Novel electrochemical flow reactor and application

Abstract

The invention provides a novel electrochemical flow reactor and application, and belongs to the technical field of electrochemical flow reactors, the novel electrochemical flow reactor comprises an electrolytic tank and a peristaltic pump, the electrolytic tank comprises two bases, two gaskets, two electrodes, two current collectors and two central gaskets which are symmetrically arranged from outside to inside; the current collector is provided with two liquid storage tanks and a flow channel, and the two liquid storage tanks are communicated through the flow channel; compared with other reactors, a novel current collector runner is designed, liquid mass transfer can be enhanced, a reference assembly and a gas assembly are added, the distance between electrodes is controllable in an assembling mode, and the current density and the reaction stability are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical flow reactors, and in particular to a novel electrochemical flow reactor and its application. Background Art

[0002] In traditional electrocatalysis, electrolysis methods based on beakers or H-type electrolytic cells often have difficulty controlling the mass transfer process. Due to the limitations of reaction speed, mass transfer rate, substrate solubility, electrode area to solution volume ratio, and stirring dead zone, they often have disadvantages such as poor repeatability, difficulty in quantifying in-situ reaction parameters, and low conversion selectivity. In addition, it is difficult to expand production scale, which limits the practical application of electrocatalysis. In comparison, continuous flow electrocatalysis technology links the flow device and the electrolytic cell. By controlling the flow rate, the reaction parameters can be better adjusted to achieve more precise reaction regulation, thereby overcoming the inherent defects of the traditional "one-pot" reaction cell. At the same time, the stacking of flow reactors also makes it more feasible to expand the scale of reaction production. Currently, according to different functions, common electrochemical flow reactors are divided into the following types:

[0003] Electrochemical filter presses are a relatively early and well-researched device. Electrocatalytic reactions often focus on studying in situ electrochemical reaction data, hoping to achieve equivalent, stable reactions at all electrode points. However, conventional electrolytic cells often struggle to achieve this by limiting the solution volume / electrode area ratio and mass transfer rates. Parallel-plate flow reactors, on the other hand, can increase the mass transfer rate by reducing the diffusion layer thickness by increasing the electrolyte flow rate. As early as 1992, D. Robinson et al. tested the mass transfer performance of the FMO1-LC flow reactor. Using the reduction of 1.0 mM ferrocyanide in a 1.0 M KOH aqueous solution, they demonstrated that increasing the mass transfer rate positively correlated with a positive increase in the reaction current, promoting the overall reaction. They also investigated the effects of various turbulence promoters on the mass transfer rate. In this reactor, mass transfer can also be achieved by pumping. In the FMO1-LC, the anode and cathode are sandwiched between a stack of spacers and current collectors, supported by support bases on either side. However, the device's complex design and lack of flow channels make the liquid mass transfer state on the electrode surface somewhat uncontrollable. In recent years, the FM01-LC reactor has seen numerous applications, most notably the degradation of sulfamethoxazole using active chlorine flow reaction by Jorge Vazquez-Arenas et al. and the electrochemical oxidation of dichlorophenol by A. Regalado-Méndez et al.

[0004] Electrochemical flow cell is a commercial electrolytic cell that has developed more maturely in recent years. It has realized the construction from micro flow cell to large-scale reactor with 3 to 4 chambers. The electrode area is as small as 0.001m 3 , up to 16m 3, which realized the transition from lab-scale reaction to industrial-scale production. Taking a micro flow cell as an example, the flow cell has a leak-proof structure and can also install a gas diffusion electrode. It is also more tolerant to temperature requirements and can withstand different reaction flow rates. And by stacking the number of gaskets, the spacing between the electrodes can be freely controlled. Shannon S. Stahl et al. realized the alcohol oxidation in the synthesis of levetiracetam through an electrocell reactor, and when the scale was 200g, the enantiomeric purity was more than 97%

[0005] Overall, in recent years, electrocatalytic flow devices have gradually begun to commercialize and scale up, providing convenience for industrial-scale production. However, for different reaction systems, different types of flow devices have different requirements for mass transfer rate, current efficiency, turbulence, and catalyst carrier material. Therefore, there is an urgent need for a flexible, free-loading, disassembling, and reassembling, modular electrochemical flow device that can meet the needs of most reaction systems. SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings of the prior art and provide a novel electrochemical flow reactor. By connecting the flow device and the electrolytic cell, the reaction parameters can be better adjusted to achieve more precise reaction control by controlling the flow rate and other conditions. At the same time, the stacking of the flow reactor also makes it more feasible to scale up the reaction. Compared with other reactors, the present application designs a new type of current collector flow channel that can enhance liquid mass transfer, and adds reference components and gas components, and makes the inter-electrode distance controllable through assembly, effectively improving the current density and reaction stability.

[0007] Technical scheme: The novel electrochemical flow reactor comprises an electrolytic cell and a peristaltic pump, the electrolytic cell comprises two bases, two gaskets, two electrodes, two current collectors and two center gaskets which are symmetrically arranged from outside to inside. The current collector is provided with two liquid storage grooves and a flow channel, and the two liquid storage grooves are communicated through the flow channel. The base provides an inlet and an outlet (adapter) for the fluid and mechanical support, the gasket and the center gasket can be leak-proof and separate different components, the electrode can catalyze electrochemical reaction, the current collector has the functions of electricity conduction and flow conduction, and the inside is provided with liquid storage grooves and flow channels. The liquid storage groove is used for enriching the fluid, and the flow channel guides the fluid to rise vertically. The peristaltic pump transports the fluid by periodically squeezing the hose, which can accurately control the flow rate and ensure the continuous input of reactants and the discharge of products.

[0008] Before the reaction, the inlet of the peristaltic pump is connected to the lower end of the adapter on one side of the base, and if the reaction system does not require an ion exchange membrane, the outlet is connected to the upper adapter on the other side of the base; if the reaction system requires an ion exchange membrane, two sets of pipelines are required, which are connected to the upper and lower adapters on one side of the base respectively. The fluid is transported by the peristaltic pump, transported from the liquid storage bottle through the pipeline, and flows into the device through the adapter of the base, and then is enriched in the liquid storage tank opened below the current collector and the gasket. As the fluid pressure gradually increases, the fluid rises through the flow channel opened in the center of the current collector, contacts the electrode and completely immerses the electrode. The upper end of the two current collectors is connected to the electrode clamp, and the reaction proceeds normally. The liquid after the reaction is discharged through the upper right corner of the other base plate.

[0009] Further improve the above technical solutions, for the reaction system requiring ion exchange membrane, the two central gaskets are provided with ion exchange membranes, at this time, the two current collectors are provided with two independent liquid storage tanks.

[0010] Further, for the reaction system requiring ion exchange membrane, the two central gaskets are provided with gas exchange components, and the gas is introduced into the reactor from the side opening.

[0011] Further, for the reaction system requiring a reference electrode, the two central gaskets are provided with a reference component, and the reference electrode is inserted from the upper part of the component.

[0012] Further, the flow channel comprises a group of S-shaped flow channel units connected in series.

[0013] Further, the flow channel comprises a group of Z-shaped flow channel units connected in series.

[0014] Further, the cross section of the flow channel is rectangular.

[0015] Application of a novel electrochemical flow reactor in electrochemical flow reaction.

[0016] Application of a novel electrochemical flow reactor in nitrate electro-reduction reaction.

[0017] Application of a novel electrochemical flow reactor in methanol electro-oxidation reaction.

[0018] Advantages: Compared with the prior art, the advantages of the present application are:

[0019] (1) The two liquid storage tanks on the current collector of the present application are connected by a flow channel. After the fluid is enriched in the liquid storage tank, it is uniformly lifted to the surface of the electrode by the pressure drive, reducing the dead angle of fluid flow, forcing the fluid to rise vertically, ensuring that the electrode surface is completely immersed and uniformly contacted with the reaction liquid, reducing the mass transfer resistance and improving the reaction efficiency.

[0020] (2) The present application designs an electrochemical flow reactor suitable for various environments and various needs, which can flexibly adjust the electrode spacing, fluid flow state, fluid flow channel, is suitable for catalyst carriers with various morphologies, and can be applied to reaction systems requiring gas, ion exchange membrane, reference electrode participation, and has application in rapid and large-scale electro-synthesis and catalyst stability. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a structural schematic diagram of an electrolytic cell in the present application;

[0022] Figure 2 is a structural schematic diagram of a base in the present application;

[0023] Figure 3 is a structural schematic diagram of a gasket in the present application;

[0024] Figure 4 is a structural schematic diagram of a center gasket in the present application;

[0025] Figure 5 is a structural schematic diagram of a current collector with an S-shaped flow channel in the present application;

[0026] Figure 6 is a structural schematic diagram of a current collector with a Z-shaped flow channel in the present application;

[0027] Figure 7 is a structural schematic diagram of a current collector with a rectangular cross-section flow channel in the present application;

[0028] Figure 8 is a structural schematic diagram of an ion exchange membrane in the present application;

[0029] Figure 9 is a structural schematic diagram of a gas exchange assembly in the present application;

[0030] Figure 10 is a structural schematic diagram of a reference assembly in the present application;

[0031] Figure 11 is a structural schematic diagram of a reference assembly in the present application;

[0032] Figure 12 is a structural schematic diagram of a reference assembly in the present application;

[0033] Figure 13For RuCu in 1M KOH solution, (a) is the VT image of constant current magnified electrolysis, (b) is the VT image of constant current 1h electrolysis test, and (c) is the VT image of constant current full conversion electrolysis test.

[0034] Figure 14 Comparison of electrolysis performance of RuCu in 1M KOH solution between batch cell and flow reactor

[0035] Figure 15 For Au-Ni00H in 1M KOH, (a) is the constant current electrolysis performance test, (b) is the constant current electrolysis VT image, and (c) is the linear sweep voltammetry electrolysis. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the embodiments.

[0037] Example 1

[0038] like Figure 1 A novel electrochemical flow reactor shown includes an electrolytic cell and a peristaltic pump. The electrolytic cell includes, from bottom to top, a first base 101, a first gasket 201, a first electrode 301, a first current collector 401, a first central gasket 501, a second central gasket 502, a second current collector 402, a second electrode 302, a second gasket 202, and a second base 102; the first base 101 and the second base 102 have the same structure, the first gasket 201 and the second gasket 202 have the same structure, the first electrode 301 and the second electrode 302 are the anode and the cathode respectively, the first current collector 401 and the second current collector 402 have the same structure, and the first central gasket 501 and the second central gasket 502 have the same structure.

[0039] Two first liquid storage tanks 601 are provided in the first gasket 201 and the first current collector 401, and a first flow channel is provided between the two first liquid storage tanks; two second liquid storage tanks 602 are provided in the second current collector 402 and the second gasket 202, and a second flow channel is provided between the two second liquid storage tanks; when the first base 101, the first gasket 201, the first electrode 301, the first current collector 401, the first center gasket 501, the second center gasket 502, the second current collector 402, the second electrode 302, the second gasket 202 and the second base 102 are combined into a whole, the corresponding first liquid storage tanks 601 and the second liquid storage tanks 602 are combined into a whole liquid storage tank; the corresponding first flow channel and the second flow channel are combined into a whole flow channel.

[0040] Since the first base 101 and the second base 102 have the same structure, the first base 101 is taken as an example. Figure 2As shown, the first base 101 includes ten base screw interfaces 103 surrounding the periphery, and also includes two liquid outlets 104 located at the upper portion and two liquid inlets 105 located at the lower portion.

[0041] like Figure 3 As shown, the gasket 2 includes ten gasket screw interfaces 201 surrounding the periphery. At positions corresponding to the liquid reservoirs of the current collector, the gasket also has corresponding gasket liquid reservoirs 202 and 203 of the same shape and a gasket liquid reservoir port 204. The gasket liquid reservoir port 204 is not connected to the two gasket liquid reservoirs 202 and 203.

[0042] like Figure 4 As shown, the central gasket 5 includes ten central gasket screw interfaces 501 surrounding the periphery. At positions corresponding to the liquid reservoirs of the current collector, the central gasket also has corresponding central gasket liquid reservoirs 502 and 503 of the same shape and a central gasket liquid reservoir port 504. The central gasket liquid reservoir port 504 communicates with the two central gasket liquid reservoirs 502 and 503 through central gasket flow channels 505.

[0043] like Figure 5 As shown, the collector has an electrode on the top, and the flow channel 7 includes a group of S-shaped flow channel units connected end to end.

[0044] like Figure 6 As shown, the collector has an electrode on the top, and the flow channel 7 includes a group of Z-shaped flow channel units connected end to end.

[0045] like Figure 7 As shown, the current collector has an electrode on its upper portion, and the cross section of the flow channel 7 is rectangular.

[0046] In this embodiment, the length of the entire new electrochemical flow reactor is 120 mm and the width is 90 mm; the length of the liquid storage tank is 50 mm and the width is 10 mm; the length of the liquid storage port is 30 mm and the width is 30 mm; the length of the central gasket liquid storage tank is 50 mm and the width is 10 mm; the length of the central gasket liquid storage port is 24 mm and the width is 24 mm; the width of the central gasket flow channel is 3 mm, and the thickness of the collector is 1.5 mm.

[0047] Example 2

[0048] The difference between this embodiment and embodiment 1 is that: Figure 8 As shown, a conventional Fumasep FAA-3-PK-130 ion exchange membrane 6, used in the prior art, is placed between the two center spacers. In this case, the liquid reservoirs in the two current collectors function as two independent reservoirs. The ion exchange membrane effectively separates the cathode and anode solutions, allowing only ions required for conductive transport to pass through the membrane. This membrane also prevents substances generated at the cathode or anode from reacting with the other electrode.

[0049] Example 3

[0050] The difference between this embodiment and embodiment 1 is that: Figure 9 As shown, a gas exchange assembly 9 is provided between the two center gaskets, including 10 screw interfaces 901 of the gas exchange assembly and a liquid storage tank 903 , on which a gas outlet 902 and a gas inlet 904 are provided.

[0051] Example 4

[0052] The difference between this embodiment and embodiment 1 is that: Figure 10 As shown, a reference assembly 8 is positioned between the two center spacers. It includes ten screw connections 801 for the reference assembly, two upper and lower liquid reservoirs 803, which are connected via a liquid reservoir port 804 and a flow channel 805. The reference assembly also includes a reference port 802. The reference assembly provides an additional reference electrode access point in the solution system, enabling accurate measurement of the relative working potential of the working electrode.

[0053] Test Example 1

[0054] In the nitrate reduction system: potassium hydroxide solution is used as the reaction solution, potassium nitrate is used as the reaction electrolyte, RuCu is used as the cathode, commercial titanium mesh is used as the anode, the designed reactor is used as the electrolytic cell, and an electrocatalytic reaction system is constructed to carry out electrocatalytic reaction on the nitrate solution.

[0055] The RuCu is prepared by the following steps: cutting the foam copper into 3 x 3 cm 2 The square was washed with 0.1M hydrochloric acid solution, ethanol and deionized water in sequence. 100mL of aqueous solution containing 0.1M ammonium persulfate and 1M sodium hydroxide was prepared, and the cleaned foam copper was placed in it and oxidized at room temperature for 1 hour. After taking it out, it was washed with deionized water and placed in a 10mM ruthenium trichloride solution for ion exchange for 12 hours. Dry at 70°C for 1 hour. The ion-exchanged foam copper was placed in a crucible, placed in a tubular furnace and heated in nitrogen, and the temperature was raised to 200°C at a rate of 5°C / min, maintained for 2 hours, and then cooled to room temperature. The obtained RuCu was ion-exchanged in a 1M potassium hydroxide solution at -700mA / cm 2 Electrolysis was performed at constant current for 1 h.

[0056] In application, the reaction solution is 1M potassium nitrate solution, the reaction substrate is potassium nitrate with a concentration of 0.05 to 0.5M, and the reaction voltage range is 0 to -3V.

[0057] Test Example 2

[0058] In the methanol electro-oxidation reaction system: potassium hydroxide solution is used as the reaction solution, Au-NiOOH is used as the anode, commercial titanium mesh is used as the cathode, the designed reactor is used as the electrolytic cell, and an electrocatalytic reaction system is constructed to carry out electrocatalytic reaction on the methanol solution.

[0059] The Au-NiOOH is prepared by cutting the nickel foam into 3 x 3 cm 2 A square was washed sequentially with 0.1M hydrochloric acid solution, ethanol, and deionized water. 3mL of 0.1M HAuCl₄ was dissolved in 20mL of deionized water. The cleaned nickel foam was immersed in the solution for 10 minutes and shaken until the yellow color faded. The resulting Au-Ni was oxidized in 1M potassium hydroxide solution at a constant current of 200mA / cm₂ for 20 minutes.

[0060] In application, the reaction solution is 1M potassium nitrate solution, the reaction substrate is methanol with a concentration of 0.05-0.5M, and the reaction voltage range is 0-2V.

[0061] like Figure 11 (a) and Figure 11 (b) shows the experimental data as follows:

[0062] Figure 11 (a) is the LSV curve of the flow cell at different flow rates. Figure 11 (b) Comparison of the LSV curves of the flow cell and batch cell. To investigate the effect of flow rate on mass transfer and, therefore, current density, LSV tests were performed at various flow rates by adjusting the peristaltic pump (Figure (a)). When the voltage was between –1.5V and –2.3V, the current density at high flow rates increased significantly, indicating that increasing the flow rate helps reduce the Tafel slope and promotes the reaction. To obtain more significant results, the LSV test results of the flow cell and batch cell were compared (Figure (b)). At voltages below the starting potential, the flow cell significantly increased the current density both with and without the addition of substrate.

[0063] like Figure 12 (a) and Figure 12 (b), the experimental data are shown in Table 1 and Table 2:

[0064] Table 1 Electrolysis performance for 1 h at different current densities

[0065]

[0066] Table 2 Full conversion test performance at different current densities

[0067]

[0068] Figure 12: Performance of electrolysis under different current density for 1 h (a) and performance chart of full conversion test under different current density (b). In the constant current electrolysis test under different current density for 1 h (Fig. (a)), the reaction rate and current density almost present linear relationship, and the FE fluctuates between 83% and 95%. It is worth noting that, under the current density of -300 mA / cm2 and -500 mA / cm2, the ammonia Faraday efficiency as high as 97% is achieved. In the full conversion test (Fig. (b)), under a wide current density window, both the ammonia Faraday efficiency and the selectivity are good (FE > 80% Sel. > 80%). When the current density is from -100 mA / cm2 to -1000 mA / cm2, the Faraday efficiency presents a trend of first decreasing and then increasing. At -100 mA / cm2, the ammonia Faraday efficiency as high as 99% is achieved.

[0069] As shown in Figure 13 (a) is the V-T curve of the amplification concentration test, Figure 13 (b) is the V-T curve of the constant current electrolysis test for 1 h, and Figure 13 (c) is the V-T curve of the constant current full conversion test. As can be seen from the figures, in the constant current test, the current density is stable and does not fluctuate abnormally, which shows that the reactor has good stability and can be used for long-time electrolysis test. The gradually increasing voltage is because the concentration of nitrate decreases with the reaction.

[0070] As shown in Figure 14 , the experimental data are shown in Table 3:

[0071] Table 3

[0072]

[0073] Figure 14 : Performance comparison of constant current electrolysis test for 1 h. In order to further understand the performance of the reactor, the performance of the flow reactor is compared with that of the batch cell under the same conditions of catalyst, reaction solution, electrolysis conditions, etc. The reaction condition is constant current electrolysis for 1 h under different current density Figure 14 ), it can be seen directly that, under the current density from -100 mA / cm2 to -1000 mA / cm2, the Faraday efficiency of the flow cell electrolysis is about twice that of the batch cell electrolysis. This fully shows the advantage of the flow cell for the nitrate reduction reaction system. It is preliminarily considered that, due to the circulating fluid and the design of the flow channel assembly, the mass transfer performance in the reaction system is enhanced, so that the reaction substrate on the electrode surface is updated in time, thereby enhancing the electrolysis performance.

[0074] As shown in Figure 15 (a), Figure 15 (b) and Figure 15 (c), the experimental data are shown in Table 4:

[0075] Table 4

[0076]

[0077] Figure 15 (a) is the constant current performance test for methanol oxidation; Figure 15 (b) is the constant current V-T curve for methanol oxidation; Figure 15 (c) is the LSV test for methanol oxidation. To further demonstrate the universality of the designed flow reactor for electrolytic system, the classic oxidation system of methanol electro-oxidation to prepare formic acid was selected as the system expansion experiment. Anode material: Au-NiOOH, cathode material: commercial Pt mesh. The constant current electrolysis performance test was carried out in 1M KOH solution with 1M methanol (Fig. (a)), and high Faraday efficiency (>90%) was achieved at different current densities, and the reaction rate and current density basically showed a linear relationship, which met the characteristics of stable Faraday efficiency. On the other hand, the V-t curve was relatively stable during electrolysis (Fig. (b)), and from this system it was also demonstrated that the reactor had excellent universality and stability.

[0078] As described above, although the present application has been shown and described with reference to certain preferred embodiments, it is to be understood that such embodiments are by way of example only and are not to be construed in a limiting sense. Various changes and modifications obvious to those skilled in the art, in the form and details of the application, can be made without departing from the spirit and scope thereof as defined in the following claims.

Claims

1. A novel electrochemical flow reactor comprising an electrolytic cell and a peristaltic pump, characterized in that: The electrolytic cell comprises two bases (1), two gaskets (2), two electrodes (3), two current collectors (4) and two central gaskets (5) that are symmetrically arranged from the outside to the inside; two liquid storage tanks (6) and a flow channel (7) are provided on the current collector, and the two liquid storage tanks (6) are connected through the flow channel (7); when the reaction liquid is pumped into the liquid inlet of the base via a peristaltic pump, the fluid is enriched in the liquid storage tank, and as the fluid pressure gradually increases, the fluid rises through the flow channel and contacts the electrodes and completely immerses the electrodes, and after the reaction, the fluid flows out through the liquid outlet of the other base.

2. A novel electrochemical flow reactor according to claim 1, characterized in that: An ion exchange membrane (8) is provided between the two central gaskets. In this case, the liquid storage tanks in the two current collectors are two independent liquid storage tanks.

3. The novel electrochemical flow reactor according to claim 1, characterized in that: A gas exchange component (9) is arranged between the two central gaskets.

4. The novel electrochemical flow reactor according to claim 1, characterized in that: A reference component (10) is arranged between the two central spacers.

5. The novel electrochemical flow reactor according to claim 1, characterized in that: The flow channel (7) comprises a group of S-shaped flow channel units connected end to end.

6. The novel electrochemical flow reactor according to claim 1, characterized in that: The flow channel (7) comprises a group of Z-shaped flow channel units connected end to end.

7. The novel electrochemical flow reactor according to claim 1, characterized in that: The cross section of the flow channel (7) is rectangular.

8. Use of the novel electrochemical flow reactor according to any one of claims 1 to 7 in an electrochemical flow reaction.

9. Use of the novel electrochemical flow reactor according to any one of claims 1 to 7 in nitrate electroreduction reaction.

10. Use of the novel electrochemical flow reactor according to any one of claims 1 to 7 in methanol electrooxidation reaction.

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