Sheet-type structure for in-situ catalytic synthesis of methane by coupling solid oxide electrolytic tank and application of sheet-type structure

Abstract

The invention discloses a sheet type structure for in-situ catalytic synthesis of methane by coupling a solid oxide electrolytic tank and application of the sheet type structure. The sheet-type structure is composed of a conventional sheet-type solid oxide electrolytic tank and a carbon dioxide hydrogenation methanation catalyst; the sheet-type structure is an integrated structure formed by filling a methanation catalyst into a connector raw material channel on the cathode side of the sheet-type solid oxide electrolytic cell. The sheet type structure for in-situ catalytic synthesis of methane through the coupled solid oxide electrolytic tank can realize coupling of electrolytic reaction and methanation, a mixed gas containing carbon dioxide, water vapor, hydrogen and the like is converted into a gas containing high-concentration methane, and high-level methane yield exceeding thermodynamic equilibrium limitation is realized with low energy consumption; and the electrolytic reaction and the hydrogenation methanation reaction are carried out in situ on the cathode side of the electrolytic tank, and a low-temperature methanation catalytic reactor does not need to be additionally arranged.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic hydrogen production and carbon dioxide methanation, and relates to a solid oxide electrolytic cell, and more specifically, to a sheet structure coupled to a solid oxide electrolytic cell for in-situ catalytic synthesis of methane, and a method for in-situ catalytic synthesis of methane based on the sheet structure. Background Art

[0002] The technical measures to reduce carbon emissions mainly include "carbon capture and utilization" (CCU) and "carbon capture and storage" (CCS). The former converts the captured carbon dioxide into high-value-added chemicals or fuels, while the latter permanently stores carbon dioxide in safe places such as underground. Among them, the catalytic conversion of carbon dioxide is a more attractive and important way to reduce carbon emissions. The captured carbon dioxide can be converted into many high-value-added chemical products such as methanol, formaldehyde, formic acid, methane, etc. through catalytic reactions. Among them, carbon dioxide hydrogenation and methanation is considered to be one of the effective ways to utilize carbon dioxide resources due to its favorable reaction conditions and thermodynamic characteristics. Using green renewable electricity such as wind power, hydropower, and photovoltaics, hydrogen is produced by electrolyzing water, and the hydrogen produced is hydrogenated with carbon dioxide to synthesize methane. This technical route is called PtM (Power to methane, PtM). PtM technology has gradually become a research hotspot in various countries in recent years.

[0003] Compared with alkaline electrolyzers and proton exchange membrane electrolyzers, solid oxide electrolyzers (SOECs) have lower operating voltages and higher working efficiency, and the efficiency of hydrogen production by electrolysis can reach more than 90%. Therefore, the technology of synthesizing methane by co-electrolyzing water and carbon dioxide in solid oxide electrolyzers is expected to achieve more efficient conversion between electricity. Solid oxide electrolyzers mainly have two structural forms: tubular and sheet. The sheet structure, also known as a flat-plate solid oxide electrolyzer, has a basic structural unit including a cathode, an anode, an electrolyte, and a connector between the cathode and the anode, wherein the connector includes a cavity structure, forming a raw gas channel with the cathode side, and an air channel with the anode side. The flat-plate structure has the advantages of simple preparation process, short current collection process, and high power density. For example, CN115613063A discloses a flat-plate solid oxide electrolytic cell stack, in which the repeating units include a plurality of stacked battery pack units, each of which is provided with a battery sealing gasket, a battery, a connecting plate, and a flow channel plate which are connected in sequence; the connecting plate adopts a hollow outer frame structure, and the flow channel plate is provided with a matrix-type concave-convex structure of the flow channel, thereby forming a fuel gas cavity and an air cavity.

[0004] However, the solid oxide electrolysis cell generally uses a temperature range of 500-1000°C, while the exothermic methanation reaction generally occurs below 450°C due to thermodynamic equilibrium constraints, that is, there is a temperature mismatch between the two. Therefore, the "two-step method" is generally used to achieve the combination of water electrolysis and methanation reaction. That is, the electrolysis cell electrolyzes water at high temperature to produce hydrogen, and then hydrogen and carbon dioxide are synthesized into methane in the low-temperature reactor of the second stage. For example, Sichuan University uses a two-stage reaction process to combine the high-temperature solid oxide electrolysis cell water electrolysis hydrogen production and biogas methanation process (Chemical Research and Application, 2022, 34(8): 1819). Similar methods are also disclosed in many patent documents (CN103756741A, CN 114182268A, CN 113818035 A).

[0005] In recent years, in order to improve the coupling of solid oxide electrolysis cells and carbon dioxide methanation reactions, some studies have attempted to construct temperature gradient coupled reactors ("quasi-one-step method") based on the traditional two-step method. That is, a temperature gradient is constructed in the reaction field, and the reaction of water electrolysis to produce hydrogen is carried out at above 650°C, while a low-temperature carbon dioxide methanation reaction field is constructed in the later stage by heat exchange and other technologies. For example, Xia Changrong et al. placed the upstream part of the tubular solid oxide electrolysis cell in a high-temperature electric furnace at 800°C and the downstream part in a room temperature environment at the furnace mouth, thereby creating a gradient temperature field for the tubular electrolysis cell, and passed 12% CO2+ 17% H2O + 71% H2 at 1.5V, and obtained 11.4% CH4 in the dry outlet product (Energy & Environmental Science, 2014, 7: 4018-4022). CN105220172A discloses a similar quasi-one-step method and tubular structure reactor.

[0006] On the other hand, the carbon dioxide methanation process is an exothermic reaction, while the water electrolysis process is an endothermic reaction. If the carbon dioxide methanation and water electrolysis are coupled in the same space to achieve endothermic coupling (that is, the "one-step" in-situ synthesis of methane), it is not only conducive to reducing the operating energy consumption of the solid oxide electrolysis cell, but also can effectively avoid the thermodynamic limitation of the reaction heat of methanation on methane synthesis. In the case of the two-step method, due to the heat loss during the reaction process, the energy conversion efficiency is generally only about 55-60%. If the heat generated in the methanation reaction is effectively used for the endothermic reaction of water electrolysis, it has the advantages of reducing heat loss and improving energy conversion efficiency. Moreover, in addition to the coupling of energy flow, the two processes also have a high degree of coupling in terms of material flow. In the case of in-situ coupling of carbon dioxide methanation and water electrolysis in a solid oxide electrolysis cell, the electrolysis cell can further electrolyze the product water of carbon dioxide methanation to produce hydrogen, breaking the thermodynamic equilibrium limitation of the methanation reaction, promoting the reaction to move to the right, and realizing the super-thermodynamic equilibrium of the material flow in the macroscopic process. Summary of the invention

[0007] The purpose of the present invention is to provide a chip structure coupled with a solid oxide electrolytic cell for in-situ catalytic synthesis of methane. The technical problem to be solved is to overcome the temperature mismatch between SOEC and methanation and exceed the limit of thermodynamic equilibrium on the methanation reaction. Methanation is coupled with SOEC, and the electrolysis of water vapor and carbon dioxide and the hydrogenation methanation reaction of carbon dioxide and carbon monoxide occur simultaneously in situ in the chip structure system, so as to achieve a high level of methane yield beyond the limit of thermodynamic equilibrium with low energy consumption.

[0008] Another object of the present invention is to provide an application of the sheet structure for in-situ catalytic synthesis of methane in a coupled solid oxide electrolytic cell.

[0009] The present invention solves the technical problem by adopting the following technical solution: The present invention discloses a chip structure for in-situ catalytic synthesis of methane coupled with a solid oxide electrolytic cell, characterized in that: the chip structure comprises a chip solid oxide electrolytic cell and a carbon dioxide hydrogenation methanation catalyst; the methanation catalyst is loaded in a connector raw material channel on the cathode side of the chip solid oxide electrolytic cell to form an integrated structure.

[0010] The solid oxide electrolytic cell adopts a conventional sheet-type solid oxide electrolytic cell, including a battery repeating unit, wherein the battery repeating unit includes a cathode, an anode and an electrolyte, and a cathode-anode connector, wherein the connector includes a cavity structure, forming a raw material channel between the cathode side and an air channel between the anode side.

[0011] The methanation catalyst is preferably a pelletized catalyst, and is uniformly loaded into each raw material channel on the cathode side of the connector in the sheet-type solid oxide electrolytic cell in a random loading mode.

[0012] The diameter of the methanation catalyst beads is 0.1-1.5 mm, preferably 0.5-1.0 mm. The methanation catalyst beads are loaded into the connector raw material channel on the cathode side of the sheet-type solid oxide electrolyzer, preferably in the rear portion of the channel where the catalyst accounts for 70%-100% and the inert beads of the same particle size in the front portion of the channel account for 0%-30%.

[0013] The methanation catalyst is preferably a composite metal oxide catalyst, wherein the active component is selected from precious metals such as Pt, Pd, Ru, etc., or from transition metals such as Fe, Ni, Co, etc., preferably Pt, Pd, Ru, Ni; the carrier is a nickel-aluminum composite metal oxide; the nickel-aluminum composite metal oxide includes nickel oxide and nickel aluminum spinel, wherein the proportion of nickel in the form of nickel oxide to the total amount of nickel element in the carrier is not higher than 10%, and the nickel aluminum spinel includes a chemically equivalent spinel structure NiAl2O4 and a non-chemically equivalent spinel-like structure NixAlyOz, x<1, y>2, z>3.

[0014] When the active component of the methanation catalyst is a precious metal such as Pt, Pd or Ru, the loading amount thereof is 0.05-5.0 wt%, preferably 0.2-2.0 wt%; when the active component is a transition metal such as Fe, Ni or Co, the loading amount thereof is 0.5-50 wt%, preferably 2-30 wt%.

[0015] The methanation catalyst and its preparation can be prepared by referring to the method disclosed in CN 118002133 A.

[0016] In a specific embodiment, a method is adopted, wherein the methanation catalyst is prepared as follows: (1) Alumina beads are immersed in a nickel precursor solution, and after continuous stirring, the solution is filtered, dried and calcined at 600-900°C to obtain a nickel-aluminum composite metal oxide carrier; (2) The nickel-aluminum composite metal oxide carrier beads obtained in the above step (1) and a precursor solution of precious metals such as Pt, Pd, Ru, or a precursor solution of transition metals such as Fe, Ni, Co, etc. are added to a solvent and continuously stirred; (3) The impregnated nickel-aluminum composite metal oxide carrier beads are filtered, dried and then calcined; (4) The calcined catalyst is subjected to a reduction treatment.

[0017] In step (1) of preparing the methanation catalyst, the nickel precursor includes but is not limited to one or more of nickel nitrate, nickel acetate, nickel phosphate, nickel hypophosphite, nickel oxalate, nickel hydroxide or nickel oxide; in step (1), the element molar ratio of nickel to aluminum in the nickel precursor and aluminum oxide is in the range of 0.05-1:1.

[0018] In the step (1) of preparing the methanation catalyst, the impregnation temperature is 25-100° C. and the impregnation time is 0.5-48 hours.

[0019] In the step (1) of preparing the methanation catalyst, the calcination temperature is 600-900° C., preferably 700-800° C.; the calcination time is preferably 1-5 hours.

[0020] In the step (2) of preparing the methanation catalyst, the precious metal precursor includes but is not limited to one or more of Pt(NH3)2(NO2)2, Pt(NO3)2, H2PtCl6, PdCl2, Pd(NO3)2, Pd(OAc)2, Ru(NO3)2, and RuCl2; the transition metal precursor includes but is not limited to one or more of FeCl2, FeCl3, Fe2O3, Fe3O4, Fe(NO3)2, NiCl2, Ni(NO3)2, NiO, CoO, CoCl2, and CoC2O4.

[0021] Based on the sheet structure, the present invention also provides a method for co-electrolysis of water and carbon dioxide for methanogenesis, which directly converts a mixed gas of carbon dioxide, water vapor, hydrogen, etc. into a gas containing a high concentration of methane. The method adopts the sheet structure for in-situ catalytic synthesis of methane by a coupled solid oxide electrolytic cell as described above, applies voltage to the sheet solid oxide electrolytic cell, and introduces a raw material gas containing carbon dioxide, water and / or hydrogen into the raw material channel of the connector, and water vapor and carbon dioxide undergo electrolysis reaction at the cathode of the sheet solid oxide electrolytic cell to generate hydrogen and carbon monoxide; the generated hydrogen, carbon monoxide and carbon dioxide undergo in-situ catalytic methanogenesis reaction on a methanogenic catalyst in the channel of the connector to generate methane and water.

[0022] Furthermore, in the method, the reaction temperature in the sheet structure is 500-650°C, preferably 500-600°C.

[0023] According to the method of the present invention, in the sheet structure for in-situ catalytic synthesis of methane in the coupled solid oxide electrolytic cell, water vapor in the raw material, water vapor generated by the methanation reaction of carbon dioxide, and part of the carbon dioxide undergo electrolysis reaction in the cathode of the solid oxide electrolytic cell to generate hydrogen and carbon monoxide; the generated hydrogen and carbon monoxide and the remaining carbon dioxide undergo in-situ methanation catalytic reaction on the methanation catalyst in the connector channel to generate gas containing high concentrations of methane and water; the generated water undergoes electrolysis reaction to generate hydrogen, promoting the right shift of the methanation reaction equilibrium. The sheet structure is used to realize the process of simultaneous in-situ electrolysis of water vapor and carbon dioxide and hydrogenation methanation reaction of carbon dioxide and carbon monoxide in the solid oxide electrolytic cell, promoting the coupling of the two processes in energy flow and material flow, and achieving a high level of methane yield beyond the thermodynamic equilibrium limit with low energy consumption.

[0024] With the sheet structure, the electrolysis reaction of water vapor and carbon dioxide and the hydrogenation and methanation reaction of carbon dioxide and carbon monoxide both occur in situ on the cathode side of the sheet solid oxide electrolysis cell, without the need for an additional low-temperature methanation catalytic reactor to carry out the hydrogenation and methanation reaction of carbon dioxide or carbon monoxide.

[0025] The sheet structure provided by the present invention can simultaneously carry out in-situ electrolysis of water vapor and carbon dioxide and hydrogenation and methanation of carbon dioxide and carbon monoxide on the cathode side of the sheet solid oxide electrolytic cell. The specific reactions involved are as follows: 2H2O(g) → 2H2(g)+ O2(g) 2CO2(g) → 2CO(g)+ O2(g) CO2(g)+H2(g) → CO(g)+H2O(g) CO (g)+3H2(g) → CH4(g)+H2O(g) CO2(g)+4H2(g) → CH4(g)+2H2O(g) 2CO(g)+2H2(g) → CH4(g)+ CO2(g).

[0026] The sheet structure of the present invention is formed by using an existing conventional solid oxide electrolytic cell and loading efficient methanogenic catalyst beads in the raw material channel of the connector on the cathode side thereof. Since the structure of the conventional solid oxide electrolytic cell is not changed, the preparation process of the sheet structure disclosed in the present invention is mature and convenient.

[0027] Compared with the prior art, the present invention has the following beneficial effects: The sheet structure of the present invention provides an electrolysis reaction field and a hydrogenation catalytic reaction field in the same space on the cathode side, so that the electrolysis reaction of water vapor and carbon dioxide and the hydrogenation methanation reaction of carbon dioxide and carbon monoxide occur synchronously in situ, providing sufficient possibilities for coupling the electrolysis process and the hydrogenation methanation process in terms of material flow (hydrogen as the product of the electrolysis reaction and water as the product of the methanation reaction) and energy flow (exothermic methanation reaction and endothermic electrolysis water reaction), thereby achieving a high level of methane yield beyond the thermodynamic equilibrium limit with low energy consumption. In addition, the use of small spherical catalysts effectively reduces the problem of catalyst layer peeling off that may be caused by coating technology, while ensuring low pressure loss in the raw material channel. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The schematic diagram of the sheet structure of the coupled solid oxide electrolytic cell for in-situ catalytic synthesis of methane of the present invention is shown, wherein the electrolytic cell is a conventional sheet solid oxide electrolytic cell, and the spherical methanogenic catalyst is uniformly loaded into the raw material channel on the cathode side of the connector in the sheet solid oxide electrolytic cell in a random loading mode. In the figure, 1-cathode, 2-electrolyte, 3-anode, 4-connector, 5-raw material channel, the raw material channel is loaded with spherical catalyst, and 6-air channel; Figure 2 for Figure 1Schematic diagram of a connector after a small spherical catalyst is loaded in a raw material channel in a sheet structure, in which 4-connector, 5-raw material channel, and a small spherical catalyst is loaded in the raw material channel; FIG3(a) is a photograph of a pelletized catalyst uniformly loaded in a random loading mode into a raw material channel of a cathode-side connector of a monolithic solid oxide electrolytic cell, and FIG3(b) is a photograph of a monolithic solid oxide electrolytic cell loaded with pelletized catalyst for testing; Figure 4 The thermal catalytic activity and outlet gas composition result diagram of the methanation reaction on the catalyst in Example 2 of the present invention (an independent thermal catalytic performance test not coupled with the solid oxide electrolytic cell); Figure 5 The figure is a comparison of the activity results under powered and non-powered conditions on a monolithic solid oxide electrolytic cell filled with 0.8 mm spherical catalyst. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further illustrated by specific examples and comparative examples below. However, it is necessary to point out that the following examples are only used to describe the content of the present invention and do not constitute a limitation on the protection scope of the present invention.

[0030] Example 1 A chip structure for in-situ catalytic synthesis of methane coupled to a solid oxide electrolytic cell, such as Figure 1 , Figure 2 As shown, it includes a sheet-type solid oxide electrolytic cell and a carbon dioxide hydrogenation methanation catalyst; the sheet-type solid oxide electrolytic cell adopts a conventional structure, wherein the battery repeating unit includes a cathode 1, an anode 3 and an electrolyte 2, and a cathode and anode connector 4, wherein the connector 4 includes a cavity structure, forming a raw material channel 5 between the cathode side and an air channel 6 between the anode side; in each raw material channel 5 on the cathode side of the connector in the sheet-type solid oxide electrolytic cell, a spherical methanation catalyst is uniformly filled in a random loading mode, and the diameter of the catalyst sphere is 0.1-1.5 mm, preferably 0.5-1.0 mm; one loading method is to fill the raw material channel 5 with the spherical methanation catalyst, or the loading area of ​​the catalyst sphere is 30%-100% of the middle and rear part of the channel, and the front area of ​​the channel is filled with inert spheres of the same particle size.

[0031] The sheet structure is an integrated structure formed by loading the methanogenic catalyst into the raw material channel of the connector on the cathode side of the conventional sheet solid oxide electrolyzer. A photograph of the cathode side of the connector of the solid oxide electrolyzer after loading the small spherical catalyst in the raw material channel is shown in Figure 3 (a), and the assembled test monolithic solid oxide electrolyzer loaded with small spherical catalyst is shown in Figure 3 (b).

[0032] Example 2 Preparation of carbon dioxide methanation catalyst: Take a nickel precursor solution with a molar ratio of nickel source to aluminum source of 1:9, add water to dilute it. Mix alumina balls with a diameter of about 0.8 mm with it under stirring, heat to 70°C and continue stirring for 24 hours. Then filter out the impregnated alumina balls, place them in a drying oven at 110°C for 12 hours, and calcine them in a muffle furnace at 700°C in an air atmosphere for 3 hours to obtain a nickel-aluminum composite metal oxide carrier prepared by the impregnation method.

[0033] A nickel precursor solution is prepared at a molar ratio of 1:9 between nickel and the metal element in the carrier, and water is added for dilution. The nickel-aluminum composite metal oxide carrier prepared above is added to the solution, and stirring is continued at room temperature for 12 hours. Then the impregnated carrier pellets are filtered out, placed in a drying oven at 110°C for 12 hours, and calcined in a muffle furnace at 700°C in an air atmosphere for 3 hours to obtain a spherical methanation catalyst.

[0034] In addition, carbon dioxide methanation catalysts Ni / NiAl2O4 and Pt / NiAl2O4 were prepared by referring to the method of CN118002133A, and coated on a spherical support to obtain a spherical methanation catalyst.

[0035] The methanation catalyst prepared above was tested for its thermal catalytic activity in the carbon dioxide hydrogenation methanation reaction in a quartz reaction tube (an independent thermal catalytic performance test, not coupled with a solid oxide electrolysis cell).

[0036] The obtained spherical catalyst particles were uniformly mixed with quartz sand of the same mesh size and loaded into the reaction tube of a tubular fixed bed reactor. The temperature was raised to 750°C in a nitrogen atmosphere, and then reduced in a hydrogen atmosphere for 3 hours. Thereafter, a mixture of carbon dioxide, hydrogen and nitrogen (CO2 / H2 / N2=1 / 4 / 1) was introduced into the reaction tube, and the carbon dioxide hydrogenation methanation reaction was carried out in the space velocity range of 10000-90000mL / h / g and the temperature range of 450-600°C. The content of each component in the reaction outlet gas was detected online by a GC-7900II gas chromatograph equipped with a hydrogen flame detector FID.

[0037] Under the conditions of reaction space velocity of 90000 mL / h / g and reaction pressure of normal pressure, the test results of the activity of the catalyst prepared in Example 2 in the carbon dioxide hydrogenation methanation reaction are shown in Figure 4. With the increase of reaction temperature, the carbon dioxide conversion rate and methane yield show a trend of first increasing and then decreasing, and the carbon dioxide conversion rate and methane yield reach a peak at 450℃. In the range of ≤450℃, the methane yield is almost consistent with the carbon dioxide conversion rate, which shows that the catalyst has excellent selectivity. When the temperature exceeds 450℃, the activity test results of the catalyst almost completely coincide with the equilibrium data, which shows that for the current reaction system, the medium and low temperature zones are mainly affected by catalytic kinetics, while the high temperature zone is mainly limited by thermodynamic equilibrium.

[0038] Example 3 A 10 cm×10 cm monolithic solid oxidation electrolytic cell was assembled, and the small spherical catalyst with a diameter of 0.8 mm prepared in Example 2 was evenly loaded into each raw material channel of the cathode side connector of the electrolytic cell in a random loading mode. The activity of the methanation reaction was tested comparatively with and without power supply.

[0039] During the test, the temperature was first raised from room temperature to 830°C at a heating rate of 1°C / min and maintained for 90 minutes to ensure the stability of the electrolytic cell sealing adhesive. The temperature was then lowered to 750°C at a cooling rate of 1°C / min, and the electrodes and catalysts were reduced using hydrogen for 3 hours. After adjusting the temperature to the target reaction temperature, a mixture of carbon dioxide, hydrogen and nitrogen (CO2 / H2 / N2=1 / 4 / 1) was introduced, and the carbon dioxide hydrogenation methanation reaction was tested at an air velocity of 10000mL / h / g and a temperature range of 500-600°C, respectively, with and without power. When powered on, a current was applied to the electrolytic cell at a voltage of 1.5V.

[0040] like Figure 5 As shown in the test, within the range of 500-600°C, the carbon dioxide conversion rate and methane yield in the powered state are significantly improved compared with the non-powered state, and this promotion effect becomes more obvious as the temperature increases. Both the carbon dioxide conversion rate and the methane yield significantly exceed the thermodynamic equilibrium data, that is, they achieve thermodynamic "super equilibrium". The super equilibrium phenomenon that becomes more and more significant with increasing temperature should be mainly attributed to the increase in current caused by the increase in temperature. Higher current allows more water vapor produced by the methanation reaction to be electrolyzed, thereby promoting the right shift of the methanation reaction.

[0041] Example 4 On the basis of Example 3, the inlet gas composition was adjusted, the temperature of the solid oxidation electrolytic cell was 525°C, and the coupling results of the inlet gas composition on the electrolysis reaction and the methanation reaction were shown in Table 1. Within the range of test conditions, the carbon dioxide conversion rate and methane yield under the power-on state were significantly higher than the results under the same conditions without power, and both achieved the phenomenon of transcending thermodynamic equilibrium.

[0042] Table 1 .

[0043] Example 5 At 525℃ and with power on, catalyst pellets of different sizes and different catalyst configurations were used to investigate the effects of catalyst particle size and catalyst layout on the coupling reaction.

[0044] In the energized state, catalysts with diameters of 0.2 mm, 0.8 mm, and 1.5 mm (prepared in the same manner as in Example 2) were used and loaded into the monolithic cell, and the effect of particle diameter was investigated under the condition of inlet gas of CO2 / H2 / H2O=25 / 75 / 25 mL / min (Table 2). In addition, in the energized state, six catalyst configurations were designed, including no catalyst loaded in the raw material channel of the connector, 100% alumina pellets loaded, 100% catalyst pellets loaded, 30% alumina pellets loaded before + 70% catalyst loaded after, 50% alumina pellets loaded before + 50% catalyst loaded after, and 70% alumina pellets loaded before + 30% catalyst loaded after, to investigate the effect of catalyst layout on the coupling reaction (Table 2).

[0045] The methane yield in the case where the connector channel is not filled with catalyst or is completely filled with alumina is much lower than that in the case where the methanogenic catalyst is filled, which confirms the effectiveness of the catalyst. The reaction performance of the 0.8mm pellet catalyst is basically the same as that of the 0.2mm catalyst, but its pressure loss is smaller; while the reaction performance of the 1.5mm pellet catalyst is lower than the former two. The pellet size of about 0.8mm is considered to be the preferred result.

[0046] In the investigation of the catalyst layout, the reactivity obtained in the first 30% alumina pellets + the last 70% catalyst is basically similar to that of the 100% catalyst pellets, and the reactivity of the layout with the first 70% alumina pellets + the last 30% catalyst is poor. Therefore, the layout with 70-100% catalyst is considered to be the preferred result.

[0047] Table 2

Claims

1. A chip structure for in-situ catalytic synthesis of methane coupled to a solid oxide electrolytic cell, characterized in that: The sheet structure comprises a sheet solid oxide electrolytic cell and a carbon dioxide hydrogenation methanation catalyst; the methanation catalyst is loaded in a connector raw material channel on the cathode side of the sheet solid oxide electrolytic cell to form an integrated structure.

2. The sheet structure according to claim 1, characterized in that: The methanation catalyst is a spherical catalyst, and is uniformly loaded into the raw material channel on the cathode side of the connector in the sheet-type solid oxide electrolytic cell in a random loading mode.

3. The sheet structure according to claim 2, characterized in that: The diameter of the methanation catalyst beads is 0.1-1.5 mm; the methanation catalyst beads are completely filled in the raw material channel of the connector on the cathode side of the sheet-type solid oxide electrolyzer, or inert beads of the same particle size are filled in 70%-100% of the rear part of the raw material channel and 0%-30% of the front part of the raw material channel.

4. The sheet structure according to claim 1, 2 or 3, characterized in that: The sheet-type solid oxide electrolytic cell comprises a battery repeating unit, which comprises a cathode, an anode and an electrolyte, and a cathode-anode connector, wherein the connector comprises a cavity structure, forming a raw material channel with the cathode side and an air channel with the anode side.

5. The sheet structure according to claim 1, 2 or 3, characterized in that: The methanation catalyst is a composite metal oxide catalyst, wherein the active component is selected from precious metals Pt, Pd or Ru, or from transition metals Fe, Ni or Co; the carrier is a nickel-aluminum composite metal oxide; the nickel-aluminum composite metal oxide includes nickel oxide and nickel aluminum spinel, wherein the proportion of nickel in the form of nickel oxide to the total amount of nickel element in the carrier is not higher than 10%, and the nickel aluminum spinel includes a chemically equivalent spinel structure NiAl2O4 and a non-chemically equivalent spinel-like structure NixAlyOz, x<1, y>2, z>3.

6. The sheet structure according to claim 5, characterized in that: When the active component of the catalyst is a noble metal such as Pt, Pd or Ru, the loading amount thereof is 0.05-5.0 wt %; when the active component is a transition metal such as Fe, Ni or Co, the loading amount thereof is 0.5-50 wt %.

7. The sheet structure according to claim 5, characterized in that: The methanation catalyst is prepared according to the following method: (1) Alumina beads are immersed in a nickel precursor solution, and after continuous stirring, the solution is filtered, dried and calcined at 600°C-900°C to obtain a nickel-aluminum composite metal oxide carrier; (2) The nickel-aluminum composite metal oxide carrier beads obtained in step (1) and a precursor solution of precious metals Pt, Pd or Ru, or transition metals Fe, Ni or Co are added to a solvent and continuously stirred; (3) The impregnated beads are filtered, dried and then calcined; (4) The calcined catalyst is subjected to a reduction treatment.

8. The sheet structure according to claim 7, characterized in that: In step (1), the nickel precursor is selected from one or more of nickel nitrate, nickel acetate, nickel phosphate, nickel hypophosphite, nickel oxalate, nickel hydroxide or nickel oxide; the molar ratio of nickel to aluminum in the nickel precursor and aluminum oxide is in the range of 0.05-1:1; the impregnation temperature is 25°C-100°C, and the impregnation time is 0.5-48 hours; and the calcination temperature is 700°C-800°C.

9. A method for co-electrolysis of water and carbon dioxide methanogenesis, characterized in that: The sheet structure for in-situ catalytic synthesis of methane in a coupled solid oxide electrolytic cell as described in claim 1 is adopted, a voltage is applied to the sheet solid oxide electrolytic cell, a raw gas containing carbon dioxide, water and / or hydrogen is introduced into the raw material channel of the connector, water vapor and carbon dioxide undergo electrolysis reaction at the cathode of the sheet solid oxide electrolytic cell to generate hydrogen and carbon monoxide; the generated hydrogen, carbon monoxide and carbon dioxide undergo in-situ catalytic methanation reaction on a methanation catalyst in the raw material channel of the connector to generate methane and water.

10. The method for co-electrolysis of water and carbon dioxide for methanogenesis according to claim 9, characterized in that: The reaction temperature in the sheet structure is 500-650°C.

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