Catalyst for electrothermic catalytic methane dry reforming reaction and preparation method thereof

Abstract

The application provides a catalyst for electro-thermal catalytic methane dry reforming reaction and a preparation method thereof, a nanometer Ni catalyst loaded on an Al2O3-TiO2 composite oxide coating prepared on the surface of carbon fiber is constructed to build an integrated material system with transient thermal response capability and catalytic function synergy, so that mechanism driven optimization of DRM reaction, efficient conversion of electric energy into chemical energy and long-term stable operation in a high-temperature CO2 environment are realized. The catalyst is constructed on the surface of carbon fiber through electro-thermal induction, has the characteristics of high interface stability, fast electro-thermal response and strong catalytic activity and the like, is suitable for methane reforming reaction in a high-temperature dry gas environment, is especially suitable for an electro-thermal catalytic system driven by a pulse current and has the application potential of efficient conversion of green electric energy into chemical energy.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, and in particular relates to a catalyst for electrothermal catalytic reforming of methane dry gas and its preparation method. Background Technology

[0002] Dry methane reforming (DRM) is a high-temperature, endothermic reaction process that co-converts the greenhouse gas methane (CH4) and carbon dioxide (CO2) into syngas (CO+H2). It possesses significant carbon reduction potential and feedstock utilization value, and is widely used in atmosphere control during the synthesis of fuels, chemical production, and metallurgical processes. With an enthalpy as high as 247 kJ / mol, this reaction requires substantial energy input and typically operates above 800°C. Therefore, it has the potential to convert electrical energy into chemical energy and achieve energy storage, making it a key node in green energy consumption and carbon cycle engineering.

[0003] However, the endothermic nature of the DRM reaction is not uniformly distributed throughout the entire reaction process, but rather concentrated in specific elementary steps, especially during C–H bond breaking and CO2 activation. These steps have high energy barriers, requiring rapid, localized energy injection at the catalytic interface. Traditional heat source systems (such as external furnaces or heat exchangers) are based on steady-state heat conduction mechanisms and cannot achieve unsteady-state heating synchronized with the elementary reactions, resulting in low thermal efficiency, deviation of the catalytic pathway from the optimal reaction coordinates, and severely limiting the reaction rate and selectivity.

[0004] In recent years, electrothermal catalysis technology has gradually emerged, achieving in-situ Joule heating by applying electric current to conductive materials, providing a rapid and controllable heat source for high-temperature catalytic reactions. More importantly, electrothermal catalysis technology, by applying electric current to conductive materials to achieve in-situ Joule heating, possesses millisecond-level thermal response capabilities and can directly generate a controllable local thermal field at the catalytic interface, thereby achieving unsteady-state heating in synergy with elementary steps. This "electro-thermal-chemical" coupling pathway not only improves reaction kinetics but also enables the DRM reaction to directly convert electrical energy into chemical energy, constructing an electrically driven syngas production platform, which has significant strategic value in the context of renewable energy.

[0005] In electrothermal catalysis systems, carbon materials, due to their high electrical conductivity, rapid thermal response, and structural flexibility, can achieve localized heating to over 1000°C within millisecond timescales. Furthermore, their interface designability allows for the construction of tightly coupled structures with catalytically active components, achieving synergistic catalytic-electrothermal drive. These characteristics make carbon materials ideal electrothermal elements capable of meeting the aforementioned unsteady-state heating requirements. However, carbon materials are prone to oxidation or interfacial carbonization reactions in high-temperature CO2 atmospheres, leading to structural degradation, decreased conductivity, and even catalytic deactivation, severely limiting their long-term stable application in electrothermal catalytic DRM systems. Summary of the Invention

[0006] In view of this, the present invention aims to propose a catalyst for electrothermal catalytic methane dry gas reforming reaction and its preparation method. The catalyst is prepared by loading nano-Ni catalyst with Al2O3-TiO2 composite oxide coating on carbon fiber surface, and constructing an integrated material system with transient thermal response capability and synergistic catalytic function, so as to achieve mechanism-driven optimization of DRM reaction, efficient conversion of electrical energy to chemical energy, and long-term stable operation in high temperature CO2 environment.

[0007] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0008] A method for preparing a catalyst for electrothermal catalytic reforming of dry methane gas, the method comprising the following steps:

[0009] S1. Use strong oxidants to modify the surface of the carbon fiber matrix to introduce oxygen-containing functional groups and enhance hydrophilicity and coating adhesion.

[0010] S2. The titanium source precursor and the aluminum source precursor are dissolved in a solvent to form a composite oxide precursor solution. The carbon fiber matrix treated in S1 is immersed in the composite oxide precursor solution and dried in air to form an Al2O3–TiO2 composite oxide coating.

[0011] S3. Dissolve the nickel source precursor in a solvent to form a nickel source precursor solution. Immerse the carbon fiber matrix treated in S2 in the nickel source precursor solution and dry it to form a Ni precursor loading layer.

[0012] S4. The material treated in S3 is placed in an electrothermal reactor and subjected to high-temperature electrothermal treatment under an inert atmosphere by applying a pulsed current, so that the precursor is converted into the corresponding oxide and a stable bilayer composite oxide structure is formed.

[0013] S5. Continue to apply electrothermal treatment in a hydrogen atmosphere to reduce Ni oxide to metallic Ni in situ, forming a dispersed Ni active phase, while stabilizing the material structure and interfacial bonding force, to obtain a catalyst for electrothermal catalytic reforming of methane dry gas.

[0014] The endothermic nature of the DRM reaction is concentrated in specific elementary steps, especially the C–H bond breaking of methane and the activation of CO2, which require instantaneous, high-temperature, and localized energy injection at the catalytic interface. Traditional steady-state heat sources cannot achieve dynamic heating synchronized with the elementary reactions, causing the catalytic path to deviate from the optimal reaction coordinates and limiting reaction performance. The catalyst described in this invention is electrothermally induced and constructed on the surface of carbon fibers, exhibiting high interfacial stability, fast electrothermal response, and strong catalytic activity. It is suitable for methane reforming reactions under high-temperature dry gas environments, and is particularly well-suited for pulsed current-driven electrothermal catalytic systems.

[0015] The strong metal-support interaction between TiO2 and Ni is beneficial for improving catalyst stability. Furthermore, TiO2 readily forms oxygen vacancies, which facilitates CO2 molecule adsorption and promotes the reaction. However, TiO2 has a low specific surface area and poor mechanical strength, and it transforms from anatase to rutile at high temperatures, making it unsuitable for high-temperature reactions. By introducing the thermally stable second metal oxide Al2O3, the thermal stability of TiO2 is enhanced.

[0016] Al₂O₃ has a large specific surface area, which can disperse Ni particles through the high specific surface area and strong metal-support interaction, enhancing structural stability and preventing deactivation due to sintering during high-temperature reactions. Incorporating TiO₂ into the Al₂O₃ support can improve metal dispersion, reduce particle sintering, enhance thermal stability, improve oxygen storage capacity, and facilitate the production of carbon in gasification reforming reactions.

[0017] Furthermore, in S1, the strong oxidant is one of concentrated nitric acid solution, potassium permanganate, or ozone water, and the carbon fiber matrix is ​​soaked in the strong oxidant for 30-60 minutes; the carbon fiber matrix is ​​a conductive carbon material.

[0018] Preferably, the carbon fiber matrix can be carbon fiber felt, carbon paper, or other conductive carbon materials.

[0019] Concentrated nitric acid solution can be nitric acid with a volume concentration of 96%–98%.

[0020] The treated carbon fiber matrix was washed with deionized water and high-purity ethanol (99.9% ethanol by volume) until neutral to obtain a carbon fiber matrix with enhanced surface activity.

[0021] Furthermore, in S2, the molar concentration of Ti in the composite oxide precursor solution is 0.01-0.2 mol / L, and the molar concentration of Al is 0.01-0.2 mol / L; the soaking time is 40-50 min, the drying temperature is 60-80℃, and the drying time is ≥1 h; the molar fraction of TiO2 in the Al2O3–TiO2 composite oxide coating is 10%-30%.

[0022] The titanium source is one of the alkoxide titanium sources, the aluminum source is one of the alkoxide aluminum sources, and the solvent is anhydrous ethanol.

[0023] Alkoxide titanium sources include, but are not limited to, tetraisopropoxide titanium and tetrabutyl titanate; alkoxide aluminum sources include, but are not limited to, sec-butoxide aluminum.

[0024] Furthermore, in S3, the molar concentration of Ni in the nickel source precursor solution is 0.01-1 mol / L, soaking for 40-50 min, drying temperature is 60-80℃, and drying time is ≥1 h; the nickel source is one of the nickel metal salts, and the solvent is a mixed solvent of ethanol and water, with a volume ratio of ethanol to water of 9:1.

[0025] Nickel metal salts include, but are not limited to, nickel nitrate hexahydrate and nickel chloride.

[0026] Furthermore, in step S3, a magnesium source precursor is added, that is, the nickel source precursor and the magnesium source precursor are dissolved in a solvent to form a mixed precursor solution. The carbon fiber matrix treated in step S2 is immersed in the mixed precursor solution and dried to form a Ni and Mg precursor loading layer. The magnesium source is one of the magnesium metal salts.

[0027] Magnesium metal salts include, but are not limited to, magnesium nitrate hexahydrate and magnesium chloride.

[0028] Furthermore, in the mixed precursor solution, the molar concentration of Ni is 0.01-1 mol / L and the molar concentration of Mg is 0.005-0.5 mol / L.

[0029] Furthermore, in S4, the parameters of the pulse current are: pulse frequency of 0.5-1Hz, pulse current duty cycle of 6%-20%, current value of 10-20A, voltage limit of ≥100V, cyclic heating 3-7 times, and temperature peak of 1000-1200K.

[0030] Furthermore, in S5, the heating power is 30-40W, the reduction temperature is 650-700℃, and the time is 1-2h.

[0031] The present invention also provides a catalyst for electrothermal catalytic reforming of methane dry gas, prepared by the preparation method described above.

[0032] The present invention also provides an application of the catalyst as described above for electrothermal catalytic reforming of dry methane gas, wherein a pulsed current is applied during the catalytic process.

[0033] Compared with existing technologies, the catalyst and its preparation method for electrothermal catalytic reforming of methane dry gas described in this invention have the following advantages:

[0034] (1) Fast electrothermal response: The catalyst and the electrothermal body are constructed in the same position to achieve synergistic driving of catalysis and heat source.

[0035] (2) Strong interface stability: The double-layer oxide coating effectively isolates the carbon matrix from the reactive gas, improving the high-temperature oxidation resistance.

[0036] (3) High catalytic activity: The Ni active phase and MgO auxiliary agent work synergistically to enhance CO2 activation and anti-carbon deposition ability.

[0037] (4) Simple and controllable process: No need for high-temperature furnace treatment, and it is compatible with pulse power supply and modular reactor design.

[0038] (5) High adaptability: The size and shape of the carbon fiber matrix can be flexibly adjusted according to the reactor structure without affecting the catalytic performance.

[0039] (6) It is not only applicable to dry reforming of methane, but can also be extended to other high-temperature electrothermal catalytic processes, with broad industrial application prospects and strategic value for carbon neutrality. Attached Figure Description

[0040] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0041] Figure 1 The image shows the SEM morphology of the Ni / Al2O3–TiO2 / CF catalyst prepared in Example 1 of this invention.

[0042] Figure 2 The graph shows the electrothermal catalytic data of methane dry gas reforming reaction of the Ni / Al2O3–TiO2 / CF catalyst prepared in Example 1 of this invention at various heating powers; (a) shows the CO2 and CH4 conversion rates; (b) shows the H2 selectivity.

[0043] Figure 3 The image shows the SEM morphology of the Ni+MgO / Al2O3–TiO2 / CF catalyst prepared in Example 2 of this invention.

[0044] Figure 4 The graph shows the electrothermal catalytic data of methane dry gas reforming reaction of the Ni+MgO / Al2O3–TiO2 / CF catalyst prepared in Example 2 of this invention at various heating powers; (a) CO2 and CH4 conversion rates; (b) H2 selectivity.

[0045] Figure 5 The following are graphs showing the data of the various catalysts prepared in Example 3 of the present invention under different duty cycles of pulse electrothermal catalysis for dry gas reforming of methane at an average heating power of approximately 15 W; (a) shows the conversion rates of CO2 and CH4; (b) shows the selectivity of H2.

[0046] Figure 6 The graph shows the electrothermal catalytic data of the methane dry gas reforming reaction of the catalyst prepared in Comparative Example 1 at various heating powers; (a) CO2 and CH4 conversion rates; (b) H2 selectivity.

[0047] Figure 7 The graph shows the electrothermal catalytic data of the methane dry gas reforming reaction of the catalyst prepared in Comparative Example 2 at various heating powers; (a) CO2 and CH4 conversion rates; (b) H2 selectivity.

[0048] Figure 8 The graph shows the electrothermal catalytic data of the methane dry gas reforming reaction of the catalyst prepared in Comparative Example 3 at various heating powers; (a) CO2 and CH4 conversion rates; (b) H2 selectivity.

[0049] Figure 9 The graph shows the electrothermal catalytic reforming data of methane dry gas prepared by the catalyst in Comparative Example 4 at various heating powers; (a) shows the CO2 and CH4 conversion rates; (b) shows the H2 selectivity. Detailed Implementation

[0050] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Example 1 Ni / Al2O3–TiO2 / CF catalyst

[0053] The preparation method of Ni / Al2O3–TiO2 / CF catalyst is as follows:

[0054] S1. Cut the clean carbon fiber felt into strips of 50mm×8mm×3mm, soak them in concentrated nitric acid with a volume concentration of 98% for 30 minutes to introduce oxygen-containing functional groups, and then wash them alternately with deionized water and anhydrous ethanol until neutral to obtain a surface-modified carbon fiber matrix.

[0055] S2. Dissolve 0.313g of titanium tetraisopropoxide and 2.219g of aluminum sec-butoxide in anhydrous ethanol to prepare 100ml of composite oxide precursor solution with a total molar concentration of 0.1mol / L. Immerse the carbon fiber felt treated in S1 in the composite oxide precursor solution for 40min, remove it and dry it in an 80℃ electric heating oven for 1h to form an Al2O3–TiO2 composite oxide coating.

[0056] S3. Dissolve 2.908g of the nickel source precursor Ni(NO3)2•6H2O in 100ml of alcohol-water mixed solution (volume ratio 9:1) to form a nickel source precursor solution with a Ni molar concentration of 0.1mol / L. Immerse the carbon fiber matrix treated in S2 in the nickel source precursor solution for 40min, remove it and dry it again at 80℃ for 1h to form a Ni precursor loading layer.

[0057] S4. Place the material treated in S3 into an electrothermal reactor, introduce argon gas for protection, apply pulsed current: frequency 1Hz, duty cycle 6%, current value 20A, voltage upper limit 100V, and cycle heating 5 times to about 1100K; so that the Ni precursor is converted into the corresponding oxide, forming a stable bilayer composite oxide structure.

[0058] S5. Subsequently, a 5% H2 / Ar mixed gas was introduced, and the reaction temperature was maintained at 650℃ for 1 hour under a heating power of about 30W to achieve in-situ reduction and structural stabilization of Ni, thus obtaining the Ni / Al2O3–TiO2 / CF catalyst.

[0059] The catalyst contains 20% TiO2 in the Al2O3–TiO2 composite oxide coating, such as... Figure 1 As shown, the Al2O3–TiO2 composite oxide coating can effectively control the distribution and size of Ni particles.

[0060] Figure 2 This catalyst was demonstrated at 600 L / g Ni Electrothermal catalytic reforming performance of methane dry gas at a space velocity of / h. The catalyst exhibited high CO2 conversion (92.1%), CH4 conversion (88.8%), and H2 selectivity (94.5%) under constant current heating (100% duty cycle) at an electrothermal power of 70W.

[0061] Example 2 Ni+MgO / Al2O3–TiO2 / CF catalyst

[0062] The catalyst is prepared as follows:

[0063] S1. Cut the clean carbon fiber felt into strips of 50mm×8mm×3mm, soak them in concentrated nitric acid with a volume concentration of 98% for 30 minutes to introduce oxygen-containing functional groups, and then wash them alternately with deionized water and anhydrous ethanol until neutral to obtain a surface-modified carbon fiber matrix.

[0064] S2. Dissolve 0.313g of titanium tetraisopropoxide and 2.219g of aluminum sec-butoxide in anhydrous ethanol to prepare 100ml of composite oxide precursor solution; immerse the carbon fiber felt treated in S1 in the composite oxide precursor solution for 40min, remove it and dry it in an 80℃ electric heating oven for 1h to form an Al2O3–TiO2 composite oxide coating.

[0065] S3. Dissolve 2.908 g of nickel source precursor Ni(NO3)2•6H2O and 1.282 g of magnesium source precursor Mg(NO3)2•6H2O in 100 ml of an alcohol-water mixture (volume ratio 9:1) to form a Ni solution with a concentration of 0.1 mol / L. 2+ With 0.05 mol / L Mg2+ The carbon fiber matrix treated with S2 was immersed in the mixed precursor solution for 40 min, and then dried again at 80 °C for 1 h to form a Ni precursor loading layer.

[0066] S4. Place the material treated in S3 into an electrothermal reactor, introduce argon gas for protection, apply pulsed current: frequency 1Hz, duty cycle 6%, current value 20A, voltage upper limit 100V, and cycle heating 5 times to about 1100K; so that the Ni precursor is converted into the corresponding oxide, forming a stable bilayer composite oxide structure.

[0067] S5. Subsequently, a 5% H2 / Ar mixed gas was introduced, and the reaction temperature was maintained at 650℃ for 1 hour under a heating power of about 30W to achieve in-situ reduction and structural stabilization of Ni, thus obtaining the Ni+MgO / Al2O3–TiO2 / CF catalyst.

[0068] The morphology of the catalyst is as follows Figure 3 As shown, the addition of MgO helps reduce the Ni particle size and enhance catalyst performance. The molar fraction of TiO2 in this catalyst is 20% of the Al2O3–TiO2 composite oxide coating.

[0069] Figure 4 This catalyst was demonstrated at 600 L / g Ni The electrothermal catalytic reforming performance of methane dry gas at a space velocity of / h showed that the catalyst, under a constant current heating method (100% duty cycle current) with an electrothermal power of 70W, exhibited high CO2 conversion (94.7%), CH4 conversion (94.8%), and H2 selectivity (98.0%).

[0070] The addition of MgO in Example 2 further improves the CO2 conversion rate, CH4 conversion rate, and H2 selectivity.

[0071] Example 3: Effect of pulse heating with different duty cycles

[0072] The catalyst was prepared as in Example 2, and the Ni+MgO / Al2O3–TiO2 / CF catalyst was obtained in the same way.

[0073] Figure 5 The catalyst was demonstrated at 600 L / g NiThe performance of pulsed electrothermal catalytic reforming of methane dry gas at a space velocity of / h was studied. The catalyst was pulse-heated at an average electrothermal power of 15W, 1Hz, and duty cycles of 10%, 20%, 50%, and 100%. It can be seen that, under the same heating power, the catalytic conversion rate and selectivity initially increase and then decrease with increasing pulse energy density (decreasing duty cycle). This is because, under the same heating power conditions, different pulse current duty cycles correspond to different instantaneous pulse powers, resulting in different instantaneous temperatures and final catalytic effects.

[0074] The results show that, under unsteady-state pulse heating, carbon-based catalysts, due to their low heat capacity and other characteristics, can achieve rapid and wide-range temperature changes, making them more suitable for discontinuous pulse heating. Appropriately controlling the pulse duty cycle is beneficial for regulating the elementary steps of the catalytic reaction and improving electrothermal catalytic performance.

[0075] Comparative Example 1: Ni / Al2O3 / CF catalyst

[0076] The catalyst is prepared as follows:

[0077] S1. Cut the clean carbon fiber felt into strips of 50mm×8mm×3mm, soak them in concentrated nitric acid with a volume concentration of 98% for 30 minutes to introduce oxygen-containing functional groups, and then wash them alternately with deionized water and anhydrous ethanol until neutral to obtain a surface-modified carbon fiber matrix.

[0078] S2. Dissolve 2.463g of aluminum source sec-butoxide in anhydrous ethanol to prepare 100ml of composite oxide precursor solution; immerse the carbon fiber felt treated in S1 in the composite oxide precursor solution for 40min, take it out and dry it in an 80℃ electric heating oven for 1h to form an Al2O3 coating.

[0079] S3. Dissolve 2.908 g of Ni(NO3)2•6H2O in 100 ml of an alcohol-water mixture (volume ratio 9:1) to form a Ni solution with a concentration of 0.1 mol / L. 2+ Precursor solution: The carbon fiber matrix treated with S2 was immersed in the precursor solution for 40 min, and then dried again at 80℃ for 1 h to form a Ni precursor loading layer.

[0080] S4. Place the material treated in S3 into an electrothermal reactor, introduce argon gas for protection, apply pulsed current: frequency 1Hz, duty cycle 6%, current value 20A, voltage upper limit 100V, and cycle heating 5 times to about 1100K; so that the Ni precursor is converted into the corresponding oxide, forming a stable bilayer composite oxide structure.

[0081] S5. Subsequently, a 5% H2 / Ar mixed gas was introduced, and the reaction temperature was maintained at 650℃ for 1 hour under a heating power of about 30W to achieve in-situ reduction and structural stabilization of Ni, thus obtaining the Ni / Al2O3 / CF catalyst.

[0082] Figure 6 This catalyst demonstrates its performance at 600 L / g Ni The electrothermal catalytic reforming performance of methane dry gas at a space velocity of / h was as follows: under 70W electrothermal power and constant current heating (100% duty cycle current), the CO2 conversion rate (91.9%), CH4 conversion rate (87.6%), and H2 selectivity (93.2%) were all lower than those of the Ni / Al2O3-TiO2 / CF catalyst in Example 1.

[0083] Comparative Example 2: Ni / TiO2 / CF Catalyst

[0084] The catalyst is prepared as follows:

[0085] S1. Cut the clean carbon fiber felt into strips of 50mm×8mm×3mm, soak them in concentrated nitric acid with a volume concentration of 98% for 30 minutes to introduce oxygen-containing functional groups, and then wash them alternately with deionized water and anhydrous ethanol until neutral to obtain a surface-modified carbon fiber matrix.

[0086] S2. Dissolve 2.843g of tetraisopropoxide titanium in anhydrous ethanol to prepare 100ml of composite oxide precursor solution; immerse the carbon fiber felt treated in S1 in the composite oxide precursor solution for 40min, take it out and place it in an 80℃ electric heating oven to dry for 1h, so that the oxide precursor is hydrolyzed and forms a TiO2 coating.

[0087] S3. Dissolve 2.908 g of Ni(NO3)2•6H2O in 100 ml of an alcohol-water mixture (volume ratio 9:1) to form a Ni solution with a concentration of 0.1 mol / L. 2+ Precursor solution: The carbon fiber matrix treated with S2 was immersed in the precursor solution for 40 min, and then dried again at 80℃ for 1 h to form a Ni precursor loading layer.

[0088] S4. Place the material treated in S3 into an electrothermal reactor, introduce argon gas for protection, apply pulsed current: frequency 1Hz, duty cycle 6%, current value 20A, voltage upper limit 100V, and cycle heating 5 times to about 1100K; so that the Ni precursor is converted into the corresponding oxide, forming a stable bilayer composite oxide structure.

[0089] S5. Subsequently, a 5% H2 / Ar mixed gas was introduced, and the reaction temperature was maintained at 650℃ for 1 hour under a heating power of about 30W to achieve in-situ reduction and structural stabilization of Ni, thus obtaining the Ni / TiO2 / CF catalyst.

[0090] Figure 7 This catalyst demonstrates its performance at 600 L / g Ni Electrothermal catalytic performance of methane dry gas reforming at a space velocity of / h. The catalyst was heated to a constant current (100% duty cycle) at an electrothermal power of 70W, with CO2 conversion (46.2%), CH4 conversion (39.0%), and H2 selectivity (94.1%). The CH4 and CO2 conversions were significantly lower than those of the Ni / Al2O3-TiO2 / CF catalyst in Example 1. This is because TiO2 has a low specific surface area and poor mechanical strength, and transforms from anatase to rutile at high temperatures, making it unsuitable for high-temperature reactions. Furthermore, the strong metal-support interaction between TiO2 and Ni easily leads to the formation of a TiO2-encapsulated Ni structure at high temperatures, affecting catalytic activity and resulting in lower catalyst conversion and poor stability at various temperatures, ultimately leading to deactivation at high temperatures.

[0091] Comparative Example 3: Different Al and Ti oxide ratios

[0092] The catalyst is prepared as follows:

[0093] S1. Cut the clean carbon fiber felt into strips of 50mm×8mm×3mm, soak them in concentrated nitric acid with a volume concentration of 98% for 30 minutes to introduce oxygen-containing functional groups, and then wash them alternately with deionized water and anhydrous ethanol until neutral to obtain a surface-modified carbon fiber matrix.

[0094] S2. Dissolve 0.711 g of titanium tetraisopropoxide and 1.847 g of aluminum sec-butoxide in anhydrous ethanol to prepare 100 ml of composite oxide precursor solution; immerse the carbon fiber felt treated in S1 in the composite oxide precursor solution for 40 min, remove it and dry it in an 80℃ electric heating oven for 1 h to form an Al2O3–TiO2 composite oxide coating.

[0095] S3. Dissolve 2.908g of nickel source precursor Ni(NO3)2•6H2O in 100ml of alcohol-water mixed solution (volume ratio 9:1) to form nickel source precursor solution. Immerse the carbon fiber matrix treated in S2 in the nickel source precursor solution for 40min. After taking it out, dry it again at 80℃ for 1h to form Ni precursor loading layer.

[0096] S4. Place the material treated in S3 into an electrothermal reactor, introduce argon gas for protection, apply pulsed current: frequency 1Hz, duty cycle 6%, current value 20A, voltage upper limit 100V, and cycle heating 5 times to about 1100K; so that the Ni precursor is converted into the corresponding oxide, forming a stable bilayer composite oxide structure.

[0097] S5. Subsequently, a 5% H2 / Ar mixed gas was introduced, and the reaction temperature was maintained at 650℃ for 1 hour under a heating power of about 30W to achieve in-situ reduction and structural stabilization of Ni, thus obtaining the Ni / Al2O3–TiO2 / CF catalyst.

[0098] The catalyst contains 40% TiO2 in the Al2O3–TiO2 composite oxide coating. Figure 8 This catalyst demonstrates its performance at 600 L / g Ni The electrothermal catalytic reforming performance of methane dry gas at a space velocity of / h was as follows: under constant current heating (100% duty cycle) at an electrothermal power of 70W, the CO2 conversion rate (90.7%), CH4 conversion rate (87.2%), and H2 selectivity (94.1%) were all lower than those of the Ni / Al2O3-TiO2 / CF catalyst in Example 1.

[0099] Comparative Example 4: Different Al and Ti oxide ratios

[0100] The catalyst is prepared as follows:

[0101] S1. Cut the clean carbon fiber felt into strips of 50mm×8mm×3mm, soak them in concentrated nitric acid with a volume concentration of 98% for 30 minutes to introduce oxygen-containing functional groups, and then wash them alternately with deionized water and anhydrous ethanol until neutral to obtain a surface-modified carbon fiber matrix.

[0102] S2. Dissolve 1.222 g of tetraisopropoxide titanium and 1.404 g of sec-butoxide aluminum in anhydrous ethanol to prepare 100 ml of composite oxide precursor solution; immerse the carbon fiber felt treated in S1 in the composite oxide precursor solution for 40 min, take it out and dry it in an 80℃ electric heating oven for 1 h to form an Al2O3–TiO2 composite oxide coating.

[0103] S3. Dissolve 2.908g of nickel source precursor Ni(NO3)2•6H2O in 100ml of alcohol-water mixed solution (volume ratio 9:1) to form nickel source precursor solution. Immerse the carbon fiber matrix treated in S2 in the nickel source precursor solution for 40min. After taking it out, dry it again at 80℃ for 1h to form Ni precursor loading layer.

[0104] S4. Place the material treated in S3 into an electrothermal reactor, introduce argon gas for protection, apply pulsed current: frequency 1Hz, duty cycle 6%, current value 20A, voltage upper limit 100V, and cycle heating 5 times to about 1100K; so that the Ni precursor is converted into the corresponding oxide, forming a stable bilayer composite oxide structure.

[0105] S5. Subsequently, a 5% H2 / Ar mixed gas was introduced, and the reaction temperature was maintained at 650℃ for 1 hour under a heating power of about 30W to achieve in-situ reduction and structural stabilization of Ni, thus obtaining the Ni / Al2O3–TiO2 / CF catalyst.

[0106] The catalyst contains 60% TiO2 in the Al2O3–TiO2 composite oxide coating. Figure 9 This catalyst demonstrates its performance at 600 L / g Ni The electrothermal catalytic performance of methane dry gas reforming at a space velocity of / h showed that the catalyst's CO2 conversion (88.2%), CH4 conversion (83.9%), and H2 selectivity (93.7%) were all lower than those of the Ni / Al2O3-TiO2 / CF catalyst in Example 1 at a 70W electrothermal power.

[0107] Comparative Examples 1 and 1-4 demonstrate that appropriately doped Al2O3 (10%-30%) Al2O3–TiO2 composite oxide coatings are beneficial for improving catalytic activity. Al2O3 has a large specific surface area, which can disperse Ni particles through high specific surface area and strong metal-support interaction, enhancing structural stability and preventing deactivation due to sintering during high-temperature reactions. Incorporating TiO2 into the Al2O3 support can improve metal dispersion, reduce particle sintering, enhance thermal stability, increase oxygen storage capacity, facilitate the vaporization of carbon generated in the gasification and reforming reaction, and improve catalyst performance.

[0108] In addition, the carbon material used in the catalyst prepared by the method of the present invention does not undergo oxidation or interfacial carbonization reaction in a high-temperature CO2 atmosphere, nor does it experience electrothermal structure reduction, decreased conductivity, or even catalytic deactivation. The catalyst can be used stably for a long time in the electrothermal catalytic DRM system.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a catalyst for electrothermal catalytic reforming of dry methane gas, characterized in that: The method includes the following steps: S1. Surface modification treatment of carbon fiber matrix using strong oxidizing agent; S2. The titanium source precursor and the aluminum source precursor are dissolved in a solvent to form a composite oxide precursor solution. The carbon fiber matrix treated in S1 is immersed in the composite oxide precursor solution and dried in air to form an Al2O3–TiO2 composite oxide coating. The molar concentration of Ti in the composite oxide precursor solution is 0.01-0.2 mol / L, and the molar concentration of Al is 0.01-0.2 mol / L. Soak for 40-50 minutes, dry at 60-80℃, and dry for ≥1 hour; TiO2 accounts for 10%-30% of the molar fraction of the Al2O3–TiO2 composite oxide coating; The titanium source is one of the alkoxide titanium sources, the aluminum source is one of the alkoxide aluminum sources, and the solvent is anhydrous ethanol; S3. Dissolve the nickel source precursor in a solvent to form a nickel source precursor solution. Immerse the carbon fiber matrix treated in S2 in the nickel source precursor solution and dry it to form a Ni precursor loading layer. S4. The material treated in S3 is placed in an electrothermal reactor and subjected to high-temperature electrothermal treatment under an inert atmosphere by applying a pulsed current, so that the precursor is converted into the corresponding oxide and a stable bilayer composite oxide structure is formed. S5. Continue to apply electrothermal treatment in a hydrogen atmosphere to reduce Ni oxide to metallic Ni in situ, forming a dispersed Ni active phase, and obtain a catalyst for electrothermal catalytic reforming of methane dry gas.

2. The method for preparing the catalyst for electrothermal catalytic reforming of methane dry gas according to claim 1, characterized in that: In S1, the strong oxidant is one of concentrated nitric acid solution, potassium permanganate, or ozone water. The carbon fiber matrix is ​​soaked in the strong oxidant for 30-60 minutes. The carbon fiber matrix is ​​a conductive carbon material, and the concentrated nitric acid solution is nitric acid with a volume concentration of 96%–98%.

3. The method for preparing the catalyst for electrothermal catalytic reforming of methane dry gas according to claim 1, characterized in that: In S3, the molar concentration of Ni in the nickel source precursor solution is 0.01-1 mol / L, soaking for 40-50 min, drying temperature is 60-80℃, and drying time is ≥1 h; the nickel source is one of the nickel metal salts; the solvent is a mixed solvent of ethanol and water, with a volume ratio of ethanol to water of 9:

1.

4. The method for preparing the catalyst for electrothermal catalytic reforming of methane dry gas according to claim 1, characterized in that: In step S3, a magnesium source precursor is added, which is to dissolve the nickel source precursor and the magnesium source precursor in a solvent to form a mixed precursor solution. The carbon fiber matrix treated in step S2 is then immersed in the mixed precursor solution and dried to form a Ni and Mg precursor loading layer. The magnesium source is one of the magnesium metal salts.

5. The method for preparing the catalyst for electrothermal catalytic reforming of methane dry gas according to claim 4, characterized in that: In the mixed precursor solution, the molar concentration of Ni is 0.01-1 mol / L and the molar concentration of Mg is 0.005-0.5 mol / L.

6. The method for preparing the catalyst for electrothermal catalytic reforming of methane dry gas according to claim 1, characterized in that: In S4, the parameters of the pulse current are: pulse frequency of 0.5-1Hz, pulse current duty cycle of 6%-20%, current value of 10-20A, voltage limit of ≥100V, cyclic heating 3-7 times, and temperature peak of 1000-1200K.

7. The method for preparing the catalyst for electrothermal catalytic reforming of methane dry gas according to claim 1, characterized in that: In S5, the heating power is 30-40W, the reduction temperature is 650-700℃, and the time is 1-2h.

8. A catalyst for electrothermal catalytic reforming of dry methane gas, prepared by the method according to any one of claims 1-7.

9. The application of the catalyst as described in claim 8 for the electrothermal catalytic reforming of dry methane gas, characterized in that: A pulsed current is applied during the catalytic process.

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