICP emission analyzer (CIROS 120EOP, manufactured by Rigaku Corporation). The total mass of the metal in the support and the respective masses of Al, Ce, Zr, and Y are determined.

In the exhaust gas purifying catalyst carrier of the present invention, the specific surface area determined by the BET method is 110 m ² / g or more. When the specific surface area is less than the lower limit, it becomes difficult to support the catalyst without agglomerating, so that the catalyst performance decreases. Such a specific surface area is preferably large, but when the content of alumina in the catalyst support is 30 to 80%, the specific surface area is particularly preferably 110 to 200 m ² / g. More preferably, it is 160 m ² / g.

  In the exhaust gas purifying catalyst carrier of the present invention, the central pore diameter determined by the nitrogen adsorption method is preferably 8 to 30 nm, and more preferably 8 to 20 nm. When the center pore diameter is less than the lower limit, the gas diffusion performance when used as an exhaust gas purifying catalyst tends to be lowered. On the other hand, when the upper limit is exceeded, the exhaust gas adsorption performance tends to be lowered.

Furthermore, in the exhaust gas purifying catalyst carrier of the present invention, it is preferable that the pore volume determined by nitrogen adsorption method is 0.2~0.6cm ³ / g, in 0.3~0.55cm ³ / g More preferably. When the pore volume is less than the lower limit, the gas diffusion performance when used as an exhaust gas purification catalyst tends to be lowered, and when the upper limit is exceeded, the exhaust gas adsorption performance tends to be lowered.

In the present invention, the specific surface area, central pore diameter and pore volume are determined by the following nitrogen adsorption method. That is, first, the exhaust gas purification catalyst carrier is cooled to 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. 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. The specific surface area of the exhaust gas purification catalyst carrier can then be determined from the obtained nitrogen adsorption isotherm by the BET isotherm adsorption formula. For example, a fully automatic specific surface area measurement device (manufactured by Cantachrome, "Autosorb-1") Can be calculated by the BET one-point method using N ₂ adsorption at a liquid nitrogen temperature (−196 ° C.).

  Similarly, the pore volume of the exhaust gas-purifying catalyst carrier can be obtained by obtaining the nitrogen adsorption amount when the relative pressure reaches the maximum value from the nitrogen adsorption isotherm. Furthermore, a pore size distribution curve is obtained from the obtained nitrogen adsorption isotherm by a calculation method such as Cranston-Inklay method, Polimore-Heal method or BJH method, and the pore diameter at the maximum peak of this pore size distribution curve is used for exhaust gas purification. The center pore diameter of the catalyst support.

In the exhaust gas purifying catalyst carrier of the present invention, the average crystallite diameter of the second ultrafine particles determined by the X-ray diffraction method is 5 to 11 nm. When the average crystallite diameter is less than the lower limit, sufficient catalytic activity cannot be obtained, and when the upper limit is exceeded, sufficient catalytic activity cannot be obtained. The average crystallite size of the second ultrafine particles is based on the half width of the peak derived from the (111) plane of the second ultrafine particles obtained by measurement by X-ray diffraction (XRD). 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)
Can be obtained by calculating. As a method of X-ray diffraction measurement in confirming such a crystallite diameter, as a measuring device, using “RINT-2200” manufactured by Rigaku Corporation, a scan step of 0.01 °, a divergence and scattering slit 1 deg, A method of measuring under the conditions of a light receiving slit of 0.15 mm, CuKα ray, 40 kV, 20 mA, and a scanning speed of 1 ° / min is adopted.

As the catalyst support for exhaust gas purification of the present invention, in addition to the first ultrafine particles containing alumina and the second ultrafine particles containing ceria, CuAl ₂ O ₄ and CuO exhibiting excellent catalytic activity as additive components Etc. may be contained. The amount of such an additive component is not particularly limited and is appropriately adjusted depending on the intended use of the catalyst, etc., but is 0.1 to 100 parts by mass of the exhaust gas purification catalyst carrier (excluding the additive component). The amount is preferably about 10 parts by mass.

  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 any one selected from the group consisting of metals and transition metal compounds supported on the surface of the carrier. . In the exhaust gas purifying catalyst of the present invention, the ultrafine particles of the exhaust gas purifying catalyst carrier of the present invention as the carrier are uniformly mixed with extremely high dispersibility, and the crystallite diameter of the primary particles is controlled to a nanometer size. Therefore, even if the supported metal is a transition metal or transition metal compound other than a noble metal, excellent catalytic activity can be realized.

  Examples of such metals include noble metals, transition metals, and alloys thereof. Examples of the noble metal include platinum, rhodium, palladium, osmium, iridium, and gold. Platinum, rhodium, and palladium are preferable from the viewpoint that the obtained catalyst is useful as an exhaust gas purifying catalyst. Examples of the transition metal include Cu, Fe, Ni, Co, Mn, Zn, W, Mo, Nb, Sn, Ta, and Ag. These metals may be used individually by 1 type, or may use 2 or more types together. Among these, Cu is preferable from the viewpoint of exhibiting high NOx reduction performance, and Cu, Fe, Mn, and Ag are preferable from the viewpoint of having high oxidation performance of CO and CH compounds. Examples of the alloy include Cu / Mn, Cu / Fe, Fe / Mn, Ag / Cu, Ag / Ni, Cu / Ni, and Fe / Ni.

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. .

  Further, the amount of such a metal and metal compound supported is not particularly limited and is appropriately adjusted according to the use of the obtained catalyst, etc., but is 0.1 to 10 mass with respect to 100 mass parts of the exhaust gas purification catalyst carrier. It is preferable that it is about a part.

  In the catalyst of the present invention, the form is not particularly limited. For example, the catalyst may be used in the form of particles, or a honeycomb-shaped monolith catalyst having the catalyst supported on a base material or the catalyst may be used. You may use as a form etc. of the pellet catalyst shape | molded to 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 catalyst of this invention, the other component (for example, NOx storage material etc.) which can be used for various catalysts in the range which does not impair the effect may be carry | supported suitably.

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:
A first raw material solution containing aluminum ions and cerium ions and a second raw material solution containing a polymer dispersant are directly and independently introduced into a region having a shear rate of 1000 to 200000 sec ^−1. Mixing the mixture homogeneously to obtain a colloidal solution;
Adjusting the pH of the colloidal solution to a pH condition capable of maintaining the state in which the colloidal solution is dispersed in the liquid;
Hydrothermally treating the colloidal solution at a temperature of 70 to 90 ° C .;
The method comprising the steps of: degreasing the colloidal solution after the hydrothermal treatment and obtaining a catalyst support for exhaust gas purification by heat treatment in an oxidizing atmosphere at a temperature of 700 to 1050 ° C. Thus, the exhaust gas purifying catalyst carrier of the present invention can be obtained.

(Colloid solution preparation process)
The first raw material solution containing the aluminum ion and the cerium ion includes an aluminum compound, a cerium compound, and another metal compound depending on the composition of the target first and second ultrafine particles. It is obtained by dissolving in

  As such aluminum compounds, cerium compounds, and other metal compounds, salts of those 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 product, and not containing sulfur as a performance deterioration component when used as a catalyst carrier for exhaust gas purification, acetate or nitrate is particularly preferable.

  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 polyalkyleneimine and polyacrylic acid are particularly preferable from the viewpoint that high dispersion performance can be exhibited in the liquid.

  Examples of the solvent used in the present invention include water, water-soluble organic solvents (methanol, ethanol, propanol, isopropanol, butanol, acetone, acetonitrile, etc.), a mixed solvent of water and the water-soluble organic solvent, and the like.

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. By homogeneous mixing in this way, even in a solvent in which metal compound crystallites such as water easily aggregate, the metal compound crystallites are dispersed in the liquid in the same state or in a uniform aggregate state with a smaller diameter. It becomes possible.

  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 a stable colloidal solution cannot be obtained.

  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. When these gaps are less than the lower limit, clogging of the gaps tends to occur, and when the upper limit is exceeded, effective shearing force cannot 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. When the feed rate of the raw material solution is less than the lower limit, the production efficiency of the metal compound crystallites and aggregates thereof tends to decrease. On the other hand, when the upper limit is exceeded, the particle diameter of the metal compound crystallite aggregates is large. Tend to be.

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

  In the first raw material solution containing the metal ions, the ratio of aluminum ions to cerium ions is preferably 92: 8 to 58:42 as a molar ratio per liter of the solution. In the catalyst support powder obtained when the content of aluminum ions is less than the lower limit, the function as a diffusion barrier of alumina tends not to be sufficiently exhibited, and on the other hand, the amount of ceria is reduced when the upper limit is exceeded, There is a tendency that the OSC performance is not exhibited.

  Further, the content of other metal ions in the case of containing other metal ions other than aluminum ions and cerium ions is not particularly limited, and is adjusted according to the intended composition of the first and second ultrafine particles. However, it is preferably 35 mol% or less based on the total amount of cations in the first raw material solution. When zirconium ions are contained as the other metal ions, the content of zirconium ions with respect to the total amount of the cations is preferably 2 to 35 mol%. Moreover, when it contains an yttrium ion as said other metal ion, it is preferable that content of the yttrium ion with respect to the whole quantity of the said cation is 0.05-4 mol%. Further, when zirconium ions and yttrium ions are contained, the content of zirconium ions is preferably 2 to 35 mol% and the content of yttrium ions is 0.05 to 4 mol% with respect to the total amount of the cation. .

  Furthermore, in the step of obtaining the colloidal solution according to the present invention, it is preferable to use polyalkyleneimine or polyacrylic acid as the polymer dispersant, but it is more preferable to satisfy the following conditions depending on the polymer dispersant used. preferable.

<When polyalkyleneimine is used as the polymer dispersant>
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 in the above range, the metal compound crystallites are dispersed as they are or 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 content of the polyalkylene imine in the resultant colloidal solution is preferably 5-35 mg / ^{m 2} relative to unit surface area of the crystallites of the metal compound, and more preferably 5 to 15 mg / ^{m 2.} When the content of the polyalkyleneimine is in the above range, the metal compound crystallites are dispersed as they are or 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, if the content of the polyalkyleneimine 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 tend to aggregate to form larger aggregates. On the other hand, if the upper limit is exceeded, a large amount of free polyalkyleneimine is present in the colloidal solution, so that the crosslinking reaction of polyalkyleneimine proceeds remarkably and aggregates having a large particle size tend to be formed.

Moreover, it is preferable to adjust pH of the obtained colloid solution to 1.0-6.0. When the pH of the colloidal solution is within the above range, the polyalkyleneimine dissociates to form NH ₃ ⁺ groups, which are adsorbed on the negatively charged sites or neutral sites of the metal compound crystallites to impart a dispersion effect. As a result, the metal compound crystallites are dispersed as they are or 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 pH is less than the lower limit, the surface of the metal compound crystallite is large and positively charged. Therefore, the polyalkyleneimine formed by dissociation and forming NH ₃ ⁺ groups is difficult to be adsorbed on the metal compound crystallite, and between the metal compound fine particles. However, when the above upper limit is exceeded, the degree of dissociation of the polyalkyleneimine is small, and the amount of polyalkyleneimine adsorbed on the metal compound fine particles decreases. In addition, sufficient repulsive force is not expressed between the metal compound fine particles, and the metal compound fine particles tend to aggregate.

Furthermore, it is preferable that the shear rate is set to 7500 sec ⁻¹ or less (more preferably 6500 sec ⁻¹ or less) in the regions where the first raw material solution and the second raw material solution are respectively introduced. When the shear rate in this region exceeds the upper limit, the polyalkyleneimine is destroyed, and sufficient repulsive force cannot be applied to the metal compound fine particles, and a larger aggregate tends to be formed.

<When using polyacrylic acid as a polymer dispersant>
As a weight average molecular weight of polyacrylic acid, 1000-5000 are preferable and 1000-3000 are more preferable. When the weight average molecular weight of the polyacrylic acid is within the above range, the metal compound crystallites are in the same state or a uniform aggregate with a small particle diameter, and a colloidal solution having excellent storage stability can be obtained. On the other hand, when the weight average molecular weight of the polyacrylic acid is less than the lower limit, even if the polymer dispersant is adsorbed to the crystallite, repulsive force due to steric hindrance or electrostatic repulsion is not sufficiently exhibited, and the crystallites tend to aggregate. On the other hand, when the above upper limit is exceeded, the polymer dispersant becomes extremely large compared to the crystallite, and a large number of adsorption sites exist in the molecule, so that the polymer dispersant is easily adsorbed on a large number of crystallites, resulting in a larger coagulation. Aggregation tends to remain. 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 content of polyacrylic acid in the resultant colloidal solution is preferably 5~21mg / ^{m 2} relative to unit surface area of the crystallites of the metal compound, and more preferably 5 to 15 mg / ^{m 2.} When the content of polyacrylic acid is within the above range, the aggregate of metal compound crystallites has a small particle size and is uniform, and a colloidal solution having excellent storage stability can be obtained. On the other hand, when the content of polyacrylic acid is less than the lower limit, the surface of the metal compound crystallite cannot be sufficiently covered with the polymer dispersant, and the crystallites aggregate to form larger aggregates. On the other hand, when the upper limit is exceeded, a large amount of free polymer dispersant is present in the colloidal solution, so that it tends to be adsorbed on a large number of crystallites and a larger aggregate remains.

  Moreover, it is preferable to adjust pH of the obtained colloid solution to 5.0-10.0, and it is more preferable to adjust to 6.0-9.0. In particular, when using polyacrylic acid having a proportion of all repeating units having a hydrophilic group of 90% or more and 100% or less, the pH of the colloidal solution should be adjusted to 5.0 or more and 10.0 or less. Is more preferable. In addition, when the ratio of the repeating unit having a hydrophilic group is 50% or more and less than 90% (more preferably 75% or more and less than 90%), the pH of the colloidal solution is 7.0 or more and 10.0 or less. It is more preferable to adjust. By adjusting the pH of the colloidal solution to the above range, a uniform aggregate of metal compound crystallites having a small particle diameter can be obtained, and a colloidal solution excellent in storage stability can be obtained. On the other hand, since the carboxyl group of polyacrylic acid does not dissociate when the pH is lower than the lower limit, the amount of adsorption of polyacrylic acid on the metal compound crystallites is reduced, and the crystallites tend to further aggregate, Exceeding the upper limit depends on the type of metal compound, but the surface of the metal compound crystallites tends to be negatively charged, the amount of adsorption of polyacrylic acid from which carboxyl groups are dissociated decreases, and the crystallites tend to aggregate further It is in.

Further, in the region where the first raw material solution and the second feedstock solution is introduced, respectively, shear rate 3000 sec ^-1 or more (more preferably 6000Sec ^-1 or more) to be set to be preferred. 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 tend to remain.

  In the method for producing a catalyst carrier of the present invention, when the colloid solution is obtained, the pH condition is adjusted so that the colloid solution can maintain a dispersed state in the liquid. The pH condition is appropriately set depending on the polymer dispersant to be used. When polyalkyleneimine is used as the polymer dispersant, the pH condition may be 1.0 to 6.0 for the reasons described above. preferable. On the other hand, when polyacrylic acid is used as the polymer dispersant, the pH condition is preferably 5.0 to 10.0, and more preferably 6.0 to 9.0, for the reasons described above. Here, the state in which the colloidal solution can maintain the state dispersed in the liquid means a state in which the aggregation of the nanoparticles and the aggregates in the colloidal solution does not substantially proceed.

(Hydrothermal process)
Next, in the method for producing an exhaust gas purifying catalyst carrier of the present invention, the colloidal solution is hydrothermally treated. The hydrothermal treatment temperature in the hydrothermal treatment step according to the present invention needs to be in the range of 70 to 90 ° C. If the temperature is lower than the lower limit, the crystallization of the aluminum compound becomes insufficient, and solid solutions of ceria and other metal oxides (ceria / zirconia solid solution, ceria / yttria solid solution, ceria / zirconia / yttria solid solution, etc.) are formed. In this case, the rearrangement of atoms is less likely to occur. On the other hand, when the temperature exceeds the above upper limit, the specific surface area of the catalyst carrier is reduced, and furthermore, only the ceria is separated and deposited alone, so that the heat resistance of the catalyst is likely to be lowered. In addition, the hydrothermal treatment temperature is such that when an aluminum compound is precipitated, the specific surface area is increased, and a solid solution of ceria and other metal oxides is formed, the rearrangement of atoms is promoted. Is preferably 80 to 90 ° C. from the viewpoint that the formation of can be suppressed.

  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.

(Aggregation process)
Next, in the method for producing an exhaust gas purifying catalyst carrier of the present invention, it is preferable to adjust the pH of the colloidal solution subjected to the hydrothermal treatment to a pH condition that cannot maintain the state in which the colloidal solution is dispersed in the liquid.

  The pH condition in which the colloidal solution in this step cannot be dispersed in the liquid is appropriately set depending on the polymer dispersant used, but when polyalkyleneimine is used as the polymer dispersant, the pH condition is 9. It is preferably 0 to 12.0, and more preferably 9.5 to 10.5. On the other hand, when polyacrylic acid is used as the polymer dispersant, it is agglomerated in the method for producing an exhaust gas purifying catalyst carrier of the present invention from the viewpoint of suppressing partial dissolution of aluminum compound particles when the pH is set to the acidic side. The process may not be included. Here, the state where the colloidal solution cannot be maintained dispersed in the liquid means a state where the aggregation of the nanoparticles and the aggregates in the colloidal solution proceeds instantaneously.

  The method for adjusting the pH in this step is not particularly limited. For example, the pH may be adjusted within a predetermined range by adding an alkali such as ammonia water or an acid such as nitric acid.

  In this process, the polymer dispersant is desorbed from the nanoparticles and the aggregates in the colloidal solution, and the aggregation of the nanoparticles and the aggregates proceeds instantaneously to form a uniform dispersion state of two or more types of composite metal oxides. Maintained agglomerates are 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.

(Heat treatment process)
Next, in the method for producing an exhaust gas purification catalyst carrier of the present invention, the aggregate obtained in the aggregation step is degreased and heat treated to obtain the exhaust gas purification catalyst carrier of the present invention.

  Although it does not restrict | limit especially as degreasing conditions in this process, In an oxidizing atmosphere (for example, air), it dries on the conditions for 1 to 10 hours at 80-100 degreeC, Then, it is 1-5 hours at 300-400 degreeC. It is preferable to degrease under conditions.

  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, the sintering is not completed, so that the sintering progresses when the catalyst is used, and the catalyst performance is significantly lowered. On the other hand, when the temperature exceeds the upper limit, the specific surface area decreases, the average crystallite diameter of the second ultrafine particles increases, the central pore diameter increases, and the pore volume decreases, resulting in catalyst performance. Decreases. Moreover, as such heat processing temperature, it is especially preferable that it is 800-1050 degreeC from a viewpoint that the more outstanding catalyst performance 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 compounds constituting the aggregates tend not to be sufficiently metal oxides. On the other hand, if the upper limit is exceeded, it tends to be accompanied by performance degradation such as sintering due to high temperature and oxidizing atmosphere. There is a tendency.

In the method for producing an exhaust gas purification catalyst carrier according to the present invention, the exhaust gas purification catalyst carrier comprising a mixture of the first ultrafine particles containing alumina and the second ultrafine particles containing ceria is further added to CuAl ₂ O ₄ and CuO. In the case of further adding an additive component such as the above, a step of further adding the additive component may be included. The method of adding such an additive component is not particularly limited, but for example, a method of preparing a colloidal solution containing Cu similarly to the colloidal solution and homogeneously mixing the colloidal solution containing Cu together with the colloidal solution is preferable. Used for.

  Next, the manufacturing method of the exhaust gas purifying catalyst of the present invention will be described. The method for producing a catalyst of the present invention is a method comprising a step of supporting any one selected from the group consisting of metals and transition metal compounds on the surface of an exhaust gas purifying catalyst carrier obtained by the production method of the present invention. is there. A specific method for supporting such a metal and a transition metal compound is not particularly limited. For example, a salt of a metal and a transition metal compound (nitrate, chloride, acetate, etc.) or a complex of a metal and a transition metal compound is added to water. A method of immersing the exhaust gas-purifying catalyst carrier in a solution dissolved in a solvent such as alcohol, removing the solvent, and firing and pulverizing is preferably used. The drying conditions for removing the solvent in the step of supporting the metal and transition metal compound are preferably within 30 minutes at 30 to 150 ° C. The firing conditions are in an oxidizing atmosphere (for example, air). In this case, the temperature is preferably from 250 to 600 ° C. for about 30 to 60 minutes. Moreover, you may repeat such a metal and transition metal compound 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
<Colloid solution preparation process>
First, 7.2 g of ammonium cerium nitrate, 3.2 g of zirconyl oxynitrate, 1.0 g of yttrium nitrate, and 27.0 g of aluminum nitrate are dissolved in 500 g of ion-exchanged water to contain a cation that is a raw material for the composite metal oxide. A raw material solution was prepared. These addition amounts correspond to a cation concentration of 0.1 mol / L and Al: Ce: Zr: Y = 73: 17: 7: 3 (molar ratio). Next, 31.3 g of ammonium nitrate, 62.5 g of polyethyleneimine having a weight average molecular weight of 10,000 represented by the following formula (1), and 115 g of nitric acid were dissolved in 385 g of ion-exchanged water to prepare a second raw material solution. The amount of polyethyleneimine added corresponds to 6.7 mg / m ² per surface area of the crystallite of the metal compound.

Next, to prepare a colloidal solution containing _Al 2 _{O 3} and _{CeO 2 -ZrO 2 -Y 2 O 3} 3 -component metal compound using the manufacturing 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 2.5 ml / min, and mixed. al ₂ was O ₃ and _{CeO 2 -ZrO 2 -Y 2 O 3} 3 colloid containing a ternary metal compound solution (pH 1.0) was prepared.

The outer diameter of the rotor 11 was 18.4 mm, the gap between the rotor 11 and the outer stator 12 was 0.2 mm, and the shear rate in the region between them was 16000 sec ⁻¹ . The outer diameter of the inner stator 13 was 12.0 mm, the gap between the rotor 11 and the inner stator 13 was 0.5 mm, and the shear rate in the region between them was 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.

<Hydrothermal treatment process>
The obtained colloidal solution was put into a sealed container, heated to 80 ° C. and maintained, and subjected to a hydrothermal treatment for 24 hours while maintaining the pressure in the sealed container within a range of 0.1 to 1.0 MPa. Thereafter, the hydrothermally treated solution was cooled to room temperature.

<Aggregation process>
The aqueous colloid solution after hydrothermal treatment was adjusted to pH 9.5 by adding ammonia water for 10 seconds while stirring to obtain an aggregate.

<Heat treatment process>
The obtained agglomerates are dried by holding at 100 ° C. for 10 hours in the atmosphere, then degreased by holding at 250 ° C. for 5 hours in the atmosphere, and then heat-treated under the condition of holding at 900 ° C. for 5 hours in the atmosphere. A catalyst carrier which is a metal oxide porous body was obtained. In the resulting catalyst support, the content of each metal oxide as shown in Table 5, _Al 2 _{O 3} is 47.4 wt%, CeO ₂ 37.3 wt%, ZrO ₂ is 11.5 wt %, Y ₂ O ₃ was 3.9% by mass.

(Example 2)
A catalyst carrier was obtained in the same manner as in Example 1 except that the heat treatment temperature was 950 ° C.

Example 3
Except that 31.3 g of ammonium nitrate, 70 g of ammonium polyacrylate having a weight average molecular weight of 2000 hydrophilic group of 100%, and a solution of 10 g of 25% by mass of ammonia water in 420 g of ion-exchanged water were used as the second raw material solution. A colloidal solution (pH 6.5) was prepared in the same manner as in Example 1. Using this colloidal solution, the colloidal solution after hydrothermal treatment was degreased as it was without performing the agglomeration step, the thermal treatment temperature was 1000 ° C., and the shear rate in the region between the rotor 11 and the inner stator 13 was 32500 sec ⁻¹ . A catalyst carrier was obtained in the same manner as in Example 1 except that. In addition, the addition amount of this polyacrylic acid is equivalent to 6.7 mg / m < ² > per surface area of a metal compound crystallite.

Example 4
A catalyst carrier was obtained in the same manner as in Example 1 except that the heat treatment temperature was 1000 ° C.

(Example 5)
A catalyst carrier was obtained in the same manner as in Example 1 except that the heat treatment temperature was 1050 ° C.

(Comparative Example 1)
A catalyst carrier was obtained in the same manner as in Example 1 except that the heat treatment temperature was 600 ° C.

(Comparative Example 2)
A catalyst carrier was obtained in the same manner as in Example 1 except that the heat treatment temperature was 1100 ° C.

(Comparative Example 3)
A colloidal solution was prepared in the same manner as in Example 1 except that the first raw material solution and the second raw material solution were rapidly introduced and mixed by propeller stirring for 12 hours at 300 rpm. Using this colloidal solution, a catalyst carrier was obtained in the same manner as in Example 1 except that the heat treatment temperature was 1100 ° C.

(Comparative Example 4)
A catalyst carrier was obtained in the same manner as in Example 1 except that a solution obtained by dissolving 40 g of 25% by mass of ammonia water in 460 g of ion-exchanged water was used as the second raw material solution.

(Comparative Example 5)
A catalyst carrier was obtained in the same manner as in Example 1 except that the hydrothermal treatment temperature was 100 ° C.

(Comparative Example 6)
A catalyst carrier was obtained in the same manner as in Example 1 except that the hydrothermal treatment temperature was not used.

(Example 6)
A solution prepared by dissolving 12.3 g of ammonium cerium nitrate, 2.6 g of zirconyl oxynitrate, 1.3 g of yttrium nitrate, and 24.1 g of aluminum nitrate in 500 g of ion-exchanged water is used as the first raw material solution and added to the second raw material solution. A catalyst support was obtained in the same manner as in Example 1 except that 32.6 g of ammonium nitrate was used instead of 31.3 g. The addition amount in the first raw material solution corresponds to a cation concentration of 0.1 mol / L and Al: Ce: Zr: Y = 64: 23: 10: 3 (molar ratio). In the obtained catalyst carrier, the content of alumina was 37.5% by mass. Table 5 shows the content of each metal oxide in the obtained catalyst carrier.

(Example 7)
A solution prepared by dissolving 5.3 g of cerium ammonium nitrate, 1.1 g of zirconyl oxynitrate, 0.6 g of yttrium nitrate, and 31.7 g of aluminum nitrate in 500 g of ion-exchanged water is used as the first raw material solution and added to the second raw material solution. A catalyst carrier was obtained in the same manner as in Example 1 except that 31.8 g of ammonium nitrate was used instead of 31.3 g. The addition amount in the first raw material solution corresponds to a cation concentration of 0.1 mol / L and Al: Ce: Zr: Y = 84: 9: 4: 1 (molar ratio). In the obtained catalyst carrier, the content of alumina was 64.3% by mass. Table 5 shows the content of each metal oxide in the obtained catalyst carrier.

(Example 8)
A solution prepared by dissolving 4.2 g of ammonium cerium nitrate, 0.9 g of zirconyl oxynitrate, 0.4 g of yttrium nitrate, and 33.0 g of aluminum nitrate in 500 g of ion-exchanged water is used as the first raw material solution and added to the second raw material solution. A catalyst carrier was obtained in the same manner as in Example 1 except that 31.7 g of ammonium nitrate was used instead of 31.3 g. The addition amount in the first raw material solution corresponds to a cation concentration of 0.1 mol / L and Al: Ce: Zr: Y = 88: 8: 3: 1 (molar ratio). In the obtained catalyst carrier, the content of alumina was 70.6% by mass. Table 5 shows the content of each metal oxide in the obtained catalyst carrier.

Example 9
A solution prepared by dissolving 13.3 g of ammonium cerium nitrate, 1.0 g of yttrium nitrate, and 27.4 g of aluminum nitrate in 500 g of ion-exchanged water was used as the first raw material solution, and the ammonium nitrate added to the second raw material solution was replaced with 31.3 g. A catalyst carrier was obtained in the same manner as in Example 1 except that the amount was 33.7 g. The addition amount of the salt containing a cation in the aqueous solution corresponds to a cation concentration of 0.1 mol / L and Al: Ce: Zr: Y = 73: 24: 0: 3 (molar ratio). In the obtained catalyst carrier, the alumina content was 45.3 mass%. Table 5 shows the content of each metal oxide in the obtained catalyst carrier.

(Example 10)
A solution prepared by dissolving 6.0 g of ammonium cerium nitrate, 3.6 g of zirconyl oxynitrate, 1.0 g of yttrium nitrate, and 27.4 g of aluminum nitrate in 500 g of ion-exchanged water is used as the first raw material solution and added to the second raw material solution. A catalyst carrier was obtained in the same manner as in Example 1 except that 31.0 g of ammonium nitrate was used instead of 31.3 g. In addition, the addition amount in the aqueous solution of the salt containing a cation corresponds to a cation concentration of 0.1 mol / L and Al: Ce: Zr: Y = 73: 6: 4: 1 (molar ratio). In the obtained catalyst carrier, the content of alumina was 47.5% by mass. Table 5 shows the content of each metal oxide in the obtained catalyst carrier.

(Comparative Example 7)
Commercially available alumina powder (trade name: AKP-50, manufactured by Sumitomo Chemical Co., Ltd.) was used as the catalyst carrier.

(Comparative Example 8)
Commercially available ceria powder (trade name: cerium oxide, manufactured by Daiichi Rare Element Chemical Industries, Ltd.) was used as the catalyst carrier.

<Characteristic evaluation>
Each characteristic of the catalyst carrier obtained in Examples 1 to 10 and Comparative Examples 1 to 8 was measured and evaluated by the following methods.
(Average crystallite diameter)
The X-ray diffraction (XRD) pattern of the catalyst carrier was measured using a powder X-ray diffractometer (trade name “RINT-2200”, manufactured by Rigaku Corporation) with a scan step of 0.01 °, a divergence and scattering slit of 1 deg, a light receiving slit of 0. Based on the full width at half maximum of the peak derived from the (111) plane of the obtained second ultrafine particle, measured under the conditions of 15 mm, CuKα ray, 40 kV, 20 mA, scan speed of 1 ° / min, 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)
The average crystallite diameter of the second fine particles was calculated. Table 1 shows the average crystallite diameters of the second ultrafine particles in the catalyst carriers obtained in Examples 1 to 5 and Comparative Examples 1 to 6, and Table 3 shows those obtained in Examples 1 and 6 to 10. The average crystallite diameter of the second ultrafine particles in the catalyst carrier is shown. In the catalyst support obtained in Comparative Example 5, it was confirmed by measurement by X-ray diffraction that the zirconia solid solution ceria crystals having a fluorite structure were destroyed. Therefore, in the catalyst carrier obtained in Comparative Example 5, the crystallite diameter of the second fine particles could not be measured.

(Specific surface area, center pore diameter, pore volume)
Nitrogen adsorption of the catalyst support by a constant volume gas adsorption method under conditions of liquid nitrogen temperature (-196 ° C.) using an automatic specific surface area / pore distribution measuring device (trade name “Autosorb-1” manufactured by Cantachrome Co., Ltd.) An isotherm was determined. The catalyst carrier was vacuum degassed at 120 ° C. for 2 hours before measurement. From the obtained nitrogen adsorption isotherm, the pore size distribution curve of the catalyst support was determined by the BJH method, and the center pore diameter of the catalyst support was calculated. Further, the pore volume of the catalyst support was calculated from the nitrogen adsorption isotherm, and the specific surface area of the catalyst support was calculated by the BET method. Table 1 shows specific surface areas, central pore diameters and pore volumes of the catalyst supports obtained in Examples 1 to 5 and Comparative Examples 1 to 6, and Table 3 shows examples obtained in Examples 1 and 6 to 10. The specific surface area, central pore diameter and pore volume of the catalyst support obtained are shown.

(standard deviation)
First, with respect to the obtained catalyst support, using an EDS apparatus (200 KV TEM, ADF-STEM image) attached to STEM (manufactured by JEOL, JEM-2100F Cs collector), Al, Ce, Zr, and Y in an area of 20 nm square. The content rate (content rate in terms of metal (mass%)) was measured at 300 measurement points. Next, with respect to the obtained catalyst support, an ICP emission analyzer (manufactured by Rigaku Corporation, CIROS 120EOP) was used to measure the total metal mass and each mass of Al, Ce, Zr, Y in the catalyst support. Each content (mass%) of Al, Ce, Zr, and Y with respect to the total mass of the metal was calculated. Based on the content of each metal in the entire catalyst support thus obtained, the standard deviation of the measured value of the content of each metal at all measurement points was calculated. The results for the catalyst carriers obtained in Examples 1 to 5 and Comparative Examples 1 to 6 are shown in Table 2, and the results for the catalyst carriers obtained in Examples 1 and 6 to 10 are shown in Table 4.

<Catalyst activity evaluation>
The catalyst activities of the catalyst carriers obtained in Examples 1 to 10 and Comparative Examples 1 to 8 were measured and evaluated by the following methods.

First, using a copper nitrate aqueous solution in which 0.951 g of copper nitrate (Cu (NO ₃ ) ₂ .3H ₂ O) was dissolved in 584 g of ion-exchanged water, Cu was 0.25 g with respect to 5 g of the obtained catalyst carrier. And calcined at 600 ° C. for 5 hours in the air to obtain a copper-based catalyst. In this catalyst, copper oxide particles are supported on a catalyst carrier, and when exposed to a reducing atmosphere, a part of the copper oxide is reduced to copper particles and exhibits catalytic activity.

Next, 1.0 g of the obtained catalyst was placed in an atmospheric pressure fixed bed flow type reactor (manufactured by Vest Sokki), and CO (0.7 vol%), H ₂ (0.23 vol%), NO (0 .12 volume%), C ₃ H ₆ (0.16 volume%), CO ₂ (10 volume%), O ₂ (0.64 volume%), H ₂ O (3 volume%) and N ₂ (balance) Was supplied at a flow rate of 3500 mL / min, the catalyst-containing gas temperature was adjusted to 100 ° C., and the CO concentration, C ₃ H ₆ concentration, and NO concentration of the catalyst-containing gas were measured. Thereafter, a pretreatment was performed in which the temperature of the gas containing the catalyst was increased to 500 ° C. at a temperature increase rate of 50 ° C./min and held for 10 minutes. Next, after cooling the catalyst-containing gas to 100 ° C., the temperature of the catalyst-containing gas is increased again to 600 ° C. at a rate of temperature increase of 15 ° C./min, while the CO concentration, C ₃ H ₆ concentration, NO The concentration was measured, and the NO purification rate was calculated from the difference between the measured values of the catalyst-containing gas and the catalyst output gas. And the temperature (T50-NO) at which the NO purification rate in the supplied model gas reaches 50% was measured. Table 5 shows the results obtained in Examples 1 and 6 to 10 and Comparative Examples 7 to 8. Moreover, T50-NO (degreeC) obtained in Examples 1-5 and Comparative Examples 1-6 was made into the vertical axis | shaft, and the average crystallite diameter of the 2nd ultrafine particle in the support | carrier obtained in each Example and the comparative example was used. FIG. 5 shows (nm) as the horizontal axis. However, in Comparative Example 5, since the crystallite size of the second ultrafine particles could not be measured, the average crystallite size is assumed to be 10 nm.

As is apparent from the results shown in Tables 1 to 4, according to the production method of the present invention, metal oxide nanoparticles (alumina particles, ceria particles) having two or more phases arranged in a highly uniform manner are physically mixed. It was confirmed that the exhaust gas purifying catalyst carrier of the present invention can be obtained. When the exhaust gas-purifying catalyst carrier of the present invention is used as a catalyst carrier, Al ₂ O ₃ nanoparticles are finely and uniformly arranged between functional particles (ceria-containing nanoparticles) as a diffusion barrier. It becomes a carrier having excellent heat resistance. Furthermore, according to the present invention, since the specific surface area, pore diameter and pore volume can be controlled, it is possible to prepare a carrier according to the supported metal or metal compound species, and to prepare a catalyst exhibiting excellent activity. It becomes possible.

  Further, as is clear from the comparison between Example 1 and Comparative Examples 5 to 6, it was confirmed that the heat resistance is improved because the specific surface area is increased by performing the hydrothermal treatment according to the present invention. On the other hand, since the crystal structure of the fluorite-structured zirconia solid solution ceria particles is destroyed when the temperature of the hydrothermal treatment is increased, it was confirmed that uniform crystals having a sufficient specific surface area cannot be formed.

  Furthermore, as is apparent from the results shown in FIG. 5, the exhaust gas-purifying catalyst carrier of the present invention having the second ultrafine particle average crystallite diameter of 5 to 11 nm is excellent in catalytic activity and is out of the range. It was confirmed that the catalytic activity deteriorated rapidly.

  Moreover, in the exhaust gas purifying catalyst carrier of the present invention, it was confirmed that the catalyst activity was particularly excellent when the alumina content was in the range of 30 to 80% by mass. This is presumably because alumina particles act as a diffusion barrier even in heat treatment at a high temperature, and control the crystallite size of ceria particles and / or zirconia solid solution ceria particles.

  As described above, according to the present invention, even when a transition metal compound is used as a supported catalyst component, it is possible to obtain a catalyst carrier for exhaust gas purification that can obtain a catalyst having a high level of catalytic activity. In addition, it is possible to provide a manufacturing method thereof.

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

Claims (10)

A catalyst carrier for exhaust gas purification comprising a mixture of first ultrafine particles containing alumina and second ultrafine particles containing ceria,
All metal elements contained in the carrier in an amount of 0.1% by mass or more are analyzed by energy dispersive X-ray spectroscopy using a scanning transmission electron microscope with a spherical aberration correction function. The first ultrafine particles and the second fine particles are so satisfied that the standard deviation of the content of each metal element obtained by measuring the content (mass%) at 300 measurement points is 10 or less. Ultra fine particles are uniformly dispersed,
The specific surface area determined by the BET method is 110 m ² / g or more,
An exhaust gas purifying catalyst carrier, wherein the second ultrafine particles have an average crystallite diameter of 5 to 11 nm determined by an X-ray diffraction method. 2. The exhaust gas purifying catalyst carrier according to claim 1, wherein a central pore diameter determined by a nitrogen adsorption method is 8 to 20 nm and a pore volume is 0.2 to 0.6 cm ³ / g.   The exhaust gas purifying catalyst carrier according to claim 1 or 2, wherein the second ultrafine particles further contain zirconia and / or yttria.   The exhaust gas purifying catalyst carrier according to any one of claims 1 to 3, wherein the content of alumina is 30 to 80% by mass.   An exhaust gas purifying catalyst carrier according to any one of claims 1 to 4, and any one selected from the group consisting of a metal and a transition metal compound supported on the surface of the carrier. An exhaust gas purifying catalyst characterized by. A first raw material solution containing aluminum ions and cerium ions and a second raw material solution containing a polymer dispersant are directly and independently introduced into a region having a shear rate of 1000 to 200000 sec ^−1. Mixing the mixture homogeneously to obtain a colloidal solution;
Adjusting the pH of the colloidal solution to a pH condition capable of maintaining the state in which the colloidal solution is dispersed in the liquid;
Hydrothermally treating the colloidal solution at a temperature of 70 to 90 ° C .;
A method for producing a catalyst carrier for exhaust gas purification, comprising: degreasing the colloidal solution after the hydrothermal treatment and obtaining a catalyst carrier for exhaust gas purification by heat treatment in an oxidizing atmosphere at a temperature of 700 to 1050 ° C. .   The method for producing an exhaust gas purifying catalyst carrier according to claim 6, wherein the first raw material solution further contains zirconium ions and / or yttrium ions.   8. The method according to claim 6, further comprising a step of adjusting the pH of the colloidal solution after the hydrothermal treatment to a pH condition where the colloidal solution cannot maintain a dispersed state in the liquid after the hydrothermal treatment step. The manufacturing method of the catalyst carrier for purification | cleaning of exhaust gas as described.   The polymer dispersant is at least one polyalkyleneimine having a weight average molecular weight of 3000 to 15000, and pH conditions capable of maintaining the state in which the colloidal solution is dispersed in the liquid are 1.0 to 6.0, The method for producing an exhaust gas purifying catalyst carrier according to claim 8, wherein the pH condition under which the colloidal solution cannot be dispersed in the liquid is 9.0 to 11.0.   The polymer dispersant is at least one polyacrylic acid having a weight average molecular weight of 1000 to 5000, and pH conditions capable of maintaining the state in which the colloidal solution is dispersed in the liquid are 5.0 to 10.0. A method for producing an exhaust gas purifying catalyst carrier according to claim 6 or 7.

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