Spinel-structured copper-rich high-entropy composite oxide catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of air pollution control treatment, and provides a copper-rich high-entropy composite oxide catalyst with a spinel structure and a preparation method and application thereof, the metal elements in the catalyst comprise Cu, Co and three or four of Mg, Mn, Cr, Ni, Fe and Zn, and by matching the oxidation-reduction capacity and oxygen vacancy content of the catalyst, the content of the copper-rich high-entropy composite oxide catalyst with the spinel structure is improved. The high-entropy metal oxide catalyst has the advantages that the bond breaking rate of a C-C bond is matched with the oxygen flow rate, the VOCs deep oxidation and mineralization capacity of the catalyst is improved, the low-temperature activity, deep mineralization and sintering resistance are improved at a time through lattice distortion, oxygen vacancy and oxygen flow, and the problems that an existing high-entropy metal oxide catalyst is poor in low-temperature activity, low in mineralization rate, poor in stability and the like are solved. Cu is locked at a crystal lattice A position by utilizing a'high-entropy spinel 'structure and a hysteresis diffusion effect, migration of Cu is inhibited, high activity of rich copper is reserved, the sintering defect of the rich copper is overcome, and unification of catalytic activity and structural stability is realized.

Description

Technical Field

[0001] This invention relates to the field of air pollution control and treatment technology, specifically to a copper-rich high-entropy composite oxide catalyst with a spinel structure, its preparation method, and its application. Background Technology

[0002] Volatile organic compounds (VOCs) mainly include hydrocarbons, halogenated hydrocarbons, oxygen-containing alcohols, ketones, esters, and some nitrogen- and sulfur-containing organic compounds, and are one of the major sources of air pollution. VOCs participate in the formation of ozone and secondary aerosols in the atmosphere, and their emissions cause serious air pollution and harm to human health. Currently, the main methods for VOCs treatment include physical adsorption, catalytic oxidation, and oxidative absorption. Among them, catalytic oxidation technology can catalytically oxidize organic waste gas into CO2 and H2O under the action of a catalyst. It is widely used due to its high efficiency, low energy consumption, and wide applicability. Its core key is a low-temperature, high-efficiency catalyst.

[0003] Although catalytic oxidation has a low activation temperature, it releases a large amount of heat during the process, posing challenges to the low-temperature activity and long-term stability of the catalyst. Existing technologies often use precious metal catalysts, which have good low-temperature activity and high catalytic oxidation efficiency, but their high price and scarce resources limit their application. They also have drawbacks such as poor resistance to water and sulfur, susceptibility to catalyst poisoning, and easy sintering.

[0004] Non-precious metal oxide catalysts have attracted attention due to their lower cost, but conventional single-component, two-component, and three-component oxide catalysts suffer from limitations in redox performance, oxygen vacancy content control, low mineralization rates, and structural instability. For example, Co3O4 nanorod catalysts have few oxygen vacancies, low mineralization rates, and begin sintering above 450℃; MnO... x -CeO2 composite oxide catalysts are prone to phase separation at high temperatures, and their activity decreases significantly in the presence of water vapor. CuO / CeO2 supported catalysts exhibit strong copper migration capabilities, rapidly growing into CuO particles at 550℃, but exhibit weak interaction with the support, resulting in powder shedding after cycling. It is evident that the aforementioned non-precious metal oxide catalysts all suffer from poor long-term stability, and their activity temperatures are generally 30–70℃ higher than those of precious metal catalysts, with mineralization rates typically below 90%.

[0005] In recent years, high-entropy oxides (HEOs) have exhibited good stability and catalytic performance due to their multi-element synergistic effects, lattice distortion, and high oxygen vacancy concentration. However, most existing HEOs are rock salt, fluorite, or perovskite structures, which have low specific surface areas, require high calcination temperatures for preparation, and consume a lot of energy. Spinel-type HEOs are rarely reported. Furthermore, due to the need for anti-sintering properties, the copper content in HEOs is usually low, resulting in low oxygen vacancy concentrations at low temperatures, which limits their low-temperature activity and applications.

[0006] Therefore, there is currently a lack of systematic research on copper-rich high-entropy composite oxide catalysts suitable for VOCs treatment that exhibit good low-temperature activity, high mineralization rate, and strong stability. Summary of the Invention

[0007] The present invention aims to provide a copper-rich high-entropy composite oxide catalyst with a spinel structure, its preparation method and application, in order to solve the problems of poor low-temperature activity, low mineralization rate and poor stability of existing high-entropy metal oxide catalysts.

[0008] To achieve the above objectives, a first aspect of the present invention provides a copper-rich high-entropy composite oxide catalyst with a spinel structure, wherein the metal elements in the catalyst include Cu, Co, and three or four of Mg, Mn, Cr, Ni, Fe, and Zn.

[0009] By adopting the above technical solution, the catalyst's redox capacity and oxygen vacancy content can be matched, ensuring that the CC bond breaking rate is consistent with the oxygen flow rate. This enhances the catalyst's ability to deeply oxidize and mineralize VOCs. The low-temperature activity, deep mineralization, and anti-sintering performance are improved in one step through "lattice distortion, oxygen vacancies, and oxygen flow," specifically manifested in the following aspects: 1) The 5 to 6 metal ions used in this invention have a radius difference of less than 15%. The entry of multiple elements into the crystal lattice causes lattice distortion, resulting in in-plane compressive / tensile stress, reducing the Co–O bond energy, making it easier to form oxygen vacancies, improving oxygen mobility, and enhancing the deep oxidation ability of the catalyst. 2) Multi-component synergistic system regulates the redox properties of catalysts, Cu 2+ / Cu + With Co 3+ / Co 2+ It forms a double redox pair, with an oxygen vacancy concentration several times higher than that of conventional Co3O4, thereby enhancing the low-temperature activity of catalytic oxidation of VOCs; 3) Utilizing the high-entropy "hysteresis diffusion effect" to suppress Cu 2+ Migration enhances the high-temperature stability of catalysts, solving the industry problem of copper-rich catalysts being prone to sintering.

[0010] In a preferred embodiment, the active component of the catalyst has a pure spinel structure.

[0011] It should be noted that Cu 2+ / Cu +Cu has a moderate redox potential, which can provide a large number of oxygen vacancies to improve low-temperature activity. The Cu-O bond is relatively weak, which is conducive to activating the C-H bond and reducing the adsorption barrier of toluene. At the same time, its price is much lower than that of precious metals, which is conducive to large-scale industrial use. However, Cu ions have a low migration barrier, are easy to aggregate, and are prone to sintering and deactivation. Excessive Cu will squeeze out other active sites, leading to phase separation and a decrease in specific surface area. These defects have led to the problem that the low-temperature activity and anti-sintering properties of copper-based catalysts are difficult to coexist in the existing technology. The copper content in high-entropy oxides is usually also low.

[0012] The spinel-type structure (AB2O4) described in this invention has unique advantages not found in other structures: 1) The tetrahedral A-site / octahedral B-site in the crystal lattice can simultaneously accommodate multiple transition metal ions, naturally suitable for "high entropy" design; 2) Cu at the A-site + / Cu 2+ With B position Co 2+ / Co 3+ The two redox pairs form a continuous electron transport chain, improving the oxygen vacancy regeneration rate; 3) The three-dimensional interconnected [BO6] octahedral network has straight oxygen migration channels, which can provide O 2- It provides a low-barrier diffusion path; 4) It has a small coefficient of thermal expansion and can maintain its framework at 800°C without undergoing a phase transition, resulting in a significantly lower specific surface area reduction rate compared to perovskite structures; 5) It has a wide preparation temperature window and can crystallize at lower temperatures, with energy consumption far lower than that of perovskite / hexaaluminate structures.

[0013] By adopting the above technical solution, this invention increases the Cu content on the basis of Co and introduces 4-5 kinds of transition metals, while still maintaining a single spinel-type solid solution (XRD test shows no second phase). Thus, the Cu can be locked in the A site of the crystal lattice using the "high-entropy spinel" structure, and its migration can be suppressed by hysteresis diffusion. This not only retains the high activity of copper-rich materials, but also overcomes their sintering shortcomings.

[0014] As a preferred embodiment, the catalyst has the chemical formula (Cu3MnNiFe)1Co2O4, (Cu2MgNiFe)1Co2O4, or (Cu2MnCrFe)1Co2O4.

[0015] A second aspect of the present invention also provides a method for preparing the above-mentioned spinel-structured copper-rich high-entropy composite oxide catalyst, comprising the following steps: S1. Dissolve a soluble salt of a metal element in water to form a mixed solution of metal salts, wherein the metal element includes Cu, Co, and three or four of Mg, Mn, Cr, Ni, Fe, and Zn. S2. Precipitation: Under stirring, slowly add Na2CO3 solution or (NH4)2CO3 solution to adjust the pH and then let stand. S3. Centrifuge, wash until pH neutral, and dry to obtain powder; S4. The powder is mixed with an organic molding agent, and after kneading, aging, extrusion molding, drying, and calcination, a strip-shaped catalyst is obtained.

[0016] Further, in step S1, the soluble salt is one or more of nitrate, acetate, and chloride.

[0017] Further, in step S1, Cu, Mg, Mn, Cr, Ni, Fe, and Zn are A-phase metal elements, and Co is a B-phase metal element. The molar ratio of the A-phase metal element to the B-phase metal element is (0.9–1.2):2, preferably (0.95–1.05):2. The molar content of Cu in the A-phase metal element is 20%–60%, preferably 40%–50%.

[0018] Further, in step S1, the total concentration of metal ions in the metal salt mixed solution is 0.1–3.0 mol / L, preferably 0.3–1.5 mol / L, and more preferably 0.5–1 mol / L.

[0019] Furthermore, in step S1, the dissolution temperature is 20℃~50℃, preferably 30℃~40℃.

[0020] Furthermore, in step S2, the precipitation time is 2 to 12 hours, preferably 4 to 8 hours.

[0021] Further, in step S2, the stirring rate is 200 rpm to 500 rpm, preferably 300 rpm to 400 rpm.

[0022] Further, in step S2, the concentration of the Na2CO3 solution or (NH4)2CO3 solution is 0.1–2.0 mol / L. -1 Preferably 0.5–1.0 mol L -1 .

[0023] Further, in step S2, the endpoint of pH adjustment is 9.0~10.0, preferably 9.0~9.5, and more preferably 9.2~9.3.

[0024] Furthermore, in step S2, the settling time is 20 to 60 minutes, preferably 30 to 40 minutes.

[0025] It should be noted that the settling process can promote particle growth, enhance structural stability, and prevent pore collapse during subsequent drying and calcination processes.

[0026] Furthermore, in step S3, the centrifugation speed is 3000 rpm to 5000 rpm, and the centrifugation time is 5 min to 10 min.

[0027] Furthermore, in step S3, the washing process involves resuspending the product in deionized water and washing it 3 to 5 times.

[0028] Further, in step S3, the drying is either atmospheric pressure heating drying or vacuum freeze-drying; the temperature for atmospheric pressure heating drying is 60℃~120℃, preferably 80℃~110℃, and the drying time is 6~24h, preferably 12~18h; the temperature for vacuum freeze-drying is -40℃~-60℃, and the vacuum degree is 10Pa~100Pa. Vacuum freeze-drying can avoid the pore collapse caused by capillary force during traditional drying, maintain the three-dimensional porous structure, increase the specific surface area, and significantly enhance the anti-sintering ability.

[0029] Further, in step S4, the organic forming agent is selected from one or more of glass fiber, titanium dioxide, hydroxypropyl methylcellulose, methylcellulose, polyvinyl alcohol, or guar gum powder. The amount of the organic forming agent is 1-10 wt% of the catalyst powder, preferably 3-7 wt%.

[0030] It should be noted that the addition of organic molding agents can provide adhesion, plasticity and extrusion molding properties, ensuring that the catalyst has good mechanical strength, and that it completely decomposes without residue after calcination, without affecting the catalyst activity.

[0031] Further, in step S4, the aging time is 12-48 hours, preferably 18-36 hours; the drying temperature is 60-120°C, preferably 80-110°C; and the drying time is 2-24 hours, preferably 4-12 hours.

[0032] Furthermore, the calcination temperature in step S4 is 350℃~550℃.

[0033] Furthermore, the calcination in step S4 adopts a programmed temperature increase method, specifically starting with a temperature increase of (2-3) °C min. -1 The temperature is increased to 350℃~400℃ at a rate of [temperature value] and held for 0.5h~3h, followed by [temperature value] at (3~5)℃ / min. -1 Heat to 450℃~550℃ and hold for 0.5h~3h.

[0034] The above technical solution not only removes organic components and forms a stable crystalline structure, but also effectively increases oxygen vacancies, improving the low-temperature activity and mechanical strength of the catalyst. The first stage, from room temperature to 350℃, is precisely the range where CO2 and NOx are violently released. Slow heating facilitates the gradual release of gases layer by layer, preventing the formation of "explosion" pores within the particles that could damage their structure. The heat preservation process allows for the full transformation of the amorphous phase into spinel nuclei, resulting in a high specific surface area. At this point, the framework is already formed. The second stage can accelerate heating and shorten the total time. 450–550℃ is the window for high-entropy ion interdiffusion, lattice distortion relaxation, and oxygen vacancy "forming." Heat preservation maintains a high specific surface area while improving structural order and thermal stability. Therefore, the above calcination method allows all steps, including nucleus formation and ion diffusion, to be completed within the most energy-efficient temperature range, while minimizing internal and external temperature stress, resulting in a more uniform material and optimal low-temperature catalytic performance while reducing performance fluctuations.

[0035] It should be noted that traditional high-entropy oxides require high temperatures to allow different metal ions to "diffuse over long distances" in order to form a uniform lattice; however, in this invention, each metal ion is pre-locked into the same precipitate in the liquid phase, and a high-entropy single-phase spinel structure can be obtained by "short-range rearrangement" at a low temperature of 350℃ to 550℃, which effectively reduces reaction conditions and energy consumption, and reduces catalyst sintering.

[0036] A third aspect of the present invention also provides the application of the above-described spinel-structured copper-rich high-entropy composite oxide catalyst in VOCs treatment.

[0037] It should be noted that the present invention does not have special requirements for the source of the VOCs, such as VOCs generated in chemical production, paint drying, food processing, crude oil refining, metal degreasing, paper manufacturing, textiles, etc.

[0038] This invention does not specify the particular type of VOCs; any volatile organic pollutant well-known in the art can be used. In the embodiments of this invention, toluene is specifically used to simulate volatile organic pollutants.

[0039] The present invention does not have special requirements for the conditions of the catalytic oxidation; well-known catalytic oxidation conditions in the art can be used.

[0040] Furthermore, the reaction temperature for the catalytic oxidation is 200–450 °C.

[0041] Furthermore, the catalyst can be used in series with a particulate filter (DPF).

[0042] III. Beneficial Effects Compared with the prior art, the present invention has the following advantages: 1. This invention provides a copper-rich high-entropy composite oxide catalyst with a spinel structure, its preparation method, and its application. Based on Co, the Cu content is increased, and 4-5 transition metals are introduced to match the catalyst's redox capacity and oxygen vacancy content, so that the C / C bond breaking rate matches the oxygen flow rate, thereby improving the catalyst's ability to deeply oxidize and mineralize VOCs. The low-temperature activity, deep mineralization, and anti-sintering performance are improved in one step by "lattice distortion, oxygen vacancy, and oxygen flow", which solves the problems of poor low-temperature activity, low mineralization rate, and poor stability of existing high-entropy metal oxide catalysts. 2. The catalyst of this invention is a single spinel-type copper-rich high-entropy composite oxide catalyst. It utilizes the "high-entropy spinel" structure and the retarded diffusion effect to lock Cu in the A site of the crystal lattice and inhibit its migration. This not only retains the high activity of copper-rich materials but also overcomes the sintering disadvantages, thus achieving a balance between catalytic activity and structural stability. 3. In step S4 of this invention, the two-stage high-temperature calcination at a lower temperature with a specific rate of programmed heating helps to avoid problems such as cracking of extruded strips, surface bulging, decreased strength of finished products, and catalyst sintering. It effectively increases oxygen vacancies, improves the low-temperature activity and mechanical strength of the catalyst, while reducing equipment load and energy consumption. The airflow distribution is better, which can further improve catalytic efficiency and reduce mineralization rate fluctuations. Attached Figure Description

[0043] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present invention and form part of this application, are not intended to limit the embodiments of the present invention.

[0044] Figure 1 The XRD patterns of the copper-rich high-entropy composite oxide catalysts prepared in Examples 1-3 are shown below. Figure 2 The curves showing the toluene conversion rate as a function of temperature for the copper-rich high-entropy composite oxide catalysts prepared in Examples 1-3 are shown. Figure 3 The curves showing the mineralization rate of the copper-rich high-entropy composite oxide catalysts prepared in Examples 1-3 as a function of temperature are shown. Figure 4 The curves showing the toluene conversion rate as a function of temperature for the high-entropy composite oxide catalysts prepared in Comparative Examples 1-3 are shown. Figure 5 The curves showing the mineralization rate of the high-entropy composite oxide catalysts prepared in Comparative Examples 1-3 as a function of temperature are shown. Figure 6 The curves showing the toluene conversion rate as a function of temperature for the non-high-entropy spinel catalysts prepared in Comparative Examples 4-6 are shown. Figure 7 The curves showing the mineralization rate of the non-high-entropy spinel catalysts prepared in Comparative Examples 4-6 as a function of temperature are shown. Figure 8The stability test results are shown for the copper-rich high-entropy composite oxide catalysts prepared in Examples 1-3. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The illustrative embodiments and descriptions of this invention are for illustrative purposes only and are not intended to limit the invention. The embodiments described below are some, but not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0046] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0047] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0048] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0049] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0050] Unless otherwise specified, the number of parts in this document refers to parts by mass.

[0051] To better illustrate the effectiveness of the technical solution in this embodiment, the following specific examples are provided: Example 1 A method for preparing a spinel-structured copper-rich high-entropy composite oxide catalyst includes the following steps: S1. Dissolve nitrates of metals such as Cu, Mn, Ni, Fe, and Co in water to form a mixed solution of metal salts, wherein the molar ratio of the metal elements such as Cu, Mn, Ni, Fe, and Co is 3:1:1:1:12. S2, after precipitation for 6 hours, while stirring at 300 rpm, slowly add Na2CO3 solution to adjust the pH to 9.3 and let stand for 30 minutes; S3. Centrifuge, resuspend in deionized water and wash 4 times until pH neutral, dry at 90℃ and normal pressure for 18h to obtain powder; S4. Mix 100 parts of the powder with 5 parts of methylcellulose, knead, age for 18 hours, extrude, and dry at 100°C for 6 hours. Then, in an air atmosphere, first heat at 2°C for 1 minute... -1 The temperature was increased to 400℃ and held for 1 hour at a rate of 5℃ / min. -1 The strip-shaped catalyst (Cu3MnNiFe)1Co2O4 was prepared by heating to 500℃ and then holding at that temperature for 1 hour.

[0052] Example 2 This embodiment is based on Example 1, and the only difference from Example 1 is that step S1 of Example 1 is replaced by the following steps: dissolving nitrates of metals such as Cu, Mg, Ni, Fe, and Co in water to form a mixed metal salt solution, wherein the molar ratio of the metal elements Cu, Mg, Ni, Fe, and Co is 2:1:1:1:10. The resulting catalyst is (Cu2MgNiFe)1Co2O4.

[0053] Example 3 This embodiment is based on Example 1, and the only difference from Example 1 is that step S1 of Example 1 is replaced by the following steps: dissolving nitrates of metals such as Cu, Mn, Cr, Fe, and Co in water to form a mixed metal salt solution, wherein the molar ratio of the metal elements Cu, Mn, Cr, Fe, and Co is 2:1:1:1:10. The resulting catalyst is (Cu₂MnCrFe)₁Co₂O₄.

[0054] Example 4 A method for preparing a spinel-structured copper-rich high-entropy composite oxide catalyst includes the following steps: S1. Dissolve nitrates of metals such as Cu, Mn, Ni, Fe, and Co in water to form a mixed solution of metal salts, wherein the molar ratio of the metal elements such as Cu, Mn, Ni, Fe, and Co is 3:1:1:1:12.6; S2. After precipitation for 4 hours, while stirring at 400 rpm, slowly add (NH4)2CO3 solution to adjust the pH to 9.0 and let stand for 40 minutes. S3. Centrifuge, resuspend in deionized water and wash 3 times until pH neutral, dry at 100℃ and normal pressure for 12h to obtain powder; S4. Mix 100 parts of the powder with 7 parts of polyvinyl alcohol, knead, age for 24 hours, extrude, and dry at 110°C for 4 hours. Then, in an air atmosphere, first heat at 3°C ​​for 1 minute... -1 The temperature was increased to 350℃ and held for 2 hours at a rate of 4℃ / min. -1 The strip-shaped catalyst (Cu3MnNiFe)1Co2O4 was prepared by heating to 550℃ and then holding at that temperature for 1 hour.

[0055] Example 5 A method for preparing a spinel-structured copper-rich high-entropy composite oxide catalyst includes the following steps: S1. Dissolve nitrates of metals such as Cu, Mn, Ni, Fe, and Co in water to form a mixed solution of metal salts, wherein the molar ratio of the metal elements such as Cu, Mn, Ni, Fe, and Co is 3:1:1:1:11.4. S2. After precipitation for 8 hours, while stirring at 350 rpm, slowly add Na2CO3 solution to adjust the pH to 9.5 and let stand for 35 minutes. S3. Centrifuge, resuspend in deionized water and wash 5 times until pH neutral, dry at 110℃ and normal pressure for 12h to obtain powder; S4. Mix 100 parts of the powder with 3 parts of hydroxypropyl methylcellulose, knead, age for 36 hours, extrude, and dry at 80°C for 12 hours. Then, in an air atmosphere, first heat at 2°C for 1 minute... -1 The temperature was increased to 350℃ and held for 1 hour at a rate of 3℃ / min. -1 The strip-shaped catalyst (Cu3MnNiFe)1Co2O4 was prepared by heating to 500℃ and then holding at that temperature for 1 hour.

[0056] Example 6 This embodiment is based on Embodiment 1, and the only difference from Embodiment 1 is that: in this embodiment, the programmed temperature rise is not performed in step S4, but a rapid temperature rise method is used for calcination, that is, "rapidly heat to 500℃ and hold for 2 hours" is used instead of "first heat at 2℃ for 2 minutes in air atmosphere" in step S4 of Embodiment 1. -1 The temperature was increased to 400℃ and held for 1 hour at a rate of 5℃ / min. -1 Heat to 500℃ and hold for 1 hour for calcination.

[0057] Example 7 This embodiment is based on Embodiment 1, and the only difference from Embodiment 1 is that the following steps are used instead of step S4 in Embodiment 1, which involves "first setting the temperature in an air atmosphere at 2°C for 1 minute". -1 The temperature was increased to 400℃ and held for 1 hour at a rate of 5℃ / min.-1 "Heat to 500℃ and then hold for 1 hour for calcination": First, in the air atmosphere, at 5°C min -1 The temperature was increased to 400℃ and held for 1 hour at a rate of 2℃ / min. -1 Heat to 500℃ and hold for 1 hour before calcining.

[0058] Example 8 This embodiment is based on Embodiment 1, and the only difference from Embodiment 1 is that the holding temperature of the second stage of calcination in step S4 is modified to 900℃, that is, the following steps are used instead of "first in an air atmosphere at 2℃ for 2 minutes" in step S4 of Embodiment 1. -1 The temperature was increased to 400℃ and held for 1 hour at a rate of 5℃ / min. -1 "Heat to 500℃ and then hold for 1 hour for calcination": First, in the air atmosphere, at 5°C min -1 The temperature was increased to 400℃ and held for 1 hour at a rate of 2℃ / min. -1 Heat to 900℃ and hold for 1 hour before calcining.

[0059] Comparative Example 1 This comparative example is based on Example 1, and differs from Example 1 only in that the molar ratio of the metal elements Cu, Mn, Ni, Fe, and Co in step S1 is 1:1:1:1:8. The catalyst obtained is (CuMnNiFe)1Co2O4.

[0060] Comparative Example 2 This comparative example is based on Example 2, and the only difference from Example 2 is that the molar ratio of the metal elements Cu, Mg, Ni, Fe, and Co in step S1 is 1:1:1:1:8. The catalyst obtained is (CuMgNiFe)1Co2O4.

[0061] Comparative Example 3 This comparative example is based on Example 1, and differs from Example 1 only in that the molar ratio of the metal elements Cu, Mn, Cr, Fe, and Co in step S1 is 1:1:1:1:8. The catalyst obtained is (CuMnCrFe)1Co2O4.

[0062] Comparative Example 4 This comparative example is based on Example 1, with the only difference being that the metal elements mentioned in step S1 only involve Cu and Co, excluding metals such as Mg, Mn, Cr, Ni, Fe, and Zn. Specifically, step S1 in Example 1 is modified to: dissolving Cu and Co nitrates in water to form a mixed metal salt solution, with a Cu to Co molar ratio of 1:2. The resulting catalyst is CuCo₂O₄.

[0063] Comparative Example 5 This comparative example is based on Example 1, with the only difference being that the metal elements mentioned in step S1 only involve Cu and Co, excluding metals such as Mg, Mn, Cr, Ni, Fe, and Zn. Specifically, step S1 in Example 1 is modified to: dissolving Cu and Co nitrates in water to form a mixed metal salt solution, with a Cu to Co molar ratio of 1:1. The resulting catalyst is Cu₂Co₂O₄.

[0064] Comparative Example 6 This comparative example is based on Example 1, with the only difference being that the metal element mentioned in step S1 only involves Co, excluding metals such as Cu, Mg, Mn, Cr, Ni, Fe, and Zn. Specifically, step S1 in Example 1 is modified to dissolve Co nitrate in water to form a metal salt solution. The resulting catalyst is Co3O4.

[0065] Comparative Example 7 This comparative example is based on Example 1, and the only difference from Example 1 is that the molar ratio of the metal elements Cu, Mn, Ni, Fe, Co and others in step S1 is 3:1:1:1:8.

[0066] Comparative Example 8 This comparative example is based on Example 1, and the only difference from Example 1 is that the molar ratio of the metal elements Cu, Mn, Ni, Fe, Co and others in step S1 is 3:1:1:1:15.

[0067] Catalyst performance evaluation: 1. Crystal phase composition To investigate the crystal phase composition and structure of the prepared catalysts, the copper-rich high-entropy catalysts (Cu3MnNiFe)1Co2O4, (Cu2MgNiFe)1Co2O4, and (Cu2MnCrFe)1Co2O4 prepared in Examples 1-3 were subjected to XRD tests. Figure 1 ).from Figure 1 It can be seen that the main diffraction peaks of the copper-rich high-entropy catalysts prepared in Examples 1-3 of this invention are all 19.0° (111), 31.3° (220), 36.9° (311), 44.9° (400), 59.2° (511), and 65.2° (440), which conform to the cubic spinel structure of PDF#43-1003, and there are no other impurity peaks. This proves that the copper-rich high-entropy catalysts prepared in Examples 1-3 of this invention all have a single spinel structure, no phase separation, and a stable structure.

[0068] 2. Low-temperature catalytic performance The catalysts prepared in Examples 1-3 and Comparative Examples 1-6 were used for the catalytic oxidation of toluene, and their performance was tested. The reactants and products of toluene oxidation before and after catalytic oxidation were detected and quantitatively analyzed. The toluene conversion and mineralization rate of each sample under different temperature conditions were calculated. The results are shown in [Figure Number]. Figure 2-6 The catalyst dosage was 0.5 g, the gas flow rate was 180 ml / min, the initial mixed gas concentration was 500 ppm toluene, the oxygen content was 20%, and the overall space velocity (OSV) of the reaction environment was 30,000 h⁻¹. -1 .

[0069] Figure 2-3 The figures show the toluene conversion and mineralization rates of the copper-rich high-entropy catalysts prepared in Examples 1-3 as a function of temperature. Figure 2-3 It can be seen that the copper-rich high-entropy catalysts (Cu3MnNiFe)1Co2O4, (Cu2MgNiFe)1Co2O4, and (Cu2MnCrFe)1Co2O4 prepared in Examples 1-3 all exhibit excellent low-temperature catalytic activity. Among them, (Cu3MnNiFe)1Co2O4 shows the best low-temperature catalytic activity, and the temperature (T) required for the toluene conversion rate to reach 90% is [not specified in the original text]. 90 The conversion rate of toluene reaches 100% at 197℃ and 200℃, and the mineralization rate reaches over 90% at 212℃. The low-temperature catalytic activity of (Cu2MgNiFe)1Co2O4 and (Cu2MnCrFe)1Co2O4 decreases sequentially compared to (Cu3MnNiFe)1Co2O4.

[0070] Figure 4-5 The figures show the toluene conversion and mineralization rates of the high-entropy catalysts prepared in Comparative Examples 1-3 as a function of temperature. It can be seen that the low-temperature catalytic activity of Comparative Examples 1-3 is reduced to varying degrees compared to Examples 1-3. For example, the only difference between (CuMnNiFe)1Co2O4 in Comparative Example 1 and (Cu3MnNiFe)1Co2O4 in Example 1 is the Cu content in the catalyst, and their temperature T... 90 The mineralization rate was significantly reduced in the temperature range of 180℃ to 220℃ when the temperature was increased from 197℃ in Example 1 to 220℃. This indicates that increasing the copper content in the catalyst can significantly improve its low-temperature catalytic activity. This proves that the present invention uses a high-entropy spinel structure to stabilize copper ions, which can effectively increase the copper content in the catalyst and improve the low-temperature catalytic activity of the catalyst.

[0071] Figure 6-7The figures show the toluene conversion and mineralization rates as a function of temperature for the non-high-entropy spinel catalysts prepared in Comparative Examples 4-6. Comparative Examples 4-5 also consisted of copper-rich components, while Comparative Example 6 was pure Co3O4. It can be seen that, compared to Example 1, the toluene conversion rate of Comparative Examples 4-6 was significantly lower in the lower temperature range of 180℃ to 220℃, and the mineralization rate was significantly lower than that of Examples 1-3 and Comparative Examples 1-3. Especially in the plateau region of 220℃ to 280℃, the mineralization rate of Comparative Examples 4-6 remained consistently around 80%, while that of Examples 1-3 was above 90%. This indicates that, compared to non-high-entropy catalysts, the copper-rich, high-entropy pure spinel structure catalyst of this invention has higher low-temperature toluene conversion and mineralization rates, meaning that this invention has better low-temperature catalytic activity. This proves that the copper-rich, high-entropy pure spinel structure of this invention is beneficial for improving the low-temperature catalytic activity of the catalyst, especially the mineralization rate.

[0072] 3. Stability 1) Long-term stability Stability tests were conducted on the copper-rich high-entropy catalysts prepared in Examples 1-3. 0.2 g samples were taken for each catalyst. The catalyst (Cu3MnNiFe)1Co2O4 prepared in Example 1 was tested at 200℃, the catalyst (Cu2MgNiFe)1Co2O4 prepared in Example 2 at 220℃, and the catalyst (Cu2MnCrFe)1Co2O4 prepared in Example 3 at 250℃ (all three catalysts were tested at the temperatures required for 100% toluene conversion). A continuous 48-hour toluene catalytic oxidation reaction was performed. The results are shown in the figure. Figure 8 .

[0073] like Figure 8 As shown, the copper-rich high-entropy catalysts prepared in Examples 1-3 of this invention maintained a toluene conversion rate of over 99% for 48 hours of continuous operation, demonstrating that the spinel-structured copper-rich high-entropy catalysts of this invention possess excellent long-term stability.

[0074] 2) Resistance to water and heat aging To investigate the effects of different catalyst compositions and preparation processes on the low-temperature catalytic activity and stability of catalysts before and after aging, the catalysts prepared in Examples 1-8 and Comparative Examples 1-8 were subjected to catalyst performance tests. Subsequently, each catalyst sample was subjected to hydrothermal aging at 800°C for 10 hours in an air atmosphere containing 10% water vapor. The temperature T required for each catalyst to achieve a toluene conversion rate of 90% before and after hydrothermal aging was determined. 90 And calculate its T before and after aging. 90 The changes in the values ​​are shown in Table 1.

[0075] Table 1. T90 test results of different catalyst samples before and after hydrothermal aging As can be seen from Table 1, the copper-rich high-entropy catalysts prepared in Examples 1-5 of this invention, after hydrothermal aging at 800℃ for 10 h, [the following parameters are observed: T]. 90 The changes were all below 6°C, demonstrating excellent hydrothermal stability; compared with Example 1, Examples 6-8 showed that the T before aging was... 90 T before and after aging 90 The changes all showed an increase to some extent, indicating that the method of preparing the catalyst by calcining with a specific temperature change rate in this invention is beneficial to improving the low-temperature catalytic performance and hydrothermal stability of the catalyst. Comparative Examples 1-3 and Examples 1-5 before and after aging T 90 The changes were basically the same, indicating that the high-entropy spinel structure can effectively increase the hydrothermal stability of the catalyst. Compared with Example 1, Comparative Examples 4-6 showed differences in T before and after aging. 90 The significant increase in the change value indicates that, compared with ordinary non-high-entropy catalysts, the copper-rich, high-entropy pure spinel structure catalyst of the present invention has better hydrothermal stability, proving that the combination of copper-rich, high-entropy and pure spinel structure of the present invention is beneficial to improving the hydrothermal stability of the catalyst while improving the low-temperature catalytic performance of the catalyst. Compared with Example 1, Comparative Examples 7-8 showed that, regardless of the T before aging... 90 T before and after aging 90 The changes all showed a certain degree of increase, indicating that the molar ratio of phase A metal elements to phase B metal elements within a specific range in this invention is beneficial to improving the low-temperature catalytic performance and hydrothermal stability of the catalyst.

[0076] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A copper-rich, high-entropy composite oxide catalyst with a spinel structure, characterized in that, The catalyst contains three or four of the following metal elements: Cu, Co, Mg, Mn, Cr, Ni, Fe, and Zn.

2. The catalyst according to claim 1, characterized in that: The chemical formulas of the catalysts are (Cu3MnNiFe)1Co2O4, (Cu2MgNiFe)1Co2O4, and (Cu2MnCrFe)1Co2O4.

3. A method for preparing a copper-rich high-entropy composite oxide catalyst with a spinel structure as described in any one of claims 1 to 2, characterized in that, Includes the following steps: S1. Dissolve a soluble salt of a metal element in water to form a mixed solution of metal salts, wherein the metal element includes Cu, Co, and three or four of Mg, Mn, Cr, Ni, Fe, and Zn. S2. Precipitation: Under stirring, slowly add Na2CO3 solution or (NH4)2CO3 solution to adjust the pH and then let stand. S3. Centrifuge, wash until pH neutral, and dry to obtain powder; S4. The powder is mixed with an organic molding agent, and after kneading, aging, extrusion molding, drying, and calcination, a strip-shaped catalyst is obtained.

4. The preparation method according to claim 3, characterized in that: In step S1, the soluble salt is one or more of nitrate, acetate, or chloride.

5. The preparation method according to claim 3, characterized in that: In step S1, Cu, Mg, Mn, Cr, Ni, Fe, and Zn are A-phase metal elements, and Co is a B-phase metal element. The molar ratio of A-phase metal elements to B-phase metal elements is (0.9-1.2):

2. The molar content of Cu in the A-phase metal elements is 20%-60%.

6. The preparation method according to claim 3 or 5, characterized in that: In step S2, the sedimentation time is 2 to 12 hours; the stirring rate is 200 rpm to 500 rpm; and the pH adjustment endpoint is 9.0 to 10.

0.

7. The preparation method according to claim 3 or 5, characterized in that: In step S3, the centrifugation speed is 3000 rpm to 5000 rpm, and the centrifugation time is 5 min to 10 min; the washing is resuspending and washing with deionized water 3 to 5 times; and the drying is atmospheric pressure heating drying or vacuum freeze drying.

8. The preparation method according to claim 3 or 5, characterized in that: In step S4, the aging time is 12–48 h; the drying temperature is 60–120 °C; the drying time is 2–24 h; and the calcination temperature range is 350–550 °C.

9. The preparation method according to claim 9, characterized in that: In step S4, the calcination is carried out using a programmed temperature increase method, specifically by first increasing the temperature by (2-3) °C per minute. -1 The temperature is increased to 350℃~400℃ at a rate of [temperature value] and held for 0.5h~3h, followed by [temperature value] at (3~5)℃ / min. -1 Heat to 450℃~550℃ and hold for 0.5h~3h.

10. The application of a copper-rich high-entropy composite oxide catalyst with a spinel structure as described in any one of claims 1 to 2, or a copper-rich high-entropy composite oxide catalyst with a spinel structure prepared by the preparation method described in any one of claims 3 to 9, in the field of VOCs treatment.

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