Catalyst and method for producing methanol using catalyst

Abstract

The present invention improves catalytic activity. A catalyst according to one embodiment of the present disclosure is used in a reaction in which a carbon oxide is contained in a raw material. The catalyst includes copper atoms and zinc atoms. The average distance between copper and zinc calculated from a mapping image of the copper atoms and the zinc atoms acquired by scanning transmission electron microscope energy dispersive X-ray spectroscopy is 1.55-2.90 nm. In the mapping image, a copper atom region and a zinc atom region are specified, and the average distance between copper and zinc is a value obtained by deriving, for each first pixel that is a pixel located in the copper atom region, the distance to a second pixel that is a pixel closest to the center of the first pixel in the zinc atom region, and averaging the distances.

Description

Catalyst and method for producing methanol using the catalyst

[0001] The present disclosure relates to a catalyst used for a reaction using a carbon oxide as a raw material, and to a method for producing methanol using said catalyst.

[0002] Examples of reactions using a carbon oxide as a raw material include methanol synthesis reaction. Methanol derived from renewable resources (hereinafter referred to as green methanol) is attracting attention as a clean chemical raw material and energy carrier, and its market size is large and steady growth is expected.

[0003] As a catalyst for promoting a methanol synthesis reaction, for example, Patent Document 1 discloses a catalyst containing copper and zinc.

[0004] International Publication No. 2013 / 183577 Pamphlet

[0005] For such catalysts, it is desired to improve the catalytic activity.

[0006] A catalyst according to one aspect of the present disclosure is a catalyst used for a reaction using a carbon oxide as a raw material, the catalyst comprising copper atoms and zinc atoms, wherein an average distance between copper and zinc calculated from a mapping image of copper atoms and zinc atoms obtained by scanning transmission electron microscope-energy dispersive X-ray spectroscopy is 1.55 nm or more and 2.90 nm or less.

[0007] According to one aspect of the present disclosure, catalytic activity can be improved.

[0008] It is a diagram schematically showing the distance between a pixel located in a copper atom region and a pixel located in a zinc atom region that is closest to the center of said pixel. It is a graph showing the relationship between the average distance between copper and zinc obtained from a STEM-EDX mapping image and methanol selectivity for each example and comparative example.

[0009] [Embodiment 1] The catalyst according to the present disclosure is described in detail below. Hereinafter, a catalyst falling within the scope of the present disclosure is referred to as the present catalyst. Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more and B or less".

[0010] This catalyst is used in reactions that involve carbon oxides as raw materials. This catalyst contains copper atoms (Cu atoms) and zinc atoms (Zn atoms). Furthermore, in this catalyst, the average distance between copper (Cu) and zinc (Zn) (Cu-Zn average distance), calculated from mapping images of Cu atoms and Zn atoms obtained by scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDX), is between 1.55 nm and 2.90 nm. In this specification, for simplicity, copper may be referred to as Cu, zinc as Zn, copper atoms as Cu atoms, and zinc atoms as Zn atoms.

[0011] Catalytic activity varies depending on various factors, such as the raw material composition and / or manufacturing conditions. The inventors have found that catalytic activity improves when the distance between Cu and Zn in the catalyst is within a specific range. Specifically, they found that in a catalyst containing copper and zinc, used in a reaction involving carbon oxides as raw materials, a highly active catalyst can be obtained by specifying the average distance between Cu and Zn.

[0012] When a catalyst containing copper and zinc is used in a reaction that uses carbon oxides as raw materials, if the distance between Cu and Zn is too great, the number of catalytic active sites will decrease. On the other hand, if the distance between Cu and Zn is too great, it is thought that the metal-metal interaction between Cu and Zn will become excessive, making side reactions more likely, or the active sites will be more susceptible to poisoning by reaction gases or by-products. Therefore, the average distance between Cu and Zn may be in the range of 1.55 nm to 2.90 nm, more preferably 1.58 nm to 2.80 nm, and even more preferably 1.60 nm to 2.60 nm.

[0013] Because this catalyst possesses the above-mentioned characteristics, catalytic activity is improved, and the yield of the product can be increased.

[0014] Reactions that use carbon oxides as raw materials include, for example, carbon monoxide (CO) and / or carbon dioxide (CO2). ２The catalyst may include the following as a raw material: More specifically, it may be a methanol synthesis reaction in which a raw material containing a carbon oxide and hydrogen is brought into contact with a catalyst to obtain methanol. By using this catalyst in a methanol synthesis reaction, methanol selectivity can be improved.

[0015] In this disclosure, the average distance between Cu and Zn can be determined as follows. First, regions of Cu atoms and regions of Zn atoms are identified in the mapping image obtained by STEM-EDX. For each of the first pixels located in the identified Cu atom region, the distance from the center of each first pixel to the second pixel, which is the closest pixel in the identified Zn atom region, is derived and averaged.

[0016] Figure 1 schematically shows the distance between a pixel located in the region of a Cu atom and the nearest pixel located in the region of a zinc atom from the center of that pixel.

[0017] Furthermore, in this catalyst, the average pore diameter measured by the nitrogen gas adsorption method may be between 11 nm and 17 nm. If the average pore diameter is too large, the surface area of ​​the catalyst used in the reaction will be small, and if the average pore diameter is too small, the surface area used in the reaction will be small due to the aggregation of the product into the pores. Therefore, the average pore diameter may be between 11 nm and 17 nm. By keeping the average pore diameter within this range, catalytic activity can be further improved.

[0018] In this disclosure, the average pore diameter (nm) is obtained based on measurements using the nitrogen adsorption method. Specifically, the specific surface area and pore size distribution of the catalyst can be measured using the automated specific surface area / pore size distribution analyzer "BELSORP-mini X" (manufactured by Microtrac-Bel). Surface area measurement in this measurement is performed using the BET method. The catalyst used for measurement is a sample that has been vacuum-dried at 120°C for 2 hours. Nitrogen gas is used as the processing gas, and the processing temperature is the liquid nitrogen temperature.

[0019] BET specific surface area (m ２The value ( / g) is obtained by analyzing the relative pressure range p / p0 = 0.1000 to 0.2500. Total pore volume (cm³ ３ The value ( / g) is obtained from the nitrogen adsorption capacity up to a relative pressure p / p0 = 0.9900. The pore diameter (nm) is the pore diameter calculated from the BET specific surface area and total pore volume, assuming cylindrical pores.

[0020] This catalyst consists of copper oxide (CuO), zinc oxide (ZnO), and aluminum oxide (Al ２ O ３ ) may contain. In this catalyst, the copper oxide content may be 50 to 80% by mass, preferably 55 to 80% by mass, and more preferably 60 to 79% by mass. By setting the copper oxide content to 50 to 80% by mass, the methanol yield can be improved.

[0021] Furthermore, in this catalyst, the mass content ratio of zinc oxide to copper oxide may be 0.10 to 0.52, preferably 0.15 to 0.50, and more preferably 0.18 to 0.45. The mass content ratio of zinc oxide to copper oxide can be determined by dividing the mass of zinc oxide contained in this catalyst by the mass of copper oxide. If the content ratio is too low, aggregation of Cu crystals is likely to occur, and the activity may decrease rapidly. If the content ratio is too high, the amount of Cu, which is the active component, will decrease, and the activity may decrease. By setting the mass content ratio of zinc oxide to copper oxide to 0.10 to 0.52, a catalyst with high catalytic activity can be realized.

[0022] This catalyst may further contain doping elements. The doping elements contained in this catalyst may be rare earth elements, alkali metals, alkaline earth metals, transition metals, or metal oxides. The elements used as doping elements may be gallium, tantalum, palladium, zirconium, magnesium, silicon, boron, samarium, cerium, lanthanum, neodymium, europium, or erbium. For example, the doping elements contained in this catalyst may be gallium, tantalum, and samarium.

[0023] Furthermore, in this catalyst, the elemental ratio (molar ratio) of the doped element to copper may be less than 0.01, preferably 0.005 or less, and more preferably 0.003 to 0.005. Also, in this catalyst, the elemental ratio (molar ratio) of the doped element to zinc may be less than 0.022. Furthermore, in this catalyst, the elemental ratio (molar ratio) of the doped element to aluminum may be less than 0.25, preferably less than 0.1, and more preferably 0.015 to 0.090.

[0024] <Method for Manufacturing the Catalyst> Next, a method for manufacturing the catalyst will be described. The method for manufacturing the catalyst according to this disclosure is not particularly limited and may be a known method. For example, it may be manufactured by precipitating an aqueous solution of an acidic salt of each metal element constituting the catalyst with a precipitating agent, followed by drying and calcination (see Japanese Patent Application Publication No. 2010-194421).

[0025] More specifically, the method for producing the catalyst may include the following steps (1) to (5): (1) Coprecipitation step: A step in which a precipitating agent is added to a solution or suspension of an acidic salt of each metal element constituting the catalyst or a metal compound, and the complex salt (mainly carbonate) is precipitated. In the coprecipitation step, maturation for a predetermined time may be performed in order to obtain a highly active catalyst precursor. (2) Washing step: A step in which the complex salt is filtered and washed. (3) Drying step: A step in which the cake obtained by filtration is dried. (4) Calcination step: A step in which the complex salt is calcined and converted into an oxide. (5) Molding step: A step in which the powder oxide obtained after the calcination step is compressed into tablets.

[0026] In the coprecipitation step described in (1) above, an acidic solution and a precipitating agent may be added simultaneously to a solution or suspension of one or more acidic salts or metal compounds to precipitate the complex salt. The solution or suspension of the acidic salt or metal compound and the acidic solution may contain copper, zinc, aluminum, and doped elements. The acidic salt of each metal element may be one or more selected from the group consisting of nitrates, sulfates, acetates, formates, oxalates, phosphates, aluminates, and halides, and is preferably a nitrate or sulfate.

[0027] The metal compound of each metal element may be one or more selected from the group consisting of oxides and carbonates, preferably an oxide, and more preferably an alumina sol. The precipitating agent may be one or more selected from the group consisting of sodium carbonate, sodium bicarbonate, and sodium hydroxide, and is preferably sodium carbonate. In the above (1) coprecipitation step, the solvent may be one or more selected from the group consisting of water, methanol, ethanol, isopropanol, ethyl acetate, tetrahydrofuran, and dichloromethane, preferably water and ethanol, and more preferably water.

[0028] <Method for Producing Methanol> The following describes a method for producing methanol using this catalyst. A methanol production method according to one embodiment of this disclosure includes the step of contacting a raw material gas containing carbon oxides and hydrogen with the catalyst according to this disclosure to obtain methanol. As described above, this catalyst has the characteristics described above and can improve methanol yield.

[0029] The reaction conditions in this process may be, for example, a reaction temperature of 150 to 300°C and a reaction pressure (gauge pressure) of 0.5 to 10 MPaG.

[0030] An example of a reactor used in this process is a fixed-bed reactor. Alternatively, an internal condensation reactor may be used, which has a condensation surface and allows the methanol synthesis reaction to proceed by condensing the high-boiling components, including methanol and water, produced within the reactor.

[0031] <Raw Material Gas> The raw material gas contains carbon oxides and hydrogen. In the methanol production method according to this embodiment, the raw material gas may contain carbon dioxide and hydrogen. Alternatively, carbon monoxide and carbon dioxide may be included as carbon oxides. When both carbon monoxide and carbon dioxide are used as carbon oxides, they may be included in any ratio.

[0032] The molar ratio of hydrogen to carbon oxides in the raw material gas is not particularly limited. The raw material gas may contain components other than carbon oxides and hydrogen, as long as they do not affect methanol production. Examples of such components include third components such as nitrogen and impurities such as by-products associated with carbon oxide production. The raw material gas may also contain water.

[0033] Carbon oxides, hydrogen, and water vapor may be introduced into the reactor separately, or they may be introduced into the reactor as a mixed gas in any combination.

[0034] [Use of Catalyst] When this catalyst is used in reactions that include carbon oxides as raw materials, such as methanol production methods, the catalyst may be used after being reduced with a reducing gas (hydrogen, a mixture of hydrogen and nitrogen, a gas containing carbon monoxide, etc.). By contacting this catalyst containing copper oxide with a reducing gas, CuO can be reduced to Cu, which has catalytic activity.

[0035] Furthermore, after the reaction using this catalyst is complete, the catalyst may be subjected to an inert treatment by oxidation with an oxidizing gas such as oxygen. By contacting the used catalyst with an oxidizing gas, the Cu can be oxidized back to CuO, which has low reaction activity.

[0036] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following, the examples are catalysts within the scope of the present disclosure (the present catalyst), and the comparative examples are catalysts outside the scope of the present disclosure.

[0037] <Measurement> (Measurement of the average distance between Cu and Zn) 0.1 g of the catalysts from the examples and comparative examples were passed through 5 vol% hydrogen / argon gas at 50 mL / min and heated to 300°C over 100 minutes. Then, they were reduced at 300°C for 1 hour, cooled to 40°C, and then surface oxidized with 5 vol% oxygen / nitrogen gas. The samples after surface treatment were ultrasonically dispersed in ethanol, and this liquid was deposited onto a Mo grid with a support film for TEM observation, dried, and used as the analytical sample.

[0038] Using a transmission electron microscope (Talos 200F) equipped with an EDX detector, EDX elemental mapping measurement was performed at an acceleration voltage of 200 kV and an irradiation current of about 0.15 nA. The mapping measurement was carried out under the conditions that the size of 1 pixel is 0.3 nm × 0.3 nm or less, and the integration time per pixel is 3 msec or more.

[0039] Specifically, according to EDX elemental mapping measurement, a location where a stronger Cu-Kα ray than Zn-Kα ray is detected can be identified as a Cu region (a region of Cu atoms), and a location where a stronger Zn-Kα ray than Cu-Kα ray is detected can be identified as a Zn region (a region of Zn atoms).

[0040] Smoothing and contrast adjustment were performed on the obtained original image. Thereafter, binarized images of the Cu image and the Zn image were generated respectively. A Cu-Zn binarized image was generated by combining the binarized images of Cu and Zn. Velox, a software manufactured by Fei Corporation, was used for image processing of the mapping image.

[0041] Based on the generated mapping image, using a C language program, for each first pixel which is a pixel located in the Cu region, the distance to the second pixel which is the closest pixel from the center of each first pixel in the Zn region is derived, and the average value of each distance is taken as the average distance between Cu and Zn.

[0042] (Measurement of electrical conductivity of filtrate) The electrical conductivity (μS / cm) of the filtrate was measured at room temperature using ECTestr11+ manufactured by Toyotana Co., Ltd.

[0043] (Measurement of average pore diameter) The average pore diameter (nm) was obtained from results measured using the nitrogen adsorption method. Specifically, the measurement was performed using an automatic specific surface area / pore size distribution measuring device "BELSORP-mini X" manufactured by Microtrac Bell Inc. The surface area measurement in this measurement was performed using the BET method. A sample that had been subjected to constant temperature vacuum drying at 120°C for 2 hours was used as the catalyst subjected to the measurement. Nitrogen gas was used as the processing gas, and liquid nitrogen temperature was used as the processing temperature.

[0044] Specific surface area (m ２ / g) was obtained by analysis in the relative pressure range of p / p0 = 0.1000 to 0.2500. Total pore volume (cm３ / g) was determined from the nitrogen adsorption capacity up to a relative pressure p / p0 = 0.9900. The pore diameter (nm) was calculated from the values of the BET specific surface area and the total pore volume, assuming cylindrical pores.

[0045] <Preparation of Catalyst> The catalyst according to the present disclosure will be described using Examples and Comparative Examples.

[0046] (Example 1: Catalyst E1) 49.8 g of copper sulfate pentahydrate, 22.1 g of zinc sulfate heptahydrate, and 1.27 g of gallium nitrate n-hydrate were dissolved in 203 g of pure water to prepare Solution A. Separately from Solution A, 38.6 g of dense soda ash was dissolved in 219 g of pure water to prepare Solution B. Further separately from Solution A and Solution B, 11.5 g of Alumina Sol 200 (manufactured by Nissan Chemical Corporation) was suspended in 350 g of pure water to prepare Solution C. Solution C was prepared in a glass separable flask equipped with a stirrer.

[0047] After heating Solution C to 70°C while stirring, 2.3 g of tantalum chloride and Solution B were added to adjust the pH to 6.6. Next, Solution A was dropped into the flask at a rate of 9.4 g / min, and Solution B was dropped such that the pH in the flask was maintained within the range of 6.4 to 6.8. When the entire amount of Solution A had been dropped, the supply of Solution B was stopped, and stirring was continued at 70°C for 5 hours and 40 minutes.

[0048] Next, the obtained precipitate was filtered and washed with pure water until the electrical conductivity of the filtrate became 100 µS / cm or less. The recovered wet cake was dried at 120°C, and then calcined in air at 300°C for 6 hours. A load was applied to the calcined powder to form a disk. After crushing the obtained disk with a pestle, granules having a size of 0.5 mm to 1.7 mm were collected using a wire mesh to obtain Catalyst E1. The average distance between Cu and Zn determined by STEM-EDX was 2.07 nm. The average pore diameter determined by the nitrogen gas adsorption method was 11.9 nm.

[0049] (Example 2: Catalyst E2) Solution A was prepared by dissolving 96.0 g of copper nitrate trihydrate, 12.0 g of aluminum nitrate nonahydrate, and 3.2 g of samarium nitrate hexahydrate in 40 g of pure water. Separately from Solution A, Solution B was prepared by dissolving 43.0 g of soda ash (dense) in 244 g of pure water. Further separately from Solutions A and B, Solution C was prepared by dissolving 22.9 g of zinc nitrate hexahydrate in 80 g of pure water.

[0050] Next, 350 g of pure water was added to a glass separable flask equipped with a stirrer, and the temperature was raised to 70°C while stirring. Then, solution B was added to adjust the pH to 6.5. Next, solution A was added dropwise into the separable flask at a rate of 5.1 g / min, while solution B was added dropwise to maintain the pH at 6.3. After all of solution A had been added, solution C was added dropwise at a rate of 3.4 g / min while continuing to add solution B to maintain the pH at 6.3. After all of solution C had been added, the supply of solution B was stopped, and stirring was continued at 70°C for 1.5 hours. The resulting precipitate was filtered and washed with pure water until the electrical conductivity of the filtrate was 100 μS / cm or less. The recovered wet cake was dried at 120°C and then baked in air at 300°C for 6 hours. A disc was formed by applying a load to the baked powder. The obtained disc was crushed with a pestle, and then catalyst E2 was obtained by separating granules ranging from 0.5 mm to 1.7 mm using a wire mesh. The average distance between Cu and Zn, determined by STEM-EDX, was 1.72 nm. The average pore diameter, determined by nitrogen gas adsorption, was 15.7 nm.

[0051] (Example 3: Catalyst E3) 22.9 g of zinc nitrate hexahydrate, 12.0 g of aluminum nitrate nonahydrate, and 3.2 g of samarium nitrate hexahydrate were added to a glass separable flask equipped with a stirrer, and dissolved in 296 g of pure water to prepare solution A. Separately, 50.0 g of soda ash (dense) was dissolved in 283 g of pure water to prepare solution B.

[0052] After raising the temperature of solution A to 70°C while stirring, solution B was added to adjust the pH to 6.5. Next, a 50% by mass aqueous solution of copper nitrate trihydrate was added dropwise at a rate of 3.2 g / min, while solution B was added dropwise at a rate of 11.1 g / min. After all of the 50% by mass aqueous solution of copper nitrate trihydrate and solution B had been added dropwise, stirring was continued at 70°C for 1.5 hours.

[0053] Next, the obtained precipitate was filtered and washed with pure water until the electrical conductivity of the filtrate was 100 μS / cm or less. The recovered wet cake was dried at 120°C and then calcined in air at 300°C for 6 hours. A load was applied to the calcined powder to create a disc. The obtained disc was crushed with a pestle, and then granules ranging from 0.5 mm to 1.7 mm were separated using a wire mesh to obtain catalyst E3. The average distance between Cu and Zn, determined by STEM-EDX, was 1.60 nm. The average pore diameter, determined by nitrogen gas adsorption, was 11.2 nm.

[0054] (Example 4: Catalyst E4) Solution A was prepared by dissolving 61.6 g of copper sulfate pentahydrate, 8.8 g of zinc sulfate heptahydrate, and 0.9 g of samarium nitrate hexahydrate in 40 g of pure water. Separately from Solution A, Solution B was prepared by dissolving 50.0 g of dense soda ash in 283 g of pure water. Further separately from Solutions A and B, Solution C was prepared by suspending 12.7 g of alumina sol 520A (manufactured by Nissan Chemical Corporation) in 350 g of pure water. Solution C was prepared in a glass separable flask equipped with a stirrer.

[0055] After raising the temperature of solution C to 70°C while stirring, solution A was added dropwise at a rate of 9.1 g / min, and simultaneously, solution B was added dropwise to maintain the pH of solution C at 6.3. Once the entire volume of solution A had been added, the supply of solution B was stopped, and stirring was continued at 70°C for 1.5 hours.

[0056] The obtained precipitate was filtered and washed with pure water until the electrical conductivity of the filtrate was 100 μS / cm or less. The recovered wet cake was dried at 120°C and then calcined in air at 300°C for 6 hours. A disc was formed by applying a load to the calcined powder. The obtained disc was crushed with a pestle, and then granules ranging from 0.5 mm to 1.7 mm were separated using a wire mesh to obtain catalyst E4. The average distance between Cu and Zn, determined by STEM-EDX, was 2.47 nm. The average pore diameter, determined by nitrogen gas adsorption, was 9.3 nm.

[0057] (Example 5: Catalyst E5) Solution A was prepared by dissolving 61.6 g of copper sulfate pentahydrate, 8.8 g of zinc sulfate heptahydrate, and 1.5 g of samarium nitrate hexahydrate in 200 g of pure water. Separately from Solution A, Solution B was prepared by dissolving 75.0 g of dense soda ash in 425 g of pure water. Further separately from Solutions A and B, Solution C was prepared by suspending 12.7 g of alumina sol 200 (manufactured by Nissan Chemical Corporation) in 250 g of pure water. Solution C was prepared in a glass separable flask equipped with a stirrer. Further separately from Solutions A, B and C, Solution D was prepared by dissolving 14.8 g of oxalic acid in 300 g of pure water.

[0058] After raising the temperature of solution C to 70°C while stirring, solutions A and D were simultaneously added dropwise at rates of 14.4 g / min and 10.5 g / min, respectively. At the same time, solution B was added dropwise to maintain the pH of solution C at 6.3. Once all of solutions A and D had been added dropwise, the supply of solution B was stopped, and stirring was continued at 70°C for 1.5 hours.

[0059] The obtained precipitate was filtered and washed with pure water until the electrical conductivity of the filtrate was 100 μS / cm or less. The recovered wet cake was dried at 120°C and then calcined in air at 300°C for 6 hours. A disc was formed by applying a load to the calcined powder using a 30 mm diameter pestle. The obtained disc was crushed with a mortar and pestle, and then catalyst E5 was obtained by separating granules ranging from 0.5 mm to 1.7 mm using a wire mesh. The average distance between Cu and Zn, determined by STEM-EDX, was 2.07 nm. The average pore diameter, determined by nitrogen gas adsorption, was 9.7 nm.

[0060] (Comparative Example 1: Catalyst C1) Solution A was prepared by dissolving 49.8 g of copper nitrate trihydrate, 22.1 g of zinc nitrate hexahydrate, and 0.9 g of samarium sulfate octahydrate in 182 g of pure water. Separately from Solution A, Solution B was prepared by dissolving 41.2 g of dense soda ash in 234 g of pure water. Further separately from Solutions A and B, Solution C was prepared by suspending 25.3 g of alumina sol 520A (manufactured by Nissan Chemical Corporation) in 350 g of pure water. Solution C was prepared in a glass separable flask equipped with a stirrer.

[0061] After raising the temperature of solution C to 70°C while stirring, solution B was added to adjust the pH to 6.6. Next, solution A was added dropwise at a rate of 8.50 g / min while solution B was added dropwise to maintain the pH in the range of 6.4 to 6.8. Once all of solution A had been added dropwise, the supply of solution B was stopped, and stirring was continued at 70°C for 3.5 hours.

[0062] Next, the obtained precipitate was filtered and washed with pure water until the electrical conductivity of the filtrate was 100 μS / cm or less. The recovered wet cake was dried at 120°C and then calcined in air at 300°C for 6 hours. A disc was formed by applying a load to the calcined powder. The obtained disc was crushed with a pestle, and then catalyst C1 was obtained by separating granules ranging from 0.5 mm to 1.7 mm using a wire mesh. The average distance between Cu and Zn, determined by STEM-EDX, was 3.30 nm. The average pore diameter, determined by nitrogen gas adsorption, was 10.1 nm.

[0063] (Comparative Example 2: Catalyst C2) Solution A was prepared by dissolving 96.0 g of copper nitrate trihydrate, 22.9 g of zinc nitrate hexahydrate, 18.6 g of aluminum nitrate nonahydrate, and 0.9 g of samarium nitrate hexahydrate in 118 g of pure water. Separately from Solution A, Solution B was prepared by dissolving 45.4 g of dense soda ash in 257 g of pure water. Next, 350 g of pure water was added to a glass separable flask equipped with a stirrer, and after heating to 70°C while stirring, Solution B was added to adjust the pH to 6.6. Then, Solution A was added dropwise at a rate of 8.53 g / min, and at the same time, Solution B was added dropwise to maintain the pH in the range of 6.4 to 6.8. After the entire volume of Solution A had been added dropwise, the supply of Solution B was stopped, and stirring was continued at 70°C for 3 hours and 10 minutes.

[0064] Next, the obtained precipitate was filtered and washed with pure water until the electrical conductivity of the filtrate was 100 μS / cm or less. The recovered wet cake was dried at 120°C and then calcined in air at 300°C for 6 hours. A disc was formed by applying a load to the calcined powder. The resulting disc was crushed with a pestle, and then catalyst C2 was obtained by separating granules ranging from 0.5 mm to 1.7 mm using a wire mesh. The average distance between Cu and Zn, determined by STEM-EDX, was 2.95 nm. The average pore diameter, determined by nitrogen gas adsorption, was 17.7 nm.

[0065] (Comparative Example 3: Catalyst C3) Solution A was prepared by dissolving 96.0 g of copper nitrate trihydrate, 22.9 g of zinc nitrate hexahydrate, and 0.9 g of samarium nitrate hexahydrate in 131 g of pure water. Separately from Solution A, Solution B was prepared by dissolving 45.4 g of dense soda ash in 257 g of pure water. Further separately from Solutions A and B, Solution C was prepared by suspending 25.3 g of alumina sol 200 (manufactured by Nissan Chemical Corporation) in 350 g of pure water. Solution C was prepared in a glass separable flask equipped with a stirrer.

[0066] After raising the temperature of solution C to 70°C while stirring, solution B was added to adjust the pH to 7.0. Next, solution A was added dropwise at a rate of 8.36 g / min while solution B was added dropwise to maintain the pH at 6.3. Once the entire volume of solution A had been added, the supply of solution B was stopped, and stirring was continued at 70°C for 1.5 hours while adding 1 mol / L nitric acid dropwise to maintain the pH at 6.3.

[0067] Next, the obtained precipitate was filtered and washed with pure water until the electrical conductivity of the filtrate was 100 μS / cm or less. The recovered wet cake was dried at 120°C and then calcined in air at 300°C for 6 hours. A disc was formed by applying a load to the calcined powder. The resulting disc was crushed with a pestle, and then catalyst C3 was obtained by separating granules ranging from 0.5 mm to 1.7 mm using a wire mesh. The average distance between Cu and Zn, determined by STEM-EDX, was 1.54 nm. The average pore diameter, determined by nitrogen gas adsorption, was 9.9 nm.

[0068] <Activity Evaluation> 3 g of the catalyst obtained above was packed into a reaction tube, and hydrogen gas was flowed through the catalyst layer at atmospheric pressure at 14 mL / min and argon at 266 mL / min. The temperature was raised to 300°C, and the reduction reaction was carried out for 2 hours. After that, it was cooled to room temperature. The pressure was increased to 0.9 MPaG with argon, and the temperature was raised to 160°C while flowing 80 mL / min. Then the argon was stopped, and a mixed gas of 24 vol% carbon dioxide, 72 vol% hydrogen, and 4 vol% argon was flowed at 200 mL / min. The temperature was raised to 200°C, and the reaction was carried out. The post-reaction gas 4.5 to 5 hours after the reaction was analyzed by gas chromatography. The methanol production rate was determined by subtracting the carbon monoxide production rate from the carbon dioxide consumption rate, and the methanol selectivity was determined by dividing the methanol production rate by the carbon dioxide consumption rate.

[0069] Table 1 below summarizes the results for the average distance between Cu and Zn, methanol selectivity, and average pore diameter for each example and comparative example. Figure 2 is a graph showing the relationship between the average distance between Cu and Zn, obtained from STEM-EDX mapping images, and methanol selectivity for each example and comparative example.

[0070]

[0071] From the results described above, it has been demonstrated that the examples within the scope of this disclosure exhibit improved methanol selectivity compared to the comparative examples.

[0072] Furthermore, a comparison of E1-E3 in the examples with E4 and E5 demonstrated that catalysts with an average distance between Cu and Zn of 1.55 nm to 2.90 nm and an average pore diameter of 11 nm to 17 nm exhibited improved methanol selectivity.

[0073] [Additional Notes] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0074] [Summary] (1) The catalyst according to Embodiment 1 of the present disclosure is a catalyst used in a reaction that includes a carbon oxide as a raw material, and contains copper atoms and zinc atoms, wherein the average distance between copper and zinc calculated from the mapping image of copper atoms and zinc atoms obtained by scanning transmission electron microscopy energy dispersive X-ray spectroscopy is 1.55 nm or more and 2.90 nm or less.

[0075] (2) The catalyst according to Embodiment 2 of the present disclosure is, in Embodiment 1, in which regions of copper atoms and regions of zinc atoms are identified in the mapping image, and the average distance between copper and zinc is the average value obtained by deriving the distance from the center of each first pixel, which is a pixel located in the region of copper atoms, to the second pixel, which is the closest pixel in the region of zinc atoms.

[0076] (3) The catalyst according to embodiment 3 of the present disclosure has an average pore diameter of 11 nm or more and 17 nm or less, as measured by the nitrogen gas adsorption method, in embodiment 1 or 2 above.

[0077] (4) A method for producing methanol according to aspect 4 of the present disclosure includes the step of contacting a raw material gas containing a carbon oxide and hydrogen with a catalyst according to any one of claims 1 to 3 to obtain methanol.

[0078] (5) The method for producing methanol according to Embodiment 5 of the present disclosure is, in Embodiment 4 above, wherein the carbon oxide is carbon dioxide.

Claims

1. A catalyst for use in a reaction involving carbon oxides as raw materials, comprising copper atoms and zinc atoms, wherein the average distance between copper and zinc, calculated from mapping images of copper and zinc atoms obtained by scanning transmission electron microscopy energy-dispersive X-ray spectroscopy, is between 1.55 nm and 2.90 nm.

2. The catalyst according to claim 1, wherein in the mapping image, regions of copper atoms and regions of zinc atoms are identified, and the average distance between copper and zinc is the average value obtained by deriving the distance from the center of each first pixel, which is a pixel located in the region of copper atoms, to the second pixel, which is the closest pixel in the region of zinc atoms, and for each first pixel, which is a pixel located in the region of copper atoms, and averaging the results.

3. The catalyst according to claim 1, wherein the average pore diameter measured by nitrogen gas adsorption is 11 nm or more and 17 nm or less.

4. A method for producing methanol, comprising the step of contacting a raw material gas containing carbon oxide and hydrogen with a catalyst according to any one of claims 1 to 3 to obtain methanol.

5. The method for producing methanol according to claim 4, wherein the carbon oxide is carbon dioxide.

Images