A molybdenum-based monolithic catalyst, a preparation method and applications thereof

Abstract

The application provides a molybdenum-based monolithic catalyst, a preparation method and application thereof, and the preparation method comprises the following steps: S1, providing an electrically conductive carbon carrier and pretreating; S2, mixing a molybdenum-based precursor and a high-molecular alcohol substance in water to form a stable impregnation liquid system; S3, placing the pretreated electrically conductive carbon carrier into the impregnation liquid system, ultrasonic impregnating, and then drying to obtain a catalyst precursor; and S4, calcining the catalyst precursor under an inert gas to obtain the molybdenum-based monolithic catalyst. The application adopts a modified impregnation liquid to replace a traditional modified carrier strategy, improves the wettability of the impregnation liquid to the hydrophobic electrically conductive carbon carrier, and ensures the uniform distribution of the molybdenum-based active component on the electrically conductive carbon carrier. In addition, a core-shell high-activity catalytic structure of MoO2 core-molybdenum carbide shell is constructed, which can synergistically significantly improve the catalytic activity and stability.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, and in particular relates to a molybdenum-based monolithic catalyst, its preparation method, and its application. Background Technology

[0002] Against the backdrop of electrification in chemical processes, the built-in Joule heated fixed-bed reactor is an emerging type of thermocatalytic reactor. Due to its small volume, energy efficiency, and flexible temperature control, it has gradually become a research hotspot. The core of this reactor lies in its heating element, which typically employs a conductive, structured monolithic catalyst. These monolithic catalysts are usually prepared by loading active components onto the surface of a support material, including metal foam, polyurethane (PU) sponge, SiC, and carbon paper.

[0003] Thermocatalytic reverse water-gas shift reaction is a mature and effective carbon dioxide conversion pathway. Among these, molybdenum-based catalysts are ideal catalysts due to their low cost, high CO2 conversion rate, and near 100% CO selectivity. To achieve efficient electrification of this reaction, a monolithic catalyst needs to be constructed and used as a Joule heating element. Graphite felt, with its excellent electrical conductivity and chemical inertness, is an ideal carbon-based support.

[0004] Graphite felt typically has poor wettability and requires appropriate modification to facilitate impregnation or growth of various active materials. Conventional modification methods involve increasing its hydrophilicity through high-temperature calcination and chemical oxidation; however, these methods often require harsh conditions or the use of hazardous chemical reagents. Another feasible approach is to use binders to enhance the bonding between the catalyst and the support. In the field of electrochemistry, perfluorosulfonic acid resin (Nafion solution) is commonly added as a binder. Its strong molecular-solid interaction can immobilize the catalyst on carbon supports such as carbon cloth. However, Nafion solution is relatively expensive, and the high material cost is a significant obstacle to its large-scale application.

[0005] It is worth noting that the Joule thermocatalysis process differs fundamentally from traditional liquid-phase electrocatalysis. In the former's impregnation-heat treatment process, the catalyst, after loading, is not immersed in the solution for an extended period to participate in subsequent electrochemical reactions, eliminating concerns about catalyst dissolution or detachment in the electrolyte. This characteristic allows for the selection of low-cost, volatile modifiers. Ethanol, as an inexpensive and readily available alcohol modifier, is often used to improve the hydrophilicity of graphite felt. However, in practice, it has been found that ethanol reduces the polarity of aqueous solutions. This reduction in polarity disrupts the solvation environment of the molybdenum-based precursor in water, causing molybdate ions to combine with hydrogen ions in the solution and undergo hydrolysis, generating insoluble molybdenum hydroxide or molybdate precipitates. These precipitates cannot be removed by ethanol evaporation; instead, they deposit on the surface or in the pores of the graphite felt, clogging the pores and forming an uneven coating. Ultimately, this leads to low catalyst loading, insufficient exposure of active sites, and catalyst performance degradation.

[0006] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a molybdenum-based monolithic catalyst, its preparation method and its application, to solve the problems of hydrolysis and precipitation of molybdenum-based precursors and the inability to uniformly impregnate them caused by the use of alcohol modifiers such as ethanol in the prior art.

[0008] To achieve the above and other related objectives, the present invention provides a method for preparing a molybdenum-based monolithic catalyst, the method comprising the following steps:

[0009] S1. Provide a conductive carbonaceous carrier and perform pretreatment;

[0010] S2. The molybdenum-based precursor is mixed with a high molecular weight alcohol in water to form a stable impregnation solution system, wherein the high molecular weight alcohol is used to inhibit the hydrolysis and precipitation of molybdate ions.

[0011] S3. The pretreated conductive carbonaceous support is placed in the impregnation liquid system, ultrasonically impregnated for a period of time, and then the excess liquid on the conductive carbonaceous support is removed and dried to obtain the catalyst precursor.

[0012] S4. The catalyst precursor is calcined under an inert gas to obtain a molybdenum-based monolithic catalyst.

[0013] Preferably, the pretreatment in step S1 specifically involves ultrasonically cleaning the conductive carbonaceous support in an ethanol-water solution, rinsing it with deionized water, and then drying it to obtain the pretreated conductive carbonaceous support; wherein the volume fraction of ethanol in the ethanol-water solution is 5% to 90%.

[0014] Preferably, the conductive carbonaceous carrier in step S1 is selected from one or a combination of graphite felt, carbon felt, and carbon cloth.

[0015] Preferably, the conductive carbonaceous carrier is a graphite felt, which has a three-dimensional cross-network structure and a porosity of 60% to 98%.

[0016] Preferably, the volume resistivity of the graphite felt is in the range of 0.02~0.16Ω·cm, and the tensile strength of the graphite felt is 0.10~0.15MPa.

[0017] Preferably, the molybdenum-based precursor in step S2 is selected from at least one of ammonium paramolybdate, ammonium tetramolybdate, ammonium orthomolybdate, and ammonium dimolybdate.

[0018] Preferably, the high molecular weight alcohol in step S2 includes polyvinyl alcohol.

[0019] Preferably, the impregnation solution system in step S2 is a mixture of a molybdenum-based precursor and a high molecular weight alcohol, wherein the mass ratio of the molybdenum-based precursor to the high molecular weight alcohol is 10 to 20.

[0020] Preferably, the ultrasonic impregnation time in step S3 is 0.1h to 100h.

[0021] Preferably, the drying conditions in step S3 are: drying in air or an inert atmosphere at 60~300℃ for 0.5h~100h.

[0022] Preferably, the inert gas in step S4 is selected from at least one of nitrogen, helium, neon, and argon.

[0023] Preferably, the calcination temperature in step S4 is 300℃~1000℃.

[0024] This invention provides a molybdenum-based monolithic catalyst, which is prepared by the above-described method for preparing a molybdenum-based monolithic catalyst. The molybdenum-based monolithic catalyst includes a conductive carbonaceous support and a molybdenum-based active component supported on the conductive carbonaceous support.

[0025] Preferably, the mass percentage of metallic molybdenum in the molybdenum-based active component is 0.1% to 80%.

[0026] In addition, the present invention also provides an application of the molybdenum-based monolithic catalyst as described above, which serves as both a catalyst and a heating element in the Joule thermal reverse water-gas shift reaction.

[0027] Preferably, the Joule thermal reverse water-gas shift reaction includes the following steps:

[0028] The molybdenum-based monolithic catalyst is loaded into the reactor, and an electric current is passed through it to generate Joule heat in the molybdenum-based monolithic catalyst, thereby heating the catalyst bed to the reaction temperature.

[0029] A feed gas containing H2 and CO2 is introduced into the reactor, and the feed gas enters the catalyst bed to undergo a shift reaction.

[0030] Preferably, before the conversion reaction begins, the process further includes an activation step for the molybdenum-based monolithic catalyst. Specifically, the activation involves heating the catalyst to 400-800°C and introducing a mixture of hydrogen and inert gas into the reactor to activate the molybdenum-based monolithic catalyst for 0-10 hours.

[0031] Preferably, in the mixture of hydrogen and inert gas, the concentration of hydrogen is 5% to 95%, wherein the inert gas is one or more of nitrogen, helium, neon, and argon.

[0032] Preferably, the molar ratio of H2 to CO2 in the raw gas is 0.1 to 10.

[0033] Preferably, the space velocity of the introduced raw material gas is 1000~3000000 mL·gcat. -1 ·h -1 .

[0034] Preferably, the reaction temperature is 200~1000℃.

[0035] As described above, the molybdenum-based monolithic catalyst, its preparation method, and its application of the present invention have the following beneficial effects:

[0036] The preparation method of this invention is simple, environmentally friendly, and operates under mild conditions. It employs a "modified impregnation solution" instead of the traditional "modified carrier" strategy. Polyvinyl alcohol (PVA) is added to the molybdenum-based precursor solution. As a surface-active polymer, PVA significantly improves the wettability of the impregnation solution on the hydrophobic conductive carbonaceous carrier, ensuring that the molybdenum-based precursor solution can penetrate deep into the carrier pores. Utilizing the steric hindrance effect of the PVA polymer chain, the hydrolysis and polymerization of molybdate ions are physically prevented, maintaining high stability in a low-polarity environment. This effectively avoids the hydrolysis and precipitation of the molybdenum-based precursor, ensuring the uniform distribution of the molybdenum-based active component on the conductive carbonaceous carrier. Furthermore, PVA can effectively adjust the viscosity and film formation of the impregnation solution. This further enhances the adhesion stability and mechanical strength of the catalyst within the three-dimensional network structure of the support. Furthermore, the conductive carbonaceous support serves as both a carbon source and a loading substrate. During calcination, the residual carbon from polyvinyl alcohol interacts with the conductive carbonaceous support as a carbon source, forming a molybdenum carbide shell at the interface with the molybdenum dioxide contact surface. This constructs a core-shell-like highly active catalytic structure of "MoO2 core-molybdenum carbide shell." The MoO2 core is primarily responsible for efficient CO2 adsorption and conversion, while the molybdenum carbide shell not only possesses excellent conductivity but also promotes H2 dissociation and protects the core from excessive reduction or loss. Using it as a catalyst and heating element in the reverse water-gas shift reaction can synergistically and significantly improve its catalytic activity and stability.

[0037] The molybdenum-based monolithic catalyst of this invention directly serves as a Joule heating element, utilizing the resistance of the conductive carbonaceous support itself to generate Joule heat. This significantly shortens the heat transfer distance, completely eliminates "cold spots" within the reactor, greatly reduces heat loss, and significantly improves energy utilization efficiency. Compared to particulate catalysts, this monolithic catalyst can slow down catalyst loss, improve the mechanical strength of the catalyst, and has a more stable electrical impedance, ensuring long-term operational reliability. This lays a solid foundation for the industrialization of Joule-heated monolithic catalysts driving thermocatalytic reactions. Attached Figure Description

[0038] Figure 1 The figure shows the change of CO2 conversion rate with reaction time in the reverse water-gas shift reaction of the molybdenum-based monolithic catalyst in Example 1 and Comparative Example 1 of the present invention, under two heating methods: internal Joule heating and external furnace heating.

[0039] Figure 2 The figure shows the change in CO2 conversion rate with reduction temperature of the molybdenum-based monolithic catalyst in the Joule thermal reverse water-gas shift reaction in Example 2 of the present invention.

[0040] Figure 3 The figure shows the change in CO2 conversion rate with reduction time in the Joule thermal reverse water-gas shift reaction of the molybdenum-based monolithic catalyst in Example 3 of the present invention.

[0041] Figure 4 The figure shows the change in CO2 conversion rate with reaction temperature of the molybdenum-based monolithic catalyst in the Joule thermal reverse water-gas shift reaction in Example 4 of the present invention.

[0042] Figure 5 The figure shows the change in CO2 conversion rate of the molybdenum-based monolithic catalyst in the Joule thermal reverse water-gas shift reaction over 40 hours in Example 5 of this invention.

[0043] Figure 6 The diagram shows the process flow for preparing the molybdenum-based monolithic catalyst of this invention.

[0044] Figure 7 The image shown is a SEM image of the molybdenum-based monolithic catalyst prepared in Example 1 of this invention. Detailed Implementation

[0045] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0046] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0047] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0048] See Figure 6 This invention provides a method for preparing a molybdenum-based monolithic catalyst, the method comprising the following steps:

[0049] S1. Provide a conductive carbonaceous carrier and perform pretreatment;

[0050] S2. The molybdenum-based precursor is mixed with a high molecular weight alcohol in water to form a stable impregnation solution system, wherein the high molecular weight alcohol is used to inhibit the hydrolysis and precipitation of molybdate ions.

[0051] S3. The pretreated conductive carbonaceous support is placed in the impregnation liquid system, ultrasonically impregnated for a period of time, and then the excess liquid on the conductive carbonaceous support is removed and dried to obtain the catalyst precursor.

[0052] S4. The catalyst precursor is calcined under an inert gas to obtain a molybdenum-based monolithic catalyst.

[0053] Specifically, this invention employs a "modified impregnation solution" instead of the traditional "modified carrier" strategy. A high-molecular-weight alcohol (polyvinyl alcohol) is added to the molybdenum-based precursor solution. As a surface-active polymer, polyvinyl alcohol significantly enhances the wettability of the impregnation solution on the hydrophobic conductive carbonaceous carrier, ensuring that the molybdenum-based precursor solution can penetrate deep into the carrier pores. Utilizing the steric hindrance effect of the polyvinyl alcohol's polymer chains, the hydrolysis and polymerization of molybdate ions are physically prevented, maintaining high stability in a low-polarity environment. This effectively avoids the hydrolysis and precipitation of the molybdenum-based precursor, ensuring the uniform distribution of the molybdenum-based active component on the conductive carbonaceous carrier. Furthermore, polyvinyl alcohol can effectively adjust the viscosity and composition of the impregnation solution. The membrane properties further enhance the adhesion stability and mechanical strength of the catalyst in the three-dimensional network structure of the support. In addition, the conductive carbonaceous support serves as both a carbon source and a loading substrate. During calcination, the carbon remaining from the polyvinyl alcohol and the conductive carbonaceous support work together as a carbon source, forming a molybdenum carbide shell at the interface with the molybdenum dioxide contact surface. This constructs a core-shell-like highly active catalytic structure of "MoO2 core-molybdenum carbide shell". The MoO2 core is mainly responsible for efficient CO2 adsorption and conversion, while the molybdenum carbide shell not only has excellent conductivity but also promotes H2 dissociation and protects the core from excessive reduction or loss. When used in the reverse water-gas shift reaction, it can synergistically and significantly improve its catalytic activity and stability.

[0054] As an example, the pretreatment in step S1 specifically involves placing the conductive carbonaceous support in an ethanol-water solution for ultrasonic cleaning, then rinsing it with deionized water and drying it to obtain the pretreated conductive carbonaceous support; wherein the volume fraction of ethanol in the ethanol-water solution is 5% to 90%.

[0055] Specifically, before ultrasonically cleaning the conductive carbonaceous carrier, the original conductive carbonaceous carrier is cut to a preset size specification. Then, the cut conductive carbonaceous carrier is placed in an ethanol-water solution for ultrasonic cleaning. The volume fraction of ethanol in the ethanol-water solution can be any value within the range of 5%, 10%, 20%, 40%, 60%, 80%, 90%, etc. Preferably, the volume fraction of ethanol in the ethanol-water solution is 50%.

[0056] Furthermore, no specific restrictions are placed on the frequency and time of ultrasonic cleaning, or the temperature and time of drying; the goal is simply to achieve preliminary cleaning of the conductive carbonaceous carrier.

[0057] As an example, the conductive carbonaceous support mentioned in step S1 is selected from one or a combination of graphite felt, carbon felt, and carbon cloth.

[0058] As an example, the conductive carbonaceous carrier is a graphite felt with a three-dimensional cross-network structure and a porosity of 60% to 98%.

[0059] Specifically, graphite felt is a product of carbon felt after high-temperature graphitization treatment, and its porosity can include any range of values ​​such as 60%, 70%, 80%, 90%, 95%, 98%; the maximum service temperature of graphite felt is not lower than 2000℃.

[0060] As an example, the volume resistivity of the graphite felt ranges from 0.02 to 0.16 Ω·cm, and the tensile strength of the graphite felt is from 0.10 to 0.15 MPa.

[0061] Specifically, the volume resistivity of graphite felt can range from 0.02 Ω·cm, 0.05 Ω·cm, 0.1 Ω·cm, 0.15 Ω·cm, 0.16 Ω·cm, etc., and the tensile strength of graphite felt can range from 0.1 MPa, 0.11 MPa, 0.12 MPa, 0.13 MPa, 0.14 MPa, 0.15 MPa, etc.; furthermore, the resistivity of the monofilament fiber of graphite felt is 1.0 × 10⁻⁶. -3 ~1.5×10 -3 Ω·cm (e.g., 1.0 × 10⁻⁶) -3 Ω·cm, 1.1×10 -3 Ω·cm, 1.2×10 -3 Ω·cm, 1.3×10 -3 Ω·cm, 1.4×10 -3 Ω·cm, 1.5×10 -3 (Values ​​within any range such as Ω·cm).

[0062] As an example, the molybdenum-based precursor in step S2 is selected from at least one of ammonium paramolybdate, ammonium tetramolybdate, ammonium orthomolybdate, and ammonium dimolybdate.

[0063] Specifically, the molecular formula of ammonium molybdate is (NH4)6Mo7O. 24 The molecular formula of ammonium tetramolybdate is (NH4)2Mo4O. 13 The molecular formula of ammonium molybdate is (NH4)2MoO4, and the molecular formula of ammonium dimolybdate is (NH4)2Mo2O7. These molybdates can be calcined in an oxygen-free environment to form molybdenum oxide.

[0064] As an example, the high molecular weight alcohols mentioned in step S2 include polyvinyl alcohol.

[0065] Specifically, the main function of polyvinyl alcohol (PVA) is to inhibit the hydrolysis and precipitation of molybdenum-based precursors and to assist in carbonization during subsequent calcination. PVA significantly improves the wettability of the impregnation solution on the hydrophobic conductive carbon support, ensuring that the molybdenum-based precursor solution can penetrate deep into the pores of the support. Utilizing the steric hindrance effect of the PVA polymer chain, it physically prevents the hydrolysis and polymerization of molybdate ions, maintaining high stability in a low-polarity environment, effectively avoiding the hydrolysis and precipitation of the molybdenum-based precursor, and ensuring the uniform distribution of the molybdenum-based active component on the conductive carbon support. In addition, as a surface-active polymer, PVA also plays a thickening and binding role in the specific embodiments of this invention, enabling the impregnation solution to be more firmly loaded on the support, further enhancing the adhesion stability of the catalyst in the three-dimensional network structure of the support.

[0066] As an example, the impregnation solution system in step S2 is a mixture of a molybdenum-based precursor and a high molecular weight alcohol, wherein the mass ratio of the molybdenum-based precursor to the high molecular weight alcohol is 10 to 20.

[0067] Specifically, the modified impregnation solution is made by mixing a high molecular weight alcohol with a molybdenum-based precursor in water. The mass ratio of the molybdenum-based precursor to the high molecular weight alcohol can be in the range of 10, 12, 14, 16, 18, 20, etc.

[0068] As an example, the ultrasonic immersion time in step S3 is 0.1h to 100h.

[0069] Specifically, the ultrasonic impregnation time can be any value within the range of 0.1h, 1h, 10h, 30h, 50h, 80h, 100h, etc., with the aim of uniformly impregnating the modified molybdenum-based precursor impregnation solution onto the conductive carbonaceous support; preferably, ultrasonic impregnation is performed for 4h.

[0070] In a specific embodiment of the present invention, after ultrasonic impregnation, the circular conductive carbonaceous carrier impregnated with the molybdenum-based precursor is placed on a spin coater and rotated at 100~20000 rpm (e.g., 100 rpm, 1000 rpm, 5000 rpm, 10000 rpm, 15000 rpm, 20000 rpm, etc.) for 5~1000 s (e.g., 5 s, 10 s, 100 s, 500 s, 800 s, 1000 s, etc.) to remove excess liquid from the conductive carbonaceous carrier; preferably, it is rotated at 1000 rpm for 10 s.

[0071] As an example, the drying conditions described in step S3 are drying in air or an inert atmosphere at 60~300°C for 0.5h~100h.

[0072] Specifically, the drying temperature in step S3 may include any value within the range of 60, 100, 150, 200, 250, 300, etc., and the drying atmosphere may be air or an inert atmosphere, wherein the inert atmosphere includes at least one of nitrogen, helium, neon, and argon.

[0073] As an example, the inert gas mentioned in step S4 is selected from at least one of nitrogen, helium, neon, and argon.

[0074] As an example, the calcination temperature in step S4 is 300℃~1000℃.

[0075] Specifically, calcination is carried out under an inert gas atmosphere, and the calcination temperature can be any value within the range of 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, etc.

[0076] This invention provides a molybdenum-based monolithic catalyst, which is prepared by the above-described method for preparing a molybdenum-based monolithic catalyst. The molybdenum-based monolithic catalyst includes a conductive carbonaceous support and a molybdenum-based active component supported on the conductive carbonaceous support.

[0077] As an example, the mass percentage of metallic molybdenum in the molybdenum-based active component is 0.1% to 80%.

[0078] Specifically, the molybdenum-based active component is uniformly loaded on a conductive carbonaceous support to achieve integrated conductivity and catalysis. The mass percentage of metallic molybdenum in the molybdenum-based active component can be any value within the range of 0.1%, 0.5%, 1%, 10%, 20%, 40%, 50%, 60%, 80%, etc. In a specific embodiment of the present invention, the molybdenum-based active component includes a MoO2 core and a molybdenum carbide shell, constructing a core-shell-like highly active catalytic structure of "MoO2 core-molybdenum carbide shell".

[0079] In addition to molybdenum oxide and molybdenum carbide, the molybdenum-based active components may also contain a very small amount of elemental molybdenum due to the excessive reduction of molybdenum oxide. Elemental molybdenum also acts as an active component, synergistically catalyzing with molybdenum oxide and molybdenum carbide. The synergistic catalytic effect of the multiphase system is far superior to that of a single active phase.

[0080] The present invention also provides an application of the molybdenum-based monolithic catalyst as described above, wherein the molybdenum-based monolithic catalyst is used simultaneously as a catalyst and a heating element in the Joule thermal reverse water-gas shift reaction.

[0081] Specifically, the molybdenum-based monolithic catalyst is directly used as a Joule heating element, utilizing the resistance of the conductive carbonaceous support itself to generate Joule heat, which greatly shortens the heat transfer distance, completely eliminates the "cold spots" in the reactor, significantly reduces heat loss, and significantly improves energy utilization efficiency. Compared with particulate catalysts, this monolithic catalyst can slow down the catalyst loss rate, improve the mechanical strength of the catalyst, and has a more stable electrical impedance, ensuring the reliability of long-term operation.

[0082] In specific embodiments of the present invention, the molybdenum-based monolithic catalyst can also be used in other endothermic gas-solid multiphase catalytic reactions, including one or a combination of steam methane reforming, dry methane reforming, alkane thermal cracking, NH3 decomposition, plastic conversion, and biomass conversion.

[0083] As an example, the Joule thermal reverse water-gas shift reaction includes the following steps:

[0084] The molybdenum-based monolithic catalyst is loaded into the reactor, and an electric current is passed through it to generate Joule heat in the molybdenum-based monolithic catalyst, thereby heating the catalyst bed to the reaction temperature.

[0085] A feed gas containing H2 and CO2 is introduced into the reactor, and the feed gas enters the catalyst bed to undergo a shift reaction.

[0086] Specifically, a molybdenum-based monolithic catalyst is packed into the reaction tube of the reactor and pressed between the upper and lower electrodes to maintain good contact. The power is turned on, and the current is conducted to generate Joule heat in the molybdenum-based monolithic catalyst. Subsequently, the temperature of the catalyst bed containing the molybdenum-based monolithic catalyst rises. When it rises to the reaction temperature, the feed gas is introduced into the reaction tube. The feed gas comes into contact with the molybdenum-based monolithic catalyst and undergoes a transformation reaction under its catalytic action.

[0087] As an example, before the conversion reaction begins, the process includes activating the molybdenum-based monolithic catalyst. Specifically, the activation involves heating the catalyst to 400-800°C and introducing a mixture of hydrogen and inert gas into the reactor to activate the molybdenum-based monolithic catalyst for 0-10 hours.

[0088] Specifically, the activation temperature can be any value within the range of 400℃, 500℃, 600℃, 700℃, 800℃, etc., and the activation time can be any value within the range of 0, 0.1h, 1h, 3h, 5h, 7h, 9h, 10h, etc. When the activation time is 0, it means that no activation step is required, and the molybdenum-based monolithic catalyst can be directly subjected to the reverse water-gas shift reaction.

[0089] In a specific embodiment of the present invention, the polymeric alcohol (polyvinyl alcohol) plays not only the role of "inhibiting precipitation and assisting carbonization" in the preparation of the monolithic catalyst, but also, as a surface-active polymer, thickens and binds the catalyst. By adjusting the viscosity and film-forming properties of the impregnation solution, the adhesion stability of the impregnation solution in the three-dimensional network structure is further enhanced, enabling the impregnation solution to be more firmly loaded on the conductive carbon support. During the calcination process in step S4, residual carbon is generated after the polyvinyl alcohol is calcined, providing a carbon source for the subsequent activation of the molybdenum-based monolithic catalyst and the formation of the core-shell catalyst, which helps to further improve its catalytic performance. The activation treatment is mainly used to adjust the amount of oxygen vacancies and the ratio of molybdenum oxide to molybdenum carbide in the molybdenum-based monolithic catalyst, which can further improve its catalytic performance.

[0090] As an example, in a mixture of hydrogen and an inert gas, the concentration of hydrogen is 5% to 95%, wherein the inert gas is one or more of nitrogen, helium, neon, and argon.

[0091] Specifically, in a mixture of hydrogen and inert gases, the concentration of hydrogen is the volume fraction of hydrogen, which can include any value within a range such as 5%, 10%, 20%, 50%, 70%, 90%, 95%, etc.

[0092] As an example, the molar ratio of H2 to CO2 in the feed gas is 0.1 to 10.

[0093] Specifically, the feed gas in the reverse water gas shift reaction is H2 and CO2, and the molar ratio between the two can be any value in any range, such as 0.1, 0.5, 1, 3, 5, 7, 9, 10, etc.

[0094] As an example, the space velocity of the introduced raw material gas is 1000~3000000 mL·gcat. -1 ·h -1 .

[0095] Specifically, the space velocity of the feed gas introduced into the reactor may include 1000 mL·gcat. -1 ·h -1 10000mL·gcat -1 ·h -1 100000mL·gcat-1 ·h -1 1,000,000 mL gcat -1 ·h -1 2,000,000 mL gcat -1 ·h -1 3,000,000 mL gcat -1 ·h -1 Values ​​within any range.

[0096] As an example, the reaction temperature is 200~1000℃.

[0097] Specifically, the reaction temperature can be any value within a range such as 200℃, 300℃, 500℃, 700℃, 900℃, 1000℃, etc., and can be adjusted according to the actual situation.

[0098] In addition, the reaction pressure of the conversion reaction is 1~30 bar, which may include any value in the range of 1 bar, 3 bar, 5 bar, 10 bar, 15 bar, 20 bar, 25 bar, 30 bar, etc.; in a specific embodiment of the present invention, the conversion reaction is carried out at atmospheric pressure.

[0099] To better understand the molybdenum-based monolithic catalyst, its preparation method, and its application in this invention, specific embodiments are described below. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way.

[0100] The graphite felt used in Examples 1 to 5 below has a porosity of 94.1%, a volume resistivity of 0.02 Ω·cm, and a tensile strength of 0.14 MPa.

[0101] Example 1

[0102] This embodiment provides a method for preparing a molybdenum-based monolithic catalyst, including the following steps:

[0103] S1. Provide graphite felt, use a punch to cut it into a preset diameter of 8mm and thickness of 3mm, and ultrasonically clean the cut graphite felt disc with ethanol-water solution (ethanol volume fraction is 50%) for 10 minutes, then rinse with deionized water 5 times, and finally put the cleaned graphite felt into a drying oven to dry completely.

[0104] S2, Weigh 3.681g of ammonium molybdate ((NH4)6Mo7O 24 Pour 4H2O into a 50mL centrifuge tube, add an appropriate amount of deionized water until just dissolved (about 13.75mL), add 0.250g of polyvinyl alcohol to form a colorless, transparent and stable impregnation solution system;

[0105] S3. Place the 10 graphite felt discs pretreated in step S1 into the impregnation system and ultrasonically impregnate for 4 hours so that the graphite felt can be directly and uniformly impregnated with ammonium molybdate. Use a spin coater to centrifuge each graphite felt at 1000 rpm for 10 seconds to remove excess impregnation liquid. Then place it in a 120℃ oven to dry completely to obtain the catalyst precursor.

[0106] S4. The catalyst precursor is placed in a tube furnace and calcined at 600°C in a nitrogen atmosphere for 2 hours to completely decompose the catalyst precursor and obtain a molybdenum-based monolithic catalyst.

[0107] The mass of a single graphite felt disc before impregnation was 20 mg, and the mass of a single graphite felt disc after impregnation was 55 mg. It was calculated that the mass of the molybdenum-based active component loaded on a single graphite felt disc was 35 mg. The molybdenum-based active component may contain MoO2, molybdenum carbide, or elemental molybdenum. Since the content of molybdenum carbide and elemental molybdenum is very low, it can be calculated that the molybdenum-based active component is entirely MoO2. The mass percentage of metallic molybdenum in the molybdenum-based active component is approximately 47.7%.

[0108] See Figure 7 The image shows an SEM image (scale bar 10 μm) of the molybdenum-based monolithic catalyst prepared in this embodiment. As can be seen from the image, the graphite felt fibers are cylindrical with a relatively smooth surface. Molybdenum-based active particles are uniformly attached to the fiber surface, indicating that the molybdenum-based active components in the molybdenum-based monolithic catalyst prepared in this embodiment are attached to the fiber surface as an extremely thin and continuous coating. In the molybdenum-based monolithic catalyst prepared in this embodiment, the molybdenum-based active components achieve a dual uniform distribution at both the three-dimensional network level and the particle level on the graphite felt support. This uniformity is due to the improved wetting of the hydrophobic support by the polyvinyl alcohol modified impregnation solution, the inhibition of hydrolysis of the molybdenum-based precursor, and the fixing effect of residual carbon from polyvinyl alcohol on the distribution of active components during calcination.

[0109] This embodiment also provides an application of a molybdenum-based monolithic catalyst, in which the molybdenum-based monolithic catalyst prepared in this embodiment is used simultaneously as a catalyst and a heating element in a Joule heat reverse water-gas shift reaction, specifically including the following steps:

[0110] A1. Assembly of the Joule thermal reactor: A molybdenum-based monolithic catalyst is packed into the middle of a quartz reaction tube with an outer diameter of 10 mm, a wall thickness of 1 mm, and a length of 400 mm, serving as the heating element. A 2 mm diameter hole (negligible mass loss) is drilled in the center of the graphite felt. Hollow 316L stainless steel rods with an outer diameter of 4 mm and a wall thickness of 1 mm (upper rod length 308 mm, lower rod length 287 mm) are inserted into the upper and lower ends respectively. The bottom of the stainless steel hollow rod is a hollow cylindrical disk (made of 310 stainless steel, outer diameter 7.75 mm, inner diameter 2 mm, communicating with the interior of the stainless steel hollow rod, thickness 2.65 mm). The molybdenum-based monolithic catalyst is compacted. Then, the stainless steel hollow rod is connected to the power supply via wires, ensuring a tight connection to form a passage. K-type thermocouples and sheaths are inserted above and below the catalyst bed through the holes in the stainless steel hollow rod for temperature control and measurement, completing the assembly of the Joule thermal reactor.

[0111] A2. Set the heating program, turn on the heating power supply, and conduct the current to generate Joule heat in the molybdenum-based monolithic catalyst, heating the catalyst bed to 600℃ (during the heating stage, only 50mL / min of N2 is introduced, the heating program is to heat from room temperature to 200℃ at a heating rate of 18℃ / min, then hold at 200℃ for 10min to confirm the stability of temperature control, and then heat to 600℃ at a heating rate of 40℃ / min), and then introduce H2 for reduction for 5h;

[0112] A3. After reduction, a mixture of raw material gas and N2 is introduced into the reactor. The composition of the mixture is CO2 / H2 / N2 = 24 / 72 / 4 mL·min. -1 The feed gas enters the catalyst bed and undergoes a shift reaction at 600℃ under normal pressure for 4 hours. Simultaneously, the gas is analyzed every 15 minutes using a gas analyzer. The test results are shown below. Figure 1 The change of CO2 conversion rate with reaction time under internal Joule heating.

[0113] Comparative Example 1

[0114] This comparative example provides an application of a molybdenum-based monolithic catalyst. The molybdenum-based monolithic catalyst prepared in Example 1 is used as both a catalyst and a heating element in a Joule thermal reverse water-gas shift reaction. The specific steps differ from those in Example 1 in that: in step A1, there is no need to connect to the power source via wires, nor is it necessary to insert a K-type thermocouple and sheath; the heating program in step A2 is completed using a conventional external heating furnace; other methods and steps are the same as in Example 1, and will not be repeated here.

[0115] The gas analyzer was used to analyze the gas every 15 minutes. The test results are shown below. Figure 1 See Figure 1The molybdenum-based monolithic catalysts used in Example 1 and Comparative Example 1 were used in a reverse water-gas shift reaction at a catalyst bed temperature of 600°C, atmospheric pressure, and H2 / CO2 / N2 ratios of 72 / 24 / 4 mL·min. -1 The CO2 conversion rate varied with reaction time during the 4-hour reaction process under two heating methods: internal Joule heating and external furnace heating. Table 1 shows the test data for the catalyst bed being heated to 600°C for the conversion reaction in Example 1 and Comparative Example 1, using internal Joule heating and external furnace heating respectively.

[0116] Table 1 shows the test results of the molybdenum-based monolithic catalysts in Example 1 and Comparative Example 1 in the counter-water gas shift reaction under two heating methods: internal Joule heating and external furnace heating.

[0117]

[0118] The average temperature at the center in Table 1 refers to the average temperature of the part of the quartz reaction tube filled with the molybdenum-based monolithic catalyst, the average temperature at the bottom refers to the average temperature at the bottom of the reaction tube, and the average temperature at the outer wall refers to the average temperature at the outer wall of the reaction tube; according to Figure 1 As shown in Table 1, the molybdenum-based monolithic catalyst prepared in Example 1 successfully catalyzed the reverse water-gas shift reaction. Compared with the external heating method in Comparative Example 1, it has a significant energy-saving advantage, saving about 30% of energy. Moreover, the average conversion rates of H2 and CO2 under the internal Joule heating method in Example 1 are close to those under the external heating method.

[0119] Example 2

[0120] This embodiment provides a method for preparing a molybdenum-based monolithic catalyst, which is the same as that in Example 1 and will not be described again here.

[0121] This embodiment provides an application of a molybdenum-based monolithic catalyst. The molybdenum-based monolithic catalyst prepared in this embodiment is used as both a catalyst and a heating element in a Joule thermal reverse water-gas shift reaction. The degree of carbonization of the molybdenum-based monolithic catalyst is controlled by adjusting different reduction temperatures.

[0122] The specific steps differ from those in Example 1 in that: in step A2, a heating program is set, the heating power supply is turned on, and the current is conducted to generate Joule heat in the molybdenum-based monolithic catalyst, heating the catalyst bed to 400℃, 500℃, 600℃, 700℃, and 800℃ respectively (during the heating stage, only 50 mL / min of N2 is introduced; the heating program starts from room temperature and increases to 200℃ at a rate of 18℃ / min, then holds at 200℃ for 10 minutes to confirm the stability of the temperature control, and then increases at 40℃ / min). The temperature was increased to 400℃, 500℃, 600℃, 700℃, and 800℃ at a heating rate of ℃ / min, respectively. Temperatures of 700℃ and 800℃ were achieved in a conventional tubular furnace, followed by reduction with H2 for 5 hours. In step A3, after reduction, the catalyst bed temperature was adjusted to 600℃ at a rate of 10℃ / min, and a mixture of feed gas and N2 was introduced into the reactor. The mixture composition was CO2 / H2 / N2 = 24 / 72 / 4 mL·min. -1 The feed gas enters the catalyst bed and undergoes a shift reaction at 600°C for 4 hours. At the same time, the gas is analyzed every 15 minutes using a gas analyzer. Other methods and steps are the same as in Example 1 and will not be repeated here.

[0123] The gas analyzer was used to analyze the gas every 15 minutes. The test results are shown below. Figure 2 See Figure 2 The molybdenum-based monolithic catalyst in Example 2 was activated in a Joule thermal reverse water-gas shift reaction at different reduction temperatures (400℃, 500℃, 600℃, 700℃, 800℃). Then, at 600℃, atmospheric pressure, and H2 / CO2 / N2 = 72 / 24 / 4 mL·min... -1 The average CO2 conversion rate under the evaluation conditions is shown in the figure.

[0124] The molybdenum-based monolithic catalyst was activated at reduction temperatures of 400℃, 500℃, 600℃, 700℃ and 800℃, respectively. Its performance was then tested under the evaluation conditions of 600℃, atmospheric pressure and H2 / CO2 / N2 volume flow ratio of 72 / 24 / 4 mL·min⁻¹. Table 2 shows the test results of the molybdenum-based monolithic catalyst in the Joule thermal reverse water-gas shift reaction in Example 2.

[0125] Table 2. Test results of the molybdenum-based monolithic catalyst in the Joule thermal reverse water-gas shift reaction in Example 2

[0126]

[0127] according to Figure 2As shown in Table 2, the optimal reduction temperature for the molybdenum-based monolithic catalyst prepared in Example 2 is 600℃. Reduction at 600℃ for 5 hours activates the molybdenum-based monolithic catalyst. At this temperature, the ratio of molybdenum oxide to molybdenum carbide is relatively suitable. As the reduction temperature increases, more molybdenum oxide is carbonized into molybdenum carbide, which will reduce the conversion rates of H2 and CO2.

[0128] Example 3

[0129] This embodiment provides a method for preparing a molybdenum-based monolithic catalyst, which is the same as that in Example 1 and will not be described again here.

[0130] This embodiment provides an application of a molybdenum-based monolithic catalyst. The molybdenum-based monolithic catalyst prepared in this embodiment is used as both a catalyst and a heating element in a Joule thermal reverse water-gas shift reaction. The main method is to control the number of oxygen vacancies in the molybdenum-based monolithic catalyst by adjusting different reduction times.

[0131] The specific steps differ from those in Example 1 in that: in step A2, a heating program is set, the heating power supply is turned on, and the current is conducted to generate Joule heat in the molybdenum-based monolithic catalyst, heating the catalyst bed to 600°C (during the heating stage, only 50 mL / min of N2 is introduced, and the heating program is to heat from room temperature to 200°C at a heating rate of 18°C / min, then hold at 200°C for 10 min to confirm the stability of temperature control, and then heat to 600°C at a heating rate of 40°C / min). Then H2 is introduced, and reduction is carried out for 0.5 h, 1 h, 2 h, 5 h, and 7 h respectively. Other methods and steps are the same as those in Example 1, and will not be repeated here.

[0132] During the shift reaction in step A3, the gas analyzer was used to analyze the reaction every 15 minutes. The test results are shown below. Figure 3 See Figure 3 The molybdenum-based monolithic catalyst in Example 3 was activated in a Joule thermal reverse water-gas shift reaction by different reduction times (0.5h, 1h, 2h, 5h, 7h) and then subjected to a reaction at 600℃, atmospheric pressure, and H2 / CO2 / N2 = 72 / 24 / 4 mL·min. -1 The average CO2 conversion rate under the evaluation conditions is shown in the figure.

[0133] The molybdenum-based monolithic catalyst was reduced at 600℃ for 0.5h, 1h, 2h, 5h and 7h respectively. Its performance was then tested under the evaluation conditions of 600℃, atmospheric pressure and H2 / CO2 / N2 volume flow rate ratio of 72 / 24 / 4 mL·min⁻¹. Table 3 shows the test results of the molybdenum-based monolithic catalyst in the Joule thermal reverse water-gas shift reaction in Example 3.

[0134] Table 3. Test results of the molybdenum-based monolithic catalyst in the Joule thermal reverse water-gas shift reaction in Example 3.

[0135]

[0136] according to Figure 3 As shown in Table 3, the optimal reduction time for the molybdenum-based monolithic catalyst prepared in Example 3 at 600°C is 5 hours, at which point the number of oxygen vacancies in the molybdenum-based active component is most suitable.

[0137] Example 4

[0138] This embodiment provides a method for preparing a molybdenum-based monolithic catalyst, which is the same as that in Example 1 and will not be described again here.

[0139] This embodiment provides an application of a molybdenum-based monolithic catalyst. The molybdenum-based monolithic catalyst prepared in this embodiment is used simultaneously as a catalyst and a heating element in a Joule thermal reverse water-gas shift reaction. The specific steps differ from those in Embodiment 1 in that: after reduction in step A3, the temperature is naturally cooled to the specified reaction temperature (300℃, 400℃, 500℃, 600℃), and a mixture of feed gas and N2 is introduced into the reactor. The composition of the mixture is CO2 / H2 / N2 = 24 / 72 / 4 mL·min. -1 The raw material gas enters the catalyst bed and undergoes a shift reaction at a specified reaction temperature for 4 hours. At the same time, the gas is analyzed every 15 minutes using a gas analyzer.

[0140] See Figure 4 The molybdenum-based monolithic catalyst in Example 4 was used in a Joule thermal reverse water-gas shift reaction at different reaction temperatures (300℃, 400℃, 500℃, 600℃) under normal pressure and with H2 / CO2 / N2 = 72 / 24 / 4 mL·min. -1 The average CO2 conversion rate under the evaluation conditions is shown in the figure.

[0141] This molybdenum-based monolithic catalyst, under different reaction temperatures (300℃, 400℃, 500℃, 600℃) and at atmospheric pressure, with H2 / CO2 / N2 = 72 / 24 / 4 mL·min, showed promising results. -1 Performance tests were conducted under the evaluation condition of 4 hours of conversion reaction. See Table 4 for the test results of the molybdenum-based monolithic catalyst in the Joule thermal reverse water gas conversion reaction in Example 4.

[0142] Table 4. Test results of molybdenum-based monolithic catalyst in Joule thermal reverse water-gas shift reaction in Example 4

[0143]

[0144] In Table 4, heating power refers to the electrical power applied directly to the molybdenum-based monolithic catalyst; bed resistance refers to the total resistance encountered when current flows into the reactor from one end electrode, through the compressed molybdenum-based monolithic catalyst bed, and out from the other end electrode; center average temperature refers to the average temperature of the part of the quartz reaction tube filled with molybdenum-based monolithic catalyst; bottom average temperature refers to the average temperature of the bottom of the reaction tube; and outer wall average temperature refers to the average temperature of the outer wall of the reaction tube.

[0145] according to Figure 4 As shown in Table 4, the molybdenum-based monolithic catalyst in Example 4 exhibits stable and accurate temperature control within the reaction temperature range of 300℃, 400℃, 500℃, and 600℃. The CO2 conversion rate and heating power are positively correlated with the reaction temperature, while the bed resistance is negatively correlated with the reaction temperature.

[0146] Example 5

[0147] This embodiment provides a method for preparing a molybdenum-based monolithic catalyst, which is the same as that in Example 1 and will not be described again here.

[0148] This embodiment provides an application of a molybdenum-based monolithic catalyst. The molybdenum-based monolithic catalyst prepared in this embodiment is used as both a catalyst and a heating element in a Joule thermal reverse water-gas shift reaction. The specific steps differ from those in Embodiment 1 in that: in step A3, the shift reaction occurs at 600°C for 40 hours, and a gas analyzer is used to analyze the gas every hour. Other methods and steps are the same as in Embodiment 1 and will not be repeated here.

[0149] See Figure 5 The figure shows the change in CO2 conversion rate of the molybdenum-based monolithic catalyst in the Joule thermal reverse water-gas shift reaction within 40 hours in Example 5. As can be seen from the figure, the catalytic performance of the molybdenum-based monolithic catalyst in this example is stable within 40 hours.

[0150] In summary, the preparation method of this invention is simple to operate, environmentally friendly, and operates under mild conditions. It employs a "modified impregnation solution" instead of the traditional "modified carrier" strategy. Polyvinyl alcohol (PVA) is added to the molybdenum-based precursor solution. As a surface-active polymer, PVA significantly improves the wettability of the impregnation solution on the hydrophobic conductive carbonaceous carrier, ensuring that the molybdenum-based precursor solution can penetrate deep into the carrier pores. Utilizing the steric hindrance effect of the PVA polymer chain, the hydrolysis and polymerization of molybdate ions are physically prevented, maintaining high stability in a low-polarity environment. This effectively avoids the hydrolysis and precipitation of the molybdenum-based precursor, ensuring the uniform distribution of the molybdenum-based active component on the conductive carbonaceous carrier. Furthermore, PVA can effectively adjust the viscosity of the impregnation solution and... The film-forming properties further enhance the adhesion stability and mechanical strength of the catalyst in the three-dimensional network structure of the support. In addition, the conductive carbonaceous support serves as both a carbon source and a loading substrate. During calcination, the carbon remaining from polyvinyl alcohol and the conductive carbonaceous support work together as a carbon source, forming a molybdenum carbide shell at the interface with the molybdenum dioxide contact surface. This constructs a core-shell-like highly active catalytic structure of "MoO2 core-molybdenum carbide shell". The MoO2 core is mainly responsible for efficient CO2 adsorption and conversion, while the molybdenum carbide shell not only has excellent conductivity but also promotes H2 dissociation and protects the core from excessive reduction or loss. When used as a catalyst and heating element in the reverse water-gas shift reaction, it can synergistically and significantly improve its catalytic activity and stability. The molybdenum-based monolithic catalyst in this invention directly serves as a Joule heating element, utilizing the resistance of the conductive carbonaceous support to generate Joule heat. This significantly shortens the heat transfer distance, completely eliminates "cold spots" within the reactor, drastically reduces heat loss, and significantly improves energy utilization efficiency. Compared to particulate catalysts, this monolithic catalyst slows down catalyst loss, improves the catalyst's mechanical strength, and possesses more stable electrical impedance, ensuring long-term operational reliability. This lays a solid foundation for the industrialization of Joule-heated monolithic catalyst-driven thermocatalytic reactions. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0151] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a molybdenum-based monolithic catalyst, characterized in that, The preparation method includes the following steps: S1. Provide a conductive carbonaceous carrier and perform pretreatment; S2. The molybdenum-based precursor is mixed with a high molecular weight alcohol in water to form a stable impregnation solution system, wherein the high molecular weight alcohol is used to inhibit the hydrolysis and precipitation of molybdate ions. S3. The pretreated conductive carbonaceous support is placed in the impregnation liquid system, ultrasonically impregnated for a period of time, and then the excess liquid on the conductive carbonaceous support is removed and dried to obtain the catalyst precursor. S4. The catalyst precursor is calcined under an inert gas to obtain a molybdenum-based monolithic catalyst.

2. The method for preparing the molybdenum-based monolithic catalyst according to claim 1, characterized in that: The pretreatment in step S1 specifically involves ultrasonically cleaning the conductive carbonaceous support in an ethanol-water solution, rinsing it with deionized water, and then drying it to obtain the pretreated conductive carbonaceous support; wherein the volume fraction of ethanol in the ethanol-water solution is 5% to 90%.

3. The method for preparing the molybdenum-based monolithic catalyst according to claim 1, characterized in that: The conductive carbonaceous carrier mentioned in step S1 is selected from one or a combination of graphite felt, carbon felt, and carbon cloth.

4. The method for preparing the molybdenum-based monolithic catalyst according to claim 3, characterized in that: The conductive carbonaceous carrier is graphite felt, which has a three-dimensional cross-network structure and a porosity of 60% to 98%.

5. The method for preparing the molybdenum-based monolithic catalyst according to claim 4, characterized in that: The graphite felt has a volume resistivity ranging from 0.02 to 0.16 Ω·cm and a tensile strength ranging from 0.10 to 0.15 MPa.

6. The method for preparing the molybdenum-based monolithic catalyst according to claim 1, characterized in that: Step S2 includes one or a combination of the following conditions: The molybdenum-based precursor is selected from at least one of ammonium paramolybdate, ammonium tetramolybdate, ammonium orthomolybdate, and ammonium dimolybdate. The high molecular weight alcohols include polyvinyl alcohol; The impregnation solution system is a mixture of a molybdenum-based precursor and a high molecular weight alcohol, wherein the mass ratio of the molybdenum-based precursor to the high molecular weight alcohol is 10 to 20.

7. The method for preparing the molybdenum-based monolithic catalyst according to claim 1, characterized in that: Step S3 includes one or a combination of the following conditions: The ultrasonic impregnation time is 0.1h to 100h; The drying conditions are as follows: drying in air or an inert atmosphere at 60~300℃ for 0.5h~100h.

8. The method for preparing the molybdenum-based monolithic catalyst according to claim 1, characterized in that: Step S4 includes one or a combination of the following conditions: The inert gas is selected from at least one of nitrogen, helium, neon, and argon; The calcination temperature is 300℃~1000℃.

9. A molybdenum-based monolithic catalyst, characterized in that: The molybdenum-based monolithic catalyst is prepared by any one of the preparation methods of claims 1 to 8, wherein the molybdenum-based monolithic catalyst comprises a conductive carbonaceous support and a molybdenum-based active component supported on the conductive carbonaceous support.

10. The molybdenum-based monolithic catalyst according to claim 9, characterized in that: The molybdenum-based active component contains 0.1% to 80% molybdenum by mass.

11. The application of a molybdenum-based monolithic catalyst as described in claim 9 or 10, characterized in that: The molybdenum-based monolithic catalyst is used as both a catalyst and a heating element in the Joule thermal reverse water-gas shift reaction.

12. The application of the molybdenum-based monolithic catalyst according to claim 11, characterized in that: The Joule thermal reverse water-gas shift reaction includes the following steps: The molybdenum-based monolithic catalyst is loaded into the reactor, and an electric current is passed through it to generate Joule heat in the molybdenum-based monolithic catalyst, thereby heating the catalyst bed to the reaction temperature. A feed gas containing H2 and CO2 is introduced into the reactor, and the feed gas enters the catalyst bed to undergo a shift reaction.

13. The application of the molybdenum-based monolithic catalyst according to claim 12, characterized in that: Before the conversion reaction begins, the process includes an activation step for the molybdenum-based monolithic catalyst. Specifically, the activation involves heating the catalyst to 400-800°C and introducing a mixture of hydrogen and inert gas into the reactor for 0-10 hours.

14. The application of the molybdenum-based monolithic catalyst according to claim 13, characterized in that: In the mixture of hydrogen and inert gas, the concentration of hydrogen is 5% to 95%, wherein the inert gas is one or more of nitrogen, helium, neon, and argon.

15. The application of the molybdenum-based monolithic catalyst according to claim 12, characterized in that: Includes one or a combination of the following conditions: The molar ratio of H2 to CO2 in the raw gas is 0.1 to 10; The space velocity of the feed gas is 1000~3000000 mL·gcat. -1 ·h -1 ; The reaction temperature is 200~1000℃.

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