Endogenous Joule heat catalyst for methane dry reforming as well as preparation method and application of endogenous Joule heat catalyst

Abstract

The invention discloses an endogenous Joule heat catalyst for methane dry reforming and a preparation method and application thereof, the endogenous Joule heat catalyst comprises a titanium black carrier and an active metal loaded on the titanium black carrier, the titanium black carrier is selected from at least one of Ti4O7, Ti5O9, Ti6O11, Ti7O13, Ti8O15 and Ti9O17, and the active metal is selected from at least one of Ti4O7, Ti5O9, Ti6O11, Ti7O13, Ti8O15 and Ti9O17. The active metal is at least one of nickel, cobalt, rhodium, ruthenium, palladium, platinum and iridium, and the endogenous Joule heat catalyst has an electro-thermal characteristic. Titanium oxide is used as a carrier, a conductive TiO layer exists in crystal lattices of the titanium oxide and has conductivity, CO2 can be directly activated by the conductive TiO layer containing a large number of oxygen vacancies, CH4 can be efficiently activated by the loaded active metal, the titanium oxide and the loaded active metal jointly form a bifunctional catalytic activity system, and the catalyst can be self-heated through endogenous Joule heat due to the electro-thermal characteristic; energy loss caused by indirect heat transfer of an electrothermal material in the prior art is avoided, current can directly flow through the catalyst, and the reaction performance is effectively improved by coupling the endogenous Joule heating effect and the electronic effect.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, and in particular to an endogenous Joule thermal catalyst for methane dry reforming, its preparation method, and its application. Background Technology

[0002] With the global energy structure transformation and increasing environmental awareness, methane dry reforming technology, as an important pathway to achieve the co-conversion of methane and carbon dioxide, has gradually become a research hotspot in the energy and environmental fields. The methane dry reforming reaction (CH4 + CO2 → 2CO + 2H2) converts methane and carbon dioxide into high-value-added syngas (CO and H2), simultaneously reducing emissions of these two greenhouse gases. The resulting syngas can be further processed into basic chemical raw materials and high-value chemicals. This technology not only has significant low-carbon effects but also performs well in terms of product market capacity, raw material substitution for emission reduction, comprehensive emission reduction, and cost-effectiveness. However, the methane dry reforming reaction is a strongly endothermic reaction, typically requiring high temperatures (usually above 800℃). To maintain this high-temperature reaction and achieve effective heat transfer, large amounts of fossil fuels often need to be burned, which to some extent weakens the carbon emission reduction effect.

[0003] Recently, electrothermal coupling catalysis technology has become an important technological development direction for realizing dry reforming of methane. For example, patent document CN116514062A discloses a method for Joule thermal coupling catalysis of natural gas and CO2 dry gas to produce syngas. A metal tube is used as the electrothermal material, coated with an active component, and assembled into a metal catalytic reactor. The active component is heated by the resistance heating of the metal reactor, driving the dry reforming reaction of methane. Patent document CN116902917A discloses an electrification method for catalytic dry reforming and a system applying this method. The active component is loaded onto a carbon material or a semiconductor material such as antimony-doped tin oxide, and the electrothermal coupling effect of the carrier drives the dry reforming reaction of methane. However, existing electrothermal coupled catalytic dry reforming technology for methane faces some technical challenges: On the one hand, the current mainly flows through the inside of the electrothermal material, heating the active component by transferring Joule heat, but the active component itself does not generate Joule heat and cannot exert the current-induced electronic effect, thus having limited improvement on the reaction performance of methane dry reforming; on the other hand, the electrothermal materials are mostly metal materials, carbon materials, or carbon-containing materials, which are easily oxidized by carbon dioxide under electrothermal conditions, while antimony-doped tin oxide and other semiconductor materials are easily over-reduced by methane, causing irreversible loss, resulting in the instability and poor durability of the electrothermal coupled catalyst in the dry reforming reaction. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to develop a novel catalyst for methane dry reforming, and to solve the problems of limited performance improvement and catalyst instability in electrothermal coupled catalytic dry reforming.

[0005] To address the aforementioned technical problems, the first aspect of this invention provides an endogenous Joule thermal catalyst, comprising a titanium suboxide support and an active metal supported on the titanium suboxide support, wherein the titanium suboxide support is selected from Ti4O7, Ti5O9, and Ti6O7. 11 Ti7O 13 Ti8O 15 Ti9O 17 At least one of the following, wherein the active metal is at least one of nickel, cobalt, rhodium, ruthenium, palladium, platinum, and iridium, and the endogenous Joule thermal catalyst has electrothermal properties.

[0006] This invention uses titanium suboxide as a carrier, whose lattice contains a conductive TiO layer that provides conductivity and a large number of oxygen vacancies that can directly activate CO2. The supported active metal can efficiently activate CH4, and together they constitute a bifunctional catalytic active system. This system allows current to flow directly through the entire catalyst, and its electrothermal properties enable it to self-heat through endogenous Joule heating, avoiding the energy loss caused by indirect heat transfer in traditional electrothermal materials. Simultaneously, the current induces electronic effects in the catalyst, particularly the electrically driven lattice oxygen migration effect, which accelerates the migration of O from CO2 dissociation to the active metal, enhancing the oxidation and decomposition of CH4 dissociation products. The coupling effect between the endogenous Joule heating effect and the electronic effect effectively improves the reaction performance.

[0007] In some preferred or optional embodiments, a strong interaction exists between the titanium suboxide support and the active metal. On the one hand, this strong interaction can significantly promote the migration of reactive oxygen species and electrons between the titanium suboxide and the active metal, accelerate the transfer of O from CO2 dissociation on the titanium suboxide to the surface of the active metal, and rapidly react with CH4 dissociation products to generate CO, thereby enhancing reaction kinetics and improving the reactivity and selectivity of methane dry reforming. On the other hand, the strong interaction can stably anchor the active metal particles on the surface of the titanium suboxide, inhibiting their agglomeration and sintering during the reaction, thus maintaining the stability and durability of the catalyst during the reaction.

[0008] In some preferred or optional embodiments, the loading of the active metal is 0.02% to 15% based on the total mass of the endogenous Joule thermal catalyst. This loading range ensures that a sufficient amount of active metal participates in the reaction; at the same time, it prevents the active metal from agglomerating into large-diameter particles due to excessive loading, thus avoiding a decrease in the density of active sites and damage to catalytic activity.

[0009] In some preferred or optional embodiments, the particle size of the active metal is no greater than 100 nm. Small-diameter metal particles have a higher specific surface area, which can significantly increase the density of active sites for CH4 activation and improve the CH4 dissociation rate; at the same time, the contact interface between small-diameter metal particles and the titanium suboxide support is larger, making it easier to form strong interactions, further promoting the migration of reactive oxygen species and electron transfer.

[0010] In some preferred or optional embodiments, the macroscopic particle size of the endogenous Joule thermal catalyst is 10-300 mesh. This particle size effectively eliminates the limitation of gas diffusion in the reaction, allowing the CH4 and CO2 mixture to quickly penetrate to the active sites inside the particles; on the other hand, it prevents excessive gas resistance in the catalytic reaction caused by excessively small particles.

[0011] In some preferred or optional embodiments, the endogenous Joule heating catalyst has an electrical conductivity of 0.1 to 100 S / m. The catalyst has a suitable electrical conductivity to ensure that a relatively low voltage is applied to generate appropriate current and Joule heating, without causing excessive line losses due to excessive current.

[0012] A second aspect of the present invention provides a method for preparing the above-mentioned endogenous Joule thermal catalyst, comprising the following steps: A. Dissolve the active metal salt in a solvent, then impregnate it into titanium dioxide powder, and dry it to obtain a mixture; B. The mixture is reduced in a hydrogen atmosphere to form a composite structure of a titanium suboxide support and a loaded active metal.

[0013] This preparation method involves a two-step process of active metal salt impregnation and hydrogen co-reduction, which simultaneously completes the preparation of titanium suboxide support and the loading of active metal to obtain a catalyst with high metal dispersion. During the reduction process, the active metal and titanium suboxide undergo atomic penetration and form chemical bonds, building a strong interaction, which lays the structural foundation for the high activity and high stability of the catalyst.

[0014] In some preferred or optional embodiments, in step B, the reduction temperature is 600~1000℃ and the time is 1~8 hours. This invention utilizes the characteristic of active metals reducing and then activating hydrogen to promote the reduction of titanium dioxide to titanium suboxide with high conductivity and abundant oxygen vacancies at a relatively low temperature not exceeding 1000℃, thus avoiding sintering or a decrease in specific surface area.

[0015] In some preferred or optional embodiments, in step B, an electric current is applied to the mixture during the reduction process, with a voltage of 1–100V or a current of 0.1–3A. In step B, as the reduction of H2 deepens, the sample gradually acquires a certain degree of conductivity. Applying a voltage to it can generate a certain current, thereby inducing an electrically driven lattice oxygen migration effect, accelerating the reduction of titanium dioxide, and further lowering the formation temperature of titanium suboxide.

[0016] In some preferred or optional embodiments, in step A, the titanium dioxide powder has a rutile phase and / or anatase phase. Rutile and anatase titanium dioxide have stable crystal structures and are not prone to phase transformation or sintering during subsequent impregnation and calcination, thus maintaining a high specific surface area for a long time.

[0017] In some preferred or optional embodiments, in step A, the specific surface area of ​​the titanium dioxide powder is greater than or equal to 100 m². 2 / g. A high specific surface area means that the surface of titanium dioxide has more loading sites, which allows the active metal salt to be uniformly dispersed in the form of single atoms or small clusters, avoiding the aggregation of metal salts caused by low specific surface area and the formation of large-diameter metal particles after subsequent reduction; at the same time, the high specific surface area can enhance the contact interface between titanium dioxide and active metal, providing sufficient interfacial conditions for the formation of strong interactions during co-reduction, ensuring the high activity and high stability of the catalyst.

[0018] In some preferred or optional embodiments, in step A, the solvent is water and / or ethanol, and the active metal salt is selected from at least one of nitrates, chlorides, acetates, and citrates. These metal salts have a certain degree of solubility, ensuring that the metal ions are uniformly dispersed in the solution, thereby achieving uniform impregnation onto the titanium dioxide surface; and the anions of the active metal salt are easily decomposed into gas or reduced and removed during subsequent hydrogen reduction, leaving no impurities in the catalyst and avoiding affecting the catalyst's performance.

[0019] In some preferred or optional embodiments, the preparation method further includes a step B0 prior to step B, in which the mixture is calcined in air. Adding a calcination step allows the active metal salt supported on the titanium dioxide surface to decompose into active metal oxides, preventing the uncalcined metal salt from agglomerating due to excessively rapid decomposition during subsequent hydrogen reduction. Simultaneously, the metal oxides can form weak interactions with the titanium dioxide surface, laying the foundation for strong interactions during subsequent hydrogen reduction.

[0020] In some preferred or optional embodiments, in step B0, the calcination temperature is 500~800℃ and the time is 1-5 hours. Controlling the calcination temperature and time ensures that the active metal salt is fully decomposed into pure metal oxides, providing a pure and uniformly dispersed precursor for subsequent reduction steps.

[0021] The third aspect of the present invention provides the application of the above-mentioned endogenous Joule thermal catalyst, wherein the endogenous Joule thermal catalyst is stacked in a reactor to form a catalyst bed, a mixed gas containing methane and carbon dioxide is introduced into the reactor to contact the catalyst bed, and the catalyst bed is simultaneously electrified to drive the methane dry reforming reaction.

[0022] This application method achieves the core advantages of electrothermal coupled catalysis: First, the catalyst bed formed by catalyst stacking ensures full contact between the mixed gas and the catalyst, guaranteeing a complete reaction; second, applying electricity to the catalyst bed allows the current to flow directly through the catalyst, achieving self-heating of the catalyst through endogenous Joule heating, completely solving the energy loss problem of traditional external heating or indirect heat transfer through electrothermal materials; third, the current synchronously induces electronic effects, enhancing the activation and conversion of CO2 and CH4, resulting in a significantly higher conversion rate and selectivity for methane dry reforming than existing technologies, while the catalyst remains stable in the redox dynamic equilibrium, forming good stability and durability.

[0023] In some preferred or optional embodiments, the volume fraction of methane and carbon dioxide in the mixed gas is 10% to 70%. This ensures sufficient reactant concentration in the reaction system, providing enough raw materials for the methane dry reforming reaction and guaranteeing high reaction efficiency.

[0024] In some preferred or optional embodiments, the inlet volume ratio of methane to carbon dioxide in the mixed gas is 0.3:1 to 3:1. Adjusting the inlet ratio of CH4 and CO2 can regulate the H2 / CO ratio of the products and can be extended to the development and utilization of CH4-rich biogas and CO2-rich natural gas.

[0025] In some preferred or optional embodiments, the mass hourly space velocity of the mixed gas relative to the catalytic bed is 1 to 100 L·g. -1 cat ·h -1 Ensure that the gas mixture has sufficient residence time in the catalytic bed to allow CH4 and CO2 to fully contact the active sites and react.

[0026] In some preferred or optional embodiments, the voltage applied to the catalyst bed is 1–500 V, or the current is 0.1–10 A. By setting a reasonable range of electrical parameters, the endogenous Joule heating effect of the catalyst can be used to provide sufficient temperature for the reaction with low energy consumption, and the electronic effect can be fully utilized to improve the reaction performance.

[0027] In some preferred or optional embodiments, after the catalyst bed is energized, it is heated to 400-900°C under endogenous Joule heating. Methane dry reforming is a strongly endothermic reaction, and this temperature range can sustain the reaction, achieving a high conversion rate. Simultaneously, this temperature range matches the electrothermal characteristics of the catalyst, allowing it to be stably maintained through endogenous Joule heating without the need for an external heat source, further reducing energy consumption.

[0028] In some preferred or optional embodiments, the electricity supplied to the catalytic bed is selected from wind power, hydropower, solar power, and nuclear power. Based on the excellent energy utilization efficiency and reaction performance of the electrothermal coupling catalysis of the endogenous Joule thermal catalyst in the dry reforming of methane, and using electricity with a relatively low emission factor as the reaction driving force, net negative CO2 emissions from the dry reforming of methane can be achieved.

[0029] In summary, compared with the prior art, the present invention has the following beneficial effects: (1) The endogenous Joule heating catalyst of the present invention constructs a dual-function active, conductive and electrothermal integrated system. The titanium suboxide support contains a large number of oxygen vacancies that can efficiently activate CO2, and the lattice conductive TiO layer has electrothermal properties. The active metal is responsible for the dissociation and activation of CH4, and together with the support, it forms a conductive network. When current flows through the catalyst, there is no need to rely on additional electrothermal materials. The catalyst itself achieves self-heating through endogenous Joule heating, which completely avoids the energy waste of traditional external heating equipment and conventional electrothermal coupling technology. The energy utilization efficiency is greatly improved compared with the prior art.

[0030] (2) Relying on the strong interaction between sub-titanium oxide and the active metal, the current-induced electronic effect is significantly enhanced. The active oxygen (O*) generated by CO2 activation on sub-titanium oxide can rapidly migrate to the surface of the active metal and react with the CH4 activation product (CH4). x The C*) reaction efficiently generates CO, while oxygen vacancies are instantly regenerated on the support surface to continuously activate CO2, forming a highly efficient cycle of CO2 activation → reactive oxygen migration → CH4 product oxidation. The endogenous Joule heat of this electronic effect coupled catalyst can greatly improve the reaction performance of methane dry reforming.

[0031] (3) The titanium suboxide support can form a dynamic equilibrium of being oxidized by CO2 and reduced by CH4 in the reaction, avoiding the loss of traditional electrothermal materials due to irreversible oxidation by CO2; at the same time, the strong interaction between titanium suboxide and active metal can effectively anchor active metal particles and inhibit their agglomeration and sintering at high temperature, and the catalyst exhibits good stability and durability.

[0032] (4) Based on its extremely high energy utilization efficiency and reactivity, this invention is driven by low-emission electricity such as wind power, hydropower, solar power, and nuclear power. It not only directly consumes two greenhouse gases, CH4 and CO2, but also offsets the trace carbon emissions from electricity production, ultimately achieving net negative CO2 emissions from the methane dry reforming reaction. At the same time, the catalyst is adapted to CH4 / CO2 mixed gas with a volume fraction of 10% to 70%, and can directly process diverse raw materials such as CH4-rich biogas and CO2-rich industrial tail gas without deep purification and pretreatment, further reducing the carbon footprint and cost of industrial applications.

[0033] (5) The present invention adopts an innovative preparation process. Relying on the activation effect of active metal on hydrogen, titanium dioxide can be reduced at a lower temperature to obtain a titanium suboxide support. At the same time, the loading of active metal and the preparation of titanium suboxide support are realized, thereby obtaining a catalyst structure with high metal dispersion and strong metal-support interaction. Attached Figure Description

[0034] Figure 1 This is a scanning electron microscope image of the nickel-loaded titanium suboxide prepared in Example 2 of the present invention.

[0035] Figure 2 This is a transmission electron microscope (TEM) image of the nickel-loaded titanium suboxide prepared in Example 2 of the present invention.

[0036] Figure 3 The graph shows the resistance change over time during the electrostatic reduction preparation of nickel-loaded titanium suboxide in Example 3 of this invention.

[0037] Figure 4 This is a schematic diagram of the electrothermal catalytic reactor structure used in an embodiment of the present invention.

[0038] Figure 5 This is a graph showing the change in the conversion rate of carbon dioxide and methane over time in Example 11 of the present invention.

[0039] Figure 6 This is a graph showing the temperature and resistance of the catalyst bed over time in Example 11 of the present invention.

[0040] Figure 7 This is a graph showing the change in the conversion rate of carbon dioxide and methane over time in Comparative Example 1 of the present invention.

[0041] Figure 8This is a graph showing the temperature and resistance of the catalytic bed in Comparative Example 2 of the present invention as a function of time.

[0042] Figure 9 This is a graph showing the temperature and resistance of the catalytic bed in Comparative Example 3 of the present invention as a function of time.

[0043] Figure 10 This is a graph showing the temperature and resistance of the catalytic bed in Comparative Example 4 of the present invention as a function of time. Detailed Implementation

[0044] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0045] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0046] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0047] The present invention provides an endogenous Joule thermal catalyst for methane dry reforming and its preparation and application method. The preparation method consists of two steps: active metal salt impregnation and hydrogen co-reduction. The specific steps are as follows: The system provides an active metal salt, titanium dioxide powder, and a solvent. The active metal can be selected from nickel, cobalt, rhodium, ruthenium, palladium, platinum, iridium, etc., and a soluble metal salt such as nitrate, chloride, acetate, citrate, etc. In specific embodiments, nickel nitrate, cobalt acetate, chloroplatinic acid, palladium chloride, iridium chloride, etc., can be used. The titanium dioxide powder has a rutile phase, anatase phase, or a mixture of both, and its specific surface area is ≥100 m². 2 / g ensures that the active metal salt can be highly dispersed on the titanium dioxide surface, with a particle size ≤5μm, and can be used without additional pretreatment. Deionized water, anhydrous ethanol, or a mixture of both can be used as solvents. Water and ethanol can effectively dissolve the active metal salt and are easily volatile.

[0048] Calculate the mass ratio of active metal salt to titanium dioxide according to the target active metal loading (0.02%~15%), weigh the corresponding mass of active metal salt and dissolve it in the solvent. After stirring to form a uniform solution, add titanium dioxide powder to the solution and ultrasonically disperse it so that the metal salt solution is uniformly impregnated on the surface of the powder. Then dry it in an oven and grind it until there are no lumps to obtain a mixture.

[0049] A roasting step can be set according to requirements. The dried mixture is placed in a muffle furnace and roasted at 500~800℃ for 1~5 hours in an air atmosphere. After cooling to room temperature, it can be used for later use. Roasting can decompose the metal salt into metal oxides and enhance the interaction between the metal and the support in the subsequent reduction process.

[0050] The calcined / uncalcined mixture is placed in a quartz reaction tube, hydrogen gas is introduced, and the temperature is raised to 600-1000°C. The mixture is then held at this temperature for 1-8 hours to complete the formation of the titanium suboxide support and the reduction of the active metal. In some embodiments, after the mixture exhibits preliminary conductivity, a closed circuit is formed by applying a voltage of 1-100V or a current of 0.1-3A through electrodes. This current-induced electronic effect lowers the titanium suboxide formation temperature. After reduction, the mixture is naturally cooled to room temperature, ground, and sieved to obtain particles of 10-300 mesh to yield the endogenous Joule thermal catalyst.

[0051] In existing technologies, titanium suboxide is prepared by high-temperature reduction of titanium dioxide, with synthesis temperatures above 1000°C. The resulting titanium suboxide has a relatively low specific surface area (typically below 2m²). 2 / g). If active metals are directly loaded onto titanium dioxide, high metal dispersion and strong metal-support interactions cannot be obtained. The above method involves loading an active metal salt onto titanium dioxide powder and simultaneously reducing both the active metal salt and titanium dioxide with hydrogen gas. This simultaneously loads the active metal and prepares the titanium dioxide support, ultimately yielding a catalyst with high metal dispersion and strong metal-support interaction. This overcomes the aforementioned problems: In the impregnation step, the active metal salt is loaded onto the high specific surface area of ​​titanium dioxide, resulting in high dispersion and maintaining relatively high metal dispersion during the subsequent reduction process; in the reduction step, the active metal salt is reduced by hydrogen gas before titanium dioxide, and the resulting active metal activates the hydrogen gas, thereby promoting the reduction of titanium dioxide, allowing for the production of titanium dioxide at temperatures below 1000°C; during the simultaneous reduction process, atomic penetration occurs between the active metal and titanium dioxide, forming stable chemical bonds, resulting in a strong interaction between them; and by adjusting the reduction temperature and time in step 2, titanium dioxide supports with different crystal forms and conductivityes, such as Ti4O7, Ti5O9, and Ti6O7, can be obtained. 11 Ti7O 13 Ti8O 15 Ti9O 17 wait.

[0052] The endogenous Joule thermal catalyst prepared by the above method comprises a titanium suboxide support and an active metal supported on the support. The catalyst's electrical conductivity is controlled within the range of 0.1–100 S / m, and the macroscopic particle size is 10–300 mesh. The support composition is selected from Ti4O7, Ti5O9, and Ti6O. 11 Ti7O 13 Ti8O 15 Ti9O 17 At least one of the following titanium suboxides is used: these titanium suboxides possess good electrical conductivity and electrothermal properties, and also have abundant oxygen vacancies for CO2 activation. The active metal is at least one of nickel, cobalt, rhodium, ruthenium, palladium, platinum, and iridium, with an active metal particle size ≤100 nm and a loading of 0.02%~15%, and there is a strong interaction between the titanium suboxide support and the active metal.

[0053] This catalyst uses titanium suboxide as a support. The oxygen atoms in titanium suboxide are missing relative to the titanium atoms, creating numerous oxygen vacancies. These vacancies can be used to dissociate and activate CO2 molecules (CO2→CO+O*), generating surface-active oxygen O*. Loading an active metal onto the titanium suboxide support can also dissociate and activate CH4 molecules (CH4→CH). x *+H2→C*+H2). Therefore, in the design of this catalytic system, titanium suboxide, in addition to dispersing the active metal, also provides important active sites for the dry reforming reaction of methane. Simultaneously, titanium suboxide possesses conductivity due to the presence of a conductive TiO layer within its crystal lattice, and thus the catalyst formed by supporting the conductive active metal also possesses conductivity.

[0054] The above-mentioned endogenous Joule thermal catalyst was applied to the dry reforming reaction of methane, and the specific operation was as follows: A reactor is provided in which an endogenous Joule-thermal catalyst is stacked to form a catalytic bed. A porous conductive medium is used to press and fix the catalytic bed on both sides. The porous conductive medium is short-circuited to the two poles of a power source via a wire, forming a circuit with the catalytic bed. This reactor structure ensures that current flows through the stacked endogenous Joule-thermal catalyst bed. A mixed gas containing methane and carbon dioxide is introduced into the reactor to contact the catalytic bed, and simultaneously, electricity is applied to the catalytic bed to drive the methane dry reforming reaction.

[0055] In a specific embodiment, the volume fraction of methane in the mixed gas is 10%~70%, the volume fraction of carbon dioxide is 10%~70%, and the mass hourly space velocity of the mixed gas relative to the catalyst bed is 1~100 L·g. -1 cat ·h -1 Reasonable reaction concentration and reaction space velocity can ensure high efficiency of methane dry reforming reaction.

[0056] In some embodiments, the intake ratio of CH4 and CO2 is adjusted to a range of 0.3:1 to 3:1, thereby adjusting the product H2 / CO ratio and extending to the development and utilization of CH4-rich biogas and CO2-rich natural gas.

[0057] In a specific embodiment, a voltage of 1-500V or a current of 0.1-10A is applied to the catalytic bed. The parameters are adjusted according to the catalyst's conductivity. After the catalytic bed is energized, it heats to 400-900℃ under endogenous Joule heating. This utilizes the endogenous Joule heating effect of the catalyst to provide sufficient temperature for the reaction with low energy consumption and fully leverages electronic effects to enhance reaction performance. The electricity used is selected from wind power, hydropower, solar power, or nuclear power to ensure low-carbon emissions from the reaction.

[0058] The use of endogenous Joule heat catalysts in the electrothermal coupling catalysis of methane dry reforming differs from electrothermal coupling catalysis utilizing the electrothermal effects of metallic, carbonaceous, or carbon-containing materials. In this method, the current flows through the entire catalyst, including both the sub-titanium oxide support and the active metal, which simultaneously play a catalytic role. The endogenous Joule heat of the catalyst allows for self-heating, reducing heat transfer losses. Furthermore, the current induces electronic effects in the catalyst, particularly the electrically driven lattice oxygen migration effect. Under this effect, the active oxygen O* dissociated from CO2 on the sub-titanium oxide support can migrate more rapidly to the surface of the active metal, where it dissociates with CH4 to produce carbonaceous species (CH4). x The reaction of * and / or C*) produces CO, while simultaneously creating numerous oxygen vacancies on the titanium suboxide support for CO2 dissociation and activation. This electronic effect-coupled endogenous Joule heating of the catalyst significantly enhances the performance of the methane dry reforming reaction. Furthermore, the titanium suboxide support can achieve a dynamic equilibrium between CO2 oxidation and CH4 reduction, thus maintaining good stability during the dry reforming reaction. Therefore, this invention overcomes the technical challenges of electrothermal coupling catalysis in methane dry reforming, enabling current to flow through the catalytically active component, effectively enhancing reaction performance by coupling endogenous Joule heating and electronic effects, and maintaining catalyst stability and durability during the reaction.

[0059] The technical effects of the present invention will be described below with reference to specific embodiments. Unless otherwise specified, the raw materials used in the embodiments of this application were all purchased through commercial channels.

[0060] Example 1 Nickel-supported titanium suboxide catalysts were prepared directly using titanium suboxide as a precursor, as follows: 0.9 g of nickel nitrate hexahydrate was dissolved in 10 mL of water, and 2 g of commercial titanium suboxide (crystal form Ti4O7, specific surface area 2 m²) was added. 2(Approximately / g), ultrasonically dispersed, dried and ground, the resulting mixture was calcined at 600°C for 3 hours in air atmosphere, and then reduced at 400°C for 2 hours with pure hydrogen to obtain a nickel-loaded titanium suboxide catalyst, wherein the mass loading of nickel is 8.3%.

[0061] Example 2 The preparation of nickel-supported titanium suboxide catalyst using titanium dioxide as a precursor is as follows: 0.9 g of nickel nitrate hexahydrate was dissolved in 10 mL of water, and 2 g of rutile phase titanium dioxide powder (specific surface area 120 m²) was added. 2 (Approximately / g), ultrasonically dispersed, dried, and ground. The resulting mixture was calcined at 700°C for 1 hour in air, cooled, and then reduced with hydrogen at temperatures of 850, 900, 950, and 1000°C for 3 hours to obtain a nickel-loaded titanium suboxide electrothermal catalyst, wherein the nickel loading was 9%. Powder X-ray diffraction characterization of the catalyst revealed that, in addition to the metallic nickel phase, it also contained a titanium suboxide phase. The degree of titanium dioxide reduction increased with increasing reduction temperature. As shown in Table 1, the titanium suboxide phase obtained at reduction temperatures of 850, 900, 950, and 1000°C included Ti9O. 17 Ti8O 15 Ti6O 11 The measured electrical conductivities of Ti4O7 were 0.48, 1.13, 1.61, and 26.54 S / m, respectively. Scanning electron microscopy was used to observe the catalysts prepared by reduction at 950°C, and the results are as follows: Figure 1 As shown, metallic nickel particles with an average particle size of approximately 80 nm can be observed adhering to the surface of titanium suboxide. Furthermore, the catalyst prepared by reduction at 950°C was characterized by transmission electron microscopy, and the results are as follows: Figure 2 As shown, nickel particles are embedded in the titanium suboxide support, indicating a strong interaction between the nickel particles and the titanium suboxide.

[0062] Table 1. Crystal structure and conductivity of titanium suboxide in nickel-supported titanium suboxide catalysts obtained at different reduction temperatures. Example 3 A nickel-supported titanium suboxide catalyst was prepared by using titanium dioxide as a precursor and enhancing its reduction through electrochemical fluxing. The specific steps were as follows: 0.9 g of nickel acetate tetrahydrate was dissolved in 10 mL of water, and 2 g of rutile titanium dioxide powder was added. The mixture was ultrasonically dispersed, dried, and ground. The resulting mixture was calcined at 700°C for 1 hour in air. After cooling, a 60V voltage was applied to the sample, and pure hydrogen was simultaneously introduced for reduction at 600°C for 1.5 hours. Figure 3 As shown, the conductivity improves and the resistance gradually decreases with the extension of reduction time, and finally nickel-loaded titanium suboxide catalyst is obtained, in which the mass loading of nickel is 9.6%.

[0063] Example 4 Nickel-supported titanium suboxide catalyst was prepared using titanium dioxide as a precursor as follows: 0.5 g of nickel citrate monohydrate was dissolved in 10 mL of water, 2 g of anatase phase titanium dioxide powder was added, ultrasonically dispersed, dried and ground, and the resulting mixture was reduced with hydrogen at 900°C for 3 hours to obtain nickel-supported titanium suboxide catalyst, wherein the mass loading of nickel was 7.9%.

[0064] Example 5 Cobalt-supported titanium suboxide catalyst was prepared using titanium dioxide as a precursor as follows: 1.0 g of cobalt acetate tetrahydrate was dissolved in 10 mL of water, 2 g of rutile phase titanium dioxide powder was added, ultrasonically dispersed, dried and ground, and the resulting mixture was calcined at 600 °C for 5 hours in air atmosphere, cooled and reduced with hydrogen at 850 °C for 8 hours to obtain cobalt-supported titanium suboxide catalyst, wherein the mass loading of cobalt was 11%.

[0065] Example 6 Platinum-supported titanium dioxide catalyst was prepared using titanium dioxide as a precursor as follows: 0.1 g of chloroplatinic acid hexahydrate was dissolved in 10 mL of ethanol, 2 g of rutile phase titanium dioxide powder was added, ultrasonically dispersed, dried and ground, and the resulting mixture was calcined at 500 °C for 3 hours in air atmosphere, cooled and then reduced with hydrogen at 900 °C for 8 hours to obtain platinum-supported titanium dioxide catalyst, wherein the mass loading of platinum was 1.9%.

[0066] Example 7 Rhodium-supported titanium suboxide catalyst was prepared using titanium dioxide as a precursor as follows: 0.05 g of rhodium trichloride trihydrate was dissolved in 10 mL of ethanol, 2 g of rutile phase titanium dioxide powder was added, ultrasonically dispersed, dried and ground, and the resulting mixture was calcined at 500 °C for 2 hours in air atmosphere, cooled and reduced with hydrogen at 900 °C for 5 hours to obtain rhodium-supported titanium suboxide catalyst, wherein the mass loading of rhodium was 1.0%.

[0067] Example 8 Ruthenium-supported titanium suboxide catalyst was prepared using titanium dioxide as a precursor as follows: 0.01 g of ruthenium trichloride hydrate was dissolved in 10 mL of ethanol, 2 g of rutile phase titanium dioxide powder was added, ultrasonically dispersed, dried and ground, and the resulting mixture was calcined at 500 °C for 5 hours in air atmosphere, cooled, and then reduced with hydrogen at 900 °C for 8 hours to obtain ruthenium-supported titanium suboxide catalyst, wherein the mass loading of ruthenium was 0.02%.

[0068] Example 9 A palladium-supported titanium suboxide catalyst was prepared using titanium dioxide as a precursor as follows: 0.05 g of palladium chloride was dissolved in 10 mL of ethanol, 2 g of rutile phase titanium dioxide powder was added, the mixture was ultrasonically dispersed, dried and ground, and the resulting mixture was calcined at 500 °C for 3 hours in air atmosphere. After cooling, it was reduced with hydrogen at 900 °C for 6 hours to obtain a palladium-supported titanium suboxide catalyst, wherein the mass loading of palladium was 1.5%.

[0069] Example 10 The iridium-supported titanium suboxide catalyst was prepared using titanium dioxide as a precursor as follows: 0.08 g of iridium trichloride hydrate was dissolved in 10 mL of water, 2 g of rutile phase titanium dioxide powder was added, ultrasonically dispersed, dried and ground, and the resulting mixture was calcined at 500 °C for 3 hours in air atmosphere. After cooling, it was reduced with hydrogen at 900 °C for 3 hours to obtain the iridium-supported titanium suboxide catalyst, wherein the iridium mass loading was 2.6%.

[0070] Example 11 Preparation Figure 4 The reactor shown includes a first conductive rod 11, a second conductive rod 12, a heat insulation layer 2, a first copper filter element 31, a second copper filter element 32, a catalytic bed 4, a reaction tube 5, and a thermocouple 6. The catalytic bed 4 is fixed in the middle of the reaction tube 5 by the first copper filter element 31 and the second copper filter element 32, and then connected to the positive and negative terminals of an adjustable power supply regulator via the first conductive rod 11 and the second conductive rod 12, respectively. The heat insulation layer 2 covers the outer wall of the reaction tube 5, and the patch thermocouple 6 is fixed to the outer wall of the reaction tube 5, corresponding to the middle position of the catalytic bed 4, to detect the temperature of the catalytic bed 4.

[0071] Weigh 0.2 g of the endogenous Joule thermal catalyst prepared in the above examples. The macroscopic particle size is 20-40 mesh. Stack the catalyst into a catalyst bed 4 and place it in the reactor. Introduce a mixed gas containing methane and carbon dioxide, using high-purity helium as the balance gas. Control the reaction gas flow rate using a mass flow meter. Adjust the electrical input power through a power program. Connect the gas outlet to a gas chromatograph for online component analysis. First, purge the catalyst with a He gas stream for 30 min. Then, introduce the reaction gas with a component volume ratio of He:CO2:CH4 = 2:1:1 and a mass hourly space velocity (WHSV) of 18 L·g⁻¹. -1 cat ·h -1 At the same time, an electric current is passed into the catalyst to initiate the dry reforming reaction of methane.

[0072] The nickel-loaded titanium suboxide prepared by reduction at 950°C in Example 2 was used as the endogenous Joule thermal catalyst, with an input power of 15W (voltage of about 17.65V and current of about 0.85A). Figure 5 The graphs showing the conversion rates of carbon dioxide and methane over time are presented. Figure 5It can be seen that the carbon dioxide conversion rate remained at 95%, the methane conversion rate remained at 90%, and the conversion rate did not show a significant decrease after 10 hours. Furthermore, Figure 6 The results showed that the catalytic bed resistance remained at a low level, while the catalytic bed temperature remained stable at around 760℃, indicating that the catalyst has strong stability in the reaction.

[0073] Table 2 summarizes the performance of the endogenous Joule thermal catalysts prepared in Examples 1-11 in the electrothermal catalytic dry reforming of methane. As can be seen from the table, the performance of the nickel-supported titanium suboxide catalysts prepared using titanium dioxide as a precursor (Examples 2-4) is superior to that prepared directly using titanium suboxide as a precursor (Example 1). This is due to the strong metal-support interaction in the former (…). Figure 2 This is beneficial for the dry reforming of methane.

[0074] Table 2 Performance of the catalysts prepared in Examples 1-11 in the electrothermal catalytic dry reforming of methane at 15W power. Based on optimized performance data from electrothermal catalytic dry reforming of methane, it was calculated that producing 1 kg of hydrogen requires 11 kg of carbon dioxide and 55 kWh of electricity. The net carbon dioxide emissions per kg of hydrogen produced can then be calculated using the electricity generation emission factor (carbon dioxide emissions per kWh of electricity generated), as shown in Table 3. The table shows that using wind, nuclear, hydro, or solar power as the electricity source for electrothermal catalytic dry reforming of methane can achieve net negative carbon dioxide emissions.

[0075] Table 3 Net CO2 emissions from electrothermal catalysis of methane dry reforming reaction using endogenous Joule thermal catalysts Comparative Example 1 A conventional externally heated catalytic reaction was designed and conducted, and its activity was compared with that of an electrothermal catalytic reaction. The specific procedure is as follows: a reaction tube encapsulated with a self-generated Joule thermal catalyst (refer to...) was used... Figure 4 The catalyst bed is placed in a tubular furnace, and reaction gas with the same flow rate, composition and space velocity is introduced into the catalyst bed. The catalyst is heated to the target temperature using the heating function of the tubular furnace to carry out the methane dry reforming reaction.

[0076] Taking the nickel-supported titanium suboxide catalyst prepared by reduction at 950℃ in Example 2 as an example, Figure 7 The reaction activity diagram of catalytic dry reforming of methane at 750℃ under external heating mode is shown. The carbon dioxide conversion rate is 53%, and the methane conversion rate is 43%, which is lower than the electrothermal catalytic performance of the same catalyst at 15W power (endogenous Joule heating temperature around 750℃) (carbon dioxide conversion rate 95%, methane conversion rate 90%, see...).Figure 5 ).

[0077] Similarly, taking the cobalt-supported titanium suboxide catalyst prepared in Example 5 as an example, the electrothermal catalytic dry reforming performance of methane (carbon dioxide conversion rate 88%, methane conversion rate 79%, see Table 2) is higher than the catalytic performance of conventional external heating at the same temperature (750℃) (carbon dioxide conversion rate 30%, methane conversion rate 15%).

[0078] The above comparison shows that endogenous Joule thermal catalysts have an electronic effect that promotes the dry reforming reaction of methane in electrothermal catalysis.

[0079] Comparative Example 2 Using activated carbon as a support, nickel and lanthanum oxide were simultaneously loaded as a comparative electrothermal catalyst. The preparation method is as follows: 0.5 g of nickel nitrate hexahydrate and 0.37 g of lanthanum nitrate hexahydrate were dissolved in 10 mL of water, 2 g of activated carbon was added, and the mixture was ultrasonically dispersed, dried and ground. The resulting mixture was calcined at 850 °C for 5 hours under a nitrogen atmosphere, cooled, and then reduced with hydrogen at 600 °C for 2 hours to obtain an activated carbon electrothermal catalyst co-loaded with nickel and lanthanum oxide, with mass fractions of 5% and 7% for nickel and lanthanum oxide, respectively.

[0080] 0.2 g of the above catalyst was stacked to form a catalyst bed and placed in the reactor of Example 11. After purging with He for 30 min, a carrier gas and a reactant gas were introduced in a ratio of He:CO2:CH4 = 2:1:1, with a mass hourly space velocity (WHSV) of 18 L·g⁻¹. -1 cat ·h -1 As the input electrical power is gradually increased, the temperature and resistance of the catalytic bed change over time as follows: Figure 8 As shown, during the temperature change process with increasing power, the resistance fluctuated violently. When the power reached 14W, although the conversion rates of carbon dioxide and methane reached 80% and 62% respectively, the reaction was forced to stop due to the sharp increase in resistance and eventual power failure, followed by a drop in temperature. This was because the activated carbon support was excessively oxidized and consumed by carbon dioxide during the reaction, leading to the breakage of the catalyst bed.

[0081] Comparative Example 3 Using antimony tin oxide as a support and nickel as a comparative electrothermal catalyst, the preparation method is as follows: 0.9 g of nickel nitrate hexahydrate was dissolved in 10 mL of water, 2 g of antimony tin oxide powder was added, ultrasonically dispersed, dried and ground, and the resulting mixture was calcined at 600 °C for 3 hours in air atmosphere. After cooling, it was reduced with hydrogen at 400 °C for 1 hour to obtain nickel-supported antimony tin oxide electrothermal catalyst, wherein the nickel loading was 9.1%.

[0082] 0.2 g of the above catalyst was stacked to form a catalyst bed and placed in the reactor of Example 11. After purging with He for 30 min, a carrier gas and a reactant gas were introduced in a ratio of He:CO2:CH4 = 2:1:1, with a mass hourly space velocity (WHSV) of 18 L·g⁻¹. -1 cat ·h -1 As the input electrical power is gradually increased, the temperature and resistance of the catalytic bed change as follows: Figure 9 As shown, when the power increases to 15W, the resistance rises sharply and eventually the power is cut off, the temperature drops, and the reaction is forced to stop. This is because the antimony tin oxide support is excessively reduced by methane and loses its conductivity.

[0083] Comparative Example 4 Using lanthanum nickel perovskite (LaNiO3) as a comparative electrothermal catalyst, the preparation method is as follows: LaNiO3 was prepared by the sol-gel method. 0.01 mol La(NO3)3·6H2O, 0.01 mol Ni(NO3)2·6H2O, and 0.02 mol ethylene glycol (C2H6O2) were dissolved in 200 mL of deionized water. 0.02 mol citric acid (C6H8O7) was dissolved in 200 mL of deionized water for later use. The two solutions were mixed and continuously stirred at 80 °C until a wet gel was formed. The wet gel was dried at 100 °C for 12 hours to obtain a dry gel. The dry gel was calcined at 600 °C for 3 hours in air to obtain LaNiO3.

[0084] 0.2 g of the above catalyst was stacked to form a catalyst bed and placed in the reactor of Example 11. After purging with He for 30 min, a carrier gas and a reactant gas were introduced in a ratio of He:CO2:CH4 = 2:1:1, with a mass hourly space velocity (WHSV) of 18 L·g⁻¹. -1 cat ·h -1 The power was maintained at 16W. Initially, the conversion rates of carbon dioxide and methane were 80% and 65%, respectively; the temperature and resistance changes of the catalyst were as follows: Figure 10 As shown, after 80 minutes of reaction, the catalyst resistance began to fluctuate violently, and after 95 minutes, it lost its conductivity, causing the temperature to drop and the reaction to be forced to stop. This was due to the excessive reduction of LaNiO3 by methane, which led to the loss of conductivity.

[0085] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the scope of protection of this invention.

Claims

1. An endogenous Joule thermal catalyst for dry reforming of methane, characterized in that, It includes a titanium suboxide support and an active metal supported on the titanium suboxide support, wherein the titanium suboxide support is selected from Ti4O7, Ti5O9, and Ti6O. 11 Ti7O 13 Ti8O 15 Ti9O 17 At least one of the following, wherein the active metal is at least one of nickel, cobalt, rhodium, ruthenium, palladium, platinum, and iridium, and the endogenous Joule thermal catalyst has electrothermal properties.

2. The endogenous Joule thermal catalyst for dry reforming of methane according to claim 1, characterized in that, There is a strong interaction between the sub-titanium oxide support and the active metal.

3. The endogenous Joule thermal catalyst for dry reforming of methane according to claim 1 or 2, characterized in that, Based on the total mass of the endogenous Joule thermal catalyst, the loading of the active metal is 0.02% to 15%.

4. The endogenous Joule thermal catalyst according to claim 1 or 2, characterized in that, The particle size of the active metal is no greater than 100 nm.

5. The endogenous Joule thermal catalyst according to claim 1 or 2, characterized in that, The macroscopic particle size of the endogenous Joule thermal catalyst is 10~300 mesh.

6. The endogenous Joule thermal catalyst according to claim 1 or 2, characterized in that, The electrical conductivity of the endogenous Joule thermal catalyst is 0.1~100 S / m.

7. A method for preparing an endogenous Joule thermal catalyst as described in any one of claims 1-6, characterized in that, Includes the following steps: A. Dissolve the active metal salt in a solvent, then impregnate it into titanium dioxide powder, and dry it to obtain a mixture; B. The mixture is reduced in a hydrogen atmosphere to form a composite structure of a titanium suboxide support and a loaded active metal.

8. The preparation method according to claim 7, characterized in that, In step B, the reduction temperature is 600~1000℃ and the time is 1~8 hours.

9. The preparation method according to claim 7, characterized in that, In step B, during the reduction process, an electric current is applied to the mixture, with a voltage of 1 to 100V or a current of 0.1 to 3A.

10. The preparation method according to claim 9, characterized in that, In step A, the specific surface area of ​​the titanium dioxide powder is greater than or equal to 100 m². 2 / g.

11. The preparation method according to claim 7, characterized in that, In step A, the solvent is water and / or ethanol, and the active metal salt is selected from at least one of nitrates, chlorides, acetates, and citrates.

12. The preparation method according to any one of claims 7-11, characterized in that, It also includes step B0, which precedes step B, by roasting the mixture in air.

13. The preparation method according to claim 12, characterized in that, In step B0, the calcination temperature is 500~800℃ and the time is 1-5 hours.

14. The application of an endogenous Joule thermal catalyst as described in any one of claims 1-6, characterized in that, An endogenous Joule-thermal catalyst is stacked in a reactor to form a catalytic bed. A mixed gas containing methane and carbon dioxide is introduced into the reactor to contact the catalytic bed, while simultaneously electrifying the catalytic bed to drive the methane dry reforming reaction.

15. The application according to claim 14, characterized in that, The volume fraction of methane in the gas mixture is 10% to 70%, and the volume fraction of carbon dioxide is 10% to 70%.

16. The application according to claim 15, characterized in that, In the mixed gas, the inlet volume ratio of methane to carbon dioxide is 0.3:1 to 3:

1.

17. The application according to claim 14, characterized in that, The mass hourly space velocity of the mixed gas relative to the catalyst bed is 1~100 L·g -1 cat ·h -1 .

18. The application according to claim 14, characterized in that, The voltage applied to the catalyst bed is 1 to 500V, or the current is 0.1 to 10A.

19. The application according to claim 18, characterized in that, When the catalytic bed is energized, it heats up to 400-900℃ under the effect of endogenous Joule heating.

20. The application according to claim 14, characterized in that, The electricity supplied to the catalytic bed is selected from wind power, hydropower, solar power, and nuclear power.

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