Catalyst for catalyzing ethylene oxidation to generate ethylene glycol and preparation method and application thereof

Abstract

The application discloses a catalyst for catalyzing ethylene oxidation to generate ethylene glycol and a preparation method and application thereof, and relates to the technical field of ethylene glycol synthesis. The preparation method comprises the following steps: dissolving a palladium source, a silver source and a carbonyl metal compound in a mixed solvent containing acetic acid and N,N-dimethylformamide to obtain a precursor mixed solution; placing hydrophobic carbon paper in the precursor mixed solution and performing a solvothermal reaction to enable Pd-doped Ag nanoparticles to grow in situ on the hydrophobic carbon paper, thereby obtaining hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles; and immersing the hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles in a phytic acid solution to enable phytic acid to be modified on the surface of the Pd-doped Ag nanoparticles, thereby obtaining a catalyst for catalyzing ethylene oxidation to generate ethylene glycol. By growing Pd-doped Ag nanoparticles in situ on the hydrophobic carbon paper and performing phytic acid surface modification, a self-supporting catalyst with the functions of gas diffusion, stable conductive loading, bimetallic activity regulation and interface microenvironment adjustment is constructed, so that the selectivity, current utilization efficiency and reaction stability of ethylene electrocatalytic oxidation to generate ethylene glycol are improved.

Description

Technical Field

[0001] This invention relates to the field of ethylene glycol synthesis technology, specifically to a catalyst for catalyzing the oxidation of ethylene to ethylene glycol, its preparation method, and its application. Background Technology

[0002] Ethylene glycol is an important bulk basic chemical, widely used in polyester materials, cooling media, and other fields. Existing ethylene glycol production routes mainly include the ethylene epoxidation-hydration route, the syngas-to-ethylene glycol route, and the biomass conversion route. However, these routes usually suffer from problems such as long reaction processes, harsh conditions, high energy consumption, insufficient catalyst stability, or difficulty in controlling product selectivity, making it difficult to simultaneously meet the requirements of green, low-energy consumption, and high-selectivity production.

[0003] In recent years, electrocatalytic synthesis has been considered a potential green route for the preparation of ethylene glycol due to its advantages such as ambient temperature and pressure, mild reaction conditions, and the ability to be driven by renewable electricity. Among these methods, the direct electrocatalytic oxidation of ethylene using water as an oxygen source can avoid the use of external strong oxidants and is expected to simplify the synthesis steps of ethylene glycol. However, in this reaction process, a stable and efficient gas-liquid-solid three-phase reaction interface needs to be formed between ethylene gas, water molecules, electrolyte, and solid catalyst. Simultaneously, the catalyst must be able to effectively regulate the adsorption, activation, and conversion processes of ethylene and oxygen-containing intermediates. This application employs a three-electrode gas diffusion electrode system, using a phytic acid-modified Pd-doped Ag catalyst supported on hydrophobic carbon paper as the working electrode, and water as the oxygen source for the electrocatalytic oxidation of ethylene to prepare ethylene glycol.

[0004] Existing electrocatalysts typically employ a method of coating powdered catalysts onto the surface of a conductive support to prepare electrodes. This method is prone to affecting reaction stability due to binders covering active sites, increasing electron transport resistance, or catalyst layer detachment. Furthermore, single Ag-based catalysts have limited adsorption and activation capabilities for ethylene, water molecules, and oxygen-containing reaction intermediates, making it difficult to balance ethylene glycol formation rate and selectivity at high current densities. Moreover, the catalytic effects of Ag doped with different metals vary significantly; not all metal doping can improve ethylene glycol selectivity.

[0005] Therefore, existing technologies still require a catalyst preparation method that can construct stable bimetallic active sites in situ on a hydrophobic conductive substrate and regulate the microenvironment of the reaction interface through surface modification, in order to improve the selectivity and stability of the electrocatalytic oxidation of ethylene to ethylene glycol. Summary of the Invention

[0006] One objective of the first aspect of this invention is to provide a method for preparing a catalyst for the catalytic oxidation of ethylene to ethylene glycol, thereby solving the technical problems of low gas mass transfer efficiency, insufficient stability of the active component and conductive substrate, and limited ability to regulate the microenvironment of the reaction interface in existing catalysts for the electrocatalytic oxidation of ethylene to ethylene glycol, which result in low selectivity for ethylene glycol formation and low current utilization efficiency.

[0007] Another objective of the first aspect of this invention is to further improve the Faraday efficiency and yield of ethylene glycol.

[0008] The second aspect of this invention aims to provide a catalyst for the catalytic oxidation of ethylene to ethylene glycol, prepared according to the above-described preparation method.

[0009] The third aspect of this invention aims to provide an application of the above-mentioned catalyst in the electrocatalytic oxidation of ethylene to ethylene glycol.

[0010] According to a first aspect of the present invention, the present invention provides a method for preparing a catalyst for the catalytic oxidation of ethylene to ethylene glycol, comprising the following steps: Palladium source, silver source and carbonyl metal compound were dissolved in a mixed solvent containing acetic acid and N,N-dimethylformamide to obtain a precursor mixture; The hydrophobic carbon paper is placed in the precursor mixture and subjected to a solvothermal reaction, so that Pd-doped Ag nanoparticles are grown in situ on the hydrophobic carbon paper to obtain hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles. The hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles was immersed in a phytic acid solution to modify the surface of the Pd-doped Ag nanoparticles with phytic acid, thereby obtaining a catalyst for catalyzing the oxidation of ethylene to ethylene glycol.

[0011] Optionally, the hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles is soaked in the phytic acid solution for any value between 1 h and 7 h.

[0012] Optionally, the amount of Pd doping in the Pd-doped Ag nanoparticles is any value between 2wt% and 30wt%.

[0013] Optionally, the temperature of the solvothermal reaction is any value between 120℃ and 160℃, and the reaction time is any value between 12h and 36h.

[0014] Optionally, the palladium source includes potassium tetrachloropalladium chloride or palladium acetylacetonate, the silver source includes silver trifluoroacetate, silver nitrate or silver chloride, and the carbonyl metal compound includes tungsten hexacarbonyl or nickel tetracarbonyl.

[0015] Optionally, before obtaining the precursor mixture, the mixture containing the palladium source, the silver source, the carbonyl metal compound, and the mixed solvent is subjected to ultrasonic treatment; wherein, The duration of the ultrasonic treatment is any value between 20 min and 60 min.

[0016] Optionally, it also includes: After the solvothermal reaction, the reaction product is washed and dried to obtain the hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles. The washing process uses ethanol, and the drying process is carried out at any temperature between 40°C and 80°C.

[0017] According to a second aspect of the present invention, the present invention also provides a catalyst for catalytic oxidation of ethylene to ethylene glycol, said catalyst being prepared by any of the preparation methods described above; The catalyst comprises hydrophobic carbon paper and phytic acid-modified Pd-doped Ag nanoparticles grown in situ on the hydrophobic carbon paper, wherein the doping amount of Pd in ​​the Pd-doped Ag nanoparticles is any value between 2wt% and 30wt%.

[0018] According to a third aspect of the present invention, the present invention provides an application of the above-mentioned catalyst in the electrocatalytic oxidation of ethylene to ethylene glycol, wherein the catalyst is used as the working electrode, water is used as the oxygen source, and ethylene is subjected to an electrocatalytic oxidation reaction in the presence of an electrolyte to produce ethylene glycol.

[0019] Optionally, the electrocatalytic oxidation reaction is carried out in a three-electrode gas diffusion electrode electrolysis system, which includes the working electrode, a silver / silver chloride reference electrode, a Pt-loaded carbon felt counter electrode, and a gas chamber; wherein, Ethylene gas is continuously introduced into the gas chamber, the electrolyte is a 0.1 mol / L-1.0 mol / L sodium perchlorate solution, and the current density for constant current electrolysis is 75 mA / cm². 2 -120mA / cm 2 Any value among them.

[0020] This invention utilizes a continuous preparation route involving in-situ loading of hydrophobic carbon paper, construction with Pd-doped Ag nanoparticles, and surface modification with phytic acid. This route enables the direct growth and immobilization of catalytically active components on a hydrophobic conductive substrate, forming a self-supporting catalyst electrode structure that requires no additional binder. On one hand, the hydrophobic carbon paper serves as a conductive support and gas diffusion interface, facilitating the transport of ethylene gas to the catalytically active sites. On the other hand, the Pd-doped Ag nanoparticles can modulate the electronic structure of the Ag-based catalyst and the adsorption behavior of reaction intermediates, enhancing the selectivity of the ethylene glycol production pathway during the electro-oxidation of ethylene. Simultaneously, the phytic acid modification layer can regulate the hydrophilicity of the catalyst surface, the local reaction microenvironment, and the interfacial reaction behavior during water-based oxidation through its phosphorus- and oxygen-containing functional groups, thereby improving the reaction efficiency and selectivity of ethylene oxidation to ethylene glycol using water as the oxygen source.

[0021] Furthermore, by controlling the Pd doping amount within the range of 2wt%-30wt%, this invention can utilize the electronic structure regulation effect of Pd on Ag-based nanoparticles to improve the catalyst's adsorption and activation capabilities for ethylene, water molecules, and oxygen-containing reaction intermediates, making the ethylene oxidation process more inclined to produce ethylene glycol. The Ag component can provide a basic catalytic interface for the electro-oxidation of ethylene, while the introduction of Pd can change the local electron density on the Ag surface and the binding strength of reaction intermediates, thereby optimizing the formation, stabilization, and conversion processes of key intermediates in the ethylene oxidation process and improving the Faraday efficiency and yield of ethylene glycol.

[0022] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0023] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic flowchart of a method for preparing a catalyst according to an embodiment of the present invention; Figure 2 This is a graph showing the relationship between the amount of Pd doping and the Faraday efficiency in Pd-doped Ag nanoparticles according to an embodiment of the present invention. Figure 3 This is a graph showing the immersion time versus Faraday efficiency of hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles in phytic acid solution according to an embodiment of the present invention. Figure 4 This is a schematic structural diagram of a three-electrode gas diffusion electrode electrolytic cell according to an embodiment of the present invention; Figure 5 This is a transmission electron microscope image of the catalyst prepared according to Example 1 of the present invention; Figure 6 This is an X-ray diffraction pattern of the catalyst prepared according to Example 1 of the present invention; Figure 7 The X-ray photoelectron spectrum of the catalyst prepared according to Example 1 of the present invention is shown below. Figure 8 This is an X-ray elemental distribution diagram of the catalyst prepared according to Example 1 of the present invention; Figure 9 The 1H NMR spectrum of the ethylene glycol electrolyte catalyzed by the catalyst prepared according to Example 1 of the present invention; Figure 10 The image shows the carbon NMR spectrum of the ethylene glycol electrolyte prepared by the catalyst according to Example 1 of the present invention. Figure 11 These are performance characterization diagrams of the catalysts prepared according to Example 1 and Comparative Examples 1-3 of the present invention.

[0024] Figure label: 100 - Three-electrode gas diffusion electrode electrolytic cell, 10 - Gas flow channel plate, 11 - Ethylene glycol outlet, 12 - Ethylene inlet, 20 - Gas diffusion electrode, 30 - Ion exchange membrane, 40 - Cathode, 50 - Counter-electrode side flow channel plate. Detailed Implementation

[0025] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0026] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0027] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0028] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] Figure 1 This is a schematic flowchart illustrating a method for preparing a catalyst according to an embodiment of the present invention. Figure 2 This is a graph showing the relationship between the amount of Pd doping and the Faraday efficiency in Pd-doped Ag nanoparticles according to an embodiment of the present invention. Figure 3 This is a graph showing the immersion time versus Faraday efficiency of hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles in phytic acid solution according to an embodiment of the present invention.

[0030] like Figure 1 As shown, the present invention provides a method for preparing a catalyst for the catalytic oxidation of ethylene to ethylene glycol, comprising the following steps: Step S100: Dissolve the palladium source, silver source and carbonyl metal compound in a mixed solvent containing acetic acid and N,N-dimethylformamide to obtain a precursor mixture; Step S200: Place the hydrophobic carbon paper in the precursor mixture and carry out a solvothermal reaction to allow Pd-doped Ag nanoparticles to grow in situ on the hydrophobic carbon paper, thereby obtaining hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles. Step S300: Immerse hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles into a phytic acid solution to modify the surface of the Pd-doped Ag nanoparticles with phytic acid, thereby obtaining a catalyst for catalyzing the oxidation of ethylene to ethylene glycol.

[0031] In this embodiment, the preparation method of the catalyst for catalyzing the oxidation of ethylene to ethylene glycol involves first dissolving a palladium source, a silver source, and a carbonyl metal compound in a mixed solvent containing acetic acid and N,N-dimethylformamide to obtain a precursor mixture. This allows the Pd and Ag precursors to be fully dispersed in the solvent system, forming a metal precursor environment suitable for subsequent in-situ growth. Next, hydrophobic carbon paper is placed in the precursor mixture and subjected to a solvothermal reaction, enabling Pd-doped Ag nanoparticles to nucleate and grow in situ on the surface of the hydrophobic carbon paper, resulting in hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles. Subsequently, the hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles is immersed in a phytic acid solution, allowing the phytic acid to modify the surface of the Pd-doped Ag nanoparticles, thus obtaining the catalyst for catalyzing the oxidation of ethylene to ethylene glycol.

[0032] In this embodiment, a continuous preparation route involving in-situ loading of hydrophobic carbon paper, construction of Pd-doped Ag nanoparticles, and surface modification with phytic acid enables the direct growth and fixation of catalytically active components onto a hydrophobic conductive substrate, forming a self-supporting catalyst electrode structure without the need for additional binders. On one hand, the hydrophobic carbon paper serves as a conductive support and gas diffusion interface, facilitating the transport of ethylene gas to the catalytically active sites. On the other hand, the Pd-doped Ag nanoparticles can modulate the electronic structure of the Ag-based catalyst and the adsorption behavior of reaction intermediates, enhancing the selectivity of the ethylene glycol generation pathway during the electro-oxidation of ethylene. Simultaneously, the phytic acid modification layer can regulate the hydrophilicity of the catalyst surface, the local reaction microenvironment, and the interfacial reaction behavior during water-based oxidation through its phosphorus- and oxygen-containing functional groups, thereby improving the reaction efficiency and selectivity of ethylene oxidation to ethylene glycol using water as an oxygen source.

[0033] Furthermore, since the Pd-doped Ag nanoparticles are grown in situ on the surface of hydrophobic carbon paper, rather than the powder catalyst being coated onto the support surface with a binder, the resulting catalyst has better conductivity continuity, interfacial bonding stability, and resistance to shedding. This avoids the problem of binders covering active sites or reducing electron transport efficiency, thereby improving the structural stability and catalytic stability of the catalyst under constant current electrolysis conditions.

[0034] In a further embodiment, the hydrophobic carbon paper serves as a conductive hydrophobic substrate, and the Pd-doped Ag nanoparticles are grown in situ on the surface of the hydrophobic carbon paper via a solvothermal reaction to form a self-supporting catalyst that can be directly used as a working electrode. In this embodiment, the hydrophobic carbon paper serves as a conductive substrate, providing a continuous electron transport pathway for the Pd-doped Ag nanoparticles. Furthermore, the hydrophobic carbon paper is suitable for gas diffusion electrode systems, facilitating the transport of ethylene gas at the electrode interface and its contact with catalytic active sites. Because the Pd-doped Ag nanoparticles are grown in situ on the surface of the hydrophobic carbon paper, rather than being a mixture of powdered catalyst and binder coated onto the carrier surface, the problems of binder covering catalytic active sites or reducing electrode conductivity are avoided. This also improves the bonding strength between the catalytic active component and the conductive substrate, resulting in better structural stability and resistance to shedding during constant current electrolysis.

[0035] like Figure 3As shown, in a further embodiment, the hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles is immersed in phytic acid solution for any value between 1 h and 7 h. That is, the immersion time can be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, or 7 h, or any other value within the 1 h-7 h range. In this embodiment, by controlling the immersion time of the hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles in phytic acid solution within the range of 1 h-7 h, the degree of modification of the Pd-doped Ag nanoparticle surface by phytic acid can be adjusted, resulting in the formation of an appropriate phytic acid modification layer on the catalyst surface. Appropriate phytic acid modification allows the phosphate groups in the phytic acid molecules to coordinate, adsorb, or interfacially bind with the surface of the metal nanoparticles, thereby adjusting the electronic environment and hydrophilic / hydrophobic interface state of the catalyst surface. This makes it easier for water molecules to participate in the oxidation reaction on the catalyst surface and promotes the selective conversion of ethylene to ethylene glycol.

[0036] In other embodiments, when the soaking time is too short, the amount of phytic acid modified on the surface of Pd-doped Ag nanoparticles is insufficient, making it difficult to fully regulate the reaction microenvironment on the catalyst surface. This results in an insignificant interfacial modulation effect of water in the oxidation process and limited improvement in ethylene glycol selectivity. When the soaking time is too long, phytic acid may be over-adsorbed on the nanoparticle surface or form a thick coating layer, causing some metal active sites to be shielded, affecting the contact between ethylene and the catalyst surface and the electron transfer process. By limiting the soaking time to 1-7 hours, a balance can be achieved between sufficient phytic acid modification and the degree of exposure of active sites, thereby improving the catalytic activity and selectivity of the catalyst for the oxidation of ethylene to ethylene glycol.

[0037] like Figure 2 As shown, in a further embodiment, the solvent for the phytic acid solution is ethanol. Ethanol can reduce the viscosity of the phytic acid system and improve the wettability of the phytic acid solution on the Pd / Ag / CP surface, allowing phytic acid molecules to contact and modify the surface of Pd-doped Ag nanoparticles more uniformly. Phytic acid molecules contain multiple phosphate groups, which can adsorb or coordinate with the surface of Pd-doped Ag nanoparticles, thereby forming a phosphorus- and oxygen-containing functional group modification layer on the surface of the metal nanoparticles. This modification layer can regulate the hydrophilicity of the catalyst surface, the local water molecule environment, and the adsorption state of oxygen-containing reaction intermediates, allowing water to participate more effectively as an oxygen source in the ethylene oxidation reaction, thereby improving the selectivity of ethylene to ethylene glycol conversion.

[0038] Furthermore, rinsing with anhydrous ethanol can remove unbound or weakly adsorbed free phytic acid from the catalyst surface, preventing excessive phytic acid from covering the metal active sites or entering the electrolyte during electrolysis and affecting reaction stability; drying can remove ethanol residue, allowing the phytic acid modification layer to be stably retained on the surface of Pd-doped Ag nanoparticles.

[0039] In a further embodiment, the Pd doping amount in the Pd-doped Ag nanoparticles is any value between 2wt% and 30wt%, that is, the Pd doping amount can be 2wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, or 30wt%, or any other value between 2wt% and 30wt%. In this embodiment, by controlling the Pd doping amount within the range of 2wt%-30wt%, the electronic structure regulation effect of Pd on Ag-based nanoparticles can be utilized to improve the catalyst's adsorption and activation ability for ethylene, water molecules, and oxygen-containing reaction intermediates, making the ethylene oxidation process more inclined to produce ethylene glycol. The Ag component can provide a basic catalytic interface for the electro-oxidation of ethylene, while the introduction of Pd can change the local electron density on the Ag surface and the binding strength of reaction intermediates, thereby optimizing the formation, stabilization, and conversion process of key intermediates in the ethylene oxidation process and improving the Faraday efficiency and yield of ethylene glycol.

[0040] In other embodiments, when the Pd doping amount is too low, its regulatory effect on the electronic structure and intermediate adsorption behavior of the Ag-based catalyst surface is insufficient, making it difficult for the catalyst to fully exert the bimetallic synergistic effect. When the Pd doping amount is too high, too many Pd-related sites may form on the catalyst surface, altering the original reaction selectivity of the Ag-based catalytic interface, and even promoting side reactions or reducing the selectivity of the ethylene glycol formation pathway. By limiting the Pd doping amount to 2wt%-30wt%, a better match can be achieved between the Ag-based catalytic activity and the regulatory effect of Pd doping, thereby improving the selectivity and stability of the catalyst for the oxidation of ethylene to ethylene glycol.

[0041] In a further embodiment, the solvothermal reaction temperature is any value between 120℃ and 160℃, and the reaction time is any value between 12h and 36h. That is, the solvothermal reaction temperature can be 120℃, 130℃, 140℃, 150℃, or 160℃, or any other value between 120℃ and 160℃; the reaction time can be 12h, 18h, 24h, 30h, or 36h, or any other value between 12h and 36h. In this embodiment, by controlling the solvothermal reaction temperature within the range of 120℃-160℃ and the reaction time within the range of 12h-36h, the palladium and silver sources can undergo controlled reduction, nucleation, and growth on the surface of the hydrophobic carbon paper, allowing Pd-doped Ag nanoparticles to be uniformly and in-situ loaded onto the hydrophobic carbon paper. Appropriate reaction temperature and reaction time facilitate the full conversion of the metal precursor and enable a stable bond between the nanoparticles and the hydrophobic carbon paper, thereby improving the catalyst's conductivity, the uniformity of active site distribution, and its resistance to shedding during electrolysis.

[0042] In other embodiments, when the solvothermal reaction temperature is too low or the reaction time is too short, the metal precursor conversion is insufficient, and the nucleation and growth of Pd-doped Ag nanoparticles are inadequate, easily leading to low catalyst loading, uneven particle distribution, or insufficient active sites. When the reaction temperature is too high or the reaction time is too long, the nanoparticles may overgrow, agglomerate, or locally accumulate, reducing the specific surface area of ​​the catalyst and the exposure of active sites. By limiting the solvothermal reaction conditions within the above ranges, a balance can be achieved between sufficient metal nanoparticle formation, controllable particle size, and stable hydrophobic carbon paper loading, thereby obtaining a highly stable catalyst suitable for the electrocatalytic oxidation of ethylene.

[0043] In a further embodiment, the palladium source includes potassium tetrachloropalladate, palladium chloride, and palladium acetylacetonate; the silver source includes silver trifluoroacetate, silver nitrate, and silver chloride; and the carbonyl metal compound includes tungsten hexacarbonyl and nickel tetracarbonyl. In a preferred embodiment, by selecting potassium tetrachloropalladate as the palladium source, silver trifluoroacetate as the silver source, and tungsten hexacarbonyl as the carbonyl metal compound, a relatively uniform reaction system can be formed between Pd and Ag precursors in an acetic acid / N,N-dimethylformamide mixed solvent, and in-situ growth of Pd-doped Ag nanoparticles on the surface of hydrophobic carbon paper can be achieved under solvothermal conditions. Potassium tetrachloropalladate can provide Pd species that can participate in doping, silver trifluoroacetate can provide Ag species required for the formation of Ag-based nanoparticles, and tungsten hexacarbonyl in the solvothermal system helps to regulate the reduction and nucleation process of the metal precursor, thereby promoting the formation of well-dispersed Pd-doped Ag nanoparticles.

[0044] In this embodiment, the aforementioned precursor combination enables the synergistic transformation of Pd and Ag in the same solvothermal system, which is beneficial for forming a bimetallic nanostructure rather than a simple single metal particle or mechanically mixed structure. The resulting catalyst possesses both the Ag-based catalytic interface and the Pd doping regulation effect, exhibiting superior reaction selectivity and catalytic activity in the electrocatalytic oxidation of ethylene to ethylene glycol.

[0045] In this embodiment, potassium tetrachloropalladate is used as the Pd source, silver trifluoroacetate as the Ag source, and tungsten hexacarbonyl as the carbonyl metal compound. By co-dissolving and dispersing these compounds in a mixed solvent system of acetic acid and N,N-dimethylformamide, a uniform metal precursor environment is provided for the subsequent in-situ growth of Pd-doped Ag nanoparticles. The volume ratio of acetic acid to N,N-dimethylformamide is 1:4, which is beneficial for balancing the solubility of the metal precursor, the wetting contact with the hydrophobic carbon paper surface, and the control of nucleation and growth during the solvothermal reaction, allowing the Pd-doped Ag nanoparticles to be uniformly loaded onto the hydrophobic carbon paper surface.

[0046] In a further embodiment, before obtaining the precursor mixture, the mixture containing the palladium source, silver source, carbonyl metal compound and mixed solvent is subjected to ultrasonic treatment; wherein the ultrasonic treatment time is any value between 20 min and 60 min, that is, the ultrasonic treatment time can be 20 min, 30 min, 40 min, 50 min or 60 min, or any other value between 20 min and 60 min.

[0047] In this embodiment, by subjecting the mixed system containing palladium source, silver source, carbonyl metal compound and mixed solvent to ultrasonic treatment for 20-60 minutes before the solvothermal reaction, the full dissolution and uniform dispersion of each metal precursor in the mixed solvent of acetic acid and N,N-dimethylformamide can be promoted, reducing local concentration differences and agglomeration of precursors, and providing a uniform reaction environment for the uniform nucleation and in-situ growth of Pd-doped Ag nanoparticles.

[0048] In other embodiments, when the ultrasonic treatment time is too short, the palladium source, silver source, and carbonyl metal compound may not be sufficiently dispersed, easily leading to uneven local nucleation, widened particle size distribution, or uneven loading during the solvothermal reaction. When the ultrasonic treatment time is too long, the further improvement in the homogeneity of the precursor mixture is limited, and it may increase process time and energy consumption. By limiting the ultrasonic treatment time to 20-60 minutes, a balance can be achieved between uniform precursor dispersion and process efficiency, thereby improving the repeatability and structural uniformity of catalyst preparation.

[0049] In a further embodiment, it also includes: After the solvothermal reaction, the reaction product is washed and dried to obtain hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles. The washing is performed with ethanol, and the drying temperature is any value between 40℃ and 80℃, that is, the drying temperature can be 40℃, 50℃, 60℃, 70℃ or 80℃, or any other value between 40℃ and 80℃.

[0050] In this embodiment, washing the reaction product with ethanol after the solvothermal reaction removes residual solvent, unreacted precursors, and weakly adsorbed impurities from the surface of the hydrophobic carbon paper. This prevents these residues from covering active sites, affecting interfacial electron transport, or introducing side reactions during subsequent phytic acid modification or electrocatalytic reactions. Ethanol has good wetting and cleaning capabilities, enabling surface cleaning without significantly damaging the Pd-doped Ag nanoparticle support structure.

[0051] Furthermore, by controlling the drying temperature within the range of 40℃-80℃, residual ethanol and water after washing can be removed under relatively mild conditions, allowing Pd-doped Ag nanoparticles to be stably retained on the surface of the hydrophobic carbon paper. If the drying temperature is too low, insufficient solvent removal may affect the uniformity of subsequent phytic acid modification; if the drying temperature is too high, it may cause changes in the surface state of the hydrophobic carbon paper or local migration and aggregation of nanoparticles. By limiting the drying temperature to 40℃-80℃, sufficient solvent removal, nanoparticle structural stability, and the effectiveness of subsequent phytic acid modification can be balanced.

[0052] This invention also provides a catalyst for the catalytic oxidation of ethylene to ethylene glycol. The catalyst is prepared by any of the methods described above. The catalyst comprises hydrophobic carbon paper and phytic acid-modified Pd-doped Ag nanoparticles grown in situ on the hydrophobic carbon paper. The Pd doping amount in the Pd-doped Ag nanoparticles is any value between 2 wt% and 30 wt%. In this embodiment, the hydrophobic carbon paper, Pd-doped Ag nanoparticles, and phytic acid modification layer together constitute a composite catalytic structure suitable for the electrocatalytic oxidation of ethylene. The hydrophobic carbon paper, as a conductive substrate and gas diffusion support, can improve the transport efficiency of ethylene at the electrode interface and provide a continuous conductive pathway for the catalyst. The in-situ grown Pd-doped Ag nanoparticles, as the main catalytically active component, can provide the active sites required for the ethylene oxidation reaction and optimize the adsorption strength of reaction intermediates through the bimetallic synergistic effect between Pd and Ag. The phytic acid modification layer can regulate the local microenvironment on the catalyst surface, allowing water to participate more effectively as an oxygen source in the ethylene oxidation process, thereby promoting the formation of ethylene glycol.

[0053] In this embodiment, because the Pd-doped Ag nanoparticles are grown in situ on hydrophobic carbon paper, the resulting catalyst differs from conventional powder catalyst coated electrodes. This reduces or eliminates the use of binders, lowering the risk of binders covering active sites and hindering electron transport. Simultaneously, the in-situ growth structure enhances the bonding strength between the catalytically active components and the conductive substrate, enabling the catalyst to maintain good structural and catalytic stability even under continuous ethylene gas flow and constant current electrolysis conditions.

[0054] This invention provides an application of the above-mentioned catalyst in the electrocatalytic oxidation of ethylene to ethylene glycol. The catalyst is used as the working electrode, and water is used as the oxygen source. Ethylene is electrocatalytically oxidized in the presence of an electrolyte to produce ethylene glycol. In this embodiment, by using the above-mentioned phytic acid-modified Pd-doped Ag nanoparticle / hydrophobic carbon paper catalyst as the working electrode and water as the oxygen source in the ethylene electrocatalytic oxidation reaction, the direct conversion of ethylene to ethylene glycol can be achieved under isothermal conditions of ambient temperature and pressure. Compared with the traditional ethylene epoxidation-hydration route, this application method does not require high temperature and high pressure conditions, and avoids the operational complexity and byproduct handling problems caused by the participation of external strong oxidants. It is beneficial to provide a green, safe, and simplified ethylene glycol synthesis route.

[0055] In this embodiment, from a working principle perspective, the hydrophobic carbon paper facilitates the transport of ethylene gas at the gas diffusion electrode interface, Pd-doped Ag nanoparticles provide active sites for ethylene oxidation, and the phytic acid modification layer regulates the interfacial reaction process of water molecules, oxygen-containing intermediates, and ethylene on the catalyst surface, enabling water to participate as an oxygen source in the ethylene glycol formation reaction. The synergistic effect of these multiple components allows the catalyst to simultaneously address ethylene supply, electron transport, water participation in oxidation, and selective ethylene glycol formation in the electrocatalytic system, thereby improving the reaction efficiency of the direct oxidation of ethylene to ethylene glycol.

[0056] In a further embodiment, the electrocatalytic oxidation reaction is carried out in a three-electrode gas diffusion electrode electrolysis system, which includes a working electrode, a silver / silver chloride reference electrode, a Pt-loaded carbon felt counter electrode, and a gas chamber; wherein ethylene gas is continuously introduced into the gas chamber, the electrolyte is a 0.1 mol / L-1.0 mol / L sodium perchlorate solution, and the current density of the constant current electrolysis is 75 mA / cm². 2 -120mA / cm 2 The electrolyte concentration can be any value within the range of 0.1 mol / L, 0.2 mol / L, 0.5 mol / L, 0.8 mol / L, or 1.0 mol / L, or any other value between 0.1 mol / L and 1.0 mol / L; the current density for constant current electrolysis can be 75 mA / cm². 2 80mA / cm 2 90mA / cm 2 100mA / cm 2 110mA / cm 2 Or 120mA / cm 2 It can also be 75mA / cm 2 -120mA / cm 2 Any other value in it.

[0057] In this embodiment, by employing a three-electrode gas diffusion electrode electrolysis system, the reaction potential of the working electrode can be monitored and controlled using a silver / silver chloride reference electrode. A Pt-loaded carbon felt is used to close the electrode circuit, and ethylene gas is continuously supplied to the working electrode interface through a gas chamber, thereby forming a three-phase reaction interface involving the gaseous reactants, electrolyte, and solid catalyst. This system is beneficial for improving the mass transfer efficiency of ethylene to the catalytically active sites, reducing the mass transfer limitation problem of ethylene in the liquid phase, and thus improving the reaction efficiency of the electrocatalytic oxidation of ethylene to ethylene glycol.

[0058] Furthermore, by controlling the concentration of sodium perchlorate solution within the range of 0.1 mol / L to 1.0 mol / L, a suitable ion conduction environment can be provided for the electrocatalytic reaction, reducing the ohmic impedance during electrolysis and maintaining a relatively stable electrolyte environment. When the electrolyte concentration is too low, the ionic conductivity of the system is insufficient, and the electrolytic impedance increases, which is not conducive to the stable operation of constant current electrolysis. When the electrolyte concentration is too high, it may increase the influence of ionic strength on the microenvironment of the catalyst interface reaction and increase the burden on subsequent product separation. By limiting the electrolyte concentration within the above range, electrolytic stability, reaction efficiency, and product system simplicity can be balanced.

[0059] Furthermore, by controlling the current density of constant current electrolysis at 75 mA / cm² 2 -120mA / cm 2 Within this range, the system can undergo ethylene oxidation at relatively high current densities, while avoiding insufficient ethylene glycol formation due to excessively low current densities, or enhanced side reactions, intensified catalyst interfacial polarization, and decreased ethylene glycol selectivity due to excessively high current densities. At 100 mA / cm²... 2 Under the given current density conditions, the ethylene glycol Faraday efficiency can reach 40.8%, and the yield can reach 640 μmol / h, indicating that the catalyst system can achieve efficient and highly selective synthesis of ethylene glycol at a relatively high current density close to the requirements of industrial applications.

[0060] Figure 4 This is a schematic structural diagram of a three-electrode gas diffusion electrode electrolytic cell according to an embodiment of the present invention.

[0061] like Figure 4As shown, the three-electrode gas diffusion electrode electrolysis cell, along the ethylene gas flow direction, sequentially includes a gas flow channel plate 10, a gas diffusion electrode 20, an ion exchange membrane 30, a cathode 40, and a counter-electrode side flow channel plate 50. The gas flow channel plate 10 is disposed on one side of the gas diffusion electrode 20 and has an ethylene glycol outlet 11 and an ethylene inlet 12. The ethylene inlet 12 continuously supplies ethylene gas to the gas diffusion electrode 20, enabling ethylene to reach the catalytic reaction interface. The ethylene glycol outlet 11 is used to remove the ethylene glycol-containing reaction liquid or product generated on the gas diffusion electrode 20 side. The gas diffusion electrode 20 is used to load the catalyst and serve as the working electrode for the electrocatalytic oxidation reaction of ethylene. One side is in contact with the ethylene gas, and the other side is in contact with the electrolyte, thus forming a gas-liquid-solid three-phase reaction interface where the gaseous reactants, electrolyte, and solid catalyst are in contact. The ion exchange membrane 30 is disposed on the gas diffusion electrode... Between electrode 20 and cathode 40, the reaction regions on both sides are isolated and ion migration is allowed to maintain charge balance during electrolysis and reduce cross-diffusion of products or reaction intermediates. Cathode 40 is located on the side of ion exchange membrane 30 away from gas diffusion electrode 20 and is used to cooperate with gas diffusion electrode 20 to form an electrolysis reaction circuit. Counter-electrode side flow channel plate 50 is located on the side of cathode 40 away from ion exchange membrane 30 and is provided with counter-electrode side reactant inlet and counter-electrode side product outlet. It is used to supply electrolyte or reaction medium to cathode 40 and discharge reaction products or electrolyte, thereby ensuring continuous renewal of reaction medium on counter-electrode side and stable operation of electrolysis system.

[0062] The technical solution of this application will be further described below with reference to specific embodiments.

[0063] Example 1

[0064] The catalyst used for the catalytic oxidation of ethylene to ethylene glycol is a PA-Pd / Ag / CP catalyst, and its preparation method is as follows: In step S100, under magnetic stirring, 10 mg of potassium tetrachloropalladate, 100 mg of silver trifluoroacetate, and 90 mg of tungsten hexacarbonyl are dissolved in 6 mL of acetic acid and 24 mL of N,N-dimethylformamide to obtain a mixed system. The mixed system is ultrasonically treated for 30 min to obtain a precursor mixture.

[0065] In step S200, the precursor mixture is transferred to a 50 mL stainless steel autoclave lined with polytetrafluoroethylene. The hydrophobic carbon paper is immersed in the precursor mixture and subjected to a solvothermal reaction at 140°C for 24 h, so that Pd-doped Ag nanoparticles grow in situ on the surface of the hydrophobic carbon paper to obtain the precursor.

[0066] In step S300, the precursor obtained in step S200 is washed multiple times with ethanol and dried at 60°C to obtain hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles, namely Pd / Ag / CP.

[0067] In step S400, 1 mL of 50 wt% phytic acid solution is dissolved in 10 mL of ethanol to form a homogeneous phytic acid solution; the Pd / Ag / CP obtained in step S300 is immersed in the phytic acid solution and allowed to stand at room temperature for 5 h, then rinsed with anhydrous ethanol to remove residual phytic acid, and finally dried to obtain the PA-Pd / Ag / CP catalyst.

[0068] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that potassium tetrachloropalladate is not added in step S100, and silver trifluoroacetate and tungsten hexacarbonyl are dissolved in a mixed solvent of acetic acid and N,N-dimethylformamide.

[0069] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that potassium tetrachloropalladate is replaced with Ru source.

[0070] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that potassium tetrachloropalladium is replaced with a Pt source.

[0071] Figure 5 This is a transmission electron microscope image of the catalyst prepared according to Example 1 of the present invention. Figure 6 This is the X-ray diffraction pattern of the catalyst prepared according to Example 1 of the present invention. Figure 7 This is the X-ray photoelectron spectrum of the catalyst prepared according to Example 1 of the present invention. Figure 8 This is an X-ray elemental distribution diagram of the catalyst prepared according to Example 1 of the present invention. Figure 9 The above is the 1H NMR spectrum of the ethylene glycol electrolyte catalyzed by the catalyst prepared according to Example 1 of the present invention. Figure 10 The NMR 3C spectrum of the ethylene glycol electrolyte catalyzed by the catalyst prepared according to Example 1 of the present invention is shown. Figure 11 These are performance characterization diagrams of the catalysts prepared according to Example 1 and Comparative Examples 1-3 of the present invention.

[0072] First, the PA-Pd / Ag / CP catalyst prepared in Example 1 was characterized by transmission electron microscopy and X-ray diffraction, and the results were as follows: Figure 5 and Figure 6 The test results are shown.

[0073] like Figure 5 and Figure 6As shown, the catalyst prepared in Example 1 exhibits a porous and loose structure formed by the aggregation of nanoparticles. The particle size is at the nanoscale, which is beneficial for exposing more catalytic active sites and increasing the contact opportunities between ethylene, water molecules, and electrolyte on the catalyst surface. The X-ray diffraction pattern shows characteristic diffraction peaks corresponding to the Ag crystal phase, and diffraction signals related to Pd and the carbon substrate can also be observed, indicating that after the solvothermal reaction, Ag-based nanoparticles have been formed on the carbon paper support, and Pd can be introduced into the catalyst system along with the Ag-based nanoparticles. This result demonstrates that this application, through the solvothermal reaction of palladium, silver, and carbonyl metal compounds, can construct Pd-doped Ag nanoparticles on the surface of hydrophobic carbon paper, rather than forming only single metal particles or disordered mixtures, providing a bimetallic synergistic catalytic interface for the subsequent electrocatalytic oxidation of ethylene.

[0074] Secondly, a comparative analysis of P 2p X-ray photoelectron spectroscopy was performed on the PA-Pd / Ag / CP catalyst and the unmodified Pd / Ag / CP catalyst, yielding the following results: Figure 7 The test results are shown.

[0075] like Figure 7 As shown, the PA-Pd / Ag / CP sample exhibits a significant P 2p signal in the P 2p region, with peaks distinguishable as P2p1 / 2 and P 2p3 / 2, while the Pd / Ag / CP sample does not show a significant P 2p signal in the same region. This result indicates that after Pd / Ag / CP is immersed in phytic acid solution and then rinsed and dried, the phosphorus-containing groups in phytic acid can be retained and modified on the surface of Pd-doped Ag nanoparticles. This demonstrates that step S400 is not a simple solution immersion treatment, but rather forms a phytic acid modification layer on the surface of bimetallic nanoparticles. This phytic acid modification layer can regulate the hydrophilicity of the catalyst surface, the local water molecule environment, and the adsorption state of oxygen-containing intermediates through its phosphate groups, thereby facilitating the participation of water as an oxygen source in the electrocatalytic oxidation of ethylene to ethylene glycol.

[0076] Next, the elemental surface distribution of the PA-Pd / Ag / CP catalyst prepared in Example 1 was characterized, and the results were as follows: Figure 8 The test results are shown.

[0077] like Figure 8As shown, both Ag and Pd elements are distributed in the nanoparticle region, indicating that Pd and Ag can coexist within the catalyst active region, supporting the formation of Pd-doped Ag nanoparticles. Simultaneously, P elements also exhibit a relatively obvious distribution in the catalyst particle region, indicating a spatial correspondence between the phytic acid modification layer and the Pd-doped Ag nanoparticles, rather than existing freely outside the catalyst system. This result corroborates the P 2p XPS characterization results, further demonstrating that the catalyst obtained in Example 1 possesses a composite structure of "hydrophobic carbon paper-supported Pd-doped Ag nanoparticles - phytic acid surface modification layer." This structure enables the hydrophobic carbon paper to provide gas diffusion and conductive support, allows the Pd-doped Ag nanoparticles to provide ethylene oxidation active sites, and regulates the reaction interface microenvironment through the phytic acid modification layer, thereby forming a synergistic catalytic effect.

[0078] Next, the reaction solution after the catalytic oxidation of ethylene in Example 1 was analyzed by proton and carbon nuclear magnetic resonance spectroscopy, yielding the following results: Figure 9 and Figure 10 The test results are shown.

[0079] like Figure 9 and Figure 10 As shown, a characteristic signal corresponding to the methylene hydrogen in ethylene glycol appeared in the reaction solution. The carbon NMR spectrum showed a characteristic signal of the -CH2OH carbon in ethylene glycol at approximately 62.68 ppm. These NMR results demonstrate that, under the action of the PA-Pd / Ag / CP catalyst of Example 1, ethylene can be directly oxidized to ethylene glycol in an electrocatalytic system with water as the oxygen source. Combined with the structural characterization results, it can be seen that this application, through the synergistic design of Pd-doped Ag nanoparticles and phytic acid surface modification, not only successfully constructed the target catalyst structure but also achieved the directional conversion of ethylene to ethylene glycol.

[0080] Finally, at 100mA / cm 2 Under constant current density conditions, the catalysts prepared in Example 1 and Comparative Examples 1-3 were tested for their performance in the electrocatalytic oxidation of ethylene to ethylene glycol, and the results were as follows: Figure 11 The test results are shown.

[0081] like Figure 11 As shown, at 100 mA / cm 2Under constant current density conditions, the ethylene glycol Faradaic efficiency of Example 1 was the highest, approximately 17%–18%; Comparative Example 1 was approximately 10%; Comparative Example 2 was approximately 3%–4%; and Comparative Example 3 was approximately 4%–5%. Therefore, the Faradaic efficiency of Example 1 was significantly higher than that of Comparative Example 1 without Pd, and also significantly higher than that of Comparative Examples 2 and 3, which used Ru or Pt to replace Pd. This result indicates that while Ag-based catalysts alone can catalyze the oxidation of ethylene to ethylene glycol, their selectivity is limited. Introducing Pd into Ag-based nanoparticles can significantly improve the current utilization efficiency for ethylene glycol generation. Meanwhile, replacing Pd with Ru or Pt did not bring the same improvement; instead, it reduced the Faradaic efficiency, indicating that not all noble metal doping with Ag can improve ethylene glycol selectivity. Pd has a more suitable role in regulating the electronic structure and intermediate adsorption of Ag-based catalysts for this reaction.

[0082] In summary, this application improves the selectivity and current utilization efficiency of ethylene to ethylene glycol conversion through a synergistic design that combines hydrophobic carbon paper gas diffusion support, Pd-doped Ag bimetallic active sites, and phytic acid surface microenvironment regulation.

[0083] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0084] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a catalyst for the catalytic oxidation of ethylene to ethylene glycol, characterized in that, Includes the following steps: Palladium source, silver source and carbonyl metal compound were dissolved in a mixed solvent containing acetic acid and N,N-dimethylformamide to obtain a precursor mixture; The hydrophobic carbon paper is placed in the precursor mixture and subjected to a solvothermal reaction, so that Pd-doped Ag nanoparticles are grown in situ on the hydrophobic carbon paper to obtain hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles. The hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles was immersed in a phytic acid solution to modify the surface of the Pd-doped Ag nanoparticles with phytic acid, thereby obtaining a catalyst for catalyzing the oxidation of ethylene to ethylene glycol.

2. The method for preparing the catalyst for catalytic oxidation of ethylene to ethylene glycol according to claim 1, characterized in that, The hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles is soaked in the phytic acid solution for any value between 1 h and 7 h.

3. The method for preparing the catalyst for catalytic oxidation of ethylene to ethylene glycol according to claim 2, characterized in that, The Pd doping amount in the Pd-doped Ag nanoparticles is any value between 2wt% and 30wt%.

4. The method for preparing the catalyst for catalytic oxidation of ethylene to ethylene glycol according to claim 3, characterized in that, The temperature of the solvothermal reaction is any value between 120℃ and 160℃, and the reaction time is any value between 12h and 36h.

5. The method for preparing the catalyst for catalytic oxidation of ethylene to ethylene glycol according to claim 4, characterized in that, The palladium source includes potassium tetrachloropalladate, palladium chloride, and palladium acetylacetonate; the silver source includes silver trifluoroacetate, silver nitrate, and silver chloride; and the carbonyl metal compound includes tungsten hexacarbonyl and nickel tetracarbonyl.

6. The method for preparing the catalyst for catalytic oxidation of ethylene to ethylene glycol according to claim 5, characterized in that, Before obtaining the precursor mixture, the mixture containing the palladium source, the silver source, the carbonyl metal compound, and the mixed solvent is subjected to ultrasonic treatment; wherein, The duration of the ultrasonic treatment is any value between 20 min and 60 min.

7. The method for preparing the catalyst for the catalytic oxidation of ethylene to ethylene glycol according to any one of claims 1-6, characterized in that, Also includes: After the solvothermal reaction, the reaction product is washed and dried to obtain the hydrophobic carbon paper loaded with Pd-doped Ag nanoparticles. The washing process uses ethanol, and the drying process is carried out at any temperature between 40°C and 80°C.

8. A catalyst for catalytic oxidation of ethylene to ethylene glycol, characterized in that, The catalyst is prepared by the preparation method according to any one of claims 1-7; The catalyst comprises hydrophobic carbon paper and phytic acid-modified Pd-doped Ag nanoparticles grown in situ on the hydrophobic carbon paper, wherein the doping amount of Pd in ​​the Pd-doped Ag nanoparticles is any value between 2wt% and 30wt%.

9. The application of the catalyst according to claim 8 in the electrocatalytic oxidation of ethylene to ethylene glycol, characterized in that, Using the catalyst as the working electrode and water as the oxygen source, ethylene is electrocatalytically oxidized in the presence of an electrolyte to produce ethylene glycol.

10. The application of the catalyst according to claim 9 in the electrocatalytic oxidation of ethylene to ethylene glycol, characterized in that, The electrocatalytic oxidation reaction is carried out in a three-electrode gas diffusion electrode electrolysis system, which includes the working electrode, a silver / silver chloride reference electrode, a Pt-loaded carbon felt counter electrode, and a gas chamber; wherein... Ethylene gas is continuously introduced into the gas chamber, the electrolyte is a 0.1 mol / L-1.0 mol / L sodium perchlorate solution, and the current density for constant current electrolysis is 75 mA / cm². 2 -120mA / cm 2 Any value among them.

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