A two-dimensional flower-like Cu 0.5 Co 2.5 O4 spinel, preparation method and application thereof

Abstract

The application provides a two-dimensional flower-shaped Cu 0.5 Co 2.5 O4 spinel, a preparation method and application thereof, and the method uses Co(NO3)2.6H2O and Cu(NO3)2.3H2O as raw materials, isopropanol and glycerol as solvents, and NaBH4 as a reducing agent, and obtains two-dimensional flower-shaped Cu 0.5 Co 2.5 O4 spinel through a combination of hydrothermal treatment, pyrolysis and reduction. 0.5 Co 2.5 The flower-shaped Cu 3+ Co 2+ O4 spinel prepared by the application has high crystallinity and high purity, and has good reproducibility; the synergistic effect between Co and Cu can significantly improve the ratio of Co / Co, and a large number of oxygen vacancies are generated, so that more active centers are shown; the content of oxygen vacancies is further improved after reduction of NaBH4; the rich oxygen vacancies are beneficial to generation and migration of lattice oxygen, so that the low-temperature thermal catalytic oxidation performance of toluene of the catalyst is improved, and the catalyst is a very promising toluene oxidation catalyst; by adjusting the Cu doping amount, the specific surface area and pore structure of the spinel can be effectively improved, so that more active sites are exposed.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a two-dimensional flower-like Cu 0.5 Co 2.5 O4 spinel, its preparation methods, and applications. Background Technology

[0002] Toluene is a major volatile organic compound (VOC), produced in large quantities from automobile exhaust and various industrial processes such as coal processing, oil refining, and natural gas processing. Currently, catalysts used for the catalytic combustion of toluene are mainly divided into noble metal catalysts and non-noble metal oxide catalysts. Noble metal catalysts (such as Pd, Pt, Au, etc.) possess excellent low-temperature activity, but their application is limited by drawbacks such as high cost, poor thermal stability, easy sintering, and susceptibility to poisoning. As alternatives to noble metal catalysts, non-noble metal oxides (such as Co3O4, CeO2, CuO, Cr2O3, etc.) and their composite oxides (such as spinel, perovskite, etc.) have been extensively studied in recent years. Among them, spinel catalysts, due to their atomically dispersed properties, maintain high atom utilization efficiency, high selectivity, and high stability while the synergistic effect between adjacent active sites can improve their catalytic activity, thus becoming a cutting-edge field in toluene catalysis. In the catalytic oxidation of toluene, the synergistic effect between the Co and Cu diatoms can effectively reduce the reaction temperature. Common methods for preparing spinel catalysts include impregnation, grinding and complexation, sol-gel, and hydrothermal methods. However, existing synthesis methods often result in products that are prone to aggregation, have low specific surface area, low purity, poor reproducibility, uneven dispersion, and are susceptible to the formation of CuO crystalline phases, leading to phase separation between Co3O4 and CuO, weak inter-component interactions, and consequently, poor catalytic combustion activity. Therefore, to improve the efficiency of thermocatalytic oxidation and decomposition of toluene, and to leverage the advantages of spinel nanomaterials, it is crucial to prepare two-dimensional flower-like copper-cobalt spinel catalysts with high specific surface area, abundant surface active sites, and excellent catalytic activity. Summary of the Invention

[0003] To address the technical problem that the abundance of active centers in nanoflower-like structures prepared by existing methods needs further improvement, this invention provides a two-dimensional flower-like Cu... 0.5 Co 2.5 O4 spinel, its preparation method, and its applications. The flower-like Cu obtained by this invention... 0.5 Co 2.5 O4 spinel has high crystallinity, high purity, and good reproducibility. The synergistic effect between Co and Cu can significantly improve the Co... 3+ / Co 2+ The higher proportion of active centers indicates a richer range of active sites, thereby improving the low-temperature thermocatalytic oxidation of toluene performance of the catalyst.

[0004] The first objective of this invention is to provide a flower-shaped Cu 0.5 Co 2.5 The preparation method of O4 spinel includes the following steps:

[0005] Step 1: Mix the cobalt source and copper source in a solvent to obtain a precursor solution;

[0006] Step two: The precursor solution obtained in step one is subjected to a hydrothermal reaction, and the solid phase is separated by solid-liquid separation. The obtained solid phase is then calcined to obtain Cu. 0.5 Co 2.5 O4 spinel precursor.

[0007] Step 3, apply the obtained Cu 0.5 Co 2.5 A reducing agent was added to the dispersion of O4 spinel precursor, and the mixture was ultrasonically treated to obtain the flower-like Cu. 0.5 Co 2.5 O4 spinel.

[0008] In one embodiment of the present invention, in step one, the cobalt source is selected from Co(NO3)2·6H2O and / or CoCl2·6H2O.

[0009] In one embodiment of the present invention, in step one, the copper source is selected from Cu(NO3)2·3H2O and / or CuCl2·2H2O.

[0010] In one embodiment of the present invention, in step one, the molar ratio of the cobalt source and the copper source is 10:1 to 1:5.

[0011] In one embodiment of the present invention, in step one, the solvent is a mixed solvent of isopropanol and glycerol, wherein the volume ratio of isopropanol to glycerol is 1:1 to 8:1.

[0012] In one embodiment of the present invention, step two includes at least one or more of the following conditions:

[0013] The conditions for the hydrothermal reaction are: reaction temperature of 130–200℃ and reaction time of 3–16 h.

[0014] It also includes washing and drying the solid phase, using alternating centrifugal washing with anhydrous ethanol, and the drying temperature is 60-80℃.

[0015] The calcination conditions are as follows: the temperature is increased at a rate of 1 to 5 °C / min, and calcined at 300 to 550 °C for 1 to 6 hours.

[0016] In one embodiment of the present invention, step three satisfies at least one or more of the following conditions:

[0017] The reducing agent is selected from one or more of NaBH4, sodium citrate, and ascorbic acid.

[0018] The two-dimensional spherical Cu 0.5 Co 2.5 The dispersant in the O4 spinel dispersion is water or ethanol;

[0019] The ultrasonic treatment time is 10–120 min;

[0020] It also includes solid-liquid separation of the ultrasonically treated reaction solution and collection of the solid phase, washing with water multiple times, and drying at 60-80℃ for 10-20 hours.

[0021] The second objective of this invention is to provide a flower-like Cu obtained by the aforementioned preparation method. 0.5 Co 2.5 O4 spinel.

[0022] A third object of the present invention is to provide the flower-shaped Cu 0.5 Co 2.5 Application of O4 spinel in the thermocatalytic oxidative decomposition of toluene.

[0023] In one embodiment of the present invention, at least one or more of the following conditions are satisfied:

[0024] The temperature in the thermocatalytic oxidation decomposition of toluene is 30–400°C;

[0025] The concentration of toluene is 300–1200 ppm;

[0026] The gas atmosphere for the thermocatalytic oxidation decomposition of toluene is as follows: the mass concentration of oxygen is 20%; the mass concentration of the inactive atmosphere is 80%, and the inactive gas in the inactive atmosphere is nitrogen and / or argon; the total flow rate of the gas in the gas atmosphere is controlled to be 40-80 mL / min, and the space velocity is 24000-48000 mL / (g·h).

[0027] The technical solution of the present invention has the following advantages over the prior art:

[0028] (I) Flower-shaped Cu obtained by the preparation method of the present invention 0.5 Co 2.5 O4 spinel has high crystallinity, and the synergistic effect between Co and Cu can significantly improve the Co content. 3+ / Co 2+ The ratio of oxygen vacancies is increased, and a large number of oxygen vacancies are generated, showing a richer active center. The oxygen vacancy content is further increased after NaBH4 reduction. Oxygen vacancies are conducive to the generation and migration of lattice oxygen, thereby improving the low-temperature thermocatalytic oxidation performance of toluene. It is a promising toluene oxidation catalyst.

[0029] (II) The nanoflowers prepared by the method of the present invention have a two-dimensional structure, and the Cu doping amount can be effectively improved by adjusting the Cu doping level. 0.5 Co 2.5 The specific surface area and pore structure of O4 spinel expose more active sites, and the high dispersion of active components avoids the interaction between nanoparticles and their aggregation covering the active sites.

[0030] (III) The preparation method of the present invention can prepare two-dimensional flower-like Cu with uniform size distribution, large surface area, abundant pores, and multi-component synergistic effect. 0.5 Co 2.5 O4 spinel is nano-Cu. 0.5 Co 2.5 O4 spinel offers broad application prospects in various fields.

[0031] (IV) The preparation method of this invention uses Co source and Cu source as raw materials, isopropanol and glycerol as solvents, and employs hydrothermal reaction, calcination and reduction reaction to prepare regular flower-like Cu. 0.5 Co 2.5 O4 spinel has a simple production process, short preparation time, low cost, high yield, strong repeatability, and can be produced on a large scale continuously.

[0032] (V) Compared with single-component Co3O4 and CuO catalysts, the flower-like Cu prepared in this invention... 0.5 Co 2.5 O4 spinel has a porous structure, exhibiting abundant active sites. Flower-like Cu 0.5 Co 2.5 O4 spinel toluene exhibits significantly better catalytic performance than single-component catalysts and demonstrates excellent low-temperature reducibility. Attached Figure Description

[0033] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0034] Figure 1 This is a two-dimensional flower-like Cu prepared in Example 1 of the present invention. 0.5 Co 2.5 X-ray diffraction (XRD) pattern of O4 spinel.

[0035] Figure 2 This is a two-dimensional flower-like Cu prepared in Example 1 of the present invention. 0.5 Co 2.5 Scanning electron microscope (SEM) image of O4 spinel.

[0036] Figure 3 This is a two-dimensional flower-like Cu prepared in Example 1 of the present invention. 0.5Co 2.5 Magnified SEM image of O4 spinel.

[0037] Figure 4 This is a SEM image of the two-dimensional flower-shaped CuCo2O4 spinel prepared in Example 2 of this invention.

[0038] Figure 5 This is a two-dimensional flower-like Cu prepared in Example 3 of the present invention. 0.375 Co 2.625 SEM image of O4 spinel.

[0039] Figure 6 This is a SEM image of the single-component Co3O4 prepared in Comparative Example 1 of this invention.

[0040] Figure 7 This is a SEM image of the single-component CuO prepared in Comparative Example 2 of this invention.

[0041] Figure 8 This is a two-dimensional flower-like Cu prepared in Example 1 of the present invention. 0.5 Co 2.5 Thermocatalytic toluene oxidation performance of O4 spinel, the single-component Co3O4 obtained in Comparative Example 1, and the CuO catalyst obtained in Comparative Example 2. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0043] Example 1:

[0044] This embodiment presents a two-dimensional flower-shaped Cu 0.5 Co 2.5 O4 spinel and its preparation method, the method comprising the following steps:

[0045] Step 1: Dissolve 0.0033 mol Co(NO3)2·6H2O and 0.0007 mol Cu(NO3)2·3H2O in a mixed solvent of 50 mL isopropanol and 14 mL glycerol, and stir for 30 min to obtain the precursor solution.

[0046] Step 2: The precursor solution was placed in a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene and allowed to stand at 170 °C for 10 h. After the hydrothermal reaction, the supernatant was discarded, and the lower precipitate was washed alternately by centrifugation with anhydrous ethanol, dried at 60 °C for 12 h, ground, and calcined in a tube furnace at 350 °C for 2 h (programmed temperature increase of 2 °C / min) to obtain Cu with a spinel structure. 0.5 Co 2.5 O4.

[0047] Step 3, add 40mg of Cu 0.5 Co 2.5 O4 was dispersed in 40 mL of deionized water, then 8 mg of NaBH4 was added, followed by ultrasonic treatment for 30 min. The mixture was then washed multiple times with deionized water and dried at 60 °C for 12 h to obtain flower-like Cu. 0.5 Co 2.5 O4 spinel. The obtained material was structurally characterized, and the results are shown in [the table below]. Figures 1-3 .

[0048] Depend on Figure 1 It can be seen that the product obtained is Cu. 0.5 Co 2.5 O4 spinel oxide.

[0049] Depend on Figure 2 As can be seen, the obtained product has a flower-like structure.

[0050] Depend on Figure 3 As can be seen, the magnified floral Cu 0.5 Co 2.5 The O4 spinel morphology diagram shows that the oxide surface is porous.

[0051] Example 2:

[0052] This embodiment provides a method for preparing two-dimensional flower-like CuCo2O4 spinel, which includes the following steps:

[0053] Step 1: Dissolve 0.0027 mol Co(NO3)2·6H2O and 0.0013 mol Cu(NO3)2·3H2O in a mixed solvent of 50 mL isopropanol and 14 mL glycerol, and stir for 30 min to obtain the precursor solution.

[0054] Step 2: The precursor solution was placed in a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene and allowed to stand at 170 °C for 10 h. After hydrothermal reaction, the supernatant was discarded, and the lower precipitate was washed with anhydrous ethanol by centrifugation, dried at 60 °C for 12 h, ground, and calcined in a tube furnace at 350 °C for 2 h (programmed temperature increase of 2 °C / min) to obtain CuCo2O4 with a spinel structure.

[0055] Step 3: 40 mg of CuCo₂O₄ was dispersed in 40 mL of deionized water, then 8 mg of NaBH₄ was added, followed by ultrasonic treatment for 30 min. The mixture was washed multiple times with deionized water and dried at 60 °C for 12 h to obtain flower-like CuCo₂O₄ spinel. The obtained material was characterized, and the results are shown in the figure. Figure 4 .Depend on Figure 4 As can be seen, the obtained product has a flower-like structure.

[0056] Example 3:

[0057] This embodiment presents a two-dimensional flower-shaped Cu 0.375 Co 2.625 A method for preparing O4 spinel, comprising the following steps:

[0058] Step 1: Dissolve 0.0035 mol Co(NO3)2·6H2O and 0.0005 mol Cu(NO3)2·3H2O in a mixed solvent of 50 mL isopropanol and 14 mL glycerol, and stir for 30 min to obtain the precursor solution.

[0059] Step 2: The precursor solution was placed in a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene and allowed to stand at 170 °C for 10 h. After the hydrothermal reaction, the supernatant was discarded, and the lower precipitate was washed with anhydrous ethanol by centrifugation, dried at 60 °C for 12 h, ground, and calcined in a tube furnace at 350 °C for 2 h (programmed temperature increase of 2 °C / min) to obtain Cu with a spinel structure. 0.375 Co 2.625 O4.

[0060] Step 3, add 40mg of Cu 0.375 Co 2.625 O4 was dispersed in 40 mL of deionized water, then 8 mg of NaBH4 was added, followed by ultrasonic treatment for 30 min. The mixture was then washed multiple times with deionized water and dried at 60 °C for 12 h to obtain flower-like Cu. 0.375 Co 2.625 O4 spinel. The obtained material was characterized, and the results are shown in [Figure number missing]. Figure 5 .Depend on Figure 5 As can be seen, the obtained product has a flower-like structure.

[0061] Comparative Example 1:

[0062] This comparative example provides a method for preparing Co3O4, which includes the following steps:

[0063] Step 1: Dissolve 0.004 mol Co(NO3)2·6H2O in a mixed solvent of 50 mL isopropanol and 14 mL glycerol, and stir for 30 min to obtain the precursor solution.

[0064] Step 2: The precursor solution was placed in a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene and allowed to stand at 170 °C for 8 h. After the hydrothermal reaction, the supernatant was discarded, and the lower precipitate was washed alternately by centrifugation with anhydrous ethanol, dried at 60 °C for 12 h, ground, and calcined in a tube furnace at 350 °C for 2 h (programmed temperature increase of 2 °C / min) to obtain Co3O4.

[0065] Step 3: 40 mg of Co3O4 was dispersed in 40 mL of deionized water, then 8 mg of NaBH4 was added, followed by ultrasonic treatment for 30 min. The mixture was washed multiple times with deionized water and dried at 60 °C for 12 h to obtain single-component Co3O4. The structure of the obtained material was characterized, and the results are shown in [Figure 1]. Figure 6 .Depend on Figure 6 As can be seen, the obtained material has a flower-like structure.

[0066] Comparative Example 2:

[0067] This comparative example presents a method for preparing two-dimensional flower-like CuO, which includes the following steps:

[0068] Step 1: Dissolve 0.004 mol Cu(NO3)2·3H2O in a mixed solvent of 50 mL isopropanol and 14 mL glycerol, and stir for 30 min to obtain the precursor solution.

[0069] Step 2: The precursor solution was placed in a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene and allowed to stand at 180 °C for 20 h. After the hydrothermal reaction, the supernatant was discarded, and the lower precipitate was washed alternately by centrifugation with anhydrous ethanol, dried at 60 °C for 12 h, ground, and calcined in a tube furnace at 350 °C for 2 h (programmed temperature increase of 2 °C / min) to obtain CuO.

[0070] Step 3: 40 mg of CuO was dispersed in 40 mL of deionized water, then 8 mg of NaBH4 was added, followed by ultrasonic treatment for 30 min. The mixture was washed multiple times with deionized water and dried at 60 °C for 12 h to obtain granular CuO spinel. The structure of the obtained material was characterized, and the results are shown in the figure. Figure 7 .Depend on Figure 7 As can be seen, the obtained material has a granular structure.

[0071] Application Example 1:

[0072] This application example illustrates the use of the catalyst obtained in the example for the thermocatalytic oxidative decomposition of toluene.

[0073] In this application example, the two-dimensional flower-shaped Cu 0.5 Co 2.5 The O4 spinel catalyst was prepared using the method described in Example 1; and the single-component Co3O4 catalyst obtained in Comparative Example 1 and the single-component CuO catalyst obtained in Comparative Example 2 were used as controls.

[0074] Specifically, 100 mg of catalyst was placed in a quartz tube reactor with a diameter of 10 mm. The reactant feed consisted of toluene at a mass concentration of 1000 ppm, a balance gas of 20% O2 and 80% N2, and the total gas flow rate was controlled at 60 mL / min. The space velocity was 36000 mL / (g·h), and the reaction temperature was 30–400 °C. Toluene was thermally catalytically oxidized and decomposed to produce CO2 and H2O. Experimental results are shown below. Figure 8 .

[0075] Depend on Figure 8 As can be seen, compared with single-component Co3O4 catalysts and single-component CuO catalysts, the flower-like Cu prepared by this invention... 0.5 Co 2.5 O4 spinel exhibits excellent catalytic oxidation performance of toluene due to its abundant specific surface area and oxygen vacancies.

[0076] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A flower-like Cu 0.5 Co 2.5 The application of O4 spinel in the thermocatalytic oxidative decomposition of toluene is characterized by... The flower-shaped Cu 0.5 Co 2.5 The preparation method of O4 spinel includes the following steps: Step 1: Mix the cobalt source and copper source in a solvent to obtain a precursor solution; Step two: The precursor solution obtained in step one is subjected to a hydrothermal reaction, and the solid phase is separated by solid-liquid separation. The obtained solid phase is then calcined to obtain Cu. 0.5 Co 2.5 O4 spinel precursor; Step 3, apply the obtained Cu 0.5 Co 2.5 A reducing agent was added to the dispersion of O4 spinel precursor, and the mixture was ultrasonically treated to obtain the flower-like Cu. 0.5 Co 2.5 O4 spinel; The reducing agent is selected from NaBH4; Step 1: The solvent is a mixture of isopropanol and glycerol, and the volume ratio of isopropanol to glycerol is 1:1 to 8:

1.

2. The application according to claim 1, characterized in that, Step 1: The cobalt source is selected from Co(NO3)2•6H2O and / or CoCl2•6H2O.

3. The application according to claim 1, characterized in that, Step 1: The copper source is selected from Cu(NO3)2•3H2O and / or CuCl2•2H2O.

4. The application according to claim 1, characterized in that, Step 1: The molar ratio of the cobalt source to the copper source is 10:1 to 1:

5.

5. The application according to claim 1, characterized in that, Step two includes at least one or more of the following conditions: The conditions for the hydrothermal reaction are: reaction temperature of 130–200℃ and reaction time of 3–16 h. It also includes washing and drying the solid phase, using alternating centrifugal washing with anhydrous ethanol, and the drying temperature is 60-80℃. The calcination conditions are as follows: the temperature is increased at a rate of 1~5℃ / min, and calcined at 300~550℃ for 1~6 hours.

6. The application according to claim 1, characterized in that, Step 3, at least one or more of the following conditions must be met: The flower-shaped Cu 0.5 Co 2.5 The dispersant in the O4 spinel dispersion is water and / or ethanol; The ultrasonic treatment time is 10-120 min; It also includes solid-liquid separation of the ultrasonically treated reaction solution and collection of the solid phase, washing with water multiple times, and drying at 60~80℃ for 10~20h.

7. The application according to claim 1, characterized in that, At least one or more of the following conditions must be met: The temperature in the thermocatalytic oxidation decomposition of toluene is 30~400℃; The mass concentration of toluene is 300~1200 ppm; The gas atmosphere for the thermocatalytic oxidation decomposition of toluene is as follows: the inactive gas in the inactive atmosphere is nitrogen and / or argon; the total flow rate of the gas in the controlled gas atmosphere is 40~80 mL / min, and the space velocity is 24000~48000 mL / (g•h).

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