Fine particle dispersion dispersed with fine particle containing silica particle with coating layer, i.e. silica particle having zirconium-containing silica layer in dispersant, fine particle used for catalyst carrier, and method for producing fine particle dispersion dispersed with fine particle containing silica particle with coating layer, i.e. silica particle having silica layer containing catalyst for organic reaction and zirconium, in dispersant

Abstract

To provide a catalyst for an organic reaction useful as a catalyst for an organic reaction such as a decomposition reaction of an organic compound or a synthetic reaction of an organic compound, and a fine particle useful for a catalyst carrier of the catalyst for the organic reaction.SOLUTION: A fine particle dispersion is obtained by dispersing a fine particle including a silica particle with a coating layer, which is a silica particle having a zirconium-containing silica layer, in a dispersant, where the fine particle has characteristics of the following 1)-4). 1) An average particle diameter (D1) by a dynamic light scattering method is in a range of 10 to 100 nm. 2) A minor axis / major axis ratio by an image analysis method is in a range of 0.75 to 1.0. 3) A value of a Q4 / Q3 ratio by solid29Si-NMR is in a range of 0.387 to 0.655. 4) A Si2P peak position by XPS measurement is in a range of 103.37 to 103.59 eV.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a catalyst for organic reactions that is useful as a catalyst for organic reactions such as decomposition reactions of organic compounds or synthesis reactions of organic compounds, fine particles that are useful as catalyst supports for the catalyst for organic reactions, and a dispersion containing the fine particles, and further relates to a method for producing the dispersion. [Background technology]

[0002] Catalysts are used in a variety of fields, including various organic reactions, reaction promotion in fuel cells, and purification of automobile exhaust gases. Many of these catalysts use porous supports, such as oxides such as silica and alumina, or carbon, on which active metals such as platinum and rhodium or metal compounds are supported, as well as multi-component catalysts in which multiple metals are supported. Support materials used include silica, zeolite, silica-alumina composites, and ceria.

[0003] Patent Document 1 discloses a desulfurization catalyst for catalytic cracking gasoline, which is a catalyst in which vanadium oxide is supported only on the surface portions of porous inorganic oxide microspherical particles, and is characterized in that vanadium oxide is supported on at least a portion of the surface portions.

[0004] Patent Document 2 discloses an oxide-supported gold catalyst in which gold is supported on an oxide support, characterized in that gold clusters are supported on the surface of the oxide support via a boundary layer made of gold oxide, AuOx.

[0005] Patent Document 3 discloses an ethylene decomposition agent in which platinum or a platinum-containing compound is supported on porous silica, and which decomposes ethylene into carbon dioxide and water in the presence of oxygen in an atmosphere of −1 to −40° C.

[0006] Patent Document 4 describes a method for determining the amount of surface hydroxyl groups to be 0.1 to 2.5 μmol / m 2A solid acid catalyst for polyether production is disclosed, which comprises a zirconia-supported silica catalyst having a pKa of -5.6 or less and an acid amount of 20 μmol / g or more.

[0007] Patent Document 5 discloses a method for producing an epoxide, which comprises reacting an olefin, hydrogen, and oxygen in the presence of a catalyst containing a titanium or vanadium zeolite, a noble metal, lead, and bismuth, and discloses the use of a catalyst in which a noble metal is supported on a support selected from the group consisting of carbon, titania, zirconia, niobia, silica, alumina, silica-alumina, tantalum oxide, molybdenum oxide, tungsten oxide, titania-silica, niobia-silica, zirconia-silica, and mixtures thereof. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-000748 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-219004 [Patent Document 3] Japanese Patent Application Publication No. 2017-023889 [Patent Document 4] Japanese Patent Application Laid-Open No. 2007-100073 [Patent Document 5] Special table 2011-500803 publication Summary of the Invention [Problem to be solved by the invention]

[0009] Patent Document 4 discloses a solid acid catalyst (here, "solid acid" refers to a solid having acidic sites on the surface) made of zirconia-supported silica having surface hydroxyl groups. The surface hydroxyl groups cause a decrease in catalytic performance over time, and are converted to hydrophobic groups by reaction with an organic compound or the like to reduce the number of these hydroxyl groups. This solid acid catalyst requires reacting a zirconia compound with silica particles (e.g., 75 μm or larger) in a substantially dry state, followed by calcination at 300 to 1100°C, and it is believed that at least the zirconia component is crystallized. Note that when the zirconia component is crystallized, specific stable crystal faces may be exposed on the surface, and stabilization of the zirconia through crystallization may reduce the catalytic performance of the solid acid. The catalytic function of the solid acid catalyst made of zirconia-supported silica in Patent Document 4 depends solely on the acidic sites present on the surface of the solid acid. Although Patent Document 4 also describes supporting transition metal particles, depending on the catalytic performance solely on the acidic sites may result in insufficient catalytic performance depending on the application and target reaction. Furthermore, in general, synthetic reactions involving two or more phases can result in a significant decrease in the specific surface area of the product due to chemical reactions or fusion of the products, etc. Even in the case of Patent Document 4, if a chemical reaction between zirconia and silica or fusion of zirconia-supported silica progresses in the catalyst preparation process, this can result in a significant decrease in the specific surface area, and process control may be necessary.

[0010] As mentioned above, Patent Document 5 discloses a catalyst for olefin epoxidation in which a noble metal or the like is supported on a carrier, and lists zirconium-silica as an option for the carrier. As with the catalyst of Patent Document 4, the catalyst of Patent Document 5 may also suffer from a significant decrease in specific surface area if a chemical reaction between zirconia and silica or fusion of zirconia-supported silica progresses during the catalyst preparation process, which may require process control.

[0011] Conventionally, in the synthesis process of metal-supported catalysts using silica fine particles (or silica sol) as a catalyst support, there has been a problem of agglomeration of the silica fine particles, which are the catalyst support. Agglomerated silica fine particles tend to be difficult to redisperse, and agglomeration leads to a decrease in the specific surface area of the silica fine particles, resulting in segregation of the supported metal and a decrease in catalytic performance. The present invention relates to a catalyst for organic reactions that is useful as a catalyst for organic reactions such as decomposition reactions of organic compounds or synthesis reactions of organic compounds, fine particles that are useful as catalyst supports for the catalyst for organic reactions, and a dispersion containing the fine particles. It is also an object of the present invention to provide a method for producing the dispersion. [Means for solving the problem]

[0012] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. The present invention includes the following (1) to (6). (1) A microparticle dispersion in which microparticles including silica particles with a coating layer, which are silica particles having a zirconium-containing silica layer, are dispersed in a dispersion medium, wherein the microparticles have the following characteristics 1) to 4): 1) Average particle size (D1) measured by dynamic light scattering is in the range of 10 to 100 nm 2) The ratio of short diameter to long diameter measured by image analysis is in the range of 0.75 to 1.0 3) solid 29 The Q4 / Q3 ratio measured by Si-NMR is in the range of 0.387 to 0.655. 4) The Si2P peak position in XPS measurement is in the range of 103.37 to 103.59 eV (2) The fine particle dispersion according to (1) above, wherein the zirconium-containing silica layer is made of zirconium silicate. (3) Fine particles containing silica particles with a coating layer, which are silica particles having a zirconium-containing silica layer, and having the following characteristics 1) to 4), which are used as a catalyst carrier. 1) Average particle size (D1) measured by dynamic light scattering is in the range of 10 to 100 nm 2) The ratio of short diameter to long diameter measured by image analysis is in the range of 0.75 to 1.0 3) solid 29The Q4 / Q3 ratio measured by Si-NMR is in the range of 0.387 to 0.655. 4) The Si2P peak position in XPS measurement is in the range of 103.37 to 103.59 eV (4) The fine particles according to (3) above, in which the Na content relative to the SiO2 content is less than 100 ppm. (5) A catalyst for organic reactions, comprising the fine particles according to (3) or (4) above carrying transition metal particles. (6) A method for producing a microparticle dispersion, in which a microparticle dispersion is obtained in which microparticles including silica particles with a coating layer, which are silica particles having a zirconium-containing silica layer, are dispersed in a dispersion medium, the method comprising the following steps 1, 2, and 3: Step 1: A step of mixing a zirconium salt of an inorganic acid with a silicic acid solution to obtain a mixed solution. Step 2: A step of adding the mixed solution obtained in the previous step to a silica fine particle dispersion to obtain a precursor solution in which the mass ratio of Zr to SiO2 is in the range of 100 ppm to 10,000 ppm. Step 3: A step of maintaining the precursor solution obtained in the previous step at 50 to 98° C. to obtain the fine particle dispersion. [Effects of the Invention]

[0013] The present invention relates to a catalyst for organic reactions that is useful as a catalyst for organic reactions such as decomposition reactions of organic compounds or synthesis reactions of organic compounds, fine particles that are useful as catalyst supports for the catalyst for organic reactions, and a dispersion containing the fine particles. Furthermore, the present invention can provide a method for producing the dispersion.

[0014] In particular, the manufacturing method of the present invention can prevent the aggregation of supported silica particles (increase in specific surface area), which has been a problem in the manufacturing process of metal-supported catalysts in which a metal is supported on a silica support instead of a conventional silica support. Therefore, segregation of the supported metal on the support is less likely to occur, and the expected deterioration of catalytic performance is less likely to occur. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will now be described. The present invention is a microparticle dispersion in which microparticles including silica particles with a coating layer, which are silica particles having a zirconium-containing silica layer, are dispersed in a dispersion medium, and the microparticles have the following characteristics 1) to 4). 1) Average particle size (D1) measured by dynamic light scattering is in the range of 10 to 100 nm 2) The ratio of short diameter to long diameter measured by image analysis is in the range of 0.75 to 1.0 3) solid 29 The Q4 / Q3 ratio measured by Si-NMR is in the range of 0.387 to 0.655. 4) The Si2P peak position in XPS measurement is in the range of 103.37 to 103.59 eV Such a fine particle dispersion will be hereinafter referred to as the "dispersion of the present invention."

[0016] The present invention also provides fine particles that include silica particles with a coating layer, which are silica particles having a zirconium-containing silica layer, and have the above characteristics 1) to 4), and are used as a catalyst support. Such fine particles will hereinafter also be referred to as "fine particles of the present invention."

[0017] That is, the dispersion of the present invention is obtained by dispersing the fine particles of the present invention in a dispersion medium.

[0018] The present invention also provides a catalyst for organic reactions, in which transition metal particles are supported on the fine particles of the present invention. Such an organic reaction catalyst will hereinafter also be referred to as the "catalyst of the present invention."

[0019] The present invention also provides a method for producing a microparticle dispersion, in which microparticles including silica particles with a coating layer, which are silica particles having a zirconium-containing silica layer, are dispersed in a dispersion medium, the method comprising the following steps 1, 2, and 3: Step 1: A step of mixing a zirconium salt of an inorganic acid with a silicic acid solution to obtain a mixed solution. Step 2: A step of adding the mixed solution obtained in the previous step to a silica fine particle dispersion to obtain a precursor solution in which the mass ratio of Zr to SiO2 is in the range of 100 ppm to 10,000 ppm. Step 3: A step of maintaining the precursor solution obtained in the previous step at 50 to 98° C. to obtain the fine particle dispersion. Such a production method will be hereinafter referred to as the "production method of the present invention."

[0020] The dispersion of the present invention can be produced by the production method of the present invention.

[0021] [Dispersion of the Present Invention and Fine Particles of the Present Invention] The solid content concentration in the dispersion of the present invention is preferably in the range of 1 to 40% by mass. A solid content concentration of less than 1% by mass is undesirable because it reduces the production efficiency of metal-supported catalysts when used as a catalyst support, whereas a solid content concentration of more than 40% by mass is unsuitable because it reduces the storage stability of the fine particle dispersion. Here, the solid content can be determined by performing ignition loss at 1000°C and weighing.

[0022] The fine particles of the present invention are supports (catalyst supports) for supporting active transition metals to exhibit catalytic functions. The surface of the silica microparticles may be entirely covered with a zirconium-containing silica layer, or the silica surface may be partially exposed.For example, if a transition metal such as Ce is used as the active metal supported on the carrier, when the carrier is silica microparticles, the dispersion stability of the silica microparticles will be impaired, resulting in a decrease in specific surface area, and the supported metal will be prone to segregation, making it difficult to obtain a catalyst with stable performance.In the case of the microparticles of the present invention, by mixing a silicic acid solution with a zirconium salt aqueous solution in the manufacturing process, the formation of Si-O-Zr bonds in the subsequent process will be promoted, and the stability of the silica microparticles to transition metals can be improved compared to Si-O-Si bonds due to the influence of electronegativity, as described below.It is presumed that this is suitable for supporting transition metals such as Au, Rh, Pd, or Ce.

[0023] The fine particles of the present invention include silica particles with a coating layer, which are silica particles having a zirconium-containing silica layer. The presence of particles having a zirconium-containing silica layer on the surface thereof can be confirmed as follows. The Si 2P peak position in XPS measurements indicates the bond strength of the Si-O bond. The strength of this chemical bond is thought to be influenced by the elements located around the bond, for example, the Zr element close to the Si-O bond in Si-O-Zr. Because Zr has a lower electronegativity than Si, it is presumed that the electron density around Si in the Si-O-Zr bond is higher than that of normal Si-O-Si. Therefore, by determining the Si 2P peak position, the presence of the Si-O-Zr bond, i.e., the formation of a zirconium silicate layer, can be confirmed.

[0024] [Average particle size] The average particle diameter (D1) of the fine particles of the present invention [measured by dynamic light scattering] is preferably in the range of 10 nm to 100 nm. If the average particle diameter of the fine particles of the present invention is less than 10 nm, aggregation tends to occur easily in the catalyst preparation process, which is undesirable. Similarly, if the average particle diameter of the silica fine particles exceeds 100 nm, the specific surface area may be insufficient when used as a support for a metal-supported catalyst, which is undesirable. The average particle size of the fine particles of the present invention is more preferably recommended to be in the range of 12 to 90 nm, and even more preferably recommended to be in the range of 14 to 80 nm.

[0025] [Minor diameter / major diameter ratio] The shape of the microparticles of the present invention is preferably spherical or nearly spherical. Specifically, the ratio of the minor axis to the major axis is preferably in the range of 0.75 to 1.0. When the ratio of the minor axis to the major axis is in this range, the viscosity range during the catalyst preparation process can be set to an appropriate range, and the supported metal can be uniformly supported over the entire support surface, which is desirable because it can exhibit excellent catalytic performance. If the ratio of the minor axis to the major axis of the microparticles of the present invention is less than 0.75, this may lead to an increase in viscosity during the catalyst preparation process, and it may be impossible to obtain a metal-supported catalyst with the desired performance, which is undesirable. The minor axis / major axis ratio of the fine particles of the present invention is more preferably recommended to be in the range of 0.85 to 1.0.

[0026] [solid 29 Q4 / Q3 ratio by Si-NMR] The microparticles of the present invention are 29 In the Si-NMR spectrum, when the peak area attributable to Si(OSi)4 is designated Q4 and the peak area attributable to HO-Si(OSi)3 is designated Q3, the peak area ratio of Q4 / Q3 is preferably 0.387 to 0.655. (Note that the chemical shifts are measured using tetramethylsilane as the reference substance, with Q4 being a peak in the range of -110 ppm to -120 ppm and Q3 being a peak in the range of -100 ppm to -110 ppm.)

[0027] The fine particles of the present invention have two chemical characteristics, and can exhibit excellent performance as a transition metal supported catalyst by supporting transition metal particles. The first chemical characteristic is the solid state of the coated silica particles, which are silica particles having a zirconium-containing silica layer. 29 The first feature, which concerns the Q4 / Q3 ratio measured by Si-NMR, is described below. In transition metal-supported catalysts, in which transition metals or the like are supported on a support, it is desirable for the catalyst to have a high specific surface area in order to further improve catalytic performance. Furthermore, in transition metal-supported catalysts, sufficient contact between the supported metal and the reactants in the catalytic reaction is required to exhibit catalytic function. To achieve this, it is necessary to suppress the growth of supported metal particles due to aggregation, fusion, or the like of the supported metal that occurs during the catalyst production process, or to ensure that the supported metal components are uniformly dispersed on the support particles.

[0028] However, catalyst preparation processes typically include processes for applying energy to transition metal-supported catalysts during preparation, such as by heating, through processes such as aging, drying, or calcination. For example, when a metal-supported catalyst using silica fine particles as a support is produced through a process such as calcination, polymerization between the support particles is promoted, and the physical strength of the final catalyst reaches a sufficient level. However, on the other hand, the specific surface area may decrease due to the aggregation and fusion of the supported metal as described above, and the desired catalytic performance may not be achieved. This is presumably because the energy-imparting process, such as calcination, promotes the polymerization of silanol groups between the silica fine particles, resulting in a decrease in the specific surface area of the support and further in a decrease in the specific surface area of the catalyst, which in turn leads to aggregation and fusion of the supported metal, resulting in the failure to achieve the desired catalytic performance.

[0029] When the carrier particles contain silica fine particles, the solid 29 The value of Q4 in the Si-NMR spectrum (Q4 is the peak area derived from Si(OSi)4) indicates that all bonds to a certain Si atom form siloxane bonds via O (oxygen atoms).Here, the higher the Q4 value, the more the polymerization reaction of the particles has progressed and is completed. On the other hand, Q3 (Q3 is the peak area derived from HO-Si(OSi)3) indicates the presence of an O (oxygen atom) that has not formed a siloxane bond with a certain Si atom, which indicates that the polymerization reaction of the particle has not been completed and that it is in a state where it is more reactive to the aforementioned energy application. The present inventors have found that when the value of Q4 / Q3 is within a specific range, the progress of the polymerization reaction of the zirconia-coated silica particles can be suppressed in the catalyst preparation step, and excellent catalytic performance is exhibited.

[0030] The peak area ratio Q4 / Q3 of the microparticles of the present invention is preferably 0.387 or more and 0.655 or less. A peak area ratio within this range can exhibit excellent catalytic performance due to the above-mentioned mechanism of action. If the peak area ratio Q4 / Q3 is less than 0.387, sufficient catalytic performance may not be achieved, possibly due to insufficient suppression of the polymerization reaction between zirconia-coated silica particles in the catalyst preparation process. On the other hand, if the peak area ratio Q4 / Q3 exceeds 0.655, sufficient catalytic performance may not be achieved due to insufficient catalyst strength, possibly due to insufficient polymerization reaction between zirconia-coated silica particles in the catalyst preparation process. It is more preferable that the peak area ratio Q4 / Q3 is 0.399 or more and 0.520 or less.

[0031] [Si 2P peak position in XPS measurement] The second chemical characteristic of the fine particles of the present invention relates to the Si2P peak position in XPS measurement. Specifically, the fine particles of the present invention preferably have an Si2P peak position in XPS measurement in the range of 103.37 to 103.59 eV. As mentioned above, in order to improve the performance of transition metal supported catalysts, it is necessary to suppress the growth of supported metal particles, and it is presumed that this requires the support particles to fix or stabilize the supported metal on their surface. It is presumed that the high electron density around the Si atoms promotes more electrical interaction between the silica particles and the supported metal, increasing the stability of the supported metal on the silica particles and resulting in excellent catalytic performance.

[0032] The Si 2P peak position in XPS measurements indicates the bond strength of the Si-O bond. The strength of this chemical bond is thought to be influenced by the elements located around the bond, for example, the Zr element close to the Si-O bond in Si-O-Zr. Since the electronegativity of Zr is lower than that of Si, it is presumed that the electron density around Si in the Si-O-Zr bond is higher than that of normal Si-O-Si. Furthermore, as shown in Examples 1 to 3 described below, the Si2P peak position also continuously decreases with increasing Zr content. This indicates that the Si-O-Zr bonds increase, as described above, i.e., Zr is continuously dissolved in SiO2. Furthermore, since the presence of crystalline Zr compounds such as ZrO2 is not confirmed by X-ray diffraction, it is inferred that an amorphous zirconium silicate layer is formed in Examples 1 to 3. In the fine particles of the present invention, the zirconium-containing silica layer is preferably made of zirconium silicate. The Si2P peak position of the fine particles of the present invention is preferably in the range of 103.37 to 103.59 eV. If the peak position is in this range, excellent catalytic performance can be exhibited due to the above-mentioned mechanism of action. If the peak position is less than 103.37, the Si-O bond strength of the silica fine particles is too low, and the reaction between the silica fine particles in the above-mentioned catalyst preparation process may proceed excessively, making it difficult to obtain sufficient catalytic performance. The peak position is more preferably 103.45 or more and 103.57 eV or less.

[0033] [Specific surface area] The specific surface area of the fine particles of the present invention correlates with the average particle size, but is usually 2 / g or more 900m 2 This specific surface area range is desirable because it allows for excellent catalytic performance with a practically used amount of supported metal. 2 If the specific surface area is less than 900 m / g, a large amount of supported metal may be required to obtain sufficient catalytic activity, which may not be cost-effective and is therefore undesirable. 2 If it exceeds 1 / g, it may lead to an increase in viscosity in the catalyst preparation step, and it may not be possible to obtain a metal-supported catalyst with the desired performance, which is undesirable. The specific surface area is preferably in the range of 200 to 500 m 2 / g range is recommended.

[0034] The specific surface area of the fine particles of the present invention is a value obtained by measurement using the following NaOH titration (Sears method). 1) Pass the sample through the cation exchange resin and confirm that the pH of the sample after passing through is 4 or less. 2) Measure the SiO2 concentration using the 1000℃ ignition method. 3) A sample equivalent to 1.5 g of SiO2 solids was placed in a beaker, transferred to a thermostatic reaction tank (25°C), and purified water was added to bring the liquid volume to 90 ml. (The following operations were carried out in a thermostatic reaction tank maintained at 25°C.) 4) Add 30g of sodium chloride, dilute with pure water to 150ml, and stir for 10 minutes. 5) Set a pH electrode and add 0.1 mol / L sodium hydroxide solution dropwise while stirring to adjust the pH to 4.0. 6) Titrate the sample adjusted to pH 4.0 with 0.1 mol / L sodium hydroxide solution, record the titer and pH value at four or more points in the pH range of 8.7 to 9.3, and create a calibration curve by setting the titer of 0.1 mol / L sodium hydroxide solution as X and the pH value at that time as Y. 7) Using the following formula (1), calculate the consumption amount V (ml) of 0.1 mol / L sodium hydroxide solution required to change the pH from 4.0 to 9.0 per 1.5 g of SiO2, and calculate the specific surface area [m 2 / g]. Equation (1): V=(A×f×100×1.5) / (W×C) Formula (2): SA=29.0V-28 The symbols in the formula have the following meanings: V = consumption volume (ml) of sodium hydroxide solution (0.1 mol / L), A: titration volume (mL) of 0.1 mol / L sodium hydroxide solution required per 1.5 g of SiO2 to bring the pH from 4.0 to 9.0, f: titer of 0.1 mol / L sodium hydroxide solution, W: sample volume (g), C: SiO2 concentration of the sample (%), SA: specific surface area of the microparticles

[0035] [Production method of the present invention] The production method of the present invention is a production method including the following steps 1, 2, and 3. Step 1: A step of mixing a zirconium salt of an inorganic acid with a silicic acid solution to obtain a mixed solution. Step 2: A step of adding the mixed solution obtained in the previous step to a silica fine particle dispersion to obtain a precursor solution in which the mass ratio of Zr to SiO2 is in the range of 100 ppm to 10,000 ppm. Step 3: A step of maintaining the precursor solution obtained in the previous step at 50 to 98°C to obtain a fine particle dispersion.

[0036] In the production method of the present invention, when the surfaces of silica fine particles are coated with zirconia, a mixed solution of a zirconium salt of an inorganic acid and a silicic acid solution is prepared and used. In this way, the compatibility between the soluble silicic acid component and zirconium ions at the molecular level can be improved, and the formation of a zirconium-containing silica layer (e.g., a zirconium silicate layer) can be further promoted.

[0037] As described above, in step 1, an aqueous solution of a zirconium salt of an inorganic acid and a silicic acid solution are mixed to prepare a mixed solution.

[0038] Examples of inorganic acids include sulfuric acid, hydrochloric acid, and nitric acid. The mixing ratio of the inorganic zirconium salt and the silicic acid solution is preferably a SiO2:Zr ratio of 100:0.01 to 100:20 by mass. This range ensures good compatibility between the silicic acid component and zirconium ions, facilitating the formation of a zirconium silicate layer in step 3. If the ratio of Zr to 100 parts by mass of SiO2 is less than 0.01, the amount of zirconium silicate layer formed in step 3 is insufficient, which is undesirable. Conversely, if the ratio of Zr to 100 parts by mass of SiO2 exceeds 20, some Zr may not form a zirconium silicate layer in step 3, resulting in an excess of Zr. A more preferable SiO2:Zr ratio (mass ratio) of 100:0.05 to 100:5 is recommended.

[0039] In step 2, the mixed solution obtained in the previous step is added to a silica fine particle dispersion to obtain a precursor solution. In step 2, by mixing Zr to SiO2 at a mixing ratio (mass ratio) in the range of 100 ppm to 10,000 ppm, the compatibility between the silicic acid component and zirconium ions is improved, resulting in a precursor solution suitable for promoting the formation of a zirconium silicate layer. Here, the mixing ratio (mass ratio) of Zr to SiO2 refers to the mixing ratio of Zr to SiO2 in the precursor solution obtained by adding a mixed solution (composed of a mixture of a zirconium salt of an inorganic acid and a silicic acid solution) to a silica microparticle dispersion. If the mixing ratio of Zr to SiO2 is less than 100 ppm, the amount of zirconium silicate layer formed in the subsequent step is insufficient, which is undesirable. Similarly, if the mixing ratio of Zr to SiO2 exceeds 10,000 ppm, Zr may be present that does not form a zirconium silicate layer in the subsequent step, possibly due to the excessive amount of Zr, resulting in an excess of Zr. The mixing ratio (mass ratio) of Zr to SiO2 is preferably recommended to be in the range of 500 to 5000 ppm.

[0040] In step 3, the precursor solution obtained in the previous step is kept at 50 to 98° C. to obtain a fine particle dispersion. This fine particle dispersion may be the dispersion of the present invention.

[0041] [Organic reaction catalysts] The catalyst of the present invention will now be described. The catalyst of the present invention is a catalyst for organic reactions in which transition metal particles are supported on the fine particles of the present invention. The catalyst of the present invention is a calcined product obtained by drying the dispersion of the present invention containing the transition metal particles and calcining the dried dispersion at a temperature of about 150 to 700°C.

[0042] The average particle size of the catalyst of the present invention is a value obtained by dispersing the catalyst of the present invention in a dispersion medium such as water and measuring the dispersion using a measuring device based on a laser diffraction scattering method (e.g., LA-950 manufactured by HORIBA). If the average particle size of the catalyst of the present invention is in the range of 5 to 200 μm, the catalyst has good fluidity when used in a fluidized bed catalytic reaction, and loss due to scattering can be suppressed, which is preferable. If the average particle size of the catalyst is less than 5 μm, significant loss due to scattering occurs, which is undesirable, whereas if the average particle size of the catalyst is more than 200 μm, the fluidity of the catalyst becomes poor, and sufficient catalytic activity cannot be obtained, which is undesirable.

[0043] The transition metal particles contained in the catalyst of the present invention, which will be described later, may be a transition metal compound. That is, the transition metal particles are a concept that includes transition metal compound particles. The types of transition metals (supported metals) and transition metal compounds may be similar.

[0044] When the catalyst of the present invention has transition metal particles and a transition metal compound, the mass ratio of the fine particles of the present invention to the total of the transition metal particles and the transition metal compound particles (in metal equivalent) is not particularly limited and is selected appropriately depending on the application of the catalyst and the type of transition metal.

[0045] <Method of producing the catalyst of the present invention> The catalyst of the present invention can be produced, for example, as follows. First, a solution or suspension of a transition metal compound containing the transition metal to be supported on the fine particles of the present invention, which serve as a carrier, is prepared. The solvent may be a ready-made product or a prepared product. Water is generally used as the solvent for the solution or suspension of the transition metal compound, but organic solvents such as alcohols, esters, ethers, and carboxylic acids may also be used. There are no particular limitations on the method for preparing a solution or suspension of a transition metal compound, and it is sufficient to prepare a predetermined amount of raw materials according to the desired composition and mix them with a solvent such as water. When water is used as the solvent, if the transition metal raw material is poorly soluble in water, it may be dissolved using an acid or alkali, or by heating to about 50 to 90°C. The solid content of the solution or suspension of the transition metal compound is not limited as long as it does not interfere with mixing with the dispersion of the present invention, but a range of 5 to 30 mass % is usually recommended.

[0046] Next, the dispersion of the present invention and the solution or suspension of the transition metal compound are mixed to prepare a mixed solution. The mixing method is not particularly limited, and examples thereof include known methods such as using a mixer or a stirrer. The solution or suspension of the transition metal compound may be added to the dispersion of the present invention and mixed, or vice versa. When mixing, an acid or alkali may be added as needed, and the mixture may be heated to about 30°C to 90°C.

[0047] After preparing the mixture, the mixture is dried to prepare a dried product. A known drying method can be used. Specifically, a vacuum drying method using a rotary evaporator, a heat treatment method on an evaporating dish, or a spray drying method using a spray dryer may be used. The dried product is then subjected to a heat treatment. The heat treatment method can be selected arbitrarily depending on the properties and scale of the dried product, but heat treatment on an evaporating dish or heat treatment in a heating furnace such as a rotary furnace or a fluidized bed calciner is common. A combination of these heat treatment procedures may also be used. The heat treatment may be performed in the atmosphere, or in a gas such as hydrogen, nitrogen, or argon, or in a vacuum. The heating temperature varies depending on the type of metal, but is typically in the range of 300 to 700°C. The heating time varies depending on the type of metal and the amount of metal supported, and is not limited, but is typically 10 minutes to 10 hours.

[0048] Examples of transition metals contained in the catalyst of the present invention include Pd, Cu, Pt, Au, Ag, Ru, Ni, W, V, Mo, Fe, Ce, etc. Examples of transition metal compounds include compounds containing at least one of the above supported metals. [Example]

[0049] Examples of the present invention will be described below. The methods of measurement and calculation used in the examples and comparative examples are as follows.

[0050] <Average particle diameter (D1)> The average particle diameter (D1) of the microparticles contained in the microparticle dispersion of the present invention means a value obtained by measurement by dynamic light scattering. Specifically, a microparticle dispersion with a solid content of 1% by mass was prepared, and an aqueous ammonia solution (concentration: 28% by mass) was added to adjust the ammonia concentration of the dispersion medium to 0.58% by mass, and the average particle diameter (D1) was measured using a particle size distribution analyzer ("nanoSAQLA" manufactured by Otsuka Electronics Co., Ltd.).

[0051] <Minor diameter / major diameter ratio> The minor axis / major axis ratio of the fine particles contained in the fine particle dispersion of the present invention means a value measured by an image analysis method using a scanning electron microscope (SEM) as described below. First, a scanning electron microscope (SEM) is used to photograph an arbitrary location of microparticles collected from a microparticle dispersion at 100,000x magnification. Then, for all microparticles contained in the photographed image, the point on the image where the diameter is longest is taken as the major axis, and the length of that major axis is taken as the major diameter (DL). A point is then determined on the major axis that bisects the major axis, and two points where a line perpendicular to this intersects with the outer edge of the particle are found. The length between these two points is measured and taken as the minor diameter (DS). The ratio of these (minor diameter / major diameter ratio) is then calculated. In this way, this ratio is calculated for each microparticle, and a simple average is calculated, and the resulting value is taken as the minor diameter / major diameter ratio of the microparticle.

[0052] After determining the minor axis and major axis of all the particles included in the image as described above, the average value of these was taken as the particle diameter of the particle. The particle diameters of all the particles were then simply averaged, and the obtained value was taken as the average particle diameter by image analysis.

[0053] <Solid 29 Si-NMR spectrum solid 29For the measurement of the Si CPMAS NMR spectrum, a VNMRS-600 (14.1 T, 1H resonance frequency: 600 MHz) manufactured by Agilent was used. The measurement sample was pulverized using a mortar and filled into a 5 mm solid NMR sample tube so as to be uniform, and then rotated at 6 kHz at the magic angle (54.7°) with respect to the external magnetic field. The 29Si resonance frequency at this time was 119.2 MHz, the 1H 90° pulse width was 5.0 μs, the contact time was 7 ms, the waiting time after FID was 5 s, and the number of integrations of FID was about 10,000 times. The peak of polydimethylsilane at -34.44 ppm was used as the secondary standard of chemical shift, and the obtained spectrum was approximated with a Gaussian function using Origin for waveform separation. As described above, 29 the Si-NMR spectrum was measured, and from this spectrum, the peak intensities and peak areas of Q3 and Q4 were read. Then, the value of [(Q4) / (Q3)] was calculated for the peak area of Q4 and the peak area of Q3.

[0054] <XPS (X-ray Photoelectron Spectroscopy)> The fine particle dispersion of the present invention was heated at 110 °C to evaporate the dispersion medium (water) to obtain powdery fine particles. 0.1 g of the powder was used as a sample, and an O1s shell binding energy spectrum diagram was obtained by measuring under the conditions of X-ray source AlKα ray, voltage 15 kV, and current 5 mA. The obtained spectrum was corrected with C1s (284.8 eV) to determine the Si2P peak position. In addition, KRATOS ULTRA2 manufactured by Shimadzu Corporation was used as the measuring device.

[0055] <Confirmation of the presence of crystalline zirconium compounds> It was confirmed by X-ray diffraction whether the fine particles contained in the dispersion of the present invention contained a crystalline zirconium compound. Specifically, the following measurements were performed. After drying the microparticle dispersion of the present invention, the microparticles are pulverized in a mortar and mortar, and when an X-ray diffraction pattern is obtained using, for example, a conventionally known X-ray diffractometer (e.g., RINT1400 manufactured by Rigaku Denki Co., Ltd.), no peaks corresponding to tetragonal zirconium dioxide are observed, which confirms that the microparticles contained in the dispersion of the present invention do not contain a crystalline zirconium compound.

[0056] <Analysis of impurities> [Atomic absorption spectroscopy] In the present invention, the Na and K contents in the silicic acid solution used as the raw material and the Na content of the microparticles contained in the microparticle dispersion were measured by atomic absorption spectroscopy. First, approximately 1 g of sample (20% solids by mass) was placed on a platinum dish. 3 ml of phosphoric acid, 5 ml of nitric acid, and 10 ml of hydrofluoric acid were added, and the mixture was heated on a sand bath. Once dried, a small amount of water and 50 ml of nitric acid were added to dissolve the mixture, which was then placed in a 100 ml measuring flask and water was added to make the total volume 100 ml. The Na and K contents of this solution were measured using an atomic absorption spectroscopy analyzer (e.g., Hitachi, Ltd., Z-2310).

[0057] <SiO2 and Zr Contents in the Fine Particles Contained in the Dispersion of the Present Invention> The Zr content of the fine particles contained in the dispersion of the present invention is a value obtained by measurement using ICP-MS (inductively coupled plasma atomic emission spectroscopy mass spectrometry). Specifically, the dispersion of the present invention is heated and dried, then the silica content is dissolved with hydrofluoric acid, heated to remove the hydrofluoric acid, and then pure water is added as necessary, and the resulting solution is measured using an ICP inductively coupled plasma atomic emission spectroscopy mass spectrometer (e.g., ICPM-8500 manufactured by Shimadzu Corporation). In addition, SiO2 was determined by subtracting the metal content, including Zr, from the solid content determined by the 1000°C scorching method described below.

[0058] Then, the Na content relative to the SiO2 content and the Zr content relative to the SiO2 content were calculated.

[0059] <Method for measuring the NH3 concentration contained in the dispersion of the present invention> The NH3 concentration in the dispersion of the present invention was measured as follows. 1) Collect 1 to 2 g of the sample and put it into a Kjeldahl flask. 2) Add 10 ml of 20% sodium hydroxide solution and set up a distillation apparatus. 3) Add 10 ml of 0.05 mol sulfuric acid to a 500 ml conical beaker as a receiver, make it 100 ml with pure water, and then add methyl red indicator. 4) Heat the distillation flask with a mantle heater and perform distillation until the effluent is about 200 ml. 5) Titrate the effluent with 0.1 mol sodium hydroxide solution to determine the NH3 concentration.

[0060] <Solid content concentration> A desired amount of the dispersion of the present invention was sampled, heated at 1000 °C (ignition loss at 1000 °C), and then the mass was measured, and the solid content concentration was measured from the obtained value.

[0061] <pH measurement> In the examples, the pH of the liquid was measured as follows. Prepare a cell containing 50 ml of the sample, and insert the glass electrode of a pH meter (manufactured by Horiba, Ltd., F22) that has been calibrated with standard solutions of pH 4.0, pH 7.0, and pH 9.0 in a thermostatic bath maintained at a temperature of 25 °C, and measure the pH value.

[0062] <Preparation of ethylene decomposition catalyst> To 50 g of the microparticle dispersion (SiO2 concentration 5 wt%) prepared in each Example and Comparative Example, an aqueous solution containing metal sources (Au: [HAuCl4·4H2O aq.], Rh: [RhCl3·3H2O aq.], Pd: [PdCl2 aq.]) was added dropwise to achieve a metal loading of 1.0 wt%, and the resulting solution was stirred overnight at room temperature. The solvent was removed by heating to 60 °C using an evaporator, and the resulting powder was vacuum dried at 60 °C for 16–18 hours. A reduction treatment was then performed at 200 °C for 2 hours while flowing hydrogen gas at 30 mL / min to obtain an ethylene decomposition catalyst as an organic reaction catalyst in which the metals (Au, Rh, and Pd) were supported on the support. In Comparative Example 1, the organic reaction catalyst was prepared using 50 g of silica sol (SiO2 concentration 5 wt%) instead of 50 g of the microparticle dispersion.

[0063] <Measurement of metal loading in organic reaction catalysts> The amount of transition metals supported in the catalyst for organic reactions (e.g., the amount of Au, Rh, and Pd supported) was measured using ICP-MS (inductively coupled plasma atomic emission spectroscopy mass spectrometry). Specifically, the catalyst for organic reactions was heated and dried, and then the silica content was dissolved in hydrofluoric acid. After heating to remove the hydrofluoric acid, pure water was added as needed, and the resulting solution was measured using an ICP inductively coupled plasma atomic emission spectrometry mass spectrometer (e.g., ICPM-8500 manufactured by Shimadzu Corporation).

[0064] <Catalyst evaluation> Using the catalysts for organic reactions prepared in each Example and Comparative Example, the ethylene decomposition rate was measured by the following method. The results are shown in Table 2. (1) Extraction of chlorine from the catalyst: 0.5 g of the catalyst was placed in a beaker, 50 ml of pure water was added, and the mixture was subjected to ultrasonic treatment for 5 minutes using an ultrasonic device. (2) Measurement of chlorine content by ion chromatography: The above extracted aqueous solution was diluted 25 times with pure water, and the concentration was measured using an ion chromatograph manufactured by Shimadzu Corporation, and the column was an IC-A3 manufactured by Shimadzu Corporation. (3) Conditions for evaluating ethylene decomposition: 1 g of catalyst was filled into a scent bag, ethylene and air were mixed, and 2600 ml of 100 ppm ethylene mixed gas was poured into the scent bag and left at 4°C for 20 hours. The ethylene concentration was measured by gas chromatography, and the ethylene decomposition rate was calculated using the following formula and evaluated according to the following criteria. Ethylene decomposition rate (%) = [(initial ethylene gas concentration) - (ethylene gas concentration after 20 hours)] / (initial ethylene gas concentration) x 100 [Criteria] An ethylene decomposition rate of 80% or more was considered to be pass (marked with a circle). Ethylene decomposition rate 80% or more: Yes Ethylene decomposition rate less than 80%: △

[0065] [Synthesis Example 1] (Preparation of silicic acid solution) 7,000 g of an aqueous solution of alkaline silicate, prepared by diluting aqueous glass (JIS K1408 sodium silicate No. 3) to a silica concentration of 7% by mass, was passed through an ultrafiltration module (SIP-1013, manufactured by Asahi Kasei Corporation), and the filtrate was collected to obtain purified aqueous glass. Pure water was added to the purified aqueous glass so that the silica concentration was 5%. 6,500 g of this aqueous glass with a silica concentration of 5% was then passed through 2.2 L of strong acid cation exchange resin SK1BH (manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.1, yielding 6,650 g of silicate solution. The silica concentration of the resulting silicate solution was 4.7% by mass.

[0066] [Synthesis Example 2] (High Purification Treatment of Silica Solution) 6,650 g of the above silicic acid solution was again passed through 0.4 L of strongly acidic cation exchange resin SK1BH (manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.1, and then passed through 0.4 L of strongly basic ion exchange resin SANUPC (manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.1, thereby obtaining a high-purity silicic acid solution with a silica concentration of 4.4%. The impurity content of the resulting silicic acid solution was measured by the following method. 1 g of the high-purity silicic acid solution was heated on a sand bath. Once it had dried, a small amount of water and 50 ml of nitric acid were added to dissolve it, and the solution was placed in a 100 ml measuring flask. Water was added to make the total volume 100 ml. The Na and K contents of this solution were measured using an atomic absorption spectrophotometer (e.g., Hitachi, Ltd., Z-2310). Acetone was added to 20 g of the high-purity silicic acid solution to make a total volume of 100 ml, and 5 ml of acetic acid and 4 ml of 0.001 M sodium chloride solution were added to this solution, and Cl analysis was performed using a potentiometric titration method (potentiometric titrator AT-610 manufactured by Kyoto Electronics Co., Ltd.) with a 0.002 M silver nitrate solution. Separately, as a blank measurement, 5 ml of acetic acid and 4 ml of 0.001 M sodium chloride solution were added to 100 ml of acetone, and titrated with 0.002 M silver nitrate solution to determine the titer. This was subtracted from the titer obtained using the sample to determine the titer of the sample. The results were as follows: Na was less than 50 ppb, K was less than 50 ppb, and Cl was less than 1 ppm.

[0067] [Synthesis Example 3] (Preparation of silica sol) 165.3 g of pure water and 55.3 g of 15% aqueous ammonia were added to 427.0 g of the high-purity silicic acid solution obtained in Synthesis Example 2 and stirred at room temperature for 10 minutes. The pH at this point was 10.7. The pH-adjusted silicic acid solution was heated to 87°C and maintained at this temperature for 30 minutes. Separately, 883.1 g of a high-purity silicic acid solution with a concentration of 4.4% was prepared by the same production method as in Synthesis Examples 1 and 2. 883.1 g of this high-purity silicic acid solution and 73.0 g of 1.9% aqueous ammonia were simultaneously added to the silicic acid solution over 9.5 hours while maintaining the temperature at 87°C. After the addition, the solution was maintained at 87°C for another hour, and then cooled to room temperature to obtain a silica sol (silica concentration 3.6% by mass). The resulting silica sol had an average particle size of 15 nm as measured by dynamic light scattering, using an ELSZ-1000 manufactured by Otsuka Electronics Co., Ltd.

[0068] The obtained silica sol was concentrated to a concentration of 12% by mass using an ultrafiltration membrane (SIP-1013, manufactured by Asahi Kasei Corporation). 1 g of this silica sol was heated on a sand bath and dried, and then dissolved in a small amount of water and 50 ml of nitric acid. The solution was placed in a 100 ml measuring flask and water was added to make 100 ml. The amount of Na contained in the silica sol was measured using an atomic absorption spectrophotometer (e.g., Z-2310, manufactured by Hitachi, Ltd.) as a sample. The result showed that the Na content was 50 ppb or less.

[0069] [Example 1] <Preparation of fine particle dispersion> [Preparation of additive solution] Zirconium sulfate was dissolved in pure water to prepare 1.29 g of an aqueous zirconium sulfate solution (Zr concentration: 5% by mass). This aqueous zirconium sulfate solution was mixed with 55.71 g of the high-purity silicic acid solution (silica concentration: 4.4% by mass) prepared in Synthesis Example 2 to obtain a mixed solution of the aqueous zirconium sulfate solution and the high-purity silicic acid solution.

[0070] [Formation of zirconium silicate layer] 57.0 g of this mixed solution was added to 992 g of the silica sol (silica concentration 12% by mass) prepared in Synthesis Example 3 over 60 minutes with stirring. After the addition was completed, stirring was continued for an additional 30 minutes to obtain a precursor solution. The Zr / SiO2 of the precursor solution was 517 ppm. After the stirring was completed, the precursor solution was heated to 70°C, held at 70°C for 60 minutes, and then cooled to room temperature to obtain a microparticle dispersion (solid concentration 11.6% by mass) in which microparticles including coated silica particles (silica particles having a zirconium-containing silica layer) were dispersed in a dispersion medium. Note that no phenomena such as clouding of the solution, generation of gel-like material, or generation of sediment were observed at each stage, such as when the silica sol was added to the mixed solution, when the precursor solution was held at 70°C, or when the precursor solution was cooled from 70°C to room temperature.

[0071] The resulting fine particle dispersion was used to prepare a catalyst for organic reactions by the method described above, and the ethylene decomposition rate was measured by the method described above. The results are shown in Table 2.

[0072] [Example 2] <Preparation of fine particle dispersion> [Preparation of additive solution] Zirconium sulfate was dissolved in pure water to prepare 3.49 g of an aqueous zirconium sulfate solution (Zr concentration: 5% by mass). This aqueous zirconium sulfate solution was mixed with 150.1 g of the high-purity silicic acid solution (silica concentration: 4.4% by mass) prepared in Synthesis Example 2 to obtain a mixed solution of the aqueous zirconium sulfate solution and the high-purity silicic acid solution.

[0073] [Formation of zirconium silicate layer] 153.59 g of this mixed solution was added to 992 g of the silica sol (silica concentration 12% by mass) prepared in Synthesis Example 3 over 60 minutes with stirring. After completion of the addition, stirring was continued for an additional 30 minutes to obtain a precursor solution. The Zr / SiO2 of the precursor solution was 1364 ppm. After completion of the stirring, the precursor solution was heated to 70°C, held at 70°C for 60 minutes, and then cooled to room temperature to obtain a microparticle dispersion (solid concentration 11.0% by mass) in which microparticles including coated silica particles (silica particles having a zirconium-containing silica layer) were dispersed in a dispersion medium. Note that no phenomena such as clouding of the solution, generation of gel-like material, or generation of sediment were observed at each stage, such as when the silica sol was added to the mixed solution, when the precursor solution was held at 70°C, or when the precursor solution was cooled from 70°C to room temperature.

[0074] The resulting fine particle dispersion was used to prepare a catalyst for organic reactions by the method described above, and the ethylene decomposition rate was measured by the method described above. The results are shown in Table 2.

[0075] [Example 3] <Preparation of fine particle dispersion> [Preparation of additive solution] Zirconium sulfate was dissolved in pure water to prepare 7.76 g of an aqueous zirconium sulfate solution (Zr concentration: 5% by mass). This aqueous zirconium sulfate solution was mixed with 333.7 g of the high-purity silicic acid solution (silica concentration: 4.4% by mass) prepared in Synthesis Example 2 to obtain a mixed solution of the aqueous zirconium sulfate solution and the high-purity silicic acid solution.

[0076] [Formation of zirconium silicate layer] 341.5 g of this mixed solution was added to 992 g of the silica sol (silica concentration 12% by mass) prepared in Synthesis Example 3 over 60 minutes with stirring. After the addition was completed, stirring was continued for an additional 30 minutes to obtain a precursor solution. The Zr / SiO2 of the precursor solution was 2900 ppm. After the stirring was completed, the precursor solution was heated to 70°C, held at 70°C for 60 minutes, and then cooled to room temperature to obtain a microparticle dispersion (solid concentration 10.0% by mass) in which microparticles including coated silica particles (silica particles having a zirconium-containing silica layer) were dispersed in a dispersion medium. Note that no phenomena such as clouding of the solution, generation of gel-like material, or generation of sediment were observed at each stage, such as when the silica sol was added to the mixed solution, when the precursor solution was held at 70°C, or when the precursor solution was cooled from 70°C to room temperature.

[0077] The resulting fine particle dispersion was used to prepare a catalyst for organic reactions by the method described above, and the ethylene decomposition rate was measured by the method described above. The results are shown in Table 2.

[0078] [Comparative Example 1] A catalyst for organic reactions was prepared by the method described above using the silica sol obtained in Synthesis Example 3, and then the ethylene decomposition rate was measured by the method described above. The results are shown in Table 2.

[0079] Comparative Example 2 <Preparation of fine particle dispersion> [Preparation of additive solution] Zirconium sulfate was dissolved in pure water to prepare 7.8 g of an aqueous zirconium sulfate solution (Zr concentration: 5% by mass).

[0080] [Formation of zirconium silicate layer] 7.76 g of an aqueous zirconium sulfate solution was added to 992 g of the silica sol (silica concentration 12% by mass) prepared in Synthesis Example 3 over 60 minutes with stirring. After the addition was completed, stirring was continued for an additional 30 minutes to obtain a precursor solution. The Zr / SiO2 of the precursor solution was 3277 ppm. After the stirring was completed, the precursor solution was heated to 70°C, held at 70°C for 60 minutes, and then cooled to room temperature to obtain a zirconia-coated silica microparticle dispersion (solid concentration 12.0% by mass). The resulting zirconia-coated silica fine particle dispersion was cloudy and contained gel-like sediment.

[0081] [Table 1]

[0082] [Table 2]

Claims

1. A fine particle dispersion in which fine particles including silica particles with a coating layer, which are silica particles having a zirconium-containing silica layer, are dispersed in a dispersion medium, wherein the fine particles have the following characteristics 1) to 4): 1) Average particle size (D1) measured by dynamic light scattering method is in the range of 10 to 100 nm 2) The ratio of minor axis to major axis measured by image analysis is in the range of 0.75 to 1.0 3) Solid 29 Q by Si-NMR 4 / Q 3 The ratio is in the range of 0.387 to 0.

655. 4) The Si2P peak position in the XPS measurement is in the range of 103.37 to 103.59 eV

2. 2. The fine particle dispersion according to claim 1, wherein the zirconium-containing silica layer comprises zirconium silicate.

3. The fine particles include silica particles with a coating layer, which are silica particles having a zirconium-containing silica layer, and have the following characteristics 1) to 4), and are used as a catalyst support. 1) Average particle size (D1) measured by dynamic light scattering method is in the range of 10 to 100 nm 2) The ratio of minor axis to major axis measured by image analysis is in the range of 0.75 to 1.0 3) Solid 29 Q by Si-NMR 4 / Q 3 The ratio is in the range of 0.387 to 0.

655. 4) The Si2P peak position in the XPS measurement is in the range of 103.37 to 103.59 eV

4. SiO 2 4. The microparticles according to claim 3, wherein the Na content relative to the total content is less than 100 ppm.

5. 5. A catalyst for organic reactions, comprising the fine particles according to claim 3 or 4 carrying transition metal particles.

6. A method for producing a microparticle dispersion, comprising the following steps 1, 2, and 3, wherein a microparticle dispersion is obtained in which microparticles including silica particles with a coating layer, which are silica particles having a zirconium-containing silica layer, are dispersed in a dispersion medium. Step 1: A step of mixing a zirconium salt of an inorganic acid and a silicic acid solution to obtain a mixed solution. Step 2: The mixed solution obtained in the previous step is added to a silica fine particle dispersion liquid, and Zr SiO 2 obtaining a precursor solution having a mass ratio of 100 ppm to 10,000 ppm. Step 3: A step of maintaining the precursor solution obtained in the previous step at 50 to 98° C. to obtain the fine particle dispersion.

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