Polyol oxidation alternating current electrolysis method, membraneless electrolysis device and large-scale electrolysis system

Abstract

The application discloses a polyhydric alcohol oxidation alternating current electrolysis method, a membrane-free electrolysis device and a large-scale electrolysis system, and belongs to the technical field of new energy chemical industry. In order to solve the problems of the poisoning of the noble metal catalyst in the traditional electrocatalytic polyhydric alcohol technology, and the high energy loss and high construction and operation cost of the traditional direct current power supply mode, the application uses a noble metal-based catalyst as a working electrode in an electrolysis system, uses polyhydric alcohol and an aqueous electrolyte as working electrode substrates, applies alternating current between the working electrode and a counter electrode, and generates high-value-added products and hydrogen through electrocatalysis. A membrane-free electrolysis device and a large-scale electrolysis system are designed for the alternating current electrolysis process. The device and the system can realize high current density, super-long stability and efficient production, greatly reduce the cost and reaction energy consumption, improve the production efficiency and economy, and are expected to be applied to actual production.

Description

Technical Field

[0001] This invention belongs to the field of new energy chemical technology, specifically relating to a polyol oxidation AC electrolysis method, a membrane-free electrolysis device, and a large-scale electrolysis system. Background Technology

[0002] Polyols (such as ethylene glycol, glycerol, and sorbitol) serve as important platform molecules for biomass conversion. They are widely derived from the hydrolysis of vegetable oils, catalytic hydrogenation of sugars, or the depolymerization of waste plastics. They are relatively inexpensive and possess advantages in terms of renewability and structural diversity. Converting these polyols from biomass and waste plastics into higher value-added products is an economically viable application. However, traditional thermocatalytic conversion technologies suffer from high energy consumption, low product selectivity, and easy catalyst deactivation. For example, while high-temperature gasification of biomass can produce hydrogen and carbon monoxide, it produces a large amount of carbon dioxide as a byproduct and requires temperatures of 700℃ to 1000℃, limiting its economic viability. Given the dependence of traditional chemical production on fossil resources and the urgent need for efficient utilization of biomass resources, developing a sustainable high-value-added conversion pathway for polyols is of great significance.

[0003] Electrochemical conversion pathways driven by renewable energy sources such as solar and wind power offer a mild, green, and sustainable approach. Electrochemical oxidation methods can be used to achieve high-value-added conversion of polyols. Specifically, by controlling electrode potential and catalyst design, highly selective synthesis of C / C bond breaking, hydroxyl oxidation, and functionalized products can be achieved under mild conditions (room temperature and pressure). Therefore, the efficient conversion of polyols (such as ethylene glycol and glycerol) into high-value-added chemicals (such as glycolic acid and glyceric acid) via electrochemical oxidation, coupled with the co-production of green hydrogen at the cathode, provides a new approach for the efficient utilization of excess polyols. Electrochemical methods can fully utilize clean electricity generated from sustainable energy sources such as wind and solar power, achieving effective absorption of clean electricity and reducing phenomena such as "wind curtailment" and "solar curtailment." Furthermore, electrochemical methods can also be used to produce hydrogen through water electrolysis at the cathode coupled with anode alcohol oxidation. Hydrogen energy has advantages such as high energy density and clean, pollution-free combustion (the combustion product is water), aligning with the development trend of clean hydrogen production from renewable energy under the "dual carbon" target. Replacing the high-potential oxygen evolution reaction (compared to 1.23 volts at the standard hydrogen electrode) in traditional water electrolysis for hydrogen production with the electrooxidation of polyols helps reduce energy consumption and improve economic efficiency. Furthermore, this method avoids the risk of explosion from a hydrogen-oxygen mixture, enhancing the safety of hydrogen production. In summary, polyol electrooxidation coupled with cathode co-production of green hydrogen is a highly promising method that aligns with the current trend of developing clean energy technologies and transforming the energy structure.

[0004] Noble metal catalysts, such as palladium, platinum, and gold, can suppress the breaking of C-C bonds and increase the added value of products in the electro-oxidation of basic polyols. However, oxidation on the surface of the noble metal and adsorption of carbonyl intermediates during this process can lead to catalyst passivation, a significant decrease in activity, and consequently, reduced yield and increased energy consumption. To address this issue, previous researchers have mainly focused on controlling the catalyst's resistance to poisoning through methods such as inert metal doping, support loading, and morphology control. However, catalyst poisoning cannot be completely avoided; during long-term electrolysis, the current gradually decreases over time, leading to a significant drop in production efficiency.

[0005] From the perspective of power supply, traditional electrocatalytic reactions rely on DC power to construct a stable electrode / solution interface double layer to achieve continuous adsorption and activation of reactants on the electrode surface. However, the total life cycle cost of DC power supply systems includes multiple hidden expenditures: (1) Rectification loss: AC power output from industrial power grids needs to be processed into DC power by AC / DC conversion devices, with a typical conversion efficiency of 90%~95%, resulting in 5%~10% energy loss; (2) Equipment maintenance cost: High-power DC power supplies need to be equipped with filter circuits to suppress ripple, and their capacitors and inductors are at risk of aging during long-term operation; (3) Infrastructure investment: High-purity DC power supplies (such as photovoltaic direct power supply systems) need to be equipped with energy storage devices to smooth out fluctuations, which will significantly increase the initial construction cost. Taking the chlor-alkali industry as an example, DC power consumption accounts for more than 60% of the total production cost, of which the rectification loss accounts for 8%~12%.

[0006] Therefore, there is an urgent need for a novel strategy for electrocatalyzing polyols that can reduce multiple hidden costs under traditional DC power supply while improving the poisoning problem of precious metal catalysts.

[0007] In typical membrane electrode electrochemical electrolysis systems, the membrane not only performs product separation and ion conduction functions, but also plays a crucial role in regulating the system's water content, interfacial electric field, and reaction microenvironment. Although proton exchange membranes and anion exchange membranes are widely used in systems such as water electrolysis, they still face significant challenges in complex reaction systems such as polyol electrooxidation. On the one hand, the reaction medium can easily cause a decrease in membrane ionic conductivity, increasing the risk of membrane fouling and failure. On the other hand, membrane fouling not only stems from physical blockage by reactants and intermediates, but also from chemical degradation initiated by nucleophilic / oxidizing components, directly leading to increased cell voltage, reduced product selectivity, and decreased device lifespan. Especially in electrolytes containing organic substrates and redox active components, membrane materials are more prone to interfacial interactions, fouling, and even degradation, further weakening the system's stability and selectivity.

[0008] From an engineering and commercial perspective, the core of implementing electrocatalysis technology lies in achieving large-scale scaling, improving operational reliability, and efficiently integrating with existing industrial processes. Reactor design must prioritize economic efficiency and stability, relying on large-scale flow systems and high specific surface area electrodes to support industrial-scale operation. Against this backdrop, simplifying reactor structure and developing membrane-free electrolysis technology hold promise for fundamentally avoiding membrane fouling, degradation, and cost issues, becoming a key technological path to reduce system energy consumption, improve operational stability, and cut overall production costs. Summary of the Invention

[0009] To address the problems of catalyst poisoning and deactivation, poor product selectivity, multiple hidden costs associated with DC power supply, membrane fouling, membrane degradation, and membrane costs in traditional DC electrolysis, this invention provides an AC electrolysis method for polyol oxidation, a membrane-free electrolysis device, and a large-scale electrolysis system. By directly utilizing AC power from the power grid for electrolysis, and by controlling the peak current, potential, and frequency of the AC power, poisonous species on the catalyst surface can be eliminated in situ, significantly maintaining catalytic activity. Combined with the membrane-free electrolysis device and a large-scale integrated system, it achieves highly selective anode production of carboxylic acids and co-production of high-purity hydrogen at the cathode. It has advantages such as high efficiency, good stability, long operating life, and low energy consumption, and has good prospects for industrial application.

[0010] The technical solution adopted in this invention is as follows:

[0011] The polyol oxidation AC electrolysis method uses a noble metal-based catalyst as the working electrode and a polyol and an aqueous electrolyte as the working electrode substrate in the electrolysis system. By applying an alternating current between the working electrode and the counter electrode, high-value-added products and hydrogen are electrocatalyzed.

[0012] Furthermore, the high-value-added product is a carboxylic acid.

[0013] Furthermore, by changing the pulse frequency of the alternating current, the electrocatalytic oxidation performance of polyols can be controlled, specifically achieving the regulation of current density.

[0014] Furthermore, the pulse frequency of the alternating current is 0.00001 Hz to 500 Hz, the pulse current is 0.001 ampere to 1000 ampere, and the pulse voltage is 0.6 volt to 660 volt.

[0015] Furthermore, the input waveform of the alternating current is at least one of square wave, sine wave, triangular wave, sawtooth wave, and step wave, and the stability of electrocatalytic oxidation can be controlled by changing the input waveform of the alternating current.

[0016] Furthermore, the polyol is ethylene glycol, glycerol, or 1,2-propanediol.

[0017] Furthermore, the concentration of the polyol in the working electrode substrate is 0.001 mol / L to 5 mol / L.

[0018] Furthermore, the precious metal-based catalyst is a precious metal sheet, a precious metal mesh, or a precious metal powder supported catalyst, wherein the precious metal is at least one of palladium, platinum, gold, and silver, and the substrate of the precious metal powder supported catalyst is at least one of carbon paper, carbon cloth, carbon felt, nickel foam, and titanium felt.

[0019] Furthermore, the noble metal supported catalyst is prepared by at least one of electroplating, vapor deposition, and impregnation methods.

[0020] Furthermore, the cut size of the noble metal-based catalyst is 1 cm × 1 cm to 100 cm × 100 cm.

[0021] Further, the aqueous electrolyte is at least one of potassium hydroxide solution, sodium hydroxide solution, lithium hydroxide solution, potassium carbonate solution, sodium carbonate solution, sodium perchlorate solution, potassium sulfate solution, perchloric acid solution, and sulfuric acid solution.

[0022] Further, the concentrations of the potassium hydroxide solution, sodium hydroxide solution, lithium hydroxide solution, and potassium carbonate solution are 0.1 mol / L to 5 mol / L; the concentration of the sodium carbonate solution is 0.1 mol / L to 2 mol / L; the concentration of the sodium perchlorate solution is 0.1 mol / L to 3 mol / L; and the concentrations of the potassium sulfate solution, perchloric acid solution, and sulfuric acid solution are 0.1 mol / L to 0.5 mol / L.

[0023] Furthermore, the electrolyte for the counter electrode in the electrolysis system can be the same as or different from the aqueous electrolyte.

[0024] Furthermore, the electrolysis system is a two-electrode system or a three-electrode system, and its reaction device includes, but is not limited to, an H-type electrolytic cell, a flow electrolytic cell, or a membrane electrode electrolytic cell.

[0025] Furthermore, the reference electrode in the electrolysis system is a mercury / mercury oxide electrode, a silver / silver chloride electrode, or a saturated calomel electrode.

[0026] A membrane-free electrolysis device for polyol oxidation includes a left end plate, several electrolysis units, and a right end plate stacked sequentially, with intermediate partitions between adjacent electrolysis units. The electrolysis units are connected in series. Each electrolysis unit consists of a first catalyst, a first gasket, an intermediate layer, a second gasket, and a second catalyst stacked sequentially. The intermediate partition and the first, intermediate, and second gaskets of each electrolysis unit have hollow areas with the same cross-sectional size. Both the first and second catalysts are noble metal-based catalysts, which alternately serve as the working electrode (anode) and the counter electrode (cathode), and their coverage area in the hollow areas is 30%–70%. The electrolyte of the electrolysis unit consists of polyol and an aqueous electrolyte. Alternating current is applied between the working electrode and the counter electrode via leads to electrocatalytically generate high-value-added products and hydrogen.

[0027] Furthermore, the left and right end plates have grooves with the same cross-sectional dimensions as the hollowed-out area on the side facing the electrolysis unit, which together with the hollowed-out area form an electrolysis chamber inside the polyol oxidation membraneless electrolysis device.

[0028] Furthermore, the first catalyst and the second catalyst are located at the lower part of the hollowed-out area, so that the upper part of the electrolysis chamber is connected to the hydrogen produced by the reaction.

[0029] Furthermore, the left end plate is also provided with a liquid inlet, which is located below the left end plate.

[0030] Furthermore, the right end plate is also provided with a liquid outlet, which is located above the right end plate.

[0031] Furthermore, the thickness of the intermediate partition layer is greater than that of the intermediate layer.

[0032] Furthermore, the thickness of the intermediate septum ranges from 5 mm to 20 mm.

[0033] Furthermore, the thickness of the intermediate layer ranges from 3 mm to 10 mm.

[0034] Furthermore, the materials of the left end plate, the middle partition layer, the right end plate, and the first gasket, the middle layer, and the second gasket of the electrolysis unit are all non-metallic materials, specifically polymethyl methacrylate, polyether ether ketone, polytetrafluoroethylene, polypropylene, phenolic plastic, silicone rubber, or fluororubber.

[0035] Furthermore, the left end plate, the middle partition layer, the right end plate, and the first gasket, the middle layer, and the second gasket of the electrolysis unit are all provided with several threaded holes for assembly and fixation.

[0036] A large-scale electrolysis system for polyol oxidation has the same structure as the membraneless electrolysis device for polyol oxidation, wherein the coverage area of ​​the first catalyst and the second catalyst is not less than 0.3 square centimeters.

[0037] The present invention also proposes a polyol oxidation membraneless electrolysis device adapted to public power grids, which has the same structure as the polyol oxidation membraneless electrolysis device, wherein an alternating current with a sine wave is applied between the working electrode and the counter electrode.

[0038] A large-scale electrolytic system for polyol oxidation adapted to public power grids has the same structure as the aforementioned large-scale electrolytic system for polyol oxidation, wherein an alternating current with a sinusoidal waveform is applied between the working electrode and the counter electrode.

[0039] Furthermore, by adjusting the number of stacked electrolysis units, the total electrolysis voltage of the polyol oxidation membraneless electrolysis device adapted to the public power grid and the polyol oxidation large-scale electrolysis system adapted to the public power grid is matched with the amplitude of the AC power supply voltage of the public power grid, thereby eliminating the need to use a step-down transformer or step-down conversion circuit.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. The polyol oxidation AC electrolysis method proposed in this invention achieves rapid periodic switching of positive and negative polarity by applying AC current, avoiding the problem of decreased production efficiency during long-term single-working-electrode electrolysis, effectively maintaining catalyst activity, inhibiting C-C bond breakage, and thus effectively removing poisoning. AC electrolysis can also reduce activation overpotential through relaxation effect, inhibit bubble accumulation on electrode surface, increase effective reaction area, and thus achieve long-term stable production under high current density, thereby improving the yield of high-value-added carboxylic acids and co-producing green hydrogen. It has the advantages of simple method, low cost, and easy industrialization.

[0042] 2. Compared with common strategies, this invention has no special requirements for the preparation process of the catalyst, is applicable to most precious metal-based catalysts, and has significant effects; this invention can not only stably produce high value-added carboxylic acids, but also produce hydrogen more efficiently and stably, and has a high cost performance.

[0043] 3. The polyol oxidation membrane-free electrolysis device and polyol oxidation large-scale electrolysis system proposed in this invention, for AC electrolysis methods, improve the catalyst (i.e., electrode) structure of the device and system. Specifically, the coverage area of ​​the electrolysis chamber window is adjusted from the traditional full coverage to 30%–70% coverage, and the gaps are preferentially set above the electrolysis chamber window. This design has multiple functions: on the one hand, the gaps facilitate the rapid escape of gaseous (hydrogen) products, shorten the residence time of bubbles on the electrode surface, thereby enhancing the liquid phase mass transfer process and improving the production efficiency and large-scale production limit of the device and system; on the other hand, the gaps connect the series-connected electrolysis unit chambers, allowing free flow of gas and electrolyte between chambers. When a local electrolysis unit chamber experiences a sudden increase in gas / hydraulic pressure due to fluctuations in gas production rate or external disturbances, the excess pressure can be quickly diffused to adjacent electrolysis unit chambers through the gaps, avoiding a sharp increase in pressure within a single electrolysis unit chamber. Meanwhile, the interconnected structure, similar to communicating vessels, allows the electrolyte to dynamically migrate between different electrolysis unit chambers, buffering pressure shocks and suppressing the cascading amplification effect of pressure fluctuations. This enhances the system's tolerance to disturbances and ensures long-term safe and stable production. Furthermore, since the electrodes do not fully cover the electrolysis chamber windows, the electrolysis units can be flexibly stacked and connected in series through gaps. The number of electrolysis units can be flexibly expanded according to actual production needs without redesigning the electrode structure of individual electrolysis unit chambers. This stackability allows the device and system to directly match the AC voltage amplitude of the public power grid by increasing the number of series units—for example, by stacking an appropriate number of electrolysis units, the total electrolysis voltage of the system can be matched with the grid supply voltage. This eliminates the need for step-down transformers or step-down conversion circuits, avoiding iron losses, copper losses, and switching losses generated during the step-down process. This reduces energy loss, lowers equipment costs and system complexity, and further enhances the convenience and economy of directly coupling this electrolysis system with the public power grid.

[0044] 4. This invention also proposes a membrane-free electrolysis device and a large-scale electrolysis system for polyol oxidation adapted to public power grids. It uses sinusoidal alternating current for electrolysis, eliminating the need for current waveform rectification or shaping, thus avoiding energy losses associated with waveform shaping. Specifically, traditional electrolysis systems often require converting alternating current to direct current, or sinusoidal alternating current to square waves or pulse waves. During this process, significant energy losses occur due to the on-state voltage drop of rectifier devices, switching losses, and heat dissipation of filter resistors. Furthermore, if the waveform does not match the electrode reaction kinetics (e.g., a square wave causes a sharp change in current, easily leading to electrode surface passivation, exacerbated side reactions, and reduced current efficiency), the overall efficiency of the electrolysis process will be further weakened. This invention can directly adapt to the standard sinusoidal alternating current of public power grids, simplifying the power supply chain and improving energy utilization efficiency.

[0045] 5. From an environmentally friendly perspective, this invention not only provides an effective technical solution to the problem of excess polyols, but is also applicable to many scenarios such as plastic recycling, organic synthesis, and industrial hydrogen production, and has high economic benefits. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 A scanning electron microscope image of the noble metal-based catalyst prepared in Example 1;

[0048] Figure 2 This is a schematic diagram of the square wave waveform used in Example 1;

[0049] Figure 3 This is a comparison chart of time-current curves obtained using square wave AC voltage and constant voltage power supply in Example 1, respectively;

[0050] Figure 4 The Faraday efficiency of each product in the anode of the ethylene glycol AC electrolysis system in Example 1;

[0051] Figure 5 The Faraday efficiency of hydrogen in the cathode of the ethylene glycol AC electrolysis system in Example 1;

[0052] Figure 6 The potential-current curves of the ethylene glycol AC electrolysis system in Example 2 at different pulse frequencies are shown.

[0053] Figure 7 This is a graph showing the electro-oxidation stability of the catalyst in the ethylene glycol AC electrolysis system based on square waves in Example 3.

[0054] Figure 8 The graph shows the electro-oxidation stability of the catalyst in the ethylene glycol DC electrolysis system of Example 3.

[0055] Figure 9 This is a schematic diagram of the polyol oxidation membrane-free electrolysis device proposed in Example 4;

[0056] Figure 10 This is a schematic diagram of the structure of the left end plate in Example 4;

[0057] Figure 11 This is a schematic diagram of the right end plate in Example 4;

[0058] Figure 12This is a schematic diagram of the intermediate septum fault in Example 4;

[0059] Figure 13 This is a schematic diagram of the structure of the first gasket in Example 4;

[0060] Figure 14 This is a schematic diagram of the intermediate layer in Example 4;

[0061] Figure 15 This is a comparison of the electrolytic stability performance of the square wave-based AC electrolysis system and the DC electrolysis system of ethylene glycol in Example 5 on a 5 square centimeter polyol oxidation membrane-free electrolysis device.

[0062] Figure 16 This is a schematic diagram of the sine wave waveform used in Example 6;

[0063] Figure 17 This is a graph showing the electrolytic stability of the ethylene glycol AC electrolysis system based on square waves in Example 6 in a 25 square centimeter polyol oxidation membrane-free electrolysis device;

[0064] Figure 18 This is a graph showing the electrolytic stability of the ethylene glycol AC electrolysis system based on a sine wave in Example 6 in a 25 cm² polyol oxidation membrane-free electrolysis device.

[0065] Figure 19 This is a graph showing the electrolytic stability of the ethylene glycol AC electrolysis system based on a sine wave in Example 7 on a 425 square centimeter-scale polyol oxidation electrolysis system.

[0066] Figure 20 The curve showing the change in glycolic acid production rate over time in the ethylene glycol AC electrolysis system based on a sine wave in Example 7, within a 425 cm² polyol oxidation scale-up electrolysis system;

[0067] Figure 21 This is a graph showing the electrolytic stability of the ethylene glycol AC electrolysis system based on a sine wave in Example 8 on a 50 square centimeter scale-up polyol oxidation electrolysis system adapted to a public power grid.

[0068] Figure 22 The graph shows the electrolytic stability of the glycerol AC electrolysis system based on a sine wave in Example 9 in a 5 cm² polyol oxidation membrane-free electrolysis device.

[0069] Figure 23 The graph shows the electrolytic stability of the 1,2-propanediol AC electrolysis system based on a sine wave in Example 10 in a 5 cm² polyol oxidation membrane-free electrolysis device.

[0070] Figure 24 This is a schematic diagram of the direct grid-driven polyol electro-oxidation production system in Example 8;

[0071] The markings in the attached diagram have the following meanings:

[0072] 1. Left end plate; 2. Electrolysis unit; 3. Middle partition layer; 4. Right end plate; 5. First catalyst; 6. First gasket; 7. Intermediate layer; 8. Second gasket; 9. Second catalyst; 10. Lead wire; 11. Threaded hole in left end plate; 12. Liquid inlet in left end plate; 13. Chamber in left end plate; 31. Threaded hole in middle partition layer; 32. Chamber in middle partition layer; 41. Threaded hole in right end plate; 42. Liquid outlet in right end plate; 43. Chamber in right end plate; 61. Threaded hole in gasket; 62. Gasket chamber; 71. Threaded hole in intermediate layer; 72. Chamber in intermediate layer. Detailed Implementation

[0073] This invention provides a polyol oxidation AC electrolysis method. In the electrolysis system, a noble metal-based catalyst is used as the working electrode, and the polyol and aqueous electrolyte are used as the working electrode substrate. By applying AC current between the working electrode and the counter electrode, high value-added products and hydrogen are electrocatalyzed.

[0074] Furthermore, the high-value-added product is a carboxylic acid.

[0075] Furthermore, by changing the pulse frequency of the alternating current, the electrocatalytic oxidation performance of polyols can be controlled, specifically achieving the regulation of current density.

[0076] Further, the pulse frequency of the alternating current is 0.00001 Hz to 500 Hz, the pulse current is 0.001 amperes to 1000 amperes, and the pulse voltage is 0.6 volts to 660 volts. Preferably, the pulse frequency of the alternating current is 0.05 Hz to 10 Hz, the pulse current is 0.05 amperes to 170 amperes, and the pulse voltage is 0.6 volts to 50 volts.

[0077] Furthermore, the input waveform of the alternating current is at least one of square wave, sine wave, triangular wave, sawtooth wave, and step wave, and the stability of electrocatalytic oxidation can be controlled by changing the input waveform of the alternating current. Preferably, the input waveform of the alternating current is a square wave or a sine wave.

[0078] Furthermore, the polyol is ethylene glycol, glycerol, or 1,2-propanediol.

[0079] Further, the concentration of the polyol in the working electrode substrate is 0.001 mol / L to 5 mol / L. Preferably, the concentration of the polyol in the working electrode substrate is 0.05 mol / L to 1 mol / L.

[0080] Furthermore, the metal-based catalyst is a metal sheet, a metal mesh, or a metal-supported catalyst, and the precious metal is at least one of palladium, platinum, gold, and silver. The catalyst substrate is at least one of carbon paper, carbon cloth, carbon felt, nickel foam, and titanium felt. Preferably, the precious metal is gold, and the catalyst substrate is carbon paper.

[0081] Furthermore, the noble metal supported catalyst is prepared by at least one of electroplating, vapor deposition, and impregnation methods.

[0082] Furthermore, the cut size of the noble metal-based catalyst is from 1 cm × 1 cm to 100 cm × 100 cm. Preferably, the cut size is from 1 cm × 1 cm to 3 cm × 3 cm.

[0083] Further, the aqueous electrolyte is at least one selected from potassium hydroxide solution, sodium hydroxide solution, lithium hydroxide solution, potassium carbonate solution, sodium carbonate solution, sodium perchlorate solution, potassium sulfate solution, perchloric acid solution, and sulfuric acid solution. Preferably, the aqueous electrolyte is potassium hydroxide solution.

[0084] Further, the concentrations of potassium hydroxide, sodium hydroxide, lithium hydroxide, and potassium carbonate are 0.1 mol / L to 5 mol / L; the concentration of sodium carbonate is 0.1 mol / L to 2 mol / L; the concentration of sodium perchlorate is 0.1 mol / L to 3 mol / L; and the concentrations of potassium sulfate, perchloric acid, and sulfuric acid are 0.1 mol / L to 0.5 mol / L. Preferably, the concentration of the potassium hydroxide solution is 0.5 mol / L to 3 mol / L.

[0085] Furthermore, the electrolyte for the counter electrode in the electrolysis system can be the same as or different from the aqueous electrolyte.

[0086] Furthermore, the electrolysis system is a two-electrode system or a three-electrode system, and its reaction device includes, but is not limited to, an H-type electrolytic cell, a flow electrolytic cell, or a membrane electrode electrolytic cell.

[0087] Furthermore, the reference electrode in the electrolysis system is a mercury / mercury oxide electrode, a silver / silver chloride electrode, or a saturated calomel electrode.

[0088] A membrane-free electrolysis device for polyol oxidation includes a left end plate, several electrolysis units, and a right end plate stacked sequentially, with intermediate partitions between adjacent electrolysis units. The electrolysis units are connected in series. Each electrolysis unit consists of a first catalyst, a first gasket, an intermediate layer, a second gasket, and a second catalyst stacked sequentially. The intermediate partition and the first, intermediate, and second gaskets of each electrolysis unit have hollow areas with the same cross-sectional size. Both the first and second catalysts are noble metal-based catalysts, which alternately serve as the working electrode (anode) and the counter electrode (cathode), and their coverage area in the hollow areas is 30%–70%. The electrolyte of the electrolysis unit consists of polyol and an aqueous electrolyte. Alternating current is applied between the working electrode and the counter electrode via leads to electrocatalytically generate high-value-added products and hydrogen.

[0089] Furthermore, the left and right end plates have grooves with the same cross-sectional dimensions as the hollowed-out area on the side facing the electrolysis unit, which together with the hollowed-out area form an electrolysis chamber inside the polyol oxidation membraneless electrolysis device.

[0090] Furthermore, the first catalyst and the second catalyst are located at the lower part of the hollowed-out area, so that the upper part of the electrolysis chamber is connected to the hydrogen produced by the reaction.

[0091] Furthermore, the left end plate is also provided with a liquid inlet, which is located below the left end plate.

[0092] Furthermore, the right end plate is also provided with a liquid outlet, which is located above the right end plate.

[0093] Furthermore, the thickness of the intermediate partition layer is greater than that of the intermediate layer.

[0094] Furthermore, the thickness of the intermediate septum ranges from 5 mm to 20 mm.

[0095] Furthermore, the thickness of the intermediate layer ranges from 3 mm to 10 mm.

[0096] Furthermore, the materials of the left end plate, the middle partition layer, the right end plate, and the first gasket, the middle layer, and the second gasket of the electrolysis unit are all non-metallic materials, specifically polymethyl methacrylate, polyether ether ketone, polytetrafluoroethylene, polypropylene, phenolic plastic, silicone rubber, or fluororubber.

[0097] Furthermore, the left end plate, the middle partition layer, the right end plate, and the first gasket, the middle layer, and the second gasket of the electrolysis unit are all provided with several threaded holes for assembly and fixation.

[0098] A large-scale electrolysis system for polyol oxidation has the same structure as the membraneless electrolysis device for polyol oxidation, wherein the coverage area of ​​the first catalyst and the second catalyst is not less than 0.3 square centimeters.

[0099] The present invention also proposes a polyol oxidation membraneless electrolysis device adapted to public power grids, which has the same structure as the polyol oxidation membraneless electrolysis device, wherein an alternating current with a sine wave is applied between the working electrode and the counter electrode.

[0100] A large-scale electrolytic system for polyol oxidation adapted to public power grids has the same structure as the aforementioned large-scale electrolytic system for polyol oxidation, wherein an alternating current with a sinusoidal waveform is applied between the working electrode and the counter electrode.

[0101] Furthermore, by adjusting the number of stacked electrolysis units, the total electrolysis voltage of the polyol oxidation membraneless electrolysis device adapted to the public power grid and the polyol oxidation large-scale electrolysis system adapted to the public power grid is matched with the amplitude of the AC power supply voltage of the public power grid, thereby eliminating the need to use a step-down transformer or step-down conversion circuit.

[0102] To further illustrate the present invention, the following detailed description, in conjunction with embodiments and accompanying drawings, describes the polyol oxidation AC electrolysis method, membrane-free electrolysis device, and large-scale electrolysis system provided by the present invention. However, this should not be considered limiting. The embodiments mentioned below are partial examples based on the technical solution of the present invention, and not all examples. These descriptions provide detailed implementation methods and specific operating procedures, and are only for further illustrating the features and advantages of the present invention, and are not intended to limit the present invention.

[0103] Unless otherwise specified, the raw materials used in the examples of this invention are all commercially available or prepared using conventional methods known to those skilled in the art; unless otherwise specified, the instruments, equipment and methods used in the examples of this invention are all conventionally mastered in the art.

[0104] Example 1

[0105] This embodiment proposes an alternating current electrolysis method for the oxidation of polyols. In the electrolysis system, a gold-supported catalyst is used as the working electrode, and ethylene glycol and potassium hydroxide solution are used as the working electrode substrates. By applying alternating current between the working electrode and the counter electrode, high-value-added products and hydrogen are generated electrocatalystly.

[0106] The preparation method of the gold-supported catalyst includes the following steps:

[0107] Step 1: Cut the raw carbon paper into 3 cm x 3 cm pieces, rinse it briefly with deionized water to remove surface impurities, and then dry it;

[0108] Step 2: Place the raw carbon paper obtained in Step 1 at the cathode of a single-cell electrolytic cell. The cathode electrolyte consists of 3 mol / L sulfuric acid and 10 mmol / L chloroauric acid. Using a graphite electrode as the counter electrode, electrodeposit for 120 seconds at a current density of -500 mA / cm² to obtain the following result. Figure 1The gold-supported catalyst shown;

[0109] Step 3: Cut the gold-supported catalyst obtained in Step 2 into 1 cm × 2 cm pieces to serve as the working electrode.

[0110] The testing environment in this embodiment is as follows: an H-type electrolytic cell is used as the electrolytic reaction device, with a graphite sheet as the counter electrode, mercury / mercury oxide as the reference electrode, and a bipolar membrane as the diaphragm. Specifically, the working electrode is immersed in a solution of 0.3 mol / L ethylene glycol and 1 mol / L potassium hydroxide, with an immersion area of ​​1 cm × 1 cm; the counter electrode is immersed in a solution of 0.5 mol / L sulfuric acid, with an immersion area of ​​1 cm × 1 cm.

[0111] Adopting such Figure 2 The square wave waveform shown was used for AC electrolytic catalytic performance testing. The parameters are as follows: the anode currents are 50 mA, 100 mA, 150 mA, 200 mA, 300 mA, 400 mA, 500 mA, 600 mA, 700 mA, 800 mA, 900 mA, and 1000 mA, respectively. Correspondingly, the cathode currents are -50 mA, -100 mA, -150 mA, -200 mA, -300 mA, -400 mA, -500 mA, -600 mA, -700 mA, -800 mA, -900 mA, and -1000 mA, respectively. The anode and cathode currents have the same value but opposite signs. The pulse frequency is 0.5 Hz, and the pulses are applied repeatedly 1800 times.

[0112] The gaseous product (hydrogen) obtained from the test was carried online by argon (flow rate 20 standard cubic centimeters per minute) to a gas chromatograph equipped with a thermal conductivity detector. After electrolysis, the electrolyte in the anode chamber was collected, and the liquid products of the reaction were detected by high performance liquid chromatography. The Faraday efficiencies of each product (specifically glycolic acid, formic acid, and oxalic acid) in the anode of the ethylene glycol AC electrolysis system were calculated as follows: Figure 4 As shown, the Faraday efficiency of hydrogen in the cathode is as follows: Figure 5 As shown, the Faraday efficiency of both glycolic acid and hydrogen remains above 95%, and the oxidation reaction pathway of ethylene glycol is mainly the two-carbon pathway.

[0113] Figure 3 The figure shows a comparison of time-current curves obtained by square wave AC voltage electrolysis and constant voltage power supply in this embodiment. As shown in the figure, the catalyst is rapidly poisoned and deactivated under constant voltage conditions, and the current decreases sharply. However, the catalyst can maintain a high current operation when using square wave AC electrolysis.

[0114] Example 2

[0115] This embodiment is based on the test environment and polyol oxidation AC electrolysis method proposed in Example 1. A square wave waveform was used for AC electrolysis testing, and the pulse frequencies were adjusted to 0.05 Hz, 0.1 Hz, 0.2 Hz, 0.5 Hz, 1 Hz, 2 Hz, and 5 Hz, yielding the following results: Figure 6 The potential-current curves of the ethylene glycol AC electrolysis system shown are presented at different pulse frequencies. It can be seen that the AC electrolysis method for the electrocatalytic oxidation of polyols is applicable at different pulse frequencies, and the electrolysis performance can be controlled by changing the pulse frequency, which is a control method that DC electrolysis does not have.

[0116] Example 3

[0117] This embodiment is based on the test environment and polyol oxidation AC electrolysis method proposed in Example 1. An AC electrolysis test was conducted using a square wave waveform (i.e., an ethylene glycol AC electrolysis system based on a square wave), with anode and cathode currents of 300 mA and -300 mA, respectively, and a pulse frequency of 0.5 Hz. A DC electrolysis method was also used under the same test environment (i.e., an ethylene glycol DC electrolysis system), with anode and cathode currents of 300 mA and -300 mA, respectively.

[0118] Potential-time curves for two testing methods were recorded, and the Faraday efficiency of the gold-supported catalyst in the ethylene glycol AC electrolysis system based on square waves was detected at different times. Figure 8 This is a graph showing the electro-oxidation stability of the ethylene glycol DC electrolysis system in this embodiment. The stability time is only half an hour, and the voltage is higher than 2 volts. Figure 7 The figure shows the catalyst electro-oxidation stability of the ethylene glycol AC electrolysis system based on square wave in this embodiment. Its stability time exceeds 3600 hours, and it maintains a voltage of about 1 volt. It can be seen that the stability of the AC electrolysis method for the electrocatalytic oxidation of polyols is significantly better than that of the DC electrolysis method, and the energy consumption is also significantly lower than that of the DC electrolysis method.

[0119] Example 4

[0120] This embodiment proposes a membrane-free electrolytic device for polyol oxidation, the structure of which is as follows: Figure 9 As shown, it includes a left end plate 1, several electrolysis units 2 and a right end plate 4 stacked and tightly fitted in sequence, with a middle partition layer 3 set between adjacent electrolysis units 2; the several electrolysis units 2 are connected in series, and the number of electrolysis units 2 is set according to the requirements of integrated electrolysis; the electrolysis unit 2 is composed of a first catalyst 5, a first gasket 6, an intermediate layer 7, a second gasket 8 and a second catalyst 9 stacked in sequence, and the first catalyst 5 and the second catalyst 9 are both led out to the outside of the device through a lead wire 10.

[0121] like Figure 10As shown, the left end plate 1 includes a left end plate threaded hole 11, a left end plate liquid inlet 12, and a left end plate chamber 13. The left end plate liquid inlet 12 is located below the left end plate 1, and the left end plate chamber 13 is specifically a groove facing the side of the electrolysis unit 2. Figure 11 As shown, the right end plate 4 includes a right end plate threaded hole 41, a right end plate liquid outlet 42, and a right end plate chamber 43. The right end plate liquid outlet 42 is located above the right end plate 4, and the right end plate chamber 43 is specifically a groove facing the side of the electrolysis unit 2. Figure 12 As shown, the intermediate septum 3 includes an intermediate septum threaded hole 31 and an intermediate septum chamber 32. (As...) Figure 13 As shown, the first gasket 6 includes a gasket threaded hole 61 and a gasket chamber 62. The second gasket 8 has the same structure as the first gasket 6. Figure 14 As shown, the intermediate layer 7 includes an intermediate layer threaded hole 71 and an intermediate layer chamber 72.

[0122] In this embodiment, the intermediate partition layer 3 is slightly thicker than the intermediate layer 7. The intermediate layer 7 is mainly used to separate the anode and cathode. The smaller the thickness, the more effectively the internal resistance of the system can be reduced and the energy utilization efficiency can be improved. The intermediate partition layer 3 is used to achieve isolation between adjacent electrolysis units 2, reduce fluid disturbance and electric field interference between units, and ensure that the electrolysis process is stable and controllable.

[0123] The intermediate partition chamber 32, gasket chamber 62 and intermediate layer chamber 72 are all hollow chambers with the same cross-sectional dimensions as the groove dimensions of the left end plate chamber 13 and the right end plate chamber 43, thus forming an electrolysis chamber inside the polyol oxidation membraneless electrolysis device.

[0124] In this embodiment, both the first catalyst 5 and the second catalyst 9 are gold-supported catalysts, alternately serving as the working electrode (anode) and the counter electrode (cathode). By applying alternating current between the working electrode and the counter electrode, high-value-added products and hydrogen are electrocatalyzed. The first catalyst 5 and the second catalyst 9 cover 50% of the hollowed-out area and are located at the lower position of the electrolysis chamber window, allowing the upper part of the electrolysis chamber window to be connected for venting the hydrogen produced by the reaction. This structure effectively avoids the pressure buildup problem caused by gas accumulation under high current density, and prevents the catalyst from failing to fully contact the electrolyte due to gas encapsulation, thereby significantly improving the overall operational stability and reaction reliability of the device.

[0125] The electrolyte in the electrolysis unit consists of 0.3 mol / L ethylene glycol and 1 mol / L potassium hydroxide solution. During the electrolysis reaction, the electrolyte is pumped in through the inlet 12 on the left end plate, passes through the electrolysis chamber, and is pumped out through the outlet 42 on the right end plate, achieving continuous mass transfer. The groove dimensions of the left end plate 1 and the right end plate 4 ensure that the end catalyst is completely immersed in the electrolyte and fully participates in the electrochemical reaction.

[0126] In this embodiment, the lead wire 10 is made of conductive material, and the materials of the left end plate 1, the middle partition layer 3, the right end plate 4, and the first gasket 6, the middle layer 7, and the second gasket 8 of the electrolysis unit 2 are all made of non-metallic materials, which can effectively avoid illegal Radic electron loss caused by the charging and discharging of structural components during AC electrolysis, and improve energy utilization and system operation stability.

[0127] Apart from the key structural design mentioned above, this embodiment does not impose special limitations on parameters such as the overall size of the electrolysis device, the effective area of ​​the catalyst, the number of threaded holes, and the number of leads. These parameters can be flexibly adjusted and adapted according to the production scale, reaction system, and assembly requirements, and have strong versatility and scalability.

[0128] Example 5

[0129] This embodiment is based on the polyol oxidation membrane-free electrolysis device proposed in Example 4. AC electrolysis testing was conducted using a square wave waveform (i.e., an ethylene glycol AC electrolysis system based on a square wave). The coverage area of ​​the first catalyst 5 and the second catalyst 9 was 5 square centimeters. The anode and cathode currents were 2.5 amperes and -2.5 amperes, respectively, and the pulse frequency was 0.5 Hz. DC electrolysis was also conducted using the same polyol oxidation membrane-free electrolysis device (i.e., an ethylene glycol DC electrolysis system), with anode and cathode currents of 2.5 amperes and -2.5 amperes, respectively.

[0130] Cell pressure-time curves for two testing methods were recorded, and the selectivity and single-pass conversion of the gold-supported catalyst in the ethylene glycol AC electrolysis system based on square wave were detected at different times. Figure 15 This diagram compares the electrolytic stability of the square-wave-based AC electrolysis system and the DC electrolysis system of ethylene glycol in this embodiment within a 5 cm² polyol oxidation membrane-free electrolysis device. In the DC electrolysis system, the device cell voltage rises rapidly, indicating device deactivation. In contrast, the square-wave-based AC electrolysis system of ethylene glycol exhibits stability exceeding 1000 hours, glycolic acid selectivity approaching 100%, and a single-pass conversion rate of approximately 80%, demonstrating the feasibility of the AC electrolysis method for polyol oxidation in this device.

[0131] Example 6

[0132] This embodiment is based on the polyol oxidation membrane-free electrolysis device proposed in Example 4, and adopts a square wave waveform (i.e., an ethylene glycol AC electrolysis system based on a square wave) and as shown in Example 4. Figure 16The sinusoidal waveform shown (i.e., the ethylene glycol AC electrolysis system based on a sinusoidal wave) was used for AC electrolysis testing. The coverage area of ​​the first catalyst 5 and the second catalyst 9 was 25 square centimeters. In the square wave-based ethylene glycol AC electrolysis system, the anode and cathode currents were 10 amperes and -10 amperes, respectively, with a pulse frequency of 0.5 Hz. In the sinusoidal wave-based ethylene glycol AC electrolysis system, the pulse frequency was 0.5 Hz, and the cell voltage was 3.15 volts.

[0133] The cell pressure-time curves of the ethylene glycol AC electrolysis system based on square waves and the peak current-time curves of the ethylene glycol AC electrolysis system based on sine waves were recorded. At the same time, the selectivity and single-pass conversion rate of the gold-supported catalyst in the device at different times were detected. Figure 17 The diagram shows the electrolytic stability of the 25 cm² polyol oxidation membrane-free electrolytic device based on the square wave ethylene glycol AC electrolysis system in this embodiment. It can be seen that the selectivity of glycolic acid is close to 100%, the single-pass conversion rate is about 80%, and the stability exceeds 700 hours. Figure 18 This diagram shows the electrolytic stability performance of a 25 cm² polyol oxidation membrane-free electrolytic device based on a sinusoidal wave ethylene glycol AC electrolysis system in this embodiment. Similarly, the glycolic acid selectivity is close to 100%, the single-pass conversion rate is approximately 80%, but the stability exceeds 1400 hours. Given the superior stability of the sinusoidal wave-based ethylene glycol AC electrolysis system and its high compatibility with industrial power, avoiding the high costs associated with current waveform conversion, the sinusoidal wave-based ethylene glycol AC electrolysis system has enormous potential for industrial scale-up.

[0134] Example 7

[0135] This embodiment proposes a large-scale electrolysis system for polyol oxidation, with the same structure as the membrane-free electrolysis device for polyol oxidation proposed in Example 4. The first catalyst 5 and the second catalyst 9 cover an area of ​​425 square centimeters to simulate a large-scale electro-oxidation conversion process of ethylene glycol. AC electrolysis testing was conducted using a sinusoidal waveform (i.e., a sinusoidal AC electrolysis system for ethylene glycol), with a pulse frequency of 0.5 Hz and a cell voltage of 48 volts.

[0136] Figure 19 This diagram shows the electrolytic stability performance of the 425 cm² polyol oxidation large-scale electrolysis system based on a sinusoidal wave AC electrolysis system for ethylene glycol in this embodiment. Figure 20The graph shows the change in glycolic acid production rate over time in the 425 cm² polyol oxidation scale-up electrolysis system based on a sinusoidal ethylene glycol AC electrolysis system in this embodiment. It can be seen that the system achieved continuous and stable operation for 220 hours. During the operation, the selectivity of the target product glycolic acid remained above 97%, and the production rate reached about 85 grams per hour, which is equivalent to an annual production capacity of about 0.75 tons. This fully demonstrates the feasibility of scaling up the technology.

[0137] Example 8

[0138] This embodiment proposes a large-scale electrolysis system for polyol oxidation adapted to public power grids. Its structure is the same as that of the membraneless electrolysis device for polyol oxidation proposed in Example 4. The coverage area of ​​the first catalyst 5 and the second catalyst 9 is 50 square centimeters. AC electrolysis testing is performed using a sine wave waveform (i.e., an ethylene glycol AC electrolysis system based on a sine wave), with a pulse frequency of 50 Hz (the standard frequency of public power grids) and a cell voltage of 4.2 volts.

[0139] Figure 21 This diagram shows the electrolytic stability performance of a 50 square centimeter polyol oxidation scale-up electrolysis system adapted to a public power grid, based on a sinusoidal wave ethylene glycol AC electrolysis system in this embodiment. It can be seen that the device can operate continuously for 100 hours, exhibiting excellent operational stability and high selectivity. The catalyst maintains a glycolic acid selectivity of over 93% throughout the entire test cycle, unaffected by significant frequency factors, and remains stably maintained at a high level. This fully demonstrates the feasibility and reliability of this directly grid-driven production system. Figure 24 The directly grid-driven electro-oxidation production system for polyols shown provides a practical and feasible technical path for the industrial electrochemical production of glycolic acid.

[0140] Example 9

[0141] This embodiment proposes a membrane-free electrolytic device for polyol oxidation. Compared with Embodiment 4, the only difference is that the type of polyol is changed to glycerol. Specifically, the electrolyte consists of 1 mol / L glycerol and 3 mol / L potassium hydroxide solution. All other structures are the same.

[0142] In this embodiment, the coverage area of ​​the first catalyst 5 and the second catalyst 9 is 5 square centimeters. The AC electrolysis catalytic performance is tested using a sine wave waveform (i.e., a glycerol AC electrolysis system based on a sine wave), with a cell voltage of 3.1 volts and a pulse frequency of 5 Hz.

[0143] Figure 22The diagram shows the electrolytic stability of the 5 cm² polyol oxidation membrane-free electrolysis device based on the glycerol AC electrolysis system in this embodiment. It can be seen that during the 110-hour continuous electrolysis process, the selectivity of the target product lactic acid was stably maintained at about 45%, which proves the applicability of the AC electrolysis method for polyol electrocatalytic oxidation in different types of polyol oxidation reactions.

[0144] Example 10

[0145] This embodiment proposes a membrane-free electrolytic device for polyol oxidation. Compared with Embodiment 4, the only difference is that the type of polyol is changed to 1,2-propanediol. Specifically, the electrolyte consists of 1 mole per liter of 1,2-propanediol and 3 moles per liter of potassium hydroxide solution. All other structures are the same.

[0146] In this embodiment, the coverage area of ​​the first catalyst 5 and the second catalyst 9 is 5 square centimeters. The AC electrolysis catalytic performance is tested using a sine wave waveform (i.e., a 1,2-propanediol AC electrolysis system based on a sine wave), with a cell voltage of 3.2 volts and a pulse frequency of 5 Hz.

[0147] Figure 23 The diagram shows the electrolytic stability of the 5 cm² polyol oxidation membrane-free electrolysis device based on the sine wave 1,2-propanediol AC electrolysis system in this embodiment. It can be seen that the selectivity of the target product lactic acid can reach 86% during 50 hours of continuous electrolysis, which also proves the applicability of the AC electrolysis method for polyol electrocatalytic oxidation in different types of polyol oxidation reactions.

[0148] The above provides a detailed description of the polyol oxidation AC electrolysis method, membrane-free electrolysis device, and large-scale electrolysis system provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of this invention, including the best mode, and also to enable any person skilled in the art to practice this invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the textual description of the claims, or if they include equivalent structural elements that are not substantially different from the textual description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A polyol oxidation alternating current electrolysis method, characterized in that, In the electrolysis system, a noble metal-based catalyst is used as the working electrode, and polyols and aqueous electrolytes are used as the working electrode substrates. By applying alternating current between the working electrode and the counter electrode, high-value-added products and hydrogen are produced electrocatalystly.

2. The polyol oxidation alternating electrolysis method according to claim 1, characterized in that, The electrocatalytic oxidation performance of polyols can be controlled by changing the pulse frequency and / or input waveform of the alternating current; wherein the pulse frequency of the alternating current is 0.00001 Hz to 500 Hz, the pulse current is 0.001 ampere to 1000 ampere, and the pulse voltage is 0.6 volt to 660 volt; the input waveform of the alternating current is at least one of square wave, sine wave, triangle wave, sawtooth wave, and step wave.

3. The polyol oxidation alternating electrolysis method according to claim 1, characterized in that, The polyol is ethylene glycol, glycerol, or 1,2-propanediol.

4. The polyol oxidation alternating electrolysis method according to claim 1, characterized in that, The concentration of polyol in the substrate of the working electrode is 0.001 mol / L to 5 mol / L.

5. The polyol oxidation alternating electrolysis method according to claim 1, characterized in that, The precious metal-based catalyst is a precious metal sheet, a precious metal mesh, or a precious metal powder supported catalyst. The precious metal is at least one of palladium, platinum, gold, and silver. The substrate of the precious metal powder supported catalyst is at least one of carbon paper, carbon cloth, carbon felt, nickel foam, and titanium felt.

6. The polyol oxidation alternating electrolysis method according to claim 1, characterized in that, The aqueous electrolyte is at least one of potassium hydroxide solution, sodium hydroxide solution, lithium hydroxide solution, potassium carbonate solution, sodium carbonate solution, sodium perchlorate solution, potassium sulfate solution, perchloric acid solution, and sulfuric acid solution; wherein the concentration of potassium hydroxide solution, sodium hydroxide solution, lithium hydroxide solution, and potassium carbonate solution is 0.1 mol / L to 5 mol / L; the concentration of sodium carbonate solution is 0.1 mol / L to 2 mol / L; the concentration of sodium perchlorate solution is 0.1 mol / L to 3 mol / L; and the concentration of potassium sulfate solution, perchloric acid solution, and sulfuric acid solution is 0.1 mol / L to 0.5 mol / L.

7. The polyol oxidation alternating electrolysis method according to claim 1, characterized in that, The electrolysis system is a two-electrode system or a three-electrode system, and its reaction device is an H-type electrolytic cell, a flow electrolytic cell, or a membrane electrode electrolytic cell.

8. A membrane-free electrolytic device for polyol oxidation, characterized in that, The device comprises a left end plate, several electrolysis units, and a right end plate stacked sequentially, with intermediate partitions between adjacent electrolysis units. The electrolysis units are connected in series. Each electrolysis unit consists of a first catalyst, a first gasket, an intermediate layer, a second gasket, and a second catalyst stacked sequentially. The intermediate partition and the first, intermediate, and second gaskets of the electrolysis units have hollow areas with the same cross-sectional size. Both the first and second catalysts are noble metal-based catalysts, which alternately serve as the working electrode and the counter electrode, and their coverage area in the hollow areas is 30% to 70%. The electrolyte of the electrolysis unit consists of a polyol and an aqueous electrolyte. Alternating current is applied between the working electrode and the counter electrode through a lead wire to electrocatalyze the production of high-value-added products and hydrogen.

9. The polyol oxidation membrane-free electrolysis device according to claim 8, characterized in that, The left and right end plates have grooves with the same cross-sectional dimensions as the hollowed-out area on the side facing the electrolysis unit, which together with the hollowed-out area form an electrolysis chamber inside the polyol oxidation membraneless electrolysis device; the first catalyst and the second catalyst are located at the lower position of the hollowed-out area, so that the upper position of the electrolysis chamber is connected for exporting the hydrogen gas generated by the reaction.

10. The polyol oxidation membrane-free electrolysis device according to claim 9, characterized in that, An alternating current with a sinusoidal waveform is applied between the working electrode and the counter electrode. By adjusting the number of stacked electrolysis units, the total electrolysis voltage of the polyol oxidation membraneless electrolysis device is made compatible with the amplitude of the AC power supply voltage of the public power grid, thus eliminating the need to use a step-down transformer or step-down conversion circuit.

11. A large-scale electrolytic system for polyol oxidation, characterized in that, Its structure is the same as that of the polyol oxidation membraneless electrolysis device described in claim 9, wherein the coverage area of ​​the first catalyst and the second catalyst is not less than 0.3 square centimeters.

12. The large-scale electrolysis system for polyol oxidation according to claim 11, characterized in that, An alternating current with a sinusoidal waveform is applied between the working electrode and the counter electrode. By adjusting the number of stacked electrolysis units, the total electrolysis voltage of the polyol oxidation large-scale electrolysis system adapted to the public power grid is made to match the amplitude of the AC power supply voltage of the public power grid, thus eliminating the need to use a step-down transformer or step-down conversion circuit.

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