Hydrocarbon production system, and method of producing and operating the system

Abstract

To provide a hydrocarbon production system that can ensure hydrogen and carbon monoxide necessary for hydrocarbon synthesis from water and carbon dioxide as raw materials to efficiently produce a hydrocarbon gas including a high calorie gas.SOLUTION: A system 100 is provided with an electrolysis reaction part 10, a reverse water gas shift reaction part 20, and a hydrocarbon synthetic reaction part 30 that includes an impregnated support catalyst cat2 with a carrier cb2 having at least ruthenium supported thereon.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a hydrocarbon production system for producing hydrocarbons from at least water and carbon dioxide, and to a production method and an operation method of the hydrocarbon production system. [Background technology]

[0002] An example of a hydrocarbon production system is disclosed in US Pat. No. 5,399,633. The system disclosed in Patent Document 1 includes a high-temperature electrolyte (HTE) reactor (corresponding to the electrolytic reaction section of the present invention) equipped with a stack of single electrolytic cells (corresponding to the electrolytic cell units of the present invention) that produce either hydrogen or a synthesis feed gas ("synthesis gas" representing a mixture of hydrogen and carbon monoxide) from water vapor and carbon dioxide, and converts the synthesis gas obtained in the single electrolytic cells into a desired combustible gas by heterogeneous catalytic action. Therefore, in the technology disclosed in Patent Document 1, a hydrocarbon synthesis section is provided downstream of an electrolytic reaction section, and hydrocarbons are synthesized (produced) using water and carbon dioxide as starting materials.

[0003] In this prior art, the electrolysis reaction section performs so-called "co-electrolysis" in which water and carbon dioxide are electrolyzed together. A heterogeneous catalyst is used for the synthesis of hydrocarbons (so-called methanation). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2016-522166 Summary of the Invention [Problem to be solved by the invention]

[0005] However, although heterogeneous catalysts are used for the synthesis of hydrocarbons, it is difficult to select such catalysts, and a technology for stably synthesizing hydrocarbons has not yet been established.

[0006] In view of this situation, a main object of the present invention is to provide a hydrocarbon production system that can efficiently produce a high calorie gas containing, for example, at least a low hydrocarbon, by securing hydrogen and carbon monoxide necessary for hydrocarbon synthesis using water and carbon dioxide as raw materials. [Means for solving the problem]

[0007] The first characteristic configuration of the present invention is as follows: an electrolytic reaction section that converts water into hydrogen by an electrolytic reaction, or converts water and carbon dioxide into hydrogen and carbon monoxide by an electrolytic reaction, and a catalytic reaction section that converts a product generated in the electrolytic reaction section into at least hydrocarbons by a catalytic reaction; The catalytic reaction section is provided with a hydrocarbon synthesis catalyst in which at least ruthenium is supported on a metal oxide carrier.

[0008] The hydrocarbon production system having this configuration includes an electrolytic reaction section and a catalytic reaction section, and at least hydrogen or hydrogen and carbon monoxide required for the synthesis of hydrocarbons are obtained from water or water and carbon dioxide in the former electrolytic reaction section. Here, when only hydrogen is obtained in the electrolytic reaction section, at least one selected from carbon monoxide and carbon dioxide may be supplied upstream of the catalytic reaction section.

[0009] In the catalytic reaction section, hydrocarbons are obtained from the supplied hydrogen and at least one selected from carbon monoxide and carbon dioxide. In this catalytic reaction section, a hydrocarbon synthesis catalyst in which at least ruthenium is supported on a metal oxide support is used. As a result, as described below, hydrocarbons can be produced in a highly efficient and stable manner in the catalytic reaction section. The catalyst used in the catalytic reaction section is a catalyst in which ruthenium is supported as a catalytically active component on a metal oxide support, and is therefore easy to produce and has stable performance, which is preferable.

[0010] The second characteristic configuration of the present invention is as follows: The catalytic reaction section converts the product produced in the electrolytic reaction section into a high-calorie gas containing at least lower saturated hydrocarbons through a catalytic reaction.

[0011] As mentioned above, the catalytic reaction section functions as a hydrocarbon synthesis reaction section. When the hydrocarbons produced in this section become gases containing at least lower saturated hydrocarbons, the gases synthesized in the hydrocarbon synthesis reaction section (total gases containing multiple lower saturated hydrocarbons) have a calorific value of, for example, 39 MJ / Nm 3 It becomes a high calorie gas. As a result, by using the hydrocarbon production system according to the present invention, a very useful high-calorie gas can be produced in a relatively simple and stable system.

[0012] The third characteristic configuration of the present invention is as follows: The amount of ruthenium supported is from 0.1% by weight to 5% by weight. Here, weight % is synonymous with mass % (the same applies below).

[0013] By using ruthenium as a catalytic active component, it is possible to perform a highly active and stable hydrocarbon synthesis, but if the loading amount is less than 0.1% by weight, the synthesis effect may decrease. On the other hand, if it is more than 5% by weight, the cost increases. Therefore, the above range is preferable.

[0014] The fourth characteristic configuration of the present invention is as follows: The metal oxide support supports at least one of molybdenum, vanadium, iron and cobalt in addition to ruthenium.

[0015] In this configuration, by adding a specified element (at least one of molybdenum, vanadium, iron, and cobalt) to the metal oxide support in addition to ruthenium as the catalyst used for hydrocarbon synthesis, it is possible to synthesize hydrocarbons with higher catalytic activity than when ruthenium is used alone.

[0016] The fifth characteristic configuration of the present invention is as follows: The amount of at least one of molybdenum, vanadium, iron and cobalt supported is 0.2% by weight or more and 6% by weight or less.

[0017] By adding a specific element (at least one of molybdenum, vanadium, iron, and cobalt) in addition to ruthenium as a catalytically active component, hydrocarbon synthesis can be performed well, but if the amount of the additional element supported is less than 0.2% by weight, the synthesis effect may decrease. On the other hand, if it is more than 6% by weight, the cost increases. Therefore, the above range is preferable.

[0018] The sixth characteristic configuration of the present invention is as follows: The carbon monoxide adsorption amount of the hydrocarbon synthesis catalyst is 0.4 ml / g or more.

[0019] By ensuring that the carbon monoxide adsorption amount is 0.4 ml / g or more, a large surface area of ​​the catalyst contributing to hydrocarbon synthesis can be secured, and the catalytically active components can be well distributed on the surface of the metal oxide support, thereby maintaining high hydrocarbon synthesis ability.

[0020] The seventh characteristic configuration of the present invention is The feature is that it has a reverse water gas shift catalytic reaction section.

[0021] The hydrocarbon production system according to the present invention comprises at least an electrolytic reaction section and a catalytic reaction section, and produces at least hydrogen in the electrolytic reaction section and uses this hydrogen for hydrocarbon synthesis, while the catalytic reaction section requires hydrogen and at least one selected from carbon monoxide and carbon dioxide. Here, when synthesizing hydrocarbons such as methane in the catalytic reaction section, the synthesis reaction of hydrocarbons is more easily promoted by reacting hydrogen with carbon monoxide than by reacting hydrogen with carbon dioxide. As explained above, although it is possible to supply carbon monoxide and / or carbon dioxide separately, the synthesis of hydrocarbons can be more effectively carried out by providing a reverse water gas shift reaction section and generating carbon monoxide from carbon dioxide by the reverse water gas shift reaction and supplying it to the catalytic reaction section.

[0022] Furthermore, when co-electrolysis is performed in the electrolysis reaction section in which both water and carbon dioxide are electrolyzed, the electrolysis reaction of water requires a lower electrolysis voltage than the electrolysis reaction of carbon dioxide, and therefore the electrolysis reaction of water proceeds more easily than the electrolysis reaction of carbon dioxide, and there are cases in which carbon monoxide is not produced sufficiently compared to the production of hydrogen. However, a reverse water-gas shift reaction can be caused by the hydrogen produced in the electrolysis reaction section and the unreacted carbon dioxide in the electrolysis reaction section, thereby increasing the carbon monoxide concentration and supplying it to the catalytic reaction section.

[0023] An eighth characteristic feature of the present invention is that a water separation section is provided at least in one of the upstream and downstream of the catalytic reaction section.

[0024] By adopting this configuration, if a water separation section is provided upstream of the catalytic reaction section, water remaining in the gas without being decomposed in the electrolytic reaction section can be removed upstream of the catalytic reaction section, thereby making it possible to adjust the amount of water supplied to the catalytic reaction section. If a water separation section is provided downstream of the catalytic reaction section, water remaining in the gas discharged from the catalytic reaction section can be removed upstream of the catalytic reaction section and used.

[0025] Furthermore, as described in a ninth characteristic configuration of the present invention, It is preferable to provide a recycle line for recycling the water separated in the water separation section.

[0026] By employing this configuration, the water separated in the water separation section can be used as new water for hydrocarbon synthesis.

[0027] The tenth characteristic configuration of the present invention is as follows: The feature is that a carbon dioxide separation section is provided downstream of the catalytic reaction section.

[0028] By adopting this configuration, it is possible to separate the carbon dioxide contained in the gas obtained from the catalytic reaction section and increase the concentration of hydrocarbons, thereby making it possible to increase the calorific value per unit volume, which is an important requirement for a high-calorie gas, which is one of the objects of the present invention.

[0029] Furthermore, as described in an eleventh characteristic configuration of the present invention, It is preferable to provide a recycle line for recycling the carbon dioxide separated in the carbon dioxide separation section.

[0030] By employing this configuration, the carbon dioxide separated in the carbon dioxide separation section can be used as new carbon dioxide for hydrocarbon synthesis.

[0031] The twelfth characteristic configuration of the present invention is The present invention is characterized in that a heavy hydrocarbon separation section is provided downstream of the catalytic reaction section.

[0032] According to this characteristic configuration, By providing a heavy hydrocarbon separation section, heavy hydrocarbons, which are useful hydrocarbon components, can be separated and utilized.

[0033] The thirteenth characteristic configuration of the present invention is The electrolytic reaction section has an electrolytic cell in which at least an electrode layer, an electrolyte layer and a counter electrode layer are formed on a support.

[0034] According to this characteristic configuration, the electrolytic cell used in the electrolytic reaction section is provided with, for example, a thin-film electrode layer, an electrolyte layer, and a counter electrode layer on a sturdy support that is thin but has sufficient strength, thereby making it possible to effectively cause an electrolytic reaction while reducing the amount of material used to constitute these layers that make up the electrolytic cell. As a result, it is possible to configure an electrolytic cell unit that is compact, has high performance, and is strong and reliable. Metals and ceramics can be selected as materials for this type of support.

[0035] The fourteenth characteristic configuration of the present invention is The support is made of a metal.

[0036] By using metal as the support, material costs can be reduced by ensuring strength using inexpensive metal materials, and it is easier to process than ceramics.

[0037] The fifteenth characteristic configuration of the present invention is The feature is that the impregnated supported catalyst obtained through the impregnation supporting step of impregnating and supporting ruthenium on a metal oxide support is disposed in the catalytic reaction section of the hydrocarbon production system described above.

[0038] By the technique of impregnating and supporting ruthenium on a metal oxide support, it is possible to obtain a good catalyst to be placed in the catalytic reaction section of the hydrocarbon production system described above, and to obtain a high-performance hydrocarbon production system.

[0039] As the catalyst to be housed in this type of catalytic reaction section, it is more preferable to use an impregnated supported catalyst obtained through an impregnation / support process in which a metal oxide support is impregnated with at least one of molybdenum, vanadium, and iron in addition to ruthenium, as described in the 16th characteristic configuration of the present invention.

[0040] The seventeenth characteristic configuration of the present invention is The present invention relates to a method for operating the hydrocarbon production system described above, and is characterized in that the catalytic reaction section is operated after being subjected to a reduction pretreatment.

[0041] By carrying out the reduction pretreatment in this manner, the catalytic ability of the hydrocarbon synthesis catalyst provided in the catalytic reaction section can be fully exhibited.

[0042] The eighteenth characteristic configuration of the present invention is The present invention relates to a method for operating a hydrocarbon production system including a reverse water gas shift reactor, the method being characterized in that the reverse water gas shift catalytic reactor is operated after being subjected to a reduction pretreatment.

[0043] By carrying out such a reduction pretreatment, the catalytic ability of the reverse water gas shift catalyst provided in the reverse water gas shift reactor can be fully exhibited. [Brief description of the drawings]

[0044] [Figure 1] Diagram showing the configuration of a hydrocarbon production system [Diagram 2]Schematic diagram showing the configuration of the electrolytic reaction section [Diagram 3] FIG. 1 shows the configuration of a system that integrates an electrolysis reactor and a reverse water gas shift reactor. [Figure 4] Schematic diagram of an electrolysis cell unit equipped with an electrolysis reactor and a reverse water gas shift reactor. [Diagram 5] Cross-sectional view of the electrolysis cell unit used in a comparison experiment in which the electrode layer side gas supply channel was used as a reverse water-gas shift reactor. [Figure 6] A diagram showing the configuration of a system equipped with a heat exchanger between the electrolysis reactor and the reverse water gas shift reactor. [Figure 7] A diagram showing another configuration of a hydrocarbon production system in which CO2 is introduced into a reverse water gas shift reactor. [Figure 8] FIG. 1 is a diagram showing another configuration of a hydrocarbon production system equipped with a hydrogen separation unit. [Figure 9] FIG. 1 shows yet another configuration of a hydrocarbon production system including a water separation section prior to a hydrocarbon synthesis reaction section. [Figure 10] FIG. 13 is a diagram showing yet another configuration of a hydrocarbon production system in which only water is introduced into the electrolysis reaction section. [Figure 11] An explanatory diagram showing the preparation state of the catalyst [Figure 12] An explanatory diagram showing the catalyst coating and calcination state and pre-reduction treatment [Figure 13] Schematic diagram of an electrolysis cell unit equipped with an electrolysis reaction section, a reverse water-gas shift reaction section, and a hydrocarbon synthesis reaction section. [Figure 14] FIG. 1 shows another configuration of a hydrocarbon production system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of one embodiment of a hydrocarbon production system 100 proposed by the present inventors.

[0046] As shown in the figure, the hydrocarbon production system 100 is configured to include, in order, an electrolytic reaction section 10, a first catalytic reaction section 20, a second catalytic reaction section 30, a heavy hydrocarbon separation section 35 (illustrated as a CnHm separation section), a water separation section 40 (illustrated as an H2O separation section), and a carbon dioxide separation section 50 (illustrated as a CO2 separation section).

[0047] The electrolytic reaction section 10 is a section for electrolyzing at least a part of the inflowing gas, the first catalytic reaction section 20 is a reverse water-gas shift reaction section for performing a reverse water-gas shift reaction on at least a part of the inflowing gas, and the second catalytic reaction section 30 is configured to function as a hydrocarbon synthesis reaction section for synthesizing at least a part of the inflowing gas into hydrocarbons. Here, the hydrocarbons synthesized are mainly CH4 (hydrocarbons with one carbon atom), but also include lower saturated hydrocarbons with 2 to 4 carbon atoms. Furthermore, as will be described later, by appropriately selecting a catalyst used in the second catalytic reaction section 30, it is possible to synthesize heavy hydrocarbons with a carbon number larger than the lower saturated hydrocarbons, hydrocarbons that are not saturated, or oxygen-containing hydrocarbons. Therefore, in this specification, hydrocarbons are a concept that includes all of these, and are also collectively referred to as hydrocarbons.

[0048] The heavy hydrocarbon separation section 35, the water separation section 40 and the carbon dioxide separation section 50 are sections that remove at least a portion of predetermined components (in the order of appearance, CnHm, H2O and CO2) from the gas flowing therethrough. The components removed and recovered by the water separation section 40 and the carbon dioxide separation section 50 are returned to predetermined sections of the system via a water return line 41 and a carbon dioxide return line 51 as shown in FIG. 1, and are reused. The H2O and CO2 returned via these return lines (recycle lines) 41, 51 are shown above the two return lines. These two return lines 41 and 51 are branch lines in each section 40, 50. As a result, the hydrocarbon production system 100 can function as a carbon-closed system that does not substantially release CO2 outside the system.

[0049] In the figure, the gases flowing into each part are shown before each part, and the gases discharged from each part are shown after each part.

[0050] In the electrolysis reaction section 10, H2O and CO2 as starting materials are flowed in and electrolyzed therein, whereby H2O is decomposed into H2 and O2, and a part of CO2 is decomposed into CO and O2 and released.

[0051] The reaction is described as follows: 2H2O→2H2+O2 (formula 1) 2CO2→2CO+O2 (formula 2) These formulas 1 and 2 are also shown in the box representing the electrolytic reaction section 10 in FIG.

[0052] In the first catalytic reaction section 20 (reverse water-gas shift reaction section), H2 and CO2 are introduced and a reverse water-gas shift reaction occurs therein, whereby CO2 becomes CO and H2 becomes H2O, which are then released.

[0053] The reaction is written as the following equilibrium reaction, but the reverse water gas shift reaction is a reaction in which the reaction described in equation 3 below proceeds to the right (in the direction in which CO2 and H2 react to produce CO and HO). CO2+H2⇔CO+H2O (Formula 3) This formula 3 is also shown in the box representing the first catalytic reaction section 20 (reverse water gas shift reaction section) in Fig. 1. The reverse water gas shift catalyst cat1 used in the reaction is also shown diagrammatically in this box.

[0054] In the second catalytic reaction section 30 (hydrocarbon synthesis reaction section), H2 and CO are flowed in, and hydrocarbons are synthesized by catalytic reaction. For example, the reaction in which CH4 is synthesized from CO and H2 is described as the following equilibrium reaction, but the reaction in which CH4 is synthesized from CO and H2 is a reaction in which the reaction described in the following formula 4 proceeds to the right (a reaction in which CO and H2 react to produce CH4 and H2O). CO+3H2⇔CH4+H2O (Formula 4) This formula 4 is also shown in a box showing the second catalytic reaction section 30 (hydrocarbon synthesis reaction section) in Fig. 1. In this box, the hydrocarbon synthesis catalyst cat2 used in the reaction is also shown diagrammatically. In addition, the equilibrium reaction of (Equation 3) also occurs at this site. Depending on the type of catalyst used in the second catalytic reaction section 30, it is possible to proceed with a Fischer-Tropsch (FT) synthesis reaction or the like, and therefore it is possible to synthesize various hydrocarbons from CO and H2, such as ethane, propane, butane, pentane, hexane, paraffin, olefin-based hydrocarbons, and the like.

[0055] As described later, the inventors have shown an example of a catalyst using ruthenium as the catalytically active component as the hydrocarbon synthesis catalyst cat2 disposed in the second catalytic reaction section 30, but heavy hydrocarbons are also synthesized in catalysts containing iron, cobalt, or the like as catalytically active components, and these types of heavy hydrocarbons are condensed as the temperature decreases and can be separated from the carrier gas. Therefore, the above-mentioned heavy hydrocarbon separation section 35 separates the hydrocarbon components separated in this manner.

[0056] The H2O produced in the water separation section 40 is separated and returned to the upstream side of the electrolysis reaction section 10 via a water return line 41 (water recycle line).

[0057] The CO2 produced in the carbon dioxide separation section 50 is separated and returned to the upstream side of the electrolysis reaction section 10 via a carbon dioxide return path 51 (carbon dioxide recycle line).

[0058] As a result, in this hydrocarbon production system 100, hydrocarbons are ultimately synthesized and can be supplied to the outside.

[0059] The above is an overview of the hydrocarbon production system 100. The configuration and role of each part will be described below. [Electrolytic reaction section] As described above, the electrolytic reaction section 10 consumes the power supplied in accordance with the above formulas 1 and 2 to decompose the inflowing H2O and CO2.

[0060] FIG. 2 shows a schematic cross-sectional configuration of the electrolytic reaction section 10. As shown in FIG. The figure shows an electrolysis cell unit U in which a plurality of units are stacked to form an electrolysis stack (not shown), and this electrolysis cell unit U includes an electrolysis cell 1, which includes an electrode layer 2 on one surface of an electrolyte layer 1a and a counter electrode layer 3 on the other surface. The electrode layer 2 serves as the cathode in the electrolysis cell 1, and the counter electrode layer 3 serves as the anode. Incidentally, this electrolysis cell unit U is supported by a metal support 4. Note that here, an example is shown in which a solid oxide electrolysis cell is used as the electrolysis cell 1.

[0061] The electrolyte layer 1a can be formed in a thin film state with a thickness of 10 μm or less. The constituent material thereof can be YSZ (yttria-stabilized zirconia), SSZ (scandia-stabilized zirconia), GDC (gadolinium-doped ceria), YDC (yttrium-doped ceria), SDC (samarium-doped ceria), LSGM (strontium-magnesium-doped lanthanum gallate), etc. In particular, zirconia-based ceramics are preferably used.

[0062] The electrolyte layer 1a is preferably formed by a low-temperature firing method (for example, a wet method using firing in a low-temperature range without firing in a high-temperature range exceeding 1100°C), a spray coating method (such as a thermal spray method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, or a cold spray method), a PVD method (such as a sputtering method or a pulse laser deposition method), or a CVD method. By using these film formation processes that can be used in a low-temperature range, it is possible to obtain an electrolyte layer 1a that is dense and has high airtightness and gas barrier properties without firing in a high-temperature range exceeding 1100°C. Therefore, damage to the metal support 4 can be suppressed, and the interdiffusion of elements between the metal support 4 and the electrode layer 2 can be suppressed, thereby realizing an electrolysis cell unit U with excellent performance and durability. In particular, it is preferable to use a low-temperature firing method or a spray coating method, since it is possible to realize a low-cost element. Furthermore, the use of a spray coating method is more preferable because it makes it easy to obtain an electrolyte layer 1a that is dense and has high airtightness and gas barrier properties in a low temperature range.

[0063] In addition, the electrolyte layer 1a is densely constructed in order to block gas leakage and to exhibit high ion conductivity. The density of the electrolyte layer 1a is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. When the electrolyte layer 1a is a uniform layer, the density is preferably 95% or more, and more preferably 98% or more. When the electrolyte layer 1a is constructed in a multi-layered form, it is preferable that at least a part of the electrolyte layer 1a includes a layer (dense electrolyte layer) having a density of 98% or more, and more preferably includes a layer (dense electrolyte layer) having a density of 99% or more. When such a dense electrolyte layer is included in a part of the electrolyte layer 1a, it is easy to form an electrolyte layer 1a that is dense, airtight, and has high gas barrier properties, even when the electrolyte layer 1a is constructed in a multi-layered form.

[0064] The electrode layer 2 can be provided in a thin layer state on a region on the front side of the metal support 4 that is larger than the region where the holes 4a are provided. When the electrode layer 2 is provided as a thin layer, the thickness can be, for example, about 1 μm to 100 μm, preferably 5 μm to 50 μm. With such a thickness, it is possible to ensure sufficient electrode performance while reducing the amount of expensive electrode layer material used to reduce costs. The entire region where the holes (through holes) 4a are provided is covered with the electrode layer 2. That is, the holes 4a are formed inside the region of the metal support 4 where the electrode layer 2 is formed. In other words, all the holes 4a are provided facing the electrode layer 2.

[0065] The material constituting the electrode layer 2 may be a composite material such as NiO-GDC, Ni-GDC, NiO-YSZ, Ni-YSZ, CuO-CeO2, or Cu-CeO2. In these examples, GDC, YSZ, and CeO2 may be called aggregates of the composite material. The electrode layer 2 is preferably formed by a low-temperature firing method (e.g., a wet method using firing in a low-temperature range without firing in a high-temperature range higher than 1100°C), a spray coating method (such as a thermal spray method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, or a cold spray method), a PVD method (such as a sputtering method or a pulsed laser deposition method), or a CVD method. By using these processes that can be used in a low-temperature range, a good electrode layer 2 can be obtained without firing in a high-temperature range higher than 1100°C. This is preferable because it is possible to realize an electrochemical element having excellent durability without damaging the metal support 4 and suppressing interdiffusion of elements between the metal support 4 and the electrode layer 2. Furthermore, the use of a low-temperature firing method is even more preferable because it facilitates handling of the raw materials.

[0066] The counter electrode layer 3 can be formed in a thin layer state on the surface of the electrolyte layer 1a opposite to the electrode layer 2. When the counter electrode layer 3 is a thin layer, the thickness can be, for example, about 1 μm to 100 μm, preferably 5 μm to 50 μm. With such a thickness, it is possible to reduce the amount of expensive counter electrode layer material used to reduce costs while ensuring sufficient electrode performance. As the material for the counter electrode layer 3, for example, composite oxides such as LSCF and LSM, ceria-based oxides, and mixtures thereof can be used. In particular, it is preferable that the counter electrode layer 3 contains a perovskite-type oxide containing two or more elements selected from the group consisting of La, Sr, Sm, Mn, Co, and Fe.

[0067] The electrolyte layer 1a, the electrode layer 2 and the counter electrode layer 3 are formed as thin films as described below, and the inventors call this being formed in a thin layer shape.

[0068] As described above, the electrolysis cell unit U is of a metal support type, and includes a metal support 4 as a support for the electrode layer 2, and a supply path forming member 5 that forms a U-shaped electrode layer side gas supply path 5a on the opposite side of the electrode layer 2 across the metal support 4. Furthermore, a large number of holes 4a are provided in the metal support 4, penetrating the front and back surfaces. Gases (H2O and CO2) supplied via the electrode layer side gas supply path 5a are subjected to electrolysis, and are supplied to the electrode layer 2 via the large number of holes 4a. Furthermore, the generated gases (H2, CO) flow out from the holes 4a.

[0069] On the other hand, a supply path forming member 6 for forming a counter electrode layer side gas supply path 6a is also provided on the counter electrode layer 3 side. As shown in the figure, this supply path forming member 6 is provided with many grooves on the counter electrode layer 3 side, and is configured to supply a carrier gas g2 (e.g., air, etc.) to this counter electrode layer side gas supply path 6a.

[0070] The metal support 4 supports the electrode layer 2, the electrolyte layer 1a, and the counter electrode layer 3, and serves as a support that maintains the strength of the electrolysis cell 1 and the entire electrolysis cell unit U. In this example, a plate-shaped metal support 4 is used as the metal support, but other shapes, such as a box shape or a cylindrical shape, are also possible. The metal support 4 may have a sufficient strength as a support to form the electrolysis cell unit U, and may have a thickness of, for example, about 0.1 mm to 2 mm, preferably about 0.1 mm to 1 mm, and more preferably about 0.1 mm to 0.5 mm. In this embodiment, the support is made of metal, but it may also be made of, for example, ceramics.

[0071] The metal support 4 has, for example, a plurality of holes 4a provided penetrating the front and back surfaces of the metal plate. For example, the holes 4a can be provided in the metal support 4 by mechanical, chemical, or optical drilling. The holes 4a have the function of allowing gas to pass from the back surface to the front surface of the metal support 4. The holes 4a may be provided at an angle to the gas advection direction (the front-to-back direction of the paper in FIG. 2).

[0072] By using ferritic stainless steel (an example of an Fe-Cr alloy) as the base material of the metal support 4, it is possible to bring the thermal expansion coefficient closer to that of YSZ (yttria-stabilized zirconia) or GDC (gadolinium-doped ceria, also known as CGO), which are used as materials for the electrode layer 2 and the electrolyte layer 1a. Therefore, the electrolysis cell unit U is less susceptible to damage even when temperature cycles of low and high temperatures are repeated. This is preferable because it allows for the realization of an electrolysis cell unit U with excellent long-term durability.

[0073] The supply path forming members 5 and 6 of the electrolysis cell unit U can be made of the same material as the metal support 4, and the thickness thereof can also be made approximately the same.

[0074] The metal support 4 and both supply path forming members 5 and 6 are electrically conductive, but are configured to be airtight, so that they function as separators that separate the supply paths 5a and 6a.

[0075] In the electrolysis operation, the electrolysis cell unit U having the above configuration supplies DC power from a power supply unit (shown as a battery in FIG. 2) between a pair of electrode layers 2 and 3 disposed on either side of the electrolyte layer 1a. In this embodiment, as shown in the figure, the electrode layer 2 side is negative and the counter electrode layer 3 side is positive. Depending on the configuration of the electrolysis cell unit U, the electrode layer 2 side may be positive and the counter electrode layer 3 side may be negative. Then, H2O and CO2, which are gases to be electrolyzed, are supplied to the electrode layer 2 from an electrolysis raw material supply unit (an upstream portion of the electrolysis reaction unit 10 in FIG. 1), and a carrier gas g2 is supplied to the counter electrode layer side, thereby causing the reactions shown in formulas 1 and 2 in the electrolysis cell 1 and allowing the decomposed gas to be extracted. Here, the supply of H2O may be either water or water vapor, or both. Therefore, in the present invention, an electrolysis cell device is constructed including at least an electrolysis cell unit U, an electrolysis raw material supply unit that supplies water and / or water vapor and carbon dioxide to the electrolysis cell unit U, and a power supply unit that supplies power.

[0076] In Fig. 2, the gases supplied (H2O, CO2) and the gases discharged (H2O, H2, CO, O2, CO2) in the electrolysis reaction are shown above and below the electrolysis cell unit U, but this is for ease of understanding. In reality, the electrode layer side gas supply path 5a and the counter electrode layer side gas supply path 6a are formed to extend in the front-to-back direction of the paper surface of Fig. 2. For example, the supply side gases (H2O, CO2) shown above the electrolysis cell unit U in Fig. 2 can be recovered from the front side of the paper surface, and the discharge side gases (H2O, H2, CO, O2, CO2) shown below the electrolysis cell 1 can be recovered from the back side of the paper surface (see Fig. 4 described later). In addition, in order to smoothly discharge O2 generated in the electrolysis reaction, a carrier gas g2 such as air can be flowed into the electrolysis cell unit U.

[0077] When H2O and CO2 are supplied to the electrolytic reaction unit 10 and electrolyzed, H2O has a lower electrolytic voltage than CO2 and is more easily electrolyzed. Therefore, if equal amounts of H2O and CO2 are supplied to the electrolytic reaction unit 10 to carry out an electrolytic reaction, the H2 concentration is likely to be higher than the CO concentration at the outlet of the electrolytic reaction unit 10, and unreacted CO2 is likely to remain.

[0078] [First catalytic reaction section (reverse water gas shift reaction section)] As described above, the first catalytic reaction unit 20 (reverse water gas shift reaction unit) causes a reverse water gas shift reaction, converts CO2 to CO using the supplied H2, and converts H2 to H2O. That is, in the electrolysis reaction unit 10 which supplies H2O and CO2 and electrolyzes them, the CO2 remaining without being decomposed is converted to CO.

[0079] The reaction here is as shown in formula 3, but this reaction is an endothermic reaction and an equilibrium reaction depending on the reaction temperature conditions. As a result, as explained above, it is necessary to select a catalyst that can cause the reaction shown in formula 3 at as high a temperature as possible (for example, 600°C to 800°C).

[0080] In describing catalysts in this specification, a component having catalytic activity may be referred to as a "catalytically active component", and a support that supports the catalytically active component may be referred to as a "support". As described below, the inventors have investigated various combinations of catalytically active components and supports, and found that certain combinations are preferable. This type of catalyst can be easily produced by carrying out an impregnation process in which a carrier (metal oxide carrier) is immersed in a solution containing catalytically active components (metal components), and then removed and dried / heat-treated, to obtain a carrier-supported catalyst (impregnated-supported catalyst) in which the catalytically active components are distributed on the carrier surface. This heat treatment is called a calcination process. The preparation and use of the catalyst will be described with reference to Figs. 11 and 12.

[0081] The preparation method described here is similar for various combinations of catalytically active components and carriers, except for the different starting materials. Figure 11 shows examples of the reverse water gas shift catalyst cat1 and the hydrocarbon synthesis catalyst cat2 according to the present invention. In the figure, the catalytically active component of the reverse water gas shift catalyst cat1 is indicated as ca1, and its carrier as cb1. On the other hand, for the hydrocarbon synthesis catalyst cat2, its catalytically active component is indicated as ca2, and its carrier as cb2.

[0082] As shown in Figure 11, in catalyst preparation, an aqueous solution of a compound containing metal components (metal catalysts) that become catalytically active components CA1 and CA2 is obtained, carriers CB1 and CB2 are added to the aqueous solution, and the impregnation-supporting process (a) is performed by stirring and impregnating the carriers CB1 and CB2. The carriers are then evaporated to dryness, dried, and then crushed and molded in the drying, crushing, and molding process (b), and the molded bodies obtained are then fired in air in the firing process (c), to obtain the target products (CAT1 and CAT2). Therefore, this form of catalyst is also called an impregnated supported catalyst.

[0083] In this case, the catalyst can be applied to the area where it is to be used and then fired, as shown in the example of reverse water gas shift catalyst cat1 in Fig. 12. Fig. 12(a) shows a coating and firing process in which the reverse water gas shift catalyst cat1 is applied to a metal support 4 having holes 4a therein to form a coating layer 20a, and then fired. Fig. 12(b) shows a pre-reduction treatment process in which H2 is passed through the reverse water gas shift catalyst cat1 to perform pre-reduction treatment before use.

[0084] When the calcination process is performed in air, the supported catalytic active components ca1 and ca2 are partially or entirely oxidized. Before using the catalyst, a so-called reduction pretreatment can be performed to reduce the oxidized catalytic active components and sufficiently increase their activity. Figure 12(b) shows the state in which a reducing gas (typically H2) is circulated over the surface of the catalyst to perform the reduction pretreatment.

[0085] (Catalyst used) As the reverse water gas shift catalyst cat1 to be used in the first catalytic reaction section 20, the inventors selected a catalyst that satisfies the following requirements.

[0086] A catalyst comprising a carrier cb1 mainly composed of a ceria-based metal oxide or a zirconia-based metal oxide, and at least one of nickel and iron as a catalytically active component ca1. Here, the ratio of the carrier cb1 to the entire catalyst is preferably 55% by weight or more, more preferably 60% by weight or more, and even more preferably 65% ​​by weight or more, in order to increase the strength of the catalyst cat1. The upper limit of this ratio can be, for example, 99.5% by weight, but if it is more than this, the catalytically active component ca1 cannot be sufficiently supported, and it may be difficult to obtain the effect of the reverse water gas shift catalyst cat1.

[0087] Furthermore, the ceria-based metal oxide may be ceria doped with at least one of gadolinium, samarium, and yttrium. The zirconia-based metal oxide may be zirconia stabilized with at least one of yttria and scandia.

[0088] In addition, since the reverse water gas shift reaction can be smoothly carried out, the amount of the catalytically active component ca1 is preferably 0.5% by weight or more, more preferably 1% by weight or more, and even more preferably 5% by weight or more. Also, even if the amount of the catalytically active component ca1 is increased too much, it becomes difficult to support the catalytically active component ca1 in a highly dispersed manner, making it difficult to obtain a significant improvement in catalytic activity, and the catalyst cost also increases, so the amount of the catalytically active component ca1 is preferably 35% by weight or less, more preferably 30% by weight or less, and even more preferably 25% by weight or less.

[0089] Furthermore, it is also preferable to add either or both of nickel and iron to the catalytically active component ca1 and support copper as the further catalytically active component ca1. In this configuration, the amount of copper supported is equal to or less than the amount of either or both of nickel and iron as the main catalytically active component ca1 supported by the catalytically active component ca1.

[0090] The following describes test results of examples in which the catalytically active component ca1 and the carrier cb1 of the reverse water gas shift catalyst cat1 used in the first catalytic reaction section 20 are changed in various ways. As the catalytically active component ca1, Ni and Fe were examined and compared with Pt (platinum). As the support cb1, ZrO2 (zirconia), YSZ (yttria stabilized zirconia), GDC (gadolinium doped ceria), and CeO2 (ceria) were used as examples, and Al2O3 (alumina) was also investigated.

[0091] In the following explanation, Test Example 1 and Test Example 2 will be introduced. The difference between the two tests is that in the calcination of the reverse water gas shift catalyst cat1, the calcination temperature in Test Example 1 was set to 450°C, while the calcination temperature in Test Example 2 was set to a higher temperature of 600°C to 1000°C.

[0092] (Test Example 1) The test results of Examples (1 to 19) in which the carrier used as the catalyst in the first catalytic reaction section 20 was changed in various ways will be described. As catalytically active components, Ni, Fe, and Pt (platinum) were also examined. The supports used were ZrO2 (zirconia), YSZ (yttria stabilized zirconia), GDC (gadolinium doped ceria), and CeO2 (ceria), with Al2O3 (alumina) also being investigated.

[0093] (Catalyst preparation) In preparing the reverse water gas shift catalyst cat1, either or both of water-soluble nickel compounds (nickel nitrate, nickel chloride, nickel sulfate, nickel ammonium sulfate, nickel acetate, nickel oxalate, nickel citrate, etc.) and water-soluble iron compounds (iron nitrate, iron chloride, iron sulfate, ammonium iron sulfate, iron acetate, iron oxalate, iron citrate, etc.) are measured and dissolved in an aqueous solution according to the composition of the target catalyst. When supporting copper as a further catalytically active component ca1, a water-soluble copper compound (copper nitrate, copper chloride, copper sulfate, copper ammonium sulfate, copper acetate, copper oxalate, copper citrate, etc.) is similarly measured and dissolved in an aqueous solution. A predetermined amount of carrier powder (ceria, zirconia, GDC, YSZ, Al2O3) is added to the aqueous solution, stirred, impregnated, evaporated to dryness, dried, then crushed, molded, and calcined in air. This impregnation is the "impregnation-supporting step" referred to in the present invention, and the result is the "impregnated-supported catalyst". In the following examples, nickel nitrate hexahydrate, iron nitrate nonahydrate, and copper nitrate trihydrate were used for preparation, respectively. The Pt-based catalyst was prepared using tetraammine platinum hydroxide.

[0094] In the preparation of the catalyst, the temperatures for the evaporation to dryness, drying, and calcination can be within a commonly used temperature range. In the following examples, the temperatures for Test Example 1 were 80°C, 80°C, and 450°C, respectively.

[0095] Table 1 shows Examples 1 to 19 of the reverse water gas shift catalyst cat1 of the present invention. The horizontal axis indicates the type of carrier cb1, the amount of metal supported as a catalytically active component (weight %; indicated as wt.% in the table), the amount of CO adsorption (ml / g), and the BET surface area (m 2 / g). The CO adsorption amount was measured after the catalyst was subjected to a reduction pretreatment in a hydrogen atmosphere at 350° C. for 1 hour.

[0096] [Table 1]

[0097] (Catalytic activity test) The catalytic activity test was performed using a mixed gas of 50% H2-50% CO2 (a mixed gas containing H2 and CO2 in a 1:1 (volume ratio)) as the reaction gas, with a GHSV (Gas Hourly Space Velocity) of 10,000 / h and the reaction temperature changed in 50°C increments from 600°C to 800°C. Before the catalytic activity test, the catalyst was subjected to a reduction pretreatment at 600° C. while passing hydrogen gas through the catalyst layer. As test results, the CO2 conversion rate (%), CO concentration (%) and CH4 concentration (%) at the reaction section outlet are shown in Table 2.

[0098] The CO2 conversion rate (%) was calculated according to the following formula based on the gas analysis results at the catalyst layer outlet. [CH4 concentration] + [CO concentration] / ([CH4 concentration] + [CO concentration] + [CO2 concentration])

[0099] As described above, it is desirable for the reverse water gas shift catalyst cat1 used in the first catalytic reaction section 20 (reverse water gas shift reaction section) to have a high CO2 conversion rate (%) on the high temperature side (for example, around 600 to 800°C).

[0100] [Table 2]

[0101] (Test Example 2) The test results of Examples (20 to 29) of Test Example 2 will be described below. As catalytically active components, Ni and Fe were examined, and the addition of Cu was also examined. The carriers used in the experiments are CeO2 (ceria) and ZrO2 (zirconia), with Al2O3 (alumina) also being considered.

[0102] (Catalyst preparation) The reverse water gas shift catalyst cat1 used in Test Example 2 was prepared in the same manner as in Test Example 1, except that the calcination temperature was changed to 600°C, 800°C, and 1000°C.

[0103] Table 3 shows the catalysts prepared in Examples (20 to 29).

[0104] [Table 3]

[0105] (Catalytic activity test) The catalytic activity test was performed using a mixed gas containing H2 and CO2 in a 1:1 (volume ratio) ratio as the reaction gas, with a GHSV of 10,000 / h and the reaction temperature changed from 600°C to 800°C in 50°C increments. Before the catalytic activity test, the catalyst was subjected to a reduction pretreatment at 600° C. while passing hydrogen gas through the catalyst layer. As test results, the CO2 conversion rate (%), CO concentration (%) and CH4 concentration (%) at the reaction section outlet are shown in Table 4.

[0106] [Table 4]

[0107] For reference, the equilibrium values ​​(calculated values) of the CO2 conversion rate under these experimental conditions are shown in Table 4.

[0108] Iron-zirconia catalyst and iron-alumina catalyst The test results of the iron-zirconia catalyst when the calcination temperatures were 450°C, 600°C, 800°C, and 1000°C are shown in Examples 8, 22, 26, and 29, respectively. On the other hand, the test results of the iron-alumina catalyst when the calcination temperatures were 450°C, 600°C, and 800°C are shown in Examples 14, 23, and 27, respectively. As can be seen from these results, although the metal loadings are slightly different, the iron-zirconia catalyst has a higher activity in the reverse water gas shift reaction than the iron-alumina catalyst. In addition, the iron-zirconia catalyst has a very high catalytic activity not only when the calcination temperature was 450°C, but also when the calcination temperature was increased to 600°C, 800°C, and 1000°C, and the CO2 conversion rate reached near the equilibrium value at any calcination temperature.

[0109] Nickel-ceria catalyst The test results for calcination temperatures of 450°C, 600°C, 800°C, and 1000°C are shown in Examples 4, 20, 24, and 28, respectively. As can be seen from these results, the nickel-ceria catalyst has extremely high catalytic activity not only at a calcination temperature of 450°C, but also at higher calcination temperatures of 600°C, 800°C, and 1000°C, and the CO2 conversion rate reaches close to the equilibrium value at any calcination temperature.

[0110] Nickel-alumina catalyst The test results when the calcination temperature was 450°C are shown in Example 7. The results showed that the nickel-alumina catalyst had a lower CO2 conversion rate than the nickel-ceria catalyst mentioned above.

[0111] Nickel-copper-ceria catalyst The test results for calcination temperatures of 450°C, 600°C, and 800°C are shown in Examples 6, 21, and 25, respectively. These results show that the nickel-copper-ceria catalyst tends to have a slightly lower CO2 conversion rate when the calcination temperature is high, such as 600°C or 800°C, but is superior to the iron-alumina catalyst with the same calcination temperature conditions mentioned above. In addition, with the nickel-copper-ceria catalyst with a calcination temperature of 450°C, the CO2 conversion rate reaches close to the equilibrium value.

[0112] Usefulness as a reverse water-gas shift catalyst As described above, iron-zirconia catalysts and nickel-ceria catalysts exhibit extremely high reverse water-gas shift catalytic activity even when the calcination temperature is changed to various values, such as 450°C to 1000°C. Therefore, even when used in combination with a solid oxide electrolysis cell operated at high temperatures, for example, around 600°C to 800°C, they are useful because they can easily ensure high performance and durability.

[0113] From the above results, as described above, the reverse water gas shift catalyst cat1 used in the first catalytic reaction section 20 can be a catalyst composed of a carrier cb1 mainly composed of a ceria-based metal oxide or a zirconia-based metal oxide, and at least one or both of nickel and iron supported as catalytically active components ca1.

[0114] Furthermore, the ceria-based metal oxide as the carrier cb1 may be ceria doped with at least one of gadolinium, samarium, and yttrium.

[0115] Furthermore, the zirconia-based metal oxide as the carrier cb1 can be zirconia stabilized with at least one of yttria and scandia.

[0116] Furthermore, it is also preferred to add either or both of nickel and iron to the catalytically active component ca1 and support copper as a further catalytically active component ca1.

[0117] By using the reverse water gas shift catalyst cat1 in the first catalytic reaction section 20 (reverse water gas shift reaction section), the reverse water gas shift reaction can be carried out at a CO2 conversion rate (%) equal to or higher than that of a Pt catalyst, which is highly active but very expensive, at around 600 to 1000°C. It should be noted that the test was conducted under extremely high GHSV conditions of 10,000 / h. It is therefore possible to carry out the reverse water gas shift reaction with a higher CO2 conversion rate (%) by reducing the GHSV below 10,000 / h, i.e., by increasing the amount of catalyst used relative to the amount of gas to be treated.

[0118] [Combination of electrolysis reactor and reverse water gas shift reactor] In the above description, the electrolysis reaction unit 10 and the reverse water gas shift reaction unit 20 are individually provided in the illustrated order along the gas advection direction in accordance with the system configuration shown in FIG. The reaction in the electrolytic reaction section 10 may be an exothermic reaction depending on the reaction conditions, while the reaction in the reverse water gas shift reaction section 20 may be an endothermic reaction. Therefore, by integrating these two reaction sections 10 and 20, the thermal efficiency of the system can be improved. FIG. 3 shows the configuration in which these two reaction sections 10 and 20 are combined and integrated, and both parts are enclosed to show that they are integrated. The reaction in the case where they are integrated in this way is also shown in the same box. Basically, the above-mentioned formulas 1, 2, and 3 are carried out. When the electrolytic reaction section 10 and the reverse water gas shift reaction section 20 are combined and integrated, it is preferable to surround them with a heat insulating member, since this allows efficient exchange of heat between the electrolytic reaction section 10 and the reverse water gas shift reaction section 20. In addition, the electrolytic reaction section 10 and the reverse water gas shift reaction section 20 may be connected using a heat conductive member in order to transfer heat generated in the electrolytic reaction section 10 to the reverse water gas shift reaction section 20.

[0119] [Electrolysis cell unit equipped with both electrolysis reaction section and reverse water gas shift reaction section] Based on the above concept, it is preferable to provide a reverse water gas shift reactor 20 in the electrolysis cell unit U serving as the electrolysis reaction section 10. This is because, when a solid oxide electrolysis cell operating at about 600 to 800°C is used as the electrolysis cell 1, the reverse water gas shift catalyst cat1 of the present application, which exhibits high activity at about 600 to 800°C, can use the electrolysis reaction section 10 and the reverse water gas shift reactor 20 in approximately the same temperature range. In this case as well, it is only necessary that the gas that has passed through the electrolytic reaction section 10 is guided to the reverse water gas shift reaction section 20 and the reverse water gas shift reaction occurs.

[0120] An electrolysis cell unit U equipped with such a reverse water gas shift reactor 20 is shown in Fig. 4. Fig. 4 is a drawing of the electrolysis cell unit U shown in cross section in Fig. 2, including the gas advection direction.

[0121] As shown in the figure, the cross sections of the electrolysis cell units U are basically the same. That is, the electrolysis cell unit U also includes an electrolysis cell 1 in which an electrode layer 2 and a counter electrode layer 3 are formed with an electrolyte layer 1a sandwiched therebetween, a metal support 4 that functions as a support for the electrolysis cell 1 and also functions as a separator, and supply channel forming members 5 and 6, and is configured to form an electrode layer side gas supply channel 5a and a counter electrode layer side gas supply channel 6a. More specifically, as is clear from the figure, when the metal support 4 is viewed in the gas advection direction, a hole 4a is provided at a position corresponding to the electrolysis cell 1, but no hole is provided downstream of the electrode layer 2. Therefore, the metal support 4 serves as a separator that effectively separates the gas supplied to the electrode layer 2 and released from the electrode layer 2 from the gas supplied to the counter electrode layer 3 and released from the counter electrode layer 3.

[0122] In this example, however, the reverse water gas shift catalyst cat1 described above is applied to the inner surface of the electrode layer side gas supply channel 5a (the inner surface on the supply channel side of the supply channel forming member 5, the surface of the metal support 4 opposite to the surface on which the electrode layer 2 is formed, and the surfaces of the plurality of holes 4a). This coating layer 20a is indicated by a thick solid line. Furthermore, the electrode layer side gas supply passage 5a is extended beyond the electrolytic reaction section 10, and the coating layer 20a is also provided on this extension side.

[0123] As a result, the electrode layer side gas supply path 5a of the electrolysis cell unit U serves as an exhaust path for exhausting at least H2 generated in the electrode layer 2, and the electrolysis reaction section 10 and the reverse water gas shift reaction section 20 are integrally provided in the electrolysis cell unit U.

[0124] In this configuration, the metal support 4 acts as a separator to separate H generated in the electrode layer 2 and O generated in the counter electrode layer 3, and at least a portion of the separator on the H discharge path side serves as a reverse water-gas shift reaction section 20. The electrolysis cell units U configured in this manner can be stacked in the left-right direction in Figures 2 and 4 to form a so-called electrolysis cell module (not shown) in which a large number of electrolysis cell units U are stacked and electrically connected. Naturally, useful gases can be generated across multiple layers.

[0125] Based on the concept of combining the electrolytic reaction unit 10 and the reverse water gas shift reaction unit 20 (the electrode layer side gas supply passage 5a of the electrolytic reaction unit 10 serves as the reverse water gas shift reaction unit 20), the inventors conducted an experiment by storing a granular reverse water gas shift catalyst cat1 in the electrode layer side gas supply passage 5a. FIG. 5 shows a cross section of the electrolysis cell unit U used in this experiment.

[0126] A specific description will be given below with reference to Fig. 5, which shows a cross-sectional view of the electrolysis cell unit U. Here, a metal-supported solid oxide electrolysis cell was used as the electrolysis cell 1. A metal substrate was prepared by providing a plurality of through holes (holes 4a) in a ferritic stainless steel metal plate having a thickness of 0.3 mm by laser processing as the metal support 4. An electrode layer 2 and an intermediate layer 2a were laminated in order on the metal substrate, and an electrolyte layer 1a was laminated on the intermediate layer 2a of the metal substrate so as to cover the intermediate layer 2a. Furthermore, a reaction prevention layer 7 and a counter electrode layer 3 were laminated in order on the electrolyte layer 1a to prepare the electrolysis cell 1. Note that a mixture of NiO powder and GDC powder was used as the material for forming the electrode layer 2, GDC powder was used as the material for forming the intermediate layer 2a, 8YSZ (8 mol% yttria-stabilized zirconia) powder was used as the material for forming the electrolyte layer 1a, GDC powder was used as the material for forming the reaction prevention layer 7, and a mixture of GDC powder and LSCF powder was used as the material for forming the counter electrode layer 3. The thicknesses of the electrode layer 2, intermediate layer 2a, electrolyte layer 1a, reaction prevention layer 7, and counter electrode layer 3 were about 25 μm, about 10 μm, about 5 μm, about 5 μm, and about 20 μm, respectively. The performance and durability of the electrolytic cell 1 can be improved by providing the intermediate layer 2a between the electrode layer 2 and the electrolyte layer 1a, or by providing the reaction prevention layer 7 between the electrolyte layer 1a and the counter electrode layer 3. The intermediate layer 2a and the reaction prevention layer 7 are preferably formed by a low-temperature firing method (for example, a wet method using a firing process in a low-temperature range that does not include a firing process in a high-temperature range higher than 1100° C.), a spray coating method (such as a thermal spray method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, or a cold spray method), a PVD method (such as a sputtering method or a pulsed laser deposition method), or a CVD method. These processes that can be used in the low temperature range make it possible to obtain a good intermediate layer 2a and reaction prevention layer 7 without using firing in a high temperature range, for example, higher than 1100° C. This is preferable because it allows the electrolysis cell 1 to be realized with excellent performance and durability without damaging the metal support 4. Furthermore, the use of a low-temperature firing method is even more preferable because it allows the raw materials to be easily handled.

[0127] For the electrolysis cell unit U obtained as described above, we investigated the performance improvement when a granular reverse water gas shift catalyst cat1 was placed in the electrode layer side gas supply passage 5a (which also serves as an exhaust passage for the gas electrolyzed in the electrolysis reaction section 10).

[0128] Results without reverse water gas shift catalyst cat1 An electrolysis reaction was carried out while supplying a gas containing H2O and CO2 to the electrolysis cell unit U, and the ratio of H2 to CO in the outlet gas of the electrolysis cell unit U was measured using a gas chromatograph. The results are shown in Table 5 below. These experimental results are described as Comparative Examples A1 and A2.

[0129] [Table 5]

[0130] Results when reverse water gas shift catalyst cat1 is installed A granular catalyst obtained by supporting approximately 10% Ni on the same 8YSZ carrier as in Example 2 was placed as the reverse water gas shift catalyst cat1, and an electrolysis reaction was carried out while supplying a gas containing H2O and CO2 to the electrolysis cell unit U, and the ratio of H2 to CO in the outlet gas of the electrolysis cell unit U was measured using a gas chromatograph. The results are shown in Table 6. This experimental result is described as Example A1.

[0131] [Table 6]

[0132] From the above comparative experiments, it was found that in the electrolytic cell unit U in which the electrolytic cell 1 was formed in a thin layer on the metal support 4 and the reverse water-gas shift reaction section 20, which produces CO using CO and the H by the reverse water-gas shift reaction, was provided in the electrode layer side gas supply path 5a, which serves as a discharge path for the electrolyzed gas, the composition ratio of CO to H produced by electrolysis could be increased.

[0133] In comparison between an electrolysis cell unit U that does not house the reverse water gas shift catalyst cat1 in the electrode layer side gas supply passage 5a (which serves as an exhaust passage for electrolyzed gas) and an electrolysis cell unit U that does house the catalyst cat1, the hydrogen / carbon monoxide ([H2 / CO]) ratio at the outlet is about 10 or more to about 5, and the amount of CO advantageous for various hydrocarbon synthesis can be secured by combining the reaction in the electrolysis reaction section 10 and the reaction in the reverse water gas shift reaction section 20, which is preferable. In addition, since the thermal efficiency of the hydrocarbon production system 100 can be improved by adopting the methanation reaction of CO rather than the methanation reaction of CO2, the amount of CO can be secured by combining the reaction in the electrolysis reaction section 10 and the reaction in the reverse water gas shift reaction section 20, which is preferable. This is because, while 2 moles of H2O are generated when 1 mole of CO2 is methanated, only 1 mole of H2O is generated when 1 mole of CO is methanated, the hydrocarbon production system 100 that adopts the methanation reaction of CO can suppress the loss of latent heat and sensible heat equivalent to 1 mole of H2O as a whole system. By appropriately adjusting the ratio of H2O and CO2 introduced into the electrolytic reaction section 10, the reaction conditions of the electrolytic reaction section 10 (electrolytic voltage, reaction temperature, etc.), and the reaction conditions of the reverse water gas shift reaction section 20 (amount of catalyst used, GHSV, reaction temperature, etc.), the hydrogen / carbon monoxide ([H2 / CO]) ratio at the outlet of the reverse water gas shift reaction section 20 can be adjusted to a value suitable for the downstream second catalytic reaction section 30 (hydrocarbon synthesis reaction section) (for example, H2 / CO=3, which is the equivalent ratio for the CO methanation reaction).

[0134] [A heat exchanger is installed between the electrolysis reactor and the reverse water gas shift reactor] In the above explanation, the electrolysis reaction section 10 and the first catalytic reaction section (reverse water gas shift reaction section) 20 are mainly integrated together, but it is also possible to adopt a configuration in which the two sections 10, 20 are separate sections and a heat exchanger 11 is provided between the two sections 10, 20 to allow heat transfer between the two sections. This configuration is shown in FIG. 6 corresponding to FIG. 1. The hollow double lines indicate heat transfer between the two sections. With this configuration, the temperature of each section 10, 20 can be appropriately controlled.

[0135] The inventors call the system consisting of the electrolysis reaction section 10 and the reverse water gas shift reaction section 20 described above an "electrolysis reaction system."

[0136] [Second catalytic reaction section (hydrocarbon synthesis reaction section)] At least H2 and CO are flowed into this second catalytic reaction section 30 (hydrocarbon synthesis reaction section), and hydrocarbons (methane and various hydrocarbons having a carbon number of 2 or more) and the like are produced by catalytic reaction.

[0137] (Example of a hydrocarbon synthesis catalyst) As activity tests of the catalyst (hydrocarbon synthesis catalyst cat2) used in this second catalytic reaction section 30, the inventors conducted the following evaluation tests 1, 2, 3, 4, and 5. Here, evaluation tests 1 to 4 are tests to determine whether a gas having a desired number of calories or more (called a high-calorie gas) can be produced, and evaluation test 5 is a confirmation test of heavy hydrocarbons that are obtained simultaneously during production.

[0138] As an example of the hydrocarbon synthesis catalyst cat2, catalysts were prepared by changing the carrier and catalytically active components in various ways. As the catalytically active component ca2, Ru, Ru with Mo, V, Fe, Co, etc., and Ni were examined. As the carrier cb2, ZrO2, Al2O3, SiO2, MgO, and TiO2 were examined.

[0139] (Catalyst preparation) The hydrocarbon synthesis catalyst cat2 is also prepared by the method described in FIGS. That is, according to the composition of the target catalyst, a water-soluble ruthenium compound (ruthenium nitrate, ruthenium chloride, ruthenium sulfate, ruthenium ammonium sulfate, ruthenium acetate, ruthenium oxalate, ruthenium citrate, etc.) is measured and dissolved in an aqueous solution to obtain the catalyst. When supporting molybdenum, vanadium, iron, or cobalt as a further catalytically active component, the water-soluble metal compounds are similarly measured and dissolved in an aqueous solution, and the catalytically active component is impregnated and supported on a predetermined amount of carrier particles (ZrO2, Al2O3, SiO2, MgO, TiO2), for example, by carrying the catalyst, and then performing necessary processing steps such as drying, calcination, and reduction, to obtain the hydrocarbon synthesis catalyst cat2. The catalysts in the following examples were prepared using an aqueous solution of ruthenium chloride, an aqueous solution of ammonium molybdate, an aqueous solution of vanadyl oxalate, an aqueous solution of iron nitrate, or an aqueous solution of cobalt nitrate, and when both ruthenium and a catalytically active component other than ruthenium were supported, they were prepared using a sequential support method (a two-stage support method in which a catalytically active component other than ruthenium is first supported on a support, and then ruthenium is supported). Evaluation test 5 is described separately.

[0140] (Evaluation Test 1) In evaluation test 1, a mixed gas containing 12.4% CO, 24.8% CO2, 37.2% H2, 12.4% H2O, and the remainder N2 was used as the reaction gas, and the activity test of the hydrocarbon synthesis catalyst cat2 was performed at a reaction temperature between 275°C and 360°C with a GHSV of 4000 / h (WET base). Note that the reaction gas in this case is an example of an assumed model in which a co-electrolytic reaction of water and carbon dioxide is performed in the electrolytic reaction section 10 under conditions where the electrolytic reaction rate of carbon dioxide is low, and the mixed gas of CO, CO2, H2, and H2O after the reverse water gas shift reaction of carbon dioxide is performed in the reverse water gas shift reaction section 20 installed in the subsequent stage is introduced into the hydrocarbon synthesis reaction section 30 to perform the hydrocarbon synthesis reaction.

[0141] The following two indicators were used to organize the test results.

[0142] 1. Estimated CO2 removal hydrocarbon conversion rate = [carbon number of hydrocarbons in outlet gas] / [carbon number in outlet gas - carbon number of outlet CO2] This index indicates the conversion rate to hydrocarbons when CO2 is removed from the outlet gas of the hydrocarbon synthesis reaction section 30 obtained by the catalytic reaction, and it is preferable that this index is high.

[0143] 2.C1-C4 calorific value (MJ / Nm 3 )=Σ(Nn×HN) / Σ Nn Nn [mol]: Number of moles of Cn hydrocarbons in the catalytic reaction gas (n = 1 to 4) HN [MJ / m 3 (N)]: Calorific value of Cn hydrocarbons in the catalytic reaction gas [H1 = 39.8, H2 = 69.7, H3 = 99.1, H4 = 128.5] This index indicates the amount of C1 to C4 components contained in the outlet gas of the hydrocarbon synthesis reaction section 30 obtained by the catalytic reaction, and if this value exceeds 39.8, it can be confirmed that hydrocarbons such as ethane, propane, and butane are produced in addition to methane. Regarding the evaluation test 1, Tables 7 and 8 shown below show Examples B1 to B3 of the hydrocarbon synthesis catalyst cat2 of the present invention.

[0144] [Table 7]

[0145] [Table 8]

[0146] As shown in Tables 7 and 8, it was confirmed that hydrocarbons can be synthesized from a mixed gas of CO, CO2, H2, and H2O using a catalyst in which ruthenium is supported on an alumina carrier, or a catalyst in which molybdenum or vanadium is supported in addition to ruthenium, as the hydrocarbon synthesis catalyst cat2. From the above results, the above-mentioned hydrocarbon production system 100 can produce a C1-C4 calorific value of 39 MJ / Nm 3 It was confirmed that it is possible to generate high calorie gases of the above levels.

[0147] (Evaluation Test 2) In evaluation test 2, a mixed gas containing 0.45% CO, 18.0% CO2, 71.55% H2, and 10.0% H2O was used as the reactant gas, and the activity test of the hydrocarbon synthesis catalyst cat2 was performed at a GHSV of 5000 / h (DRY basis) and a reaction temperature between about 230° C. and about 330° C. Note that the reactant gas in this case is an example of an assumed model in which a mixed gas obtained when a co-electrolysis reaction of water and carbon dioxide is carried out in the electrolysis reaction section 10 under conditions where the electrolysis reaction rate of carbon dioxide is low is introduced into the hydrocarbon synthesis reaction section 30 to carry out the hydrocarbon synthesis reaction.

[0148] The following two indicators were used to organize the test results.

[0149] 1 Hydrocarbon conversion rate = [carbon number of hydrocarbons in outlet gas] / [carbon number in outlet gas] This index indicates the proportion of carbon that is converted to hydrocarbons without being converted to CO2 out of the total carbon that is input, and it is preferable that this index is high.

[0150] 2. Estimated CO2 removal hydrocarbon conversion rate = [carbon number of hydrocarbons in outlet gas] / [carbon number in outlet gas - carbon number of outlet CO2] This index indicates the conversion rate to hydrocarbons when CO2 is removed from the outlet gas of the hydrocarbon synthesis reaction section obtained by the catalytic reaction, and it is preferable that this index is also high.

[0151] For evaluation test 2, the catalysts used (Examples B4 to B15 and Comparative Example B1) are shown in Table 9, and the test results are shown in Table 10.

[0152] [Table 9]

[0153] [Table 10]

[0154] (Evaluation Test 3) In the evaluation test 3, a mixed gas (H2 / CO=3) containing H2 and CO at a volume ratio of 3:1 was used as the reaction gas, and the activity test of the hydrocarbon synthesis catalyst cat2 was performed at a GHSV of 2000 / h and a reaction temperature between 235°C and approximately 330°C. In this activity test, a catalyst (Examples B16 and B17) in which iron or cobalt was supported on a titania carrier in addition to ruthenium was used. The reaction gas in this case is an example of a model in which a mixed gas obtained by adding carbon monoxide to hydrogen obtained by electrolysis of water in the electrolysis reaction section 10, or a mixed gas of hydrogen and carbon monoxide obtained by separating moisture or carbon dioxide as necessary from a gas obtained by a co-electrolysis reaction of water and carbon dioxide is introduced into the hydrocarbon synthesis reaction section 30 to perform a hydrocarbon synthesis reaction.

[0155] The results of evaluation test 3 are shown in Table 11.

[0156] [Table 11]

[0157] As shown in Table 11, it was confirmed that hydrocarbons can be synthesized from a mixed gas containing H2 and CO by using a catalyst in which ruthenium and iron or cobalt are supported on a titania carrier as the hydrocarbon synthesis catalyst cat2.

[0158] The above-mentioned hydrocarbon production system 100 produces a C1-C4 calorific value of 39 MJ / Nm 3 It was confirmed that it is possible to generate high calorie gases of the above levels.

[0159] (Evaluation Test 4) In evaluation test 4, a mixed gas containing 0.5% CO, 20.0% CO2, and 79.5% H2 was used as the reaction gas, and the activity test of the hydrocarbon synthesis catalyst cat2 was performed at a GHSV of 5000 / h (dry basis) and a reaction temperature between about 260° C. and about 290° C. The reaction gas in this case corresponds to the mixed gas obtained by separating and removing moisture from the reaction gas used in evaluation test 2.

[0160] Regarding evaluation test 4, the test results are shown in Table 12.

[0161] [Table 12]

[0162] From the above results, comparing the test results of Evaluation Test 2 and Evaluation Test 4, it was found that by separating water upstream of the second catalytic reaction section 30 (hydrocarbon synthesis reaction section), the hydrocarbon conversion rate in the hydrocarbon synthesis reaction section 30 can be improved even at a lower reaction temperature, and the activity of the catalyst can be improved. Therefore, the configuration of a hydrocarbon production system 100 shown in Fig. 9, which will be described later in another embodiment, is also effective.

[0163] (Evaluation Test 5) Catalyst preparation In this evaluation test 5 as well, the hydrocarbon synthesis catalyst cat2 was prepared by the method described with reference to Figs. Catalyst cat2 has ruthenium and iron as catalytic active components and titania as carrier. Ruthenium chloride solution was used in the ruthenium component supporting process, and iron nitrate solution was used in the iron component supporting process. As mentioned above, other aqueous solutions of compounds containing ruthenium or iron can also be used.

[0164] The specific preparation method is as follows. A titania carrier as a metal oxide carrier was impregnated with an aqueous solution containing iron at a predetermined concentration, and iron was supported on the titania carrier. This iron-supported titania was impregnated with an aqueous solution of ruthenium chloride at a predetermined concentration. Then, a wet reduction treatment was performed using an aqueous solution of hydrazine, and iron-ruthenium-supported titania was obtained as a hydrocarbon synthesis catalyst cat2.

[0165] The amounts of iron and ruthenium supported in the hydrocarbon synthesis catalyst cat2 can be set arbitrarily depending on the concentration of each aqueous solution and the impregnation conditions. In the hydrocarbon synthesis catalyst cat2 in evaluation test 5, a spherical titania support having a diameter of 2 to 4 mm was used, and iron-ruthenium supported titania (2 wt.% Ru / 2 wt.% Fe / TiO2) with an iron content (supported amount) of 2 wt.% and a ruthenium content (supported amount) of 2 wt.% was used.

[0166] Reduction pretreatment In the test, a pre-reduction treatment shown in FIG. 12(b) was performed. Specifically, nitrogen gas containing 10% hydrogen was flowed as a hydrogen-containing gas into the catalyst storage section which constitutes the hydrocarbon synthesis reaction section 30, while the temperature of the catalyst section was maintained at 350°C, and hydrogen treatment (pre-reduction treatment) of the catalyst before use was performed for one hour. The hydrogen-containing gas used in the reduction pretreatment can be a mixed gas of hydrogen and nitrogen in this way, thereby reducing the amount of hydrogen consumed. Therefore, in this reduction pretreatment, it is preferable to use a mixed gas of hydrogen and nitrogen with a hydrogen concentration of 20 volume % or less, for example, and in this embodiment, the reduction pretreatment of the hydrocarbon synthesis catalyst cat2 is performed using a hydrogen-containing gas containing 10 volume % hydrogen and the remainder being nitrogen gas.

[0167] Test conditions In evaluation test 5, a mixed gas containing H2 and CO in a volume ratio of 3:1 (H2 / CO=3) was used as the reaction gas, and the hydrocarbon synthesis catalyst cat2 was tested under the condition of GHSV=2000 / h. The reaction pressure in this test was 0.6 MPa.

[0168] Heavy Hydrocarbon Verification Test 1 Using the hydrocarbon synthesis catalyst cat2 (2wt.%Ru / 2wt.%Fe / TiO2) that had been subjected to the above-mentioned reduction pretreatment, a hydrocarbon synthesis test was carried out for approximately 80 hours at a reaction temperature of 275°C. As a result, gas analysis using a gas chromatograph confirmed that methane (CH4) was the main component, and C2 to C6 hydrocarbons such as ethane, propane, and butane were being continuously produced at the outlet of the catalytic reaction section. On the other hand, when the wax-like deposit obtained in the air-cooled portion (corresponding to the heavy hydrocarbon separation portion 35) provided below the catalytic reaction portion was analyzed, it was identified as straight-chain higher aliphatic hydrocarbons (average chain length: C26) by IR and C13 NMR analysis. In addition, when the precipitates on the hydrocarbon synthesis catalyst cat2 were extracted with a solvent and analyzed by MS, peaks were obtained every 14 mass units at 268 to 604 (maximum intensity at 352). From these results, it was found that higher hydrocarbons of C19 to C43 (most abundant C25) were precipitated on the hydrocarbon synthesis catalyst cat2.

[0169] Heavy Hydrocarbon Verification Test 2 As in the above test, the hydrocarbon synthesis catalyst cat2 (2wt.%Ru / 2wt.%Fe / TiO2) was used, and the reduction pretreatment was performed at 550°C, and the hydrocarbon synthesis test was performed at a reaction temperature of 325°C for about 270 hours. As a result, it was confirmed by gas analysis using a gas chromatograph that methane (CH4) was the main component and C2-C6 hydrocarbons such as ethane, propane, and butane were continuously generated at the outlet of the catalytic reaction section. On the other hand, it was confirmed that a wax-like deposit (straight-chain higher aliphatic hydrocarbons (average chain length: C18)) was obtained in the air-cooled area (corresponding to the heavy hydrocarbon separation section 35) provided below the catalytic reaction section. Furthermore, it was found that higher hydrocarbons of C19 to C60 (C29 is the most abundant) were deposited on the hydrocarbon synthesis catalyst cat2.

[0170] Hydrocarbon production with separate hydrocarbon synthesis catalysts Furthermore, a different hydrocarbon synthesis catalyst cat2 (2wt.%Ru / 2wt.%Co / TiO2) from the above-mentioned hydrocarbon synthesis catalyst cat2 (2wt.%Ru / 2wt.%Fe / TiO2) was used, and the reduction pretreatment was performed at 450°C, and a hydrocarbon synthesis test was performed at temperatures of 250°C to 270°C for about 380 hours. As a result, it was confirmed by gas analysis using a gas chromatograph that methane (CH4) was the main component and hydrocarbons such as ethane, propane, and butane were continuously generated at the outlet of the catalytic reaction section. On the other hand, it was confirmed that a wax-like deposit (straight-chain higher aliphatic hydrocarbons (average chain length: C27)) was obtained in the air-cooled area (corresponding to the heavy hydrocarbon separation section 35) provided below the catalytic reaction section. Furthermore, it was found that higher hydrocarbons of C23 to C60 (C37 is the most abundant) were deposited on the hydrocarbon synthesis catalyst cat2.

[0171] From the evaluation test 5, it was confirmed that by using the hydrocarbon synthesis catalyst cat2 according to the present invention, not only lower saturated hydrocarbons but also heavy hydrocarbons can be produced.

[0172] From the above results, as shown above, a catalyst in which at least ruthenium is supported as the catalytically active component CA2 on the metal oxide carrier CB2 can be used in the second catalytic reaction section 30 (hydrocarbon synthesis reaction section). Furthermore, it is preferable to support at least one of molybdenum, vanadium, iron, and cobalt as the catalytically active component CA2.

[0173] It has been found that the hydrocarbon synthesis catalyst cat2 is preferably a catalyst in which at least ruthenium is supported on a metal oxide carrier cb2, with the amount of ruthenium supported being preferably 0.1% by weight or more and 5% by weight or less, and that it is preferable for the metal oxide carrier cb2 to further support, in addition to ruthenium, at least one of molybdenum, vanadium, iron and cobalt as a catalytically active component ca2.

[0174] Here, the amount of at least one of molybdenum, vanadium, iron and cobalt supported can be 0.2% by weight or more and 6% by weight or less.

[0175] Moreover, among such hydrocarbon synthesis catalysts cat2, the highly active catalysts had a carbon monoxide adsorption capacity of 0.4 ml / g or more.

[0176] [Heavy Hydrocarbon Separation Section] The gas reaching the heavy hydrocarbon separation section 35 is cooled, so that the heavy hydrocarbons contained in the gas discharged from the hydrocarbon synthesis reaction section 30 are condensed, and the heavy hydrocarbons can be taken out. For example, in the hydrocarbon synthesis reaction section 30 using the 2 wt.% Ru / 2 wt.% Fe / TiO2 catalyst described above, a mixed gas (H2 / CO=3) containing H2 and CO at a volume ratio of 3:1 was introduced and the reaction was carried out at 275°C, whereby linear higher aliphatic hydrocarbons with an average chain length of 26 carbon atoms could be taken out in the heavy hydrocarbon separation section 35, and when the reaction was carried out at 325°C, linear higher aliphatic hydrocarbons with an average chain length of 18 carbon atoms could be taken out in the heavy hydrocarbon separation section 35.

[0177] [Water separation section] The water separation section 40 is provided with a condenser, which adjusts the temperature and pressure of the inflowing gas containing H2O to a predetermined level, condenses the gas, and takes out the water to the outside.

[0178] [Carbon dioxide separation section] For example, a PSA is provided in this section 50, which separates CO2 from the incoming CO2-containing gas by adsorbing it onto an adsorbent under a predetermined temperature and pressure, and then desorbs the separated CO2 from the adsorbent, thereby separating the CO2 satisfactorily. The separated CO2 can be returned to the front of the electrolysis reaction section 10 via the carbon dioxide return path 51 and reused. It should be noted that the carbon dioxide separation section and the water separation section may be integrated into one separation section by using PSA or the like.

[0179] [Another embodiment] (1) In the above embodiment, the CO2 separated in the carbon dioxide separation section 50 is returned to the upstream side of the electrolysis reaction section 10. However, in the hydrocarbon production system 100 according to the present invention, the conversion of CO2 to CO is mainly performed in the reverse water gas shift reaction section 20. Therefore, the CO2 may be returned to the upstream side of the reverse water gas shift reaction section 20. This configuration is shown in FIG.

[0180] (2) In the above embodiment, no particular mention was made regarding H2 in the gas obtained from the hydrocarbon synthesis reaction section 30. However, a hydrogen separation section (shown as H2 separation section in the figure) 60 that separates H2 using a hydrogen separation membrane or the like may be provided to separate H2 for separate use. This configuration is shown in FIG. 8. In this example, the H2 separated in the hydrogen separation section 60 may be returned to the upstream side of the reverse water gas shift reaction section 20 and used for the reverse water gas shift reaction. In this case as well, hydrogen is separated from the hydrogen separation section 60 into a branch path.

[0181] (3) In the above embodiment, the water separation section 40 is provided downstream of the hydrocarbon synthesis reaction section 30, but as shown in Fig. 9, the water separation section 40 may be provided between the reverse water gas shift reaction section 20 and the hydrocarbon synthesis reaction section 30. The main function of this water separation section 40 is to facilitate the hydrocarbon synthesis reaction.

[0182] (4) In the above embodiment, both H2O and CO2 are supplied to the electrolysis reaction unit 10 for the electrolysis reaction, but as shown in Fig. 10, a system in which only H2O is supplied to the electrolysis reaction unit 10 for the electrolysis reaction may be used. In this case, carbon consumed in the hydrocarbon synthesis is input to the reverse water gas shift reaction unit 20 as carbon dioxide.

[0183] (5) In the above embodiment, an example was shown in which a solid oxide electrolysis cell was used as the electrolysis cell 1 in the electrolysis reaction section 10. However, the electrolysis cell 1 may also be an alkaline electrolysis cell or a polymer membrane electrolysis cell.

[0184] (6) In the above embodiment, the electrolytic reaction section 10 and the first catalytic reaction section 20 are integrated into one structure, but it is also possible to integrate the second catalytic reaction section 30 in addition to the reaction sections 10 and 20. An example of this structure is shown in Fig. 13. In this figure, 30a indicates a coating layer of the hydrocarbon synthesis catalyst cat2. In this configuration, each of the reaction sections 10, 20, 30 can be constructed on a metal support 4, and the metal support 4 acts as a separator for separating the produced hydrocarbons from oxygen.

[0185] (7) In the above embodiment, the hydrocarbon production system 100 is provided with the reverse water gas shift reactor 20. However, as shown in FIG. 14, it is also possible to obtain a high calorie gas by electrolyzing water in the electrolysis reactor 10 without using the reverse water gas shift reactor 20 and inputting at least one selected from carbon monoxide and carbon dioxide upstream of the hydrocarbon synthesis reactor 30.

[0186] (8) In the above embodiment, an example was shown in which hydrocarbons such as methane were synthesized in the hydrocarbon synthesis reaction section 30. However, depending on how the hydrocarbon synthesis catalyst used in the hydrocarbon synthesis reaction section 30 is selected, it is also possible to synthesize chemical raw materials from hydrogen, carbon monoxide, etc. introduced into the hydrocarbon synthesis reaction section 30. [Explanation of symbols]

[0187] 1 Electrolysis cell 1a Electrolyte layer 2 electrode layer 3 Counter electrode layer 4 Metal support (support / separator) 4a hole 5 Supply path forming member (separator) 6 Supply path forming member (separator) 10 Electrolytic reaction section 20 First catalytic reaction section (reverse water gas shift reaction section) 20a Coating layer 30 Second catalytic reaction section (hydrocarbon synthesis reaction section) 40 Water separation section 50 Carbon dioxide separation section 60 Hydrogen separation section U Electrolysis cell unit Cat1 reverse water gas shift catalyst ca1 Catalytically active component (metal component) cb1 Metal oxide carrier (carrier) Cat2 Hydrocarbon Synthesis Catalyst ca2 Catalytic active component (metal component) cb2 Metal oxide carrier (carrier)

Claims

1. an electrolytic reaction section that converts water into hydrogen by an electrolytic reaction, or converts water and carbon dioxide into hydrogen and carbon monoxide by an electrolytic reaction, and a catalytic reaction section that converts a product generated in the electrolytic reaction section into at least hydrocarbons by a catalytic reaction; The catalytic reaction section is provided with a hydrocarbon synthesis catalyst in which at least ruthenium is supported on a metal oxide support, and in addition to the ruthenium, at least one of molybdenum and vanadium is supported; The amount of ruthenium supported is 0.1% by weight or more and 5% by weight or less, The hydrocarbon production system, wherein the amount of at least one of molybdenum and vanadium supported is 0.2% by weight or more and 6% by weight or less.

2. 2. The hydrocarbon production system according to claim 1, wherein the catalytic reaction section converts the product produced in the electrolytic reaction section into a high-calorie gas containing at least lower saturated hydrocarbons through a catalytic reaction.

3. A hydrocarbon production system as described in claim 1 or 2, wherein the carbon monoxide adsorption amount of the hydrocarbon synthesis catalyst is 0.4 ml / g or more.

4. A hydrocarbon production system according to any one of claims 1 to 3, having a reverse water gas shift catalytic reaction section.

5. A hydrocarbon production system as described in any one of claims 1 to 4, comprising a water separation section at least one of the upstream and downstream stages of the catalytic reaction section.

6. A hydrocarbon production system as described in claim 5, comprising a recycle line for recycling water separated in the water separation section.

7. A hydrocarbon production system according to any one of claims 1 to 6, further comprising a carbon dioxide separation section downstream of the catalytic reaction section.

8. A hydrocarbon production system as described in claim 7, comprising a recycle line for recycling carbon dioxide separated in the carbon dioxide separation section.

9. A hydrocarbon production system according to any one of claims 1 to 8, further comprising a heavy hydrocarbon separation section downstream of the catalytic reaction section.

10. A hydrocarbon production system according to any one of claims 1 to 9, wherein the electrolytic reaction section has an electrolytic cell in which at least an electrode layer, an electrolyte layer and a counter electrode layer are formed on a support.

11. The hydrocarbon production system of claim 10, wherein the support is a metal.

12. A hydrocarbon production system comprising: an impregnated-supported catalyst obtained through an impregnation-supporting step of impregnating and supporting ruthenium on a metal oxide support; and an impregnation-supporting step of impregnating and supporting at least one of molybdenum and vanadium in addition to the ruthenium, and the impregnated-supported catalyst is disposed in a catalytic reaction section according to any one of claims 1 to 11.

13. A method for producing a hydrocarbon production system, comprising the steps of: an impregnation-supporting step of impregnating and supporting ruthenium on a metal oxide support; and an impregnation-supporting step of impregnating and supporting at least one of molybdenum and vanadium in addition to the ruthenium; and disposing the impregnated-supported catalyst in the catalytic reaction section described in claim 12.

14. A method for operating a hydrocarbon production system according to any one of claims 1 to 12, comprising operating the hydrocarbon production system after subjecting the catalytic reaction section to reduction pretreatment.

15. A method for operating a hydrocarbon production system as described in any one of claims 4 to 12, comprising operating the hydrocarbon production system after subjecting a reverse water gas shift catalytic reaction section constituting the catalytic reaction section to reduction pretreatment.

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