A metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation and its preparation method and application

Abstract

The present invention discloses a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation, as well as its preparation method and application, and belongs to the technical field of low-temperature CO2 methanation catalyst preparation. The catalyst comprises a metal nickel salt and a metal oxide nano-island, wherein the particle size of the metal nickel salt is 5-20 nm, and the particle size of the metal oxide nano-island is 2-10 nm. The present invention also discloses the preparation method and application of the metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation. The novel catalyst of the present invention can convert CO2 into CH4 under mild conditions of 160°C and 0.1 MPa. At 220°C, the CO2 conversion rate is close to 90%, the CH4 selectivity is 100%, and the reaction temperature is 100°C lower than that of traditional nickel-based catalysts.

Description

Technical Field

[0001] The present invention belongs to the technical field of CO2 methanation catalyst preparation, and specifically relates to a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation, and a preparation method and application thereof. Background Art

[0002] As an important primary energy source and raw material, the huge global demand and uneven distribution of CH4 make the development of new CH4 production processes essential. The CO2 methanation reaction, also known as the Sabatier reaction, provides an effective route for large-scale CH4 synthesis and CO2 recycling. Compared with H2, CH4 has significant advantages in storage and transportation, making it an important energy storage carrier in the concept of power-to-gas. Moreover, the CO2 methanation reaction can provide the necessary guarantee for daily water and fuel needs in human exploration of the universe. The CO2 methanation reaction has high conversion rate, high selectivity, and a wide operating range. As energy and environmental issues on Earth become increasingly prominent, the demand for this process will increase significantly. Therefore, there is an urgent need to develop highly active and highly selective CO2 methanation catalysts.

[0003] Currently, metal catalysts (Ru, Rh, Pd, Fe, Co, Ni, etc.) have been used for CO2 methanation. Among them, nickel-based catalysts show great potential due to their low cost and high activity. However, conventional nickel-based catalysts have high reaction temperatures (300-400°C), resulting in high energy consumption and poor catalyst stability. Improving the low-temperature activity and operational stability of nickel-based catalysts is crucial for practical applications. Coal-fired power plant and steel mill tail gas is a significant source of CO2, with tail gas temperatures typically ranging from 150-300°C. Harnessing the waste heat of this tail gas for CO2 methanation would further improve the economics of CO2 methanation. Therefore, the development of nickel-based methanation catalysts suitable for use under mild conditions is highly desirable. Although the size effects, structural sensitivity, and strong metal-support interactions common to nickel-based CO2 methanation catalysts are well understood, the development of highly active nickel-based catalysts capable of CO2 methanation under mild conditions, particularly at temperatures around 200°C and 0.1 MPa, has been slow. Traditional metal oxide-supported nickel-based catalysts emphasize the role of CO bond activation in the CO2 methanation reaction, but ignore the influence of hydrogenation capacity on the reaction rate. Therefore, CO bond activation and H2 activation fail to achieve a good match in kinetics, which may be the key reason why it is difficult to achieve a major breakthrough in catalytic performance.

[0004] In view of this, in order to overcome the shortcomings of the existing technology, it is necessary to provide a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation, so as to achieve a CO2 methanation process with high conversion rate, high selectivity and high stability under mild conditions. Summary of the Invention

[0005] The purpose of the present invention is to provide a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation. The preparation process of the catalyst of the present invention is simple and low-cost, and it can achieve a CO2 methanation process with high conversion rate, high selectivity and high stability under mild conditions.

[0006] One of the objectives of the present invention is to provide a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation.

[0007] The technical solution of the present invention to solve the above technical problems is: a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation, comprising a metal nickel salt and a metal oxide nano-island, wherein the particle size of the metal nickel salt is 5-20nm, the particle size of the metal oxide nano-island is 2-10nm, and the metal oxide in the metal oxide nano-island is selected from one of aluminum oxide, cerium oxide, zirconium oxide, yttrium oxide, scandium oxide, zinc oxide, gallium oxide or cadmium oxide.

[0008] The principle of the metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation of the present invention is:

[0009] The surface of the metal oxide nanoislands serves as a CO bond activation site. The smaller the metal oxide nanoislands, the more active the surface oxygen species, making it easier for oxygen vacancies to participate in CO bond dissociation. Metal nickel salts provide abundant H2 activation sites. CO2 is easily activated on the metal oxide nanoislands and combines with active hydrogen species on the surrounding metal nickel salt surfaces, leading to subsequent hydrogenation reactions to produce CH4. Highly dispersed nickel species can provide a hydrogen-rich atmosphere, facilitating deep hydrogenation reactions. The oxide nanoisland-metal nickel interface, serving as a reaction site for low-temperature CO2 methanation, can promote CO bond dissociation while providing a hydrogen-rich atmosphere, achieving rate matching between CO bond dissociation and hydrogenation reactions.

[0010] Catalytic performance results demonstrate that the catalyst provided by the present invention can convert CO2 to CH4 under mild conditions of 160°C and 0.1 MPa. At 220°C, the CO2 conversion rate approaches 90%, with a CH4 selectivity of 100%. This reaction temperature is 100°C lower than that of traditional nickel-based catalysts. Furthermore, the catalyst provided by the present invention maintains excellent stability over a long-term operation period of 125 hours, demonstrating its significant potential for application.

[0011] The beneficial effects of the metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation of the present invention are:

[0012] 1. This invention achieves efficient and coordinated CO bond dissociation and hydrogenation reactions by constructing a metal oxide nanoisland-nickel active interface. The metal oxide nanoisland-modified nickel-based catalyst can achieve high CO conversion, high CH selectivity, and high stability in the CO methanation reaction at mild conditions of 220°C and 0.1 MPa. At high space velocities, the CO conversion is greater than 80%, and the methane selectivity is greater than 99%. Most current catalysts require temperatures above 300°C to achieve high methanation activity.

[0013] 2. The nickel-based catalyst modified with metal oxide nano-islands provided by the present invention further improves its catalytic activity by adjusting the content of metal oxide and metallic nickel, precisely controlling the microstructure and reaction interface of metal oxide nano-islands and metallic nickel.

[0014] On the basis of the above technical solution, the present invention can also be improved as follows.

[0015] Furthermore, the mass content of the metal nickel salt is 50-95 wt%, and the mass content of the metal oxide nano-islands is 5-50 wt%.

[0016] Furthermore, the particle size of the metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation is 10-200 mesh.

[0017] A second object of the present invention is to provide a method for preparing a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation.

[0018] The technical solution of the present invention to solve the above technical problems is: a method for preparing a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation, comprising the following steps:

[0019] S1: dissolving a metal nickel salt and a metal oxide precursor salt in a solvent to obtain a solution A;

[0020] S2: dissolving oxalic acid dihydrate in a solvent to obtain solution B;

[0021] S3: adding solution B to solution A and stirring at room temperature, then collecting the solid product, washing it with ethanol 2-4 times, drying it, and finally calcining it in a muffle furnace at 300-600°C for 1-10 hours to obtain a catalyst precursor;

[0022] S4: reducing the catalyst precursor obtained in S3 under a hydrogen atmosphere at normal pressure to obtain a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation.

[0023] The beneficial effects of the preparation method of the metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation of the present invention are:

[0024] The present invention adopts a one-step co-precipitation combined with hydrogen reduction method for preparation, which has the advantages of simple preparation process and easy scale-up; wherein dihydrated oxalic acid is selected as a precipitant in the co-precipitation method, and dihydrated oxalic acid can efficiently complex metal cations, which is conducive to the dispersion of various components in the catalyst.

[0025] On the basis of the above technical solution, the present invention can also be improved as follows.

[0026] Furthermore, the metal nickel salt in step S1 is selected from one of nickel nitrate hexahydrate, nickel chloride hexahydrate or nickel sulfate hexahydrate; the precursor salt of the metal oxide is selected from one of aluminum nitrate nonahydrate, cerium nitrate hexahydrate, zirconium nitrate pentahydrate, yttrium nitrate hexahydrate, hydrated scandium nitrate, zinc nitrate hexahydrate, gallium nitrate hydrate, samarium nitrate hexahydrate, cadmium nitrate tetrahydrate, aluminum chloride, cerium chloride, zirconium chloride, zirconium oxychloride, yttrium chloride, scandium chloride, zinc chloride, gallium chloride, samarium chloride, cadmium chloride, aluminum sulfate 18hydrate, cerium ammonium sulfate hydrate, zirconium sulfate tetrahydrate, yttrium sulfate octahydrate or zinc sulfate heptahydrate.

[0027] Furthermore, the amount of the metal nickel salt is 0.01-0.02 mol, the amount of the metal oxide precursor salt is 0.01-0.02 mol; and the amount of the oxalic acid dihydrate in step S2 is 0.04-0.06 mol.

[0028] The above method has the further beneficial effect that oxalic acid dihydrate can efficiently complex metal cations, which is beneficial to the dispersion of various components in the catalyst, and the obtained catalyst has a large specific surface area and good dispersibility.

[0029] Furthermore, in step S1 and step S2, the solvent is deionized water or ethanol; the amount used is 80-120 mL.

[0030] Furthermore, in step S4, the concentration of hydrogen in the reduction pretreatment is 5-100%, and the total flow rate is 5-50 mL / min; the reduction heat treatment temperature is 350-600° C., and the heat treatment time is 4-10 h.

[0031] The third object of the present invention is to provide an application of a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation.

[0032] The technical solution of the present invention to solve the above technical problems is: application of the above metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation in low-temperature CO2 methanation reaction.

[0033] The beneficial effects of the application of the present invention are:

[0034] The metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation of the present invention maintains excellent stability during a long-term operation of 125 hours and has great application potential.

[0035] On the basis of the above technical solution, the present invention can also be improved as follows.

[0036] Furthermore, the specific method of the application is: placing the metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation in a fixed bed reactor, introducing a mixed reaction gas with a molar ratio of carbon dioxide to hydrogen of 1:4, and a mass space velocity of 6000-27000 mL g -1 h -1 , reaction pressure 0.1-1.0MPa, reaction temperature 160-340℃. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 TEM structure diagram of nickel-based catalyst modified with metal oxide nanoislands.

[0038] Figure 2 Effect of metal loading on catalytic performance of nickel-based catalysts modified with metal oxide nanoislands.

[0039] Figure 3 Comparison of the performance of metal oxide nanoislands modified nickel-based catalysts and reported catalysts.

[0040] Figure 4 The effect of preparation method on catalytic performance of nickel-based catalysts modified with metal oxide nano-islands.

[0041] Figure 5 XRD spectra of metal oxide nano-islands modified nickel-based catalysts obtained by different preparation methods.

[0042] Figure 6 The catalytic performance of nickel-based catalysts modified with metal oxide nanoislands at different mass space velocities.

[0043] Figure 7 Catalytic performance of nickel-based catalyst modified with metal oxide nanoislands for CO2 methanation reaction for 125 h.

[0044] Figure 8 The influence of the type of metal oxide nanoisland precursor on the catalytic performance.

[0045] Figure 9 Comparison of the apparent activation energy of CO2 methanation reaction between Example 1 and Comparative Example 1.

[0046] Figure 10 Comparison of the reaction orders of CO2 methanation to CO2 and H2 between Example 1 and Comparative Example 1.

[0047] Figure 11 Comparison of CO2 and H2 adsorption performance between Example 1 and Comparative Example 1.

[0048] Figure 12 XPS results of Example 1 and Comparative Example 1 after different treatments. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following Figure 1-9 The present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0050] Additional aspects and advantages of the present invention will be described in part in the following description, and in part will become apparent from the following description or learned through practice of the present invention. It should be understood that the following description is only used to explain the present invention and is not intended to limit the present invention.

[0051] As used herein, the terms "comprises," "including," "having," "containing" or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0052] The phrase "consisting of" excludes any unrecited element, step, or component. If used in a claim, this phrase renders the claim closed, excluding materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim, rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0053] When dosage, concentration, or other value or parameter is expressed as a range, preferred range, or a range limited by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when disclosing a range of "1 to 5", the described range should be interpreted as including the range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0054] In some instances, approximating terms may correspond to the instrumental precision of the measured value. In this specification and claims, range limits may be combined and / or interchanged. Unless otherwise indicated, these ranges include all subranges contained therein.

[0055] The indefinite articles "a" and "an" before the elements or components of the present invention do not limit the quantity requirement (i.e. the number of times they appear). Therefore, "a" or "an" should be interpreted as including one or at least one, and elements or components in the singular also include plural forms, unless the quantity clearly refers to only the singular form.

[0056] When used in conjunction with the present invention, terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the technical features of various embodiments of the present invention may be combined as long as they do not conflict with each other.

[0057] Unless otherwise specified, the raw materials and equipment used in the present invention can be purchased from the market or are commonly used in the art. The methods in the embodiments, unless otherwise specified, are all conventional methods in the art.

[0058] In some embodiments, the present invention provides a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation, characterized in that it includes a metal nickel salt and a metal oxide nano-island, the particle size of the metal nickel salt is 5-20nm, the particle size of the metal oxide nano-island is 2-10nm, and the metal oxide in the metal oxide nano-island is selected from one of aluminum oxide, cerium oxide, zirconium oxide, yttrium oxide, scandium oxide, zinc oxide, gallium oxide or cadmium oxide. Further, the particle size of the metal nickel salt can be 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm or 20nm, and the particle size of the metal oxide nano-island can be 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm or 10nm.

[0059] In some embodiments, the weight content of the metal nickel salt is 50-95 wt %, and the weight content of the metal oxide nano-islands is 5-50 wt %. Furthermore, the weight content of the metal nickel salt can be one of 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and 95%; and the weight content of the metal oxide can be one of 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%.

[0060] In some embodiments, the metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation has a particle size of 10-200 mesh. Further, the particle size of the catalyst can be 10 mesh, 20 mesh, 30 mesh, 40 mesh, 50 mesh, 60 mesh, 70 mesh, 80 mesh, 90 mesh, 100 mesh, 110 mesh, 120 mesh, 130 mesh, 140 mesh, 150 mesh, 160 mesh, 170 mesh, 180 mesh, 190 mesh, or 200 mesh.

[0061] In some embodiments, the present invention provides a method for preparing a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation, comprising the following steps:

[0062] S1: dissolving a metal nickel salt and a metal oxide precursor salt in a solvent to obtain a solution A;

[0063] S2: dissolving oxalic acid dihydrate in a solvent to obtain solution B;

[0064] S3: adding solution B to solution A and stirring at room temperature, then collecting the solid product, washing it with ethanol 2-4 times, drying it, and finally calcining it in a muffle furnace at 300-600°C for 1-10 hours to obtain a catalyst precursor;

[0065] S4: reducing the catalyst precursor obtained in S3 under a hydrogen atmosphere at normal pressure to obtain a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation.

[0066] Furthermore, in some embodiments, the metal nickel salt in step S1 is selected from one of nickel nitrate hexahydrate, nickel chloride hexahydrate or nickel sulfate hexahydrate; the precursor salt of the metal oxide is selected from one of aluminum nitrate nonahydrate, cerium nitrate hexahydrate, zirconium nitrate pentahydrate, yttrium nitrate hexahydrate, scandium nitrate hydrate, zinc nitrate hexahydrate, gallium nitrate hydrate, samarium nitrate hexahydrate, cadmium nitrate tetrahydrate, aluminum chloride, cerium chloride, zirconium chloride, zirconium oxychloride, yttrium chloride, scandium chloride, zinc chloride, gallium chloride, samarium chloride, cadmium chloride, aluminum sulfate 18hydrate, cerium ammonium sulfate hydrate, zirconium sulfate tetrahydrate, yttrium sulfate octahydrate or zinc sulfate heptahydrate.

[0067] Furthermore, in step S1, the amount of the metal nickel salt is 0.01-0.02 mol, and the amount of the metal oxide precursor salt is 0.01-0.02 mol; and in step S2, the amount of the oxalic acid dihydrate is 0.04-0.06 mol.

[0068] Furthermore, the molar ratio of the metal nickel salt to the metal oxide is 4-9:1.

[0069] Furthermore, in step S1 and step S2, the solvent is deionized water or ethanol; the amount used is 80-120 mL.

[0070] Furthermore, in step S4, the concentration of hydrogen in the reduction pretreatment is 5-100%, and the total flow rate is 5-50 mL / min; the reduction heat treatment temperature is 350-600° C., and the heat treatment time is 4-10 h.

[0071] In some embodiments, the present invention provides the use of the above-mentioned metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation in a low-temperature CO2 methanation reaction.

[0072] Furthermore, the application method is as follows: placing the metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation in a fixed bed reactor, introducing a mixed reaction gas with a molar ratio of carbon dioxide to hydrogen of 1:4, and a mass space velocity of 6000-27000 mL g -1 h -1 , reaction pressure 0.1-1.0MPa, reaction temperature 160-340℃.

[0073] The following is further described with reference to specific embodiments.

[0074] Example 1

[0075] 1. Dissolve 5.23 g of nickel nitrate hexahydrate and 0.77 g of yttrium nitrate hexahydrate in 100 mL of ethanol to obtain solution A;

[0076] 2. Dissolve 6.31 g of oxalic acid dihydrate in 100 mL of ethanol to obtain solution B;

[0077] 3. Solution B was added to solution A and stirred at room temperature for 4 h. The solid product was then collected, washed with ethanol three times, dried at 80 ° C for 12 h, and then calcined in a muffle furnace at 400 ° C for 2 h to obtain a catalyst precursor;

[0078] 4. The catalyst precursor obtained in step 3 was pretreated by reduction at 500°C in a hydrogen atmosphere at normal pressure for 5 hours to obtain a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation, named Y2O3 / Ni catalyst.

[0079] The catalyst was granulated into 40-80 mesh and placed in a fixed bed for CO2 methanation reaction. A mixed reaction gas with a molar ratio of CO2 and H2 of 1:4 was introduced at a space velocity of 15000-27000 mL g -1 h -1 , the reaction pressure is 0.1MPa, and the reaction temperature is 160-280℃.

[0080] Example 2

[0081] The difference from Example 1 is that in step 1, 4.65 g of nickel nitrate hexahydrate and 1.53 g of yttrium nitrate hexahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0082] The catalyst obtained in this example is named Y2O3 / Ni-2 catalyst.

[0083] Example 3

[0084] The difference from Example 1 is that in step 1, 5.52 g of nickel nitrate hexahydrate and 0.38 g of yttrium nitrate hexahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0085] The catalyst obtained in this example is named Y2O3 / Ni-3 catalyst.

[0086] Example 4

[0087] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.86 g of zirconium nitrate pentahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0088] The catalyst obtained in this example is named ZrO2 / Ni catalyst.

[0089] Example 5

[0090] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.87 g of cerium nitrate hexahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0091] The catalyst obtained in this example is named CeO2 / Ni catalyst.

[0092] Example 6

[0093] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.75 g of aluminum nitrate nonahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0094] The catalyst obtained in this example is named Al2O3 / Ni catalyst.

[0095] Example 6

[0096] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.75 g of aluminum nitrate nonahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0097] The catalyst obtained in this example is named Al2O3 / Ni catalyst.

[0098] Example 7

[0099] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.80 g of chromium nitrate nonahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0100] The catalyst obtained in this example is named Cr2O3 / Ni catalyst.

[0101] Example 8

[0102] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.87 g of lanthanum nitrate hexahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0103] The catalyst obtained in this example is named La2O3 / Ni catalyst.

[0104] Example 9

[0105] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.50 g of manganese nitrate tetrahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0106] The catalyst obtained in this example is named MnO / Ni catalyst.

[0107] Example 10

[0108] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.51 g of magnesium nitrate hexahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0109] The catalyst obtained in this example is named MgO / Ni catalyst.

[0110] Example 11

[0111] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.47 g of calcium nitrate tetrahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0112] The catalyst obtained in this example is named CaO / Ni catalyst.

[0113] Example 12

[0114] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.52 g of scandium nitrate hydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0115] The catalyst obtained in this example is named Sc2O3 / Ni catalyst.

[0116] Example 13

[0117] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.89 g of samarium nitrate hexahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0118] The catalyst obtained in this example is named Sm2O3 / Ni catalyst.

[0119] Example 14

[0120] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.87 g of praseodymium nitrate hexahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0121] The catalyst obtained in this example is named Pr6O 11 / Ni catalyst.

[0122] Example 15

[0123] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.88 g of neodymium nitrate hydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0124] The catalyst obtained in this example is named Nd2O3 / Ni catalyst.

[0125] Example 16

[0126] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.23 g of ammonium metavanadate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0127] The catalyst obtained in this example is named V3O5 / Ni catalyst.

[0128] Example 17

[0129] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.88 g of ammonium metavanadate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0130] The catalyst obtained in this example is named WO3 / Ni catalyst.

[0131] Example 18

[0132] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.40 g of manganese chloride tetrahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0133] The catalyst obtained in this example is named MnO-Cl / Ni catalyst.

[0134] Example 19

[0135] The difference from Example 1 is that in step 1, 5.23 g of nickel nitrate hexahydrate and 0.22 g of anhydrous calcium chloride are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0136] The catalyst obtained in this example is named CaO-Cl / Ni catalyst.

[0137] Comparative Example 1

[0138] The difference from Example 1 is that in step 1, 0.58 g of nickel nitrate hexahydrate and 6.13 g of yttrium nitrate hexahydrate are dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0139] The catalyst obtained in this comparative example is named Ni / Y2O3 catalyst.

[0140] Comparative Example 2

[0141] The difference from Example 1 is that in step 1, 5.82 g of nickel nitrate hexahydrate is dissolved in 100 mL of ethanol to obtain solution A. The rest are the same.

[0142] The catalyst obtained in this comparative example is named NiO catalyst.

[0143] Comparative Example 3

[0144] The difference from Example 1 is that in step 1, 5.82 g of nickel nitrate hexahydrate was dissolved in 100 mL of ethanol to obtain solution A; in step 3, solution B was added to solution A and stirred at room temperature for 4 hours. The solid product was then collected, washed three times with ethanol, dried at 80°C for 12 hours, and then calcined in a muffle furnace at 400°C for 2 hours to obtain nickel oxide; in step 4, 0.5696 g of yttrium nitrate nonahydrate was dissolved in 5 mL of deionized water and gradually added dropwise to 1 g of the nickel oxide obtained in step 3. The mixture was stirred at room temperature for 24 hours, dried at 110°C for 12 hours, and calcined at 400°C for 2 hours. The rest of the process was the same.

[0145] The catalyst obtained in this comparative example is named Y2O3 / Ni-IM catalyst.

[0146] Table 1 CO2 conversion and CH4 selectivity of each catalyst for low-temperature CO2 methanation reaction

[0147]

[0148] Table 1 shows the CO2 conversion rate and CH4 selectivity of each catalyst for CO2 methanation reaction at 220℃. Comparing Examples 1-3 with Comparative Examples 1-3, it is found that the Y2O3 nano-island modified nickel catalyst (Y2O3 / Ni) in Example 1 has the best low-temperature CO2 methanation activity, showing a CO2 conversion rate of up to 80% and a methane selectivity of 100% at 220℃. Figure 1 Transmission electron microscopy images reveal that Y2O3 / Ni possesses a unique structure compared to traditional supported catalysts. Small Y2O3 nano-islands are evenly distributed on the surface of the active nickel metal. These metal oxide nano-islands not only stabilize and disperse the nickel metal—in the case of Y2O3 / Ni, the nickel metal size remains at 15nm—but also effectively activate the CO bond, accelerating the dissociation of the CO bond between CO2 and key intermediates. This novel structure creates abundant CO bond activation and H2 activation sites on the catalyst surface, enabling kinetic matching between CO dissociation and hydrogenation reactions, thus enabling low-temperature CO2 methanation.

[0149] By comparing Example 1 with Examples 4-17, it was found that the five catalysts Y2O3 / Ni, ZrO2 / Ni, CeO2 / Ni, Al2O3 / Ni and Sc2O3 / Ni all exhibited excellent low-temperature CO2 methanation activity, with CO2 conversion rates of 80.1%, 85.8%, 84.7%, 88.7% and 86.9%, respectively, and methane selectivity of 100%. The above results reflect the unique superiority of the metal oxide nano-island modified nickel-based catalyst in the present invention and the universality of this structure in low-temperature CO2 methanation.

[0150] Figure 2The results of the reaction between 160-280℃ for the Y2O3 nano-island modified nickel catalysts with different metal loadings in Examples 1-3 are compared. It can be seen that with the increase of metal loading, the CO2 conversion rate-methane selectivity curve of the catalyst gradually shifts to the low temperature region, indicating that increasing the metal loading is beneficial to the low-temperature CO2 methanation reaction. In addition, the optimal Y2O3 / Ni catalyst can catalyze the CO2 methanation reaction at 160℃ and shows excellent performance at 220℃. -1 h -1 The CO2 conversion rate reaches 80% and the methane selectivity is 100% at the air velocity

[0151] Figure 3 A comparison of the CO2 methanation reaction performance of the Y2O3 nano-island modified nickel catalyst in Example 1 and the reported catalyst is given. It can be seen that the Y2O3 nano-island modified nickel catalyst shows excellent performance at 220°C, which is 100°C lower than the reaction temperature of the reported nickel-based catalyst. The performance is also better than that of the precious metal ruthenium-based catalyst, reflecting the superior performance of the Y2O3 nano-island modified nickel catalyst.

[0152] Figure 4 The effects of the catalyst preparation methods of Example 1 and Comparative Example 3 on catalytic performance are shown. Both the one-step coprecipitation method and the step-by-step impregnation method can produce metal oxide nano-island modified nickel catalysts. Therefore, Comparative Example 3 can also show a CO2 conversion rate of nearly 70% at 220°C, which is much better than the traditional supported catalyst. The main difference between the two preparation methods is that the catalyst active metal nickel prepared by the one-step coprecipitation method is smaller in size and better in dispersion (see Figure 5 ), so the catalyst prepared by the one-step co-precipitation method has better performance in low-temperature CO2 methanation than the step-by-step impregnation method.

[0153] Figure 6 Example 1 is given at 220 ° C, 0.1 MPa, 15000-27000 mL g -1 h -1 The low-temperature CO2 methanation performance within the space velocity range shows that the Y2O3 / Ni catalyst can still maintain a CO2 conversion rate of more than 80% and a CH4 selectivity of 100% at high space velocity.

[0154] Figure 7 The results of Example 1 were given at 220°C, 0.1 MPa, 15000 mL g -1 h -1 From the long-term operation stability under the conditions of 125h reaction, it can be seen that the CO2 conversion rate of the catalyst remains above 80% and the CH4 selectivity is always 100%, indicating that the catalyst has good stability.

[0155] Figure 8The effects of the types of metal oxide nano-island precursors on the catalytic performance of Examples 9 and 18 as well as Examples 11 and 19 are given. It can be seen that both nitrate precursors and chloride precursors can be used to prepare this type of catalyst, among which the catalyst synthesized by the nitrate precursor has better performance.

[0156] Figure 9 The comparison of the apparent activation energy of CO2 methanation between Example 1 and Comparative Example 1 shows that the apparent activation energy of the catalyst in Example 1 is as low as 44.3 kJ mol -1 In contrast, the apparent activation energy of the conventional nickel catalyst in Comparative Example 1 is as high as 93.0 kJ mol -1 , indicating that the new metal oxide nano-island modified nickel catalyst is conducive to low-temperature methanation reaction.

[0157] Figure 10 A comparison of the reaction orders of CO2 and H2 in the methanation of CO2 in Example 1 and Comparative Example 1 is given, wherein the CO2 reaction order is smaller than the H2 reaction order, indicating that the reactant CO2 or the intermediate CO is too strongly adsorbed on the catalyst surface and the surface H2 adsorption is too weak, which is not conducive to the reaction; compared with Comparative Example 1, the CO2 reaction order of the catalyst in Example 1 is increased and the H2 reaction order is decreased, indicating that the H2 adsorption on the catalyst surface is enhanced and the CO2 / CO adsorption is weakened, thereby promoting the CO2 methanation.

[0158] Figure 11 A comparison of the CO2 and H2 adsorption performance of Example 1 and Comparative Example 1 shows that the Example 1 catalyst weakly and moderately adsorbs 83% of CO2, while the Comparative Example 1 catalyst primarily adsorbs 52% of CO2. Furthermore, the Example 1 catalyst adsorbs twice as much H2 as the Comparative Example 1 catalyst. Furthermore, the H2 desorption temperature spans the CO2 methanation reaction temperature range, while the Comparative Example 1 catalyst desorbs H2 only above 450°C. These results demonstrate that the Example 1 catalyst exhibits enhanced H2 adsorption and weakened CO2 adsorption, thus facilitating low-temperature methanation reactions.

[0159] Figure 12 The XPS results of Example 1 and Comparative Example 1 after different treatments are given. After the reduction treatment, the catalyst of Example 1 shows partially reduced Y2O 3-x Species, Y2O after CO2 methanation reaction 3-x The species has been oxidized, indicating that Y2O 3-x The species can participate in CO2 activation and promote CO bond dissociation, while no Y2O was observed in the catalyst of Comparative Example 1 after reduction treatment. 3-x Species generation indicates that metal oxide nanoislands can form highly active Y2O after reduction treatment 3-x species, which is conducive to CO bond dissociation.

[0160] It is easy for those skilled in the art to understand that 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 and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation, characterized in that: The catalyst comprises active nickel and metal oxide nano-islands, wherein the metal oxide is scandium oxide, wherein the particle size of the metal oxide nano-islands is 2-10 nm, and the particle size of the active nickel is 5-20 nm; the mass content of the active nickel in the catalyst is 50-95%, and the mass content of the metal oxide is 5-50%; and the preparation method of the metal oxide nano-island modified nickel-based catalyst comprises the following steps: S1: dissolving a metal nickel salt and a metal oxide precursor salt in a solvent to obtain a solution A; S2: dissolving oxalic acid dihydrate in a solvent to obtain solution B; S3: Solution B is added to solution A and stirred at room temperature. The solid product is then collected, washed with ethanol 2 to 4 times, dried, and finally calcined in a muffle furnace at 300 to 600 °C for 1 to 10 h to obtain a catalyst precursor. S4: reducing the precursor obtained in S3 under a hydrogen atmosphere at normal pressure to obtain a nickel-based catalyst modified with metal oxide nano-islands.

2. The metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation according to claim 1, characterized in that: The particle size of the nickel-based catalyst is 10 to 200 mesh.

3. A method for preparing a metal oxide nano-island modified nickel-based catalyst for low-temperature CO2 methanation according to any one of claims 1-2, characterized in that: The preparation method comprises the following steps: S1: dissolving a metal nickel salt and a precursor salt of a metal oxide in a solvent to obtain a solution A; S2: dissolving oxalic acid dihydrate in a solvent to obtain solution B; S3: Solution B is added to solution A and stirred at room temperature. The solid product is then collected, washed with ethanol 2 to 4 times, dried, and finally calcined in a muffle furnace at 300 to 600 °C for 1 to 10 h to obtain a catalyst precursor. S4: reducing the precursor obtained in S3 under a hydrogen atmosphere at normal pressure to obtain a nickel-based catalyst modified with metal oxide nano-islands.

4. The preparation method according to claim 3, characterized in that In step S1, the metal nickel salt is selected from one of nickel nitrate hexahydrate, nickel chloride hexahydrate, and nickel sulfate hexahydrate; in step S2, the precursor salt of the metal oxide is selected from one of scandium nitrate hydrate and scandium chloride.

5. The preparation method according to claim 3 or 4, characterized in that In step S1, the amount of the metal nickel salt used is 0.01 to 0.02 mol, and the amount of the metal oxide precursor salt used is 0.01 to 0.02 mol; and / or, the amount of oxalic acid dihydrate used in step S2 is 0.04 to 0.06 mol.

6. The preparation method according to claim 3 or 4, characterized in that The solvent used in steps S1 and S2 is deionized water or ethanol; and / or, the amount of the solvent used is 80 to 120 mL.

7. The preparation method according to claim 3 or 4, characterized in that In step S4, the reduction pretreatment hydrogen concentration range is 5 to 100%, and the total flow rate range is 5 to 50 mL / min; the reduction heat treatment temperature is 350 to 600°C, and the heat treatment time is 4 to 10 h.

8. Use of the metal oxide nano-island modified nickel-based catalyst according to any one of claims 1-2 or the metal oxide nano-island modified nickel-based catalyst prepared by the preparation method according to any one of claims 3-7 in a low-temperature CO2 methanation reaction.

9. The use according to claim 8, characterized in that The method of application is: The nickel-based catalyst was placed in a fixed-bed reactor, and a reaction gas with a molar ratio of carbon dioxide to hydrogen of 1:4 was introduced at a mass space velocity of 6000-27000 mL g -1 h -1 , reaction pressure 0.1 ~ 1.0 MPa, reaction temperature 160 ~ 340 ℃.

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