JP7640339B2 - Hydrocarbon production system, and method of producing and operating the system - Google Patents

Description

The present invention relates to a hydrocarbon production system that produces hydrocarbons from at least water and carbon dioxide, and to a production method and an operation method of this hydrocarbon production system.

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.

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).

Special table 2016-522166 publication

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

In view of this situation, the main objective of the present invention is to provide a hydrocarbon production system that can efficiently produce high-calorie gases, for example, containing at least low-molecular-weight hydrocarbons, by securing the hydrogen and carbon monoxide necessary for hydrocarbon synthesis using water and carbon dioxide as raw materials.

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.

The hydrocarbon production system of this configuration comprises an electrolytic reaction section and a catalytic reaction section, and in the former electrolytic reaction section, at least hydrogen, or hydrogen and carbon monoxide, required for the synthesis of hydrocarbons, is obtained from water or water and carbon dioxide. Here, if only hydrogen is to be obtained in the electrolytic reaction section, at least one selected from carbon monoxide and carbon dioxide may be supplied before the catalytic reaction section.

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.

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.

As described above, the catalytic reaction section functions as a hydrocarbon synthesis reaction section. When the hydrocarbons produced in this section become a gas containing at least lower saturated hydrocarbons, the gas synthesized in the hydrocarbon synthesis reaction section (total gas containing a plurality of lower saturated hydrocarbons) becomes a high-calorie gas having a calorific value of, for example, ³⁹ MJ/Nm3 or more.
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.

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, "wt %" is synonymous with "mass %" (the same applies below).

By using ruthenium as a catalytically active component, it is possible to perform 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 will increase. Therefore, the above range is preferable.

The fourth characteristic configuration of the present invention is as follows:
The feature is that, in addition to ruthenium, at least one of molybdenum, vanadium, iron and cobalt is supported on the metal oxide support.

In this configuration, by adding a specific 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, hydrocarbon synthesis can be performed with higher catalytic activity than when ruthenium is used alone.

The fifth characteristic configuration of the present invention is
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.

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 added element supported is less than 0.2 wt%, the synthesis effect may decrease. On the other hand, if it is more than 6 wt%, the cost will increase. Therefore, the above range is preferable.

The sixth characteristic configuration of the present invention is
The carbon monoxide adsorption amount of the hydrocarbon synthesis catalyst is 0.4 ml/g or more.

By having a carbon monoxide adsorption amount of 0.4 ml/g or more, the surface area of the catalyst that contributes to hydrocarbon synthesis is secured widely, and the catalytically active components are well distributed on the surface of the metal oxide carrier, thereby maintaining high hydrocarbon synthesis ability.

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

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.

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

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

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.

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.

By adopting this configuration, the water separated in the water separation section can be used as new water for hydrocarbon synthesis.

The tenth characteristic configuration of the present invention is
The feature is that a carbon dioxide separation section is provided downstream of the catalytic reaction section.

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. As a result, it is possible to increase the calorific value per unit volume, which is an important requirement for a high-calorie gas, which is one of the objectives of the present invention.

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.

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

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.

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

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.

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 robust support that is thin but has sufficient strength, making it possible to effectively cause an electrolytic reaction while reducing the amount of material used to compose 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.

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

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.

The fifteenth characteristic configuration of the present invention is
The impregnated supported catalyst obtained through the impregnation step of impregnating a metal oxide support with ruthenium is disposed in the catalytic reaction section of the hydrocarbon production system described above.

By impregnating a metal oxide support with ruthenium, it is possible to obtain a good catalyst to be placed in the catalytic reaction section of the hydrocarbon production system described above, thereby obtaining a high-performance hydrocarbon production system.

As the catalyst to be housed in this type of catalytic reaction section, it is more preferable to use an impregnated catalyst obtained through an impregnation process in which a metal oxide carrier 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.

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

By carrying out this pre-reduction treatment, the catalytic ability of the hydrocarbon synthesis catalyst in the catalytic reaction section can be fully utilized.

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.

By carrying out this pre-reduction treatment, the catalytic activity of the reverse water gas shift catalyst in the reverse water gas shift reaction section can be fully demonstrated.

Diagram showing the configuration of a hydrocarbon production system Schematic diagram showing the configuration of the electrolytic reaction section FIG. 1 shows the configuration of a system that integrates an electrolysis reactor and a reverse water gas shift reactor. Schematic diagram of an electrolysis cell unit equipped with an electrolysis reactor and a reverse water-gas shift reactor. 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. A diagram showing the configuration of a system equipped with a heat exchanger between the electrolysis reactor and the reverse water gas shift reactor. FIG. 1 shows another configuration of a hydrocarbon production system in which CO ₂ is introduced into a reverse water gas shift reaction section. FIG. 1 is a diagram showing another configuration of a hydrocarbon production system equipped with a hydrogen separation unit. FIG. 1 shows yet another configuration of a hydrocarbon production system including a water separation section prior to a hydrocarbon synthesis reaction section. 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. An explanatory diagram showing the preparation state of the catalyst An explanatory diagram showing the catalyst coating and baking state and pre-reduction treatment 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. FIG. 1 shows another configuration of a hydrocarbon production system.

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.

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).

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 CH ₄ (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, the term "hydrocarbon" is a concept that includes all of these, and is also collectively referred to as "hydrocarbons."

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 (CnHm, _H2O and _CO2 , in the order of appearance) 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 Figure 1, for reuse. 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 serves as a carbon-closed system in which CO ₂ is not substantially released outside the system.

In the diagram, the gas flowing into each part is shown before each part, and the gas released from that part is shown afterwards.

In the electrolysis reaction section 10, H ₂ O and CO ₂ as starting materials are introduced and electrolyzed therein. H ₂ O is decomposed into H ₂ and O ₂ , and a part of CO ₂ is decomposed into CO and O ₂ and released.

The reaction is described as follows:
2H ₂ O → 2H ₂ +O ₂ (Formula 1)
_2CO2 → 2CO + _O2 (Equation 2)
These formulas 1 and 2 are also shown in the box representing the electrolytic reaction section 10 in FIG.

In the first catalytic reaction unit 20 (reverse water gas shift reaction unit), _H2 and _CO2 are introduced and a reverse water gas shift reaction occurs therein, and _CO2 becomes CO and _H2 becomes _H2O , which are then released.

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 the following equation 3 proceeds to the right (in the direction in which _CO2 and _H2 react to produce CO and _H2O ).
CO ₂ + H ₂ ⇔ CO + H ₂ O (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 in this box.

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+3H ₂ ⇔ _{CH 4} +H ₂ O (Formula 4)
This formula 4 is also shown in the box representing 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.
Furthermore, 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 various hydrocarbons such as ethane, propane, butane, pentane, hexane, paraffin, olefin-based hydrocarbons, etc. can be synthesized from CO and _H2 .

As described later, the inventors have shown an example of a catalyst that uses ruthenium as the catalytically active component of the hydrocarbon synthesis catalyst cat2 placed in the second catalytic reaction section 30, but heavy hydrocarbons are also synthesized with catalysts that contain iron, cobalt, or the like as catalytically active components, and these types of heavy hydrocarbons condense as the temperature decreases and can be separated from the transport gas. Therefore, the aforementioned heavy hydrocarbon separation section 35 separates the hydrocarbon components separated in this manner.

The H ₂ O 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).

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 line 51 (carbon dioxide recycle line).

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

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 H ₂ O and CO ₂ .

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

The electrolyte layer 1a can be formed in a thin film state with a thickness of 10 μm or less. Its constituent materials include YSZ (yttria-stabilized zirconia), SSZ (scandia-stabilized zirconia), GDC (gadolinium-doped ceria), YDC (yttrium-doped ceria), SDC (samarium-doped ceria), and LSGM (strontium-magnesium-doped lanthanum gallate). Zirconia-based ceramics are particularly suitable.

This electrolyte layer 1a 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 exceeding 1100 ° C), a spray coating method (thermal spraying, aerosol deposition, aerosol gas deposition, powder jet deposition, particle jet deposition, cold spray, etc.), a PVD method (sputtering, pulse laser deposition, etc.), a CVD method, etc. These film formation processes that can be used in a low-temperature range can 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., for example. 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 electrolytic 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, etc., because it is possible to realize a low-cost element. Furthermore, spray coating is more preferable because it is easy to obtain a dense electrolyte layer 1a with high airtightness and gas barrier properties at low temperatures.

The electrolyte layer 1a is densely constructed to prevent 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-layer structure, 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. If 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-layer structure.

The electrode layer 2 can be provided in the form of a thin layer on the front surface of the metal support 4 in an area larger than the area in which the holes 4a are provided. When the electrode layer 2 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 ensure sufficient electrode performance while reducing the amount of expensive electrode layer material used to reduce costs. The entire area in which the holes (through holes) 4a are provided is covered with the electrode layer 2. In other words, the holes 4a are formed inside the area in the metal support 4 in which the electrode layer 2 is formed. In other words, all the holes 4a are provided facing the electrode layer 2.

The material for the electrode layer 2 may be a composite material such as NiO-GDC, Ni-GDC, NiO-YSZ, Ni-YSZ, CuO-CeO ₂ , or Cu-CeO ₂ . In these examples, GDC, YSZ, and CeO ₂ 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 a firing process in a low-temperature range without firing in a high-temperature range higher than 1100°C), a spray coating method (thermal spraying, aerosol deposition, aerosol gas deposition, powder jet deposition, particle jet deposition, cold spray, or other method), a PVD method (sputtering, pulse laser deposition, or other 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, for example. Therefore, it 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, it is even more preferable to use a low-temperature firing method because it makes it easier to handle the raw materials.

The counter electrode layer 3 can be formed as a thin layer 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.

The electrolyte layer 1a, electrode layer 2, and counter electrode layer 3 are formed as thin films as described below, and the inventors call this a "thin layer formation."

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 formed in the metal support 4, penetrating the front and back surfaces. Gases (H ₂ O and CO ₂ ) 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 (H ₂ , CO) flow out from the holes 4a.

On the other hand, on the counter electrode layer 3 side, a supply path forming member 6 is provided to form a counter electrode layer side gas supply path 6a. As shown in the figure, this supply path forming member 6 has 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.

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 electrolytic cell 1 and the entire electrolytic 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.

The metal support 4 has, for example, a plurality of holes 4a that penetrate 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).

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

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 can be approximately the same.

The metal support 4 and the two supply path forming members 5 and 6 are conductive, but are constructed to be airtight, so they act as separators that separate the supply paths 5a and 6a.

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 1 a. 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, the gases to be electrolyzed, H ₂ O and CO _2, are supplied to the electrode layer 2 from the electrolysis raw material supply section (the upstream portion of the electrolysis reaction section 10 in FIG. 1 ) and a carrier gas g2 is supplied to the counter electrode layer side, whereby the reactions shown in formulas 1 and 2 are caused in the electrolysis cell 1 and the decomposed gas can be taken out. Here, the supply of H ₂ O 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 section that supplies water and/or water vapor and carbon dioxide to the electrolysis cell unit U, and a power supply section that supplies power.

In Fig. 2, the gases supplied in the electrolysis reaction ( _H2O , _CO2 ) and the gases discharged ( _H2O , _H2 , CO, _O2 , _CO2 ) 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 passage 5a and the counter electrode layer side gas supply passage 6a are formed to extend in the front-to-back direction of the paper surface of Fig. 2, and for example, the supply side gas ( _H2O , _CO2 ) described above the electrolysis cell unit U in Fig. 2 can be recovered from the front side of the paper surface, and the discharge side gas ( _H2O , _H2 , CO, _O2 , _CO2 ) described 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.

When _H2O and _CO2 are supplied to the electrolytic reaction unit 10 for electrolysis, _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.

[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 _H2 O. That is, in the electrolysis reaction unit 10, which supplies _H2O and _CO2 and electrolyzes them, the remaining _CO2 that is not decomposed is converted to CO.

The reaction here is as shown in Equation 3, but this reaction is an endothermic reaction and an equilibrium reaction that depends 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 Equation 3 at as high a temperature as possible (for example, 600°C to 800°C).

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 is produced by carrying out an impregnation step in which a carrier (metal oxide carrier) is immersed in a solution containing catalytically active components (metal components), and then removed, dried, and heated to easily 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 treatment. The preparation and use of the catalyst will be described with reference to Figures 11 and 12.

The preparation method described here is similar for various combinations of catalytically active components and carriers, except that the starting materials are different. Figure 11 shows examples of a reverse water gas shift catalyst cat1 and a 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.

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 support process (a) is performed by stirring and impregnating the carriers, followed by evaporation to dryness, drying, and then a drying, crushing, and molding process (b) in which the carriers are crushed and molded, and a firing process (c) is performed in which the molded body obtained is fired in air to obtain the target product (cat1, cat2). Therefore, this form of catalyst is also called an impregnated supported catalyst.

In this case, the catalyst can be applied to the portion where it is to be used and then calcined, as shown in Fig. 12 using the reverse water gas shift catalyst cat1 as an example. Fig. 12(a) shows a coating and calcination 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 calcined. Fig. 12(b) shows a pre-reduction process in which _H2 is passed through the reverse water gas shift catalyst cat1 before it is used.

When the calcination treatment 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 H ₂ ) is passed over the surface of the catalyst to perform the reduction pretreatment.

(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.

A catalyst composed of a carrier cb1 mainly composed of ceria-based metal oxide or zirconia-based metal oxide, and at least one or both of nickel and iron as catalytically active components ca1. Here, the ratio of 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, since this can 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.

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.

In addition, since the reverse water gas shift reaction can be smoothly carried out, the amount of catalytically active component CA1 supported is preferably 0.5% by weight or more, more preferably 1% by weight or more, and even more preferably 5% by weight or more. Furthermore, even if the amount of catalytically active component CA1 supported is increased too much, it becomes difficult to support the catalytically active component CA1 in a highly dispersed manner, making it difficult to achieve a significant improvement in catalytic activity and increasing the catalyst cost, so the amount of catalytically active component CA1 supported is preferably 35% by weight or less, more preferably 30% by weight or less, and even more preferably 25% by weight or less.

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

Hereinafter, 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 variously changed will be described.
As the catalytically active component ca1, Ni and Fe were examined and compared with Pt (platinum).
As the carrier cb1, ZrO ₂ (zirconia), YSZ (yttria stabilized zirconia), GDC (gadolinium doped ceria), and CeO ₂ (ceria) were used as examples, and Al ₂ O ₃ (alumina) was also considered.

In the following explanation, we will introduce Test Example 1 and Test Example 2. 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 is set to 450°C, while in Test Example 2, the calcination temperature is set to the higher temperature of 600°C to 1000°C.

(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 carriers investigated were ZrO ₂ (zirconia), YSZ (yttria stabilized zirconia), GDC (gadolinium doped ceria), and CeO ₂ (ceria) as examples, with Al ₂ O ₃ (alumina) also being considered.

(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.) are quantitatively determined and dissolved in an aqueous solution according to the composition of the target catalyst. When supporting copper as a further catalytically active component ca1, water-soluble copper compounds (copper nitrate, copper chloride, copper sulfate, copper ammonium sulfate, copper acetate, copper oxalate, copper citrate, etc.) are quantitatively determined and dissolved in an aqueous solution. A predetermined amount of carrier powder (ceria, zirconia, GDC, YSZ, Al ₂ O ₃ ) is added to the aqueous solution, stirred, impregnated, evaporated to dryness, dried, then crushed, molded, and calcined in air. This impregnation is referred to as the "impregnation-supporting step" in the present invention, and the resultant product 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 catalyst using Pt was prepared using tetraammine platinum hydroxide.

The temperatures for the evaporation to dryness, drying, and calcination in the above catalyst preparation can be within the commonly used temperature range, but in the following example, in Test Example 1, the temperatures were 80°C, 80°C, and 450°C, respectively.

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 %; expressed as wt. % in the table), the amount of CO adsorption (ml/g), and the BET surface area (m ² /g).
The amount of adsorbed CO was measured after the catalyst was subjected to a reduction pretreatment in a hydrogen atmosphere at 350° C. for 1 hour.

(Catalytic activity test)
The catalytic activity test was performed using a mixed gas of 50% H ₂ -50% CO ₂ (a mixed gas containing H ₂ and CO ₂ in a 1:1 (volume ratio)) as the reaction gas, under conditions of a GHSV (Gas Hourly Space Velocity) of 10,000/h, while changing the reaction temperature from 600°C to 800°C in 50°C increments.
Before carrying out 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 outlet of the reaction section are shown in Table 2.

The _CO2 conversion rate (%) was calculated according to the following formula based on the gas analysis results at the outlet of the catalyst layer.
[CH ₄ concentration] + [CO concentration] / ([CH ₄ concentration] + [CO concentration] + [CO ₂ concentration])

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).

(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.
As the support, CeO ₂ (ceria) and ZrO ₂ (zirconia) are given in the examples, and Al ₂ O ₃ (alumina) is also under consideration.

(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.

Table 3 shows the catalysts prepared for each of the examples (20-29).

(Catalytic activity test)
The catalytic activity test was performed using a mixed gas containing _H2 and _CO2 in a 1:1 (volume ratio) as the reaction gas, under the condition of a GHSV of 10,000/h, while changing the reaction temperature from 600°C to 800°C in 50°C increments.
Before carrying out 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 outlet of the reaction section are shown in Table 4.

For reference, the equilibrium values (calculated values) of the _CO2 conversion rate under these experimental conditions are shown in Table 4.

Iron-zirconia catalyst and iron-alumina catalyst The test results for the iron-zirconia catalyst when the calcination temperature is 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 for the iron-alumina catalyst when the calcination temperature is 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 loading amount is slightly different, the iron-zirconia catalyst has a superior activity in performing 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 is 450°C, but also when the calcination temperature is increased to 600°C, 800°C, and 1000°C, and the _CO2 conversion rate reaches the vicinity of the equilibrium value at any calcination temperature.

The test results for the nickel-ceria catalyst 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 very 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 near the equilibrium value at any calcination temperature.

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 described above.

Nickel-copper-ceria catalyst 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 has a tendency to slightly decrease in _CO2 conversion 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 described above. In addition, the nickel-copper-ceria catalyst with a calcination temperature of 450°C has a _CO2 conversion rate approaching the equilibrium value.

As described above, the iron-zirconia catalyst and the nickel-ceria catalyst exhibit very 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 used in a high temperature range, for example, around 600°C to 800°C, high performance and durability can be easily ensured, making them useful.

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

Furthermore, the ceria-based metal oxide used as the carrier cb1 can be ceria doped with at least one of gadolinium, samarium, and yttrium.

The zirconia-based metal oxide as the carrier cb1 can also be zirconia stabilized with at least one of yttria and scandia.

Furthermore, it is also preferable 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.

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 performed 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. Therefore, it is possible to carry out the reverse water gas shift reaction with a higher _CO2 conversion rate (%) under conditions where the GHSV is lower than 10,000/h, i.e., by increasing the amount of catalyst used relative to the amount of gas to be treated.

[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, and 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. Also, the reaction in the case where they are integrated in this way is shown in the same box. Basically, the above-mentioned formulas 1, 2, and 3 are carried out. In addition, 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, in order to transfer heat generated in the electrolytic reaction section 10 to the reverse water gas shift reaction section 20, the electrolytic reaction section 10 and the reverse water gas shift reaction section 20 may be connected using a heat conductive member.

[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 electrolytic cell unit U serving as the electrolytic reaction unit 10. This is because, when a solid oxide electrolytic cell operating at about 600 to 800°C is used as the electrolytic cell 1, the reverse water gas shift catalyst cat1 of the present application, which has high activity at about 600 to 800°C, can use the electrolytic reaction unit 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 so as to cause the reverse water gas shift reaction.

Figure 4 shows an electrolysis cell unit U equipped with such a reverse water gas shift reaction section 20. Figure 4 shows the electrolysis cell unit U shown in cross section in Figure 2, including the gas advection direction.

As shown in the figure, the cross sections of the electrolysis cell units U are basically the same.
That is, this electrolysis cell unit U is also configured to include 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 path forming members 5 and 6, and is configured to form an electrode layer side gas supply path 5a and a counter electrode layer side gas supply path 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.

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.

As a result, the electrode layer side gas supply path 5a of the electrolytic cell unit U serves as an exhaust path for exhausting at least _H2 generated in the electrode layer 2, and the electrolytic reaction section 10 and the reverse water gas shift reaction section 20 are integrally provided in the electrolytic cell unit U.

In this configuration, the metal support 4 acts as a separator for separating _H2 generated in the electrode layer 2 from _O2 generated in the counter electrode layer 3, and at least a part of the separator on the _H2 exhaust side serves as a reverse water-gas shift reaction section 20.
The electrolysis cell units U thus configured 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.

Based on the concept of combining the electrolytic reaction section 10 and the reverse water gas shift reaction section 20 (the electrode layer side gas supply passage 5a of the electrolytic reaction section 10 is regarded as the reverse water gas shift reaction section 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.

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 an 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. 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 performance and durability of the electrolytic cell 1 can be improved. The intermediate layer 2a and the reaction prevention layer 7 are preferably formed by a low-temperature firing method (e.g., a wet method using a firing treatment in a low-temperature range that does not include a firing treatment 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 a good reaction prevention layer 7 without using firing in a high temperature range, for example, higher than 1100° C. This is preferable because it is possible to realize an electrolytic cell 1 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 makes it easier to handle the raw materials.

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 path 5a (which also serves as the exhaust path for the gas electrolyzed in the electrolysis reaction section 10).

Results when no reverse water gas shift catalyst cat1 was installed An electrolysis reaction was carried out while supplying 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.

Results when reverse water gas shift catalyst cat1 was installed As the reverse water gas shift catalyst cat1, a granular catalyst obtained by supporting about 10% Ni on an 8YSZ carrier similar to that in Example 2 was installed, 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.

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 _CO2 and the _H2 by the reverse water-gas shift reaction, was provided in the electrode layer side gas supply path 5a, which serves as an exhaust path for the electrolyzed gas, the composition ratio of CO to _H2 produced by electrolysis could be increased.

Comparing an electrolysis cell unit U that does not store the reverse water gas shift catalyst cat1 in the electrode layer side gas supply path 5a (which serves as an exhaust path for electrolyzed gas) with an electrolysis cell unit U that does store it, the hydrogen/carbon monoxide ([ _H2 /CO]) ratio at the outlet is from about 10 or more to about 5, which is preferable because combining the reaction in the electrolysis reaction unit 10 with the reaction in the reverse water gas shift reaction unit 20 ensures an amount of CO that is advantageous for synthesizing various hydrocarbons. In addition, since the thermal efficiency of the hydrocarbon production system 100 can be improved by adopting the CO methanation reaction rather than the _CO2 methanation reaction, combining the reaction in the electrolysis reaction unit 10 with the reaction in the reverse water gas shift reaction unit 20 is preferable because it ensures an amount of CO. This is because, while 2 moles of _H2O are produced when 1 mole of _CO2 is methanated, only 1 mole of _H2O is produced when 1 mole of CO is methanated, and therefore, the hydrocarbon production system 100, which employs the CO methanation reaction, can reduce the loss of latent heat and sensible heat equivalent to 1 mole of _H2O in the entire system.
In addition, 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).

[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 and 20 are separate sections and a heat exchanger 11 is provided between the two sections 10 and 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. In this configuration, the temperature of each section 10 and 20 can be appropriately controlled.

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."

[Second catalytic reaction section (hydrocarbon synthesis reaction section)]
At least _H2 and CO are introduced into the 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.

(Examples of Hydrocarbon Synthesis Catalysts)
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 obtained as the gas to be produced, and evaluation test 5 is a confirmation test of heavy hydrocarbons obtained simultaneously during production.

As an example of the hydrocarbon synthesis catalyst cat2, catalysts were prepared by changing the carrier and catalytically active _component 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.

(Catalyst Preparation)
The hydrocarbon synthesis catalyst cat2 is also prepared by the method described with reference to FIGS.
That is, an aqueous solution is obtained by dissolving a measured amount of a water-soluble ruthenium compound (ruthenium nitrate, ruthenium chloride, ruthenium sulfate, ruthenium ammonium sulfate, ruthenium acetate, ruthenium oxalate, ruthenium citrate, etc.) according to the composition of the target catalyst. When supporting molybdenum, vanadium, iron, or cobalt as an additional catalytically active component, the water-soluble metal compounds are similarly measured and dissolved in the aqueous solution, and the catalytically active component is, for example, impregnated and supported on a predetermined amount of carrier particles _{( ZrO2} , _Al2O3 , _SiO2 , MgO, _TiO2 ), and the catalyst is subjected to necessary treatment steps such as drying, calcination, and reduction to obtain a hydrocarbon synthesis catalyst cat2.
The catalysts in the following examples were prepared using an aqueous ruthenium chloride solution, an aqueous ammonium molybdate solution, an aqueous vanadyl oxalate solution, an aqueous iron nitrate solution, and an aqueous cobalt nitrate solution, and when both ruthenium and a catalytically active component other than ruthenium were supported, they were prepared using a successive 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.

(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 GHSV of 4000/h (wet basis) and a reaction temperature between 275° C. and 360° C. 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 carried out in the electrolytic reaction section 10 under conditions where the electrolytic reaction rate of carbon dioxide is low, and a mixed gas of CO, _CO2 , _H2 , and _H2O after the reverse water gas shift reaction of carbon dioxide is carried out in the reverse water gas shift reaction section 20 installed in the subsequent stage is introduced into the hydrocarbon synthesis reaction section 30 to carry out the hydrocarbon synthesis reaction.

The following two indicators were used to organize the test results:

1. _CO2 removal assumed 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.

2. C1-C4 calorific value (MJ/Nm ³ ) = Σ (Nn x HN) / Σ Nn
Nn [mol]: number of moles of Cn hydrocarbons in the catalytic reaction gas (n = 1 to 4)
HN [MJ/ ^m3 (N)]: Heat generation amount of Cn hydrocarbons in the catalytic reaction gas [H1 = 39.8, H2 = 69.7, H3 = 99.1, H4 = 128.5]
This index is an index showing 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.

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, it was confirmed that the above-mentioned hydrocarbon production system 100 can produce high-calorie gas with a C1-C4 calorific value of 39 MJ/Nm3 or ^more .

(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 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 230° C. and about 330° C. Note that the reaction 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.

The following two indicators were used to organize the test results:

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 fed in, and it is preferable for this index to be high.

2 _CO2 removal assumed 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.

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.

(Evaluation Test 3)
In the evaluation test 3, a mixed gas (H ₂ /CO=3) containing H ₂ 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 in addition to ruthenium was supported on a titania carrier 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 water 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.

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

As shown in Table 11, it was confirmed that hydrocarbons can be synthesized from a mixed gas containing H ₂ and CO using a catalyst in which ruthenium and iron or cobalt are supported on a titania carrier as the hydrocarbon synthesis catalyst cat2.

It was confirmed that the above-described hydrocarbon production system 100 can produce high-calorie gas with a C1-C4 calorific value of 39 MJ/Nm3 or ^more .

(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.

The test results for evaluation test 4 are shown in Table 12.

Comparing the test results of evaluation test 2 and evaluation test 4 from the above results, 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 the hydrocarbon production system 100 shown in Figure 9, which will be described later in another embodiment, is also effective.

(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.
The catalyst cat2 had ruthenium and iron as catalytic active components and titania as a carrier. A ruthenium chloride aqueous solution was used in the ruthenium component supporting step, and an iron nitrate aqueous solution was used in the iron component supporting step. As previously mentioned, aqueous solutions of other compounds containing ruthenium or iron can also be used.

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, thereby supporting iron 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, to obtain iron-ruthenium-supported titania as a hydrocarbon synthesis catalyst cat2.

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 carrier 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.

Pre-reduction treatment During the test, the pre-reduction treatment shown in FIG. 12(b) was carried out.
Specifically, while nitrogen gas containing 10% hydrogen was flowed as a hydrogen-containing gas into the catalyst housing section which constitutes the hydrocarbon synthesis reaction section 30, 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 the reduction pretreatment, it is preferable to use a mixed gas of hydrogen and nitrogen having 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.

Test Conditions In the evaluation test 5, a mixed gas containing _H2 and CO at 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.

Heavy Hydrocarbon Verification Test 1
Using the hydrocarbon synthesis catalyst cat2 (2 wt. % Ru/2 wt. % Fe/TiO ₂ ) 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, it was confirmed by gas analysis using a gas chromatograph that methane (CH ₄ ) 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 linear higher aliphatic hydrocarbons (average chain length: C26) by IR and C13 NMR analyses.
In addition, when the precipitates on the hydrocarbon synthesis catalyst cat2 were subjected to solvent extraction and MS analysis, 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.

Heavy Hydrocarbon Verification Test 2
As in the above test, a hydrocarbon synthesis catalyst cat2 (2 wt.% Ru/2 wt.% Fe/ _TiO2 ) was used, and reduction pretreatment was performed at 550°C, and a 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 to C6 hydrocarbons such as ethane, propane, and butane were continuously generated at the outlet of the catalytic reaction section. Meanwhile, it was confirmed that a wax-like deposit (straight-chain higher aliphatic hydrocarbons (average chain length: C18)) was obtained in the air-cooled area (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.

Production of Hydrocarbons with Another Hydrocarbon Synthesis Catalyst Furthermore, a different hydrocarbon synthesis catalyst cat2 (2 wt.% Ru/2 wt.% Co/TiO ₂ ) from the above-mentioned hydrocarbon synthesis catalyst cat2 (2 wt.% Ru/2 wt.% Fe/TiO ₂ ) was used, and 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 (CH ₄ ) 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 at the air-cooled portion (the portion 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.

Evaluation test 5 confirmed that the use of the hydrocarbon synthesis catalyst cat2 according to the present invention makes it possible to produce lower saturated hydrocarbons as well as heavy hydrocarbons.

From the above results, as previously shown, 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 this 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.

It was 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 0.1% by weight or more and 5% by weight or less, and that in addition to ruthenium, the metal oxide carrier cb2 is preferably further supported with at least one of molybdenum, vanadium, iron, and cobalt as a catalytically active component ca2.

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

In addition, among these hydrocarbon synthesis catalysts cat2, the carbon monoxide adsorption capacity of the highly active catalyst was 0.4 ml/g or more.

[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 above-mentioned 2 wt. % Ru/2 wt. % Fe/ _TiO2 catalyst, a mixed gas ( _H2 /CO=3) containing _H2 and CO at a ratio of 3:1 (volume ratio) was introduced and the reaction was carried out at 275°C, and 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.

[Water Separation Section]
A condenser is provided in this water separation section 40, and adjusts the temperature and pressure of the inflowing H ₂ O-containing gas to a predetermined level, condensing the gas and removing the condensed water to the outside.

[Carbon dioxide separation section]
For example, a PSA is provided in this section 50, which separates _CO2 from the inflowing CO2-containing gas by adsorbing it to an adsorbent at 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 is also possible to use PSA or the like to form the carbon dioxide separation section and the water separation section into a single separation section.

[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.

(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 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.

(3) In the above embodiment, the water separation section 40 is provided downstream of the hydrocarbon synthesis reaction section 30. However, 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.

(4) In the above embodiment, both H ₂ O and CO ₂ are supplied to the electrolysis reaction unit 10 for the electrolysis reaction. However, as shown in Fig. 10, a system in which only H ₂ O 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.

(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, but an alkaline electrolysis cell, a polymer membrane electrolysis cell, or the like may also be used as the electrolysis cell 1.

(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 this metal support 4 acts as a separator for separating the produced hydrocarbons from oxygen.

(7) In the above embodiment, the hydrocarbon production system 100 is configured to include a reverse water gas shift reactor 20. However, as shown in FIG. 14, it is 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 of carbon monoxide and carbon dioxide upstream of the hydrocarbon synthesis reactor 30.

(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, chemical raw materials can also be synthesized from hydrogen, carbon monoxide, etc., introduced into the hydrocarbon synthesis reaction section 30.

1 Electrolytic 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 Electrolysis 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 Catalytically Active Components (Metal Components)
cb2 Metal oxide carrier (carrier)

Claims (15)

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 . 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. The hydrocarbon production system according to claim 1, wherein the carbon monoxide adsorption amount of the hydrocarbon synthesis catalyst is 0.4 ml/g or more . The hydrocarbon production system according to any one of claims 1 to 3, further comprising a reverse water gas shift catalytic reaction section . The hydrocarbon production system according to any one of claims 1 to 4 , further comprising a water separation section at least in one of an upstream stage and a downstream stage of the catalytic reaction section . The hydrocarbon production system according to claim 5 , further comprising a recycle line for recycling the water separated in the water separation section . The hydrocarbon production system according to any one of claims 1 to 6 , further comprising a carbon dioxide separation section provided downstream of the catalytic reaction section . The hydrocarbon production system according to claim 7 , further comprising a recycle line for recycling the carbon dioxide separated in the carbon dioxide separation section . The hydrocarbon production system according to any one of claims 1 to 8 , further comprising a heavy hydrocarbon separation section provided downstream of the catalytic reaction section . 10. The hydrocarbon production system according to claim 1 , wherein the electrolysis reaction section has an electrolysis cell in which at least an electrode layer, an electrolyte layer and a counter electrode layer are formed on a support . 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/supporting ruthenium on a metal oxide support; and an impregnation/supporting step of impregnating/supporting at least one of molybdenum and vanadium in addition to the ruthenium, and the impregnated /supported catalyst is disposed in the catalytic reaction section according to any one of claims 1 to 11. A method for producing a hydrocarbon production system, comprising the steps of: an impregnation/supporting step of impregnating a metal oxide support with ruthenium; and an impregnation/supporting step of impregnating a metal oxide support with at least one of molybdenum and vanadium in addition to the ruthenium; and disposing an impregnated/supported catalyst in the catalytic reaction section according to claim 12 . A method for operating a hydrocarbon production system according to any one of claims 1 to 12, comprising operating the catalytic reaction section after performing a reduction pretreatment . A method for operating a hydrocarbon production system according to any one of claims 4 to 12, comprising the step of operating a reverse water gas shift catalytic reaction section constituting the catalytic reaction section after carrying out a reduction pretreatment .

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