Carbon dioxide reduction catalyst and method for producing higher hydrocarbon

Abstract

The present invention provides a carbon dioxide reduction catalyst with which it is possible to increase the adsorption amount of carbon dioxide.　This carbon dioxide reduction catalyst reduces carbon dioxide by hydrogenating carbon dioxide and hydrogen, the catalyst containing iron, gallium, and barium as catalyst metals, and the iron being the main component of the catalyst metals.

Description

Carbon dioxide reduction catalyst and method for producing higher hydrocarbons

[0001] The present invention relates to a carbon dioxide reduction catalyst and a method for producing higher hydrocarbons.

[0002] Efforts aimed at mitigating or reducing the impact of climate change have been ongoing, and toward this end, automobile exhaust gas regulations have been further advanced. In particular, there is a demand for reducing the amount of carbon dioxide emissions contained in exhaust gases from internal combustion engines. In recent years, technologies for producing fuel by subjecting carbon dioxide to a hydrogenation reaction have become known. For example, a catalyst composed of Cu, Zn, and alumina has been proposed as a catalyst for synthesizing methanol from a mixed gas of carbon dioxide and hydrogen (see Patent Document 1).

[0003] However, it is desired to be able to produce hydrocarbons having, for example, 5 or more carbon atoms that can be used as liquid fuels as fuels obtained by hydrogenating carbon dioxide. As a technology for achieving this, a method has been proposed in which potassium is used as a promoter for an Fe catalyst in a Fischer-Tropsch (FT) synthesis reaction to prepare highly branched products having 5 or more carbon atoms (see Patent Document 2).

[0004] Special Publication No. 45-16682 Special Publication No. 2005-537340

[0005] Meanwhile, in efforts to reduce carbon dioxide emissions, attention has been focused on technology related to sustainable aviation fuel (SAF), which is an aviation fuel produced from biomass-derived materials or waste, or produced from hydrocarbons using carbon dioxide as a feed gas. It would be preferable if SAF could be produced directly from carbon dioxide using technology related to the hydrogenation reaction of carbon dioxide. The production of SAF requires an increase in the hydrocarbon production rate. After extensive research, the present inventors have found that an effective way to increase the hydrocarbon production rate is to adsorb a large amount of the carbon dioxide used as a feedstock onto a carbon dioxide reduction catalyst.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a carbon dioxide reduction catalyst that can increase the amount of carbon dioxide adsorbed.

[0007] In order to achieve the above object, the present invention provides the following means: [1] A carbon dioxide reduction catalyst that reduces carbon dioxide by subjecting carbon dioxide and hydrogen to a hydrogenation reaction, the carbon dioxide reduction catalyst containing iron, gallium, and barium as catalytic metals, with the iron being a main component of the catalytic metals.

[0008] The carbon dioxide reduction catalyst according to [1] contains iron, gallium, and barium as catalytic metals, and thus can increase the amount of carbon dioxide adsorbed onto the catalyst in the hydrogenation reaction of carbon dioxide and hydrogen.

[0009] [2] The carbon dioxide reduction catalyst according to [1], which produces hydrocarbons by a hydrogenation reaction between carbon dioxide and hydrogen.

[0010] The carbon dioxide reduction catalyst according to [2] contains iron, gallium, and barium as catalytic metals, and thus can increase the amount of carbon dioxide adsorbed onto the catalyst in the hydrogenation reaction of carbon dioxide and hydrogen.

[0011] [3] The carbon dioxide reduction catalyst according to [1] or [2], wherein the gallium content is greater than the barium content.

[0012] The carbon dioxide reduction catalyst according to [3] contains iron as a main catalytic metal component, and contains gallium and barium as auxiliary catalysts in that order of content, thereby improving the basicity of iron and enabling the promotion of upgrading of hydrocarbons produced by the hydrogenation reaction of carbon dioxide and hydrogen.

[0013] [4] The carbon dioxide reduction catalyst according to any one of [1] to [3], wherein the content of the barium relative to the catalytic metal is 0.1 to 2.2 mass%.

[0014] The carbon dioxide reduction catalyst according to [4] has a barium content relative to the catalyst metal within a specific range, thereby making it possible to increase the production rate of hydrocarbons having 8 to 16 carbon atoms.

[0015] [5] The carbon dioxide reduction catalyst according to any one of [1] to [4], further containing sodium as an auxiliary catalyst in addition to the catalytic metal.

[0016] The carbon dioxide reduction catalyst according to [5] further contains sodium as an auxiliary catalyst in addition to the catalytic metal, which can further improve the basicity of iron, thereby further increasing the production rate of hydrocarbons having 8 to 16 carbon atoms.

[0017] [6] The carbon dioxide reduction catalyst according to any one of [1] to [5], further containing zirconium as the catalytic metal.

[0018] The carbon dioxide reduction catalyst according to [6] further contains zirconium as a catalytic metal, which can further improve the basicity of iron, thereby further increasing the production rate of hydrocarbons having 8 to 16 carbon atoms.

[0019] [7] The carbon dioxide reduction catalyst according to any one of [1] to [4], further containing sodium as an auxiliary catalyst in addition to the catalytic metal, and further containing zirconium as the metal catalyst.

[0020] The carbon dioxide reduction catalyst according to [7] further contains sodium as an auxiliary catalyst in addition to the catalytic metal, and further contains zirconium as a catalytic metal, which can further improve the basicity of iron, thereby further increasing the production rate of hydrocarbons having 8 to 16 carbon atoms.

[0021] [8] A method for producing higher hydrocarbons, comprising producing hydrocarbons having 8 to 16 carbon atoms from a feed gas containing carbon dioxide and hydrogen, using the carbon dioxide reduction catalyst according to any one of [1] to [7].

[0022] The method for producing higher hydrocarbons according to [8] uses the carbon dioxide reduction catalyst according to any one of [1] to [7]. As a result, in the hydrogenation reaction of carbon dioxide and hydrogen, the amount of carbon dioxide adsorbed to the catalyst can be increased, and the production rate of hydrocarbons having 8 to 16 carbon atoms can be increased. As a result, the production rate of hydrocarbons having 8 to 16 carbon atoms, which are the main components of synthetic jet fuel, can be increased, and synthetic jet fuel can be produced efficiently.

[0023] The carbon dioxide reduction catalyst of the present invention can increase the amount of carbon dioxide adsorbed to the catalyst, and the method for producing higher hydrocarbons of the present invention can efficiently produce synthetic jet fuels such as SAF.

[0024] 1 is a conceptual diagram showing an embodiment of a fuel synthesis device using a carbon dioxide reduction catalyst of the present invention; FIG. 2 is a conceptual diagram showing another embodiment of a fuel synthesis device using a carbon dioxide reduction catalyst of the present invention; FIG. 3 is a conceptual diagram showing the relationship between the amount of Ba added in the carbon dioxide reduction catalyst according to examples and comparative examples of the present invention and the CO ２ 1 is a graph showing the relationship between the amount of Ba added and the conversion rate in Examples and Comparative Examples. ８ -C １６ 1 is a graph showing the relationship between the amount of Ba added and the selectivity of hydrocarbons in Examples and Comparative Examples. ８ -C １６ 1 is a graph showing the relationship between the amount of Ba added and the rate of hydrocarbon production in Examples and Comparative Examples. ２ 10 is a graph showing the relationship between the amount of adsorption and the amount of water adsorbed.

[0025] Preferred embodiments of the present invention will now be described in detail.

[0026] [Carbon dioxide reduction catalyst] The carbon dioxide reduction catalyst of this embodiment is a catalyst that reduces carbon dioxide by subjecting carbon dioxide and hydrogen to a hydrogenation reaction. In addition, the carbon dioxide reduction catalyst of this embodiment is a catalyst that can produce hydrocarbons by subjecting carbon dioxide and hydrogen to a hydrogenation reaction. In particular, the carbon dioxide reduction catalyst of this embodiment can increase the production rate of hydrocarbons having 8 to 16 carbon atoms compared to conventional catalysts. In this specification, "higher hydrocarbons" refers to hydrocarbons having 8 or more carbon atoms. Hydrocarbons having 8 to 16 carbon atoms fall under the category of higher hydrocarbons.

[0027] The carbon dioxide reduction catalyst of this embodiment contains iron (Fe), gallium (Ga), and barium (Ba) as catalytic metals, with iron being the main component of the catalytic metal. Here, "mainly containing iron" means that the iron content is 50 mass% or more relative to the total mass of the catalytic metals in the carbon dioxide reduction catalyst.

[0028] The carbon dioxide reduction reaction using the carbon dioxide reduction catalyst according to this embodiment is carried out by H ２ (hydrogen) and CO ２ (carbon dioxide) mixed gas as raw material, ２ This is the so-called direct FT synthesis reaction, in which hydrocarbons are produced by carrying out, in a single stage, a reverse water-gas shift reaction in which CO is reduced to CO (carbon monoxide), and an FT synthesis reaction in which CO is converted into hydrocarbons. The carbon dioxide reduction catalyst according to this embodiment contributes to both the reverse water-gas shift reaction and the FT synthesis reaction. In addition, it can also be used in the so-called direct FT synthesis reaction.

[0029] Iron is contained as a catalytic metal in the carbon dioxide reduction catalyst and may be a compound such as an oxide, carbonate compound, nitrate compound, or sulfate compound, with an oxide being preferred. Two or more of these compounds may be contained. Furthermore, iron is more preferably contained in the catalytic metal as an iron-gallium composite oxide containing iron and gallium. Use of a catalytic metal containing an iron-gallium composite oxide can promote the growth of hydrocarbon carbon chains compared to compounds such as iron oxide.

[0030] The iron content relative to the total mass of catalytic metals in the carbon dioxide reduction catalyst is 50 mass % or more, preferably 50 to 75 mass %, and more preferably 60 to 70 mass %, calculated as metal atoms. By setting the iron content within this range, the amount of carbon dioxide adsorbed onto the catalyst in the hydrogenation reaction of carbon dioxide and hydrogen can be further increased.

[0031] The gallium contained in the catalytic metal according to this embodiment may be, like iron, in the form of a compound such as an oxide, a carbonate compound, a nitrate compound, or a sulfate compound, and is preferably an oxide. Two or more of these compounds may be contained. Gallium is more preferably contained in the catalytic metal as an iron-gallium composite oxide containing iron and gallium.

[0032] The gallium content relative to the total mass of the catalytic metals in the carbon dioxide reduction catalyst is preferably 10 to 30 mass %, and more preferably 15 to 25 mass %, calculated as metal atoms. When the gallium content is within this range, the catalytic activity of the carbon dioxide reduction catalyst can be further enhanced.

[0033] In the catalytic metal, the content of gallium is preferably greater than the content of barium, which will be described later. In the carbon dioxide reduction catalyst of this embodiment, both gallium and barium function as auxiliary catalysts. By including gallium and barium in order of decreasing content as auxiliary catalysts, the basicity of iron can be improved, and the upgrading of hydrocarbons produced by the hydrogenation reaction of carbon dioxide and hydrogen can be promoted.

[0034] Barium is contained as a catalytic metal in the carbon dioxide reduction catalyst, and like iron, it may be in the form of a compound such as an oxide, carbonate compound, nitrate compound, or sulfate compound, with an oxide being preferred. Barium is more preferably contained in the catalytic metal as an iron-gallium-barium composite oxide containing iron and gallium. Use of a catalytic metal containing an iron-gallium-barium composite oxide can promote the growth of carbon chains in hydrocarbons compared to compounds such as iron oxide.

[0035] When barium is contained in the carbon dioxide reduction catalyst together with iron and gallium, the basicity of barium can enhance the adsorption power of acidic carbon dioxide onto the catalyst. The content of barium relative to the total mass of catalytic metals in the carbon dioxide reduction catalyst is preferably more than 0 mass% and not more than 3 mass%, more preferably 0.1 to 2.2 mass%, in terms of metal atoms. When the barium content is equal to or greater than the above lower limit, CO ２ The adsorption power of the intermediate CH ２ When the barium content is equal to or less than the upper limit, it is possible to suppress a decrease in activity due to barium covering the reactive sites of iron.

[0036] The carbon dioxide reduction catalyst of this embodiment preferably further contains sodium (Na) in addition to the catalytic metal. Sodium functions as a co-catalyst (promoter) together with the catalytic metal containing iron, gallium, and barium. Sodium acts to convert carbon dioxide into sodium carbonate (Na ２ CO ３) promotes the reverse shift reaction in which carbon monoxide is produced from hydrogen and carbon dioxide, thereby further increasing the carbon dioxide conversion rate. Sodium is preferably present on the surface of the composite oxide in the form of an oxide or the like, separate from the composite oxide. By being present on the surface of the composite oxide, sodium functions as a surface catalyst. The carbon dioxide reduction catalyst may contain an alkali metal such as lithium (Li), potassium (K), rubidium (Rb), or cesium (Cs) in place of or together with sodium.

[0037] When the carbon dioxide reduction catalyst of this embodiment contains sodium, the content of sodium relative to the total mass of the catalytic metal in the carbon dioxide reduction catalyst is preferably 0.5 to 2.0 mass%, and more preferably 0.5 to 1.5 mass%, calculated as metal atoms. When the sodium content is equal to or greater than the above-mentioned lower limit, the basicity of the carbon dioxide reduction catalyst can be increased, and the efficiency of producing hydrocarbons having 8 to 16 carbon atoms can be sufficiently improved. When the sodium content is equal to or less than the above-mentioned upper limit, the adverse effects caused by sodium covering the iron reaction sites can be avoided, the production of carbon monoxide as a by-product can be suppressed, and a decrease in catalytic activity can be prevented.

[0038] The carbon dioxide reduction catalyst of this embodiment preferably further contains zirconium (Zr) as a catalytic metal. Zirconium functions as an auxiliary catalyst (promoter) in a catalytic metal containing iron, gallium, and barium. Zirconium can promote the carbidization of iron particles, thereby promoting carbon chain growth and further increasing the production rate of hydrocarbons having 8 to 16 carbon atoms. Like iron, zirconium may be in the form of a compound such as an oxide, carbonate, nitrate, or sulfate, and is preferably an oxide. Two or more of these compounds may be contained. Zirconium is more preferably contained in the catalytic metal as an iron-gallium-zirconium-barium composite oxide containing iron, gallium, barium, and zirconium. Using a catalytic metal containing an iron-gallium-zirconium-barium composite oxide can promote carbon chain growth compared to compounds such as iron oxide.

[0039] When the carbon dioxide reduction catalyst of this embodiment contains zirconium, the zirconium content relative to the total mass of catalytic metals in the carbon dioxide reduction catalyst is preferably more than 0 mass% and 15 mass% or less, and more preferably 5 to 15 mass%, calculated as metal atoms. When the zirconium content is equal to or greater than the above-mentioned lower limit, the carbidization of iron particles can be promoted, thereby accelerating the growth of carbon chains and further increasing the production rate of hydrocarbons having 8 to 16 carbon atoms. When the zirconium content is equal to or less than the above-mentioned upper limit, the adverse effects caused by zirconium covering iron reaction sites can be avoided, and a decrease in catalytic activity can be prevented.

[0040] The carbon dioxide reduction catalyst of this embodiment further contains sodium as an auxiliary catalyst in addition to the catalytic metal, and by further containing zirconium as the catalytic metal, the basicity of iron can be further improved and the production rate of hydrocarbons having 8 to 16 carbon atoms can be further increased. For this reason, the carbon dioxide reduction catalyst of this embodiment preferably further contains sodium as an auxiliary catalyst in addition to the catalytic metal, and further contains zirconium as the catalytic metal.

[0041] The carbon dioxide reduction catalyst of this embodiment may be, for example, a powder of catalytic metal, or a pellet-shaped molded body formed by pressure molding of catalytic metal. Alternatively, the catalyst may be supported on a known catalyst carrier such as silica. In addition to the above, the carbon dioxide reduction catalyst of this embodiment may contain inevitable impurities that are mixed in during the catalyst production process, etc., but it is preferable that the carbon dioxide reduction catalyst contain as few impurities as possible.

[0042] [Method for producing carbon dioxide reduction catalyst] The method for producing the carbon dioxide reduction catalyst of this embodiment preferably includes a coprecipitation step and an impregnation step.

[0043] <Coprecipitation Step> The coprecipitation step is a step of extracting a catalyst precursor precipitate by coprecipitation from an aqueous solution in which a predetermined amount of iron nitrate and at least one of gallium nitrate and barium nitrate are dissolved in distilled water. Iron-gallium-barium composite oxide is formed by the coprecipitation step. In the coprecipitation step, a precipitation solution is preferably obtained by adding a urea aqueous solution dropwise to the aqueous solution containing iron and at least one of gallium and barium. The precipitate is then separated from the precipitation solution by filtration, washing, or the like, and dried to obtain a catalyst precursor precipitate (iron-gallium-barium composite oxide). Note that in the coprecipitation step, zirconium nitrate may also be used to obtain an iron-gallium-zirconium-barium composite oxide.

[0044] <Impregnation Step> The impregnation step is a step of dropping an aqueous solution containing Na onto the precipitate obtained by the coprecipitation step, drying for a predetermined time, and firing the obtained powder at a predetermined temperature. The impregnation step allows the Na compound to be unevenly distributed near the surface of the composite oxide. Examples of the aqueous solution containing Na include NaNO ３ (sodium nitrate) aqueous solution. ３ The aqueous solution can be added dropwise under ultrasonic vibration. This allows the Na compound to be uniformly distributed near the surface of the composite oxide. The firing temperature can be, for example, 500 to 600°C, and the firing time can be 3 to 5 hours.

[0045] [Fuel synthesis device] When a carbon dioxide reduction reaction is carried out using the carbon dioxide reduction catalyst according to this embodiment, for example, a fuel synthesis device can be used. FIG. 1 is a conceptual diagram showing a schematic configuration of a fuel synthesis device using the carbon dioxide reduction catalyst according to this embodiment. As shown in FIG. 1, the fuel synthesis device 1 according to this embodiment includes a catalyst reaction vessel 20, a catalyst reaction vessel 30, and a water trap unit 40. The catalyst reaction vessel 20 and the catalyst reaction vessel 30 are connected by a flow path L. The water trap unit 40 is connected to the flow path L.

[0046] <Catalyst Reaction Vessel> The carbon dioxide reduction catalyst (C1) of this embodiment, which contains iron, gallium, and barium as catalytic metals, is placed in the catalyst reaction vessel 20. The carbon dioxide reduction catalyst (C2) of this embodiment, which contains iron, gallium, and barium as catalytic metals, similar to the catalyst reaction vessel 20, is placed in the catalyst reaction vessel 30.

[0047] There are no particular limitations on the configuration of the catalyst reactor 20 and the catalyst reactor 30, and any known configuration can be applied. For example, a fixed-bed flow-type reactor in which a flow path having a predetermined shape is filled with a powdery, granular, or pellet-like catalyst or a carrier carrying the catalyst can be mentioned.

[0048] <Water Trap Unit> The water trap unit 40 removes water from the fluid supplied to the carbon dioxide reduction catalyst. This makes it possible to shift the chemical equilibrium in the carbon dioxide reduction reaction by the carbon dioxide reduction catalyst in the direction of increasing the number of carbon atoms in hydrocarbons. This makes it possible to improve the yield of hydrocarbons with 8 to 16 carbon atoms.

[0049] The fuel synthesizer may be a fuel synthesizer 1' as shown in Fig. 2, in which a water trap unit 40' is connected to a catalyst reaction vessel 20'. The catalyst reaction vessel 20' and the water trap unit 40' shown in Fig. 2 are similar to the catalyst reaction vessel 20 and the water trap unit 40 described above, respectively.

[0050] [Method for Producing Higher Hydrocarbons] The method for producing higher hydrocarbons according to the present embodiment is not particularly limited as long as it uses the carbon dioxide reduction catalyst according to the present embodiment, and examples include a method for producing hydrocarbons having 8 to 16 carbon atoms from a feed gas containing carbon dioxide and hydrogen.

[0051] The method for producing higher hydrocarbons according to this embodiment uses the carbon dioxide reduction catalyst according to this embodiment. Therefore, in the hydrogenation reaction of carbon dioxide and hydrogen, the amount of carbon dioxide adsorbed onto the catalyst can be increased, and the production rate of hydrocarbons having 8 to 16 carbon atoms can be increased. As a result, the production rate of hydrocarbons having 8 to 16 carbon atoms, which are the main components of synthetic jet fuels such as SAF, can be increased, and synthetic jet fuel can be produced efficiently.

[0052] The present invention is not limited to the above-described embodiment, and includes modifications and improvements within the scope of achieving the object of the present invention.

[0053] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0054] [Preparation of Carbon Dioxide Reduction Catalyst] <Example 1> Iron nitrate (Fe(NO)) as a catalytic metal of a carbon dioxide reduction catalyst ３ ) ３ ・9H ２ O) and gallium nitrate (Ga(NO) ３ ) ３ ・6H ２ O) and zirconium nitrate (ZrO(NO) ３ ) ２ ・2H ２ O) and barium nitrate (Ba(NO)) as a catalytic metal. ３ ) ２ ) were weighed out so that the mass ratio of Fe:Ga:Zr:Ba was 6.7:2.2:1.0:0.1 in terms of metal atoms, and dissolved in distilled water to obtain an aqueous solution. Next, urea (CH ４ N ２ An aqueous solution of iron, gallium, zirconium, and barium was added dropwise at 2 ml / min and the pH was fixed at 8.5 (25°C), thereby obtaining a precipitate solution containing iron, gallium, zirconium, and barium as a precipitate. Next, the precipitate solution was aged at room temperature (25°C) for 24 hours, and then the precipitate was separated by repeated filtration and washing. The separated precipitate was dried at 60°C for 12 hours to obtain an iron-gallium-zirconium-barium catalyst precursor (Fe-Ga-Zr-Ba catalyst precursor). Sodium nitrate (NaNO) was added to the Fe-Ga-Zr-Ba catalyst precursor. ３ An aqueous solution of 1.0% by mass of Na, calculated as metal atoms, was added dropwise to the catalyst under 92 kHz ultrasonic vibration. The catalyst was then dried under a vacuum of 5000 Pa for 1 hour, and further dried at 60°C under normal pressure for 12 hours to obtain a powder. The obtained powder was calcined at 550°C for 4 hours to obtain a carbon dioxide reduction catalyst according to Example 1 (hereinafter also simply referred to as "catalyst").

[0055] Examples 2 and 3 Catalysts were prepared in the same manner as in Example 1, except that the amounts of iron, gallium, and barium nitrates were adjusted so that the content of barium as a catalytic metal was 2% by mass (Example 2) and 3% by mass (Example 3), respectively.

[0056] Comparative Example 1 A catalyst was prepared in the same manner as in Example 1, except that barium nitrate was not used as the catalytic metal, and iron nitrate, gallium nitrate, and zirconium nitrate were weighed out so that the mass ratio of Fe:Ga:Zr was 6.7:2.3:1.0 in terms of metal atoms.

[0057] The contents of catalytic metals and sodium (surface catalyst) in the catalysts of Examples 1 to 3 and Comparative Example 1 are shown in Table 1. In Table 1, the numbers in parentheses after the element names represent mass % in terms of metal atoms relative to the total mass of catalytic metals. In Table 1, "-" means that the element is not contained.

[0058]

[0059] [Evaluation] Using the carbon dioxide reduction catalysts of the above examples and comparative examples, a carbon dioxide reduction reaction was carried out in the following manner. A fixed-bed flow-type reactor was used, and the reaction gas was CO ２ 0.28NL / h, H ２ 0.84NL / h(CO ２ / H ２ W / F (catalyst weight / gas flow rate) was 5.0 g·h / mol, and space velocity SV (Space Velocity) was 5,000 h －１ The reaction conditions were a temperature of 380°C, a pressure of 3 MPa, and a reaction time of 4 hours. The gas components after the catalytic reaction were qualitatively and quantitatively analyzed by online gas chromatography (Shimadzu, GC-2014AT, detector: thermal conductivity detector (TCD)) and a flame ionization detector (FID) (Shimadzu, GC-2014AF). The liquid components after the catalytic reaction were also qualitatively and quantitatively analyzed by offline gas chromatography (Shimadzu, GC-2014AF, detector: flame ionization detector (FID)).

[0060] (CO ２Conversion rate) CO by the above carbon dioxide reduction reaction ２ The conversion rate of CO with Ba addition was calculated using the following formula (1). The results are shown in Figure 3. ２ The conversion rate was comparable to that of Comparative Example 1. ２ Conversion rate (%) = (CO before reaction ２ concentration)-(CO after reaction ２ concentration) / (CO before reaction ２ Concentration)×100…(1)

[0061] (C ８－１６ Selectivity) of hydrocarbons having 8 to 16 carbon atoms (C ８－１６ The selectivity of CO adsorbed on the catalyst was calculated using the following formula (2). The results are shown in Figure 4. The addition of Ba confirmed an improvement in the selectivity. ２ increases, and the intermediate CH ２ It is believed that the amount of C increased, the carbon chain grew, and the selectivity improved. ８－１６ Selectivity (%) = (C ８－１６ (concentration of contained components) / ((CO before reaction ２ concentration)-(CO after reaction ２ Concentration))×100…(2)

[0062] (C ８－１６ Production rate (yield) of hydrocarbons having 8 to 16 carbon atoms (C ８－１６ The production rate of C was calculated by the following formula (3). The results are shown in Figure 5. ８－１６ Selectivity improved, C ８－１６ The production rate was improved. ８－１６ Production rate (%) = CO ２ Conversion rate x C ８－１６ Selection rate / 100...(3)

[0063] In FIG. 5, the C with Ba content of 2 and 3 mass% ８－１６ The generation rate was approximated by least squares. The approximate formula obtained is shown in the following formula (4): (C ８－１６ Generation rate (%))=-12.0x+54.0...(4)

[0064] In the above formula (4), x represents the Ba content (mass%). From the above formula (4), the C of Comparative Example 1, which has a Ba content of 0 mass%, ８－１６ C exceeding production rate (%) ８－１６ The Ba content in the catalytic metal that gave the production rate (%) was calculated to be 0.1 to 2.2 mass %.

[0065] (Ba addition amount and CO ２ Next, the relationship between the amount of CO adsorption and the amount of CO adsorption of the catalysts of Example 1 and Comparative Examples 1, 2, and 3 was compared. ２ The relationship between the amount of adsorption and the amount of Ba added was investigated. The results are shown in Figure 6. The vertical axis of Figure 6 shows the amount of CO adsorption per catalyst weight. ２ The horizontal axis of Fig. 6 represents the amount of Ba added to the catalyst. ２ The amount of adsorption was measured using a gas adsorption measurement-catalysis analyzer. ２ After saturated adsorption, the material was heated to 850°C at a temperature increase rate of 10°C / min in a helium (He) atmosphere to remove CO. ２ The gas concentration was measured by a TCD detector, and the CO concentration per catalyst weight was ２ The amount of CO adsorption was calculated. ２ Considering the results of Figures 3 to 5 together, it is clear that the amount of C adsorption increased when Ba was added to the catalytic metal. ８ -C １６ The improvement of catalytic activity such as CO production rate ２ This is presumably due to an improvement in the amount of adsorption.

[0066] By using a carbon dioxide reduction (fuel synthesis) device filled with the carbon dioxide reduction catalyst of the present invention, it is possible to obtain a large amount of higher hydrocarbons having about 8 to 16 carbon atoms, which can be expected to be used to produce aviation fuel with a small input of energy.

[0067] REFERENCE SIGNS LIST 1, 1'... fuel synthesis device 20, 20'... catalytic reaction vessel 30... catalytic reaction vessel 40, 40'... water trap section L... flow path C1... carbon dioxide reduction catalyst C2... carbon dioxide reduction catalyst

Claims

1. A carbon dioxide reduction catalyst that reduces carbon dioxide by hydrogenating carbon dioxide with hydrogen, the carbon dioxide reduction catalyst containing iron, gallium, and barium as catalytic metals, with the iron being the main component of the catalytic metals.

2. The carbon dioxide reduction catalyst according to claim 1, which produces hydrocarbons by hydrogenating carbon dioxide and hydrogen.

3. The carbon dioxide reduction catalyst according to claim 1, wherein the content of said gallium is greater than the content of said barium.

4. The carbon dioxide reduction catalyst according to claim 1, wherein the content of said barium relative to said catalytic metal is 0.1 to 2.2 mass %.

5. The carbon dioxide reduction catalyst according to claim 1, further comprising sodium as a co-catalyst in addition to the catalytic metal.

6. The carbon dioxide reduction catalyst according to claim 1, further comprising zirconium as the catalytic metal.

7. The carbon dioxide reduction catalyst according to claim 1, further comprising sodium as a co-catalyst in addition to the catalytic metal, and further comprising zirconium as the catalytic metal.

8. A method for producing higher hydrocarbons, comprising producing hydrocarbons having 8 to 16 carbon atoms from a feed gas containing carbon dioxide and hydrogen using the carbon dioxide reduction catalyst according to any one of claims 1 to 7.

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