Ce-doped Co-MOF derived CuO composite oxide catalyst and preparation method thereof

Abstract

The application discloses a Ce-doped Co-MOF derived CuO composite oxide catalyst and a preparation method thereof, and belongs to the technical field of catalytic materials. The preparation method comprises the following steps: S1, obtaining rare earth waste residue containing Ce elements and Co elements, and processing the rare earth waste residue to obtain a cerium salt solution and a cobalt salt solution; S2, mixing the cerium salt solution and the cobalt salt solution with an organic ligand to prepare a Ce-Co-MOF precursor; S3, performing calcination and annealing treatment to obtain a Ce-Co-O porous composite oxide carrier; S4, preparing a copper salt solution, impregnating the Ce-Co-O porous composite oxide carrier with the copper salt solution, and then performing drying and calcination treatment to obtain a CuO@Ce-Co-O composite oxide; and S5, performing surface plasmon activation treatment to obtain the Ce-doped Co-MOF derived CuO composite oxide catalyst. The application can realize high-value utilization of rare earth resources and precise structure regulation of catalytic materials, and the prepared catalyst can exhibit excellent activity and stability in a low-temperature CO oxidation reaction.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials technology, and in particular to a Ce-doped Co-MOF-derived CuO composite oxide catalyst and its preparation method. Background Technology

[0002] Ce-Co based oxides exhibit excellent redox properties in low-temperature CO catalytic oxidation; however, their traditional preparation routes rely on high-purity chemical reagents, failing to balance resource utilization and cost control. On the other hand, rare earth smelting tailings and cobalt ore waste contain abundant Ce, Co, and trace amounts of beneficial elements such as Fe and Ni. How to achieve high-value utilization of these rare earth wastes, and even synergistic effects with Ce-Co based oxides, is a pressing research topic that could provide new insights for current research on green catalytic materials. Summary of the Invention

[0003] To address the above problems, this invention aims to provide a Ce-doped Co-MOF-derived CuO composite oxide catalyst and its preparation method.

[0004] The technical solution of the present invention is as follows:

[0005] On the one hand, a method for preparing a Ce-doped Co-MOF-derived CuO composite oxide catalyst is provided, comprising the following steps:

[0006] S1: Obtain rare earth waste containing Ce and Co elements, and perform cerium source and cobalt source extraction treatment on the rare earth waste to obtain cerium salt solution and cobalt salt solution.

[0007] S2: The cerium salt solution and the cobalt salt solution are mixed with organic ligands to form Ce-Co-MOF crystals through a self-assembly reaction. After the reaction is completed, the mixture is centrifuged, washed, and dried to obtain the Ce-Co-MOF precursor.

[0008] S3: The Ce-Co-MOF precursor is calcined and annealed to obtain a Ce-Co-O porous composite oxide support;

[0009] S4: Prepare a copper salt solution and impregnate the Ce-Co-O porous composite oxide support with the copper salt solution. Then, dry and calcine the impregnated sample to obtain CuO@Ce-Co-O composite oxide.

[0010] S5: The CuO@Ce-Co-O composite oxide is subjected to surface plasma activation treatment to obtain the Ce-doped Co-MOF-derived CuO composite oxide catalyst.

[0011] Preferably, step S1, which involves extracting cerium and cobalt sources from the rare earth waste residue, specifically includes the following sub-steps:

[0012] S11: The rare earth waste residue is coarsely ground and homogenized to obtain a powder sample;

[0013] S12: The powder sample is subjected to acid leaching treatment with nitric acid solution, and the leaching solution is obtained by filtration.

[0014] S13: Add oxalic acid solution to the first acid leaching solution and adjust the pH of the system to 1-2 so that rare earth ions react with oxalate ions to form insoluble rare earth oxalate precipitate. Centrifuge and wash to obtain precipitate one and acid leaching solution two.

[0015] S14: The precipitate is calcined to obtain a mixed oxide containing Ce, and then the mixed oxide is dissolved in acid to prepare a salt solution containing Ce. The salt solution is extracted and the extracted phase is back-extracted to obtain the cerium salt solution.

[0016] S15: Adjust the pH of the second acid leaching solution to 7-9 to selectively precipitate cobalt ions in the form of hydroxides. Centrifuge, wash, and dry to obtain precipitate two. Dissolve precipitate two in acid to obtain the cobalt salt solution.

[0017] Preferably, in step S15, when adjusting the pH of the second acid leaching solution, the adjusting agent used is any one of ammonia, urea, ammonium carbonate, ammonium bicarbonate, hexamethylenetetramine, and hydroxylamine.

[0018] Preferably, in step S2, when mixing, the molar ratio of the cerium salt solution, cobalt salt solution and organic ligand is x:1-x:10, where 0 < x < 0.3.

[0019] Preferably, in step S2, the self-assembly reaction is carried out in an ultrasonic-microwave synergistic reactor, with an ultrasonic frequency of 30~50 kHz, a microwave power of 500~700 W, a temperature of 110~130 ℃, and a time of 10~12 h.

[0020] Preferably, in step S3, during calcination, the temperature is first raised to 300-350°C in nitrogen at a rate of 2-3°C / min and held for 2-2.5 h, and then raised to 450-500°C in a 5% O2 / Ar mixed atmosphere at a rate of 3-5°C / min and held for 3-3.5 h; during annealing, the annealing is carried out in an air atmosphere for 30-40 min.

[0021] Preferably, in step S4, the copper salt solution is a copper nitrate solution, and the impregnation is performed using an atomized equal-volume impregnation method.

[0022] Preferably, in step S4, during calcination, the temperature is first raised to 200-300℃ in nitrogen at a rate of 4-6℃ / min and held for 1-2 hours, and then raised to 400-500℃ in air and held for 3-4 hours.

[0023] Preferably, in step S5, when performing surface plasma activation treatment, the surface carbon residue is first removed and active oxygen sites are introduced in a high-frequency low-pressure plasma reaction system, and then the surface is treated by an in-situ electrospray ion beam surface reconstruction device to enhance the electronic coupling of the CuO and Ce-Co phase interface and maximize the catalytic activity.

[0024] On the other hand, a Ce-doped Co-MOF-derived CuO composite oxide catalyst is also provided, which is prepared by the preparation method of the Ce-doped Co-MOF-derived CuO composite oxide catalyst described in any one of the above-mentioned methods.

[0025] The beneficial effects of this invention are:

[0026] This invention enables the high-value utilization of rare earth resources and precise structural control of catalytic materials. The resulting catalyst exhibits excellent activity and stability in low-temperature CO oxidation reactions. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic flowchart of the preparation method of the Ce-doped Co-MOF-derived CuO composite oxide catalyst of the present invention;

[0029] Figure 2 This is a schematic diagram showing the performance test results of the catalysts in Examples 1-2 and Comparative Examples 1-5;

[0030] Figure 3 A schematic diagram showing the comparison of sulfur resistance test results between unsupported CuO and supported CuO catalysts;

[0031] Figure 4 This is a schematic diagram comparing the hydrophobic angles of unsupported CuO and supported CuO catalysts; where a is the hydrophobic angle of the unsupported CuO Ce2Co8-O (rare earth waste) catalyst in Comparative Example 4, and b is the hydrophobic angle of the CuO@Ce2Co8-O (rare earth waste) catalyst in Example 2.

[0032] Figure 5 Raman spectra of the catalysts in Examples 1-2 and Comparative Examples 1-3 are shown below.

[0033] Figure 6 XPS spectra of catalysts in Examples 1-2 and Comparative Examples 1-3; where (a) is the fitted spectrum of Ce 3d and (b) is the fitted spectrum of Co 2p.

[0034] Figure 7 The images show the electron microscope (EM) images of the catalysts in Examples 1-2 and Comparative Examples 1-3; where (a) is the electron microscope image of the Co8Ce2-MOF sample obtained in step (8) of Example 2, and (b) is... Figure 7 (a) is a magnified view of a portion of the sample; (c) is a micro-electron micrograph of the Co8Ce2-O sample obtained in step (9) of Example 2; (d) is... Figure 7 (c) is a magnified view of a portion of the catalyst, (e) is a micro-electron micrograph of the catalyst of Comparative Example 1, (f) is a micro-electron micrograph of the catalyst of Example 1, (g) is a micro-electron micrograph of the catalyst of Example 2, (h) is a micro-electron micrograph of the catalyst of Comparative Example 2, and (i) is a micro-electron micrograph of the catalyst of Comparative Example 3. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0036] On the one hand, such as Figure 1 As shown, this invention provides a method for preparing a Ce-doped Co-MOF-derived CuO composite oxide catalyst, comprising the following steps:

[0037] S1: Obtain rare earth waste containing Ce and Co elements, and perform cerium source and cobalt source extraction treatment on the rare earth waste to obtain cerium salt solution and cobalt salt solution.

[0038] In one specific embodiment, the rare earth waste residue is rare earth smelting waste residue, mainly containing CeO2 10~20 wt%, Fe2O3 8~15 wt%, SiO2 30~40 wt%, and small amounts of Co, La, and Nd.

[0039] In a specific embodiment, the cerium and cobalt source extraction treatment of the rare earth waste residue specifically includes the following sub-steps:

[0040] S11: The rare earth waste residue is coarsely ground and homogenized to obtain a powder sample;

[0041] S12: The powder sample is subjected to acid leaching treatment with nitric acid solution, and the leaching solution is obtained by filtration.

[0042] In this step, nitric acid solution is used. It is a strong acid that can perform acid leaching treatment, and its acid anions do not affect the subsequent synthesis process. After calcination, there will be no residue of nitrate ions, thus avoiding any impact on subsequent steps.

[0043] S13: Add oxalic acid solution to the first acid leaching solution and adjust the pH of the system to 1-2 so that rare earth ions react with oxalate ions to form insoluble rare earth oxalate precipitate. Centrifuge and wash to obtain precipitate one and acid leaching solution two.

[0044] S14: The precipitate is calcined to obtain a mixed oxide containing Ce, and then the mixed oxide is dissolved in acid to prepare a salt solution containing Ce. The salt solution is extracted and the extracted phase is back-extracted to obtain the cerium salt solution.

[0045] S15: Adjust the pH of the second acid leaching solution to 7-9 to selectively precipitate cobalt ions in the form of hydroxides. Centrifuge, wash, and dry to obtain precipitate two. Dissolve precipitate two in acid to obtain the cobalt salt solution.

[0046] In one specific embodiment, in step S15, when adjusting the pH of the second acid leaching solution, the adjusting agent used is any one of ammonia, urea, ammonium carbonate, ammonium bicarbonate, hexamethylenetetramine, and hydroxylamine. In this embodiment, a mild alkaline reagent / precipitant is used as the adjusting agent, which can provide OH- - Alternatively, the pH can be adjusted to allow metal ions to precipitate slowly and evenly, avoiding localized excessive alkalinity.

[0047] It should be noted that the cobalt and cerium source extraction and purification methods in the above embodiments are only preferred methods of the present invention. Other methods in the prior art that can extract and purify cobalt and cerium sources from rare earth waste residues can also be applied to the present invention.

[0048] S2: The cerium salt solution and the cobalt salt solution are mixed with organic ligands to form Ce-Co-MOF crystals through a self-assembly reaction. After the reaction is completed, the mixture is centrifuged, washed, and dried to obtain the Ce-Co-MOF precursor.

[0049] In one specific embodiment, when mixing, the molar ratio of the cerium salt solution, cobalt salt solution and organic ligand is x:1-x:10, where 0 < x < 0.3.

[0050] In one specific embodiment, the self-assembly reaction is carried out in an ultrasonic-microwave synergistic reactor, with an ultrasonic frequency of 30-50 kHz, a microwave power of 500-700 W, a temperature of 110-130 ℃, and a time of 10-12 h.

[0051] In the above embodiments, the self-assembly reaction is carried out in an ultrasonic-microwave synergistic reactor. The synergistic effect of microwave bulk heating and ultrasonic cavitation can significantly shorten the reaction time and produce high-performance catalysts with smaller particle size, more uniform distribution, and more concentrated active component loading.

[0052] S3: The Ce-Co-MOF precursor is calcined and annealed to obtain a Ce-Co-O porous composite oxide support.

[0053] In one specific embodiment, during calcination, the temperature is first raised to 300-350°C in nitrogen at a rate of 2-3°C / min and held for 2-2.5 h, and then raised to 450-500°C in a 5% O2 / Ar mixed atmosphere (i.e., 5% O2 and 95% Ar) at a rate of 3-5°C / min and held for 3-3.5 h; during annealing, the annealing is carried out in an air atmosphere for 30-40 min.

[0054] In the above embodiments, multi-atmosphere segmented calcination can precisely control the reaction environment (such as oxidizing, inert, and reducing atmospheres) at different temperature stages. It can gradually and selectively remove template agents, regulate the valence state and crystal structure of active components, and create abundant channels and surface defects while protecting the catalyst framework, thereby synergistically optimizing the activity, selectivity and stability of the catalyst.

[0055] S4: Prepare a copper salt solution and impregnate the Ce-Co-O porous composite oxide support with the copper salt solution. Then, dry and calcine the impregnated sample to obtain CuO@Ce-Co-O composite oxide.

[0056] In one specific embodiment, the copper salt solution is a copper nitrate solution, and impregnation is performed using an atomized equal-volume impregnation method. In this embodiment, the atomized equal-volume impregnation method can atomize the active component precursor solution into tiny droplets and allow them to be adsorbed onto the support at the same volume. This achieves an extremely uniform distribution of the active component on the support surface and within the pores, thereby effectively preventing local aggregation and significantly improving the utilization rate of the catalyst's active sites and overall stability.

[0057] In one specific embodiment, during calcination, the temperature is first raised to 200-300°C in nitrogen at a rate of 4-6°C / min and held for 1-2 hours, and then raised to 400-500°C in air and held for 3-4 hours.

[0058] In the above embodiments, multi-atmosphere segmented calcination can precisely control its valence state and particle size under inert or reducing atmospheres, thereby suppressing agglomeration, improving dispersion, and then using an air atmosphere to fully decompose the copper precursor into uniform CuO to obtain the optimal active center structure.

[0059] S5: The CuO@Ce-Co-O composite oxide is subjected to surface plasma activation treatment to obtain the Ce-doped Co-MOF-derived CuO composite oxide catalyst.

[0060] In one specific embodiment, during surface plasma activation treatment, surface carbon residues are first removed and active oxygen sites are introduced in a high-frequency low-pressure plasma reaction system, and then the surface is treated by an in-situ electrospray ion beam surface reconstruction device to enhance the electronic coupling of the CuO and Ce-Co phase interface and maximize catalytic activity.

[0061] On the other hand, the present invention also provides a Ce-doped Co-MOF-derived CuO composite oxide catalyst, which is prepared by the preparation method of the Ce-doped Co-MOF-derived CuO composite oxide catalyst described in any one of the above-mentioned methods.

[0062] Example 1

[0063] A Ce-doped Co-MOF-derived CuO composite oxide catalyst is prepared by the following steps:

[0064] (1) Obtain rare earth waste residue and grind it in a planetary ball mill at 400 rpm for 3 h. The average particle size of the obtained powder is about 10 μm, indicating that it has good reactivity and specific surface area. The powder is fully mixed and fined before use.

[0065] (2) The above powder sample was mixed with nitric acid solution (concentration 3 mol / L) at a solid-liquid ratio of 1:10 (g / mL), and the mixture was magnetically stirred in a constant temperature water bath at 90 ℃ for 4 h. After the reaction was completed, the solid and liquid phases were separated by filtration. The resulting filtrate (acid leaching solution one) contained Ce. 3+ Co 2+ Fe 3+ La 3+ Multiple metal ions are used as the base solution for subsequent separation.

[0066] (3) To selectively precipitate rare earth elements, a 10 wt% oxalic acid solution was slowly added dropwise to the first acid leaching solution, and the pH of the system was adjusted to approximately 1.5. At this point, rare earth ions react with oxalate ions to form insoluble rare earth oxalate precipitates, while most impurities such as iron and cobalt remain in the solution. The resulting precipitate was centrifuged, washed several times with deionized water, and then calcined at 600 °C for 2 h to generate Ce-La mixed oxides;

[0067] (4) Dissolve the obtained oxide in 0.5 mol / L HNO3 to prepare a Ce-containing solution. 3+ La 3+ The nitrate solution was used. Liquid-liquid extraction was performed using the organophosphate extractant D2EHPA (di(2-ethylhexyl) phosphate) to separate Ce. 3+ and La 3+ The extracted phase was back-extracted to obtain high-purity Ce. 3+ A nitrate solution with a concentration of approximately 0.3 mol / L is denoted as solution A.

[0068] (5) The acid leaching solution still contains a high concentration of Co after rare earth separation. 2+ Fe 3+ Plasma. To recover cobalt, the pH of the filtrate was slowly adjusted to 7.5 with ammonia, causing cobalt ions to selectively precipitate as hydroxides. The resulting precipitate was centrifuged, washed with deionized water, and dried at 60 °C. It was then dissolved in 1 mol / L HNO3 to obtain Co. 2+ The nitrate solution, with a concentration controlled at 0.3 mol / L, is denoted as solution B;

[0069] (6) Prepare a 0.3 mol / L anhydrous ethanol solution of 2-methylimidazole. Control the molar ratio of solution A to solution B to be Ce:Co:ligand = 0.1:0.9:10. Add and mix the solutions simultaneously in a continuous microfluidic mixing reactor at a flow rate of 1.5 mL / min. Maintain the reaction system temperature at 40 °C.

[0070] (7) The above reaction system was stirred at 40 °C for 40 min to form a uniform mixture; then a self-assembly reaction was carried out in an ultrasonic-microwave synergistic reactor: ultrasonic frequency 40 kHz, microwave power 600 W, temperature 120 °C, reaction time 10~12 h, to form uniform Ce-Co-MOF crystals.

[0071] (8) After the reaction was completed, the solid was separated by a magnetic levitation centrifugation system, washed three times with an ethanol-deionized water mixture, and dried at -40 °C for 6 h in a vacuum freeze dryer to obtain the Ce-Co-MOF precursor;

[0072] (9) The Ce-Co-MOF precursor was placed in a dual-zone programmable atmosphere calcination furnace. In the first stage, the temperature was raised to 300 °C at 2 °C / min and held for 2 h in nitrogen (99.999%) to remove organic residues. In the second stage, the temperature was switched to a 5% O2 / Ar mixed atmosphere and raised to 500 °C at 3 °C / min and held for 3 h to achieve complete decomposition of the organic framework and reconstruction of the metal oxide phase. Finally, the precursor was annealed in air for 30 min to obtain the Ce-Co-O porous composite oxide support.

[0073] (10) The Ce-Co-O porous composite oxide support was placed in an atomizing equal-volume impregnation reactor, and a mixture containing 7 wt% Cu was sprayed in through an ultrasonic atomization system. 2+ The copper nitrate solution was sprayed at a rate of 1.5 mL / min, the temperature was 40 ℃, the stirring speed was 1000 rpm, and the reaction time was 40 min.

[0074] (11) The impregnated sample was placed in a vacuum rotary dryer and dried at 80 °C for 2 h. Then, it was heated to 250 °C (N2 atmosphere) at 5 °C / min and held for 1 h. Then, it was heated to 400 °C (air atmosphere) and held for 4 h to obtain CuO@Ce-Co-O composite oxide.

[0075] (12) The CuO@Ce-Co-O composite oxide was placed in a high-frequency low-pressure plasma reaction system, and an O2 / Ar mixed gas (1:3) was introduced. The power was 100 W and the reaction was carried out for 20 min to remove surface carbon residue and introduce active oxygen sites. Then, it was treated by an in-situ electrospray ion beam surface reconstruction device to enhance the electronic coupling of CuO and Ce-Co phase interface and maximize the catalytic activity, so as to obtain the Ce-doped Co-MOF derived CuO composite oxide catalyst, which is denoted as CuO@Ce1Co9-O (rare earth waste).

[0076] Example 2

[0077] Unlike Example 1, in step (6) of this example, the molar ratio of solution A to solution B is controlled to Ce:Co:ligand = 0.2:0.8:10, and the final catalyst is denoted as CuO@Ce2Co8-O (rare earth waste residue).

[0078] Comparative Example 1

[0079] Unlike Example 1, in step (6) of this comparative example, the molar ratio of solution A to solution B is controlled to Ce:Co:ligand = 0:1:10, and the final catalyst is denoted as CuO@Ce0Co. 10 -O (rare earth waste residue).

[0080] Comparative Example 2

[0081] Unlike Example 1, in step (6) of this comparative example, the molar ratio of solution A to solution B is controlled as Ce:Co:ligand = 0.3:0.7:10, and the final catalyst is denoted as CuO@Ce3Co7-O (rare earth waste residue).

[0082] Comparison 3

[0083] Unlike Example 1, in this comparative step (6), the molar ratio of solution A to solution B is controlled to Ce: Co: ligand = 0.4:0.6:10, and the final catalyst is denoted as CuO@Ce4Co6-O (rare earth waste residue).

[0084] Comparative Example 4

[0085] Unlike Example 2, this comparative example does not include step (10) (i.e., no CuO is loaded), and the final catalyst is denoted as Ce2Co8-O (rare earth waste).

[0086] Comparative Example 5

[0087] Unlike Example 2, this comparative example does not include steps (1)-(5). The cerium source and cobalt source in step (6) are commercially available pure cerium nitrate and commercially available pure cobalt nitrate. The catalyst obtained is denoted as CuO@Ce2Co8-O (pure reagent process).

[0088] Comparative Example 6

[0089] Unlike Comparative Example 5, this comparative example does not include (10) (i.e., no CuO is supported), and the final catalyst obtained is denoted as Ce2Co8-O (pure reagent process).

[0090] Test Example 1

[0091] To evaluate the catalytic performance of the catalyst samples in each embodiment and comparative example, CO catalytic reaction experiments were conducted in a fixed-bed reactor with a diameter of 10 mm. To ensure experimental safety, the experiments were conducted in a fume hood. Before testing, the airtightness and integrity of the flue gas analyzer, tubular reactor, and gas connection were checked. The catalyst was uniformly loaded onto a quartz wool support layer and placed in the isothermal zone of the fixed-bed reactor. The feed gas contained 4000 ppm CO, 20 vol% O2, and 78 vol% N2, with a gas flow rate of 1 L / min. A programmed temperature increase (5 °C / min) was then established, and the CO concentration changes at different temperatures were continuously monitored and recorded using a German Testo 350 flue gas analyzer until the CO conversion rate reached over 90%. The catalyst activity can be expressed as CO conversion efficiency, and the results are shown below. Figure 2As shown. After the reaction is complete, shut off the gas source and analyzer in sequence. After the system has cooled and residual gas has been purged, disassemble the device, clean the reaction tubes, and dispose of the waste catalyst according to regulations.

[0092] from Figure 2 It can be seen that the Ce-doped Co-MOF-derived CuO composite oxide catalyst of the present invention can achieve a CO conversion rate of over 90% at a lower temperature, and the temperature achieved first decreases and then significantly increases with increasing Ce doping amount. Furthermore, the temperature required for the CuO@Ce2Co8-O (pure reagent process) catalyst of Comparative Example 5 to achieve a CO conversion rate of over 90% is higher than that required for the CuO@Ce2Co8-O (rare earth waste residue) catalyst of Example 2 to achieve a CO conversion rate of over 90%. The present invention can reduce the temperature required for the catalyst to achieve a CO conversion rate of over 90%. Moreover, the CuO@Ce2Co8-O (rare earth waste residue) catalyst of Example 2 of the present invention, compared with the undoped Ce CuO@Ce0Co catalyst of Comparative Example 1, achieves a higher CO conversion rate. 10 The Ce-O (rare earth waste residue) catalyst reduces the temperature required to achieve a CO conversion rate of over 90% by 62°C. Compared to the unsupported CuO comparative catalyst 4Ce2Co8-O (rare earth waste residue), the temperature required to achieve a CO conversion rate of over 90% is reduced by more than 200°C, representing a significant temperature reduction. Furthermore, the Ce-doped Co-MOF-derived CuO composite oxide catalyst described in this invention retains over 95% of its activity after multiple cycles, demonstrating excellent stability and resistance to deactivation. The Ce and Co raw materials prepared using the rare earth waste residue process contain trace amounts of other rare earth elements, which promote the generation of oxygen vacancies on the catalyst support, thereby improving the overall performance of the catalyst.

[0093] Test Example 2

[0094] To evaluate the anti-interference performance of the catalyst samples in each embodiment and comparative example, a high-sulfur, high-humidity catalytic reaction experiment was conducted in a fixed-bed reactor with a diameter of 10 mm. The feed gas contained 4000 ppm CO, 500 ppm SO2, 10 vol% H2O, 20 vol% O2, and 70 vol% N2, with a gas flow rate of 1 L / min. The reactor temperature was then set to 300 °C, and the CO concentration was continuously monitored and recorded over time using a German Testo 350 flue gas analyzer until the CO conversion deactivation rate dropped below 10%. The comparison results between CuO-loaded and unloaded CuO are shown below. Figure 3 As shown. After the reaction is complete, shut off the gas source and analyzer in sequence. After the system has cooled and residual gas has been purged, disassemble the device, clean the reaction tubes, and dispose of the waste catalyst according to regulations.

[0095] from Figure 3It can be seen that in a high-sulfur and high-humidity atmosphere, the catalyst gradually deactivates over time. The time to reach 50% conversion (T50) is used to evaluate the catalyst's anti-interference ability. The T50 values ​​for Ce2Co8-O (rare earth waste residue) without CuO support and Ce2Co8-O (pure reagent process) are 62 minutes and 39 minutes, respectively. However, the anti-sulfur effects of CuO@Ce2Co8-O (rare earth waste residue) and CuO@Ce2Co8-O (pure reagent process) with CuO support have T50 values ​​of 134 minutes and 108 minutes, respectively. A significant difference in anti-interference effects between CuO-supported and unsupported catalysts is observed. This is attributed to the interfacial synergy between CuO and the Ce-Co support, which effectively inhibits sulfide formation, thereby achieving a level of anti-sulfur poisoning ability that existing catalytic systems have not yet achieved.

[0096] In addition, through Figure 4 Comparing the hydrophobic angles of CuO@Ce2Co8-O (rare earth waste residue) without CuO support, the hydrophobic angle of CuO@Ce2Co8-O (rare earth waste residue) was found to be 90.45°, significantly larger than the 66.92° of the unsupported CuO. Therefore, the introduction of CuO not only forms a high-entropy composite oxide structure on the Ce-Co-O matrix, leading to a decrease in surface energy and weakened polarity, but also enhances the stability of the gas-solid interface through the generated multi-scale rough surface. These structural factors collectively endow the catalyst with higher hydrophobicity, enabling it to effectively suppress the competitive adsorption of water molecules on active sites under high humidity or water-containing atmospheres, thereby significantly extending the stable operating time and resistance to moisture deactivation of the CuO@Ce2Co8-O catalyst.

[0097] Test Example 3

[0098] The effect of Ce doping concentration on the structure of CuO@Co3O4 catalyst was analyzed by Raman spectroscopy, and the results are as follows: Figure 5 As shown. From Figure 5 It can be seen that the undoped Ce sample at 610 cm⁻¹ -1 A distinct oxygen vacancy defect peak appears at this location, while the characteristic peaks of Co3O4 (520 and 690 cm⁻¹) are present. -1 The concentration of CuO significantly decreased, indicating that the introduction of CuO led to the reconstruction of the support surface structure. With increasing Ce doping concentration (Ce:Co ratio from 1:9 to 4:6), the 465 cm⁻¹ structure... -1 The intensity of the characteristic CeO2 peak at 610 cm⁻¹ continuously increases, indicating that the CeO2 phase gradually forms a complete crystalline phase from a highly dispersed state. Particularly noteworthy is the peak intensity at 610 cm⁻¹. -1 The defect peak intensity at the point exhibits a trend of first increasing and then decreasing, reaching its maximum value when Ce:Co = 8:2. This phenomenon stems from the fact that appropriate Ce doping can pass through Ce... 3+ / Ce 4+ Redox reactions effectively promote the formation of oxygen vacancies, while excessive doping of the CeO2 phase can actually reduce the surface oxygen defect density.

[0099] Combination Figure 2 The catalytic activity test results show that the CO oxidation activity exhibits a typical "volcano-shaped" curve with varying Ce content, reaching a peak at Ce:Co = 8:2. This phenomenon is highly consistent with the Raman analysis results, indicating that the catalyst performance mainly depends on its surface structure characteristics. When Ce:Co = 8:2, the catalyst achieves an optimal balance between the number and quality of active sites: sufficient oxygen vacancies ensure excellent redox capabilities, while a moderate Ce content prevents excessive coverage of active sites.

[0100] Test Example 4

[0101] To investigate the regulatory effect of Ce doping on the chemical states and electronic structure of elements on the surface of CuO@Co3O4 catalysts, XPS spectra of a series of samples were collected, and peak fitting and quantitative analysis were performed on the Co 2p and Ce 3d spectra. The results are as follows: Figure 6 As shown. From Figure 6 As can be seen, detailed analysis of the Co 2p spectrum reveals the valence state distribution of Co. In the undoped sample, Co... 2+ / (Co 2+ +Co 3+ The proportion was only 28.25%, and its Co 2p 3 / 2 The main peak is located around 780 eV, accompanied by strong satellite peaks, which is Co in Co3O4. 2+ With Co 3+ Coexistence characteristics. With Ce doping, Co 2p 3 / 2 The main peak binding energy systematically shifts negatively by approximately 0.4 eV, and in the CuO@Ce2Co8-O sample, Co... 2+ The proportion increased sharply to 78.64%. This clearly shows that the introduction of Ce donated electrons to the Co-O bond, causing some Co to... 3+ Reduced to Co 2+ (Co) 3+ +e - →Co 2+ This conclusion is strongly supported by the Ce 3d spectrum.

[0102] Test Example 5

[0103] The microstructure of the catalysts in each embodiment was observed, and the results are as follows: Figure 7 As shown. From Figure 7 (a)- Figure 7(b) It can be seen that the uncalcined Co8Ce2-MOF sample exhibits uniformly dispersed micron-sized polyhedral particles. These particles are evenly distributed without significant agglomeration, indicating good dispersibility and contributing to the provision of more active sites during catalysis. The particles have smooth surfaces and regular morphologies, exhibiting typical polyhedral characteristics. This structure may provide more exposed surface areas, thereby enhancing the contact probability between the catalyst and reactants. The particle size is mainly concentrated in the range of 1–5 μm, a size distribution that balances the catalyst's mechanical stability and specific surface area.

[0104] from Figure 7 (c)- Figure 7 (d) It can be seen that the morphology of the Co8Ce2-O sample changed significantly after high-temperature heat treatment. Large-sized porous spherical structures (approximately 10 μm in diameter) appeared in the sample. The originally smooth particle surface was reconstructed under high temperature, becoming rough and porous. This porous structure helps to increase the specific surface area and gas diffusion capacity of the material, thereby significantly improving the catalytic reaction efficiency. In addition, uniformly distributed particles of tens of nanometers in size can be observed on the surface of these large particles. These nanoparticles likely originate from the decomposition of organic components during high-temperature pyrolysis, thus forming a micro-nano hierarchical composite structure, further enhancing the surface activity of the catalyst.

[0105] from Figure 7 (e)- Figure 7 (i) It can be seen that in systems with different cobalt-cerium ratios (10:0, 9:1, 8:2, 7:3, 6:4), as the cerium doping amount increases, the final CuO@Co x Ce 1-x The overall morphology of the -O catalyst remained largely unchanged, maintaining a stable micro-nano hierarchical composite structure. This indicates that Ce incorporation does not disrupt the original structural framework of the catalyst and has no negative impact on morphological stability. Although the macroscopic morphology remains essentially unchanged, the chemical effect of Ce cannot be ignored. Its unique redox properties may modulate the electronic structure of the catalyst at the molecular level, thereby enhancing its reactivity.

[0106] In summary, this invention utilizes rare earth tailings and cobalt slag as raw materials to prepare catalysts, achieving resource regeneration and environmental friendliness. The continuous flow micro-premixed reaction combined with ultrasonic-microwave hydrothermal synergy ensures uniform crystal nucleation. High dispersion loading of CuO is achieved through multi-atmosphere segmented calcination and atomized impregnation-step calcination. The resulting catalyst is rich in oxygen vacancies, exhibits strong interfacial electron synergy, and demonstrates excellent low-temperature activity and stability. The preparation method allows for continuous control and is suitable for industrial-scale production. Compared with existing technologies, this invention represents a significant advancement.

[0107] The above description is merely a representative embodiment of the present invention and is not intended to limit the present invention in any way. Any embodiment made by those skilled in the art without departing from the scope of the present invention and utilizing the disclosed technical content is an equivalent embodiment of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a Ce-doped Co-MOF-derived CuO composite oxide catalyst, characterized in that, Includes the following steps: S1: Obtain rare earth waste containing Ce and Co elements, and perform cerium source and cobalt source extraction treatment on the rare earth waste to obtain cerium salt solution and cobalt salt solution. S2: The cerium salt solution and the cobalt salt solution are mixed with organic ligands to form Ce-Co-MOF crystals through a self-assembly reaction. After the reaction is completed, the mixture is centrifuged, washed, and dried to obtain the Ce-Co-MOF precursor. When mixing, the molar ratio of the cerium salt solution, cobalt salt solution and organic ligand is x:1-x:10, where 0 < x < 0.3; S3: The Ce-Co-MOF precursor is calcined and annealed to obtain a Ce-Co-O porous composite oxide support; S4: Prepare a copper salt solution and impregnate the Ce-Co-O porous composite oxide support with the copper salt solution. Then, dry and calcine the impregnated sample to obtain CuO@Ce-Co-O composite oxide. S5: Perform surface plasma activation treatment on the CuO@Ce-Co-O composite oxide to obtain the Ce-doped Co-MOF-derived CuO composite oxide catalyst.

2. The method for preparing the Ce-doped Co-MOF-derived CuO composite oxide catalyst according to claim 1, characterized in that, Step S1, the extraction of cerium and cobalt sources from the rare earth waste residue, specifically includes the following sub-steps: S11: The rare earth waste residue is coarsely ground and homogenized to obtain a powder sample; S12: The powder sample is subjected to acid leaching treatment with nitric acid solution, and the leaching solution is obtained by filtration. S13: Add oxalic acid solution to the first acid leaching solution and adjust the pH of the system to 1-2 so that rare earth ions react with oxalate ions to form insoluble rare earth oxalate precipitate. Centrifuge and wash to obtain precipitate one and acid leaching solution two. S14: The precipitate is calcined to obtain a mixed oxide containing Ce, and then the mixed oxide is dissolved in acid to prepare a salt solution containing Ce. The salt solution is extracted and the extracted phase is back-extracted to obtain the cerium salt solution. S15: Adjust the pH of the second acid leaching solution to 7-9 to selectively precipitate cobalt ions in the form of hydroxides. Centrifuge, wash, and dry to obtain precipitate two. Dissolve precipitate two in acid to obtain the cobalt salt solution.

3. The method for preparing the Ce-doped Co-MOF-derived CuO composite oxide catalyst according to claim 2, characterized in that, In step S15, when adjusting the pH of the second acid leaching solution, the adjusting agent used is any one of ammonia, urea, ammonium carbonate, ammonium bicarbonate, hexamethylenetetramine, and hydroxylamine.

4. The method for preparing the Ce-doped Co-MOF-derived CuO composite oxide catalyst according to claim 1, characterized in that, In step S2, the self-assembly reaction is carried out in an ultrasonic-microwave synergistic reactor, with an ultrasonic frequency of 30-50 kHz, a microwave power of 500-700 W, a temperature of 110-130 ℃, and a time of 10-12 h.

5. The method for preparing the Ce-doped Co-MOF-derived CuO composite oxide catalyst according to claim 1, characterized in that, In step S3, during calcination, the temperature is first raised to 300-350℃ in nitrogen at a rate of 2-3℃ / min and held for 2-2.5 h, and then raised to 450-500℃ in a 5% O2 / Ar mixed atmosphere at a rate of 3-5℃ / min and held for 3-3.5 h; during annealing, the annealing is carried out in an air atmosphere for 30-40 min.

6. The method for preparing the Ce-doped Co-MOF-derived CuO composite oxide catalyst according to claim 1, characterized in that, In step S4, the copper salt solution is a copper nitrate solution, and the impregnation is carried out using an atomized equal-volume impregnation method.

7. The method for preparing the Ce-doped Co-MOF-derived CuO composite oxide catalyst according to claim 1, characterized in that, In step S4, during calcination, the temperature is first raised to 200-300 ℃ in nitrogen at a rate of 4-6 ℃ / min and held for 1-2 h, and then raised to 400-500 ℃ in air and held for 3-4 h.

8. The method for preparing the Ce-doped Co-MOF-derived CuO composite oxide catalyst according to any one of claims 1-7, characterized in that, In step S5, during the surface plasma activation treatment, the surface carbon residue is first removed and active oxygen sites are introduced in the high-frequency low-pressure plasma reaction system. Then, the surface is treated by the in-situ electrospray ion beam surface reconstruction device to enhance the electronic coupling of the CuO and Ce-Co phase interface and maximize the catalytic activity.

9. A Ce-doped Co-MOF-derived CuO composite oxide catalyst, characterized in that, It was prepared using the method described in any one of claims 1-8 for the preparation of Ce-doped Co-MOF-derived CuO composite oxide catalyst.

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