Catalyst for reverse water-gas shift reaction and method for producing the same, and method for producing carbon monoxide

Abstract

To provide a catalyst for reverse water-gas shift reaction for generating CO from CO2 and H2, the catalyst enabling acceleration of the reverse water-gas shift reaction under lower temperature conditions relative to the conventional art, while allowing suppression of a methanation reaction.SOLUTION: A catalyst for reverse water-gas shift reaction used for producing carbon monoxide from carbon dioxide and hydrogen comprises a support having a porous structure and a catalytic material supported on the support, the catalytic material containing nickel and zinc as catalytic active components, and the proportion of nickel relative to a total mass of nickel and zinc being 20 mass% or more and 85 mass% or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to catalysts for the reverse water gas shift reaction. [Background technology]

[0002] In recent years, carbon recycling has been proposed, in which CO2 (carbon dioxide), a type of greenhouse gas, is treated as a carbon resource and captured and reused. One method of carbon recycling is to generate CO (carbon monoxide) from CO2 and use that CO as an organic industrial raw material. The reverse water gas shift reaction, shown in the following equation (1), is known as a method for reducing CO2 to CO. The reverse water gas shift reaction is a reaction that generates CO and H2O (water) from CO2 and H2 (hydrogen) through the action of a catalyst. CO2+H2→CO+H2O...Equation (1)

[0003] The reverse water-gas shift reaction is an equilibrium reaction and an endothermic reaction. Therefore, high temperature conditions are advantageous for promoting the forward reaction of the reverse water-gas shift reaction, i.e., for driving the reaction to the right in the reaction formula (1). In the practically used reverse water-gas shift reaction using metals such as Cu (copper), Ni (nickel), and Pr (platinum) as catalysts, the reaction temperature is preferably high, at 600°C or higher, which poses a problem of high operating costs for the reaction equipment. Therefore, as in Patent Document 1, a reverse water-gas shift reaction catalyst that is highly reactive even under low-temperature reaction conditions has been proposed.

[0004] The reverse water gas shift reaction catalyst of Patent Document 1 is a reverse water gas shift reaction catalyst used to produce CO from CO2 and H2. The reverse water gas shift reaction catalyst comprises a metal oxide support, a composite oxide supported on the metal oxide support, and a metal catalyst, and is capable of activating the reverse water gas shift reaction at 100 to 400°C. The composite oxide includes, as a first metal oxide, an oxide of at least one metal element selected from the group consisting of Group 4 elements, Group 5 elements, and Group 6 elements, and, as a second metal oxide, an oxide of at least one metal element selected from the group consisting of Group 1 elements and Group 2 elements. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-058874 Summary of the Invention [Problem to be solved by the invention]

[0006] In the reverse water gas shift reaction, depending on the catalyst, methanation, a side reaction, can easily occur, resulting in the production of CH4 (methane) and a decrease in CO concentration, which is an issue.

[0007] The present disclosure has been made in consideration of the above circumstances, and its purpose is to provide a catalyst for reverse water-gas shift reaction (RWGR) for producing CO from CO and H, which can promote the RWGR under low-temperature conditions compared to conventional catalysts and can suppress the methanation reaction. [Means for solving the problem]

[0008] In order to solve the above problems, a reverse water gas shift reaction catalyst according to one embodiment of the present disclosure is a reverse water gas shift reaction catalyst used for producing carbon monoxide from carbon dioxide and hydrogen, comprising: A catalyst includes a carrier having a porous structure and a catalyst material supported on the carrier, The catalytic material contains nickel and zinc as catalytically active components, and the proportion of nickel to the total mass of nickel and zinc is 20 mass % or more and 85 mass % or less.

[0009] A method for producing a reverse water gas shift reaction catalyst according to one embodiment of the present disclosure includes dissolving a precursor containing a water-soluble salt of nickel and a water-soluble salt of zinc in water to prepare a precursor aqueous solution; impregnating a carrier with the aqueous precursor solution; drying the carrier impregnated with the precursor aqueous solution under reduced pressure; and calcining the support carrying the precursor; The proportion of nickel in the precursor relative to the total mass of nickel and zinc is 20% by mass or more and 85% by mass or less.

[0010] A method for producing carbon monoxide according to one embodiment of the present disclosure includes: a reverse water gas shift reaction step of contacting a feed gas containing carbon dioxide and hydrogen with the reverse water gas shift reaction catalyst to obtain a product gas containing carbon monoxide, The reaction temperature in the reverse water gas shift reaction step is 350°C or higher and 700°C or lower. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a catalyst for reverse water-gas shift reaction (RWGR) for producing CO from CO and H, which can promote the RWGR under low-temperature conditions and suppress the methanation reaction compared to conventional catalysts. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a performance evaluation test device. [Figure 2] FIG. 2 is a diagram showing the relationship between the mass fraction of Ni in the Ni—Zn-based catalyst material, the reverse water gas shift reaction activity, and the methanation reaction activity. DETAILED DESCRIPTION OF THE INVENTION

[0013] Next, embodiments of the present disclosure will be described. The following description is an exemplification for explaining the catalyst for the reverse water gas shift reaction according to the present disclosure, and the catalyst for the reverse water gas shift reaction according to the present disclosure is not limited to these disclosures.

[0014] 《Catalyst for Reverse Water Gas Shift Reaction》 The catalyst for the reverse water gas shift reaction according to the present disclosure is a catalyst that promotes the reverse water gas shift reaction for generating CO from CO2 and H2. The catalyst for the reverse water gas shift reaction is used, for example, for producing CO from CO2 and H2.

[0015] The active components of the catalyst for the reverse water gas shift reaction are Ni (nickel) and Zn (zinc). The catalyst for the reverse water gas shift reaction includes a Ni-Zn-based catalyst substance containing Ni and Zn, and a carrier supporting the catalyst substance. The catalyst for the reverse water gas shift reaction may optionally contain other components such as a molding aid.

[0016] <Carrier> The carrier has a carrier surface on which the catalyst substance is fixed. As the carrier, an oxide having a porous structure is preferable. The carrier having a porous structure has a large specific surface area and can contribute to improving the reactivity of the reverse water gas shift reaction. The carrier is not limited as long as it has a porous structure. Examples of the carrier material include SiO2 (silica), Al2O3 (aluminum oxide, alumina), MgO (magnesium oxide, magnesia), silica-alumina, silica-magnesia, TiO2 (titanium oxide), ZrO2 (zirconium oxide), zeolite, and activated carbon. The carrier may be in powder form or in a molded form such as a spherical or cylindrical shape.

[0017] <Ni-Zn-based Catalyst Substance> The catalyst substance contains Ni and Zn as catalyst active components. The catalyst substance may include an alloy of Ni and Zn.

[0018] From the viewpoint of excellent reactivity in the reverse water gas shift reaction, the content of the catalytic substance is preferably 3.0% by mass or more, and more preferably 5.0% by mass or more, where the total mass of the catalyst for the reverse water gas shift reaction (total mass = mass of the support + mass of the catalytic substance) is 100% by mass. Based on past experience, the content of the catalytic substance can be 50% by mass or less, and preferably 30% by mass or less. However, as the content of the catalytic substance increases, the degree of dispersion tends to decrease and the particle size tends to increase. Therefore, from the viewpoint of increasing the degree of dispersion, the content of the catalytic substance is preferably 10.0% by mass or less, and more preferably 8.0% by mass or less, of the total mass of the catalyst for the reverse water gas shift reaction.

[0019] The Ni content in the catalytic material is 20% by mass to 95% by mass, preferably 50% by mass to 85% by mass, where the total mass of the catalytic material (total mass = Ni mass + Zn mass) is 100% by mass. A catalytic material having such a Ni to Zn content ratio can activate the reverse aqueous shift reaction while suppressing the activity of the methanation reaction at a reaction temperature of approximately 500°C.

[0020] <<Method for producing a catalyst for reverse water gas shift reaction>> The reverse water gas shift reaction catalyst can be produced by impregnation. For example, the method for producing the reverse water gas shift reaction catalyst is as follows. (1) A precursor of a Ni-Zn-based catalyst material is mixed with distilled water to prepare a precursor aqueous solution. (2) The support is impregnated with the precursor aqueous solution. (3) The support impregnated with the precursor aqueous solution is dried under reduced pressure to remove water from the precursor aqueous solution and leave the precursor on the support surface. (4) The support with the precursor supported on its surface is calcined. By the above steps, a catalyst for reverse water gas shift reaction can be produced in which a Ni-Zn based catalytic material is supported on a carrier.

[0021] The precursor of the catalytic substance is a mixture of water-soluble salts of Ni and Zn. For example, a mixture of nickel (II) nitrate hexahydrate and zinc nitrate hexahydrate can be used as the precursor of the catalytic substance. The calcination temperature in the calcination step is preferably 300°C or higher and 600°C or lower. A calcination temperature of 300°C or higher tends to provide a catalyst with thermal stability sufficient for long-term use and high catalytic activity. The calcination time is not particularly limited, but is preferably 1 hour or higher and 24 hours or lower.

[0022] <<Method for producing carbon monoxide>> The method for producing carbon monoxide according to the present disclosure includes a reverse water-gas shift reaction step in which a feed gas containing CO and H is contacted with the reverse water-gas shift reaction catalyst to obtain a product gas containing CO, as shown in the following formula (2): CO2+H2→CO+H2O...Equation (2)

[0023] <Source gas> The source of the raw material gas is not limited as long as it contains CO2 and H2. The O2 in the raw material gas may be combustion exhaust gas generated from a process of burning hydrocarbons as fuel or a process of burning unreacted hydrocarbons in oil refineries, petrochemicals, power generation, steelmaking, boilers, etc. Furthermore, the CO2 in the raw material gas may be concentrated CO2 contained in gas.

[0024] <Reverse water gas shift reaction process> In the reverse water gas shift reaction step of the carbon monoxide production method, for example, a reaction vessel filled with a reverse water gas shift reaction catalyst is used, and the raw material gas is brought into contact with the reverse water gas shift reaction catalyst by flowing the raw material gas through the reaction vessel.

[0025] The temperature at which the feed gas is brought into contact with the reverse water-gas shift reaction catalyst is 350° C. or higher and 700° C. or lower, preferably 400° C. or higher and 600° C. or lower, and more preferably 450° C. or higher and 550° C. or lower. The reverse water-gas shift reaction catalyst according to the present disclosure exhibits catalytic activity even at low temperatures of 600° C. or lower, which are lower than conventional reaction temperatures, and can reduce the energy required for CO production.

[0026] [Example] EXAMPLES The present invention will be described in more detail below with reference to examples. In the examples, samples of catalysts for the reverse water gas shift reaction were prepared and performance evaluation tests were carried out on the samples.

[0027] <<Preparation of reverse water gas shift reaction catalyst samples>> A sample of a catalyst for the reverse water gas shift reaction was prepared according to the following procedure. (1) A precursor aqueous solution for the Ni-Zn catalyst was prepared. The precursor was a mixture of nickel (II) nitrate hexahydrate [Ni(ON3)2·6H2O: Fujifilm Wako Pure Chemical Industries, Ltd.] and zinc nitrate hexahydrate [Zn(ON3)2·6H2O: Fujifilm Wako Pure Chemical Industries, Ltd.]. The mass ratio of the nickel (II) nitrate hexahydrate and zinc nitrate hexahydrate precursors was determined so that the mass ratio of Ni to the total mass of Ni and Zn was a predetermined value. The precursor was mixed with distilled water to prepare a precursor aqueous solution. (2) Silica gel [SiO2: Fuji Silysia CAriACT Q-10 75-150 μm] was used as the support. The silica gel was placed in a 200 mL beaker, and the precursor aqueous solution was added dropwise to it. After every 5 or 6 drops of the precursor aqueous solution, the beaker was shook to mix the silica gel, or the silica gel was kneaded with a spatula to mix the silica gel, thereby obtaining silica gel impregnated with the precursor aqueous solution. (3) The silica gel impregnated with the precursor solution was placed in a beaker and the pressure was reduced in a rotary evaporator. (4) The silica gel impregnated with the precursor aqueous solution was dried in a beaker at 110°C for 10 hours or more under reduced pressure to remove water from the precursor aqueous solution. (5) The silica gel carrying the precursor was calcined at 400°C for 4 hours. By the above steps (1) to (5), a catalyst sample for reverse water gas shift reaction was obtained in which a Ni-Zn-based catalytic material was supported on silica gel. Several types of samples were prepared, with the mass ratio of Ni to the total mass of Ni and Zn being 0 mass%, 20 mass%, 50 mass%, 70 mass%, 80 mass%, 85 mass%, 90 mass%, 95 mass%, and 100 mass%.

[0028] Performance evaluation test A performance evaluation test was carried out using a performance evaluation test device to evaluate the catalytic performance of the prepared sample.

[0029] <Test equipment> FIG. 1 is a schematic diagram of a performance evaluation test apparatus 1. As shown in FIG. 1, the performance evaluation test apparatus 1 includes a reaction vessel 11, a heater 12, a raw material gas supply device 13, a separator 14, and a component analyzer 15. The reaction vessel 11 is a quartz cylinder having an inlet at one longitudinal end and an outlet at the other longitudinal end. A predetermined amount of catalyst 10 is loaded into the reaction vessel 11. The heater 12 heats the reaction vessel 11 so that the interior of the reaction vessel 11 reaches a predetermined reaction temperature. The raw material gas supply device 13 supplies a raw material gas to the inlet of the reaction vessel 11. The raw material gas is a mixed gas of H2 gas and CO2 gas. The raw material gas supply device 13 can adjust the flow rate of the raw material gas supplied to the reaction vessel 11. However, the raw material gas supply device 13 can switch the gas supplied to the reaction vessel 11 between only N2 and only H2. The separator 14 cools the reaction product gas discharged from the reaction vessel 11 and separates water vapor from the reaction product gas. The reaction product gas discharged from the reaction vessel 11 contains CO and water vapor, which are reaction products of the reverse water-gas shift reaction, as well as unreacted CO and H, and CH (methane) produced by the methanation reaction. The component analyzer 15 analyzes the contents of CO, CO, and CH in the reaction product gas from which water has been removed by the separator 14. The component analyzer 15 is, for example, a gas chromatograph.

[0030] <Test Method> The test method using the performance evaluation test device 1 having the above configuration is as follows. (1) 0.5 g of catalyst 10 was loaded into a reaction vessel 11. (2) After the inside of the reaction vessel 11 was replaced with N2, H2 was supplied to the reaction vessel 11 at 100 NmL / min. (3) The temperature inside the reaction vessel 11 was raised to 500° C. by the heater 12, and then maintained at that temperature for 1 hour. (4) While maintaining the inside of the reaction vessel 11 at atmospheric pressure and 500°C, the supply of the raw material gas was started by the raw material gas supply device 13. The flow rate of the raw material gas at the inlet of the reaction vessel 11 was 100 NmL / min, and the H gas concentration of the raw material gas was 50 mol% and the CO gas concentration was 50 mol%. (5) After the moisture in the reaction product gas discharged from the reaction vessel 11 was removed by the separator 14, the content of each of the components CO2, CO, and CH4 in the reaction product gas was detected by the component analyzer 15. (6) The reverse water-gas shift reaction activity and methanation reaction activity of the catalyst sample were determined from the component analysis results of the component analyzer 15. To calculate the reaction activity, we used "FactSage," a software developed by Computational Mechanics Research Center, Inc., which quantitatively predicts thermodynamic equilibrium states. Reaction engineering models were constructed for each of the reverse water-gas shift reaction activity and methanation reaction activity, and the model parameters that best reproduced the experimental data were defined as the reaction activity. Specifically, the reverse water-gas shift reaction activity was determined using the software to determine the pressure equilibrium constant of the reverse water-gas shift reaction that best reproduced the experimental data, and this pressure equilibrium constant was defined as the reverse water-gas shift reaction activity. Furthermore, the methanation reaction activity was determined using the software to determine the pressure equilibrium constant of the methanation reaction that best reproduced the experimental data, and this pressure equilibrium constant was defined as the methanation reaction activity.

[0031] <Test Results> Figure 2 is a diagram showing the relationship between the mass fraction of Ni in a Ni-Zn-based catalytic material, the reverse water gas shift reaction activity, and the methanation reaction activity. In the diagram of Figure 2, the horizontal axis represents the mass fraction of Ni relative to the total mass of the catalytic material, the left vertical axis represents the reverse water gas shift reaction activity of the catalyst, and the right vertical axis represents the methanation reaction activity of the catalyst. As is clear from the diagram of Figure 2, the methanation reaction activity of the catalyst remains roughly flat and does not change significantly up to a mass fraction of Ni in the catalytic material of 95 mass%, but increases rapidly once the mass fraction exceeds 95 mass%. Furthermore, the reverse water gas shift reaction activity of the catalyst increases gradually up to a mass fraction of Ni in the catalytic material of 95 mass%, and then increases rapidly once the mass fraction exceeds 95 mass%.

[0032] The above test results clearly show that the reverse water gas shift reaction catalyst according to the present disclosure can activate the reverse water gas shift reaction at a temperature of 500°C, which is lower than the conventional temperature of 600-700°C. Furthermore, the above test results clearly show that the reverse water gas shift reaction catalyst according to the present disclosure can suppress the methanation reaction when the Ni mass fraction of the Ni in the Ni-Zn-based catalytic material is 95 mass% or less, and that the reverse water gas shift reaction activity increases as the Ni mass fraction of the Ni-Zn-based catalytic material increases. Considering both the reaction stability and the amount of CO produced, the Ni mass fraction of the Ni in the Ni-Zn-based catalytic material is preferably in the range of 20 mass% to 95 mass%, more preferably 50 mass% to 85 mass%.

[0033] [Summary] A reverse water gas shift reaction catalyst according to a first aspect of the present disclosure is a reverse water gas shift reaction catalyst used for producing carbon monoxide from carbon dioxide and hydrogen, comprising: A catalyst includes a carrier having a porous structure and a catalyst material supported on the carrier, The catalytic material contains nickel and zinc as catalytically active components, and is characterized in that the ratio of nickel to the total mass of nickel and zinc is 20% by mass or more and 85% by mass or less.

[0034] A reverse water gas shift reaction catalyst according to a second aspect of the present disclosure is the reverse water gas shift reaction catalyst according to the first aspect, wherein the catalytic material has a ratio of nickel to the total mass of nickel and zinc of 50 mass% or more and 85 mass% or less.

[0035] A reverse water gas shift reaction catalyst according to a third aspect of the present disclosure is the reverse water gas shift reaction catalyst according to the first or second aspect, wherein the proportion of the catalytic material relative to the total mass of the reverse water gas shift reaction catalyst is 3 mass% or more and 50 mass% or less.

[0036] A method for producing a reverse water gas shift reaction catalyst according to a fourth aspect of the present disclosure includes the steps of: preparing a precursor aqueous solution by dissolving a precursor containing a water-soluble salt of nickel and a water-soluble salt of zinc in water; impregnating a carrier with the aqueous precursor solution; drying the carrier impregnated with the precursor aqueous solution under reduced pressure; and calcining the support carrying the precursor; The precursor is characterized in that the proportion of nickel relative to the total mass of nickel and zinc is 20% by mass or more and 85% by mass or less.

[0037] A method for producing carbon monoxide according to a fifth aspect of the present disclosure includes: a reverse water gas shift reaction step of contacting a feed gas containing carbon dioxide and hydrogen with the reverse water gas shift reaction catalyst according to any one of items 1 to 3 to obtain a product gas containing carbon monoxide, The reaction temperature of the reverse water gas shift reaction step is 350°C or higher and 700°C or lower.

[0038] The reverse water-gas shift reaction catalyst, its manufacturing method, and carbon monoxide manufacturing method according to the present disclosure can activate the reverse water-gas shift reaction at a lower temperature than conventional catalysts, thereby reducing the energy and costs involved in carbon monoxide production. Furthermore, the methanation reaction can be suppressed, increasing the amount of CO produced as a product and suppressing the production of CH4 as a by-product.

Claims

1. A catalyst for a reverse water gas shift reaction used to produce carbon monoxide from carbon dioxide and hydrogen, comprising: A catalyst includes a carrier having a porous structure and a catalyst material supported on the carrier, the catalytic substance contains nickel and zinc as catalytically active components, and the ratio of nickel to the total mass of nickel and zinc is 20 mass% or more and 85 mass% or less; Catalyst for the reverse water gas shift reaction.

2. The catalytic substance has a nickel content of 50% by mass or more and 85% by mass or less relative to the total mass of nickel and zinc. The reverse water gas shift reaction catalyst according to claim 1.

3. a ratio of the catalytic substance to the total mass of the reverse water gas shift reaction catalyst is 3 mass% or more and 50 mass% or less; The reverse water gas shift reaction catalyst according to claim 1 or 2.

4. preparing a precursor aqueous solution by dissolving a precursor containing a water-soluble salt of nickel and a water-soluble salt of zinc in water; impregnating a carrier with the aqueous precursor solution; drying the carrier impregnated with the precursor aqueous solution under reduced pressure; and calcining the support carrying the precursor; The ratio of nickel to the total mass of nickel and zinc in the precursor is 20% by mass or more and 85% by mass or less. A method for producing a catalyst for the reverse water gas shift reaction.

5. a reverse water gas shift reaction step of contacting a feed gas containing carbon dioxide and hydrogen with the reverse water gas shift reaction catalyst according to claim 1 to obtain a product gas containing carbon monoxide, The reaction temperature of the reverse water gas shift reaction step is 350°C or higher and 700°C or lower. Carbon monoxide production method.

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