Carbon dioxide reduction catalyst device, carbon dioxide reduction method, and catalyst manufacturing method

Abstract

To provide a carbon dioxide reduction catalyst device capable of preferably generating hydrocarbons with 8 to 16 carbons by a hydrogenation reaction of carbon dioxide.SOLUTION: A carbon dioxide reduction catalyst device that reduces carbon dioxide by subjecting it to a hydrogenation reaction to produce hydrocarbons, the carbon dioxide reduction catalyst device having a first catalyst containing, as catalytic metals, Fe and at least one of Ga or Zr, and a second catalyst containing, as catalytic metals, Fe and Co, the second catalyst being disposed downstream of the first catalyst.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a carbon dioxide reduction catalyst device, a carbon dioxide reduction method, and a method for producing a catalyst. [Background technology]

[0002] Efforts to mitigate or reduce the impact of climate change have been ongoing for some time, and to achieve this, automobile exhaust gas regulations have been further advanced. In particular, there is a demand to reduce the amount of carbon dioxide emitted by internal combustion engines.

[0003] In recent years, technologies for producing fuel by subjecting carbon dioxide to a hydrogenation reaction have become known. For example, a catalyst made 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).

[0004] It is desired to be able to produce hydrocarbons with a carbon number of, for example, 5 or more 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 the FT (Fischer-Tropsch) synthesis reaction to prepare highly branched products with a carbon number of 5 or more (see Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 45-16682 [Patent Document 2] Special Publication No. 2005-537340 Summary of the Invention [Problem to be solved by the invention]

[0006] Meanwhile, in efforts to reduce carbon dioxide emissions, attention has been focused on technology related to sustainable aviation fuel (SAF), which is aviation fuel produced from biomass-derived materials, waste, etc. It would be desirable to be able to produce SAF directly from carbon dioxide using technology related to the hydrogenation reaction of carbon dioxide. However, the technology disclosed in Patent Document 2 has the problem that the production rate of hydrocarbons with carbon numbers of approximately 8 to 16, which are the main components of SAF, is low.

[0007] The present invention has been made in view of the above, and has an object to provide a carbon dioxide reduction catalyst device that can preferably produce hydrocarbons having 8 to 16 carbon atoms through a carbon dioxide hydrogenation reaction. [Means for solving the problem]

[0008] (1) The present invention relates to a carbon dioxide reduction catalyst device that reduces carbon dioxide by hydrogenating it to produce hydrocarbons, the carbon dioxide reduction catalyst device having a first catalyst containing Fe and at least one of Ga and Zr as catalytic metals, and a second catalyst containing Fe and Co as catalytic metals, the second catalyst being disposed downstream of the first catalyst.

[0009] (2) The carbon dioxide reduction catalyst device according to (1), wherein at least one of the first catalyst and the second catalyst further contains Na as a catalytic metal.

[0010] (3) The carbon dioxide reduction catalyst device according to (2), wherein at least one of the first catalyst and the second catalyst contains 0.5 to 1.5 mass % of Na in the catalytic metal.

[0011] (4) The carbon dioxide reduction catalyst device according to any one of (1) to (3), wherein the second catalyst contains 10 to 40 mass % of Co in the catalytic metal.

[0012] (5) The carbon dioxide reduction catalyst device according to any one of (1) to (4), further comprising a water trap portion between the first catalyst and the second catalyst.

[0013] (6) The carbon dioxide reduction catalyst device according to any one of (1) to (5), wherein the first catalyst contains at least one of an Fe—Ga composite oxide containing Fe and Ga, and an Fe—Zr composite oxide containing Fe and Zr.

[0014] (7) The present invention also relates to a carbon dioxide reduction method using the carbon dioxide reduction catalyst device according to any one of (1) to (6), in which a catalyst temperature T2 of the second catalyst is lower than a catalyst temperature T1 of the first catalyst.

[0015] (8) The carbon dioxide reduction method according to (7), wherein the catalyst temperature T2 is within a range of 260°C to 340°C.

[0016] (9) The present invention also relates to a method for producing the first catalyst according to (1), comprising a coprecipitation step of extracting a precipitate by a coprecipitation method from an aqueous solution in which a predetermined amount of the nitrate of Fe and at least one of the nitrate of Ga and the nitrate of Zr is dissolved in distilled water.

[0017] (10) The method for producing a catalyst according to (9), further comprising, after the coprecipitation step, an impregnation step of dropping an aqueous solution containing Na onto the precipitate, drying the precipitate for a predetermined period of time, and calcining the resulting powder at a predetermined temperature.

[0018] (11) The method for producing a catalyst according to (9) or (10), wherein in the coprecipitation step, a precipitation solution is obtained by adding dropwise a urea aqueous solution to an aqueous solution obtained by dissolving a predetermined amount of the nitrate of Fe and at least one of the nitrate of Ga and the nitrate of Zr in distilled water. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a carbon dioxide reduction catalyst device that can preferably produce hydrocarbons having 8 to 16 carbon atoms through a carbon dioxide hydrogenation reaction. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram showing the configuration of a carbon dioxide reduction catalyst device according to a first embodiment (Example 1). [Figure 2A] FIG. 10 is a diagram showing the configuration of a carbon dioxide reduction catalyst device according to a second embodiment (Example 2). [Figure 2B] FIG. 1 is a diagram showing the configuration of a carbon dioxide reduction catalyst device according to a comparative example. [Figure 2C] FIG. 1 is a diagram showing the configuration of a carbon dioxide reduction catalyst device according to a comparative example. [Figure 3] 1 is a graph comparing the C8-C16 yields of the carbon dioxide reduction catalyst devices of Examples and Comparative Examples. [Figure 4A] 1 is a graph showing the relationship between carbon number and selectivity in the carbon dioxide reduction catalyst device of Comparative Example 1. [Figure 4B] 10 is a graph showing the relationship between the carbon number and the selectivity in the carbon dioxide reduction catalyst device of Comparative Example 2. [Figure 4C] 1 is a graph showing the relationship between carbon number and selectivity in the carbon dioxide reduction catalyst device of Example 1. [Figure 5] 1 is a chart showing the relationship between C8-C16 selectivity and CO2 conversion rate and C8-C16 yield in Examples and Comparative Examples. [Figure 6A] 1 is a graph showing the relationship between the amount of Na added and the CO2 conversion rate in Examples and Comparative Examples. [Figure 6B] 1 is a graph showing the relationship between the amount of Na added and the C8-C16 selectivity in Examples and Comparative Examples. [Figure 6C] 1 is a graph showing the relationship between the amount of Na added and the C8-C16 production rate in Examples and Comparative Examples. [Figure 7A] 1 is a graph showing the relationship between the amount of Co added and the CO2 conversion rate in Examples and Comparative Examples. [Figure 7B]1 is a graph showing the relationship between the amount of Co added and the C8-C16 selectivity in Examples and Comparative Examples. [Figure 7C] 1 is a graph showing the relationship between the amount of Co added and the C8-C16 production rate in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0021] <Carbon dioxide reduction catalyst device> First Embodiment 1, the carbon dioxide reduction catalyst device 1 according to this embodiment has a catalytic reactor 20 having a first catalyst C1, and a catalytic reactor 30 having a second catalyst C2. The catalytic reactor 20 and the catalytic reactor 30 are connected by a flow path L, with the catalytic reactor 20 provided on the upstream side and the catalytic reactor 30 provided on the downstream side.

[0022] (First catalyst) The first catalyst C1, which is a carbon dioxide reduction catalyst according to this embodiment, contains Fe (iron) as an essential catalytic metal, and also contains at least one of Ga (gallium) and Zr (zirconium). It preferably further contains Na (sodium). The carbon dioxide reduction reaction using the first catalyst C1 according to this embodiment is a reaction that uses a mixed gas of H2 (hydrogen) and CO2 (carbon dioxide) as a raw material and produces hydrocarbons by carrying out, in a single stage, a reverse water gas shift reaction in which CO2 is reduced to CO (carbon monoxide), and an FT synthesis reaction in which CO is converted to hydrocarbons. The catalyst according to this embodiment contributes to both the reverse water gas shift reaction and the FT synthesis reaction. The carbon dioxide reduction reaction using the catalyst according to this embodiment has a space velocity (SV) of, for example, 5,000 h compared to conventional FT synthesis reactions. -1 Even under high flow rates, hydrocarbons with carbon numbers of 8 to 16 can be produced with high efficiency.

[0023] The Fe contained in the catalytic metal of the first catalyst C1 may be a compound such as an oxide, carbonate, nitrate, or sulfate, and is preferably an oxide. Two or more of these compounds may be contained. Furthermore, it is more preferable that Fe be contained in the catalytic metal as at least one of an Fe-Ga composite oxide containing Fe and Ga and an Fe-Zr composite oxide containing Fe and Zr. By using a catalytic metal containing at least one of an Fe-Ga composite oxide and an Fe-Zr composite oxide, the Fe particles can be more effectively converted into carbides in the FT synthesis reaction, which promotes the CH growth reaction in the catalyst and the growth of carbon chains.

[0024] The content of Fe in the catalytic metal of the first catalyst C1 is preferably 55 to 90 mass % in terms of metal atoms, and more preferably 60 to 75 mass %.

[0025] Like Fe, Ga contained in the catalytic metal of the first catalyst C1 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. Ga is more preferably contained in the catalytic metal as an Fe-Ga composite oxide containing Fe and Ga.

[0026] The Ga content in the catalytic metal of the first catalyst C1 is preferably 10 to 30 mass % in terms of metal atoms, and more preferably 20 to 30 mass %. If the Ga content is less than 10 mass %, the catalytic metal may not be sufficiently finely divided. By keeping the Ga content at 30 mass % or less, it is possible to avoid the adverse effects caused by Ga covering the reactive sites of Fe, and to prevent a decrease in catalytic activity.

[0027] Like Fe, Zr contained in the catalytic metal of the first catalyst C1 may be in the form of an oxide, a carbonate compound, a nitrate compound, a sulfate compound, or the like, and is preferably an oxide. Two or more of these compounds may be contained. Zr is more preferably contained in the catalytic metal as an Fe-Zr composite oxide containing Fe and Zr.

[0028] The content of Zr in the catalyst metal is preferably more than 0 mass% and not more than 15 mass%, and more preferably 5 to 10 mass%, calculated as metal atoms. By keeping the Zr content at 15 mass% or less, it is possible to avoid the adverse effects caused by Zr covering the reactive sites of Fe, and to prevent a decrease in catalytic activity.

[0029] The catalytic metal of the first catalyst C1 may contain both Ga and Zr. When the catalytic metal contains both Ga and Zr, it is more preferable that these catalytic metals are contained in the catalytic metal as an Fe-Ga-Zr composite oxide containing Fe, Zr, and Ga. Compared to compounds such as iron oxide, the Fe-Ga-Zr composite oxide is finely divided, which increases the reaction sites of the Fe catalyst and ensures the reaction time of the FT synthesis reaction, i.e., the time for the carbon chains of the produced hydrocarbons to grow.

[0030] The first catalyst C1 preferably further contains Na as a catalytic metal. Na functions as a promoter in the catalytic metal and captures CO2 as Na2CO3, thereby promoting the reverse water gas shift reaction in which CO is produced from H2 and CO2, thereby improving the CO2 conversion rate. Na is preferably present on the surface of the Fe-Zr composite oxide or the Fe-Ga-Zr composite oxide in the form of an oxide or the like, separate from the Fe-Zr composite oxide or the Fe-Ga-Zr composite oxide. Note that the catalytic metal may contain an alkali metal such as Li, K, Rb, or Cs instead of or in addition to Na.

[0031] The content of Na in the catalytic metal of the first catalyst C1 is preferably 0.5 to 1.5 mass%, and more preferably 1.0 mass%. By setting the Na content to 0.5 mass% or more, it is possible to sufficiently improve the production efficiency of hydrocarbons having a carbon number of 8 to 16. Furthermore, by setting the Na content to 1.5 mass% or less, it is possible to avoid the adverse effects caused by Na covering the reactive sites of Fe, and to prevent a decrease in catalytic activity.

[0032] (Second catalyst) The second catalyst C2 essentially contains Fe (iron) and Co (cobalt) as catalytic metals. Preferably, it further contains Na (sodium). The second catalyst C2 is disposed downstream of the first catalyst C1, and increases the carbon number of the hydrocarbons produced by the first catalyst C1, thereby improving the production rate (yield) of hydrocarbons with 8 to 16 carbon atoms.

[0033] The Fe contained in the catalytic metal of the second catalyst C2 may be a compound such as an oxide, carbonate, nitrate, or sulfate, and is preferably an oxide. Two or more of these compounds may be contained. Furthermore, it is more preferable that Fe is contained in the catalytic metal as an Fe-Co composite oxide containing Fe and Co. By using a catalytic metal containing an Fe-Co composite oxide, Co itself has carbon growth reactivity, which can promote carbon chain growth compared to compounds such as iron oxide.

[0034] The content of Fe in the catalytic metal of the second catalyst C2 is preferably 60 to 90 mass % in terms of metal atoms, and more preferably 70 to 80 mass %.

[0035] Like Fe, the Co contained in the catalytic metal of the second catalyst C2 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. Co is more preferably contained in the catalytic metal as an Fe-Co composite oxide containing Fe and Co.

[0036] The Co content in the catalytic metal of the second catalyst C2 is preferably 10 to 40 mass % in terms of metal atoms, and more preferably 20 to 30 mass %. By setting the Co content to 10 mass % or more, the carbon growth reactivity of Co itself can be exhibited. By setting the Co content to 40 mass % or less, the generation of methane as a by-product can be suppressed. Furthermore, the function of the iron catalyst to reduce carbon dioxide to carbon monoxide (reverse water gas shift reaction) can be maintained.

[0037] The second catalyst C2 preferably further contains Na as a catalytic metal. Na functions as a promoter in the catalytic metal. Na is preferably present on the surface of the Fe—Co composite oxide in the form of an oxide or the like, separate from the Fe—Co composite oxide. The catalytic metal may contain an alkali metal such as Li, K, Rb, or Cs instead of or in addition to Na.

[0038] The content of Na in the catalytic metal of the second catalyst C2 is preferably 0.5 to 1.5 mass%, and more preferably 1.0 mass%. By setting the Na content to 0.5 mass% or more, the basicity of the iron catalyst can be increased, and the production efficiency of hydrocarbons having 8 to 16 carbon atoms can be sufficiently improved. Furthermore, by setting the Na content to 1.5 mass% or less, the adverse effects caused by Na covering the reactive sites of Fe can be avoided, the production of carbon monoxide as a by-product can be suppressed, and a decrease in catalytic activity can be prevented.

[0039] (catalytic reactor) The configuration of the catalytic reactor 20 and the catalytic reactor 30 is not particularly limited, and known configurations can be applied. For example, a fixed-bed flow-type reactor in which a powder, granular, or pellet-shaped catalyst or a carrier carrying the catalyst is packed into a flow path having a predetermined shape can be used. The catalytic reactor 20 and the catalytic reactor 30 are independent of each other, and the catalyst temperatures can be set to different temperatures using a heating device (not shown).

[0040] Second Embodiment Next, the configuration of a carbon dioxide reduction catalyst device 1a according to a second embodiment of the present invention will be described with reference to Fig. 2A. The configuration of the carbon dioxide reduction catalyst device 1a is the same as that of the first embodiment, except that it has a water trap unit 40 in the middle of the flow path L.

[0041] (Water trap section) The water trap unit 40 removes water from the fluid supplied to the second catalyst C2. This allows the chemical equilibrium to be shifted in the catalytic reaction by the second catalyst C2 in the direction of increasing the carbon number of hydrocarbons. Therefore, the yield of hydrocarbons with a carbon number of 8 to 16 can be improved.

[0042] A conventionally known water trap unit 40 can be used. For example, it can be configured to be made up of a bent pipe, with condensed water pooling at the bent portion and condensed water exceeding a certain amount being discharged outside the system. In addition to the above, the water trap unit 40 may also have a configuration in which the pipe itself is cooled by ice or the like to trap condensed water. These may be used alone or in combination.

[0043] <Carbon dioxide reduction method> The carbon dioxide reduction method according to this embodiment is carried out using the carbon dioxide reduction catalyst device 1 or 1a. The carbon dioxide reduction method includes a first catalytic reaction step in which a gas containing carbon dioxide is brought into contact with a first catalyst C1 arranged upstream, and a second catalytic reaction step in which a gas containing hydrocarbons produced in the first catalytic reaction step is brought into contact with a second catalyst C2 arranged downstream to increase the carbon number. Between the first catalytic reaction step and the second catalytic reaction step, a step of removing moisture from the gas containing hydrocarbons produced in the first catalytic reaction step using a water trap unit 40 may be included.

[0044] The catalyst temperature T2 of the second catalyst C2 in the second catalytic reaction step is preferably lower than the catalyst temperature T1 of the first catalyst C1 in the first catalytic reaction step, which makes it possible to control the activity of Co contained in the second catalyst and further improve the yield of hydrocarbons having 8 to 16 carbon atoms.

[0045] The catalyst temperature T1 is preferably set to, for example, 340 to 400°C, and the catalyst temperature T2 is preferably set to, for example, 260 to 340°C.

[0046] <First catalyst production method> The first catalyst production method according to this embodiment preferably includes a coprecipitation step and an impregnation step.

[0047] (Co-precipitation process) The coprecipitation step is a step of extracting a catalyst precursor precipitate by coprecipitation from an aqueous solution prepared by dissolving a predetermined amount of Fe nitrate and at least one of Ga nitrate and Zr nitrate in distilled water. The coprecipitation step forms at least one of an Fe-Ga composite oxide, an Fe-Zr composite oxide, and an Fe-Ga-Zr composite oxide. In the coprecipitation step, a precipitation solution is preferably obtained by adding a urea aqueous solution dropwise to the aqueous solution containing Fe and at least one of Ga and Zr. The precipitate is then separated from the precipitation solution by filtration, washing, or the like, and dried to obtain a catalyst precursor precipitate (an Fe-Ga composite oxide, an Fe-Zr composite oxide, or an Fe-Ga-Zr composite oxide).

[0048] (Impregnation process) The impregnation step involves dropping an aqueous solution containing Na onto the precipitate obtained in the coprecipitation step, drying the resulting powder for a predetermined period of time, and firing the resulting powder at a predetermined temperature. The impregnation step allows the Na compound to be unevenly distributed near the surface of the composite oxide. An example of an aqueous solution containing Na is a NaNO3 solution. The NaNO3 solution can be dropped 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, 550°C, and the firing time can be 4 hours.

[0049] <Second catalyst manufacturing method> The second catalyst production method according to this embodiment preferably includes a hydrothermal synthesis step and an impregnation step.

[0050] (Hydrothermal synthesis process) The hydrothermal synthesis step is a step of extracting a catalyst precursor precipitate by hydrothermal synthesis from an aqueous solution in which predetermined amounts of Fe nitrate and Co nitrate are dissolved in a urea aqueous solution. An Fe-Co composite oxide is formed by the hydrothermal synthesis step. In the hydrothermal synthesis step, it is preferable to obtain a precipitate solution by subjecting the above aqueous solution containing Fe and Co to the hydrothermal synthesis step using an autoclave. Thereafter, the precipitate is separated from the precipitate solution by filtration, washing, etc., and dried to obtain a catalyst precursor precipitate (Fe-Co composite oxide).

[0051] (Impregnation process) The impregnation step can be the same as the impregnation step in the first catalyst production method.

[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. [Example]

[0053] Next, an example of the present invention will be described, but the present invention is not limited to this example.

[0054] Example 1 [Preparation of the first catalyst] The first catalyst consisted of Fe nitrate (Fe(NO3)3·9H2O), Zr nitrate (ZrO(NO3)2·2H2O), and Ga nitrate (Ga(NO3)3·6H2O) as catalytic metals. The mass ratio of Fe:Zr:Ga was 6:1:3, and the components were weighed and dissolved in distilled water. Next, while stirring, CH4N2O solution was added dropwise at 2 mL / min to the solution, maintaining the pH at 8.5. This resulted in a precipitate solution containing Fe, Zr, and Ga. The solution was then aged at room temperature for 24 hours, after which the precipitate was separated by repeated filtration and washing. The separated precipitate was dried at 60 °C for 12 hours to obtain an Fe-Ga-Zr catalyst precursor.

[0055] An aqueous NaNO solution was added dropwise to the Fe-Ga-Zr catalyst precursor under ultrasonic vibration at 92 kHz so that the Na content was 1.0 mass%. The catalyst was then dried under a vacuum of 5000 Pa for 1 hour and then 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 first catalyst according to Example 1.

[0056] [Preparation of the second catalyst] The second catalyst contained Fe nitrate (Fe(NO3)3·9H2O) as the catalytic metal, and Co nitrate (Co(NO3)2·6H2O) as the catalytic metal. These were weighed out so that the mass ratio of Fe:Co was 3:1 in terms of metal atoms, and dissolved in urea water. The aqueous solution was then stirred for 1 hour, transferred to an autoclave, and subjected to hydrothermal synthesis at 120°C for 12 hours, yielding a precipitate solution containing Fe and Co as precipitates. The precipitate solution was then aged at room temperature for 24 hours, after which the precipitate was separated by repeated filtration and washing. The separated precipitate was dried at 60°C for 12 hours to obtain an Fe-Co catalyst precursor.

[0057] An aqueous NaNO solution was added dropwise to the Fe-Co catalyst precursor under ultrasonic vibration at 92 kHz so that the Na content was 1.0 mass%. The catalyst was then dried under a vacuum of 5000 Pa for 1 hour and then further dried at normal pressure at 60°C for 12 hours to obtain a powder. The obtained powder was calcined at 550°C for 4 hours to obtain the second catalyst according to Example 1.

[0058] [Preparation of carbon dioxide reduction catalyst device] The carbon dioxide reduction catalyst device 1 shown in Figure 1 was fabricated using the first catalyst and second catalyst obtained as described above. A fixed-bed flow-type reactor was used as the catalytic reactor, and 0.25 g of the first catalyst in the form of pellets measuring 0.4 to 0.8 mm square was used. The pellets were packed in a reaction tube (inner diameter 6 mm) to a length of 5 cm. The second catalyst had the same shape, weight, and packing amount as the first catalyst. The reaction temperatures were 380°C for the catalyst temperature T1 of the first catalyst and 300°C for the catalyst temperature T2 of the second catalyst.

[0059] <Example 2> The procedure was the same as in Example 1, except that a carbon dioxide reduction catalyst device 1a shown in FIG. 2A was fabricated.

[0060] Example 3 The procedure was the same as in Example 2, except that the catalyst temperature T2 of the second catalyst was set to 220°C.

[0061] Example 4 The same procedure as in Example 2 was followed, except that the catalyst temperature T2 of the second catalyst was set to 260°C.

[0062] <Example 5> The same procedure as in Example 2 was followed except that the catalyst temperature T2 of the second catalyst was set to 340°C.

[0063] Example 6 The second catalyst was prepared in the same manner as in Example 2, except that the Na content (addition amount) of the second catalyst was 0.5 mass %.

[0064] Example 7 The second catalyst was prepared in the same manner as in Example 2, except that the Na content (addition amount) of the second catalyst was 1.5 mass %.

[0065] Example 8 The second catalyst was prepared in the same manner as in Example 2, except that the Co content (addition amount) of the second catalyst was 10 mass% (the second catalyst was prepared so that the Fe content was 89 mass% and the Na content was 1.0 mass%).

[0066] Example 9 The second catalyst was prepared in the same manner as in Example 2, except that the Co content (addition amount) of the second catalyst was 25 mass% (the second catalyst was prepared so that the Fe content was 74 mass% and the Na content was 1.0 mass%).

[0067] Example 10 The second catalyst was prepared in the same manner as in Example 2, except that the Co content (addition amount) of the second catalyst was 40 mass% (the second catalyst was prepared so that the Fe content was 59 mass% and the Na content was 1.0 mass%).

[0068] <Comparative Example 1> The carbon dioxide reduction catalyst device 1b shown in Fig. 2B was produced in the same manner as in Example 1, except that it was produced using only the first catalyst obtained as described above. As shown in Fig. 2B, the carbon dioxide reduction catalyst device 1b only has a catalytic reactor 20 having a first catalyst C1 as a catalytic reactor. The catalyst temperature T1 of the first catalyst was set to 380°C.

[0069] <Comparative Example 2> The carbon dioxide reduction catalyst device 1c shown in Fig. 2C was produced using the first catalyst and second catalyst obtained as described above, in the same manner as in Example 1. In the carbon dioxide reduction catalyst device 1c, as shown in Fig. 2C, the first catalyst C1 and the second catalyst C2 are packed in the same catalytic reactor 21 and adjusted to the same catalyst temperature. The catalyst temperature T1 of the first catalyst and the catalyst temperature T2 of the second catalyst were set to 380°C.

[0070] <Comparative Example 3> The second catalyst was prepared in the same manner as in Example 2, except that no Na was added to the second catalyst.

[0071] <Comparative Example 4> The second catalyst was prepared in the same manner as in Example 2, except that no Co was added to the second catalyst.

[0072] [evaluation] Using the carbon dioxide reduction catalyst devices of the above examples and comparative examples, a carbon dioxide reduction reaction was carried out in the following manner. The reaction gases were CO2 0.28 NL / h and H2 0.84 NL / h (CO2 / H2 = 1 / 3). The W / F (catalyst weight / gas flow rate) was 5.0 g h / mol, and the space velocity (SV) was 5,000 h. -1The pressure was 3 MPa, and the reaction time was 4 hours. The gas components after the catalytic reaction were analyzed qualitatively and quantitatively using 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 analyzed qualitatively and quantitatively using offline gas chromatography (Shimadzu, GC-2014AF, detector: flame ionization detector (FID)).

[0073] (CO2 conversion rate) The conversion rate of CO2 by the carbon dioxide reduction reaction was calculated using the following formula (1). The results are shown in Figures 5, 6A, and 7A. CO2 conversion rate (%) = ((CO2 concentration before reaction) - (CO2 concentration after reaction)) / (CO2 concentration before reaction) × 100 ... (1)

[0074] (C 8-16 Selection rate) The hydrocarbons (C 8-16 The selectivity of hydrocarbons having different carbon numbers and structures was calculated using the same method as in the following equation (2). The results are shown in Figures 5, 6B, and 7B. The selectivity of hydrocarbons having different carbon numbers and structures was also calculated using the same method as in the following equation (2). The results are shown in Figures 4A to 4C. C 8-16 Selectivity (%) = (C 8-16 Concentration of contained components) / ((CO2 concentration before reaction) - (CO2 concentration after reaction)) × 100 ... (2)

[0075] (C 8-16 Production rate (yield) The hydrocarbons (C 8-16 The production rate of ) was calculated by the following formula (3). The results are shown in Figures 3, 5, 6C, and 7C. C 8-16 Production rate (%) = CO2 conversion rate × C 8-16 Selection rate / 100 …(3)

[0076] As shown in FIG. 3, the carbon dioxide reduction catalyst devices according to the examples have a C 8-16 The results clearly show a high production rate (yield).

[0077] FIG. 4A is a graph showing the carbon number of hydrocarbons produced by a carbon dioxide reduction catalyst device according to Comparative Example 1 and the selectivity of hydrocarbons for each carbon number. Similarly, FIG. 4B is a graph corresponding to Comparative Example 2, and FIG. 4C is a graph corresponding to Example 1. In FIGS. 4A to 4C, "Paraffins" refers to saturated chain hydrocarbons with a linear structure. "Iso-paraffins" refers to saturated chain hydrocarbons with a branched structure. "Olefins" refers to chain hydrocarbons with a double bond.

[0078] As shown in FIG. 4A, the carbon dioxide reduction catalyst device of Comparative Example 1, which used only the first catalyst, 8-16 4B, the carbon dioxide reduction catalyst device of Comparative Example 2, which used the first catalyst and the second catalyst at the same catalyst temperature, 8-16 Although the production rate was slightly improved compared to Comparative Example 1, the production rate of hydrocarbons with a small carbon number, such as methane, was high. As shown in FIG. 4C, the carbon dioxide reduction catalyst device of Example 1, in which the catalyst temperature of the first catalyst was set higher than the catalyst temperature of the second catalyst, 8-16 The production rate was further improved compared to Comparative Example 2, and the production rate of hydrocarbons with a small carbon number, such as methane, was reduced.

[0079] FIG. 5 shows the C of each example and comparative example. 8-16 Selectivity and CO2 conversion, and the C that correlates with these results. 8-16 5 is a chart showing the relationship between the production rate (yield) and the catalyst temperature of the first catalyst, which is set to 380°C and the catalyst temperature of the second catalyst is set to 260°C to 340°C. 8-16 The production rate (yield) can be increased to 20% or more.

[0080] 6A, 6B, and 6C show the CO2 conversion rate and C, respectively, when only the amount of Na added to the second catalyst was changed under the same conditions. 8-16 Selectivity, C 8-16 6A, 6B, and 6C show that the production rate (yield) of C 8-16 Although the production activity improves, it is presumed that increasing the amount of Na by more than 1.0 mass% causes Na to cover the reaction sites of the Fe catalyst, resulting in a monotonous decrease in activity. Therefore, it is clear that a Na addition amount in the range of 0.5 to 1.5 mass% is preferable. In particular, Example 2, in which the Na addition amount is 1.0 mass%, is excellent in all results and is clearly the most preferable.

[0081] 7A, 7B, and 7C show the CO2 conversion rate and C, respectively, when only the amount of Co added to the second catalyst was changed under the same conditions. 8-16 Selectivity, C 8-16 This is a graph comparing the production rate (yield). 8-16 Although the production activity improves, if the Co content is increased beyond 25% by mass, the Co covers the reaction sites of the Fe catalyst, causing a monotonous decrease in activity and the production of methane as a by-product. Therefore, it is clear that a Co content in the range of 10 to 40% by mass is preferable. In particular, Example 9, in which the Co content is 25% by mass, is excellent in all results and is clearly the most preferable. [Explanation of symbols]

[0082] 1, 1a Carbon dioxide reduction catalyst device C1 First catalyst C2 Second catalyst 40 Water trap section

Claims

1. A carbon dioxide reduction catalyst device that reduces carbon dioxide by a hydrogenation reaction to produce hydrocarbons, a first catalyst containing Fe, Ga, and Zr as catalytic metals; a second catalyst containing Fe, Co, and Na as catalytic metals; The content of Ga in the first catalyst is 10 to 30 mass% in terms of metal atoms, The content of Zr in the first catalyst is more than 0 mass% and 15 mass% or less in terms of metal atoms, the content of Co in the second catalyst is 10 to 40 mass% in terms of metal atoms, a carbon dioxide reduction catalyst device, wherein the second catalyst is disposed downstream of the first catalyst;

2. 2. The carbon dioxide reduction catalyst device according to claim 1, wherein the first catalyst further contains Na as a catalytic metal.

3. 3. The carbon dioxide reduction catalyst device according to claim 1, wherein at least one of the first catalyst and the second catalyst contains 0.5 to 1.5 mass % of Na in the catalytic metal.

4. 3. The carbon dioxide reduction catalyst device according to claim 1, further comprising a water trap portion between the first catalyst and the second catalyst.

5. 3. The carbon dioxide reduction catalyst device according to claim 1, wherein the first catalyst contains an Fe--Ga--Zr composite oxide containing Fe, Ga, and Zr.

6. A carbon dioxide reduction method using the carbon dioxide reduction catalyst device according to claim 1, A carbon dioxide reduction method, wherein a catalyst temperature T2 of the second catalyst is lower than a catalyst temperature T1 of the first catalyst.

7. 7. The carbon dioxide reduction method according to claim 6, wherein the catalyst temperature T2 is 260 to 340°C.

8. A method for manufacturing a carbon dioxide reduction catalyst device according to claim 1, comprising: a method for manufacturing a carbon dioxide reduction catalyst device, the method including a co-precipitation step of extracting a precipitate by a co-precipitation method from an aqueous solution in which a predetermined amount of the nitrate of Fe and at least one of the nitrate of Ga and the nitrate of Zr is dissolved in distilled water.

9. 9. The method for manufacturing a carbon dioxide reduction catalyst device according to claim 8, further comprising, subsequent to the coprecipitation step, an impregnation step of dropping an aqueous solution containing Na onto the precipitate, drying the precipitate for a predetermined period of time, and firing the obtained powder at a predetermined temperature.

10. 10. The method for manufacturing a carbon dioxide reduction catalyst device according to claim 8, wherein in the coprecipitation step, a precipitation solution is obtained by adding dropwise a urea aqueous solution to an aqueous solution in which a predetermined amount of the Fe nitrate and at least one of the Ga nitrate and the Zr nitrate is dissolved in distilled water.

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