Design synthesis of Co-based nano material and application of Co-based nano material in cyclohexene electrocatalytic oxidation

Abstract

The invention provides design and synthesis of a Co-based catalyst electrode material and electro-catalysis of the Co-based catalyst electrode material for ultra-high selective oxidation of cyclohexene into cyclohexenol. The preparation method comprises the following steps: mixing cobalt nitrate hexahydrate, hexadecyl trimethyl ammonium chloride and urea, reacting, and treating to obtain spherical Co3O4; the method comprises the following steps: treating spherical Co3O4 by taking sodium phosphite as a phosphorus source to obtain Co3O4-P; the preparation method comprises the following steps: carrying out reaction on cobalt nitrate hexahydrate, urea and thiourea to prepare Co3O4-S. And the three catalysts are respectively loaded on the carrier carbon paper sheets to form corresponding electrodes. The catalyst electrodes are used for electrocatalytic oxidation of cyclohexene to prepare cyclohexenol with ultrahigh selectivity, the selectivity is as high as 99%, the Faraday efficiency is as high as 89.6%, and the cycle stability is excellent. The cost of the Co-based catalyst is lower than that of precious metal, and the Co-based catalyst has good catalytic activity, ultrahigh selectivity and poisoning resistance and has good application prospects in the industrial field.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis technology, specifically relating to Co-based catalyst electrode materials, preparation methods, and their application in the catalytic oxidation of cyclohexene. Background Technology

[0002] Cyclohexene is a very important organic intermediate. In recent years, with the maturation of the selective hydrogenation process of benzene to cyclohexene, the downstream applications of cyclohexene have developed rapidly. The CH oxidation of alkenes can convert olefins into alcohols, aldehydes, carboxylic acids, and epoxides with higher added value. Among these, the selective oxidation of cyclohexene to prepare 2-cyclohexen-1-ol (cyclohexenol) has become a research hotspot. Cyclohexenol is an important raw material in pharmaceutical, pesticide, and materials research fields, and can be used as a raw material for the synthesis of terpenes, the Amaryllidaceae alkaloid snow lotusamine, dihydrocodeine ketone, and other drugs or intermediates. Therefore, research on the selective oxidation of cyclohexene to prepare cyclohexenol has received considerable attention in recent years. Currently, the industrial method for oxidizing cyclohexene to cyclohexenol usually involves catalytic oxidation under high temperature and high pressure, which suffers from high energy consumption, low efficiency, and difficulty in product separation. However, using renewable energy to drive the conversion of cyclohexene to cyclohexenol allows for the production of valuable products in a milder manner with lower energy consumption, thus leading to the widespread development of electrochemical synthesis.

[0003] In electrochemical oxidation, the most commonly used heterogeneous catalysts are noble metals and their alloys, such as Pt, Au, Pd, and Ru. However, their cost is very high. Therefore, research on non-noble metal compounds to replace noble metal catalysts is attracting increasing attention. Cobalt-based catalysts, in particular, are less expensive than noble metals such as platinum and palladium, making them more economical for industrial applications. Due to the unfilled d-orbitals, cobalt-based catalysts readily undergo electron transitions in their outermost shell, resulting in high activity, good electrochemical stability, and high electron conductivity. This effectively promotes electrocatalytic reactions, thus exhibiting redox properties. Based on the constituent elements, commonly used cobalt-based catalysts for electrocatalytic oxidation reactions can be classified into six categories: cobalt oxides, cobalt hydroxides, cobalt sulfides, cobalt phosphides, cobalt nitrides, and cobalt selenides. Furthermore, the electrocatalytic performance of catalysts can be improved through elemental doping, size and morphology control, and interface engineering design. Summary of the Invention

[0004] To address the aforementioned shortcomings, this invention provides a Co-based catalyst electrode, its preparation method, and its application in the catalytic oxidation of cyclohexene. The electrode incorporates three Co-based catalyst materials: Co3O4, Co3O4-P, and Co3O4-S. This invention designs and constructs catalytic electrodes supported on catalysts such as Co3O4, Co3O4-P, and Co3O4-S for the electrocatalytic conversion of sparingly soluble organic solutions, such as cyclohexene. Under electrocatalytic action, this electrode can rapidly and efficiently oxidize cyclohexene at the allyl group site to the important organic intermediate 2-cyclohexenol, exhibiting high efficiency and good selectivity.

[0005] This invention is achieved through the following technical solutions.

[0006] First, the present invention provides three Co-based catalyst electrodes, including a Co3O4 catalyst electrode, a Co3O4-P catalyst electrode, and a Co3O4-S catalyst electrode.

[0007] (1) Co3O4 catalyst electrode: This electrode comprises a carbon paper support and spherical Co3O4 particles supported on the support. The present invention also provides a method for preparing the above-mentioned Co3O4 catalyst electrode, the method comprising the following steps:

[0008] Cobalt nitrate hexahydrate, hexadecyltrimethylammonium chloride, and urea were mixed into a solution and placed in a high-pressure reactor for heating. After the reaction was completed, the mixture was cooled and centrifuged to obtain a precipitate. The precipitate was washed with water and 95% ethanol, dried in an oven, and then heated in a muffle furnace to obtain spherical Co3O4 catalyst.

[0009] (2) Co3O4-P catalyst electrode: This electrode comprises a carbon paper support and Co3O4-P supported on the support. The present invention also provides a method for preparing the above-mentioned Co3O4-P catalyst electrode, the method comprising the following steps:

[0010] The spherical Co3O4 prepared above was heated under a nitrogen atmosphere using sodium phosphite as the nitrogen source to finally obtain the Co3O4-P catalyst.

[0011] (3) Co3O4-S catalyst electrode: This electrode comprises a carbon paper support and Co3O4-S supported on the support. The present invention also provides a method for preparing the above-mentioned Co3O4-S catalyst electrode, the method comprising the following steps:

[0012] Cobalt nitrate hexahydrate, urea, and thiourea were prepared into a solution, heated in a polytetrafluoroethylene liner, and then cooled, washed, and dried to finally obtain the Co3O4-S catalyst.

[0013] Note: The mass ratio of cobalt nitrate hexahydrate, hexadecyltrimethylammonium chloride, and urea in step (1) is 4.37g:0.15g:3.60g. The three are dissolved in ethylene glycol in sequence. The mixture is kept at 180℃ for 12 hours in a high-pressure reactor, dried in an oven at 100℃ for 12 hours, and finally calcined in a muffle furnace at 400℃.

[0014] The mass ratio of the spherical Co3O4 and sodium phosphite mentioned in step (2) is 0.1g:1g. After mixing them evenly in a magnetic boat, the mixture is calcined at 300°C for 2 hours under a nitrogen atmosphere.

[0015] The mass ratio of cobalt nitrate hexahydrate, urea, and thiourea in step (3) is 0.873g:0.540g:0.228g. The three are dissolved in deionized water and kept at 180°C for 12 hours in a polytetrafluoroethylene liner.

[0016] This invention also provides the application of the above three catalyst electrodes in the electrocatalytic oxidation of cyclohexene to cyclohexenol. The electrolytic oxidation of cyclohexene using these three catalyst electrodes exhibits excellent selectivity, high yield of cyclohexenol, and good cyclic stability. This provides a catalyst construction strategy for effectively improving the performance of nucleophiles in electrocatalytic oxidation, and has excellent application prospects. The resulting cyclohexenol is also an important intermediate in organic synthesis, offering significant economic benefits.

[0017] The present invention has the following positive and beneficial effects

[0018] This invention utilizes a simple operation to construct three cobalt-based catalyst materials. Compared to precious metals such as platinum and palladium, cobalt-based catalysts are less expensive, making them more economical for industrial applications. Furthermore, cobalt-based catalysts not only possess excellent catalytic activity and high selectivity, but also exhibit some resistance to poisoning by compounds such as sulfur and phosphorus, maintaining good catalytic activity in reaction systems containing small amounts of impurities. The economic efficiency, high efficiency, and high selectivity of cobalt-based catalysts make them promising for industrial applications.

[0019] The catalyst electrode prepared by this invention exhibits excellent reaction rate and selectivity in the nucleophilic oxidation reaction (COR). It can quickly reach equilibrium during the process, i.e., form a rapid dynamic equilibrium, avoiding the competitive reaction between COR and OER on the surface of the cobalt-based catalyst, thus breaking through the bottleneck of cobalt-based catalyst application in COR. Attached Figure Description

[0020] Figure 1 The spherical Co3O4 catalytic material prepared in Example 1 is characterized by scanning electron microscopy (SEM).

[0021] Figure 2The transmission electron microscope (TEM) characterization of the spherical Co3O4 catalytic material in Example 1 is shown.

[0022] Figure 3 The energy dispersive X-ray spectroscopy (EDS) characterization of the spherical Co3O4 catalytic material in Example 1 is shown.

[0023] Figure 4 The X-ray diffraction (XRD) characterization of the spherical Co3O4 catalytic material in Example 1 is shown.

[0024] Figure 5 The image shows the scanning electron microscope (SEM) characterization of the Co3O4-P catalytic material in Example 2.

[0025] Figure 6 Transmission electron microscopy (TEM) characterization of the Co3O4-P catalytic material in Example 2.

[0026] Figure 7 The energy dispersive X-ray spectroscopy (EDS) characterization of the Co3O4-P catalytic material in Example 1 is shown.

[0027] Figure 8 These are the linear voltammetric scan (LSV) curves of the spherical Co3O4, Co3O4-P, and Co3O4-S catalytic materials in Examples 1, 2, and 3.

[0028] Figure 9 These are the Tafel slope curves of the spherical Co3O4, Co3O4-P, and Co3O4-S catalytic materials in Examples 1, 2, and 3.

[0029] Figure 10 This is a graph showing the yield and selectivity of cyclohexenol from the Co3O4-P catalyst in Example 2 at different voltages.

[0030] Figure 11 This is a Faraday efficiency diagram of Co3O4-P under different voltages in Example 2.

[0031] Figure 12 Long-term stability voltammetric curves of the spherical Co3O4, Co3O4-P, and Co3O4-S catalytic materials in KOH electrolyte in Examples 1, 2, and 3. Detailed Implementation

[0032] The present invention will now be described in more detail through specific embodiments to facilitate understanding of the technical solution of the present invention, but this is not intended to limit the scope of protection of the present invention.

[0033] Unless otherwise specified, all reagents used in the experimental section of this invention are reagents known to those skilled in the art.

[0034] Example 1

[0035] A method for preparing spherical Co3O4 catalyst materials, comprising the following steps:

[0036] 4.37 g of Co(NO3)·6H2O was dissolved in 30 mL of ethylene glycol and stirred for 30 min. Then, 0.15 g of hexadecyltrimethylammonium chloride and 3.60 g of urea were added to the solution sequentially, and stirring was continued for 2 h. The resulting solution was transferred to a 50 mL high-pressure reactor and kept at 180 °C for 12 h. After the reaction was completed, the reactor was cooled to room temperature and centrifuged to obtain the precipitate. The precipitate was washed three times alternately with water and 95% alcohol, dried in an oven at 100 °C for 12 h, and finally calcined in a muffle furnace at 400 °C with a heating rate of 2 °C / min to obtain spherical Co3O4 catalyst.

[0037] Example 2

[0038] A method for preparing Co3O4-P catalyst material, comprising the following steps:

[0039] 100 mg of spherical cobalt oxide was placed in a small magnetic boat, and 1 g of sodium hypophosphite was used as the phosphorus source. The mixture was heated to 300 °C for 2 h under a nitrogen atmosphere at a rate of 2 °C / min to obtain the Co3O4-P catalyst.

[0040] Example 3

[0041] A method for preparing Co3O4-S catalyst material, comprising the following steps:

[0042] 0.873 g Co(NO3)2·6H2O (3 mmol, 0.1 mol / L), 0.54 g CO(NH2)2 (9 mmol, 0.3 mol / L), and 0.228 g thiourea (3 mmol, 0.1 mol / L) were dissolved in 30 mL of deionized water. The solution was kept in a 50 mL polytetrafluoroethylene-lined container at 180 °C for 12 h. After washing and drying at 60 °C, the Co3O4-S catalyst was finally obtained.

[0043] The performance of the catalysts prepared in the above examples was tested.

[0044] The obtained material was characterized, and the results are shown in [the table below]. Figure 1-12 .

[0045] Depend on Figure 1 As can be seen from the scanning electron microscope (SEM) characterization image of the spherical Co3O4 catalytic material prepared in Example 1, the prepared Co3O4 has a good spherical shape.

[0046] Depend on Figure 2As can be seen, the transmission electron microscope (TEM) characterization image of the spherical Co3O4 catalytic material prepared in Example 1 is shown.

[0047] Depend on Figure 3 As can be seen, the energy dispersive X-ray spectroscopy (EDS) characterization diagram of the spherical Co3O4 catalytic material prepared in Example 1 is shown.

[0048] Depend on Figure 4 As can be seen, the X-ray diffraction (XRD) characterization of the spherical Co3O4 catalytic material prepared in Example 1 shows that the blue diffraction peaks in the figure correspond to the brown vertical lines on the standard PDF card below, indicating the presence of spherical Co3O4 in the sample. At the same time, the sharp peaks in the figure indicate good crystallinity and regular atomic arrangement. Furthermore, no impurity peaks are shown in the figure, indicating that the sample has high purity.

[0049] Depend on Figure 5 As can be seen, the scanning electron microscope (SEM) characterization image of the Co3O4-P catalytic material prepared in Example 2 is shown.

[0050] Depend on Figure 6 As can be seen, the transmission electron microscope (TEM) characterization image of the Co3O4-P catalytic material prepared in Example 2 is shown.

[0051] Depend on Figure 7 As can be seen, the energy dispersive X-ray spectroscopy (EDS) characterization diagram of the Co3O4-P catalytic material prepared in Example 2 is shown.

[0052] Depend on Figure 8 As can be seen from the linear voltammetric scan (LSV) curves of the spherical Co3O4, Co3O4-P, and Co3O4-S catalysts prepared in Examples 1, 2, and 3 in KOH solution with and without cyclohexene. The graph shows that Co3O4-P exhibits the highest current density at the same potential regardless of the presence or absence of cyclohexene, followed by spherical Co3O4, and finally Co3O4-S.

[0053] Depend on Figure 9 It can be seen that the spherical Co3O4, Co3O4-P, and Co3O4-S catalytic materials prepared in Examples 1, 2, and 3 are effective at 1.0 mol / L. -1 The Tafel slope curve of Co3O4-P in KOH electrolyte shows that the Tafel slope is 12 mVdec. -1， The smallest slope indicates that it has the best dynamic performance.

[0054] Depend on Figure 10 It can be seen that the Co3O4-P catalyst prepared in Example 2 has the highest yield and selectivity at 1.5V.

[0055] Depend on Figure 11 It can be seen that the Co3O4-P catalytic material prepared in Example 2 has the highest Faraday efficiency at 1.5V.

[0056] Depend on Figure 12 As can be seen, Examples 1, 2, and 3 at 1.0 mol L -1 The long-term stability voltammetric curves in KOH electrolyte showed no current decay during the 20-hour test, indicating that these materials have excellent long-term stability and ideal practical prospects.

Claims

1. Design and synthesis of Co-based nanomaterials and their application in the electrocatalytic oxidation of cyclohexene, specifically including the preparation methods of three Co-based catalyst materials: spherical Co3O4, Co3O4-P, and Co3O4-S.

2. The synthesis method of the spherical Co3O4 catalyst according to claim 1 is as follows: 4.37 g of Co(NO3)·6H2O is dissolved in 30 mL of ethylene glycol and stirred for 30 min. Then, 0.15 g of hexadecyltrimethylammonium chloride and 3.60 g of urea are added to the solution sequentially, and stirring is continued for 2 h. The resulting solution is transferred to a 50 mL high-pressure reactor and kept at 180 °C for 12 h. After the reaction is completed, the reactor is cooled to room temperature and centrifuged to obtain the precipitate. The precipitate is washed three times alternately with water and 95% alcohol, dried in an oven at 100 °C for 12 h, and finally calcined in a muffle furnace at 400 °C with a heating rate of 2 °C / min to obtain the spherical Co3O4 catalyst.

3. The synthesis method of the Co3O4-P catalyst according to claim 1 is as follows: Take the spherical Co3O4 prepared according to claim 2 and put it into a small magnetic boat. Take a certain amount of sodium hypophosphite as a phosphorus source and heat it to 300°C for 2 hours at a rate of 2°C / min under a nitrogen atmosphere to finally obtain the Co3O4-P catalyst.

4. The synthesis method of the Co3O4-S catalyst according to claim 1 is as follows: 0.873 g Co(NO3)2·6H2O (3 mmol, 0.1 mol / L), 0.54 g CO(NH2)2 (9 mmol, 0.3 mol / L), and 0.228 g thiourea (3 mmol, 0.1 mol / L) are dissolved in 30 mL deionized water. The solution is kept at 180 °C for 12 h in a 50 mL polytetrafluoroethylene liner. After washing and drying at 60 °C, the Co3O4-S catalyst is finally obtained.

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