Methanol synthesis catalyst and method for producing methanol synthesis catalyst

Abstract

The present invention pertains to a methanol synthesis catalyst which has a material represented by general formula (1): A2Mo3N. In general formula (1), A is at least one metal that is selected from cobalt and nickel.

Description

methanol synthesis catalyst and method for producing methanol synthesis catalyst

[0001] This invention relates to a methanol synthesis catalyst and a method for producing a methanol synthesis catalyst. This application claims priority under Japanese Patent Application No. 2024-194979, filed in Japan on November 7, 2024, the contents of which are incorporated herein by reference.

[0002] From the perspective of reducing carbon dioxide emissions, the synthesis reaction of methanol using carbon dioxide as a raw material is attracting attention. In this reaction, methanol can be synthesized using carbon dioxide and hydrogen as raw materials according to the following reaction equation: CO ２ +3H ２ →CH ３ OH + H ２ Currently, Cu-ZnO catalysts are used as catalysts for methanol synthesis reactions like this.

[0003] H. Sugiyama et. al. , "Room-Temperature CO2 Hydrogenation to Methanol over Air-Stable hcp-PdMo Intermetallic Catalyst," J. American Chem. Society, 2023, 145, 17, 9410-9416

[0004] The aforementioned Cu-ZnO catalysts have the problem of low activity at low temperatures. For this reason, Cu-ZnO catalysts must be used in high-temperature environments (for example, 250°C to 300°C).

[0005] On the other hand, the methanol synthesis reaction described above is an exothermic reaction, and the methanol yield tends to decrease at high temperatures. Therefore, there is a problem in that it is difficult to sufficiently increase the methanol yield in the operating conditions of conventional Cu-ZnO catalysts.

[0006] To address these issues, research and development on methanol synthesis at lower temperatures has been actively pursued in recent years. For example, Non-Patent Document 1 reports that PdMo intermetallic compounds can exhibit significantly higher methanol yields even at low temperatures.

[0007] However, even with the catalyst described in Non-Patent Document 1, the methanol yield at low temperatures is still not sufficient, and there is still a need for methanol synthesis catalysts that exhibit high activity at low temperatures.

[0008] This invention has been made in view of the above background, and aims to provide a methanol synthesis catalyst that can exhibit a significantly higher methanol yield even in low-temperature ranges compared to conventional methods. Furthermore, this invention aims to provide a method for producing such a methanol synthesis catalyst.

[0009] In this invention, a methanol synthesis catalyst is provided, which has the following general formula (1) A ２ Mo ３ A methanol synthesis catalyst is provided, comprising a material represented by N(1), wherein in the general formula (1), A is at least one metal selected from cobalt and nickel.

[0010] Furthermore, the present invention provides a method for producing a methanol synthesis catalyst, comprising: (I) mixing a solution containing either or both of a nickel compound and a cobalt compound with a solution containing a molybdenum compound to prepare a mixed solution; (II) drying the mixed solution to prepare a precipitate; and (III) nitriding the precipitate, wherein the methanol synthesis catalyst is defined by the following general formula (1) A ２ Mo ３ A method for producing a methanol synthesis catalyst is provided, comprising a material represented by N(1), wherein in the general formula (1), A is at least one metal selected from cobalt and nickel.

[0011] The present invention provides a methanol synthesis catalyst that can exhibit a significantly higher methanol yield even at low temperatures compared to conventional methods. Furthermore, the present invention provides a method for producing such a methanol synthesis catalyst.

[0012] The figure schematically shows the process for manufacturing a methanol synthesis catalyst according to an embodiment of the present invention. The figure shows the X-ray diffraction analysis results of the methanol synthesis catalyst according to an embodiment of the present invention. The graph shows the relationship between the methanol synthesis temperature and the amount of methanol produced for the methanol synthesis catalyst according to an embodiment of the present invention and a conventional methanol synthesis catalyst.

[0013] Hereinafter, an embodiment of the present invention will be described.

[0014] The methanol synthesis catalyst of the present embodiment has a material represented by the following general formula (1). A ２ Mo ３ N (1) In the general formula (1), A is at least one metal selected from cobalt and nickel.

[0015] As described above, the Cu-ZnO-based catalyst has low activity at low temperatures and is essential for use in a high-temperature environment. However, the methanol synthesis reaction is an exothermic reaction, and there is a problem that it is difficult to sufficiently increase the methanol yield on the high-temperature side.

[0016] Also, in the PdMo intermetallic compound catalyst described in Non-Patent Document 1, the methanol yield in the low-temperature range is still not sufficient.

[0017] In contrast, the methanol synthesis catalyst of the present embodiment can exhibit a significantly higher methanol yield in the low-temperature range compared to the prior art.

[0018] (Methanol synthesis catalyst) Hereinafter, the methanol synthesis catalyst of the present embodiment will be described in more detail.

[0019] (Composition) As described above, the methanol synthesis catalyst according to the present embodiment (hereinafter referred to as the "first catalyst") contains a material represented by the general formula (1) (hereinafter referred to as the "molybdenum nitride-based material"). A ２ Mo ３N (1) For example, the first catalyst may be composed of a molybdenum nitride-based material. In formula (1) above, the coefficient of A, 2, includes the range in which it becomes 2 when rounded to the first decimal place (i.e., 1.5 to 2.4). Similarly, the coefficient of Mo, 3, includes the range in which it becomes 3 when rounded to the first decimal place (i.e., 2.5 to 3.4). However, the sum of the coefficients of A and Mo is 5.

[0020] In the general formula (1) above, A is at least one metal selected from cobalt and nickel. The composition of the molybdenum nitride material can be confirmed using an inductively coupled plasma atomic emission spectrometer. Specifically, the composition can be confirmed by dissolving the molybdenum nitride material in a solvent that does not contain Mo, A, and N, and then performing inductively coupled plasma atomic emission spectrometry on the resulting solution.

[0021] For example, if A is nickel, then the molybdenum nitride-based material is Ni ２ Mo ３ It is represented by N. Note that A may be only one type, such as cobalt or nickel, or it may be both cobalt and nickel. In the case of two types, the sum of cobalt and nickel satisfies the coefficient of 2.

[0022] Molybdenum nitride-based materials preferably have a cubic crystal structure. ３ Al ２ It is more preferable that the material has a C-type crystal structure. The crystal structure of molybdenum nitride-based materials can be identified from the powder X-ray diffraction pattern obtained by powder X-ray diffraction measurement. Powder X-ray diffraction measurement is performed using a powder X-ray diffraction analyzer. Specifically, the molybdenum nitride-based material is filled into a dedicated substrate, and the measurement is performed using a Cu-Kα source to obtain the powder X-ray diffraction pattern.

[0023] (Form) The form of the first catalyst is not particularly limited. The first catalyst may be provided in the form of a powder, a film, or a bulk material.

[0024] Further, the first catalyst may consist only of a molybdenum nitride-based material, or may be provided in a state where the molybdenum nitride-based material is supported on a carrier. In this case, the shape of the carrier is not particularly limited, and the carrier may be plate-shaped or particulate.

[0025] For example, when the carrier is plate-shaped, the first catalyst may be in the form of a layer or powder and may be provided in a state supported on at least one main surface of the carrier.

[0026] When the carrier is in particulate form, the molybdenum nitride-based material may be supported on the surface of the carrier particles. In this case, the content of the molybdenum nitride-based material with respect to the total mass of the carrier particles and the molybdenum nitride-based material (i.e., the total mass of the methanol synthesis catalyst) may be 0.5% by mass or more and 11% by mass or less, or may be 0.5% by mass or more and 10% by mass or less.

[0027] Further, when the carrier is plate-shaped, the material of such a carrier is not particularly limited. On the other hand, when the carrier is in particulate form, examples of such a carrier include inorganic oxide carriers. Examples of inorganic oxide carriers include silicon oxide, aluminum oxide, titanium oxide, boron oxide, magnesium oxide, zirconium oxide, etc. Among them, silicon oxide is preferable, and silicon oxides such as SiO ２ etc. are more preferable. As will be described later, when silicon oxide is used for the carrier, the first catalyst can exhibit a higher methanol yield. The carrier may be used alone or in combination of two or more.

[0028] (Method for producing methanol synthesis catalyst) Next, referring to FIG. 1, an example of the method for producing the methanol synthesis catalyst of the present embodiment will be described.

[0029] FIG. 1 schematically shows the flow of the method for producing the methanol synthesis catalyst of the present embodiment (hereinafter referred to as "the first method").

[0030] As shown in FIG. 1, the first method includes: (I) a step of dissolving a molybdenum compound and a second metal compound in a solvent to prepare a raw material solution (step S110); (II) a step of drying the raw material solution to prepare a precipitate (step S120); and (III) a step of nitriding the precipitate (step S130).

[0031] The following describes each step.

[0032] In the following description, when A in the general formula (1) of the molybdenum nitride-based material contained in the methanol synthesis catalyst is nickel, that is, when the molybdenum nitride-based material contained in the first catalyst is Ni ２ Mo ３ The first method will be explained using the case where N is the element as an example. Therefore, the aforementioned "second metal compound" is a nickel compound.

[0033] However, the molybdenum nitride-based materials produced by the first method are not limited to these. That is, by using a cobalt compound in place of, or in addition to, the "nickel compound" described later in the first method, all molybdenum nitride-based materials represented by the aforementioned general formula (1) can be produced.

[0034] (Step S110) First, the molybdenum compound and the nickel compound are dissolved in a solvent to prepare the raw material solution.

[0035] The molybdenum compound is selected from, for example, ammonium heptamolybdate and molybdenum bis(acetylacetonate) oxide. The nickel compound is selected from, for example, nickel nitrate and nickel(II) acetate tetrahydrate. Nickel nitrate may also be used in hexahydrate form.

[0036] The concentration of the molybdenum compound in the raw material solution is, for example, in the range of 0.01% to 20% by mass. The concentration of the nickel compound in the raw material solution is, for example, in the range of 0.01% to 20% by mass.

[0037] The solvent may be water or an aqueous solution. If the solvent is an aqueous solution, the aqueous solution may contain an acid. Examples of such acids include nitric acid, citric acid, and malic acid.

[0038] When dissolving molybdenum compounds and nickel compounds, the solvent may be heated. The upper limit of the heating temperature is, for example, 80°C or lower.

[0039] Furthermore, a carrier may be added to the raw material solution. The carrier is preferably added in the form of particles.

[0040] The carrier may be composed of, for example, silicon dioxide. The average particle size of the carrier is, for example, in the range of 0.01 μm to 100 μm. The average particle size of the carrier can be measured by laser diffraction scattering. Specifically, a laser diffraction scattering particle size distribution analyzer is used to obtain a volume-based cumulative particle size distribution curve of the carrier. In the obtained cumulative particle size distribution curve, the value of the particle size at 50% accumulation from the fine particle side is taken as the average particle size.

[0041] (Step S120) Next, the raw material solution is dried to completely remove the solvent. The drying process may be carried out at room temperature or in a heated environment. If heated, the processing temperature is preferably in the range of 100°C to 200°C.

[0042] This allows us to obtain precipitates from the raw material solution.

[0043] (Step S130) Next, the obtained precipitate is subjected to nitriding treatment.

[0044] Furthermore, a pre-oxidation treatment may be performed on the precipitate before the nitriding treatment. By performing the pre-oxidation treatment, an oxide precursor containing molybdenum and nickel can be obtained.

[0045] Nitriding is carried out, for example, by heating the precipitate under an ammonia atmosphere. The heating temperature is, for example, in the range of 600°C to 800°C.

[0046] After step S130, Ni ２ Mo ３ A molybdenum nitride-based material represented by N can be obtained.

[0047] Furthermore, if carrier particles are added to the raw material solution in step S110 described above, a molybdenum nitride-based material supported on the surface of the carrier particles can be obtained.

[0048] Above, Ni ２ Mo ３ Using N material as an example, the method for producing the methanol synthesis catalyst of this embodiment was described by the first method.

[0049] However, in the first method, by changing the "nickel compound" to a cobalt compound, Co ２ Mo ３ It is obvious to those skilled in the art that methanol synthesis catalysts containing N material can be manufactured.

[0050] The following describes embodiments of the present invention. In the following description, Examples 1 and 2 are examples, and Example 11 is a comparative example.

[0051] (Example 1) Ni ２ Mo ３ A methanol synthesis catalyst containing N material was manufactured.

[0052] First, a mixed solution was prepared by placing 1.3086 g of ammonium heptamolybdate tetrahydrate, 1.4367 g of nickel nitrate hexahydrate, 4.7 g of anhydrous citric acid, 5 mL of 61% by mass concentrated nitric acid, and 45 mL of pure water into a 300 mL beaker. The mixed solution was then stirred at 80°C for 1 hour to completely dissolve the molybdenum salt and nickel salt.

[0053] Next, the mixed solution was held at 200°C for 1 hour to completely remove the water and obtain a precipitate.

[0054] Subsequently, the precipitate in the beaker was transferred to an alumina crucible, and the alumina crucible was heated in air at 500°C for 2 hours. This formed an oxide precursor containing molybdenum and nickel.

[0055] Next, this precursor was placed in a tubular furnace and heated at 700°C for 12 hours in an ammonia gas stream at a flow rate of 10 mL / min.

[0056] This yielded a powder (hereinafter referred to as "powder 1").

[0057] Figure 2 shows the results of the X-ray diffraction analysis of powder 1.

[0058] As shown in Figure 2, powder 1 is composed of Ni ２ Mo ３ It was found to contain N.

[0059] Here, the X-ray diffraction results do not show any peaks for the nickel-based composition added as a raw material, therefore, nickel is Mo ３ It is thought to be doped into N-based materials. Furthermore, the amount of nickel contained in the raw material was 0.4 (molar ratio) relative to the total amount of molybdenum and nickel, so palladium is Ni ２ Mo ３ As N, Mo ３ It is expected to be contained within N-type materials.

[0060] (Example 11) A methanol synthesis catalyst containing MoPd material was produced by the following method.

[0061] First, a mixed solution was prepared by placing 0.834 g of hexaammonium heptamolybdate tetrahydrate, 1.1603 g of palladium acetate, 3.8 g of anhydrous citric acid, 5 mL of 61% by mass concentrated nitric acid, and 45 mL of pure water into a 300 mL beaker. The mixed solution was then stirred at 80°C for 1 hour to completely dissolve the molybdenum salt and palladium salt.

[0062] Next, the mixed solution was held at 200°C for 1 hour to completely remove the water and obtain a precipitate.

[0063] Subsequently, the precipitate in the beaker was transferred to an alumina crucible, and the alumina crucible was heated in air at 500°C for 2 hours. This formed an oxide precursor containing molybdenum and palladium.

[0064] Next, this precursor was placed in a tubular furnace and heated at 750°C for 12 hours in an ammonia gas stream at a flow rate of 10 mL / min.

[0065] This yielded a powder (hereinafter referred to as "powder 11").

[0066] X-ray diffraction analysis revealed that powder 11 contains hcp-type PdMo. In other words, powder 11 does not contain A and N.

[0067] (Example 2) Ni ２ Mo ３ A methanol synthesis catalyst containing N material was manufactured.

[0068] A solution was prepared by placing 0.1309 g of ammonium heptamolybdate tetrahydrate, 0.1437 g of nickel nitrate hexahydrate, 0.5 g of anhydrous citric acid, 5 mL of 61% by mass concentrated nitric acid, and 45 mL of pure water into a 300 mL beaker. This solution was then stirred at 80°C for 1 hour to completely dissolve the molybdenum salt and nickel salt.

[0069] Subsequently, 0.9 g of crystalline silica particles (average particle size 100 μm) was added to this solution to prepare a mixed solution.

[0070] Next, the mixed solution was held at 200°C for 1 hour to completely remove the water and obtain a precipitate.

[0071] Subsequently, the precipitate in the beaker was transferred to an alumina crucible, and the alumina crucible was heated in air at 500°C for 2 hours. This formed an oxide precursor containing molybdenum and nickel.

[0072] Next, this precursor was placed in a tubular furnace and heated at 700°C for 12 hours in an ammonia gas stream at a flow rate of 10 mL / min.

[0073] This yielded a powder (hereinafter referred to as "powder 2").

[0074] Microscopic observation revealed that in powder 2, a Mo-Ni-N based material was supported on the surface of the silica particles. The content of the Mo-Ni-N based material relative to the total mass of the silica particles and the Mo-Ni-N based material (i.e., the total mass of the methanol synthesis catalyst) was 10% by mass.

[0075] Furthermore, based on the results of X-ray diffraction analysis, etc., powder 2 is Ni ２ Mo ３ It was inferred that it contained N.

[0076] (Evaluation) Methanol synthesis tests were conducted using each powder.

[0077] The test was conducted as follows:

[0078] First, 100 mg of each powder was weighed out and packed into a quartz glass tube.

[0079] Next, hydrogen gas was circulated through the quartz glass tube at a flow rate of 30 mL / min, and the quartz glass tube was heated at 300°C for 2 hours, then slowly cooled to activate the powder.

[0080] Next, the quartz glass tube was heated to a predetermined test temperature, and while maintaining this temperature, a mixture of hydrogen gas (30 mL / min), carbon dioxide gas (10 mL / min), and argon gas (10 mL / min) was circulated through the quartz glass tube.

[0081] The gases generated over two hours from the start of the reaction were collected and analyzed using gas chromatography (Agilent 7890A).

[0082] These tests were conducted at various test temperatures between 100°C and 200°C.

[0083] Table 1 below summarizes the test results obtained for each powder.

[0084]

[0085] In Table 1, "methanol production" was calculated by dividing the total amount of methanol measured by the amount of catalyst (excluding the support) and the reaction time.

[0086] Figure 3 also shows the relationship between methanol synthesis temperature and methanol production amount for powders 1 and 11.

[0087] These test results confirmed that powders 1 and 2 yielded higher methanol yields compared to powder 11 at synthesis temperatures ranging from 100°C to 200°C.

[0088] (Aspects of the present invention) The present invention has the following aspects.

[0089] (Aspect 1) A methanol synthesis catalyst, wherein the following general formula (1) A ２ Mo ３ A methanol synthesis catalyst having a material represented by N(1), wherein in the general formula (1), A is at least one metal selected from cobalt and nickel.

[0090] (Aspect 2) The methanol synthesis catalyst according to aspect 1, wherein the material is supported on the surface of carrier particles.

[0091] (Aspect 3) A method for producing a methanol synthesis catalyst, comprising: (I) mixing a solution containing either one or both of a nickel compound and a cobalt compound with a solution containing a molybdenum compound to prepare a mixed solution; (II) drying the mixed solution to prepare a precipitate; and (III) nitriding the precipitate, wherein the following general formula (1) A ２ Mo ３ A methanol synthesis catalyst represented by N(1) is obtained, wherein in the general formula (1), A is at least one metal selected from cobalt and nickel.

[0092] (Aspect 4) The method according to aspect 3, wherein the molybdenum compound is ammonium heptamolybdate or molybdenum bis(acetylacetonate) oxide.

[0093] (Aspect 5) The method according to aspect 3 or 4, wherein the nickel compound is nickel nitrate or nickel(II) acetate tetrahydrate.

[0094] (Aspect 6) The method according to any one of aspects 3 to 5, wherein the precipitate is treated in an ammonia-containing atmosphere at a temperature of 600°C to 800°C in the manner described in (III).

[0095] (Aspect 7) The method according to any one of aspects 3 to 6, wherein in (I), the mixed solution further comprises carrier particles, and after (III), a methanol synthesis catalyst supported on the carrier particles is obtained.

[0096] The methanol synthesis catalyst of the present invention is useful because it can exhibit a significantly higher methanol yield even at low temperatures compared to conventional catalysts.

Claims

1. A methanol synthesis catalyst, wherein the following general formula (1) A ２ Mo ３ A methanol synthesis catalyst having a material represented by N(1), wherein in the general formula (1), A is at least one metal selected from cobalt and nickel.

2. The methanol synthesis catalyst according to claim 1, wherein the material is supported on the surface of a carrier.

3. A method for producing a methanol synthesis catalyst, comprising: (I) mixing a solution containing either one or both of a nickel compound and a cobalt compound with a solution containing a molybdenum compound to prepare a mixed solution; (II) drying the mixed solution to prepare a precipitate; and (III) nitriding the precipitate, wherein the methanol synthesis catalyst is defined by the following general formula (1) A ２ Mo ３ A method for producing a methanol synthesis catalyst, comprising a material represented by N(1), wherein in the general formula (1), A is at least one metal selected from cobalt and nickel.

4. The method for producing a methanol synthesis catalyst according to claim 3, wherein the molybdenum compound is hexaammonium heptamolybdate or molybdenum bis(acetylacetonato) oxide.

5. The method for producing a methanol synthesis catalyst according to claim 3, wherein the nickel compound is nickel nitrate or nickel(II) acetate tetrahydrate.

6. The method for producing a methanol synthesis catalyst according to claim 3, wherein, in (III), the precipitate is treated in an ammonia-containing atmosphere at a temperature of 600°C to 800°C.

7. The method for producing a methanol synthesis catalyst according to claim 3, wherein, in (I) above, the mixed solution further comprises a carrier, and the methanol synthesis catalyst is a methanol synthesis catalyst in which the material is supported on the surface of the carrier.

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