A mgal2o4-based high-entropy spinel catalyst, a preparation method thereof and application in greenhouse gas conversion

Abstract

The application provides a MgAl2O4-based high-entropy spinel catalyst, a preparation method thereof and application in greenhouse gas conversion, and relates to the technical field of high-entropy spinel catalysts. The catalyst is constructed by constructing a multi-principal-element high-entropy structure in a MgAl2O4 spinel skeleton, and transition metals such as Ni, Co, Cu and Cr are introduced in a cooperative manner. Relying on the high-entropy stability and lattice distortion effect, the electronic structure, oxygen migration ability and surface acid-base characteristics of the catalyst are precisely controlled, and the efficient cooperation of CH4 dissociation and CO2 activation is realized. The catalyst prepared by the preparation method provided in the application still maintains excellent catalytic activity, super-strong carbon deposition resistance and long-period stability under harsh working conditions such as high space velocity, high temperature and rich methane, and has significant industrial application potential.

Description

Technical Field

[0001] This invention relates to the field of high-entropy spinel catalyst technology, and more particularly to a MgAl2O4-based high-entropy spinel catalyst, its preparation method, and its application in greenhouse gas conversion. Background Technology

[0002] Against the backdrop of the parallel advancement of global energy structure transformation and the "dual-carbon" strategic goals, how to synergistically resolve the contradiction between excessive greenhouse gas emissions from fossil fuel consumption and the efficient utilization of carbon resources is one of the most severe challenges currently facing the energy and chemical industry. Methane (CH4) and carbon dioxide (CO2), as two typical strong greenhouse gases, require resource-based synergistic conversion, which is not only a fundamental solution to mitigating climate change but also a key pathway to achieving a "carbon circular economy." Among these, the dry reforming (DRM) reaction (CH4 + CO2 → 2CO + 2H2) can directly convert these two greenhouse gases into syngas rich in hydrogen and carbon monoxide. This syngas is not only a core platform molecule for Fischer-Tropsch synthesis of liquid fuels, methanol synthesis, and high-value-added chemicals, but its H2 / CO ratio is also particularly well-suited for downstream high-end chemical processes such as carbonyl synthesis. Therefore, DRM technology is widely recognized as one of the most promising technologies for negative carbon emissions and low-carbon hydrogen production.

[0003] Although the DRM reaction has significant thermodynamic environmental and economic value, its industrialization has long been limited by the adaptability of catalysts to extreme operating conditions. Currently, supported nickel (Ni)-based catalysts, widely studied in industry, possess high methane activation capabilities and low cost, but they are prone to metal sintering, carbon deposition, and activity degradation under high-temperature reaction conditions (>800℃), severely restricting their industrial application. Traditional single-metal or bimetallic oxide catalysts, due to their limited structural stability, struggle to simultaneously achieve high activity, high stability, and high resistance to carbon deposition.

[0004] In view of this, it is necessary to design an improved MgAl2O4-based high-entropy spinel catalyst, its preparation method, and its application in greenhouse gas conversion to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a MgAl2O4-based high-entropy spinel catalyst, its preparation method, and its application in greenhouse gas conversion.

[0006] To achieve the above-mentioned objectives, in a first aspect, the present invention provides a MgAl2O4-based high-entropy spinel catalyst, the chemical formula of which is: (Mg a Co b Ni c Cu d Cr eAl2O4, a+b+c+d+e=1, the molar fractions of Mg, Co, Ni, Cu, and Cr are 0.1-0.4, preferably, the molar ratio of Mg, Co, Ni, Cu, and Cr is 0.2:0.2:0.2:0.2:0.2.

[0007] Secondly, the present invention provides a method for preparing a MgAl2O4-based high-entropy spinel catalyst, comprising the following steps:

[0008] According to the chemical formula of the high-entropy spinel catalyst, Mg source, Co source, Ni source, Cu source, Cr source and Al source are dissolved in water to obtain a precursor solution;

[0009] The precursor solution was subjected to ball milling and calcination in sequence to obtain a high-entropy spinel catalyst.

[0010] Preferably, the ball milling process is performed at a rotation speed of 500-700 rpm, the ball milling time is 2-4 h, and the ball-to-material ratio is (4-6):1.

[0011] Preferably, the calcination treatment is carried out at a temperature of 900-1100℃ for 8-12 hours.

[0012] Preferably, the ball milling process is performed at a rotation speed of 600 rpm, a milling time of 4 hours, and a ball-to-material ratio of 5:1.

[0013] Preferably, the calcination treatment is performed at a temperature of 1000°C for 10 hours.

[0014] Thirdly, the present invention provides an application of a MgAl2O4-based high-entropy spinel catalyst in greenhouse gas conversion.

[0015] Fourthly, this invention provides a reaction condition for the dry reforming of methane using a MgAl2O4-based high-entropy spinel catalyst, as follows: reaction temperature 800℃, feed gas composition of CH4, CO2, and Ar, with a CH4 to CO2 volume ratio of 1:1, total gas flow rate of 300 mL / min, and space velocity of 36000 mL·g. -1 ·h -1 The reaction time for the methane dry reforming is 0-150 h.

[0016] The beneficial effects of this invention are:

[0017] 1. The MgAl2O4-based high-entropy spinel catalyst provided by this invention constructs a multi-principal-element high-entropy structure in the MgAl2O4 spinel framework and synergistically introduces transition metals such as Ni, Co, Cu, and Cr. It utilizes the high-entropy stabilization effect and lattice distortion effect to achieve precise customization of the catalyst's electronic structure, oxygen migration ability, and surface acid-base properties. Among them, Ni and Co sites are responsible for enhancing the activation of CH4 bonds to provide high reactivity. Cu doping effectively inhibits deep methane cracking by modifying the electron cloud density of Ni sites. Cr element enhances the lattice oxygen migration rate through variable valence state to promote the oxidation and removal of surface carbon. The introduction of Mg component significantly enhances the catalyst's adsorption and activation ability for CO2. Based on this, the slow diffusion effect in the high-entropy structure can effectively suppress the migration and agglomeration of active metal particles under high temperature conditions, improve the catalyst's anti-sintering performance, and at the same time, the atomic-level uniform distribution of multiple metals in the spinel lattice induces abundant oxygen vacancies, promoting the synergistic process of CH4 dissociation and CO2 activation. Thus, the catalyst can still maintain excellent catalytic activity, strong anti-carbon deposition ability and long-term operational stability under harsh conditions such as high space velocity, high temperature and methane richness, and has significant potential for industrial application.

[0018] 2. The MgAl2O4-based high-entropy spinel catalyst provided by this invention effectively overcomes the inherent defects of existing commercial 5% Ni / Al2O3 and traditional single / few-metal catalysts in methane dry reforming reactions, such as easy carbon deposition, easy sintering, and poor stability. The above-mentioned MgAl2O4-based high-entropy spinel catalyst, at 800℃ and a space velocity of 36,000 mL·g... -1 ·h -1 Under stringent conditions of CH4 / CO2 = 1:1, the catalytic method exhibits CH4 to CO2 conversion rates close to the thermodynamic equilibrium limit, with an H2 / CO molar ratio approaching 1, and demonstrates extremely low activity decay during a long-term test of 150 h. Furthermore, the preparation method provided by this invention is simple, low-cost, and requires no precious metals, achieving a harmonious balance of high activity, high stability, and high resistance to carbon deposition. This provides a practical and high-performance catalytic solution for the industrial application of methane dry reforming to syngas technology. Attached Figure Description

[0019] Figure 1 Here is a SEM image of the catalyst prepared in Example 1 of this invention;

[0020] Figure 2 The XRD pattern of the catalyst prepared in Example 1 of this invention;

[0021] Figure 3 Here is a SEM image of the catalyst prepared in Example 2 of this invention;

[0022] Figure 4This is a SEM image of the catalyst prepared in Comparative Example 1 of the present invention.

[0023] Figure 5 The H2-TPR test results are for the catalysts prepared in Examples 1 to 2 and Comparative Example 1 of this invention.

[0024] Figure 6 The CO2-TPD results are for the catalyst prepared in Comparative Example 1 of this invention.

[0025] Figure 7 The CO2-TPD results are for the catalyst prepared in Example 2 of this invention.

[0026] Figure 8 The CO2-TPD results are for the catalyst prepared in Example 1 of this invention.

[0027] Figure 9 This is a schematic diagram of a fixed-bed continuous flow reactor used to test the application performance of the catalyst in greenhouse gas conversion in an application embodiment of the present invention.

[0028] Figure 10 The results of XPS O 1s for the catalyst prepared in Example 1 of this invention before and after the DRM reaction;

[0029] Figure 11 The XPS Ni 2p results of the catalyst prepared in Example 1 of this invention before and after the DRM reaction;

[0030] Figure 12 The XPS Cu 2p results of the catalyst prepared in Example 1 of this invention before and after the DRM reaction;

[0031] Figure 13 The above are Raman diagrams of the catalysts prepared in Examples 1 and 2 and Comparative Example 1 after the DRM reaction.

[0032] Figure 14 The CO2 conversion rate of the catalysts prepared in Examples 1 to 2 and Comparative Example 1 after 5 hours of DRM reaction is shown.

[0033] Figure 15 The CH4 conversion rate of the catalysts prepared in Examples 1 to 2 and Comparative Example 1 after 5 h of DRM reaction is given.

[0034] Figure 16 The H2 / CO ratio of the catalysts prepared in Examples 1 to 2 and Comparative Example 1 after 5 h of DRM reaction is shown.

[0035] Figure 17 The results of CO2 and CH4 conversion after 150 h of DRM reaction with the catalyst prepared in Example 1 of the present invention;

[0036] Figure 18 The H2 / CO ratio is the value of the catalyst prepared in Example 1 of this invention after undergoing a DRM reaction for 150 h. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0039] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0040] This invention provides a MgAl2O4-based high-entropy spinel catalyst, the chemical formula of which is: (Mg a Co b Nic C u d Cr e Al₂O₄, a+b+c+d+e=1, the mole fraction of each element is 0.1-0.4, and the optimal mole fraction ratio is Mg:Co:Ni:Cu:Cr =0.2:0.2:0.2:0.2:0.2.

[0041] Furthermore, the present invention also provides a method for preparing the above-mentioned high-entropy spinel catalyst, comprising the following steps:

[0042] According to the chemical formula of the high-entropy spinel catalyst, Mg source, Co source, Ni source, Cu source, Cr source and Al source are dissolved in water to obtain a precursor solution;

[0043] The precursor solution was subjected to ball milling and calcination in sequence to obtain the high-entropy spinel catalyst.

[0044] In some embodiments, the Mg source, Co source, Ni source, Cu source, Cr source, and Al source are soluble salts of various metals. Preferably, the Mg source is magnesium oxide, the Co source is cobalt monoxide, the Ni source is nickel monoxide, the Cu source is copper oxide, the Cr source is chromium oxide, and the Al source is aluminum oxide.

[0045] In some embodiments, the ball milling speed is 500-700 rpm, the ball milling time is 2-4 h, and the ball-to-material ratio is (4-6):1.

[0046] In some embodiments, the calcination treatment is carried out at a temperature of 900-1100°C for 8-12 hours.

[0047] Furthermore, this invention also provides the application of MgAl2O4-based high-entropy spinel catalysts in the dry reforming of methane, with the specific reaction conditions as follows: reaction temperature of 800℃, feed gas composition of CH4, CO2, and Ar, with a CH4 to CO2 volume ratio of 1:1, total gas flow rate of 300 mL / min, and space velocity of 36000 mL·g. -1 ·h -1 The reaction time is 0-150h.

[0048] The following specific embodiments further illustrate the MgAl2O4-based high-entropy spinel catalyst provided by the present invention, its preparation method, and its application in greenhouse gas conversion:

[0049] Example 1

[0050] This embodiment provides a method for preparing a MgAl2O4-based high-entropy spinel catalyst, comprising the following steps:

[0051] According to the chemical formula (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Cr 0.2 For Al2O4, weigh 1.612 g of magnesium oxide, 2.997 g of cobalt monoxide, 2.988 g of nickel monoxide, 3.182 g of copper oxide, 3.039 g of chromium oxide, and 20.392 g of aluminum oxide, dissolve them in 50 g of water, and pour the resulting mixture into a ball mill jar for ball milling. The ball-to-material ratio is 5:1, the rotation speed is 600 rpm, and the time is 4 hours. After ball milling, pour the liquid into a beaker and transfer it to an oven at 105℃ for drying. After drying, grind the sample into a fine powder of less than 100 mesh, and calcine it in a muffle furnace at 1000℃ for 10 hours. Then grind the calcined product into a fine powder of less than 100 mesh to obtain the dark green (Mg)2O4. 0.2 Co 0.2 Ni 0.2 Cu 0.2 Cr 0.2 Al2O4 powder. It should be noted that, unless otherwise specified, all reagents and raw materials used in the embodiments of this invention can be obtained commercially.

[0052] The (Mg) prepared in this embodiment 0.2 Co0.2 Ni 0.2 Cu 0.2 Cr 0.2 SEM image of Al2O4 catalyst as shown below Figure 1 As shown, the results indicate that the catalyst exhibits a porous aggregated morphology, with rough particle surfaces, fine and fragmented grains that are interconnected to form a three-dimensional network. The high-entropy effect significantly inhibits excessive grain growth while introducing abundant lattice defects and surface active sites. The XRD pattern of the catalyst is shown below. Figure 2 As shown in the figure, a series of sharp and high-intensity diffraction peaks are observed at positions such as 2θ ≈ 19.0°, 31.4°, 36.2°, 38.5°, 44.9°, 59.5° and 65.4°, which are highly consistent with the typical spinel structure, indicating that a single-phase spinel phase has been successfully prepared.

[0053] Example 2

[0054] This embodiment provides a method for preparing a MgAl2O4-based high-entropy spinel catalyst, comprising the following steps:

[0055] According to the chemical formula (Mg) 0.4 Co 0.2 Ni 0.2 Cr 0.2 For Al2O4, weigh out 3.224 g of magnesium oxide, 2.997 g of cobalt monoxide, 2.988 g of nickel monoxide, 3.039 g of chromium oxide, and 20.392 g of aluminum oxide, dissolve them in 50 g of water, and pour the resulting mixture into a ball mill jar for ball milling. The ball-to-material ratio is 5:1, the rotation speed is 600 rpm, and the time is 4 h. After ball milling, pour the liquid into a beaker and transfer it to an oven at 105℃ for drying. After drying, grind the sample into a fine powder of less than 100 mesh, and calcine it in a muffle furnace at 1000℃ for 10 h. Then grind the calcined product into a fine powder of less than 100 mesh to obtain the dark green (MgO) powder. 0.4 Co 0.2 Ni 0.2 Cr 0.2 )Al2O4 powder.

[0056] The (Mg) prepared in this embodiment 0.4 Co 0.2 Ni 0.2 Cr 0.2 SEM image of Al2O4 catalyst as shown below Figure 3 As shown, the results indicate that the catalyst exhibits a fine particle morphology with a porous surface and clear grain outlines, and the pore structure is increased compared to Example 1.

[0057] Comparative Example 1

[0058] The difference between this comparative example and Example 1 is that the catalyst was prepared according to the following steps:

[0059] Weigh out 8.867 g of magnesium oxide and 22.431 g of aluminum oxide, dissolve them in water, and pour the resulting mixture into a ball mill jar for ball milling. The ball-to-material ratio is 5:1, the rotation speed is 600 rpm, and the time is 4 h. After ball milling, pour the liquid into a beaker and transfer it to an oven at 105℃ for drying. After drying, grind the sample into fine powder below 100 mesh and calcine it in a muffle furnace at 1000℃ for 10 h. Then grind the calcined product into fine powder below 100 mesh to obtain milky white MgAl2O4 powder.

[0060] The SEM image of the MgAl2O4 powder prepared in this comparative example is shown below. Figure 4 As shown, the results indicate that the particles are large and have relatively rough surfaces, exhibiting a large, irregular blocky structure with significant agglomeration and a relatively low exposed specific surface area.

[0061] The H2-TPR test results of the catalysts prepared in Examples 1 and 2 and Comparative Example 1 are as follows: Figure 5 As shown, the results indicate that the samples of Examples 1-2 all exhibit significant H2 consumption peaks in the high-temperature region of 800-950°C, which clearly confirms that the active metal species are mainly embedded within the crystal lattice and have a strong interaction with the support. Comparing the three curves, it can be seen that with the increase of Mg content, the reduction peak shifts significantly towards higher temperatures, indicating that the thermodynamic stability of the crystal structure is enhanced. Conversely, the introduction of Cu significantly lowers the reduction temperature, effectively promoting the reduction of the Ni / Co active components; while Cr doping further shifts the reduction peak towards higher temperatures, indicating that it further strengthens the stability of the crystal framework. It is noteworthy that although the reduction peak intensity of the high-entropy sample is weaker than that of some single or binary systems, its main peak is still located in the high-temperature region above 800°C (the main peak of the high-entropy sample is about 847°C, and that of the Mg-containing system is about 953°C), indicating that the active metal species are still firmly bound in the crystal lattice. Therefore, this phenomenon of "lower reduction temperature" does not imply structural instability, but rather makes the reduction behavior of the material closer to the reaction temperature window of dry methane reforming (DRM), thus facilitating the in-situ generation of active metals during the reaction. In contrast, excessively high reduction temperatures can lead to insufficient activation of metal species under reaction conditions, while excessively low reduction temperatures may cause premature precipitation of metal particles and sintering. Thus, this high-entropy system successfully achieves synergistic optimization of catalytic activity and structural stability by precisely controlling the reduction temperature to an appropriate range, thereby exhibiting optimal catalytic performance.

[0062] The CO2-TPD results of the catalyst prepared in Comparative Example 1 are as follows: Figure 6As shown, the results indicate that the CO2-TPD curve exhibits typical broadening characteristics. There is an extremely strong desorption peak in the low-temperature region (120℃), corresponding to a large number of weakly basic sites on the surface. In contrast, only a weak shoulder peak was observed in the medium-high temperature region (300-450℃), indicating that it lacks moderately strong basic sites that can effectively dissociate CO2 molecules. This explains the inherent defect of low activity of pure magnesium aluminum spinel in the DRM reaction.

[0063] The CO2-TPD results of the catalyst prepared in Example 2 are as follows: Figure 7 As shown, the results indicate that when Ni, Co, and Cr are introduced to form a high-entropy configuration, the curve profile undergoes a significant evolution: the intensity of the strong peak in the low-temperature region decreases significantly, confirming that the introduction of the multi-metallic components reconstructs the surface chemical environment, leading to a sharp reduction in the number of weak adsorption sites; at the same time, the desorption peak area in the mid-temperature region (300-400℃) increases significantly and the peak shape becomes sharper, which is directly attributed to the severe lattice distortion and electronic structure regulation caused by high-entropy doping, which causes some originally inert weak basic sites to be transformed into medium-strength basic sites with high reactivity (such as specific MO pairs or oxygen vacancy neighborhoods), thereby significantly enhancing the material's ability to chemically adsorb and activate CO2.

[0064] The CO2-TPD results of the catalyst prepared in Example 1 are as follows: Figure 8 As shown, the results indicate that after further introducing Cu to construct a pentagonal high-entropy system, the desorption peak area in the mid-temperature region decreases with further dilution of Mg content. This is due to the replacement of the main basic structural unit, Mg-O, by transition metals. However, the peak position shifts significantly towards the high-temperature region (red shift), indicating that the adsorption strength (basic strength) of the remaining basic sites is greatly enhanced. This phenomenon of "reduced quantity but increased strength" stems from the more complex local coordination environment and multi-metal synergistic effect in the high-entropy system, which greatly enhances the adsorption of O on the surface. 2- The electron cloud density causes the CO2 adsorption mode to shift from weak / moderate bicarbonate species to more stable bidentate / bridged carbonate species. In summary, as the entropy increases, the basicity of the sample gradually evolves from "weakly basic dominant" to "increased proportion of high-intensity strong basicity," which is beneficial for improving the adsorption strength and activation capacity of CO2, thereby promoting the generation of surface reactive oxygen species and enhancing the carbon deposition oxidation capacity. However, it may also limit the overall reaction rate due to a decrease in the number of adsorption sites.

[0065] Application Examples

[0066] To investigate the application performance of the catalysts prepared in Examples 1 and 2 in greenhouse gas conversion, this section uses a fixed-bed continuous flow reactor to test the reaction performance of the catalysts in methane dry reforming. The test is divided into two processes: short-time performance testing and long-term stability testing, both of which are carried out using a fixed-bed continuous flow reactor.

[0067] Specifically, please refer to Figure 9 As shown, the fixed-bed continuous flow reactor includes a feed gas supply system, a mass flow control system, a fixed-bed quartz reactor, an electric heating furnace, and an online gas mass spectrometer. It is a standard device for gas-solid phase catalytic reactions in this field, so it will not be described in detail here.

[0068] The test conditions for short-term performance testing are as follows: the feed gas consists of high-purity CH4, CO2, and Ar (all with a purity >99.999%). During operation, 0.5 g of catalyst is thoroughly mixed with an appropriate amount of quartz sand and then packed into the center of the isothermal zone of a quartz reaction tube with an inner diameter of 10 mm. Quartz wool is laid at the bottom of the tube to support the bed. Subsequently, under Ar atmosphere protection, the temperature is increased to 800 °C at a rate of 10 °C / min. After the temperature stabilizes, the feed gas is switched to CH4 / CO2 / Ar (CH4 to CO2 volume ratio of 1:1, Ar as internal standard), and the total flow rate is controlled at 300 mL / min (corresponding to a space velocity of approximately 36000 mL·g). -1 ·h -1 The methane dry reforming reaction was carried out under normal pressure. After the tail gas was condensed and dehydrated, it entered an online mass spectrometer (SHP8400PMS-L) to detect the concentrations of CH4, CO2, H2 and CO in real time. Data was recorded every 30 min to calculate the CH4 conversion rate, CO2 conversion rate and H2 / CO molar ratio, thereby evaluating the short-term catalytic performance of the catalyst within 5 h.

[0069] The test conditions for long-term stability testing are as follows: 0.5 g of catalyst was weighed, uniformly mixed with quartz sand, and then loaded (to reduce local hot spots in the bed and improve gas mass transfer efficiency); under Ar atmosphere protection, the temperature was increased to 800℃ at 10℃ / min, and the feed gas was switched to CH4 / CO2 / Ar (the volume ratio of CH4 to CO2 was 1:1, the total flow rate was 300 mL / min, and the space velocity was approximately 36000 mL·g). -1 ·h -1 The reaction was carried out; the system was maintained at 800℃ and atmospheric pressure for 150 hours of continuous and stable operation. The composition of the gas outlet was detected every hour using online mass spectrometry, and the changes in CH4 conversion, CO2 conversion, and H2 / CO molar ratio were recorded in real time to verify the long-term stability of the catalyst. The apparatus used for the test was consistent with that used in the short-term test. The formula for calculating the CH4 conversion is as follows: The formula for calculating CO2 conversion rate is as follows: The formula for calculating the H2 / CO molar ratio is as follows: In the three formulas, F in F represents the inlet flow rate of the corresponding reactant. out This represents the outlet flow rate of the corresponding reactant.

[0070] The XPS O 1s results of the catalyst prepared in Example 1 before and after the DRM reaction are as follows: Figure 10 As shown, the results indicate that the O 1s spectrum of the catalyst before and after the DRM reaction can be decomposed into three characteristic peaks. The peak at approximately 530.3-530.4 eV is attributed to lattice oxygen, indicating that the sample bulk still maintains a relatively stable spinel oxide structure. The peak at approximately 530.9-531.1 eV corresponds to surface defect oxygen or adsorbed active oxygen species, which are usually closely related to oxygen vacancies and surface active sites. The weak peak at approximately 532.3-532.5 eV is attributed to surface adsorbed hydroxyl and water molecule species. Compared with before the reaction, the peak area of ​​adsorbed oxygen on the catalyst surface increased significantly after 5 hours of reaction, indicating that the surface oxygen mobility was enhanced and more oxygen vacancies were formed during the DRM process, which is beneficial to CO2 activation and carbon deposition oxidation. At the same time, the lattice oxygen peak decreased slightly, indicating that some lattice oxygen participated in the reaction process. As the reaction time was extended to 150 h, the proportion of adsorbed oxygen further increased, while the lattice oxygen peak remained strong. This indicates that the high-entropy spinel structure still has good structural stability and oxygen cycling ability under long-term high-temperature DRM conditions. This high surface active oxygen content and stable lattice oxygen reserve help to promote the timely removal of carbon species after CH4 cracking, thereby improving the catalyst's anti-carbon deposition performance and long-term stability.

[0071] The XPS Ni 2p results of the catalyst prepared in Example 1 before and after the DRM reaction are as follows: Figure 11 As shown, the results indicate that Ni is the main component present in the catalyst before the reaction. 2+ Species, whose Ni 2p 3 / 2 The main peak is located at approximately 855-856 eV, while a distinct satellite peak exists around 861 eV, which is typical for Ni. 2+ The characteristic oxidation state indicates that Ni in the catalyst before the reaction mainly exists in the oxidation state form within the spinel lattice. After the DRM reaction, new Ni appears at approximately 852-853 eV. 0 Characteristic peaks indicate that some Ni 2+ Under a high-temperature reducing atmosphere, it is in situ reduced to the active sites of metallic Ni. Meanwhile, Ni... 2+ The peaks remained at high intensity, indicating that some Ni still maintained strong interactions with the spinel framework after the reaction, suggesting strong MSI in the system. Compared to the sample after 5 h of reaction, the sample after 150 h showed higher Ni content. 0 The peak further intensifies, while Ni 2+The peak slightly weakens, indicating that as the reaction time increases, more surface Ni species gradually precipitate and transform into metallic Ni. It is noteworthy that even after a long DRM reaction, Ni... 2+ The presence of satellite peaks indicates that the high-entropy spinel structure has not completely collapsed and can still stabilize some Ni species, thereby inhibiting severe sintering of metal particles. This "partial reduction-partial anchoring" state is beneficial for improving the long-term stability and anti-carbon deposition performance of the catalyst while maintaining a high CH4 activation capacity.

[0072] The XPS Cu 2p results of the catalyst prepared in Example 1 before and after the DRM reaction are as follows: Figure 12 As shown, the results indicate that in the catalyst before the reaction, Cu 2p 3 / 2 The main peak is located at 934.1 eV, accompanied by characteristic satellite peaks at 940.4 eV and 961.2 eV, which are characteristic of Cu in the spinel lattice. 2+ Typical characteristics. After 5 h or even 150 h of the DRM reaction, the Cu 2p of the catalyst... 3 / 2 The main peak remains stable at 934.2-934.4 eV, and satellite peaks (941-944 eV and 963 eV) are still prominent, although some weak components appear in the lower binding energy region, suggesting the presence of a small amount of reduced Cu species (Cu). + / Cu 0 ), but Cu 2+ The dominant valence state remains, indicating that the strong metal-support interaction and configuration entropy stabilization effect in the high-entropy spinel structure effectively suppress the complete reduction and sintering of Cu under a long-term reducing DRM reaction atmosphere.

[0073] The Raman spectroscopy diagrams of the catalysts prepared in Examples 1 and 2 and Comparative Example 1 after the DRM reaction are shown below. Figure 13 As shown, the results indicate that I after 5 hours of reaction with MgAl2O4 G / I D The value is 0.67, indicating the presence of a certain amount of disordered carbon; (Mg 0.4 Ni 0.2 Co 0.2 Cr 0.2 I after Al2O4 reaction for 5 hours G / I D The value is 2.28, indicating a high degree of graphitization; (Mg 0.4 Ni 0.2 Co 0.2 Cu 0.2 I after Al2O4 reaction for 5 hours G / I D The coefficient of performance (C-doping) dropped to 1.09, indicating that Cu doping effectively suppressed the ordering of carbon; the high-entropy catalyst (Co-doping) 0.2 Ni0.2 Mg 0.2 Cu 0.2 Cr 0.2 I after Al2O4 reaction for 5 hours G / I D The value was 1.47, indicating moderate performance, while its response time was 150 hours later. G / I D The carbon content was only 0.42 (the lowest), indicating a very weak carbon signal and predominantly highly disordered carbon. Ni-based and Ni-Co systems tend to generate highly graphitized carbon after 5 hours of reaction, while Cu doping can reduce the degree of graphitization. High-entropy spinel, on the other hand, exhibited extremely strong resistance to carbon deposition during long-term operation (150 hours), effectively suppressing carbon accumulation and maintaining carbon in a disordered state that is easily vaporized by CO2. This is closely related to the abundant oxygen vacancies and synergistic effect brought about by the high-entropy effect.

[0074] The CO2 conversion rates of the catalysts prepared in Examples 1 and 2 and Comparative Example 1 after 5 hours of DRM reaction are as follows: Figure 14 As shown, the CH4 conversion rates of the catalysts prepared in Examples 1 to 2 and Comparative Example 1 after 5 hours of DRM reaction are as follows: Figure 15 As shown, the H2 / CO ratios of the catalysts prepared in Examples 1 to 2 and Comparative Example 1 after 5 hours of DRM reaction are as follows: Figure 16 As shown.

[0075] Specifically Figure 14 The results showed significant differences among different catalysts during the 5-hour DRM reaction. MgAl₂O₄ exhibited low CO₂ conversion, which rapidly decreased and stabilized over time (15-20%), indicating almost no effective DRM activity, primarily due to a lack of metal active sites capable of activating CH₄ / CO₂. In contrast, the introduction of Ni-based multimetals significantly improved catalytic performance. The low-entropy sample showed a high initial conversion rate, but with a certain induction period, gradually stabilizing at around 90%. As the system complexity (entropy configuration) increased, the multi-element high-entropy catalyst exhibited superior performance, with its CO₂ conversion rate rapidly increasing to near thermodynamic equilibrium (95-100%) and remaining stable. This indicates that the multimetal synergistic effect enhanced CO₂ adsorption and activation capabilities while suppressing the deactivation process.

[0076] Figure 15The results show that the CH4 conversion rate trend is consistent with that of CO2. MgAl2O4 has almost no CH4 activation ability, and its conversion rate drops rapidly to an extremely low level (<5%), indicating a lack of metal active centers. After the introduction of Ni, the low-entropy samples exhibited higher initial activity (60-85%), but also tended to stabilize after a brief activation phase. The high-entropy catalyst maintained a CH4 conversion rate close to 100% throughout the entire reaction process with minimal fluctuations, demonstrating extremely strong CH bond activation ability and excellent stability. In addition, some medium-entropy samples showed a slow upward trend over time (approximately 30%→50%), further confirming the gradual exposure of active sites during the reaction. The high-entropy structure enhances metal dispersion and anti-sintering ability, while promoting in-situ gasification of carbon deposits, enabling the catalyst to achieve a synergistic balance of high activity and high stability in a short period of time.

[0077] Figure 16 The results show that Comparative Example 1 (MgAl2O4), an undoped quaternary spinel, has the lowest H2 / CO ratio, at only 0.33947, significantly lower than 1.0. This indicates that it has undergone severe carbon deposition side reactions, resulting in excessive consumption of hydrogen or conversion of carbon monoxide. This is a direct manifestation of the single active site and weak anti-carbon deposition ability of pure magnesium aluminum spinel. In contrast, the five-element spinel catalyst with the introduction of Co, Ni, Cu, and Cr multi-element transition metals showed significant performance improvement: the H2 / CO ratio of Example 2 was the highest, reaching 1.08986, while that of Example 1 was 1.04715. Both are close to the ideal stoichiometric ratio of methane dry reforming (H2 / CO ≈ 1), which indicates that promoting CO2 activation and carbon deposition gasification (C + CO2 → 2CO) enables the synergistic generation of H2 and CO, making the system closer to the ideal DRM reaction pathway. Furthermore, the high magnesium content (Example 2) further enhanced the activity and migration ability of lattice oxygen, thereby significantly inhibiting carbon deposition and improving the catalyst's resistance to sintering and deactivation.

[0078] The catalyst (Co) prepared in Example 1 0.2 Ni 0.2 Mg 0.2 Cu 0.2 Cr 0.2 The CO2 and CH4 conversion results after Al2O4 underwent DRM reaction for 150 h are as follows: Figure 17 As shown, the H2 / CO ratio is as follows: Figure 18As shown in the figure, the conversion rates of CH4 and CO2 remained above approximately 95% and 94%, respectively, and increased slightly with reaction time, indicating that the catalyst underwent a certain structural activation process during the reaction. Meanwhile, the H2 / CO ratio of the products remained close to the theoretical value of 1, indicating that the reaction was mainly controlled by the main reaction of methane dry reforming, with minimal impact from side reactions. No significant deactivation was observed during long-term operation, demonstrating that this high-entropy spinel catalyst possesses excellent resistance to sintering and carbon deposition. This is mainly attributed to the multi-metal synergistic effect and the stability and abundant surface active sites brought about by the high-entropy structure.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A MgAl2O4-based high-entropy spinel catalyst, characterized in that, Its chemical formula is: (Mg a Co b Ni c Cu d Cr e Al₂O₄, a+b+c+d+e=1, the mole fractions of Mg, Co, Ni, Cu, and Cr are 0.1-0.

4.

2. The MgAl2O4-based high-entropy spinel catalyst according to claim 1, characterized in that, The molar ratio of Mg, Co, Ni, Cu, and Cr is 0.2:0.2:0.2:0.2:0.

2.

3. A method for preparing a MgAl2O4-based high-entropy spinel catalyst as described in claim 1 or 2, characterized in that, Includes the following steps: According to the chemical formula of the high-entropy spinel catalyst, Mg source, Co source, Ni source, Cu source, Cr source and Al source are dissolved in water to obtain a precursor solution; The precursor solution was subjected to ball milling and calcination in sequence to obtain a high-entropy spinel catalyst.

4. The preparation method according to claim 3, characterized in that, The ball milling process is performed at a speed of 500-700 rpm, a milling time of 2-4 hours, and a ball-to-material ratio of (4-6):

1.

5. The preparation method according to claim 3, characterized in that, The calcination treatment is carried out at a temperature of 900-1100℃ for 8-12 hours.

6. The preparation method according to claim 4, characterized in that, The ball milling process was carried out at a rotation speed of 600 rpm, a milling time of 4 hours, and a ball-to-material ratio of 5:

1.

7. The preparation method according to claim 5, characterized in that, The calcination treatment was carried out at a temperature of 1000℃ for 10 hours.

8. The application of a MgAl2O4-based high-entropy spinel catalyst prepared by the preparation method according to any one of claims 3-7 in greenhouse gas conversion.

9. The application of a MgAl2O4-based high-entropy spinel catalyst prepared by the preparation method according to any one of claims 3-7 in the dry reforming of methane, characterized in that, The reaction conditions for the methane dry reforming are as follows: reaction temperature is 800℃, feed gas composition is CH4, CO2, and Ar, with a CH4 to CO2 volume ratio of 1:1, total gas flow rate is 300 mL / min, and space velocity is 36000 mL·g. -1 ·h -1 .

10. The application according to claim 9, characterized in that, The reaction time for the methane dry reforming is 0-150 h.

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