JP5116276B2 - Powder comprising oxide microcrystal particles, catalyst using the same, and method for producing the same - Google Patents

Description

  The present invention relates to a powder comprising fine oxide crystal particles, a catalyst using the same, and a method for producing the same.

  Fine particles, especially nanometer-sized particles (nanoparticles) exhibit various unique and excellent properties, characteristics, and functions, so they are more accurate and more compact than all current materials and products. It is expected to realize a technology that satisfies the demand for lighter weight. In this way, the nanoparticle is a ceramic nanostructure modifier, an optical functional coating material, an electromagnetic shielding material, a secondary battery material, a fluorescent material, an electronic component material, a magnetic recording material, an industrial material such as an abrasive material, It is attracting attention as a material that enables high functionality, high performance, high density, and high precision for pharmaceuticals and cosmetics.

Under such circumstances, for example, Japanese Patent Application Laid-Open No. 2003-47849 (Patent Document 1) is an exhaust gas purification catalyst in which a catalytic metal element is supported on a supporting base material in which ceria is highly dispersed in alumina. The ratio I ₂₀₀ / I ₁₁₁ of the integrated intensity I ₂₀₀ of the (200) plane diffraction peak to the integrated intensity I ₁₁₁ of the (111) plane diffraction peak by X-ray diffraction contains ceria that exceeds 0.4. A featured exhaust gas purification catalyst is disclosed.

  However, in the exhaust gas purifying catalyst described in Patent Document 1, since the crystal plane can be controlled only by supporting ceria in a highly dispersed state on the alumina carrier, the ceria alone that has controlled the crystal plane is used. Since particles cannot be obtained and there is a great restriction on the composition, there is a problem that a composition in which an arbitrary component is supported on ceria cannot be obtained.

In Patent Document 1, a conclusion that the ratio of ceria grown in the (200) plane direction is increased from the phenomenon that the ratio I ₂₀₀ / I ₁₁₁ exceeds 0.4 is derived. The inventors believe that the conclusion is inaccurate for the following reasons. That is, the ceria particles described in the same document should have grown in an arbitrary crystal orientation in the gap of the alumina carrier, and it is impossible to separate from alumina even when measuring X-ray diffraction. , It should remain in any crystal orientation. The fact that the ceria is in a highly dispersed state tends to decrease the crystallite diameter, and thus the phenomenon that the ratio I ₂₀₀ / I ₁₁₁ increases is understood in a form associated with the change in the crystallite diameter. It should not be said that the proportion of ceria grown in the (200) plane direction is increasing.

  K.K. Zhou et al. , J .; Catalysis 229 (2005) p. In 206-212 (Non-patent Document 1), cerium nitrate is neutralized with sodium hydroxide, treated under hydrothermal conditions of 100 ° C. for 10 hours, washed, filtered, dried at 60 ° C., and further at 350 ° C. It is disclosed that a rod-shaped ceria single crystal having a thickness of about 20 nm and a length of about 200 nm can be obtained by firing for 4 hours. It is described that the rod-like ceria single crystal is a rectangular parallelepiped having an end face made of (110) face and side faces made of (110) face and (001) face, and further the main surface of the conventional ceria nanoparticles. It is described that the (111) plane is very stable, whereas the (110) plane is slightly less stable and the (001) plane has a higher surface energy and is active.

  However, the rod-shaped ceria single crystal described in Non-Patent Document 1 has a problem that the (001) plane is 50% or less and the ratio of the active (001) plane cannot be increased further. In addition, the rod-shaped ceria single crystal is easily increased in viscosity by adding a small amount when preparing a catalyst slurry, and further, the rod-shaped crystal is broken during the mixing process and the ratio of the active (001) plane is reduced. there were.

  Furthermore, Japanese Patent Application Laid-Open No. 2005-193237 (Patent Document 2) discloses a method for producing organic modified metal oxide fine particles in the presence of an organic modifier in a reaction field in a supercritical hydrothermal synthesis method. In the Examples, a method is described in which hydrogen peroxide is added to an aqueous cerium nitrate solution and organically modified metal oxide fine particles are produced by high-temperature, high-pressure hydrothermal synthesis in the presence of hexanoic acid.

However, in the method for producing metal oxide fine particles described in Patent Document 2, although crystal growth is suppressed by organic modification to obtain highly crystalline nanoparticles, the crystal of metal oxide fine particles obtained in the same document is obtained. The present invention does not necessarily consider the aspect, and the method described in this document is not necessarily sufficient in that the improvement in the ratio of the metal oxide fine particles composed of active crystal faces is limited. Found them.
JP 2003-47849 A K. Zhou et al. , J .; Catalysis 229 (2005) p. 206-212 JP 2005-193237 A

  The present invention has been made in view of the above-described problems of the prior art, and is capable of producing oxide microcrystal particles capable of significantly improving the ratio of oxide crystallite particles having an active crystal plane as compared with the prior art. The present invention provides a powder in which fine oxide crystal particles composed of active crystal planes, which could not be obtained in the past, account for 50% by mass or more, and further used for low temperature and high temperature catalytic activity. The object is to provide an excellent catalyst.

As a result of intensive research aimed at achieving the above object, the present inventors have conducted oxidation in a method for synthesizing microcrystalline oxide particles in the presence of a specific organic substance in a reaction field in a high-temperature and high-pressure hydrothermal synthesis method. In order to complete the present invention, it has been found that the ratio of oxide microcrystal particles comprising active crystal planes is greatly improved by using as a raw material a hydroxide of a specific cation that should constitute the product microcrystal particles. It came.

That is, the method for producing a powder composed of oxide fine crystal particles according to the present invention includes a hydroxide of Ce, which is a cation that should form oxide fine crystal particles, in a reaction field in a high-temperature and high-pressure hydrothermal synthesis method. Oxide microcrystal particles having an outermost surface composed of an oxygen ion layer by synthesizing oxide microcrystal particles in the presence of a carboxylic acid having 6 to 10 carbon atoms from a hydroxide of Ce and La Is a method characterized by obtaining a powder composed of oxide crystallite particles comprising 50% by mass or more . In the present invention, the ratio (molar ratio) between the cation hydroxide and the carboxylic acid is preferably 5: 1 to 1:10.

Then, as the hydroxides of the cations according to the present invention, hydroxides of Ce, or Ru der those containing a hydroxide of Ce hydroxide and La. When such La is contained, the content is preferably 3 to 20 mol% based on the total amount of Ce and La . Also, the powder made of oxide fine crystal particles of the present invention, oxide fine crystal grains consisting of sintered outermost surface made by oxygen ion layer planes (active crystal surface) accounts for more than 50 wt% It is characterized by being.

In the present invention, the active crystal plane preferably satisfies at least one of the following conditions (i) to (iii).
(I) The coordination number of cations with respect to oxygen ions on the outermost surface constituting the active crystal plane is 2 or less.
(Ii) The active crystal plane is an unstable crystal plane with high surface energy.
(Iii) The oxide microcrystalline particles comprising the active crystal plane have a fluorite structure, and the active crystal plane is a crystal plane that is crystallographically equivalent to the (001) plane and the (001) plane. Be.

Further, cations constituting the oxide fine crystal particles according to the present invention, Ce, or Ru der those containing Ce and La. When such La is contained, the content is preferably 3 to 20 mol% based on the total amount of Ce and La .

  Furthermore, the oxide microcrystal particles comprising the active crystal plane preferably have an average particle size in the range of 2 nm to 30 nm, and more preferably monodisperse nanocrystal particles.

  The catalyst of the present invention is characterized by comprising a powder comprising the oxide microcrystal particles of the present invention and a catalytically active species supported on the surface of the powder. The catalytically active species is preferably at least one selected from the group consisting of oxides of transition elements and noble metals.

  In the method for producing a powder comprising fine oxide crystal particles of the present invention, an active crystal plane (001 in the case of a fluorite structure) having an outermost surface constituted by an oxygen ion layer by an organic substance (surface modifier molecule). The reason why the surface) is selectively grown is not necessarily clear, but the present inventors infer as follows. That is, first, the nucleus of the crystal is generated at the initial stage of growth of the oxide crystal. And the organic substance (surface modifier molecule) reacts with the crystal surface with high reactivity ((001) surface in the case of fluorite structure) because the surface energy is high and unstable with respect to the nucleus. Stabilized. On the other hand, on the crystal face other than the crystal face that has been stabilized by reacting with the surface modifier molecule, the precipitation of the oxide continues and the face disappears. As a result, it is surmised that only the crystal plane stabilized by the surface modifier molecule is obtained. Further, in the reaction field in the high-temperature and high-pressure hydrothermal synthesis method, particularly in supercritical water, the surface modifier molecules are uniformly dissolved and can react efficiently by contacting with the crystal plane of the oxide. Therefore, the present inventors speculate that oxide microcrystal particles having an unstable crystal plane with high surface energy can be obtained at a high rate.

  Further, although the reason why the low-temperature and high-temperature catalytic activity is improved according to the catalyst of the present invention obtained using the powder comprising the oxide microcrystal particles of the present invention is not necessarily clear, the present inventors We infer as follows. That is, in the crystal structure of an oxide, there are generally a crystal plane that is densely filled with oxygen, a crystal face that is densely filled with cations, and a crystal face that is filled with both. In general, the morphology of crystal grains with crystal planes that are densely filled with oxygen is thermodynamically unstable. The reason is that from the viewpoint of the charge balance of the crystal, the surface has a structure in which only half of the oxygen is filled, and there is almost no structural restriction on oxygen ions. For example, a crystal plane having a cation coordination number of 2 or less with respect to oxygen ions on the outermost surface, such as a (001) plane having a fluorite structure and a crystal plane equivalent to the (001) plane, is a surface. Energy is high. The oxygen in this state is more active than oxygen molecules in the air and preferentially contributes to the oxidation reaction on the oxide surface. In addition, since oxygen ion vacancies can be easily formed in which oxygen molecules in the gas phase are easily dissociated and adsorbed, oxygen necessary for the oxidation reaction is easily supplied and high oxidation activity is obtained. This ability to absorb and release oxygen from a low temperature simultaneously contributes to the activation of the reduction reaction. Therefore, the book obtained by using the powder comprising the oxide microcrystal particles of the present invention in which the oxide microcrystal particles comprising the active crystal plane composed of the oxygen ion layer on the outermost surface account for 50% by mass or more. The inventors speculate that low and high temperature catalytic activity will be improved with the inventive catalyst.

  According to the method for producing oxide microcrystal particles of the present invention, the ratio of oxide crystallite particles composed of active crystal faces can be significantly improved as compared with the conventional method. Therefore, according to the present invention, it is possible to provide a powder of oxide microcrystal particles in which the oxide crystallite particles composed of active crystal faces that could not be obtained conventionally account for 50% by mass or more, Furthermore, it becomes possible to provide a catalyst excellent in low-temperature and high-temperature catalytic activity using it.

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

  First, the powder comprising the oxide crystallite particles of the present invention will be described. The powder composed of oxide microcrystal particles of the present invention is characterized in that the oxide microcrystal particles composed of an active crystal plane whose outermost surface is constituted by an oxygen ion layer account for 50% by mass or more. It is.

  The oxide according to the present invention is not particularly limited as long as it can form microcrystalline particles. As a metal element constituting such an oxide, Group IIIB boron (B) to Group IVB silicon (Si) to Group VB arsenic (As) to Group VIB in the long-period periodic table. Examples include elements on the line with the line of tellurium (Te) as well as those on the left or lower side of the long-period periodic table from the boundary. For example, elements of Group VIII include Fe, Co, Ni, Ru , Rh, Pd, Os, Ir, Pt, etc., group IB elements such as Cu, Ag, Au, etc., group IIB elements such as Zn, Cd, Hg, etc., group IIIB elements such as B, Al, Ga, In, Tl, etc., Group IVB elements such as Si, Ge, Sn, Pb, etc., Group VB elements As, Sb, Bi, etc., Group VIB elements such as Te, Po, etc., and Groups IA to VIIA These elements are mentioned.

Therefore, the metal oxide according to the present invention includes Fe, Co, Ni, Cu, Ag, Au, Zn, Cd, Hg, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Ti, Zr, Examples include oxides such as Mn, Eu, Y, Nb, Ce, and Ba. For example, SiO ₂ , TiO ₂ , ZnO ₂ , SnO ₂ , Al ₂ O ₃ , MnO ₂ , NiO, Eu ₂ O ₃ , Y _2. O ₃ , Nb ₂ O ₃ , InO, ZnO, Fe ₂ O ₃ , Fe ₃ O ₄ , Co ₃ O ₄ , ZrO ₂ , CeO ₂ , BaO · 6Fe ₂ O ₃ , Al ₅ (Y + Tb) ₃ O ₁₂ , BaTiO _{3 3} , LiCoO ₂ , LiMn ₂ O ₄ , K ₂ O.6TiO ₂ .

  In addition, when there are multiple valences of cations (metal elements) constituting the oxide, oxygen on the outermost surface is easily desorbed, so that the activity of the crystal plane is further improved and the catalyst has excellent catalytic activity. Therefore, it is preferable that the cation constituting the oxide according to the present invention is a cation of an element that can take a plurality of valences, and in particular, the influence on the human body tends to be small. From a certain viewpoint, it is more preferably a cation of at least one element selected from the group consisting of Ce, Pr, Fe, Ni, Cu, V, and Co, and a cation of Ce is particularly preferable.

  Furthermore, the cation constituting the oxide according to the present invention contains a cation of Ce and at least one second component cation selected from the group consisting of rare earth elements other than Ce. It is preferable because it tends to keep the crystal form stable even at high temperatures because the volume diffusion of the cation is hindered, and when such a second component is La, the crystal is particularly stable because the ionic radius is large. It is more preferable because the function to be converted tends to be high. Moreover, when such a 2nd component is contained, it is preferable that the content rate is 3-20 mol% on the basis of the total amount of Ce and said 2nd component. If the content of the second component is less than the above lower limit, the effect of addition tends not to be sufficiently obtained. On the other hand, if the content exceeds the upper limit, the effect of changing the valence of Ce is insufficient and the oxygen adsorption / desorption is reduced. There is a tendency.

  The powder of the present invention is composed of fine crystal particles of the above oxide. Examples of the microcrystalline particles according to the present invention include those having an average particle size of about 1 μm or less, and preferably nanoparticles. Such nanoparticles generally include those having an average particle size of 200 nm or less, preferably those having an average particle size of 100 nm or less, and those having an average particle size of 50 nm or less. Is more preferable. Examples of the shape of the microcrystalline particles according to the present invention include pseudo cubic particles, tabular circular particles, tabular elongated particles, and pseudo rectangular parallelepiped particles. Among them, pseudo cubic particles are preferable. The powder according to the present invention is preferably an aggregate of microcrystalline particles having a uniform particle size and shape, but may be a mixture of microcrystalline particles having different particle sizes and shapes.

  In the present invention, in the powder composed of the oxide microcrystal particles, it is necessary that the oxide microcrystal particles composed of an active crystal plane whose outermost surface is constituted by an oxygen ion layer occupy 50% by mass or more. It is preferable that it occupies 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 95% by mass or more. The powder in which the oxide crystallite particles composed of active crystal faces account for 50% by mass or more is obtained for the first time by the production method of the present invention described later. By using the body, a catalyst having dramatically improved low-temperature and high-temperature catalytic activity can be obtained.

  Note that “the outermost surface is composed of an oxygen ion layer” refers to a form in which all surfaces of the oxide microcrystalline particles have crystal planes that are densely filled with oxygen, but are exposed on the outermost surface. It is not necessary that all the sites are oxygen ion sites, but 80% or more of the sites exposed on the outermost surface may be oxygen ion sites, and 90% or more may be oxygen ion sites. More preferably, 100% is particularly preferably an oxygen ion site. As described above, the surface of the oxide microcrystal particle according to the present invention is composed of a crystal plane in which oxygen is densely packed, but the oxygen ions exposed on the outermost surface are actually the same from the viewpoint of the charge balance of the crystal. The number of oxygen ions filled on the surface is about 40 to 90 at% (particularly preferably about 50 at%) of the number of oxygen ions that can be arranged crystallographically. Therefore, there is almost no structural restriction on oxygen ions. Therefore, oxygen ions in such a state are more active than oxygen molecules in the air, and a crystal plane whose outermost surface is constituted by such an oxygen ion layer becomes active. Active oxygen ions preferentially contribute to the oxidation reaction on the oxide surface. In addition, since oxygen ion vacancies can be easily formed in which oxygen molecules in the gas phase are easily dissociated and adsorbed, oxygen necessary for the oxidation reaction is easily supplied and high oxidation activity is obtained. This ability to absorb and release oxygen from a low temperature simultaneously contributes to the activation of the reduction reaction.

In the present invention, the active crystal plane preferably satisfies at least one of the following conditions (i) to (iii).
(I) The coordination number of cations with respect to oxygen ions on the outermost surface constituting the active crystal plane is 2 or less.
(Ii) The active crystal plane is an unstable crystal plane with high surface energy.
(Iii) The oxide microcrystalline particles comprising the active crystal plane have a fluorite structure, and the active crystal plane is a crystal plane that is crystallographically equivalent to the (001) plane and the (001) plane. Be.

  Note that the outermost oxygen ion constituting the active crystal plane, that is, unstable oxygen, has a coordination number of the cation at the nearest position as small as 2 or less. For example, in the case of ceria microcrystalline particles, the Ce ion coordination number of the outermost surface oxygen ion in the (001) plane and a crystallographically equivalent crystal plane to the (001) plane is 2, while the (110) plane The Ce ion coordination number of the outermost surface oxygen ion in the (111) plane is 4.

  The particle size and shape of the oxide microcrystal particles according to the present invention are as described above, but the average particle size of the oxide microcrystal particles composed of the above active crystal plane is in the range of 2 nm to 30 nm. preferable. If the average particle size is less than the lower limit, the heat resistance becomes insufficient and the powder tends to sinter and change to another shape by heating at less than 500 ° C. The specific surface area tends to be insufficient. In addition, as the oxide microcrystal particles having an active crystal face according to the present invention, monodisperse nanocrystal particles are used for forming secondary particles having sufficient voids between the particles and from the viewpoint of increasing heat resistance. And monodisperse monodisperse nanocrystal particles are particularly preferred.

Note that the crystal plane of such oxide microcrystalline particles can be analyzed using HR-TEM (High Resolution Transmission Electron Microscope), electron diffraction method or the like. The crystal composition can be confirmed by EDX analysis or the like, and the particle size of the particles can be measured by TEM, adsorption method, light scattering method, SAXS or the like. The adsorption method is a method for evaluating the BET specific surface area by N ₂ adsorption or the like.

  Next, the manufacturing method of the powder which consists of oxide microcrystal particle | grains of this invention is demonstrated. In the present invention, oxide microcrystal particles are synthesized in the presence of an organic substance from a cation hydroxide that constitutes oxide microcrystal particles in a reaction field in a high-temperature and high-pressure hydrothermal synthesis method.

  As the reaction field in the high-temperature and high-pressure hydrothermal synthesis method according to the present invention, a solvent in a subcritical or supercritical condition (water or a mixed solvent of water and an organic solvent) is preferably employed. Is preferably about 350 to 450 ° C., and the pressure (assumed to be pure water) is preferably about 160 to 500 bar (particularly preferably 300 to 500 bar). By using such a reaction field, a unique reaction environment is provided, and the crystal plane formed by the synergistic action of organic modification of the surface of the oxide microcrystal by a specific organic substance described later is regulated. Surprisingly, it becomes possible to selectively obtain oxide microcrystalline particles having the above-mentioned active crystal face.

  The reaction apparatus for forming such a reaction field is not particularly limited as long as it can achieve conditions of high temperature and high pressure, and for example, either a batch type apparatus or a flow type apparatus can be used.

  In the present invention, it is necessary to use, as a raw material, a hydroxide of a cation (metal element) that constitutes the aforementioned oxide microcrystal particles. The mechanism of action is not clear, but by using such a cation (metal element) hydroxide, it can be produced compared to the conventional case of using a cation (metal element) salt (nitrate, etc.). The ratio of the oxide fine crystal particles having the above active crystal face in the powder to be greatly improved, and the powder of the present invention can be obtained. The method for obtaining a cation (metal element) hydroxide is not particularly limited. For example, a solution containing a cation (metal element) salt is neutralized with an alkali (potassium hydroxide, sodium hydroxide, etc.). The resulting precipitate is washed as necessary and then redispersed in water.

  The organic substance according to the present invention is not particularly limited as long as it can cause hydrocarbons to be strongly bonded to the surface of the oxide microcrystalline particles, and examples thereof include ether bonds, ester bonds, and N atoms. Various organic substances that can form a strong bond such as a bond, a bond through an S atom, a bond of metal-C-, a bond of metal-C =, a bond of metal- (C = O)-, and the like. . As the hydrocarbon to be bonded, the number of carbon atoms is not particularly limited, and those having 1 or 2 carbon atoms can be used, but long-chain hydrocarbons having a chain having 3 or more carbon atoms are preferable. Examples thereof include 3 to 20 linear or branched chain or cyclic hydrocarbons. Moreover, such hydrocarbons may be substituted or unsubstituted.

Such organic material, the carboxylic acid having 6 to 10 carbon atoms is used from the viewpoint of the ratio of the oxide fine crystal grains say you improved with active crystal faces in live powder made, hexane Acid and decanoic acid are particularly preferred.

  In the production method of the present invention, the cation hydroxide and the organic substance are allowed to coexist in the reaction field described above to produce oxide microcrystalline particles. The mixing amount of the cation hydroxide and the organic substance is not particularly limited, but the ratio (molar ratio) between the cation hydroxide and the organic substance is 5: 1 to 1:10. Is preferable, and 1: 1 to 1: 5 is more preferable. If the ratio of the organic substance to the cation hydroxide is less than the above lower limit, the surface modification action of the organic substance is insufficient, and the form of crystals formed tends to be irregular and coarse. The yield of the resulting crystals is low and the size of the crystals tends to be too small. The concentration of the cation hydroxide in the reaction solution is not particularly limited, but is preferably 0.01 to 1.0 mol / l, and preferably 0.1 to 0.2 mol / l. Is more preferable. Furthermore, the reaction time is not particularly limited, but generally a reaction time of about 0.01 to 20 minutes is employed.

  In the production method of the present invention, the oxide microcrystal particles produced by the above reaction are usually cooled to about room temperature, separated by centrifugation, membrane filter, etc., and washed with water, ethanol, etc. as necessary. Thus, the powder of the present invention is obtained.

  Next, the catalyst of the present invention will be described. The catalyst of the present invention comprises a powder comprising the oxide microcrystal particles of the present invention, and a catalytically active species supported on the surface of the powder.

  The catalytically active species according to the present invention is not particularly limited as long as it is a substance that contributes to the target catalytic activity, and includes at least one element selected from the group consisting of oxides of transition elements and noble metals. . Examples of such noble metals include Pt, Pd, Rh, Ru, Ir, Os, Au, Ag, and the like. Among them, platinum group elements (Pt, Pd, Rh, Ru, Ir, Os) are preferable from the viewpoint of catalytic activity. Pt is preferable and Pt is particularly preferable. The oxide of the transition element may be any oxide that is different from the oxide that constitutes the oxide microcrystal particles to be supported. Fe, Cu, Co, Ni, Zr, Ti, Zn, V , W, Mo, Cr, Nb, Sn, Mn, Sm, Eu, Tb, Yb, and the like. Among them, iron oxide and copper oxide are preferable from the viewpoint of catalytic activity, and iron oxide is particularly preferable. The transition element oxide may be a single metal oxide or a complex metal oxide composed of a plurality of metal oxides.

  The amount of the catalytically active species supported on the powder in the catalyst of the present invention is not particularly limited, but the amount of the catalytically active species is about 0.1 to 10 parts by mass with respect to 100 parts by mass of the supported powder. Preferably there is.

  Further, a specific method for supporting the catalytically active species on the powder is not particularly limited. For example, when supporting a noble metal, a solution containing a noble metal salt (nitrate, chloride, acetate, etc.) or a complex. A method in which the powder is brought into contact with the substrate and further subjected to a reduction treatment and / or a firing treatment as necessary is appropriately employed. In the case of supporting an oxide of a transition element, the powder is brought into contact with a solution containing a transition element salt (nitrate, chloride, acetate, etc.) or a complex, and if necessary, oxidation treatment and / or Or the method of giving a baking process is employ | adopted suitably.

  The catalyst of the present invention may be used in the form of powder or formed into a predetermined shape such as pellets, but may be used by being supported on a catalyst substrate. Such a substrate is not particularly limited and is appropriately selected according to the application of the catalyst, etc., but when used as an exhaust gas purification catalyst or the like, a monolith carrier substrate (honeycomb filter, high density honeycomb, etc.), foam filter A substrate, a pellet-shaped substrate, a plate-shaped substrate and the like are preferably employed. In addition, the material of such a base material is not particularly limited, but when used as an exhaust gas purification catalyst, a base material made of ceramics such as cordierite, silicon carbide, mullite, or a metal such as stainless steel containing chromium and aluminum. The base material which consists of is employ | adopted suitably.

  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
A closed reaction vessel (tubular autoclave) with an internal volume of 5 cm ³ was charged with 4.4 ml of 0.03 mol / l cerium hydroxide suspension and 0.1 ml of hexanoic acid, and reacted in a heating furnace set at 200 ° C. The container was placed and heated. It took 1.5 minutes to raise the temperature. After reacting for 20 minutes, the mixture was cooled to room temperature, and the resulting powder was centrifuged and washed with water and ethanol.

Observation of the morphology of the fine particles constituting the powder produced using HR-TEM (high resolution transmission electron microscope) revealed a pseudo cubic particle (average particle size: 7 nm) shown in FIG. 1 and a flat plate shape shown in FIG. There are circular small particles (average particle size: 6 nm), tabular elongated particles (average length: 10 nm) shown in FIG. 3, and tabular large circular particles (average particle size: 10 nm) shown in FIG. Had the average particle size or average length shown in parentheses. When EDX analysis was performed on these crystals, all were ceria (CeO ₂ ) crystals, and at least pseudo-cubic particles were confirmed to be monodisperse nanocrystals composed of single crystals.

  When these crystals were analyzed from the lattice plane of the lattice image photograph and the angle thereof, in the case of small circular particles, large circular particles, and long and narrow particles, the (111) plane with an interplanar spacing of d = 3.1 mm was about 70 °. It was confirmed that it consists of (110) planes. Further, it was found that the thickness was very thin compared to the width from the ease of transmission of electron beams, and it was confirmed that the particles were flat. On the other hand, since the (200) plane and the (020) plane intersect at right angles, the pseudo cubic particle was confirmed to be a cubic particle composed of the (001) plane and an equivalent plane.

  When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about 70%. In addition, although it is estimated that the pseudo cubic particles have a mass per particle that is clearly larger than those of other shaped particles, it is assumed that even if the same mass is assumed, pseudo cubic particles are obtained for 70% by mass or more. I understood. Therefore, it was confirmed that the ceria microcrystal particles having an active crystal face composed of an oxygen ion layer on the outermost surface accounted for 50% by mass or more and could not be obtained conventionally.

(Example 2)
A powder was obtained in the same manner as in Example 1 except that the temperature of the heating furnace was set to 400 ° C., the amount of the cerium hydroxide suspension was 2.5 ml, and the amount of hexanoic acid was 0.057 ml.

  The form of fine particles constituting the produced powder was observed by HR-TEM and EDX analysis in the same manner as in Example 1. As shown in FIGS. 5 to 6, pseudo cubic particles (average particle size: 6 nm), flat plate shape There are small circular particles (average particle size: 4 nm) and tabular large circular particles (average particle size: 10 nm), both of which are ceria crystals, and at least pseudo-cubic particles are monodisperse nanocrystals composed of single crystals. It was confirmed that.

  When these crystals were analyzed from the lattice plane of the lattice image photograph and the angle thereof, as in the case of Example 1, circular small particles and circular large particles are tabular grains having (110) planes. Thus, it was confirmed that the pseudo cubic particle is a cubic particle having a (001) plane and a plane equivalent thereto.

  When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It is 80% by mass, and it is confirmed that it is a powder that could not be obtained in the past, with ceria microcrystalline particles comprising active crystal planes composed of an oxygen ion layer on the outermost surface accounting for 50% by mass or more. It was done.

(Comparative Example 1)
A sealed reaction vessel having an internal volume of 5 cm ³ was charged with 2.5 ml of a 0.1 mol / l cerium nitrate aqueous solution and 0.01 ml of decanoic acid, and the reaction vessel was placed in a heating furnace set at 350 ° C. and heated. It took 1.5 minutes for the temperature to rise, and after reacting for 20 minutes, the mixture was cooled to room temperature. The obtained powder was separated by a membrane filter and washed with water and ethanol.

  The shape of the fine particles constituting the produced powder was observed by HR-TEM and EDX analysis in the same manner as in Example 1. As shown in FIGS. 7 to 8, flat circular small particles having an average particle diameter of about 10 nm were obtained. It was confirmed that all were ceria crystals.

  When these crystals were analyzed from the lattice plane of the lattice image photograph and the angle thereof, the (111) plane with a plane interval of d = 3.1 mm intersected at about 70 °, and thus this was confirmed in Example 1. It was confirmed to be the same as the flat circular small particles having a (110) plane.

  As a result of confirming the crystal planes of arbitrary 500 fine particles in the powder obtained in this comparative example, almost all the particles are flat circular small particles composed of (110) planes, (001) plane and the same It was confirmed that ceria microcrystal particles, which are pseudo-cubic particles composed of equivalent surfaces, do not exist.

(Comparative Example 2)
A sealed reaction vessel having an internal volume of 5 cm ³ was charged with 2.5 ml of a 0.1 mol / l cerium nitrate aqueous solution and 0.01 ml of decylamine, and the reaction vessel was placed in a heating furnace set at 350 ° C. and heated. It took 1.5 minutes for the temperature to rise, and after reacting for 20 minutes, the mixture was cooled to room temperature. The obtained powder was separated by a membrane filter and washed with water and ethanol.

  When the form of the fine particles constituting the generated powder was observed by HR-TEM and EDX analysis in the same manner as in Example 1, as shown in FIG. 9, there were particles having a particle size of about 30 to 150 nm. Were also confirmed to be ceria crystals.

  When these crystals were analyzed from the lattice plane of the lattice image photograph and their angles, they were composed of (001) plane as shown in FIG. 10, (110) plane as shown in FIG. 11, and (211) plane. The presence of particles was confirmed.

  When the crystal planes of arbitrary 500 fine particles in the powder obtained in this comparative example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed to be 10% by mass.

(Comparative Example 3)
A sealed reaction vessel having an internal volume of 5 cm ³ was charged with 2.5 ml of a 0.1 mol / l cerium nitrate aqueous solution, and the reaction vessel was placed in a heating furnace set at 350 ° C. and heated. It took 1.5 minutes for the temperature to rise, and after reacting for 20 minutes, the mixture was cooled to room temperature. The obtained powder was separated by a membrane filter and washed with water and ethanol.

  The form of the fine particles constituting the produced powder was observed by HR-TEM and EDX analysis in the same manner as in Example 1. As a result, there were large particles with an average particle diameter of 1 μm or more, both of which were ceria crystals. It was confirmed that there was.

  When these crystals were analyzed from the lattice plane of the lattice image photograph and its angle, the (013) plane as shown in FIGS. 12 to 13, the (011) plane as shown in FIGS. 14 to 15, and FIG. It was confirmed that particles having (211) plane as shown in FIG. 17 and (123) plane and (211) plane as shown in FIGS.

  As a result of confirming the crystal plane of any 100 fine particles in the powder obtained in this comparative example, the particles synthesized in the absence of the organic substance have no selectivity to the crystal plane, and the (001) plane and It was confirmed that the ratio of ceria microcrystalline particles, which are pseudo-cubic particles having an equivalent surface, was about 10% by mass.

<Catalytic activity test>
2 g of the powder obtained in Example 2 was applied to a cordierite honeycomb test piece (30 mmφ × 30 mm), and 0.002 g of Pt was further supported thereon. Then, a flow-type reaction was performed using the obtained catalyst. The model exhaust gas was circulated while slowly raising the temperature in the vessel.

For comparison, a similar test was performed using a catalyst obtained by applying commercially available CeO ₂ powder (specific surface area 100 m ² / g) to a cordierite honeycomb test piece together with Pt.

  The 50% purification temperature obtained as a result of both tests is shown below.

(Powder obtained in Example 2) (Commercially available CeO ₂ powder)
CO 80 ℃ 150 ℃
C ₃ H ₆ 120 ° C. 210 ° C.
NO 135 ° C 220 ° C.

  From the above results, the catalyst obtained by using the powder obtained in Example 2 has high catalytic activity at a low temperature around room temperature, and the catalytic properties do not decrease until a high temperature around 800 ° C. It was confirmed that it was obtained. Therefore, if the catalyst of the present invention is used as an exhaust gas purification catalyst, it can be purified with high efficiency without releasing hydrocarbons and CO released at engine start-up, and a dramatic reduction of exhaust gas can be easily achieved. It becomes possible to do.

(Example 3)
A sealed reaction vessel (tubular autoclave) with an internal volume of 5 cm ³ was charged with 2.5 ml of 0.2 mol / l cerium hydroxide suspension and 0.2 ml of hexanoic acid, and reacted in a heating furnace set at 400 ° C. The container was placed and heated. It took 1.5 minutes for the temperature to rise, and after reacting for 20 minutes, the mixture was cooled to room temperature. The obtained powder was separated by a membrane filter and washed with water and ethanol.

  When TEM observation and EDX analysis were performed on the form of the fine particles constituting the generated powder, as shown in FIGS. 21 to 22, there were particles such as pseudo cubic particles having an average particle diameter of about 10 nm. It was confirmed that it is a ceria crystal, and at least pseudo-cubic particles are monodisperse nanocrystals composed of a single crystal.

  When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, as shown in FIG. 23, ceria, which is a pseudo-cubic particle comprising a (001) plane and an equivalent plane, as shown in FIG. It was confirmed that the ratio of microcrystalline particles was about 70% by mass. FIG. 23 shows the measurement results of the crystal planes of 39 fine particles shown in FIG.

Example 4
A powder was obtained in the same manner as in Example 3 except that the amount of hexanoic acid charged was 0.1 ml.

  When TEM observation and EDX analysis were performed on the form of the fine particles constituting the generated powder, as shown in FIG. 24, particles such as pseudo cubic particles having an average particle diameter of about 10 nm were present, both of which were ceria crystals. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.

  When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed to be 60% by mass.

(Example 5)
A powder was obtained in the same manner as in Example 3 except that the amount of hexanoic acid charged was 0.3 ml.

  When TEM observation and EDX analysis were performed on the form of fine particles constituting the generated powder, as shown in FIG. 25, particles such as pseudo cubic particles having an average particle diameter of about 10 nm were present, both of which were ceria crystals. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.

  When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed to be 50% by mass.

(Example 6)
In a sealed reaction vessel (tubular autoclave) with an internal volume of 5 cm ³ , a lanthanum-containing cerium hydroxide suspension of 0.2 mol / l (La content: 10 mol% based on the total amount of Ce and La) 2.5 ml and 0.1 ml of hexanoic acid were charged, and the reaction vessel was placed in a heating furnace set at 400 ° C. and heated. It took 1.5 minutes for the temperature to rise, and after reacting for 20 minutes, the mixture was cooled to room temperature. The obtained powder was separated by a membrane filter and washed with water and ethanol.

  TEM observation and EDX analysis of the form of the fine particles constituting the generated powder revealed that there were particles such as pseudo cubic particles having an average particle diameter of about 10 nm as shown in FIG. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.

  When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed to be 50% by mass.

(Example 7)
A powder was obtained in the same manner as in Example 6 except that the amount of hexanoic acid charged was 0.2 ml.

  As a result of TEM observation and EDX analysis of the form of fine particles constituting the generated powder, as shown in FIG. 27, particles such as pseudo cubic particles having an average particle diameter of about 10 nm are present, both of which are ceria crystals. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.

  When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed that the content was 70% by mass.

(Example 8)
A powder was obtained in the same manner as in Example 6 except that the amount of hexanoic acid charged was 0.3 ml.

  When TEM observation and EDX analysis were performed on the form of fine particles constituting the generated powder, as shown in FIG. 28, particles such as pseudo cubic particles having an average particle diameter of about 10 nm were present, both of which were ceria crystals. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.

  When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed that the content was 70% by mass.

Example 9
A powder was obtained in the same manner as in Example 6 except that the amount of hexanoic acid charged was 0.4 ml.

  As a result of TEM observation and EDX analysis of the form of fine particles constituting the generated powder, as shown in FIG. 29, particles such as pseudo cubic particles having an average particle diameter of about 10 nm are present, both of which are ceria crystals. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.

  When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed that it was 80 mass%.

(Example 10)
A powder was obtained in the same manner as in Example 6 except that the amount of hexanoic acid charged was 0.6 ml.

  As a result of TEM observation and EDX analysis of the form of fine particles constituting the generated powder, as shown in FIG. 30, there are particles such as pseudo cubic particles having an average particle diameter of about 10 nm, both of which are ceria crystals. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.

  When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed to be 90% by mass.

(Example 11)
A powder was obtained in the same manner as in Example 10 except that the charged amount of the lanthanum-containing cerium hydroxide suspension was changed to 1.9 ml.

  As a result of TEM observation and EDX analysis of the form of fine particles constituting the generated powder, as shown in FIG. 31, there are particles such as pseudo cubic particles having an average particle diameter of about 10 nm, both of which are ceria crystals. It was confirmed that at least the pseudo cubic particles are monodisperse nanocrystals composed of a single crystal.

  When the crystal planes of arbitrary 500 fine particles in the powder obtained in this example were confirmed, the ratio of ceria microcrystal particles, which are pseudo-cubic particles composed of (001) planes and planes equivalent thereto, was about It was confirmed to be 50% by mass.

(Comparative Example 4)
After neutralizing 50 ml of 0.2 mol / l cerium nitrate aqueous solution with 1 mol / l ammonia water and stirring for 30 minutes, the resulting precipitate was separated, dried at 150 ° C. for 5 hours, and further 400 Ceria powder was obtained by baking at 5 ° C. for 5 hours.

  When the crystal face of any 500 fine particles in the powder obtained in this comparative example was confirmed, the particles synthesized by the precipitation method had no selectivity for the crystal face, and particles with a clear crystal face were not seen. I couldn't.

<Oxygen storage amount test>
The oxygen storage amount (OSC) of the powder composed of ceria microcrystal particles obtained in Example 3 and Comparative Example 4 was measured and compared by the following method.

  That is, each sample was placed in a sample cell of a 15 mg thermogravimetric analyzer, and reversible weight change was measured by repeatedly performing reduction with hydrogen and oxidation with oxygen at each test temperature of 150 ° C., 200 ° C., and 400 ° C. A zirconia powder having no OSC was used as a blank, and the OSC of each sample was determined by subtracting the value obtained with zirconia from the measured value of each sample. The obtained result is shown in FIG.

  As is apparent from the results shown in FIG. 32, it was obtained in Example 3 as compared with the powder composed of ceria microcrystalline particles obtained in Comparative Example 4 at each test temperature of 150 ° C., 200 ° C., and 400 ° C. It was confirmed that the powder composed of the ceria microcrystal particles thus obtained has an overwhelmingly large OSC.

<Heat resistance test>
The powders composed of ceria microcrystalline particles obtained in Example 3 and Example 9 were each heated in the atmosphere at 400 ° C. for 5 hours, and the morphology of the subsequent fine particles was observed by TEM. The obtained results are shown in FIG. 33 (Example 3) and FIG. 34 (Example 9).

  As is clear from the results shown in FIG. 33 and FIG. 34, the powder composed of ceria microcrystalline particles obtained in Example 3 is also excellent in heat resistance, but as the second component obtained in Example 9, It was confirmed that the powder composed of ceria microcrystalline particles containing lanthanum is more excellent in heat resistance.

  As described above, according to the method for producing a powder composed of oxide microcrystal particles of the present invention, the ratio of the oxide microcrystal particles composed of active crystal faces can be significantly improved as compared with the conventional method. . Therefore, according to the present invention, it is possible to provide a powder of oxide microcrystal particles in which the oxide crystallite particles composed of active crystal faces that could not be obtained conventionally account for 50% by mass or more, The catalyst of the present invention obtained by using the powder comprising the oxide microcrystal particles of the present invention is excellent in low temperature and high temperature catalytic activity. Therefore, the present invention is very useful as a technique for obtaining various catalysts such as an exhaust gas purification catalyst and an oxidation catalyst.

4 is an electron micrograph showing the analysis result of the crystal plane of the oxide microcrystal particles obtained in Example 1. FIG. 4 is an electron micrograph showing the analysis result of the crystal plane of the oxide microcrystal particles obtained in Example 1. FIG. 4 is an electron micrograph showing the analysis result of the crystal plane of the oxide microcrystal particles obtained in Example 1. FIG. 4 is an electron micrograph showing the analysis result of the crystal plane of the oxide microcrystal particles obtained in Example 1. FIG. 4 is an electron micrograph showing the analysis result of the crystal plane of the oxide microcrystal particles obtained in Example 2. FIG. 4 is an electron micrograph showing the analysis result of the crystal plane of the oxide microcrystal particles obtained in Example 2. FIG. 2 is an electron micrograph showing the shape of oxide microcrystal particles obtained in Comparative Example 1. FIG. 4 is an electron micrograph showing the analysis result of the crystal plane of the oxide microcrystal particles obtained in Comparative Example 1. FIG. 4 is an electron micrograph of oxide microcrystal particles obtained in Comparative Example 2. FIG. 2 is a photograph showing an electron diffraction image of oxide microcrystal particles obtained in Comparative Example 2. FIG. 2 is a photograph showing an electron diffraction image of oxide microcrystal particles obtained in Comparative Example 2. FIG. 4 is an electron micrograph of oxide crystallite particles obtained in Comparative Example 3. 4 is a photograph showing an electron diffraction pattern of oxide microcrystal particles obtained in Comparative Example 3. FIG. 4 is an electron micrograph of oxide crystallite particles obtained in Comparative Example 3. 4 is a photograph showing an electron diffraction pattern of oxide microcrystal particles obtained in Comparative Example 3. FIG. 4 is an electron micrograph of oxide crystallite particles obtained in Comparative Example 3. 4 is a photograph showing an electron diffraction pattern of oxide microcrystal particles obtained in Comparative Example 3. FIG. 4 is an electron micrograph of oxide crystallite particles obtained in Comparative Example 3. 4 is a photograph showing an electron diffraction pattern of oxide microcrystal particles obtained in Comparative Example 3. FIG. 4 is a photograph showing an electron diffraction pattern of oxide microcrystal particles obtained in Comparative Example 3. FIG. 4 is an electron micrograph of oxide microcrystal particles obtained in Example 3. FIG. 4 is an electron micrograph of oxide microcrystal particles obtained in Example 3. FIG. 4 is an electron micrograph showing the analysis result of the crystal plane of the oxide microcrystal particles obtained in Example 3. FIG. 4 is an electron micrograph of oxide microcrystal particles obtained in Example 4. FIG. 6 is an electron micrograph of oxide microcrystal particles obtained in Example 5. FIG. 4 is an electron micrograph of oxide microcrystal particles obtained in Example 6. FIG. 4 is an electron micrograph of oxide microcrystal particles obtained in Example 7. FIG. 4 is an electron micrograph of oxide microcrystal particles obtained in Example 8. FIG. 4 is an electron micrograph of oxide microcrystal particles obtained in Example 9. 4 is an electron micrograph of oxide microcrystal particles obtained in Example 10. FIG. 2 is an electron micrograph of oxide microcrystal particles obtained in Example 11. FIG. It is a graph which shows the oxygen storage amount of the powder which consists of oxide microcrystal particle | grains obtained in Example 3 and Comparative Example 4. 2 is an electron micrograph after a heat resistance test of oxide microcrystal particles obtained in Example 3. FIG. 4 is an electron micrograph of a heat resistance test of oxide microcrystal particles obtained in Example 9.

Claims (11)

In the reaction field in the high-temperature and high-pressure hydrothermal synthesis method, in the coexistence of a carboxylic acid having 6 to 10 carbon atoms from a hydroxide of Ce or a hydroxide of Ce and La which is a cation constituting the oxide microcrystal particles. in a powder consisting of synthesized oxide fine crystal grains formed by, characterized in that oxide fine crystal grains consisting of crystal plane of the outermost surface is formed by oxygen ion layer accounts for more than 50 wt% A powder composed of oxide microcrystalline particles. Powder of oxide crystallites particles according to claim 1, wherein the coordination number of the cation is 2 or less for oxygen ions of the outermost surface constituting the front Kiyui planes. Oxide fine crystal grains consisting of front Kiyui crystal faces have a fluorite structure, before Kiyui planes is (001) plane and the (001) plane crystallographically equivalent crystal planes A powder comprising fine oxide crystal particles according to claim 1 or 2 . The content of La is comprised of oxide fine grains according to any one of claims 1 to 3, characterized in that 3 to 20 mol% based on the total amount of Ce and La powder. Oxide according to any one of claims 1-4 for oxide fine crystal grains consisting of front Kiyui planes is characterized in that having an average particle size in the range of 2nm~30nm Powder composed of microcrystalline particles. Powder of oxide crystallites particles according to any one of claims 1 to 5 in which oxide fine crystal grains consisting of front Kiyui planes is characterized in that it is a monodispersed nanocrystalline particles. Claim 1 and a powder of an oxide fine grains according to any one of the six, a catalyst which is characterized by comprising said powder catalytically active species supported on the surface of the. The catalyst according to claim 7 , wherein the catalytically active species is at least one selected from the group consisting of oxides of transition elements and noble metals. In the reaction field in the high-temperature and high-pressure hydrothermal synthesis method, in the coexistence of a carboxylic acid having 6 to 10 carbon atoms from a hydroxide of Ce or a hydroxide of Ce and La which is a cation constituting the oxide microcrystal particles. By synthesizing the oxide microcrystal particles with the above, a powder made of oxide microcrystal particles in which the outermost surface comprises oxide crystallite particles comprising a crystal plane composed of an oxygen ion layer account for 50% by mass or more. A method for producing a powder comprising oxide microcrystalline particles. The method for producing a powder comprising fine oxide crystal particles according to claim 9 , wherein the La content is 3 to 20 mol% based on the total amount of Ce and La . The powder comprising the oxide microcrystal particles according to claim 9 or 10 , wherein a ratio (molar ratio) between the cation hydroxide and the carboxylic acid is 5: 1 to 1:10. Manufacturing method.