JP2011144421A - Precious-metal-based colloidal solution and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a precious-metal-based colloidal solution that has precious-metal-based fine particles uniformly dispersed therein which have a small particle size and are uniform, and is superior in storability, and to provide a method for producing the same. <P>SOLUTION: The precious-metal-based colloidal solution includes at least one precious-metal-based fine particle selected from the group consisting of a precious-metal fine particle, a precious-metal-alloy fine particle, a precious-metal-compound fine particle and a precious-metal-alloyed compound fine particle, and a polymeric dispersing agent. As for a particle size of the precious-metal-based fine particles, a particle size D<SB>50</SB>at which the accumulated mass in the particle size distribution reaches 50% is 0.8-5.0 nm, and a particle size D<SB>90</SB>at which the accumulated mass reaches 90% is 2.5 times of the particle size D<SB>50</SB>or smaller. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a noble metal colloid solution and a method for producing the same.

  Noble metal fine particles such as noble metal fine particles and noble metal alloy fine particles are usually carried on a carrier and used for various applications such as a catalyst. Such noble metal-based fine particles are conventionally obtained by mixing a noble metal complex, which is a raw material of noble metal-based fine particles, with a carrier that is an aggregated powder of several microns composed of an oxide or a composite oxide, or an oxide or a composite. After impregnating a noble metal complex with a carrier, which is an agglomerated powder of several microns composed of an oxide, particles were formed and supported on the carrier. However, in this method, the noble metal complex is adsorbed in the vicinity of the surface of the support formed by agglomeration of the primary particles, so that the formed noble metal fine particles are also arranged close to each other and the dispersibility becomes low. There was a problem that noble metal-based fine particles were likely to grow and the catalytic activity was lowered.

  In addition, as a method for supporting noble metal-based fine particles on a carrier, a method of adsorbing a colloidal solution containing noble metal-based fine particles on the carrier is disclosed. According to this method, since the colloidal solution containing the noble metal-based fine particles is supported on the support formed by agglomeration of the primary particles by heating with stirring, it is difficult to support the colloid solution sufficiently uniformly. On the other hand, a colloid solution containing a highly dispersible oxide or composite oxide in which an appropriate polymer dispersant is adsorbed and a colloid solution containing noble metal fine particles are uniformly mixed, and then the pH is adjusted to adjust the polymer. The noble metal fine particles can be supported on the carrier by a method of fixing the noble metal fine particles arranged uniformly by removing the dispersant. However, nanoparticles such as noble metal-based fine particles tend to aggregate in a solvent such as water, and it has not been easy to obtain a colloid solution in which noble metal-based fine particles are highly dispersed.

  For example, Japanese Patent Application Laid-Open No. 2004-261735 (Patent Document 1) discloses a noble metal colloid solution comprising a solvent such as water, cluster particles of noble metal, and a polymer dispersant such as polyethyleneimine. Although this noble metal colloid solution has good water solubility and does not cause rapid precipitation during use, the noble metal fine particles in the colloid solution are aggregated in the liquid. The monodispersibility was low.

  Japanese Patent Application Laid-Open No. 2006-183092 (Patent Document 2) discloses a reaction system in a liquid phase containing two or more kinds of metal ions in the presence of a polymer dispersant having a carboxyl group and a molecular weight of 4000 to 30000. Among them, a method is disclosed in which alloy fine particles are precipitated by being reduced by the action of a reducing agent. According to this method, alloy fine particles and a metal colloid solution containing the same can be efficiently obtained. However, even in the metal colloid solution obtained by this method, although the dispersibility of the noble metal fine particles in the liquid is improved as compared with the noble metal colloid solution described in Patent Document 1, it is still not sufficient.

  Furthermore, in JP 2009-144250 A (Patent Document 3), a thin film fluid is formed between processing surfaces which are disposed so as to be able to approach and separate from each other and at least one of which rotates relative to the other. Obtained by mixing the aqueous solution containing the polymer dispersant and the metal compound with the reducing agent aqueous solution in the above thin film and carrying out the reduction reaction while uniformly mixing in the thin film. Disclosed are metal fine particles and metal colloids containing the same. According to this method, a metal colloid solution containing metal fine particles having a uniform particle diameter can be obtained. However, even in this metal colloid solution, the metal fine particles are aggregated in the liquid, and the dispersibility thereof is not sufficient.

  As described above, in the conventional colloidal solution, the dispersibility of the noble metal fine particles in the liquid is not yet sufficient, and even when the noble metal colloidal solution is supported on the noble metal fine particle carrier, the noble metal-based fine particles are highly advanced. It was difficult to obtain a dispersed catalyst or the like.

  Japanese Patent Application Laid-Open No. 2005-133135 (Patent Document 4) discloses a method in which a reaction liquid is instantaneously mixed and a reaction is allowed to proceed in a pipe to form metal fine particles. It is disclosed that this is a method suitable for forming metal fine particles by a reverse micelle method using a surfactant. And in the said patent document 4, the high-speed stirring mixing system, the fine gap mixing system, and the high pressure mixing system are disclosed as a mixing method. However, in the mixing device used for the high-speed stirring and mixing method, the reaction liquid is mixed after being dropped into the reaction field, and is not directly introduced into the reaction field to which high shear force is applied and mixed. . In the mixing device used for the micro gap mixing method, the reaction liquid is supplied and mixed while applying a shearing force in a narrow reaction field, but the reaction liquid supply port is separated and instantaneous In terms of mixing, it was not sufficient. Furthermore, in Patent Document 4, Y-shaped and T-shaped mixing devices used for the high pressure mixing method are disclosed, but in these devices, the reaction liquid is collided in the pipe and mixed. Yes, it does not consider shear force. For this reason, it has been difficult for the method described in Patent Document 4 to obtain a noble metal colloid solution in which uniform noble metal fine particles having a small particle diameter are uniformly dispersed.

JP 2004-261735 A JP 2006-183092 A JP 2009-144250 A JP-A-2005-133135

  The present invention has been made in view of the above-mentioned problems of the prior art, and provides a noble metal colloid solution having excellent storage stability, in which uniform noble metal fine particles having a small particle diameter are uniformly dispersed, and a method for producing the same. The purpose is to provide.

  As a result of intensive studies to achieve the above object, the present inventors have obtained two or more kinds of raw material solutions containing noble metal ions, which are raw materials of noble metal-based fine particles, and a polymer dispersant, at a predetermined high shear rate. It is introduced directly into the region where it is mixed and homogeneously mixed. Further, by precipitating the noble metal fine particles and adsorbing the polymer dispersant to the single noble metal fine particles, uniform noble metal fine particles with a small particle diameter can be obtained. The inventors have found that a colloidal solution that is uniformly dispersed can be obtained, and have completed the present invention.

That is, the noble metal colloid solution of the present invention contains at least one kind of noble metal fine particles selected from the group consisting of noble metal fine particles, noble metal alloy fine particles, noble metal compound fine particles and noble metal alloy compound fine particles, and a polymer dispersant. the noble metal particles, the particle diameter _{D 90} of and cumulative mass is a particle diameter _{D 50} which cumulative mass in the particle size distribution is 50% 0.8~5.0nm is 90% of the particle diameter _{D 50} It is characterized by being 2.5 times or less. As such a noble metal colloid solution, one produced by the following method for producing a noble metal colloid solution of the present invention is preferable.

That is, the method for producing a noble metal-based colloidal solution of the present invention comprises at least one selected from the group consisting of noble metal fine particles, noble metal alloy fine particles, noble metal compound fine particles and noble metal alloy compound fine particles by mixing two or more raw material solutions. A noble metal-based colloidal solution containing noble metal-based fine particles, wherein at least one of the two or more kinds of raw material solutions contains a noble metal ion that is a raw material of the noble metal-based fine particles, At least one of the two or more types of raw material solutions contains a polymer dispersant, and each of the raw material solutions is introduced directly and homogeneously into a region having a shear rate of 3000 sec ⁻¹ or more. It is a method characterized by mixing.

  In such a method for producing a noble metal-based colloid solution, at least one of the two or more kinds of raw material solutions contains the noble metal ion, and at least one of the remaining raw material solutions contains the high-value colloid solution. It is preferable that it contains a molecular dispersant, and it is more preferable that the raw material solution containing the polymer dispersant further contains a reducing agent. The cation concentration of the raw material solution containing the noble metal ions is preferably 0.0001 to 0.5 mol / L.

  In the noble metal colloid solution and the method for producing the same of the present invention, the weight average molecular weight of the polymer dispersant is preferably 800 to 4000. The polymer dispersant is preferably a (meth) acrylic acid polymer, and the pH of the noble metal colloid solution in this case is more preferably adjusted to 5.0 to 10.0.

  The reason why a colloidal solution in which uniform noble metal-based fine particles having a small particle size are uniformly dispersed is obtained by the present invention is not necessarily clear, but the present inventors speculate as follows. That is, nanoparticles such as noble metal-based fine particles are likely to aggregate in an aqueous solution such as water, and usually a polymer dispersant is added and adsorbed to the nanoparticles to suppress aggregation. It is surmised that the polymer dispersant used in the present invention is also adsorbed to the nanoparticles and suppresses aggregation, but an aggregate having a large particle diameter is formed only by adding the polymer dispersant and performing normal stirring. Tend to form. This is because the polymer dispersant is usually larger than the primary particles and tends to form a crosslinked structure, so that the nanoparticles adsorbed by the polymer dispersant agglomerate with the crosslinking reaction of the polymer dispersant, This is presumably because the polymer dispersant is simultaneously adsorbed on a plurality of noble metal-based fine particles.

  Further, when diethanolamine and polyethylene glycol are added, aggregates having a large particle size tend to be formed. This is because even when only polyethylene glycol is added, aggregates are formed in the liquid. However, when diethanolamine and polyethylene glycol are added, diethanolamine added to form noble metal-based fine particles is adsorbed to the generated noble metal-based fine particles. Since it inhibits the adsorption of polyethylene glycol, the effect of suppressing the aggregation by polyethylene glycol is further inferior, and even if diethanolamine is adsorbed to noble metal fine particles, sufficient steric hindrance is not exerted in the liquid, and the suppression of aggregation by diethanolamine It is presumed that the effect is not fully exhibited. In addition, the repulsive effect of polyethylene glycol is small and the amount of adsorption is small, so the repulsive effect is small, and the aggregates further agglomerate during storage of the noble metal-based colloid solution and the dispersibility in the liquid decreases. It is guessed.

  On the other hand, in the production method of the present invention, since a high shear force is imparted to the reaction field in addition to the addition of the polymer dispersant, the polymer dispersant is converted into the noble metal particles at the same time as the noble metal particles are precipitated. It is presumed that the noble metal-based fine particles are adsorbed and exist in the colloidal solution in a uniformly dispersed state. In addition, since the polymer dispersant is stably present in the colloidal solution, it is presumed that the noble metal-based fine particles hardly aggregate and are stably dispersed in the colloidal solution.

  According to the present invention, it is possible to obtain a noble metal colloid solution having excellent storage stability in which uniform noble metal fine particles having a small particle diameter are uniformly dispersed.

It is a schematic longitudinal cross-sectional view which shows suitable one Embodiment of the manufacturing apparatus of the noble metal type colloid solution used for this invention. FIG. 2 is an enlarged longitudinal sectional view showing a tip portion (stirring portion) of the homogenizer 10 shown in FIG. 1. It is a side view of the inner side stator 13 shown in FIG. It is a cross-sectional view of the inner stator 13 shown in FIG. 2 is a high-resolution scanning transmission electron microscope photograph (high-resolution STEM photograph) showing a high-angle scattering dark field image (HAADF image) of the noble metal-based fine particles obtained in Example 1. FIG. 2 is a transmission electron micrograph (TEM photograph) showing an electron diffraction pattern of noble metal-based fine particles obtained in Example 1. FIG. 4 is a high-resolution scanning transmission electron microscope photograph (high-resolution STEM photograph) showing a high-angle scattering dark field image (HAADF image) of the noble metal-based fine particles obtained in Example 2. FIG. 3 is a transmission electron micrograph (TEM photograph) showing an electron diffraction pattern of noble metal-based fine particles obtained in Example 2. FIG. 6 is a high-resolution scanning transmission electron microscope photograph (high-resolution STEM photograph) showing a high-angle scattering dark field image (HAADF image) of the noble metal-based fine particles obtained in Example 3. FIG. 6 is a transmission electron micrograph (TEM photograph) showing an electron diffraction pattern of noble metal-based fine particles obtained in Example 3. FIG. 6 is a high-resolution scanning transmission electron micrograph (high-resolution STEM photograph) showing a high-angle scattering dark field image (HAADF image) of the noble metal-based fine particles obtained in Example 4. 6 is a transmission electron micrograph (TEM photograph) showing an electron diffraction pattern of noble metal-based fine particles obtained in Example 4. FIG. 6 is a high-resolution scanning transmission electron microscope photograph (high-resolution STEM photograph) showing a high-angle scattering dark field image (HAADF image) of the noble metal-based fine particles obtained in Example 5. FIG. 6 is a transmission electron micrograph (TEM photograph) showing an electron diffraction pattern of noble metal-based fine particles obtained in Example 5. FIG.

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

First, the noble metal colloid solution of the present invention will be described. The noble metal colloid solution of the present invention contains at least one kind of noble metal fine particles selected from the group consisting of noble metal fine particles, noble metal alloy fine particles, noble metal compound fine particles and noble metal alloy compound fine particles, and a polymer dispersant, 2 noble metal particles, the particle diameter _{D 90} of and cumulative mass is a particle diameter _{D 50} which cumulative mass in the particle size distribution is 50% 0.8~5.0nm is 90% of the particle diameter _{D 50.} It is characterized by being 5 times or less.

  The noble metal fine particles according to the present invention are at least one kind of fine particles selected from the group consisting of noble metal fine particles, noble metal alloy fine particles, noble metal compound fine particles and noble metal alloy compound fine particles. Examples of the noble metal that forms such noble metal fine particles include gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), osmium ( Os). These noble metals may be used alone to form noble metal fine particles, or two or more may form noble metal alloy fine particles. Among these noble metal fine particles, fine particles made of gold, silver, platinum, palladium, rhodium, iridium, or alloys thereof are preferable from the viewpoint of exhibiting excellent catalytic activity.

  Moreover, in the noble metal colloid solution of the present invention, fine particles of a noble metal alloy of the noble metal and a metal other than the noble metal can be used as the noble metal fine particles. Examples of the metal other than the noble metal include iron, nickel, cobalt, copper, manganese, chromium, zinc, niobium, molybdenum, tantalum, and tungsten. These metals may be used alone or in combination of two or more.

  Further, the noble metal fine particles according to the present invention include fine particles of noble metal compounds such as oxides, hydroxides, salts, carbides, nitrides and sulfides of the noble metals; oxides, hydroxides and salts of the noble metal alloys. Fine particles of noble metal alloy compounds such as carbides, nitrides and sulfides can also be used. The noble metal alloy compound means a composite metal compound such as a composite metal oxide containing at least one kind of noble metal.

The noble metal-based colloid solution of the present invention is a dispersion of such noble metal-based fine particles. The particle size distribution of the fine particles in the noble metal-based colloid solution can be measured by, for example, a dynamic light scattering method. Particles in the colloidal solution of the present invention, the particle diameter _{D 50} which cumulative mass in measured particle size distribution in this way is 50 percent 0.8～5.0Nm (preferably 0.8～3.0Nm) In addition, the particle diameter D ₉₀ with a cumulative mass of 90% is 2.5 times or less (preferably 2.0 times or less) of the particle diameter D ₅₀ . Such noble metal fine particles having particle diameters D ₅₀ and D ₉₀ are uniformly dispersed in the colloidal solution. By using such a noble metal-based colloidal solution, uniform noble metal-based catalyst particles having a small particle diameter can be obtained, and when the noble metal-based catalyst particles are used as a catalyst, the particle growth is difficult and the catalytic activity is improved. It is possible to suppress the decrease. Further, when the noble metal-based fine particles are supported on the composite oxide aggregated particles having an alumina skeleton, the composite oxide aggregated particles (catalyst support) are changed by changing the pore diameter of the composite oxide aggregated particles having the alumina skeleton. It is possible to arbitrarily control the pore size distribution. Therefore, by using the noble metal colloidal solution of the present invention at the time of catalyst preparation, it becomes possible to design an ideally shaped catalyst according to the operating temperature range of the catalyst, for example, optimal for gas diffusivity. It is possible to obtain a highly heat-resistant catalyst having a pore size, in which noble metal-based fine particles are uniformly arranged in the pores of the catalyst carrier and having ideal catalytic activity in the diffusion-controlled region.

  The noble metal colloid solution of the present invention contains a polymer dispersant. Due to the presence of the polymer dispersant in the colloidal solution, the surface of the noble metal-based fine particles is positively or negatively charged depending on the type of the polymer dispersant, so that it is difficult to agglomerate and is stable in a uniform state. Thus, it can be dispersed in the colloidal solution. For example, when a (meth) acrylic acid polymer, which will be described later, is used as the polymer dispersant, the surface of the noble metal fine particles is negatively charged, so that it is difficult to agglomerate and stably in a colloidal solution in a uniform state. It becomes possible to disperse. In addition, since the surface of the noble metal fine particles is negatively charged, an electrostatic attractive force acts on the positively charged carrier and a repulsive force acts on the negatively charged carrier. It is possible to adsorb noble metal-based fine particles.

In the colloidal solution of the present invention, the content of the polymer dispersant is preferably 30 to 500 mg / m ^{2 and} more preferably 50 to 250 mg / m ² with respect to the unit surface area of the noble metal-based fine particles. When the content of the polymer dispersant is within the above range, the noble metal-based fine particles have a small particle size, are uniform, hardly aggregate, are uniformly dispersed, and obtain a noble metal-based colloid solution with excellent storage stability. Can do. On the other hand, when the content of the polymer dispersant is less than the lower limit, the surface of the noble metal fine particles cannot be sufficiently covered with the polymer dispersant, and the noble metal fine particles aggregate to form larger aggregates. On the other hand, when the above upper limit is exceeded, since a large amount of free polymer dispersant is present in the noble metal colloid solution, the crosslinking reaction of the polymer dispersant proceeds remarkably and the noble metal fine particles are aggregated to form particles. There is a tendency to form aggregates having a large diameter.

  Although there is no restriction | limiting in particular as a weight average molecular weight of such a polymer dispersing agent, 800-4000 are preferable and 800-3000 are more preferable. When the weight average molecular weight of the polymer dispersant is in the above range, the noble metal-based fine particles have a small particle size, are uniform, hardly aggregate, are uniformly dispersed, and obtain a noble metal-based colloid solution with excellent storage stability. be able to. On the other hand, when the weight average molecular weight of the polymer dispersant is less than the lower limit, even if the polymer dispersant is adsorbed to the noble metal fine particles, the repulsive force due to steric hindrance or electrostatic repulsion is not sufficiently exhibited, and the noble metal fine particles are aggregated. On the other hand, when the upper limit is exceeded, the polymer dispersant becomes extremely larger than the noble metal-based fine particles, and the noble metal-based fine particles tend to aggregate to form large aggregates. The weight average molecular weight is a value measured by gel permeation chromatography (GPC) and converted to standard polystyrene.

  The polymer dispersant used in the present invention includes a homopolymer of (meth) acrylic acid, a copolymer of (meth) acrylic acid and (meth) acrylic acid ester, (meth) acrylic acid and other vinyl monomers (Meth) acrylic acid polymers such as copolymers, and (meth) acrylic acid polymers are preferred from the viewpoint of maintaining water solubility, and (meth) acrylic acid homopolymers. A copolymer of (meth) acrylic acid and (meth) acrylic acid ester is more preferred.

  Moreover, when a (meth) acrylic acid polymer is used as the polymer dispersant, the pH of the colloidal solution of the present invention is preferably 5.0 to 10.0, and 6.0 to 9.0. It is more preferable. When the pH of the colloidal solution is within the above range, the noble metal-based fine particles have a small particle size, are uniform, hardly aggregate, are uniformly dispersed, and can provide a noble metal-based colloid solution with excellent storage stability. . On the other hand, since the carboxyl group in the (meth) acrylic acid polymer does not dissociate when the pH is less than the lower limit, the amount of adsorption of the (meth) acrylic acid polymer to the noble metal fine particles decreases, and the noble metal fine particles On the other hand, when the above upper limit is exceeded, depending on the type of noble metal fine particles, the surface of the noble metal fine particles tends to be negatively charged and the carboxyl group is dissociated. There is a tendency that the amount of adsorption decreases and the noble metal-based fine particles aggregate.

  The ratio of those having a hydrophilic group among all repeating units in the (meth) acrylic acid polymer is 90 when the pH of the resulting noble metal colloid solution is 5.0 or more and less than 7.0. % To 100% is preferable. When the pH of the noble metal colloid solution is 7.0 or more and 10.0 or less, the ratio of the repeating unit having a hydrophilic group is preferably 50% or more and 100% or less, and more preferably 75% or more and 100% or less. When the ratio of the repeating unit having a hydrophilic group is within the above range, the (meth) acrylic acid polymer is adsorbed to the noble metal fine particles in a loop train type, so that the repulsive force due to steric hindrance acts and the aggregation of the noble metal fine particles is effective. The noble metal-based fine particles can be obtained in such a manner that the noble metal-based fine particles have a small particle size, are uniform, hardly aggregate, are uniformly dispersed, and are excellent in storage stability. On the other hand, when the ratio of the repeating unit having a hydrophilic group is less than the lower limit, the dissociated carboxyl group in the (meth) acrylic acid polymer is insufficient, and the adsorption amount of the (meth) acrylic acid polymer to the noble metal fine particles is reduced. , And noble metal-based fine particles tend to aggregate.

  The solvent used in the present invention is preferably water. Accordingly, a colloidal aqueous solution is preferred as the colloidal solution of the present invention.

Such a noble metal-based colloidal solution of the present invention is, for example, a method of mixing two or more kinds of raw material solutions (preferably raw material aqueous solution, the same shall apply hereinafter), and among the two or more kinds of raw material solutions, At least one of the above-mentioned noble metal ions is used, and at least one of the two or more kinds of raw material solutions is used which contains the polymer dispersant, and the raw material solution has a shear rate. It can be manufactured by a method in which it is directly directly introduced into the region of 3000 sec ⁻¹ or more and homogeneously mixed. According to this method, it is possible to uniformly disperse the noble metal-based fine particles without agglomerating even in water in which the noble metal-based fine particles easily aggregate.

  As an apparatus used for producing such a noble metal colloid solution, for example, the apparatus shown in FIG. Hereinafter, a suitable apparatus for producing the noble metal colloid solution of 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 may be omitted.

  The manufacturing apparatus shown in FIG. 1 includes a homogenizer 10 as a high-speed stirring device, and the tip (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. Furthermore, the rotor 11 is connected to a motor 15 via a rotating shaft 14 and has a structure capable of rotating at high speed.

  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. Therefore, 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 nozzles 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 apparatus. 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 be 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 16A and the nozzles 16B are alternately provided in a row in the outer circumferential 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, preferably shear rate is 3000 sec ^-1 or more, and particularly preferably 6000Sec ^-1 or more. When the shear rate in this region is less than the lower limit, the aggregation of the noble metal-based fine particles and the structure in which the polymer dispersant is adsorbed on the plurality of noble metal-based fine particles are not separated, and a larger aggregate tends to be formed.

  Conditions for achieving such a range of shear rates are affected by the rotational speed of the rotor and the size of the gap between the rotor and the stator. Need to be set. The specific rotation speed of the rotor 11 is not particularly limited and varies depending on the size of the device. For example, the outer diameter of the inner stator 13 is 10 mm, the gap between the rotor 11 and the outer stator 12 is 0.2 mm, When the gap between the rotor 11 and the inner stator 13 is 0.2 mm, the rotational speed of the rotor 11 is preferably set to 3000 to 30000 rpm, more preferably 3000 to 20000 rpm, thereby achieving the shear speed in the above range. It becomes possible.

  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, and preferably 0.2 to 0 mm. More preferably, it is 5 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, and preferably 0.2 to 0 mm. More preferably, it is 5 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, high shear rates tend not to be achieved.

  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 introduced 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 time when the raw material solution A (or raw material solution B) introduced from the nozzle 16A (or nozzle 16B) rotates the rotor 11. It is a time until the position of the adjacent nozzle 16B (or nozzle 16A) is reached and mixed with the raw material solution B (or raw material solution A) introduced from the nozzle 16B (or nozzle 16A).

  As mentioned above, although the apparatus used for manufacture of the noble metal system colloid solution of this invention was demonstrated, the manufacturing method of the colloid solution of this invention is not limited to the method of using the manufacturing apparatus shown in FIG. For example, the manufacturing apparatus shown in FIG. 1 is configured so that two kinds of raw material solutions can be introduced, but a nozzle, a raw material solution supply apparatus, or the like may be configured so that three or more kinds of raw material solutions can be introduced. Good.

  Further, 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.

  Next, a preferred embodiment of the method for producing a noble metal colloid solution of the present invention will be described. In the method for producing a noble metal colloid solution of the present invention, the shear rate of the region into which the raw material solution is introduced is set in the above range, and each of the raw material solutions is directly and independently introduced into the region. For example, when the manufacturing apparatus shown in FIG. 1 is used, 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 rotor 11 and the inner stator 13 in FIG. 1 and FIG. The rotor 11 is rotated at a high speed so that the shear rate in the region between is within the above range, and the raw material solution A and the raw material solution B are directly introduced into the region independently from the nozzle 16A and the nozzle 16B, respectively. Thus, each raw material solution directly introduced into the region where the shear rate is extremely high is homogeneously mixed in a very short time to complete the reaction, and noble metal-based fine particles are formed. At the same time, the polymer dispersant is instantaneously and effectively adsorbed on the surface of the noble metal-based fine particles in the reaction field at an extremely high shear rate. As a result, a colloidal solution in which noble metal fine particles are highly dispersed can be obtained.

  In the method for producing a colloidal solution of the present invention, the noble metal ion and the polymer dispersant may be contained in the same raw material solution or in different raw material solutions. It is preferable that at least one of the plurality of raw material solutions contains the noble metal ion, and at least one of the remaining raw material solutions contains the polymer dispersant. Furthermore, reducing agents such as hydrazine and sodium borohydride may not be included in the same raw material solution as the noble metal ion, but may be included in the same raw material solution as the polymer dispersant. For example, when the manufacturing apparatus shown in FIG. 1 is used, both the noble metal ions and the polymer dispersant may be contained in the raw material solution A, or the raw solution A contains the noble metal ions. The polymer dispersant may be contained in B, but the latter is preferable.

  In the method for producing a noble metal colloid solution of the present invention, the cation concentration of the raw material solution containing the noble metal ions (for example, the raw material solution A) is preferably 0.0001 to 0.5 mol / L, 0.001 -0.2 mol / L is more preferable. When the cation concentration is in the above-mentioned range, the noble metal-based fine particles have a small particle size, are uniform, hardly aggregate, are uniformly dispersed, and a noble metal-based colloid 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 noble metal fine particles tends to decrease. On the other hand, when the cation concentration exceeds the upper limit, the interparticle distance of the noble metal fine particles in the noble metal colloid solution is shortened. The polymer dispersant adsorbed on the system fine particles tends to be adsorbed on a large number of noble metal based fine particles, and the noble metal based fine particles tend to aggregate.

  When a (meth) acrylic acid polymer is used as a polymer dispersant in the method for producing a colloidal solution of the present invention, it is preferable to adjust the pH of the colloidal solution to 5.0 to 10.0. It is more preferable to adjust to 0-9.0. In particular, when the (meth) acrylic acid-based polymer having a hydrophilic group among all repeating units of 90% to 100% is used, the colloidal solution has a pH of 5.0 to 10. More preferably, it is adjusted to 0 or less. 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, uniform noble metal-based fine particles having a small particle diameter can be obtained, and a noble metal-based colloidal solution having excellent storage stability can be obtained. On the other hand, since the carboxyl group in the (meth) acrylic acid polymer does not dissociate when the pH is less than the lower limit, the amount of adsorption of the (meth) acrylic acid polymer to the noble metal fine particles decreases, and the noble metal fine particles On the other hand, when the above upper limit is exceeded, depending on the type of noble metal fine particles, the surface of the noble metal fine particles tends to be negatively charged and the carboxyl group is dissociated. There is a tendency that the amount of adsorption decreases and the noble metal-based fine particles aggregate.

  Although there is no restriction | limiting in particular as a liquid feeding rate of each raw material solution, 1.0-30 ml / min is preferable. When the feed rate of the raw material solution is less than the lower limit, the production efficiency of the noble metal-based fine particles tends to decrease, and when the upper limit is exceeded, the aggregate particle diameter of the noble metal-based fine particles in the liquid tends to increase.

  The reaction system applicable to the method for producing the noble metal-based colloidal solution of the present invention is not particularly limited, and examples thereof include a hydrolysis reaction of alkoxide and a precipitation reaction utilizing a change in solubility using a poor solvent. Even in reactions with very fast nucleation rate and reaction rate such as reaction and oxidation-reduction reaction, noble metal fine particles have a small particle size and uniform according to the above production method, and a colloidal solution with excellent storage stability can be obtained. The production method of the present invention is particularly useful for such a reaction system having a very high nucleation rate and reaction rate.

A specific reaction system in such neutralization reaction, oxidation-reduction reaction, etc. is not particularly limited, but an oxidation-reduction reaction system is preferable. For example, when two kinds of raw material solutions are used, the following reaction system is used. A redox reaction system using raw material solutions A and B is more preferable.
Raw material solution A (precious metal ion-containing solution): A solution containing silver nitrate, palladium nitrate, chloroplatinic acid, rhodium nitrate, dinitrodiammine platinum nitrate (hereinafter referred to as “platinum nitrate”), and the like.
Raw material solution B (reducing agent): acetaldehyde solution, sodium borohydride solution, hydrazine, ethanol and the like.

  The polymer dispersant may be contained in at least one of the raw material solution A and the raw material solution B in any of the above reactions, but is preferably contained in the raw material solution B. For example, in the oxidation-reduction reaction, it is preferable to use a raw material solution A containing noble metal ions, which are raw materials for noble metal-based fine particles, and a raw material solution B containing a reducing agent and a polymer dispersant.

  The composition and combination of such raw material solutions can be appropriately set according to the type of the target noble metal colloid solution and the type of raw material used.

  In the method for producing a noble metal colloid solution of the present invention described above, two or more kinds of raw material solutions are not mixed in advance under a gentle stirring condition, and the stirring conditions are not different for each raw material solution. The noble metal fine particles produced are mixed in a very short time under a high shear force, and the precipitating metal fine particles are adsorbed on the surface simultaneously with the precipitation of the noble metal fine particles, and the dispersion state is stabilized. It becomes possible to obtain a colloidal solution having a small diameter and a uniform diameter and having excellent storage stability.

  The composition of the noble metal-based colloidal solution obtained by the method for producing a colloidal solution of the present invention is not particularly limited. By using various raw material solutions, noble metal-based noble metals, noble metal alloys, noble metal compounds, noble metal alloy compounds, and the like are used. A colloidal solution can be obtained.

  In addition, the noble metal colloid solution of the present invention is highly dispersible in the liquid, and the noble metal fine particles are supported on the catalyst carrier in a highly dispersed state by being homogeneously mixed with the highly dispersible catalyst carrier colloid solution. Can do. Furthermore, in the noble metal colloid solution of the present invention, the polymer dispersant can be instantaneously desorbed from the noble metal fine particles by adjusting the pH, so that the noble metal fine particles can be easily arranged uniformly on the catalyst carrier. It can be supported. In addition, when the catalyst carrier is prepared using a metal oxide or composite metal oxide colloidal solution prepared in the same manner as the noble metal colloid solution of the present invention, the metal oxide particles or composite metal which is the catalyst carrier. Since the polymer dispersant can be instantaneously desorbed from the oxide particles, the noble metal-based fine particles can be supported in a more uniform state.

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

Example 1
First, ion-exchanged water is added to 4.85 g of a platinum nitrate solution having a Pt content of 4.565% by mass, and a noble metal ion-containing raw material aqueous solution (raw material solution A) having a cation (Pt ion) concentration of 0.0025 mol / L. ) 125 ml was prepared. Also, ion-exchanged water was added to a mixture of 0.95 g of hydrazine monohydrate and 6.4 g of polyacrylic acid sodium salt (weight average molecular weight: 1200, ratio of those having a hydrophilic group among all repeating units: 100%). These were dissolved to prepare 125 ml of an aqueous polymer dispersant solution (raw material solution B). A small amount of nitric acid was added to the aqueous polymer dispersant solution so that the pH after mixing with the noble metal ion-containing raw material aqueous solution was 6.0.

  Next, a noble metal colloid solution was prepared using the manufacturing apparatus (super agitation reactor) shown in FIG. The stator 13 was a 48-hole type in which 24 nozzles 16A and 24 nozzles 16B were provided.

  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 raw material solution A and the raw material solution B are mixed while rotating the rotor 11 of the homogenizer 10 at a rotational speed of 10,000 rpm. Using a tube pump (not shown) at a supply rate of 2.5 ml / min, the solution is fed from the nozzle 16A and the nozzle 16B to the region between the rotor 11 and the inner stator 13 and mixed to obtain a noble metal colloid solution. Produced.

The outer diameter of the rotor 11 was 17.8 mm, the gap between the rotor 11 and the outer stator 12 was 0.5 mm, and the shear rate in the region between them was 18730 sec ⁻¹ . The outer diameter of the inner stator 13 was 12.2 mm, the gap between the rotor 11 and the inner stator 13 was 0.2 mm, and the shear rate in the region between them was 18730 sec ⁻¹ . Furthermore, the time from the introduction of the raw material solution A and the raw material solution B into the region until the homogeneous mixing was 0.126 msec. Here, the time until homogeneous mixing is defined as the time until the raw material solution A or the raw material solution B discharged from the nozzle 16A or the nozzle 16B reaches the adjacent nozzle 16B or the nozzle 16A by the rotation of the rotor 11. It is what is done.

  The noble metal colloidal solution overflowing from the beaker 20 was received by setting a 1 L beaker (not shown) further below the beaker 20.

  The pH of the obtained noble metal colloid solution is shown in Table 1. In addition, several drops of the noble metal colloid solution were dropped on the carbon support film and observed with a high resolution scanning transmission electron microscope (high resolution STEM, “JEM2100F-Cs collector” manufactured by JEOL Ltd.). The result is shown in FIG. 5A. Moreover, the electron beam diffraction pattern was measured using the transmission electron microscope. FIG. 5B shows an electron diffraction image of the noble metal-based fine particles. When the measured value obtained from this electron beam diffraction image was compared with the theoretical value for the distance between hkl planes, it was confirmed that the fine particles contained in the noble metal colloid solution were platinum fine particles (see Table 2).

Next, the particle size distribution of the fine particles in this noble metal colloid solution was measured by a dynamic light scattering method (using “Nanotrac 250” manufactured by Nikkiso Co., Ltd.). The noble metal particle diameter D ₅₀ cumulative mass from the particle size distribution of the particles in the colloidal solution is 50% _(average particle diameter) and cumulative mass was determined particle diameter D ₉₀ which is 90%. Further, the particle size distribution of the fine particles was measured in the same manner as described above for the noble metal-based colloid solution that was allowed to stand for 30 days, and the particle size D _{50 at} which the cumulative mass was 50% was determined. These results are shown in Table 1.

(Example 2)
First, nitric acid and ion-exchanged water are added to 2.71 g of a palladium nitrate solution having a Pd content of 8.2% by mass to obtain a noble metal having a cation (Pd ion) concentration of 0.0025 mol / L and a pH of 6.0. 125 ml of ion-containing raw material aqueous solution was prepared. Also, ion-exchanged water was added to a mixture of 0.95 g of hydrazine monohydrate and 6.4 g of polyacrylic acid sodium salt (weight average molecular weight: 1200, ratio of those having a hydrophilic group among all repeating units: 100%). These were dissolved to prepare 125 ml of an aqueous polymer dispersant solution. A small amount of nitric acid was added to the aqueous polymer dispersant solution so that the pH after mixing with the noble metal ion-containing raw material aqueous solution was 6.0.

  Next, a noble metal colloid solution was prepared using the production apparatus shown in FIG. 1 in the same manner as in Example 1 except that the noble metal ion-containing raw material aqueous solution and the polymer dispersant aqueous solution were used as the raw material solutions A and B, respectively. Produced.

  The pH of the obtained noble metal colloid solution is shown in Table 1. The fine particles in the noble metal colloid solution were observed with a high resolution STEM and identified with an electron diffraction pattern in the same manner as in Example 1. The results are shown in FIGS. When the measured value and the theoretical value of the hkl interplane distance were compared in the same manner as in Example 1, it was confirmed that the fine particles contained in the noble metal colloid solution were palladium fine particles (see Table 3).

Further, in the same manner as in Example 1, the particle size distribution of the fine particles in the noble metal colloid solution is measured, and the particle diameter D ₅₀ (average particle diameter) at which the cumulative mass becomes 50% and the particle diameter at which the cumulative mass becomes 90%. D ₉₀ was determined. In addition, the particle size distribution of the fine particles was measured in the same manner as described above for the noble metal-based colloid solution that was allowed to stand for 30 days, and the particle diameter D _{50 at} which the cumulative mass was 50% was determined. These results are shown in Table 1.

(Example 3)
First, nitric acid and ion-exchanged water were added to 8.07 g of a rhodium nitrate solution having an Rh content of 2.75% by mass, and 125 ml of a noble metal ion-containing raw material aqueous solution having a cation (Rh ion) concentration of 0.0025 mol / L. Prepared. Also, ion-exchanged water was added to a mixture of 0.95 g of hydrazine monohydrate and 6.4 g of polyacrylic acid sodium salt (weight average molecular weight: 1200, ratio of those having a hydrophilic group among all repeating units: 100%). These were dissolved to prepare 125 ml of an aqueous polymer dispersant solution. A small amount of nitric acid was added to the aqueous polymer dispersant solution so that the pH after mixing with the noble metal ion-containing raw material aqueous solution was 6.0.

  Next, a noble metal colloid solution was prepared using the production apparatus shown in FIG. 1 in the same manner as in Example 1 except that the noble metal ion-containing raw material aqueous solution and the polymer dispersant aqueous solution were used as the raw material solutions A and B, respectively. Produced.

  The pH of the obtained noble metal colloid solution is shown in Table 1. The fine particles in the noble metal colloid solution were observed with a high resolution STEM and identified with an electron diffraction pattern in the same manner as in Example 1. The results are shown in FIGS. When the measured value and the theoretical value of the hkl interplane distance were compared in the same manner as in Example 1, it was confirmed that the fine particles contained in the noble metal colloid solution were rhodium fine particles (see Table 4).

Further, in the same manner as in Example 1, the particle size distribution of the fine particles in the noble metal colloid solution is measured, and the particle diameter D ₅₀ (average particle diameter) at which the cumulative mass becomes 50% and the particle diameter at which the cumulative mass becomes 90%. D ₉₀ was determined. In addition, the particle size distribution of the fine particles was measured in the same manner as described above for the noble metal-based colloid solution that was allowed to stand for 30 days, and the particle diameter D _{50 at} which the cumulative mass was 50% was determined. These results are shown in Table 1.

Example 4
First, nitric acid and ion-exchanged water were added to 0.106 g of silver nitrate to prepare 125 ml of a noble metal ion-containing raw material aqueous solution having a cation (Ag ion) concentration of 0.0025 mol / L. Also, ion-exchanged water was added to a mixture of 0.95 g of hydrazine monohydrate and 6.4 g of polyacrylic acid sodium salt (weight average molecular weight: 1200, ratio of those having a hydrophilic group among all repeating units: 100%). These were dissolved to prepare 125 ml of an aqueous polymer dispersant solution. A small amount of nitric acid was added to the aqueous polymer dispersant solution so that the pH after mixing with the noble metal ion-containing raw material aqueous solution was 6.0.

  Next, a noble metal colloid solution was prepared using the production apparatus shown in FIG. 1 in the same manner as in Example 1 except that the noble metal ion-containing raw material aqueous solution and the polymer dispersant aqueous solution were used as the raw material solutions A and B, respectively. Produced.

  The pH of the obtained noble metal colloid solution is shown in Table 1. The fine particles in the noble metal colloid solution were observed with a high resolution STEM and identified with an electron diffraction pattern in the same manner as in Example 1. The results are shown in FIGS. When the measured value and the theoretical value of the hkl interplane distance were compared in the same manner as in Example 1, it was confirmed that the fine particles contained in the noble metal colloid solution were silver oxide fine particles (see Table 5).

Further, in the same manner as in Example 1, the particle size distribution of the fine particles in the noble metal colloid solution is measured, and the particle diameter D ₅₀ (average particle diameter) at which the cumulative mass becomes 50% and the particle diameter at which the cumulative mass becomes 90%. D ₉₀ was determined. In addition, the particle size distribution of the fine particles was measured in the same manner as described above for the noble metal-based colloid solution that was allowed to stand for 30 days, and the particle diameter D _{50 at} which the cumulative mass was 50% was determined. These results are shown in Table 1.

(Example 5)
First, ion-exchanged water was added to a mixture of 4.85 g of a platinum nitrate solution having a Pt content of 4.565% by mass and 8.07 g of a rhodium nitrate solution having an Rh content of 2.75% by mass to obtain a cation (Pt Ion / Rh ion = 5: 1) 125 ml of a noble metal ion-containing raw material aqueous solution having a concentration of 0.0030 mol / L was prepared. Also, ion-exchanged water was added to a mixture of 0.95 g of hydrazine monohydrate and 6.4 g of polyacrylic acid sodium salt (weight average molecular weight: 1200, ratio of those having a hydrophilic group among all repeating units: 100%). These were dissolved to prepare 125 ml of an aqueous polymer dispersant solution. A small amount of nitric acid was added to the aqueous polymer dispersant solution so that the pH after mixing with the noble metal ion-containing raw material aqueous solution was 6.0.

  Next, a noble metal alloy colloid solution was prepared using the production apparatus shown in FIG. 1 in the same manner as in Example 1 except that the noble metal ion-containing raw material aqueous solution and the polymer dispersant aqueous solution were used as the raw material solutions A and B, respectively. Produced.

  Table 1 shows the pH of the obtained noble metal alloy colloid solution. Further, the fine particles in the noble metal alloy colloid solution were observed with a high resolution STEM and identified with an electron diffraction pattern in the same manner as in Example 1. The results are shown in FIGS. When the measured value and the theoretical value of the hkl interplane distance were compared in the same manner as in Example 1, it was confirmed that the fine particles contained in the noble metal alloy colloid solution were platinum / rhodium alloy fine particles (see Table 6).

Further, in the same manner as in Example 1, the particle size distribution of the fine particles in the noble metal alloy colloid solution is measured, and the particle diameter D ₅₀ (average particle diameter) at which the cumulative mass becomes 50% and the particle diameter at which the cumulative mass becomes 90%. D ₉₀ was determined. In addition, the particle size distribution of the fine particles of the noble metal alloy colloid solution that was allowed to stand for 30 days was measured in the same manner as described above, and the particle size D _{50 at} which the cumulative mass was 50% was determined. These results are shown in Table 1.

Example 6
A noble metal colloid solution was prepared in the same manner as in Example 1 except that the rotation speed of the rotor 11 was changed to 5000 rpm. In this case, the shear rate in the region between the rotor 11 and the outer stator 12 was 9365 sec ⁻¹ , and the shear rate in the region between the rotor 11 and the inner stator 13 was 9365 sec ⁻¹ . Further, the time from when the raw material solution A and the raw material solution B were introduced into the region until they were homogeneously mixed was 0.252 msec.

The pH of the obtained noble metal colloid solution is shown in Table 1. Further, in the same manner as in Example 1, the particle size distribution of the fine particles in the noble metal colloid solution was measured, and the particle diameter D ₅₀ (average particle diameter) at which the cumulative mass was 50% and the particle diameter at which the cumulative mass was 90%. D ₉₀ was determined. Further, the particle size distribution of the fine particles was measured in the same manner as described above for the noble metal colloid solution that was allowed to stand for 30 days, and the particle diameter D _{50 at} which the cumulative mass was 50% was determined. These results are shown in Table 1.

(Comparative Example 1)
4.85 g of platinum nitrate solution having a Pt content of 4.565% by mass, 0.95 g of hydrazine monohydrate, and 3.2 g of polyvinylpyrrolidone having a weight average molecular weight of 10,000 represented by the above formula (1) are ion-exchanged water. The mixture was added to 250 ml, and propeller stirring was performed at 300 rpm for 12 hours to prepare a noble metal colloid solution. The amount of platinum nitrate solution added is such that the cation (Pt ion) concentration before colloid formation is 0.0025 mol / L.

The pH of the obtained noble metal colloid solution is shown in Table 1. Further, in the same manner as in Example 1, the particle size distribution of the fine particles in the noble metal colloid solution was measured, and the particle diameter D ₅₀ (average particle diameter) at which the cumulative mass was 50% and the particle diameter at which the cumulative mass was 90%. D ₉₀ was determined. Further, the particle size distribution of the fine particles was measured in the same manner as described above for the noble metal colloid solution that was allowed to stand for 30 days, and the particle diameter D _{50 at} which the cumulative mass was 50% was determined. These results are shown in Table 1.

(Comparative Example 2)
A noble metal colloid solution was prepared in the same manner as in Comparative Example 1 except that polyvinylpyrrolidone was not used. The pH of the obtained noble metal colloid solution is shown in Table 1. Further, in the same manner as in Example 1, the particle size distribution of the fine particles in the noble metal colloid solution was measured, and the particle diameter D ₅₀ (average particle diameter) at which the cumulative mass was 50% and the particle diameter at which the cumulative mass was 90%. D ₉₀ was determined. Further, the particle size distribution of the fine particles was measured in the same manner as described above for the noble metal colloid solution that was allowed to stand for 30 days, and the particle diameter D _{50 at} which the cumulative mass was 50% was determined. These results are shown in Table 1.

(Comparative Example 3)
A noble metal-based colloidal solution was prepared in the same manner as in Example 1 except that the rotation speed of the rotor 11 was changed to 1000 rpm. In this case, the shear rate in the region between the rotor 11 and the outer stator 12 was 1873 sec ⁻¹ , and the shear rate in the region between the rotor 11 and the inner stator 13 was 1873 sec ⁻¹ . Further, the time from when the raw material solution A and the raw material solution B were introduced into the region until they were homogeneously mixed was 1.25 msec.

The pH of the obtained noble metal colloid solution is shown in Table 1. Further, in the same manner as in Example 1, the particle size distribution of the fine particles in the noble metal colloid solution was measured, and the particle diameter D ₅₀ (average particle diameter) at which the cumulative mass was 50% and the particle diameter at which the cumulative mass was 90%. D ₉₀ was determined. Further, the particle size distribution of the fine particles was measured in the same manner as described above for the noble metal colloid solution that was allowed to stand for 30 days, and the particle diameter D _{50 at} which the cumulative mass was 50% was determined. These results are shown in Table 1.

(Reference Example 1)
Example except that 6.4 g of polyacrylic acid sodium salt having a weight average molecular weight of 8000 (ratio of those having a hydrophilic group among all repeating units: 100%) was used instead of polyacrylic acid sodium salt having a weight average molecular weight of 1200 In the same manner as in No. 1, a noble metal colloid solution was prepared. The pH of the obtained noble metal colloid solution is shown in Table 1. Further, in the same manner as in Example 1, the particle size distribution of the fine particles in the noble metal colloid solution was measured, and the particle diameter D ₅₀ (average particle diameter) at which the cumulative mass was 50% and the particle diameter at which the cumulative mass was 90%. D ₉₀ was determined. Further, the particle size distribution of the fine particles was measured in the same manner as described above for the noble metal colloid solution that was allowed to stand for 30 days, and the particle diameter D _{50 at} which the cumulative mass was 50% was determined. These results are shown in Table 1.

  As is clear from the results shown in Table 1, in the noble metal colloid solutions (Examples 1 to 6) obtained by mixing the raw material solutions under high shear force by the production method of the present invention, the average particle size is It was confirmed that noble metal fine particles having a narrow particle size distribution in the nano order are dispersed. Further, this noble metal colloid solution was excellent in storability without any change in the average particle diameter of the noble metal fine particles even after being stored for 30 days.

  On the other hand, when the polymer dispersant is not added (Comparative Example 1) and when the propeller is stirred (Comparative Example 2), noble metal-based fine particles having a large average particle diameter of nano-order and a wide particle size distribution are formed. I found out that Moreover, when it preserve | saved for 30 days, the average particle diameter of noble metal type fine particles became large, and it was inferior to preservability.

Furthermore, when the raw material solution is mixed in a region where the shear rate is less than 3000 sec ⁻¹ (Comparative Example 3), and when the weight average molecular weight of the polyacrylic acid sodium salt as the polymer dispersant exceeds 4000 (Reference Example) In 1), it was found that noble metal fine particles having an increased average particle size in water and a wide particle size distribution were formed. Moreover, when it preserve | saved for 30 days, the average particle diameter of noble metal type fine particles became large, and it was inferior to preservability.

  As described above, according to the present invention, it is possible to obtain a noble metal-based colloid solution excellent in storage stability in which noble metal-based fine particles having a small particle size and a narrow particle size distribution are uniformly dispersed.

  Therefore, since the noble metal-based colloid solution of the present invention is a nano-sized highly dispersed noble metal-based fine particle, for example, by supporting the noble metal-based fine particle on the catalyst carrier using such a noble metal-based colloid solution. In addition, it is possible to obtain a noble metal catalyst supported in a state in which noble metal fine particles are highly dispersed. A catalyst in which such noble metal-based fine particles are highly dispersed is expected to exhibit a nano-size effect and is useful as a noble metal-based catalyst having excellent catalytic activity.

  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 (15)

Containing at least one kind of noble metal fine particles selected from the group consisting of noble metal fine particles, noble metal alloy fine particles, noble metal compound fine particles and noble metal alloy compound fine particles, and a polymer dispersant;
The noble metal particles, 2 the particle diameter _{D 90} of the particle diameter _{D 50} of and cumulative mass is a particle diameter _{D 50} which cumulative mass in the particle size distribution is 50% 0.8~5.0nm becomes 90% .5 times or less,
A noble metal-based colloidal solution.   2. The noble metal colloid solution according to claim 1, wherein the polymer dispersant has a weight average molecular weight of 800 to 4000.   The noble metal colloid solution according to claim 1 or 2, wherein the polymer dispersant is a (meth) acrylic acid polymer.   The noble metal-based colloidal solution according to claim 3, wherein the pH is 5.0 to 10.0. A noble metal colloid solution containing the noble metal fine particles produced by mixing two or more kinds of raw material solutions;
At least one of the two or more raw material solutions contains a noble metal ion that is a raw material of the noble metal-based fine particles, and at least one of the two or more raw material solutions is the polymer dispersant. Containing
5. The method according to claim ¹ , wherein each raw material solution is directly and independently introduced into a region having a shear rate of 3000 sec ⁻¹ or more and is homogeneously mixed. The noble metal-based colloidal solution according to one item.   At least one of the two or more types of raw material solutions contains the noble metal ion, and at least one of the remaining raw material solutions contains the polymer dispersant. The noble metal colloid solution according to claim 5.   The noble metal-based colloidal solution according to claim 6, wherein the raw material solution containing the polymer dispersant further contains a reducing agent.   The noble metal colloid solution according to any one of claims 5 to 7, wherein a cation concentration of the raw material solution containing the noble metal ions is 0.0001 to 0.5 mol / L. Two or more raw material solutions are mixed to produce a noble metal colloid solution containing at least one noble metal fine particle selected from the group consisting of noble metal fine particles, noble metal alloy fine particles, noble metal compound fine particles and noble metal alloy compound fine particles. A method,
At least one of the two or more kinds of raw material solutions contains a noble metal ion that is a raw material of the noble metal-based fine particles, and at least one of the two or more kinds of raw material solutions contains a polymer dispersant. Contains
A method for producing a noble metal-based colloidal solution, wherein each of the raw material solutions is directly and independently introduced into a region having a shear rate of 3000 sec ⁻¹ or more and is homogeneously mixed.   At least one of the two or more types of raw material solutions contains the noble metal ion, and at least one of the remaining raw material solutions contains the polymer dispersant. The method for producing a noble metal-based colloid solution according to claim 9.   The method for producing a noble metal colloid solution according to claim 10, wherein the raw material solution containing the polymer dispersant further contains a reducing agent.   The cation concentration of the raw material solution containing the noble metal ions is 0.0001 to 0.5 mol / L, The production of a noble metal colloid solution according to any one of claims 9 to 11 Method.   The method for producing a noble metal-based colloidal solution according to any one of claims 9 to 12, wherein the polymer dispersant has a weight average molecular weight of 800 to 4000.   The method for producing a noble metal colloid solution according to any one of claims 9 to 13, wherein the polymer dispersant is a (meth) acrylic acid polymer.   The method for producing a noble metal colloid solution according to claim 14, wherein the pH is adjusted to 5.0 to 10.0.