Electrochemical reaction cell, electrochemical reaction cell stack, hot module, alkene production device, alkene production system, and method for producing alkene

Abstract

This electrochemical reaction cell includes: an electrolyte in which proton conductivity is promoted by humidification; a first electrode layer provided on one surface of the electrolyte and containing a catalyst that promotes an oxidation coupling reaction for converting an alkane into an alkene; and a second electrode layer provided on the other surface of the electrolyte. When an alkane-containing gas and a humidifying gas are supplied, in the first electrode layer, the alkane can be converted into the alkene using an oxygen source generated from water vapor contained in the humidifying gas.

Description

Electrochemical reaction cell, electrochemical reaction cell stack, hot module, alkene production apparatus, alkene production system, and method for producing alkenes.

[0001] This invention relates to the production of alkenes.

[0002] Conventionally, a method for producing ethylene is known in which methane is converted to ethylene by methane oxidation coupling, which is an electrochemical reaction. For example, Patent Document 1 discloses an ethylene production apparatus comprising a ceramic film having at least one of oxide ion conductivity and proton conductivity, and a first catalyst layer provided on one surface of the ceramic film and equipped with a catalyst that promotes the methane oxidation coupling reaction.

[0003] International Publication No. 2022 / 270404

[0004] There are two methods for producing ethylene using electrochemical reactions: one using a methane oxidation coupling reaction and the other using a methane non-oxidation coupling reaction. While the former reaction has relatively high reaction efficiency, lower reaction temperatures were desired. On the other hand, the latter reaction yields pure hydrogen as a byproduct of ethylene production, but its reaction efficiency is low and the reaction temperature is relatively high. Therefore, a technology capable of efficiently producing ethylene and pure hydrogen under low-temperature conditions was desired. However, the prior art described in Patent Document 1 did not adequately consider the efficient production of ethylene and pure hydrogen under low-temperature conditions.

[0005] The present invention has been made to solve at least some of the problems described above, and aims to provide a technology that can efficiently produce alkenes and pure hydrogen under low-temperature conditions.

[0006] The present invention has been made to solve at least some of the above-mentioned problems and can be realized in the following forms.

[0007] (1) According to one embodiment of the present invention, an electrochemical reaction cell is provided. This electrochemical reaction cell comprises an electrolyte whose proton conductivity is promoted by humidification, a first electrode layer provided on one surface of the electrolyte and containing a catalyst that promotes an oxidative coupling reaction that converts alkanes to alkenes, and a second electrode layer provided on the other surface of the electrolyte, wherein when an alkane-containing gas and a humidifying gas are supplied, the first electrode layer can convert alkanes to alkenes using an oxygen source generated from water vapor contained in the humidifying gas.

[0008] In this configuration, when an alkane-containing gas and a humidifying gas are supplied to the space on the side where the first electrode layer is located, the electrolyte is humidified by water vapor, and in the first electrode layer, the alkanes are converted to alkenes using an oxygen source generated from the water vapor contained in the humidifying gas. Furthermore, protons generated from the water vapor (protons generated by the reaction of formula (1) described later) move to the side of the second electrode layer via the electrolyte whose proton conductivity is enhanced by humidification, and are then converted to hydrogen. With this configuration, by using an electrolyte whose proton conductivity is enhanced by humidification, ion conduction is possible at low temperatures compared to when an electrolyte with oxide ion conductivity is used. Therefore, with this configuration, alkenes can be efficiently produced and pure hydrogen can be produced simultaneously at low temperatures.

[0009] (2) In the electrochemical reaction cell of the above embodiment, the oxidation coupling reaction promoted by the catalyst may be a methane oxidation coupling reaction that converts methane to ethylene. With this configuration, pure hydrogen can be produced while efficiently generating ethylene.

[0010] Furthermore, the present invention can be realized in various forms, for example, as an electrochemical reaction cell stack in which a plurality of electrochemical reaction cells are stacked; a hot module equipped with an electrochemical reaction cell stack; an alkene production apparatus equipped with a hot module; an alkene production system equipped with these apparatuses; a method for producing alkenes using any of these apparatuses; a computer program for executing these apparatuses; a server device for distributing this computer program; a non-temporary storage medium storing the computer program, and so on.

[0011] This is an explanatory diagram showing the schematic configuration of an ethylene production apparatus according to the first embodiment of the present invention. This is an explanatory diagram showing the schematic configuration of an ethylene production apparatus according to the second embodiment of the present invention.

[0012] <First Embodiment> Figure 1 is an explanatory diagram showing the schematic configuration of an ethylene production apparatus 1 as a first embodiment of the present invention. The ethylene production apparatus 1 is an apparatus that produces ethylene and pure hydrogen using water vapor and methane. The ethylene production apparatus 1 includes a ceramic membrane 5, a first electrode layer 10, a second electrode layer 20, a humidifying gas supply unit 30, an external circuit 42, and a load unit 44. The ceramic membrane 5, the first electrode layer 10, and the second electrode layer 20 of the ethylene production apparatus 1 are collectively called the electrochemical reaction cell CL. The ethylene production apparatus 1 further includes a housing (not shown) having two spaces inside that are separated by a partition wall. The electrochemical reaction cell CL constitutes at least a part of the above-mentioned partition wall. In the ethylene production apparatus 1, the space on the side where the first electrode layer 10 is provided among the two spaces separated by the partition wall including the electrochemical reaction cell CL is called the first space S1.

[0013] The ceramic film 5 is a film-like electrolyte composed of ceramics having proton conductivity. The proton conductivity of the ceramic film 5 is enhanced by humidification. The ceramics constituting the ceramic film 5 only need to have the property of having their proton conductivity enhanced by humidification, and various mixtures or composite oxides of oxides known conventionally can be used. In this embodiment, the ceramics constituting the ceramic film 5 are Ba ｉ Scｊ M1 ｋ M2 ｌ O ３－δ (M1: W and / or Mo, M2: Cu and / or Ni; i, j, k, l are each coefficients). Further, as the ceramics constituting the ceramic membrane 5, for example, BaScO other than the present embodiment ３－δ -based, BaZrO ３－δ -based, BaCeO ３－δ -based, Ba(Zr, Ce)O ３－δ -based, BaSnO ３－δ -based, LaMO ３－δ (M = Sc, Y, Yb)-based, SrZrO ３－δ -based, or SrCeO ３－δ -based perovskite-type composite oxides may also be used.

[0014] The first electrode layer 10 is provided on one surface of the ceramic membrane 5, and contains a catalyst that promotes the methane oxidative coupling reaction for converting methane into ethylene. The catalyst contained in the first electrode layer 10 only needs to be a catalyst that promotes the methane oxidative coupling reaction, and various conventionally known mixtures of oxides or composite oxides can be used. In the present embodiment, the first electrode layer 10 contains, as a catalyst that promotes the methane oxidative coupling reaction, BaZr γ Sc １－γ O ３－δ (0 < γ < 1). Further, the first electrode layer 10 may also contain, as a catalyst that promotes the methane oxidative coupling reaction, for example, Li / MgO, Li ２ CaSiO ４ , M ２ ZrO ３ (M = Li, Na), Mn-Na ２ WO ４ / SiO ２ , Sr / La ２ O ３may be contained. The first electrode layer 10 may be formed using a supported catalyst in which the catalyst is supported on a porous powder used as a carrier. Examples of suitable methods for supporting the catalyst on a carrier include vapor phase methods represented by sputtering, and liquid phase methods represented by the impregnation method and spin coating. When a liquid phase method is used, baking treatment is preferably performed at about 500°C to 900°C to volatilize organic components in the slurry.

[0015] Further, the first electrode layer 10 contains a catalyst that promotes the decomposition reaction of water vapor. In the present embodiment, the first electrode layer 10 contains La as a catalyst that promotes the decomposition reaction of water vapor ０．６ Sr ０．４ Co ０．２ Fe ０．８ O ３－δ is contained. Further, as a catalyst for promoting the decomposition reaction of water vapor, the first electrode layer 10 may contain, for example, PrNi ｘ Co １－ｘ O ３－δ (0 < x < 1) or La ｘ Sr １－ｘ MnO ３－δ (0 < x < 1), BaCo ｙ Zr ｚ Sc １－ｙ－ｚ O ３－δ (y > 0, z > 0, y + z < 1) may be contained.

[0016] The second electrode layer 20 is provided on the other surface of the ceramic membrane 5. The second electrode layer 20 contains a catalyst that promotes the reaction of converting protons into hydrogen. In the present embodiment, the second electrode layer 20 contains cermet, which is a composite (sintered body) of the ceramic constituting the ceramic membrane 5 and Ni, as a catalyst that promotes the reaction of converting protons into hydrogen.

[0017] The humidified gas supply unit 30 is a device that supplies methane-containing gas and humidified gas to the first electrode layer 10 (first space S1). In the present embodiment, the humidified gas supply unit 30 supplies a methane-containing humidified gas obtained by mixing a methane-containing gas and a humidified gas. The methane-containing humidified gas may be produced, for example, by humidifying natural gas containing methane as a main component.

[0018] The external circuit 42 is a circuit that moves electrons from the first electrode layer 10 to the second electrode layer 20. More specifically, when methane-containing humidifying gas is supplied to the first space S1 from the humidifying gas supply unit 30, the external circuit 42 uses an external power source to create a potential difference between the first electrode layer 10 and the second electrode layer 20, thereby moving electrons from the first electrode layer 10 to the second electrode layer 20. The load unit 44 is provided within the external circuit 42 and is a device that extracts power to be supplied to the external circuit 42.

[0019] When methane-containing humidifying gas is supplied to the first space S1 from the humidifying gas supply unit 30, the ceramic film 5 is humidified by water vapor. At the same time, a reaction proceeds on the first electrode layer 10, which contains a catalyst that promotes the decomposition reaction of water (water vapor), in which an oxygen source is generated from the water vapor. As an example of the reaction in which an oxygen source is generated from water vapor, the decomposition reaction of water (water vapor) and the reaction in which the oxygen decomposed from water (water vapor) is converted into oxide ions proceed, as shown in the following equations (1) and (2). ２ O → O ２ +4H ＋ +4e － … (1) O ２ +4e － → 2O ２－ ... (2)

[0020] The first electrode layer 10 contains a catalyst that promotes the decomposition reaction of water vapor, as well as a catalyst that promotes the methane oxidation coupling reaction that converts methane to ethylene. Therefore, when methane-containing humidified gas is supplied to the first space S1, a reaction (methane oxidation coupling reaction) in which methane is converted to ethylene using the oxide ions generated in equation (2) above proceeds on the first electrode layer 10, as shown in equation (3) below. ４ +2O ２－ → C ２ H ４ +2H ２ O+4e －… (3) Thus, in the first electrode layer 10, methane can be converted to ethylene using oxide ions generated from water vapor contained in the methane-containing humidifying gas. Note that the right side of equation (3) above is water (H), which has a large negative standard Gibbs free energy of formation. ２ Because it contains O, the reaction Gibbs free energy becomes negatively large, and therefore, equation (3) proceeds more readily than the reaction in which ethylene is produced without the production of water in the absence of an oxygen source.

[0021] Combining equations (1) to (3) above, the reaction that occurs on the first electrode layer 10 when methane-containing humidifying gas is supplied to the first space S1 is expressed as shown in equation (4) below. 2CH ４ → C ２ H ４ +4H ＋ +4e － … (4)

[0022] When methane-containing humidifying gas is supplied to the first space S1 from the humidifying gas supply unit 30, the ceramic film 5 is humidified by the water vapor contained in the methane-containing humidifying gas, as described above. Therefore, on the side of the first electrode layer 10, protons produced as a by-product during the conversion of methane to ethylene (see equation (1) or equation (4)) move to the side of the second electrode layer 20 via the ceramic film 5, whose proton conductivity is enhanced by humidification, and are then converted to hydrogen as shown in the following equation (5): 4H ＋ +4e － → 2H ２ … (5)

[0023] As shown in equations (4) and (5) above, in the ethylene production apparatus 1, when methane-containing humidified gas is supplied from the humidified gas supply unit 30 to the first space S1, ethylene is produced in the first electrode layer 10 and pure hydrogen is produced in the second electrode layer 20. Although equations (2) and (3) illustrate the case in which oxide ions are produced as reaction intermediates, the oxygen source generated from water vapor is not necessarily limited to this. Specifically, the oxygen source generated from water vapor may be reactive oxygen species such as hydroxyl radicals or singlet oxygen. Even in that case, water is produced as a reaction product with methane, so the methane oxidation coupling reaction proceeds easily.

[0024] According to the electrochemical reaction cell CL of the ethylene production apparatus 1 of the first embodiment described above, when methane-containing humidified gas is supplied to the first space S1, the ceramic film 5 is humidified with water vapor, and in the first electrode layer 10, methane is converted to ethylene using an oxygen source generated from the water vapor contained in the methane-containing humidified gas, such as oxide ions (see formulas (1) and (2)) (see formula (3)). In addition, protons generated from water vapor (see formula (1) or formula (4)) move to the second electrode layer 20 side via the ceramic film 5, whose proton conductivity has been enhanced by humidification, and are then converted to hydrogen (see formula (5)).

[0025] Compared to the proton conductivity of the humidified ceramic film 5 under temperature conditions of 400°C to 600°C, the oxide ion conductivity of the comparative example ceramic film, which is composed of ceramics having oxide ion conductivity, is lower under the same temperature conditions. In other words, in the electrochemical reaction cell CL of the first embodiment, by using a ceramic film 5 whose proton conductivity is promoted by humidification, ion conduction is possible under lower temperature conditions compared to the case where the comparative example ceramic film having oxide ion conductivity is used. Therefore, according to the electrochemical reaction cell CL of the first embodiment, ethylene can be efficiently produced while simultaneously producing pure hydrogen under low temperature conditions. Furthermore, it is generally known that proton-conducting ceramics are prone to hole conduction in high-temperature oxidizing atmospheres (>600°C), which causes electronic leakage and reduces the proton transport rate. According to the electrochemical reaction cell CL of the first embodiment, since protons are conducted under low temperature conditions, it is also possible to suppress the occurrence of electronic leakage in the ceramic film 5.

[0026] <Second Embodiment> Figure 2 is an explanatory diagram showing the schematic configuration of an ethylene production apparatus 1a as a second embodiment of the present invention. Similar to the ethylene production apparatus 1 of the first embodiment, the ethylene production apparatus 1a is an apparatus that produces ethylene and pure hydrogen using steam and methane. The ethylene production apparatus 1a is equipped with a hot module 51.

[0027] The hot module 51 comprises an electrochemical reaction cell stack ST, a humidifying gas supply unit 30, a heater 52, and an insulating container 53. To reduce heat dissipation, the hot module 51 houses the electrochemical reaction cell stack ST and the heater 52 inside the insulating container 53. The insulating container 53 may also house the humidifying gas supply unit 30. Examples of materials forming the insulating container 53 include heat-resistant fibers such as ceramic wool, refractory ceramic fiber (RCF), and biosoluble fiber (AES). Such heat-resistant fibers are suitable for filling the gaps between the electrochemical reaction cell stack ST, the humidifying gas supply unit 30, and the heater 52.

[0028] The electrochemical reaction cell stack ST is constructed by stacking multiple electrochemical reaction cells CL (see Figure 1). Inside the electrochemical reaction cell stack ST, there is a manifold for supplying methane-containing humidified gas from outside the electrochemical reaction cell stack ST to each of the electrochemical reaction cells CL, and a manifold for releasing ethylene and hydrogen from each of the electrochemical reaction cells CL to the outside of the electrochemical reaction cell stack ST.

[0029] In the ethylene production apparatus 1a, the humidifying gas supply unit 30 supplies methane-containing humidifying gas to the electrochemical reaction cell stack ST. Specifically, the methane-containing humidifying gas delivered from the humidifying gas supply unit 30 is heated by the heater 52, which is a heating unit, and then supplied to the electrochemical reaction cell stack ST.

[0030] In the electrochemical reaction cell stack ST of the ethylene production apparatus 1a of the second embodiment described above, just like in the first embodiment, ethylene can be efficiently produced under low temperature conditions while simultaneously producing pure hydrogen. Furthermore, since the ethylene production apparatus 1a of the second embodiment is equipped with a heater 52 and an insulated container 53, ethylene and pure hydrogen can be produced under more favorably controlled temperature conditions.

[0031] <Modifications of this Embodiment> The present invention is not limited to the above-described embodiments, and can be implemented in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0032] In the above embodiment, the first electrode layer 10 contained a catalyst that promotes the methane oxidation coupling reaction that converts methane to ethylene, but is not limited to this. The first electrode layer 10 may also contain a catalyst that promotes the oxidation coupling reaction that converts alkanes to alkenes. That is, the electrochemical reaction cell CL is not limited to ethylene and may be a cell for producing alkenes. For example, the first electrode layer 10 contains a catalyst that promotes the oxidation coupling reaction that converts ethane to propylene, and the electrochemical reaction cell CL may be a cell for producing propylene from ethane and also producing pure hydrogen.

[0033] In the above embodiment, the humidifying gas supply unit 30 was a device that supplied methane-containing humidified gas, which is a mixture of methane-containing gas and humidifying gas, but it is not limited to this. The humidifying gas supply unit 30 may also be capable of supplying methane-containing gas and humidifying gas separately. In such a configuration, when producing ethylene and pure hydrogen in the electrochemical reaction cell CL, the humidifying gas is supplied to the first electrode layer 10, and then the methane-containing gas is supplied to the first electrode layer 10.

[0034] In the above embodiment, examples of a configuration for producing ethylene and pure hydrogen included an electrochemical reaction cell CL, an ethylene production apparatus 1, an electrochemical reaction cell stack ST, a hot module 51, and an ethylene production apparatus 1a, but the invention is not limited thereto. A configuration for producing ethylene and pure hydrogen may also include an ethylene production system comprising any one of the following: an electrochemical reaction cell CL, an electrochemical reaction cell stack ST, and a hot module 51.

[0035] In the above embodiment, the ethylene production apparatus 1 included an electrochemical reaction cell CL and a humidifying gas supply unit 30, but is not limited to this. For example, the ethylene production apparatus may include an electrochemical reaction cell stack ST and a humidifying gas supply unit 30.

[0036] In the above embodiment, the hot module 51 included an electrochemical reaction cell stack ST, a humidifying gas supply unit 30, a heater 52, and an insulated container 53, but is not limited to this. For example, the hot module may include an electrochemical reaction cell CL, a humidifying gas supply unit 30, a heater 52, and an insulated container 53. An alkene production apparatus may be configured with such a hot module. Of course, an ethylene production system may also be configured with such a hot module.

[0037] The embodiments of this specification have been described above based on the embodiments and modifications described above. The embodiments described above are for the purpose of facilitating understanding of this specification and do not limit it. This specification may be modified and improved without departing from its spirit and the scope of the claims, and equivalents thereof are included in this specification. Furthermore, any technical features that are not described as essential in this specification may be deleted as appropriate.

[0038] The present invention can also be realized in the following forms: [Example 1] An electrochemical reaction cell comprising: an electrolyte whose proton conductivity is promoted by humidification; a first electrode layer provided on one surface of the electrolyte and containing a catalyst that promotes an oxidation coupling reaction that converts alkanes to alkenes; and a second electrode layer provided on the other surface of the electrolyte, wherein when an alkane-containing gas and a humidifying gas are supplied, the first electrode layer is capable of converting alkanes to alkenes using an oxygen source generated from water vapor contained in the humidifying gas. [Example 2] An electrochemical reaction cell according to Example 1, wherein the oxidation coupling reaction promoted by the catalyst is a methane oxidation coupling that converts methane to ethylene. [Example 3] An electrochemical reaction cell stack characterized in that a plurality of electrochemical reaction cells according to Example 1 or Example 2 are stacked. [Application Example 4] A hot module comprising: an electrochemical reaction cell stack as described in Application Example 3; a humidifying gas supply unit that supplies the alkane-containing gas and the humidifying gas to the electrochemical reaction cell stack; a heating unit that raises the temperature of the alkane-containing gas and the humidifying gas supplied to the electrochemical reaction cell stack; and an insulated container that houses the electrochemical reaction cell stack and the heating unit inside. [Application Example 5] An alkene manufacturing apparatus comprising the hot module as described in Application Example 4. [Application Example 6] An alkene manufacturing system comprising any one of the following: an electrochemical reaction cell as described in Application Example 1 or Application Example 2; an electrochemical reaction cell stack as described in Application Example 3; and a hot module as described in Application Example 4. [Application Example 7] A method for manufacturing an alkene using any one of the following: an electrochemical reaction cell as described in Application Example 1 or Application Example 2; an electrochemical reaction cell stack as described in Application Example 3; and a hot module as described in Application Example 4.

[0039] 1...Ethylene production apparatus 1a...Ethylene production apparatus 5...Ceramic film 10...First electrode layer 20...Second electrode layer 30...Humidifying gas supply unit 42...External circuit 44...Load unit 51...Hot module 52...Heater 53...Insulated container CL...Electrochemical reaction cell ST...Electrochemical reaction cell stack

Claims

1. An electrochemical reaction cell comprising: an electrolyte whose proton conductivity is promoted by humidification; a first electrode layer provided on one surface of the electrolyte and containing a catalyst that promotes an oxidative coupling reaction that converts alkanes to alkenes; and a second electrode layer provided on the other surface of the electrolyte, wherein when an alkane-containing gas and a humidifying gas are supplied, the first electrode layer is capable of converting alkanes to alkenes using an oxygen source generated from water vapor contained in the humidifying gas.

2. An electrochemical reaction cell according to claim 1, characterized in that the oxidation coupling reaction promoted by the catalyst is a methane oxidation coupling reaction that converts methane to ethylene.

3. An electrochemical reaction cell stack characterized by having a plurality of electrochemical reaction cells as described in claim 1 stacked on top of each other.

4. A hot module comprising: an electrochemical reaction cell stack according to claim 3; a humidifying gas supply unit for supplying the alkane-containing gas and the humidifying gas to the electrochemical reaction cell stack; a heating unit for heating the alkane-containing gas and the humidifying gas supplied to the electrochemical reaction cell stack; and an insulated container housing the electrochemical reaction cell stack and the heating unit.

5. An alkene manufacturing apparatus characterized by comprising the hot module described in claim 4.

6. An alkene production system comprising any one of the following: an electrochemical reaction cell according to claim 1 or claim 2, an electrochemical reaction cell stack according to claim 3, and a hot module according to claim 4.

7. A method for producing an alkene using any one of the following: the electrochemical reaction cell described in claim 1 or claim 2, the electrochemical reaction cell stack described in claim 3, and the hot module described in claim 4.

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