A catalyst for reverse water gas shift reaction and a method for preparing the same

Abstract

The present application relates to the technical field of reverse water gas shift reaction, and discloses a preparation method of a catalyst for reverse water gas shift reaction, comprising the following steps: weighing magnesium nitrate and zinc acetate, so that the molar ratio of Mg atoms to Zn atoms is 1:1 to 1:10 or 3:1 to 10:1; dissolving the weighed magnesium nitrate and zinc acetate in water, adding urea, stirring and uniformly mixing at room temperature, and then increasing the temperature and stirring to promote the co-precipitation of metal ions; and obtaining the MgO-ZnO composite oxide catalyst by centrifugation, washing, drying and calcination of the obtained precipitate. The MgO-ZnO composite oxide catalyst is prepared by adopting the urea uniform precipitation method, using magnesium nitrate and zinc acetate as raw materials, and precisely controlling the molar ratio of Mg to Zn.

Description

Technical Field

[0001] This invention relates to the field of reverse water gas shift reaction technology, and in particular to a catalyst for reverse water gas shift reaction and its preparation method. Background Technology

[0002] Against the backdrop of the ongoing "dual-carbon" strategic goals, converting massive amounts of carbon dioxide into high-value-added chemicals or fuels has become crucial for achieving carbon resource recycling. The reverse water-gas shift reaction can convert carbon dioxide and green hydrogen into carbon monoxide and water, and its syngas product is an indispensable raw material for modern coal chemical and natural gas chemical processes such as Fischer-Tropsch synthesis and methanol synthesis. Therefore, this technology is considered one of the most promising pathways for achieving large-scale resource utilization of carbon dioxide.

[0003] However, the development of catalysts for reverse water-gas shift reactions still faces significant challenges. While noble metal catalysts (such as Pt, Pd, and Ru) possess excellent catalytic performance, their high cost hinders large-scale industrial application. Traditional copper-based catalysts, although lower in cost, suffer from poor thermal stability and are prone to sintering and deactivation under high-temperature reaction conditions, limiting their application in high-temperature environments. Iron-based catalysts are prone to side reactions, resulting in unsatisfactory selectivity for the target product, carbon monoxide.

[0004] Furthermore, in existing technologies, such as the catalyst disclosed in Chinese Patent No. CN117380176B, a spinel structure is formed by combining divalent metal ions (Mg, Zn) and trivalent metal ions (Al, In, Ga). Although it achieves certain catalytic activity, its composition is complex, and it must rely on the introduction of trivalent metals to stabilize the structure. Another example is the catalyst disclosed in Chinese Patent No. CN118477652B, which uses the sol-gel method to prepare MoCe, MoTi, or MoGa supports, and then co-precipitates copper. While this achieves high CO selectivity, its preparation process is cumbersome and involves multiple metals such as molybdenum, cerium, titanium, and gallium, resulting in high costs.

[0005] Therefore, developing a non-precious metal reverse water-gas shift catalyst that combines high activity, high selectivity, excellent stability, and low cost is crucial for promoting the industrial application of this technology. This invention focuses on a low-cost non-precious metal MgO-ZnO composite oxide catalyst. By optimizing the molar ratio of Mg to Zn and using a urea homogeneous precipitation method, it effectively solves the problems of insufficient activity and poor stability of traditional catalysts, providing a new solution for the industrial application of reverse water-gas shift technology. Summary of the Invention

[0006] To address the technical problems mentioned in the background section, this invention provides a catalyst for reverse water-gas shift reaction and its preparation method.

[0007] This invention is achieved using the following technical solution: A method for preparing a catalyst for a reverse water-gas shift reaction, comprising the following steps: Weigh out magnesium nitrate and zinc acetate to make the molar ratio of Mg atoms to Zn atoms 1:1 to 1:10 or 3:1 to 10:1; Magnesium nitrate and zinc acetate were weighed and dissolved in water. Urea was added, and the mixture was stirred at room temperature. Then, the temperature was raised and stirred to promote the co-precipitation of metal ions. The precipitate was centrifuged, washed, dried, and calcined to obtain the MgO-ZnO composite oxide catalyst.

[0008] Preferably, the heating and stirring conditions are: heating to 90°C and stirring at a constant temperature for 6 hours.

[0009] Preferably, the molar ratio of Mg atoms to Zn atoms is 1:2 to 1:5.

[0010] Preferably, the molar ratio of Mg atoms to Zn atoms is 1:3.

[0011] Preferably, the molar ratio of urea to the total amount of Mg and Zn is 4:1.

[0012] Preferably, the washing includes washing with deionized water and anhydrous ethanol.

[0013] Preferably, the drying conditions are: temperature 60°C, time 12 hours.

[0014] Preferably, the calcination conditions are: calcination at 600°C for 2 hours with a heating rate of 5°C / min.

[0015] This invention also proposes a catalyst for reverse water-gas shift reaction, which is prepared by the above method; The catalyst is a composite oxide formed by MgO and ZnO, wherein the molar ratio of Mg atoms to Zn atoms is 1:1 to 1:10 or 3:1 to 10:1.

[0016] Preferably, the molar ratio of Mg atoms to Zn atoms is 1:3.

[0017] Preferably, in the lattice structure of the catalyst, the same nanoparticle simultaneously contains lattice stripes corresponding to the (101) crystal plane of ZnO and lattice stripes corresponding to the (111) crystal plane of MgO.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes a urea homogeneous precipitation method, employing magnesium nitrate and zinc acetate as raw materials, to precisely control the molar ratio of Mg to Zn (especially Mg:Zn = 1:3), thus preparing a MgO-ZnO composite oxide catalyst. This method achieves highly homogeneous composite formation of Mg and Zn at the atomic level, resulting in a high-density heterogeneous interface and even a solid solution structure, thereby producing a significant synergistic effect: on the one hand, the strongly basic sites provided by MgO can efficiently adsorb and activate CO2; on the other hand, the redox sites provided by ZnO facilitate the dissociation of H2. The synergistic effect of these two factors significantly improves the catalytic reaction efficiency.

[0019] The results show that the catalyst exhibits excellent comprehensive performance in the reverse water-gas shift reaction: under reaction conditions of 600°C, the CO2 conversion rate can reach 31.5%, which is much higher than that of pure MgO or pure ZnO components, and the CO selectivity is as high as 100%, completely avoiding the interference of side reactions; at the same time, after continuous reaction at 600°C for 500 hours, the CO2 conversion rate decreases by less than 2.5%, and the CO selectivity remains at 100%, demonstrating excellent anti-sintering and anti-deactivation stability.

[0020] Furthermore, the urea uniform precipitation method used in this invention does not require complex equipment or strict pH control, and achieves simultaneous precipitation of bimetallic ions in one step. The process is simple and low-cost, and the catalyst contains only three elements: Mg, Zn, and O, making it green and environmentally friendly. It is very suitable for large-scale industrial production and provides a non-precious metal catalyst solution for reverse water-gas shift reaction that combines high activity, high selectivity, excellent stability, and low cost. Attached Figure Description

[0021] Figure 1 The X-ray diffraction (XRD) spectra of the catalysts in Example 2 and Comparative Examples 1-2 of this invention are shown below. Figure 2 This is a comparison chart of the CO2 conversion rates of the catalysts in Examples 1-7 and Comparative Examples 1-7 of the present invention at a reaction temperature of 600°C. Figure 3 This is a comparison chart of the catalytic stability test results of the catalyst in Example 2 (Mg1Zn3O) and the catalyst in Comparative Example 1 (pure MgO) after continuous reaction at a reaction temperature of 600°C for 500 hours. Figure 4 This is a high-resolution transmission electron microscope (HRTEM) image (scale bar is 5 nm) of the Mg1Zn3O catalyst prepared in Example 2 of the present invention. Figure 5a The image shows a transmission electron microscope (TEM) image (scale bar is 50 nm) of the Mg1Zn3O catalyst prepared in Example 2 of this invention. Figure 5b This is a histogram of particle size distribution. Figure 6 The image shows a scanning electron microscope (SEM) image (scale bar 500 nm) of the pure ZnO catalyst prepared in Comparative Example 2 of this invention, which shows that the pure ZnO has a particulate morphology and exhibits a certain degree of agglomeration. Figure 7 The image shows a scanning electron microscope (SEM) image (scale bar 100 nm) of the pure ZnO catalyst prepared in Comparative Example 2 of this invention, further revealing the particle morphology characteristics of pure ZnO, with relatively clear particle edges; Figure 8 The scanning electron microscope (SEM) image (scale bar 500 nm) of the Mg1Zn3O catalyst prepared in Example 2 of the present invention shows that, compared with pure ZnO, the Mg1Zn3O catalyst has smaller particle size, more uniform distribution, and more rounded particle edges. Figure 9 The scanning electron microscope (SEM) (scale bar 100 nm) of the Mg1Zn3O catalyst prepared in Example 2 of the present invention shows that it has a uniform particle distribution and good dispersibility, and the particles exhibit different degrees of mutual adhesion. Figure 10 The scanning electron microscope (SEM) (scale bar 500 nm) of the Mg1Zn5O catalyst prepared in Example 3 of the present invention shows that when the Zn content increases to Mg:Zn=1:5, the catalyst particle size increases, but still maintains the nanoparticle morphology. Figure 11 The scanning electron microscope (SEM) (scale bar 100 nm) of the Mg1Zn5O catalyst prepared in Example 3 of the present invention shows the morphological characteristics of the Mg1Zn5O catalyst, with rounded particle edges and a dense aggregated state. Figure 12 Comparison of X-ray photoelectron spectroscopy (XPS) O1s spectra of the catalysts of Comparative Example 1 (MgO), Comparative Example 2 (pure ZnO), Example 2 (Mg1Zn3O), and Example 3 (Mg1Zn5O) of this invention; Figure 13 The image shows the micro-region morphology of the Mg1Zn3O catalyst prepared in Example 2 of this invention for energy dispersive X-ray spectroscopy (EDS) analysis, illustrating the micro-morphology of the analyzed sample region. Figure 14 The EDS elemental distribution diagram (magnesium element, Mg Kα1,2 signal) of the Mg1Zn3O catalyst prepared in Example 2 of the present invention shows that the Mg element is uniformly distributed in the catalyst particles. Figure 15 The EDS elemental distribution diagram (oxygen element, O Kα1,2 signal) of the Mg1Zn3O catalyst prepared in Example 2 of the present invention shows that the O element is uniformly distributed in the catalyst particles. Figure 16The EDS elemental distribution diagram (zinc element, Zn Kα1,2 signal) of the Mg1Zn3O catalyst prepared in Example 2 of the present invention shows that the Zn element is uniformly distributed in the catalyst particles. Figure 17 The EDS elemental distribution diagram (Mg, O, Zn elements superimposed) of the Mg1Zn3O catalyst prepared in Example 2 of the present invention shows that the bright spots of Mg (cyan) and Zn (purple-red) are densely and uniformly distributed, and the two are highly overlapping in space. Detailed Implementation

[0022] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0023] Reference Figures 1-17 The following describes the scheme in detail with reference to Examples 1-7 and Comparative Examples 1-7: Example 1 In this embodiment, the preparation method of the Mg1Zn1O catalyst is as follows: 2.56 g of magnesium nitrate hexahydrate, 2.20 g of zinc acetate dihydrate (Mg to Zn molar ratio 1:1) and 4.80 g of urea (urea to total metal ion molar ratio 4:1) were weighed and dissolved in 100 mL of deionized water. The mixture was stirred at room temperature for 1 hour to achieve homogeneity. The temperature was raised to 90℃ and stirred at a constant temperature for 6 hours, during which the urea decomposed and promoted the co-precipitation of metal ions. After cooling and standing for 1 hour, the precipitate was centrifuged, washed with deionized water and anhydrous ethanol, and dried at 60℃ for 12 hours to obtain the precursor. Finally, the precursor was calcined at 600℃ at a rate of 5℃ / min for 2 hours to obtain the Mg1Zn1O catalyst.

[0024] Example 2 In this embodiment, the preparation method of the Mg1Zn3O catalyst is as follows: 0.85 g of magnesium nitrate hexahydrate, 2.20 g of zinc acetate dihydrate (Mg to Zn molar ratio 1:3) and 3.20 g of urea are weighed and dissolved in 100 mL of deionized water. The mixture is stirred at room temperature for 1 hour to achieve homogeneity. The temperature is raised to 90℃ and stirred at a constant temperature for 6 hours, causing the urea to decompose and promote the co-precipitation of metal ions. After cooling and standing for 1 hour, the precipitate is centrifuged, washed with deionized water and anhydrous ethanol, and dried at 60℃ for 12 hours to obtain the precursor. Finally, the precursor is calcined at 600℃ at a rate of 5℃ / min for 2 hours to obtain the Mg1Zn3O catalyst.

[0025] Example 3 In this embodiment, the preparation method of the Mg1Zn5O catalyst is as follows: 0.44 g of magnesium nitrate hexahydrate, 2.20 g of zinc acetate dihydrate (Mg to Zn molar ratio 1:5) and 2.88 g of urea are weighed and dissolved in 100 mL of deionized water. The mixture is stirred at room temperature for 1 hour to achieve homogeneity. The temperature is raised to 90℃ and stirred at a constant temperature for 6 hours, causing the urea to decompose and promote the co-precipitation of metal ions. After cooling and standing for 1 hour, the precipitate is centrifuged, washed with deionized water and anhydrous ethanol, and dried at 60℃ for 12 hours to obtain the precursor. Finally, the precursor is calcined at 600℃ at a rate of 5℃ / min for 2 hours to obtain the Mg1Zn5O catalyst.

[0026] Example 4 In this embodiment, Mg1Zn 10 The preparation method of the O catalyst is as follows: 0.26 g of magnesium nitrate hexahydrate, 2.20 g of zinc acetate dihydrate (Mg to Zn molar ratio 1:10), and 2.64 g of urea were weighed and dissolved in 100 mL of deionized water. The mixture was stirred at room temperature for 1 hour to achieve homogeneity. The temperature was raised to 90℃ and stirred at a constant temperature for 6 hours. The decomposition of urea promoted the co-precipitation of metal ions. After cooling and standing for 1 hour, the precipitate was centrifuged, washed with deionized water and anhydrous ethanol, and dried at 60℃ for 12 hours to obtain the precursor. Finally, the precursor was calcined at 600℃ at a rate of 5℃ / min for 2 hours to obtain Mg1Zn. 10 O catalyst Example 5 In this embodiment, the preparation method of the Mg3Zn1O catalyst is as follows: 2.56 g of magnesium nitrate hexahydrate, 0.73 g of zinc acetate dihydrate (Mg to Zn molar ratio 3:1) and 3.20 g of urea are weighed and dissolved in 100 mL of deionized water. The mixture is stirred at room temperature for 1 hour to achieve homogeneity. The temperature is raised to 90℃ and stirred at a constant temperature for 6 hours, causing the urea to decompose and promote the co-precipitation of metal ions. After cooling and standing for 1 hour, the precipitate is centrifuged, washed with deionized water and anhydrous ethanol, and dried at 60℃ for 12 hours to obtain the precursor. Finally, the precursor is calcined at 600℃ at a rate of 5℃ / min for 2 hours to obtain the Mg3Zn1O catalyst.

[0027] Example 6 In this embodiment, the preparation method of the Mg5Zn1O catalyst is as follows: 2.56 g of magnesium nitrate hexahydrate, 0.44 g of zinc acetate dihydrate (Mg to Zn molar ratio 5:1), and 2.88 g of urea are weighed and dissolved in 100 mL of deionized water. The mixture is stirred at room temperature for 1 hour to achieve homogeneity. The temperature is raised to 90℃ and stirred at a constant temperature for 6 hours, causing the urea to decompose and promote the co-precipitation of metal ions. After cooling and standing for 1 hour, the precipitate is centrifuged, washed with deionized water and anhydrous ethanol, and dried at 60℃ for 12 hours to obtain the precursor. Finally, the precursor is calcined at 600℃ at a rate of 5℃ / min for 2 hours to obtain the Mg5Zn1O catalyst.

[0028] Example 7 In this embodiment, Mg 10 The preparation method of Zn1O catalyst is as follows: 2.56 g of magnesium nitrate hexahydrate, 0.22 g of zinc acetate dihydrate (Mg to Zn molar ratio 10:1), and 2.64 g of urea were weighed and dissolved in 100 mL of deionized water. The mixture was stirred at room temperature for 1 hour to achieve homogeneity. The temperature was raised to 90℃ and stirred for 6 hours, during which the urea decomposed and promoted the co-precipitation of metal ions. After cooling and standing for 1 hour, the precipitate was centrifuged, washed with deionized water and anhydrous ethanol, and dried at 60℃ for 12 hours to obtain the precursor. Finally, the precursor was calcined at 600℃ at a rate of 5℃ / min for 2 hours to obtain Mg1O catalyst. 10 Zn1O catalyst.

[0029] Comparative Example 1 In this comparative example, the preparation method of pure MgO catalyst was as follows: 2.56 g of magnesium nitrate hexahydrate and 2.40 g of urea were weighed and dissolved in 100 mL of deionized water. The mixture was stirred at room temperature for 1 hour to achieve homogeneity. The temperature was raised to 90℃ and stirred at a constant temperature for 6 hours, during which the urea decomposed and precipitated magnesium ions. After cooling and standing for 1 hour, the precipitate was centrifuged, washed with deionized water and anhydrous ethanol, and dried at 60℃ for 12 hours to obtain the precursor. Finally, the precursor was calcined at 600℃ for 2 hours at a rate of 5℃ / min to obtain pure MgO catalyst.

[0030] Comparative Example 2 In this comparative example, the preparation method of pure ZnO catalyst was as follows: 2.20 g of zinc acetate dihydrate and 2.40 g of urea were weighed and dissolved in 100 mL of deionized water. The mixture was stirred at room temperature for 1 hour to achieve homogeneity. The temperature was raised to 90℃ and stirred at a constant temperature for 6 hours, during which the urea decomposed and precipitated zinc ions. After cooling and standing for 1 hour, the precipitate was centrifuged, washed with deionized water and anhydrous ethanol, and dried at 60℃ for 12 hours to obtain the precursor. Finally, the precursor was calcined at 600℃ for 2 hours at a rate of 5℃ / min to obtain pure ZnO catalyst.

[0031] Comparative Example 3 In this comparative example, Mg1Zn3O （浸）The catalyst was prepared as follows: 2.56 g of magnesium nitrate hexahydrate and 2.40 g of urea were dissolved in 100 mL of deionized water and stirred at room temperature for 1 hour to mix. The mixture was then heated to 90℃ and stirred for 6 hours, causing the urea to decompose and precipitate magnesium ions. After cooling and standing for 1 hour, the precipitate was centrifuged, washed with deionized water and anhydrous ethanol, and dried at 60℃ for 12 hours to obtain the precursor. Finally, the precursor was calcined at 600℃ for 2 hours at a rate of 5℃ / min to obtain pure MgO catalyst. 2.20 g of zinc acetate dihydrate was weighed and dissolved in 5 mL of deionized water. After ultrasonic oscillation for 0.5 hours, the mixed solution was slowly added dropwise to 1.0 g of the prepared MgO support using an impregnation method. The precursor was then dried at 60℃ for 12 hours. The resulting precursor was placed in a muffle furnace and calcined at 600℃ for 2 hours at a rate of 5℃ / min to finally obtain Mg1Zn3O. （浸） catalyst.

[0032] Comparative Example 4 In this comparative example, Mg1Zn3O （混合） The catalyst was prepared as follows: MgO and ZnO prepared according to Comparative Examples 1 and 2 were mechanically mixed at a molar ratio of 1:3 and placed in a mortar. The mixture was then manually and mechanically ground for 1 hour to ensure thorough and uniform mixing, ultimately yielding Mg1Zn3O. （混合） catalyst.

[0033] Comparative Example 5 In this comparative example, Mg1Zn3O （水热） The catalyst was prepared as follows: 0.85 g of magnesium nitrate hexahydrate, 2.20 g of zinc acetate dihydrate, and 3.20 g of urea were weighed and dissolved in 80 mL of deionized water. The solution was stirred at room temperature for 1 hour to form a homogeneous precursor solution. The solution was transferred to a 100 mL stainless steel hydrothermal reactor lined with polytetrafluoroethylene, sealed, and placed in an oven at 120 °C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The resulting precipitate was centrifuged, washed with deionized water and anhydrous ethanol, and dried at 60 °C for 12 hours to obtain the precursor. Finally, the precursor was calcined at 600 °C for 2 hours at a rate of 5 °C / min to obtain Mg1Zn3O. （水热） catalyst.

[0034] Comparative Example 6 In this comparative example, Mg1Zn3O （滴定）The catalyst was prepared as follows: 0.85 g of magnesium nitrate hexahydrate, 2.20 g of zinc acetate dihydrate, and 3.20 g of urea were dissolved in 100 mL of deionized water to prepare a mixed salt solution with a total metal ion concentration of 0.2 M. This solution is designated as solution A. 100 mL of 0.4 M ammonium carbonate solution was measured as a precipitant and designated as solution B. Under continuous stirring, solution B was slowly added dropwise to solution A using a constant flow pump, controlling the dropping rate to maintain the pH of the mixed solution at a stable level of 10.0 ± 0.2. After the addition was complete, the resulting slurry was aged in a water bath at 70 °C for 3 hours. After the reaction was completed, the mixture was filtered and repeatedly washed with deionized water until the filtrate was neutral, then washed twice with anhydrous ethanol. The resulting solid was dried at 100 °C for 12 hours to obtain the catalyst precursor. Finally, the precursor was placed in a muffle furnace and heated to 600℃ at a rate of 5℃ / min, and calcined for 4 hours to obtain Mg1Zn3O. （滴定） catalyst.

[0035] Comparative Example 7 In this comparative example, Mg1Zn3O （溶胶） The catalyst was prepared as follows: 0.85 g of magnesium nitrate hexahydrate and 2.20 g of zinc acetate dihydrate were weighed and dissolved in a mixed solvent of 50 mL deionized water and 20 mL anhydrous ethanol. The solution was stirred at room temperature for 0.5 hours to form a homogeneous solution. Under vigorous stirring, 2 mL of citric acid (citric acid to total metal ions molar ratio of 1:1) was slowly added dropwise as a complexing agent to the above solution. Subsequently, the mixed solution was continuously stirred and slowly evaporated in a 70°C water bath until a viscous sol was formed. The solution was then allowed to stand for 12 hours to obtain a transparent gel. The obtained gel was dried at 100°C for 12 hours, and then calcined at 600°C at a rate of 5°C / min for 4 hours to obtain Mg1Zn3O. （溶胶） catalyst.

[0036] In this embodiment, the catalyst characterization results are as follows: 1. Transmission electron microscopy (TEM) analysis TEM analysis was performed on the Mg1Zn3O catalyst prepared in Example 2, and the results are as follows: Figure 4 and Figure 5a As shown.

[0037] Reference Figure 4By comparing with the standard PDF card, 0.245 nm belongs to the (101) crystal plane of ZnO, while 0.243 nm belongs to the (111) crystal plane of MgO. Both lattice fringes coexist in the same nanoparticle, with no obvious interface defects or amorphous regions, forming a tight MgO-ZnO heterostructure. This interface structure is considered key to the high activity of the RWGS reaction: the strongly basic sites of MgO are responsible for CO2 adsorption and activation, while the redox sites of ZnO are responsible for H2 dissociation; the two work together to complete the reaction at the interface. TEM images show that the particles are irregularly shaped blocks or polyhedra with relatively clear edges, showing no obvious signs of agglomeration or sintering; larger particles are more conducive to thermal stability. The redox sites of O are responsible for H2 dissociation; the two work together to complete the reaction at the interface.

[0038] Figure 5a The data shows that the catalyst particles are nanoscale in size, have a relatively uniform morphology, and show no obvious agglomeration. Figure 5b The particle size distribution histogram shows that the average particle diameter is 47.70 nm, the standard deviation is 11.15 nm, and the particle size is concentrated in the range of 30–65 nm. The particle size exhibits a narrow normal distribution, with no obvious ultrafine particles or large-sized agglomerates. These nanoscale particles can provide a large specific surface area and abundant surface active sites, which is beneficial for the adsorption of reactants and the desorption of products, thereby improving the catalytic performance of the reverse water-gas shift reaction.

[0039] 2. Scanning electron microscopy (SEM) analysis SEM analysis was performed on the pure ZnO catalyst prepared in Comparative Example 2, and the results are as follows: Figure 6 (Scale bar 500 nm) and Figure 7 As shown in the scale bar (100 nm), pure ZnO exhibits a granular morphology with a certain degree of agglomeration and relatively clear particle edges.

[0040] The Mg1Zn3O catalyst prepared in Example 2 was analyzed by SEM, and the results are as follows: Figure 8 (Scale bar 500 nm) and Figure 9 As shown in the scale bar (100 nm), compared with pure ZnO, the Mg1Zn3O catalyst has smaller particle size, more uniform distribution, more rounded particle edges, and exhibits varying degrees of mutual adhesion.

[0041] The Mg1Zn5O catalyst prepared in Example 3 was analyzed by SEM, and the results are as follows: Figure 10 (Scale bar 500 nm) and Figure 11 As shown in the scale bar (100 nm), when the Zn content increases to Mg:Zn=1:5, the catalyst particle size increases, but still maintains the nanoparticle morphology, with rounded particle edges and a dense aggregated state.

[0042] All samples exhibited typical nanoparticle morphology. After the introduction of Mg, Mg1Zn3O and Mg1Zn5O retained their nanoparticle morphology, but the edges of the particles became more rounded and showed varying degrees of mutual adhesion. These nanoscale particles with a certain degree of roughness can provide a large specific surface area and abundant surface active sites, which has significant advantages in the application of reverse water-gas shift reaction.

[0043] 3. X-ray photoelectron spectroscopy (XPS) analysis XPS analysis was performed on the catalysts of Example 2 (Mg1Zn3O), Example 3 (Mg1Zn5O), and Comparative Example 2 (pure ZnO). The results are as follows: Figure 12 As shown.

[0044] Figure 12 A comparison of XPS O1s spectra of the Mg-Zn-O system is presented. Analysis of the three spectra reveals that in the O1s spectra of pure ZnO, Mg1Zn3O, and Mg1Zn5O, the lattice oxygen peak (O1) near approximately 530.0 eV accounts for about 80%–81%, while the surface adsorbed oxygen peak (O2) near approximately 531.5 eV accounts for about 9.2%–9.8%, with remarkably similar proportions. This indicates that changing the Mg doping ratio did not lead to severe collapse of the original lattice structure or the generation of a large number of additional oxygen defect sites, and the chemical state of the bulk material remains very stable.

[0045] 4. Energy-dispersive X-ray spectroscopy (EDS) elemental distribution analysis EDS elemental distribution analysis was performed on the Mg1Zn3O catalyst prepared in Example 2, and the results are as follows: Figures 13 to 17 As shown.

[0046] Figure 13 This is a micro-region morphology diagram of the analyzed sample. Figure 14 The magnesium element (Mg Kα1,2 signal) is shown to be uniformly distributed in the catalyst particles; Figure 15 This shows that oxygen (O Kα1,2 signal) is uniformly distributed in the catalyst particles; Figure 16 The zinc element (Zn Kα1,2 signal) is shown to be uniformly distributed in the catalyst particles; Figure 17 This is a superimposed distribution diagram of the three elements Mg, O, and Zn.

[0047] observe Figures 14 to 17 As can be seen, the bright spots representing Mg (cyan) and Zn (purplish-red) are distributed very densely and uniformly, with a high degree of spatial overlap. No phase separation phenomenon, such as "one area entirely composed of magnesium and another entirely of zinc," is observed within the field of view. This further confirms the success of Mg and Zn co-doping at the micrometer scale, demonstrating excellent compositional uniformity in the material.

[0048] The catalyst performance test results are as follows: The activity test of the catalyst for the reverse water-gas shift reaction was carried out in a fixed-bed reactor. The specific process included: Weigh 50 mg of 40-60 mesh catalyst and 1 g of quartz sand, mix thoroughly, and then pack the mixture into a quartz tube reactor with an inner diameter of 8 mm, an outer diameter of 10 mm, and a length of 45 cm. Both ends of the catalyst bed are filled with quartz sand. Before the experiment, the catalyst was subjected to hydrogen reduction treatment: the temperature was raised to 400℃ and purged for 2 hours under N2 atmosphere (50 mL / min). After the purging, the temperature was lowered to 100℃ under N2 atmosphere, and then raised to three target reaction temperatures of 500℃, 550℃, and 600℃ under N2 atmosphere. The reaction gases were switched (H2 20 mL / min, CO2 20 mL / min, N2 50 mL / min) to carry out the reaction. The reaction outlet gas was detected and analyzed by online gas chromatography.

[0049] The catalytic activity test results of the catalyst prepared by this method are as follows:

[0050] The catalyst prepared in this scheme exhibits the following catalytic activity in the reverse water-gas shift reaction: Figure 1 As shown in the XRD patterns, the MgO-ZnO composite oxide catalysts prepared by the urea homogeneous precipitation method in this scheme all exhibit good crystallinity. At a reaction temperature of 600°C, the single-component oxide catalysts, namely Comparative Example 1 (pure MgO) and Comparative Example 2 (pure ZnO), showed extremely low catalytic activity, with CO2 conversion rates of only 4.4% and 5.2%, respectively. In contrast, the Mg-ZnO composite oxide catalysts prepared by the urea co-precipitation method showed significantly increased activity. It is worth mentioning that the Mg1Zn3O catalyst (Example 2) had the highest CO2 conversion rate, reaching 31.5%, significantly higher than other catalyst ratios, such as Mg1Zn1O (Example 1, 30.4%) and Mg1Zn... 10 O (Example 4, 18.4%). Furthermore, all experimental catalysts exhibited 100% CO selectivity, ensuring efficient hydrogen consumption and high-purity CO production.

[0051] In summary, the catalysts prepared by different methods all exhibited lower activities than the catalysts prepared by the urea precipitation method in the examples, as shown in Table 1 and... Figure 2 As shown. Among them, Mg1Zn1O prepared by the physical mixing method... （物混） The catalyst (Comparative Example 4) exhibited the lowest activity, at only 12.5%, significantly lower than the catalytic activity (31.5%) of the catalyst prepared by the urea homogeneous precipitation method in Example 2. Furthermore, the catalytic stability of the optimal catalyst, Mg1Zn3O, was also tested. Figure 3Experimental results show that during a continuous reaction lasting up to 500 hours, its catalytic activity did not show significant attenuation, the CO2 conversion rate remained at around 31%, and 100% CO selectivity was maintained, demonstrating excellent catalytic stability.

[0052] This pattern indicates that the preparation method of the catalyst has a significant impact on the catalyst structure, which in turn affects the interfacial density between the MgO and ZnO phases.

[0053] Table 1: Comparison of CO2 conversion and CO selectivity results under different catalysts at 600℃

[0054] Table 2: Comparison of Catalytic Stability Test Results for Countercurrent Gas

[0055]

[0056] Finally, it should be noted that, by comparing the catalytic activity and stability of the catalysts, the synergistic effect between MgO and ZnO plays a decisive role in improving the performance of the reverse water-gas shift reaction, mainly due to the following reasons: First, the strong basic sites provided by MgO effectively adsorb and activate CO2 molecules; second, the redox sites provided by ZnO efficiently dissociate H2; and finally, the heterogeneous contact between the two generates stronger catalytically active sites, which can improve the catalytic reaction efficiency. This synergistic effect not only greatly enhances the catalytic activity, but its unique composite oxide structure also effectively prevents the sintering and deactivation of the active components, thereby achieving the efficient and stable operation of this catalyst in the high-temperature reverse water-gas shift reaction.

[0057] Compared to existing catalysts that require the introduction of trivalent metals (such as Al, In, and Ga), this invention uses only three elements: Mg, Zn, and O. It eliminates the need for complex ternary component control, resulting in a simpler, lower-cost, and more environmentally friendly preparation process. The catalyst of this invention contains no precious metals or Cu, avoiding the inherent high-temperature sintering defects of Cu-based catalysts, and exhibits superior stability under the same high-temperature reaction conditions.

[0058] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0059] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a catalyst for reverse water gas shift reaction, characterized by, Includes the following steps: Weigh out magnesium nitrate and zinc acetate to make the molar ratio of Mg atoms to Zn atoms 1:1 to 1:10 or 3:1 to 10:1; Magnesium nitrate and zinc acetate were weighed and dissolved in water. Urea was added, and the mixture was stirred at room temperature. Then, the temperature was raised and stirred to promote the co-precipitation of metal ions. The precipitate was centrifuged, washed, dried, and calcined to obtain the MgO-ZnO composite oxide catalyst.

2. The production method according to claim 1, characterized by, The conditions for heating and stirring are: heating to 90°C and stirring at a constant temperature for 6 hours.

3. The preparation method according to claim 1, characterized in that, The molar ratio of Mg atoms to Zn atoms is 1:

3.

4. The preparation method according to claim 1, characterized in that, The molar ratio of urea to the total amount of Mg and Zn is 4:

1.

5. The preparation method according to claim 1, characterized in that, The washing process includes washing with deionized water and anhydrous ethanol.

6. The preparation method according to claim 1, characterized in that, The drying conditions are: temperature 60℃, time 12 hours.

7. The preparation method according to claim 1, characterized in that, The calcination conditions are as follows: calcination at 600℃ for 2 hours with a temperature increase of 5℃ / min.

8. A catalyst for a reverse water-gas shift reaction, characterized in that, Prepared by the method according to any one of claims 1-7; The catalyst is a composite oxide formed by MgO and ZnO, wherein the molar ratio of Mg atoms to Zn atoms is 1:1 to 1:10 or 3:1 to 10:

1.

9. The catalyst according to claim 8, characterized in that, The molar ratio of Mg atoms to Zn atoms is 1:

3.

10. The catalyst according to claim 9, characterized in that, In the lattice structure of the catalyst, the same nanoparticle simultaneously contains lattice stripes corresponding to the (101) crystal plane of ZnO and lattice stripes corresponding to the (111) crystal plane of MgO.

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