A method for preparing cyclohexanone by catalytic hydrogenation of chlorophenol based on a carbon nanotube confined palladium electrode

Abstract

The application discloses a method for preparing cyclohexanone by catalytic hydrogenation of chlorophenol based on a carbon nanotube confined palladium electrode, which comprises the following steps: firstly, preparing a Pd-in-CNTs catalyst through a dipping calcination method; then, constructing a three-dimensional electrocatalytic reaction system, wherein a platinum sheet is used as an anode, a graphite plate is used as a cathode, Ag / AgCl is used as a reference electrode, a cation exchange membrane is used to divide an anode chamber and a cathode chamber, and the Pd-in-CNTs is filled in the cathode chamber as a particle electrode; under a constant potential condition, chlorophenol pollutants in the cathode chamber are subjected to step-by-step hydrogenation dechlorination and synergistic cyclohydrogenation reactions on the surface of the Pd-in-CNTs, and are directionally converted into a high-value-added chemical product, cyclohexanone; the application realizes a 95% to 99% conversion rate of chlorophenol organic matters, and exhibits excellent catalytic activity and product selectivity; the method innovatively combines pollutant degradation and resource recovery, and has the advantages of mild reaction conditions, environmental friendliness, controllable selectivity and the like, and provides a new technical approach for resource treatment of industrial chlorinated organic wastewater.

Description

Technical Field

[0001] This invention relates to the field of cyclohexanone preparation technology, and in particular to a method for preparing cyclohexanone from chlorophenols by hydrogenation catalysis using a carbon nanotube confined palladium electrode. Background Technology

[0002] Chlorophenols, organic compounds, possess excellent lipophilic and solvent properties, and are commonly used as solvents and mediators in industrial production, widely applied in pesticide synthesis, plastics processing, and petrochemical production. However, due to their high water solubility, high bioaccumulation, and potential carcinogenic, teratogenic, and mutagenic effects, the large quantities of chlorophenol wastewater generated during industrial production (chlorophenol concentrations typically ranging from several to hundreds of mg / L, with annual discharges reaching hundreds of thousands of tons) pose a serious threat to ecological security if discharged directly without advanced treatment. The key step in treating chlorophenol pollutants lies in the effective breaking of the C-Cl bond. However, the strong electron-withdrawing effect of the chlorine atom reduces the electron cloud density of the phenolic ring, giving it strong antioxidant properties. Traditional advanced oxidation processes (AOPs) often suffer from bottlenecks such as high reaction energy barriers and low efficiency. In contrast, electrocatalytic hydrogenation (ECH) technology utilizes a catalyst to electrolyze H₂O or H₂O. + The generated active hydrogen species ( This method enables dechlorination and cyclohexanone hydrogenation processes, offering advantages such as mild conditions, environmental friendliness, and the ability to transform pollutants into high-value-added chemicals. For example, hydrogenating chlorophenols to cyclohexanone (an important industrial raw material) not only significantly reduces product toxicity but also enables the resource utilization of waste.

[0003] Pd-based catalysts are due to their production and storage Capability is currently the focus of ECH technology research. However, most existing technologies stop at the dechlorination of chlorophenol to phenol (a toxic intermediate product), and it is difficult to further cyclohydrogenate it to cyclohexanone. The core bottleneck is: (1) Mass transfer is hindered: chlorophenol (p K a > 8) and the intermediate product phenol (p K (a = 9.95) It mainly exists in the electrolyte as a neutral molecule or phenol anion, and it is difficult to approach the inner Helmholtz plane of the electrode surface; (2) Site deficiency: Existing Pd-based catalysts lack sufficient electron-deficient Pd sites to effectively activate the phenol ring; (3) Low utilization: Electrocatalytic hydrogenation to prepare cyclohexanone requires a large amount of [unclear - possibly a typo, should be "unclear - possibly "resources"]. (e.g., p-chlorophenol + 5) →cyclohexanone), and Its short lifespan and high susceptibility to recombination loss before reaching the active site result in slow deep hydrogenation kinetics.

[0004] Three-dimensional particle electrode enhances mass transfer: To solve the problem of hindered mass transfer between chlorophenol and its intermediate product phenol and the cathode, this invention introduces a Pd-based catalyst as a three-dimensional particle electrode into the electrocatalytic system. Compared with traditional planar electrodes, the particle electrode is suspended in the electrolyte solution, which greatly expands the effective active area of ​​electrocatalysis, shortens the diffusion distance of pollutant molecules to the electrode surface, and effectively overcomes the problem of limited mass transfer of neutral or anionic reactants at the interface.

[0005] Confined modulation of Pd-based electronic structure: To address the lack of electron-deficient Pd sites, this invention utilizes the unique electron-deficient properties within the cavity of CNTs to confine Pd nanoparticles within the CNT cavity. Through the modulation of the Pd-based electronic structure by the cavity, the degree of electronic defects at the Pd sites is significantly enhanced (i.e., increased...). (Proportion). Electron-deficient Pd sites can enhance the chemisorption and activation of electron-rich chlorophenol molecules and intermediate phenol through π-bonding, thereby lowering the reaction energy barrier.

[0006] Increased spatial constraints Application: To solve the problem of high efficiency in electrocatalytic hydrogenation conversion There is a contradiction between the demand and the low utilization rate of CNTs. This invention utilizes the spatial confinement effect of the inner cavity of CNTs to generate... Confined within nanoscale space, reducing The mass transfer distance to diffuse pollutants promotes... Targeted migration and inhibition The ineffective composite is thus met to satisfy the requirements of electrocatalytic deep hydrogenation conversion.

[0007] In summary, the Pd-in-CNTs particle electrode system constructed in this invention, through the synergistic effects of "three-dimensional mass transfer enhancement," "electronic structure regulation," and "spatial confinement enhancement," successfully overcomes the technical bottleneck of synthesizing cyclohexanone from simple dechlorination of chlorophenol pollutants via deep hydrogenation. This method exhibits high conversion rates (95%–99%) and good product selectivity, achieving a high degree of unity between pollutant degradation and resource recovery, and possesses significant environmental benefits and promising industrial application prospects. Summary of the Invention

[0008] The purpose of this invention is to solve the technical problems existing in the prior art and to provide a method for preparing cyclohexanone by hydrogenation catalysis of chlorophenol based on carbon nanotube confined palladium electrode.

[0009] To achieve the above objectives, the technical solution provided by this invention is: a method for preparing cyclohexanone from chlorophenols via hydrogenation catalysis using a confined palladium electrode based on carbon nanotubes. This method first prepares a Pd-in-CNTs catalyst via impregnation and calcination, then constructs a three-dimensional electrocatalytic reaction system: using a platinum sheet as the anode, a graphite plate as the cathode, and Ag / AgCl as the reference electrode, a cation exchange membrane is used to divide the anode and cathode chambers, and Pd-in-CNTs are used as particle electrodes to fill the cathode chamber. Under constant potential conditions, chlorophenolic pollutants in the cathode chamber undergo stepwise hydrogenation dechlorination and synergistic cyclohydrogenation reactions on the surface of the Pd-in-CNTs, directionally converting them into the high-value-added chemical cyclohexanone. The specific steps of this method are as follows: Step 1: First, Pd-in-CNTs catalysts are prepared by confining palladium nanoparticles within carbon nanotubes; Step 2: Construct an electrochemical reaction system using an H-type electrolytic cell, separating the anode and cathode chambers through a Nafion-117 cation exchange membrane; add a chlorophenol-containing electrolyte solution to the cathode chamber, and take an appropriate amount of the Pd-in-CNTs catalyst prepared in Step 1, dispersing it in the cathode chamber by ultrasonic stirring, i.e., filling the cathode chamber with Pd-in-CNTs as particle electrodes; add an electrolyte solution of the same molar concentration to the anode chamber; Step 3: Using a platinum sheet as the anode, a graphite plate as the cathode, and Ag / AgCl as the reference electrode, the entire H-type electrolytic cell is connected to a circulating water system. Under constant temperature and applied voltage conditions, cyclohexanone is produced through a catalytic hydrogenation reaction.

[0010] Preferably, the preparation method of the Pd-in-CNTs catalyst in step one includes the following steps: (1) Preparation of open carbon nanotubes, i.e. O-CNTs: Carbon nanotubes are placed in concentrated nitric acid and refluxed at 100-150 °C. After washing and drying, O-CNTs are obtained. (2) Preparation of Pd-in-CNTs: Palladium chloride solution was added to O-CNTs for impregnation and ultrasonic treatment using the equal volume impregnation method; the impregnated material was dried, ground and then heated to 400-500 ℃ in an inert atmosphere for reduction treatment to obtain Pd-in-CNTs.

[0011] Preferably, the pore volume of CNTs in step (1) is 0.4~0.6 cm³. 3 / g, the mass fraction of concentrated nitric acid is 65%~68%, the stirring and reflux time in the reflux reaction is 10~16 h, and the freeze drying time is 6~10 h.

[0012] Preferably, in step (2), the mass concentration of palladium in the palladium chloride solution is 0.05~0.15 g / mL; the ultrasonic treatment time in the impregnation ultrasonic treatment is 10~20 min; and the drying temperature of the material after impregnation is 110~120 ℃.

[0013] Preferably, the electrolytes in both the cathode chamber and the anode chamber are perchloric acid solutions with a concentration of 0.1~0.5 mol / L, wherein the mass concentration of chlorophenol in the perchloric acid solution in the cathode chamber is 5~50 mg / L.

[0014] Preferably, the amount of Pd-in-CNTs catalyst used in step two is 0.05~0.4 mg / mL.

[0015] Preferably, the applied voltage of the H-type electrolytic cell is -0.3 V to -0.6 V vs. AgCl.

[0016] Preferably, before the catalytic hydrogenation reaction in step three, an inert gas is introduced into the cathode chamber to purge oxygen for 10-20 minutes.

[0017] Beneficial effects of this invention: This invention uses palladium confined in carbon nanotubes as the particle electrode, which, compared with most current Pd-based catalysts, enables the electrocatalytic hydrogenation reduction of chlorophenol to cyclohexanone. The CNT tube cavity allows for better control of the metal catalyst size, improving its reactivity and stability. Confining Pd within the CNT tube increases the generation of electron-deficient Pd sites and enhances... The generation and utilization of active hydrogen shortens the mass transfer distance from active hydrogen to pollutants, thereby significantly improving the performance of deep hydrogenation, effectively preventing the loss and aggregation of active components, and improving the cycle stability of the catalyst. This method recovers high-value chemical raw materials while degrading toxic pollutants, and has significant environmental and economic benefits. Attached Figure Description

[0018] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, are illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0019] Figure 1 This is the electrocatalytic reaction device in the present invention.

[0020] Figure 2 This is a TEM image of the Pd-in-CNTs sample from Embodiment 1 of the present invention.

[0021] Figure 3 This is a TEM image of the Pd-out-CNTs sample from Embodiment 1 of the present invention.

[0022] Figure 4This is an elemental distribution diagram of the Pd-in-CNTs sample in Embodiment 1 of the present invention.

[0023] Figure 5 This is an elemental distribution diagram of the Pd-out-CNTs sample in Embodiment 1 of the present invention.

[0024] Figure 6 XPS spectra of Pd-in-CNTs and Pd-out-CNTs samples in the embodiments of this invention.

[0025] Figure 7 The curve of Pd-in-CNTs electrocatalytic hydrogenation conversion of chlorophenol over time is shown in Example 2 of this invention.

[0026] Figure 8 The curve of Pd-out-CNTs electrocatalytic hydrogenation conversion of chlorophenol over time is shown in Example 2 of this invention.

[0027] Figure 9 This is a bar chart showing the effect of different operating voltages on the electrocatalytic conversion rate of chlorophenol in Embodiment 3 of the present invention.

[0028] Figure 10 This is a bar chart showing the effect of different coexisting ions on the electrocatalytic conversion rate of chlorophenol in Example 4 of this invention. Detailed Implementation

[0029] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0030] This invention discloses a method for the hydrogenation catalysis of chlorophenols to prepare cyclohexanone based on a carbon nanotube-confined palladium electrode. This method utilizes carbon nanotube-confined palladium as a particle electrode to electrocatalyze the reduction of chlorophenols to prepare cyclohexanone. By controlling the microscopic confinement structure of the catalyst and the three-dimensional electrocatalytic system, this invention solves the problems of mass transfer, reaction activity, and selectivity of traditional Pd-based electrocatalysts, achieving a highly efficient and targeted conversion of chlorophenol pollutants to high-value-added cyclohexanone. The conversion rate of chlorophenol organic compounds reaches 95%–99%, exhibiting excellent catalytic activity and product selectivity. This method innovatively combines pollutant degradation with resource recovery, offering advantages such as mild reaction conditions, environmental friendliness, and controllable selectivity, providing a new technological approach for the resource-based treatment of industrial chlorinated organic wastewater.

[0031] Implementation Case 1 Preparation of Pd-out-CNTs 0.5 g of O-CNTs were weighed and mixed with 0.25 mL of xylene. The mixture was sonicated for 10 min to fill the O-CNTs cavity with xylene. Then, 0.25 mL of PdCl2 solution (Pd concentration of 0.1 g / mL) was added, and the mixture was allowed to stand for 30 min. The mixture was then placed in an oven and heated to 110 °C at a rate of 1 °C / min and held for 12 h. The temperature was then increased to 150 °C and held for 5 h to obtain the precursor of Pd-out-CNTs. Finally, the precursor was placed in a tube furnace and heated to 400 °C at a rate of 2 °C / min under an argon atmosphere and held for 2 h to obtain Pd nanoparticles loaded on carbon nanotubes (Pd-out-CNTs).

[0032] The morphology of Pd-in-CNTs and Pd-out-CNTs in the samples was characterized using HAADF-scanning transmission electron microscopy (HAADF-STEM). Figure 2 As shown, the dark-field TEM image of Pd-in-CNTs clearly shows that cylindrical nanoparticles are uniformly distributed within the CNT lumen. Figure 3 The CNTs shown have a large number of spherical nanoparticles uniformly covering their outer walls. Figure 4 and 5 As shown, surface scan analysis of C, O, and Pd elements in the samples confirmed that Pd nanoparticles in the Pd-in-CNTs samples were confined within the CNT lumen, while spherical Pd nanoparticles in the Pd-out-CNTs samples were loaded onto the outer surface of the CNTs. X-ray photoelectron spectroscopy (XPS) was used to investigate the chemical valence state of Pd in ​​both Pd-in-CNTs and Pd-out-CNTs. Figure 6 As shown, peak fitting analysis results indicate that the Pd 3d energy spectra of both Pd-in-CNTs and Pd-out-CNTs exhibit four peaks at 342.9 eV, 340.6 eV, 337.6 eV, and 335.4 eV, corresponding to Pd, respectively. 2+ 3D 3 / 2 Pd 0 3D 3 / 2 Pd 2+ 3D 5 / 2 and Pd 0 3D 5 / 2 Characteristic peaks. Based on electron-deficient Pd (Pd 2+ ) and electron-rich Pd (Pd 0 The peak area clearly indicates that the Pd element in Pd-in-CNTs is mainly Pd. 2+ The main component is Pd, while in Pd-out-CNTs, Pd... 2+ / Pd 0The ratio was close to 1:1. The results confirmed that utilizing the unique electronic regulation effect of the inner wall of CNTs can promote a high proportion of electron-deficient properties in the generated Pd nanoparticles. These electron-deficient Pd sites are beneficial for enhancing the adsorption and activation of electron-rich chlorophenol pollutants, and are key to improving catalytic performance.

[0033] Implementation Case 2 Based on the characterization analysis results of Implementation Case 1, this study further explored the performance of Pd-in-CNTs and Pd-out-CNTs in the electrocatalytic hydrogenation reduction of p-chlorophenol.

[0034] This experiment employed an H-type electrolytic cell to construct a three-electrode system, with a platinum sheet (1 cm × 3 cm) as the anode, a graphite plate (2 cm × 2 cm) as the cathode, and Ag / AgCl as the reference electrode. A cation exchange membrane (Nafion-117) separated the anode and cathode chambers. The anode chamber contained 70 mL of a 0.2 mol / L HClO4 solution, while the cathode chamber contained 70 mL of a mixed solution of HClO4 and p-chlorophenol, with the HClO4 concentration also at 0.2 mol / L and the p-chlorophenol concentration at 10 mg / L. Pd-in-CNTs or Pd-out-CNTs (0.2 g / L) prepared in this experiment were dispersed in the system as particle electrodes. Before the electrocatalytic reaction, nitrogen gas was purged into the cathode chamber for 20 min to eliminate the influence of dissolved oxygen in the solution. Given that industrial wastewater containing chlorophenol is typically discharged at high temperatures, the entire electrolytic cell was connected to a circulating water system, and the reaction temperature was set at 50°C. During the reaction, 0.5 mL of the cathode reaction solution was drawn at 0, 1, 2, 5, 10, 20, 40, 60, 80, 100, 120, 140, 160, and 180 min, respectively, and filtered through a 0.22 μm nylon filter for liquid phase analysis.

[0035] When the particle electrodes dispersed in the cathode chamber are Pd-in-CNTs, the changes in the concentrations of p-chlorophenol and reduction products over time during the experiment are as follows: Figure 7As shown in the figure, p-chlorophenol was completely degraded within 10 minutes, during which phenol was rapidly generated. At 1 minute of reaction, the efficiency of converting p-chlorophenol to phenol reached 99.3%. At 2 minutes of reaction, 5.5% cyclohexanone was detected in the reaction system. At 10 minutes of reaction, p-chlorophenol was completely converted to phenol (77.2%) and cyclohexanone (22.8%). As the reaction continued, the concentration of phenol gradually decreased, while the concentration of cyclohexanone continuously increased. At 120 minutes of reaction, 1% cyclohexanol was detected in the system. Until 180 minutes of reaction, the efficiencies of converting p-chlorophenol to cyclohexanone and cyclohexanol reached 95.1% and 4.9%, respectively.

[0036] When the particle electrodes dispersed in the cathode chamber are Pd-out-CNTs, although the dechlorination of p-chlorophenol can be achieved, the conversion rate is significantly slower. At the end of the reaction, phenol is still the main product (75.5%), and the yield of cyclohexanone is only 20.5%. This indicates that traditional Pd-out-CNTs catalysts are difficult to achieve the deep saturated hydrogenation reaction of chlorophenol to cyclohexanone.

[0037] In summary, the experimental results demonstrate that Pd-in-CNTs particle electrodes exhibit significantly superior catalytic activity and product selectivity compared to traditional Pd-out-CNTs in the electrocatalytic hydrogenation reduction of p-chlorophenol to cyclohexanone. This difference further confirms that the confinement effect within the CNT cavity can enhance the catalytic activity. This allows for the efficient resource-based transformation of chlorophenol pollutants.

[0038] Implementation Case 3 To investigate the effect of reaction voltage on the performance of chlorophenol by the electrocatalytic hydrogenation reduction of Pd-in-CNTs, we conducted electrolysis reactions under constant voltage conditions of -0.3 V, -0.35 V, -0.4 V, -0.45 V, and -0.5 V vs. AgCl. The effects on the electrocatalytic hydrogenation reduction of chlorophenol are as follows: Figure 9 As shown, the efficiency of the complete degradation of p-chlorophenol to cyclohexanone initially increases and then decreases as the voltage increases from -0.3 V to -0.5 V. This experimental phenomenon is attributed to the applied voltage exceeding [a certain value]. The generation voltage easily leads to competing hydrogen evolution reactions, reducing the selectivity of the electrocatalytic hydrogenation reduction reaction. As shown in the figure, at set voltages of -0.3 V, -0.35 V, and -0.5 V, some p-chlorophenol is reduced only to phenol. Specifically, at -0.3 V, the efficiency of p-chlorophenol to cyclohexanone is 84.3%. At -0.35 V, the conversion efficiency further increases to 91.4%. At -0.5 V, the efficiency of p-chlorophenol to cyclohexanone is 90%, with 5.7% of p-chlorophenol being converted to cyclohexanol. When the voltage is set to -0.4 V and -0.45 V, p-chlorophenol is completely electrocatalytically hydrogenated to cyclohexanone and cyclohexanol. According to the experimental data, the efficiency of phenol to cyclohexanone is highest at -0.4 V, reaching 94.3%, therefore -0.4 V is considered the optimal voltage condition.

[0039] Implementation Case 4 Under the optimal voltage of -0.4 V, 10 mmol / L of different common coexisting inorganic ions (Cl) were added to the cathode chamber. - PO4 3- and NH 4+ Using humic acid as an example, and simulating an industrial wastewater environment, we explored the effects of these factors on the performance of chlorophenol during the electrocatalytic hydrogenation reduction of Pd-in-CNTs. Figure 10 It can be seen from Cl - The electrocatalytic hydrogenation reduction of Pd-in-CNTs has almost no effect on the performance of chlorophenol, while PO4 3- and NH 4+ The presence of ions slightly reduced the efficiency of the electrocatalytic hydrogenation reduction of phenol to cyclohexanone; however, the conversion rate remained above 95%. In contrast, the presence of humic acid may affect the mass transfer between the electrode and the reactants, with a slightly greater impact on the system than other ions. Overall, the Pd-in-CNTs electrocatalytic system exhibited good anti-interference capabilities.

[0040] Without causing conflict, those skilled in the art can freely combine and use the above-mentioned additional technical features.

[0041] The above description is only a preferred embodiment of the present invention. Any technical solution that achieves the purpose of the present invention by essentially the same means is within the protection scope of the present invention.

Claims

1. A method for preparing cyclohexanone from chlorophenol by hydrogenation catalysis using a carbon nanotube-confined palladium electrode, characterized in that: This method first prepares Pd-in-CNTs catalysts via impregnation and calcination, then constructs a three-dimensional electrocatalytic reaction system: using a platinum sheet as the anode, a graphite plate as the cathode, and Ag / AgCl as the reference electrode, a cation exchange membrane is used to separate the anode and cathode chambers, and Pd-in-CNTs are used as particle electrodes to fill the cathode chamber; under constant potential conditions, chlorophenolic pollutants in the cathode chamber undergo stepwise hydrogenation dechlorination and synergistic cyclohydrogenation reactions on the surface of Pd-in-CNTs, directionally converting them into the high-value-added chemical cyclohexanone; the specific steps of this method are as follows: Step 1: First, Pd-in-CNTs catalysts are prepared by confining palladium nanoparticles within carbon nanotubes; Step 2: Construct an electrochemical reaction system using an H-type electrolytic cell, separating the anode and cathode chambers through a Nafion-117 cation exchange membrane; add a chlorophenol-containing electrolyte solution to the cathode chamber, and take an appropriate amount of the Pd-in-CNTs catalyst prepared in Step 1, dispersing it in the cathode chamber by ultrasonic stirring, i.e., filling the cathode chamber with Pd-in-CNTs as particle electrodes; add an electrolyte solution of the same molar concentration to the anode chamber; Step 3: Using a platinum sheet as the anode, a graphite plate as the cathode, and Ag / AgCl as the reference electrode, the entire H-type electrolytic cell is connected to a circulating water system. Under constant temperature and applied voltage conditions, cyclohexanone is produced through a catalytic hydrogenation reaction.

2. The method for preparing cyclohexanone from chlorophenol by hydrogenation catalysis based on a carbon nanotube confined palladium electrode according to claim 1, characterized in that: The preparation method of the Pd-in-CNTs catalyst in step one includes the following steps: (1) Preparation of open carbon nanotubes, i.e. O-CNTs: Carbon nanotubes are placed in concentrated nitric acid and refluxed at 100-150 °C. After washing and drying, O-CNTs are obtained. (2) Preparation of Pd-in-CNTs: Palladium chloride solution was added to O-CNTs for impregnation and ultrasonic treatment using the equal volume impregnation method; the impregnated material was dried, ground and then heated to 400-500 ℃ in an inert atmosphere for reduction treatment to obtain Pd-in-CNTs.

3. The method for preparing cyclohexanone from chlorophenol by hydrogenation catalysis based on a carbon nanotube confined palladium electrode according to claim 2, characterized in that: The pore volume of CNTs in step (1) is 0.4~0.6 cm³. 3 / g, the mass fraction of concentrated nitric acid is 65%~68%, the stirring and reflux time in the reflux reaction is 10~16 h, and the freeze drying time is 6~10 h.

4. The method for preparing cyclohexanone from chlorophenol by hydrogenation catalysis based on a carbon nanotube confined palladium electrode according to claim 2, characterized in that: In step (2), the mass concentration of palladium in the palladium chloride solution is 0.05~0.15 g / mL; the ultrasonic treatment time in the impregnation ultrasonic treatment is 10~20 min; and the drying temperature of the material after impregnation is 110~120 ℃.

5. The method for preparing cyclohexanone from chlorophenol by hydrogenation catalysis based on a carbon nanotube confined palladium electrode according to claim 1, characterized in that: The electrolytes in both the cathode and anode chambers are perchloric acid solutions with a concentration of 0.1–0.5 mol / L. The perchloric acid solution in the cathode chamber contains chlorophenol with a mass concentration of 5–50 mg / L.

6. The method for preparing cyclohexanone from chlorophenol by hydrogenation catalysis based on a carbon nanotube confined palladium electrode according to claim 1, characterized in that: The amount of Pd-in-CNTs catalyst used in step two is 0.05~0.4 mg / mL.

7. The method for preparing cyclohexanone from chlorophenol by hydrogenation catalysis based on a carbon nanotube confined palladium electrode according to claim 1, characterized in that: The applied voltage for the H-type electrolytic cell is -0.3 V to -0.6 V vs. AgCl.

8. The method for preparing cyclohexanone from chlorophenol by hydrogenation catalysis based on a carbon nanotube confined palladium electrode according to claim 1, characterized in that: Before the catalytic hydrogenation reaction in step three, inert gas needs to be introduced into the cathode chamber to remove oxygen for 10-20 minutes.

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