Method for producing catalyst composition

Abstract

To provide a method for producing a catalyst composition having high CO2 conversion activity.SOLUTION: There is provided a method for producing a catalyst composition which comprises: a step (1) of preparing Ti-based oxide fine particles having a Ti content of 90 mass% or more in terms of TiO2 and a median diameter D50 of 1 nm or more and 500 nm or less, non-Ti-based metal oxide particles having a Ti content of 1 mass% or less in terms of TiO2 and an Ru source as raw materials; and a step (2) of supporting Ti-based oxide fine particles and Ru particles on non-Ti-based metal oxide particles using the raw materials, wherein the Ti-based oxide fine particles in step (1) exhibit a rutile-type crystal structure and the mass of the Ti-based oxide fine particles in the step (1) is 2 mass% or more and 8 mass% or less based on the total mass of the mass of the Ti-based oxide fine particles in step (1) and the mass of the non-Ti-based metal oxide particles in step (1)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for preparing a catalyst composition. [Background technology]

[0002] In recent years, research has been conducted into recovering the greenhouse gas CO2 (carbon dioxide) and reacting it with H2 (hydrogen) to obtain useful chemical raw materials such as CO (carbon monoxide). For example, the reaction shown in the following formula (a1) is known. CO2+H2→CO+H2O (a1)

[0003] Known catalysts for converting CO2 to CO include those containing Ru or TiO2. Patent Document 1 describes a shift catalyst used in a so-called shift reaction in which CO is reacted with H2O (water) to generate hydrogen gas and simultaneously convert CO to CO2. The shift catalyst is prepared by hydrolyzing a titanium alkoxide in an organic solvent containing an oxide other than titanium oxide and a titanium alkoxide, and using an inorganic material in which the titanium oxide is supported on the oxide other than titanium oxide as a support. Patent Document 2 describes a method for producing a synthesis gas containing hydrogen and carbon monoxide, in which hydrocarbons are reformed with carbon dioxide in the presence of a reforming catalyst comprising a carrier carrying at least one selected from the group consisting of ruthenium and ruthenium compounds, and silica. Patent Document 3 describes a method for producing a catalyst for removing carbon monoxide in a hydrogen-containing gas, which comprises absorbing a mixed aqueous solution of ruthenium nitrate and nitric acid onto a metal oxide support, followed by drying and reduction treatment, characterized in that the mixed aqueous solution has a ruthenium concentration in the range of 0.12 to 90 g / L, and when the ruthenium concentration of the mixed aqueous solution is adjusted to 0.5 g / L, the absorbance at a wavelength of 600 nm of the mixed aqueous solution is in the range of 2.0 to 4.0. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-141801 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-241122 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-194615 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Documents 1 to 3 describe catalysts that convert CO to CO2 and catalysts that convert CO2 to CO, but there is a demand for catalysts that have higher CO2 conversion activity (that can increase the CO production intensity) than these conventional technologies.

[0006] It is therefore an object of the present invention to provide a method for preparing a catalyst composition that is highly active for CO2 conversion. [Means for solving the problem]

[0007] The gist of the present invention is as follows.

[0008] [1] Ti-based oxide fine particles having a TiO2-equivalent content of 90 mass% or more and a median diameter D50 of 1 nm or more and 500 nm or less; Non-Ti-based metal oxide particles having a Ti content of 1% by mass or less in terms of TiO2; (1) preparing a Ru source as a raw material; and a step (2) of supporting the Ti-based oxide fine particles and Ru particles on the non-Ti-based metal oxide particles using the raw material; 1. A method for producing a catalyst composition comprising: The Ti-based oxide fine particles in the step (1) exhibit a rutile crystal structure, The method for producing a catalyst composition, wherein the mass of the Ti-based oxide microparticles in step (1) is 2% by mass or more and 8% by mass or less relative to the total mass of the Ti-based oxide microparticles in step (1) and the non-Ti-based metal oxide particles in step (1). [2] The method for producing a catalyst composition according to [1], wherein the step (2) includes the following steps (2-1) and (2-2): Step (2-1): A step of supporting the Ti-based oxide fine particles on the non-Ti-based metal oxide particles to obtain supported particles. Step (2-2): A step of supporting the Ru particles on the support particles [3] The method for producing a catalyst composition according to [1] or [2], wherein the non-Ti-based metal oxide particles have a median diameter D50 of 0.5 μm or more and 500 μm or less. [4] The method for producing a catalyst composition according to any one of [1] to [3], wherein the non-Ti-based metal oxide particles contain at least one selected from the group consisting of oxides of Ce element and oxides of Al element. [5] The method for producing a catalyst composition according to any one of [1] to [4], wherein the non-Ti-based metal oxide particles contain an oxide of Ce element. [6] The method for producing a catalyst composition according to any one of [1] to [5], wherein the catalyst composition is a catalyst composition for a reaction between CO2 and H2. [Effects of the Invention]

[0009] According to the present invention, a method for producing a catalyst composition having high activity for CO2 conversion can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail.

[0011] [Method of producing catalyst composition] The method for producing the catalyst composition of the present invention (also referred to as the "production method of the present invention") is as follows: Ti-based oxide fine particles having a TiO2-equivalent content of 90 mass% or more and a median diameter D50 of 1 nm or more and 500 nm or less; Non-Ti-based metal oxide particles having a Ti content of 1% by mass or less in terms of TiO2; (1) preparing a Ru source as a raw material; and a step (2) of supporting the Ti-based oxide fine particles and Ru particles on the non-Ti-based metal oxide particles using the raw material; 1. A method for producing a catalyst composition comprising: The Ti-based oxide fine particles in the step (1) exhibit a rutile crystal structure, The method for producing a catalyst composition is such that the mass of the Ti-based oxide microparticles in step (1) is 2% by mass or more and 8% by mass or less relative to the total mass of the Ti-based oxide microparticles in step (1) and the non-Ti-based metal oxide particles in step (1).

[0012] The production method of the present invention has the effect of being able to obtain a catalyst composition with high CO conversion activity. Although the mechanism by which the present invention achieves the above effect is not completely clear, the inventors speculate as follows. However, the present invention is not limited in any way by the speculated mechanism below. The catalyst composition produced by the production method of the present invention (also referred to as the "catalyst composition of the present invention") is made from non-Ti-based metal oxide particles, Ti-based oxide fine particles exhibiting a rutile crystal structure, and a Ru source as raw materials. TiO2 with a rutile crystal structure (also referred to as "rutile TiO2") is known to be more chemically stable than TiO2 with an anatase crystal structure (also referred to as "anatase TiO2"). Furthermore, as explained below, rutile TiO2 is thought to have advantages not found in anatase TiO2. In catalysts in which catalytically active components are supported on a carrier, the catalytically active component particles can move and agglomerate on the carrier, resulting in a decrease in active sites. The catalytically active component, Ru, is usually present as RuO2 at the time of catalyst production. Because RuO2 has a rutile crystal structure, it strongly interacts with rutile-type TiO2, which has a similar crystal structure, which is thought to suppress the movement of catalytically active component particles and the accompanying agglomeration, thereby preventing a decrease in active sites. However, if the support contains a large amount of TiO2, if a large amount of TiO2 is supported on the support, or if the particle size of the supported TiO2 is large, RuO2 may diffuse deep into the support particles or TiO2 particles, where it is less likely to come into contact with the gas, and may no longer contribute to the catalytic reaction. Therefore, the production method of the present invention uses non-Ti-based metal oxide particles having a Ti content of 1% by mass or less in terms of TiO2, Ti-based oxide fine particles having a median diameter D50 of 1 nm or more and 500 nm or less, and a Ru source as raw materials, and the content of the Ti-based oxide fine particles is 2% by mass or more and 8% by mass or less of the total mass of the non-Ti-based metal oxide particles and the Ti-based oxide fine particles, and by supporting the Ti-based oxide fine particles and Ru particles on the non-Ti-based metal oxide particles, Ru can efficiently contribute to the catalytic reaction. As a result, it is believed that the catalyst composition of the present invention has high activity for CO2 conversion.

[0013] (Process (1)) Step (1) of the production method of the present invention will be described. Step (1) is a step of preparing, as raw materials, Ti-based oxide microparticles having a Ti content of 90% by mass or more in terms of TiO2 and a median diameter D50 of 1 nm or more and 500 nm or less, non-Ti-based metal oxide particles having a Ti content of 1% by mass or less in terms of TiO2, and a Ru source.

[0014] <Non-Ti metal oxide particles> The non-Ti-based metal oxide particles, which are the raw material in the method for producing the catalyst composition of the present invention, will now be described. The non-Ti-based metal oxide particles function as a support for supporting at least one of Ti-based oxide fine particles and Ru particles. The non-Ti-based metal oxide particles have a Ti content of 1% by mass or less, calculated as TiO2, relative to the mass of the non-Ti-based metal oxide particles. Note that an embodiment in which the non-Ti-based metal oxide particles do not contain Ti is also encompassed by "a Ti content of 1% by mass or less, calculated as TiO2, relative to the mass of the non-Ti-based metal oxide particles." When the non-Ti-based metal oxide particles contain Ti as TiO2, the crystal structure of the TiO2 contained in the non-Ti-based metal oxide particles is not limited, and may be either anatase type or rutile type. The content of Ti contained in the non-Ti-based metal oxide particles in terms of TiO2 is 1 mass% or less, preferably 0.5 mass% or less, and more preferably 0 mass% or less (i.e., the non-Ti-based metal oxide particles do not contain Ti), relative to the mass of the non-Ti-based metal oxide particles.

[0015] The non-Ti-based metal oxide particles are not particularly limited as long as they are metal oxide particles that can support at least one of Ti-based oxide fine particles and Ru particles, but preferably contain at least one selected from the group consisting of Ce (cerium), Al (aluminum), Zr (zirconium), and Si (silicon), more preferably contain at least one selected from the group consisting of Ce and Al, and even more preferably contain Ce. Ce oxide (CeO2) is a basic oxide that is excellent at adsorbing CO2, an acidic gas, and is therefore thought to increase the concentration of reactants near catalytically active species and promote the reaction. The non-Ti-based metal oxide particles preferably contain at least one element selected from the group consisting of Ce and Al (preferably an oxide of Ce), in an amount of 50 mass% or more, more preferably 70 mass% or more, and even more preferably 90 mass% or more, calculated as oxide, relative to the mass of the non-Ti-based metal oxide particles. The type and content of elements contained in non-Ti-based metal oxide particles can be determined by standard methods such as inductively coupled plasma atomic emission spectroscopy (ICP-AES). When calculating the content (mass%), Ru is assumed to be in a metallic state, and other metal elements are assumed to be in an oxide state. The specific oxide forms of each element are as follows: Ti oxide is TiO2, Ce oxide is CeO2, Al oxide is Al2O3, Zr oxide is ZrO2, and Si oxide is SiO2.

[0016] The median diameter D50 of the non-Ti-based metal oxide particles in step (1) (also referred to as "at the raw material stage") is preferably 0.5 μm or more and 500 μm or less, more preferably 1 μm or more and 300 μm or less, and even more preferably 3 μm or more and 100 μm or less. The median diameter D50 of the non-Ti-based metal oxide particles means the particle size at which the cumulative volume is 50% in the volume-based particle size distribution of the non-Ti-based metal oxide particles measured by dynamic light scattering. In the catalyst composition of the present invention, when Ru particles are supported on non-Ti-based metal oxide particles, it is preferable that the median diameter D50 of the non-Ti-based metal oxide particles is 0.5 μm or more, since the distance between the Ru particles is large and aggregation between the Ru particles is easily suppressed.Furthermore, it is preferable that the median diameter D50 of the non-Ti-based metal oxide particles is 500 μm or less, since the handleability of the catalyst composition is improved. The volume-based particle size distribution of non-Ti-based metal oxide particles measured by dynamic light scattering can be measured by dispersing the non-Ti-based metal oxide particles in pure water (non-Ti-based metal oxide particle concentration: 1% by mass) and then using a commercially available particle size distribution measuring device (for example, the Zetasizer Nano ZS manufactured by Malvern Panalytical).

[0017] The non-Ti-based metal oxide particles are preferably porous. The BET specific surface area of ​​the porous material is 10 m 2 / g or more, and 2 / g or more is more preferable, and 30m 2It is more preferable that it is / g or more. Further, the BET specific surface area of the porous body is 600 m 2 / g or less, preferably 500 m 2 / g or less, more preferably 400 m 2 / g or less, and still more preferably / g or less

[0018] <Ti-based oxide fine particles> The Ti-based oxide fine particles, which are raw materials in the method for producing the catalyst composition of the present invention, will be described. Ti-based oxide fine particles refer to particles in which the mass of Ti in terms of TiO2 contained in the particles is 90% by mass or more based on the mass of the particles, and the median diameter D50 is 1 nm or more and 500 nm or less. The definition of the median diameter D50 is the same as the definition of the median diameter D50 of non-Ti-based metal oxide particles. Whether the mass of Ti in terms of TiO2 contained in a certain particle is 90% by mass or more based on the mass of the particle can be measured in the same manner as the composition of non-Ti-based metal oxide particles. The median diameter D50 of a certain particle can be measured in the same manner as the median diameter D50 of non-Ti-based metal oxide particles. The mass of Ti in terms of TiO2 contained in the Ti-based oxide fine particles is 90% by mass or more based on the mass of the Ti-based oxide fine particles, preferably 95% by mass or more, more preferably 98% by mass or more, and most preferably 100% by mass.

[0019] The mass of the Ti-based oxide fine particles in the raw material stage is 2% by mass or more and 8% by mass or less, preferably 2% by mass or more and 7% by mass or less, and more preferably 3% by mass or more and 6% by mass or less, based on the total mass of the non-Ti-based metal oxide particles and the Ti-based oxide fine particles in the raw material stage.

[0020] The Ti-based oxide fine particles in the raw material stage exhibit a rutile-type crystal structure. It can be determined that the Ti-based oxide fine particles exhibit a rutile-type crystal structure by performing powder X-ray diffraction measurement (XRD) on the Ti-based oxide fine particles and detecting a peak at 36.1 ± 0.5°.

[0021] The median diameter D50 of the Ti-based oxide fine particles in the raw material stage is 1 nm or more and 500 nm or less, preferably 5 nm or more and 300 nm or less, and more preferably 10 nm or more and 200 nm or less. When the median diameter D50 of the Ti-based oxide fine particles is 500 nm or less, the diffusion of Ru particles deep into the interior of the Ti-based oxide fine particles can be suppressed. Further, when the median diameter D50 of TiO2 is 1 nm or more, the movement of Ru particles and the accompanying aggregation can be suppressed. The method for measuring the volume-based particle size distribution of the Ti-based oxide fine particles by the dynamic light scattering method is the same as the method for measuring the volume-based particle size distribution of non-Ti-based metal oxide particles.

[0022] <Ru source> The Ru source, which is a raw material in the method for producing the catalyst composition of the present invention, will be described. The Ru source only needs to contain at least the Ru (ruthenium) element, and the Ru contained in the Ru source may be in a metallic state or in a state of a compound such as an oxide. Further, the Ru contained in the Ru source may be in the form of particles or not in the form of particles. Examples of the Ru source include metallic Ru, oxides of Ru, hydroxides of Ru, salts containing Ru, molecules containing Ru, complexes containing Ru, etc. Examples of the salt containing Ru include ruthenium nitrate, ruthenium chloride, ruthenium acetate, ruthenium sulfate, etc.

[0023] (Step (2)) Step (2) of the production method of the present invention will be described. Step (2) is a step of supporting Ti-based oxide fine particles and Ru particles on non-Ti-based metal oxide particles using the raw materials prepared in step (1). By carrying out step (2), a catalyst composition in which Ti-based oxide fine particles and Ru particles are supported on non-Ti-based metal oxide particles can be obtained. The Ru particles are particles containing Ru element. The Ru particles are not particularly limited as long as they exhibit the catalytic activity of the present invention, and may be a metal or a compound such as an oxide, but are preferably at least one of a metal or an oxide. The Ru particles are derived from the Ru source prepared in step (1), but Ru particles may not be present in the Ru source at the raw material stage and may be formed during the process.

[0024] In the production method of the present invention, Ti-based oxide fine particles and Ru particles may be simultaneously supported on non-Ti-based metal oxide particles, or Ti-based oxide fine particles may first be supported on non-Ti-based metal oxide particles to obtain supported particles, and then the Ru particles may be supported on the supported particles. Examples of methods for simultaneously supporting Ti-based oxide fine particles and Ru particles on non-Ti-based metal oxide particles include dispersing or dissolving non-Ti-based metal oxide particles, Ti-based oxide fine particles, and a Ru source such as a Ru salt in a dispersion medium such as water, and evaporating the mixture to dryness. However, from the viewpoint of improving the contact between the Ru particles and the reaction gas in the catalyst composition and enhancing the activity of the catalyst composition, it is preferable to first support Ti-based oxide fine particles on non-Ti-based metal oxide particles, obtain supported particles, and then support the Ru particles on the supported particles. That is, step (2) preferably includes the following steps (2-1) and (2-2). Step (2-1): A step of supporting Ti-based oxide fine particles on non-Ti-based metal oxide particles to obtain supported particles. Step (2-2): A step of supporting Ru particles on support particles

[0025] The step (2-1) is a step of supporting Ti-based oxide fine particles on non-Ti-based metal oxide particles to obtain supported particles. The phrase "Ti-based oxide fine particles are supported on non-Ti-based metal oxide particles" refers to a state in which the Ti-based oxide fine particles are physically or chemically adsorbed or held on the outer surface or inner pore surface of the non-Ti-based metal oxide particles. The method for supporting Ti-based oxide microparticles on non-Ti-based metal oxide particles is not particularly limited, and examples include a method of mixing Ti-based oxide microparticles and non-Ti-based metal oxide particles in a dispersion liquid, a method of dispersing Ti-based oxide microparticles in a gas to form an aerosol and using the aerosol to deposit Ti-based oxide microparticles on the surface of non-Ti-based metal oxide particles, and a method of charging Ti-based oxide microparticles with a positive or negative charge and charging the non-Ti-based metal oxide particles with the other charge, thereby depositing Ti-based oxide microparticles on the surface of non-Ti-based metal oxide particles. Hereinafter, a method for mixing Ti-based oxide fine particles and non-Ti-based metal oxide particles in a dispersion will be described. When Ti-based oxide fine particles and non-Ti-based metal oxide particles are mixed in a dispersion liquid, the Ti-based oxide fine particles and non-Ti-based metal oxide particles may be added to the dispersion medium simultaneously, or one of the Ti-based oxide fine particles or the non-Ti-based metal oxide particles may be first dispersed in the dispersion medium and then the other may be added. However, from the viewpoint of more uniformly supporting the Ti-based oxide fine particles on the surfaces of the non-Ti-based metal oxide particles, it is preferable to first disperse the Ti-based oxide fine particles in the dispersion medium and then add the non-Ti-based metal oxide particles. The Ti-based oxide fine particles used in step (2-1) contain a rutile-type crystal structure. The mass of TiO2 containing the rutile-type crystal structure is preferably 80 mass% or more, more preferably 90 mass% or more, even more preferably 95 mass% or more, and particularly preferably 100 mass% of the total mass of the Ti-based oxide fine particles used in step (2-1).

[0026] The liquid used as the dispersion medium is not particularly limited, but examples thereof include water. In the dispersion of Ti-based oxide microparticles, the mass of the Ti-based oxide microparticles relative to the volume of the dispersion medium is preferably 0.1 g / L or more and 20 g / L or less, more preferably 0.5 g / L or more and 15 g / L or less, and even more preferably 1 g / L or more and 10 g / L or less.

[0027] Next, non-Ti-based metal oxide particles are added to the dispersion liquid to cause the Ti-based oxide fine particles to be supported on the non-Ti-based metal oxide particles, thereby obtaining supported particles. The content of Ti-based oxide microparticles supported on non-Ti-based metal oxide particles in the supported particles is 2% by mass or more and 8% by mass or less, preferably 2% by mass or more and 7% by mass or less, and more preferably 3% by mass or more and 6% by mass or less, relative to the mass of the supported particles.

[0028] The method for supporting Ti-based oxide fine particles in a non-Ti-based metal oxide particle dispersion is not particularly limited, and known methods can be used. For example, the Ti-based oxide fine particles in the dispersion can be supported on the non-Ti-based metal oxide particles by adding the non-Ti-based metal oxide particles, stirring the dispersion, and drying it. Alternatively, the non-Ti-based metal oxide particles may be added to the dispersion, stirring the mixture, and drying to obtain a solid, which can then be fired. The temperature for firing the solid is not particularly limited, but is preferably 300 to 600°C. The firing time is not particularly limited, but is preferably 0.1 to 24 hours.

[0029] Step (2-2) is a step of supporting Ru particles on the support particles obtained in step (2-1). By supporting Ru particles on the support particles, the catalyst composition of the present invention can be obtained. The method for supporting Ru particles on the supported particles obtained in step (2-1) is not particularly limited, and known methods can be used. In one embodiment, the supported particles obtained in step (2-1) are dispersed in a dispersion medium (e.g., a liquid such as water) to obtain a supported particle dispersion, to which a Ru source (e.g., a salt containing Ru element and soluble in the dispersion medium, or pre-prepared Ru particles, etc.) is added, stirred, and dried to remove the dispersion medium. In another embodiment, a Ru source soluble in the dispersion medium (e.g., a salt containing Ru element) is added to the supported particle dispersion and stirred, and then a substance for converting the Ru source into a substance insoluble in the dispersion medium (e.g., a base such as ammonia) is added, and the dispersion medium is removed by filtration. In either embodiment, the solid obtained after removing the dispersion medium may be calcined. The temperature for calcining the solid is not particularly limited, but 300 to 600°C is preferred. The calcination time is not particularly limited, but 0.1 to 24 hours is preferred.

[0030] In the catalyst composition of the present invention, at least a portion of the Ru particles is preferably supported on at least a portion of the non-Ti-based metal oxide particles and the Ti-based oxide fine particles supported on the non-Ti-based metal oxide particles, and more preferably supported on at least a portion of the Ti-based oxide fine particles. The statement that Ru particles are supported on at least a portion of the non-Ti-based metal oxide particles and Ti-based oxide microparticles means that the Ru particles are physically or chemically adsorbed or held on the outer surface or inner pore surface of at least a portion of the non-Ti-based metal oxide particles and Ti-based oxide microparticles.

[0031] The Ru content in the catalyst composition of the present invention is not particularly limited, but is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 8% by mass or less, and even more preferably 3% by mass or more and 7% by mass or less, based on the total mass of the non-Ti-based metal oxide particles, the Ti-based oxide fine particles, and the Ru source. The Ru content in the catalyst composition can be measured by ICP-AES. The mass of Ru supported on at least one of the non-Ti-based metal oxide particles and the Ti-based oxide microparticles supported on the non-Ti-based metal oxide particles is preferably 80 mass% or more, more preferably 90 mass% or more, even more preferably 95 mass% or more, and particularly preferably 100 mass% of the total mass of Ru contained in the catalyst composition in terms of metal.

[0032] <Form of catalyst composition> The form of the catalyst composition of the present invention is not particularly limited. The catalyst composition of the present invention may be, for example, a powder, a slurry, or a molded body. The shape of the molded body may be, for example, spherical or cylindrical.

[0033] <Uses of catalyst composition> The catalyst composition of the present invention is preferably a catalyst composition for a reaction between CO2 and H2. For example, CO can be obtained by the reaction shown in the following formula (a1): CO2+H2→CO+H2O (a1)

[0034] The raw material gas used as the raw material for the reaction is not particularly limited as long as it contains at least CO2 and H2. For example, CO2 may be a mixed gas generated in a process of burning hydrocarbons as fuel or a process of burning unreacted hydrocarbons in oil refineries, petrochemicals, power generation, steelmaking, boilers, etc., or may be purified before use. CO2 from the atmosphere may also be concentrated and used.

[0035] The volume ratio of H2 to CO2 in the raw material gas (H2 / CO2) is not particularly limited, but is preferably 0.5 or more and 7 or less, and more preferably 1 or more and 5 or less.

[0036] The source gas may further contain compounds other than CO and H as long as they do not inhibit the reaction between CO and H. For example, the source gas may further contain an inert gas such as nitrogen or argon.

[0037] The reaction of CO2 with H2 can be carried out, for example, by using a reactor filled with the catalyst composition of the present invention and passing a raw material gas through the reactor. Various reactors used in gas-phase reactions using solid catalysts can be used as the reactor. Examples of the reactor include a fixed-bed reactor, a radial flow reactor, and a tubular reactor.

[0038] The temperature at which the raw material gas is brought into contact with the catalyst composition of the present invention is not particularly limited, but is preferably 100°C or higher and 600°C or lower, more preferably 150°C or higher and 550°C or lower.

[0039] The pressure when the raw material gas is brought into contact with the catalyst composition of the present invention is not particularly limited, but is, for example, 0.05 MPa or more and 4 MPa or less.

[0040] When the reaction is carried out while continuously supplying the raw materials, the space velocity is not particularly limited, but it is preferable to use a space velocity of 10 h -1 More than 100000h -1 Less than 100h is preferable-1 Over 50,000h -1 The following is more preferable. Here, the space velocity is the volume V (m 3 ) to the feed rate of the raw gas (feed volume / time) F(m 3 h -1 ) ratio F / V(h -1 ) [Example]

[0041] Next, the embodiments of the present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

[0042] Example 1 (I) Preparation of rutile TiO2(a) / CeO2 powder 0.16 g of commercially available Ti-based oxide fine particles (rutile-type TiO2) powder (manufactured by Sakai Chemical Industry Co., Ltd., STR-100N) exhibiting a rutile crystal structure was dispersed in 45 ml of pure water, to which 5.08 g of commercially available CeO2 powder (manufactured by Solvay) was added and stirred for 30 minutes. The mixture was evaporated to dryness while stirring, and the resulting dry powder was calcined at 500°C for 1 hour to obtain supported particles in which rutile-type TiO2, Ti-based oxide fine particles, were supported on CeO2, non-Ti-based metal oxide particles (also referred to as "rutile-type TiO2(a) / CeO2 powder"). The mass of the Ti-based oxide fine particles used as raw material was 3.0 mass % based on the total mass of the non-Ti-based metal oxide particles used as raw material and the Ti-based oxide fine particles used as raw material. The amount of Ti in the Ti-based oxide fine particles used as the raw material, converted into TiO2, was nearly 100 mass % (>99 mass %). The median diameter D50 of the Ti-based oxide fine particles was 112 nm, and the median diameter D50 of the non-Ti-based metal oxide particles was 5.0 μm.

[0043] (II) Preparation of Ru / rutile-type TiO2(a) / CeO2 powder 2.90 g of the rutile TiO2(a) / CeO2 powder prepared in (I) above was dispersed in 24 ml of pure water, and a ruthenium nitrate solution was added and stirred for 1 hour. 1.20 g of 28% aqueous ammonia was then added and stirred for 5 minutes. The resulting solution was then filtered through a 0.2 μm membrane filter, and the residue was washed repeatedly with pure water and then dried at 120°C. The resulting dried powder was calcined at 500°C for 3 hours to obtain a powder in which Ru particles were supported on the rutile TiO2(a) / CeO2 powder (also referred to as "Ru / rutile TiO2(a) / CeO2 powder"). The content of Ru particles relative to the mass of the Ru / rutile-type TiO2(a) / CeO2 powder was 5.0 mass%. The Ru / rutile TiO2(a) / CeO2 powder is the catalyst composition of Example 1.

[0044] <Example 2> The procedure in (I) of Example 1 was repeated except that the amount of rutile-type TiO2 powder was changed to 0.27 g, to obtain supported particles in which rutile-type TiO2, which is a Ti-based oxide fine particle, is supported on CeO2, which is a non-Ti-based metal oxide particle (also referred to as "rutile-type TiO2(b) / CeO2 powder"). The mass of the Ti-based oxide fine particles used as raw material was 5.0 mass % based on the total mass of the non-Ti-based metal oxide particles used as raw material and the Ti-based oxide fine particles used as raw material. Ru particles were supported on the rutile TiO2(b) / CeO2 powder using the same procedure as in (II) of Example 1, to obtain a powder in which Ru particles were supported on the rutile TiO2(b) / CeO2 powder (also referred to as "Ru / rutile TiO2(b) / CeO2 powder"). The Ru / rutile TiO2(b) / CeO2 powder is the catalyst composition of Example 2.

[0045] Example 3 In the procedure of Example 1 (I), the same procedure was followed except that 5.08 g of CeO2 powder was replaced with 5.08 g of Al2O3 powder (manufactured by Sumitomo Chemical), and supported particles (also referred to as "rutile-type TiO2(a) / Al2O3 powder") were obtained in which rutile-type TiO2, which is a Ti-based oxide fine particle, is supported on Al2O3, which is a non-Ti-based metal oxide particle. Furthermore, by the same procedure as in Example 1 (II), a powder in which Ru particles were supported on rutile-type TiO2(a) / Al2O3 powder (also referred to as "Ru / rutile-type TiO2(a) / Al2O3 powder") was obtained. The median diameter D50 of the non-Ti-based metal oxide particles was 10.8 μm. The Ru / rutile TiO2(a) / Al2O3 powder is the catalyst composition of Example 3.

[0046] <Comparative Example 1> In the procedure of (II) of Example 1, 2.90 g of CeO powder was used instead of 2.90 g of rutile TiO(a) / CeO powder, and Ru particles were supported on the CeO powder in the same manner as in (II) of Example 1 to obtain Ru / CeO powder. The Ru / CeO powder does not contain rutile TiO. The Ru / CeO2 powder is the catalyst composition of Comparative Example 1.

[0047] <Comparative Example 2> Rutile-type TiO2(c) / CeO2 powder was obtained in the same manner as in the procedure of (I) of Example 1, except that the amount of rutile-type TiO2 powder was changed to 0.05 g. The mass of the Ti-based oxide fine particles used as raw material was 1.0 mass % relative to the total mass of the non-Ti-based metal oxide particles used as raw material and the Ti-based oxide fine particles used as raw material. Ru particles were supported on the rutile TiO2(c) / CeO2 powder in the same manner as in Example 1 (II), to obtain Ru / rutile TiO2(c) / CeO2 powder. The Ru / rutile TiO2(c) / CeO2 powder is used as the catalyst composition of Comparative Example 2.

[0048] <Comparative Example 3> The procedure in (I) of Example 1 was repeated except that the amount of rutile-type TiO2 powder was changed to 0.56 g, to obtain supported particles in which rutile-type TiO2, which is a Ti-based oxide fine particle, is supported on CeO2, which is a non-Ti-based metal oxide particle (also referred to as "rutile-type TiO2(d) / CeO2 powder"). The mass of the Ti-based oxide fine particles used as raw material was 10.0 mass % based on the total mass of the non-Ti-based metal oxide particles used as raw material and the Ti-based oxide fine particles used as raw material. Ru particles were supported on the rutile TiO2(d) / CeO2 powder in the same manner as in Example 1 (II), to obtain Ru / rutile TiO2(d) / CeO2 powder. The Ru / rutile-type TiO2(d) / CeO2 powder is used as the catalyst composition of Comparative Example 3.

[0049] <Comparative Example 4> In the procedure of (I) of Example 1, 0.16 g of rutile-type TiO2 powder was replaced with 0.16 g of TiO2 powder (anatase-type TiO2) (SSP-M, manufactured by Sakai Chemical Industry Co., Ltd.) that does not exhibit a rutile-type crystal structure but exhibits an anatase-type crystal structure. The same procedure was repeated to obtain particles in which anatase-type TiO2 was supported on CeO2, a non-Ti-based metal oxide particle (also referred to as "anatase-type TiO2(e) / CeO2 powder"). Furthermore, by the same procedure as in Example 1 (II), a powder in which Ru particles were supported on anatase TiO2(e) / CeO2 powder (also referred to as "Ru / anatase TiO2(e) / CeO2 powder") was obtained. The median diameter D50 of the anatase TiO2 was 30 nm. The Ru / anatase TiO2(e) / CeO2 powder is used as the catalyst composition of Comparative Example 4.

[0050] <Comparative Example 5> (III) Preparation of Ru / [CeO2 + rutile TiO2] mixed powder 2.81 g of commercially available CeO powder (Solvay) and 0.086 g of commercially available rutile TiO powder (Fujifilm Wako Pure Chemical Industries, Ltd.) were dispersed in 24 ml of pure water, followed by the addition of a ruthenium nitrate solution and stirring for 1 hour. Then, 1.20 g of 28% aqueous ammonia was added and stirred for 5 minutes. The mixture was then filtered through a 0.2 μm mesh membrane filter, and the residue was washed repeatedly with pure water and then dried at 120 °C. The resulting dried powder was calcined at 500 °C for 3 hours to obtain a powder in which Ru particles were supported on non-Ti metal oxide particles, CeO and rutile TiO (also referred to as "Ru / [CeO + rutile TiO] mixed powder"). The Ru particle content relative to the mass of the Ru / [CeO + rutile TiO] mixed powder was 5.0 mass%. The median diameter D50 of CeO2 was 5.0 μm, and the median diameter D50 of rutile-type TiO2 was 2.9 μm. The Ru / [CeO2+rutile-type TiO2] mixed powder was used as the catalyst composition of Comparative Example 5. Although the rutile-type TiO2 of Comparative Example 5 is not a non-Ti-based metal oxide particle, for convenience it is listed in the "Type of non-Ti-based metal oxide particle" column in Table 1 below.

[0051] <Comparative Example 6> In the procedure of Comparative Example 1, except that 2.90 g of CeO2 powder was replaced with 2.90 g of commercially available rutile-type TiO2 powder (manufactured by Fujifilm Wako Pure Chemical Industries), the same procedure was followed to support Ru particles on rutile-type TiO2, which is a non-Ti-based metal oxide particle, and obtain Ru / rutile-type TiO2 powder. The median diameter D50 of the rutile-type TiO2 was 2.9 μm. The Ru / rutile TiO2 powder is used as the catalyst composition of Comparative Example 6. Although the rutile-type TiO2 of Comparative Example 6 is not a non-Ti-based metal oxide particle, for convenience it is listed in the "Type of non-Ti-based metal oxide particle" column in Table 1 below.

[0052] <Comparative Example 7> In the operation of Comparative Example 1, except that 2.90 g of CeO2 powder was changed to 2.90 g of commercially available anatase-type TiO2 powder (manufactured by Fujifilm Wako Pure Chemical Corporation), Ru particles were supported on anatase-type TiO2, which is a non-Ti-based metal oxide particle, in the same operation to obtain Ru / anatase-type TiO2 powder. The median diameter D50 of the anatase-type TiO2 was 1.9 μm. The Ru / anatase-type TiO2 powder is used as the catalyst composition of Comparative Example 7. Although the anatase-type TiO2 of Comparative Example 7 is not a non-Ti-based metal oxide particle, for convenience, it is described in the column of "type of non-Ti-based metal oxide particles" in Table 1 below.

[0053] <CO2 Reduction Activity Evaluation Method> The CO2 reduction activity was evaluated using a catalyst analyzer (BELCAT-A manufactured by BEL JAPAN, INC.). A 100 mg sample of the catalyst composition of each example and comparative example was reduced at 500 °C in an atmosphere of 0.75 vol% H2 and the balance Ar (argon), and then cooled to 50 °C in Ar. Subsequently, while flowing a reaction gas of 0.75 vol% H2, 1.5 vol% CO2, and the balance Ar, the sample was heated from 50 °C to 500 °C at a rate of 10 °C / min. CO (Mass No. 28) flowing out from the outlet of the reaction tube was measured using a gas analyzer (BELMASS) by mass spectrometry attached to the catalyst analyzer, and the CO production intensity was determined from the peak intensity at the time of reaching 500 °C (peak intensity at 500 °C). The greater the peak intensity at 500 °C, the greater the CO production intensity and the higher the activity of CO2 conversion. The results are shown in Table 1 below.

[0054] <XRD Measurement Method> Using each catalyst composition obtained in Example 1 and Comparative Example 4, X-ray diffraction (XRD) was performed 30 times using a commercially available powder X-ray diffractometer ("MiniFlex600" manufactured by Rigaku Corporation) under the following conditions: X-ray source: CuKα, scanning axis: 2θ / θ, measurement method: continuous, counting unit: cps, start angle: 20°, end angle: 40°, sampling width: 0.01°, scan speed: 3° / min, voltage: 40 kV, current: 15 mA. The obtained data for 30 runs were analyzed for the crystal structure of TiO2 using analysis software ("PDXL version 2" manufactured by Rigaku Corporation), and the presence or absence of a peak at 36.1±0.5° due to rutile-type TiO2 was confirmed. As a result, a peak at 36.1±0.5° derived from rutile TiO2 was confirmed for the catalyst composition of Example 1. The peak at 36.1±0.5° derived from rutile TiO2 was not confirmed for the catalyst composition of Comparative Example 4 (a peak derived from anatase TiO2 was confirmed for the catalyst composition of Comparative Example 4).

[0055] In Table 1, "Content of Ti-based oxide microparticles" is the ratio of the mass of Ti-based oxide microparticles in the raw material stage to the total mass of the Ti-based oxide microparticles in the raw material stage and the mass of the non-Ti-based metal oxide particles in the raw material stage. In Table 1, "E-11" means "×10 -11 " means.

[0056] [Table 1]

[0057] From Table 1, it was found that the catalyst compositions of Examples 1 to 3 had a higher CO production intensity and higher CO2 conversion activity than the catalyst compositions of Comparative Examples 1 to 7.

Claims

1. TiO ２ Ti-based oxide fine particles having a converted content of 90 mass% or more and a median diameter D50 of 1 nm or more and 500 nm or less; TiO ２ non-Ti-based metal oxide particles having a converted content of 1% by mass or less; (1) preparing a Ru source as a raw material; and a step (2) of supporting the Ti-based oxide fine particles and Ru particles on the non-Ti-based metal oxide particles using the raw material; 1. A method for producing a catalyst composition comprising: The Ti-based oxide fine particles in the step (1) exhibit a rutile crystal structure, A method for producing a catalyst composition, wherein the mass of the Ti-based oxide fine particles in the step (1) is 2 mass% or more and 8 mass% or less relative to the total mass of the Ti-based oxide fine particles in the step (1) and the mass of the non-Ti-based metal oxide particles in the step (1).

2. The method for producing a catalyst composition according to claim 1, wherein the step (2) comprises the following steps (2-1) and (2-2): Step (2-1): A step of supporting the Ti-based oxide fine particles on the non-Ti-based metal oxide particles to obtain supported particles. Step (2-2): A step of supporting the Ru particles on the support particles

3. 2. The method for producing a catalyst composition according to claim 1, wherein the non-Ti-based metal oxide particles have a median diameter D50 of 0.5 μm or more and 500 μm or less.

4. 2. The method for producing a catalyst composition according to claim 1, wherein the non-Ti-based metal oxide particles contain at least one oxide selected from the group consisting of oxides of Ce element and oxides of Al element.

5. The method for producing a catalyst composition according to claim 1 , wherein the non-Ti-based metal oxide particles contain an oxide of the Ce element.

6. The catalyst composition ２ and H ２ The method for producing the catalyst composition according to any one of claims 1 to 5, which is a catalyst composition for a reaction in which

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