A method for producing hydrogen sulfide by electrochemical reduction of sulfur dioxide based on a double-electrode flow electrolytic cell

Abstract

The present invention discloses a method for preparing hydrogen sulfide by electrochemically reducing sulfur dioxide based on a dual-electrode flow electrolytic cell. In the method, during the process of electrochemically reducing sulfur dioxide to prepare hydrogen sulfide using the dual-electrode flow electrolytic cell, a cation exchange resin is filled in the cathode chamber of the dual-electrode flow electrolytic cell. The proton-exchanging property of the cation exchange resin is utilized to alleviate the problem of local pH increase on the electrode surface, thereby improving the mass transfer of the SO2 electrochemical reduction reaction, greatly reducing the influence of bubbles on the electrode surface, reducing the reaction cell pressure, and improving the stability of the reaction.

Description

Technical Field

[0001] The present invention relates to a method for preparing hydrogen sulfide by electrochemical reduction of sulfur dioxide, and in particular to a method for preparing hydrogen sulfide by electrochemical reduction of sulfur dioxide based on a double-electrode flow electrolytic cell, belonging to the technical field of resource utilization of industrial sulfur dioxide flue gas. Background Art

[0002] Chinese patent CN113122864A discloses a method for preparing hydrogen sulfide by electrochemical reduction of sulfur dioxide. This method utilizes a membrane electrode to catalyze the electrochemical reduction of sulfur dioxide to generate hydrogen sulfide gas. This method can reduce sulfur dioxide to hydrogen sulfide, but it has the disadvantage of low current density, which limits the larger-scale application of SO2 electrocatalytic reduction.

[0003] The use of a flow electrolyzer for the electrochemical reduction of sulfur dioxide to hydrogen sulfide gas using a membrane electrode is theoretically more suitable as a reactor for large-scale applications due to its higher reactant concentration on the electrocatalyst surface, shorter transport paths, and suitable gas diffusion layer substrate. However, in practice, when the current density is increased, the electrocatalytic reduction of SO2 to H2S is significantly affected by bubbles, resulting in unstable and high cell pressure. Therefore, reducing the cell pressure while increasing the current density is a necessary issue for the industrialization of SO2 electrocatalytic reduction. Summary of the Invention

[0004] In view of the technical problems of unstable and high cell pressure in the process of electrochemical reduction of sulfur dioxide to produce hydrogen sulfide using a dual-electrode flow electrolytic cell in the prior art, the purpose of the present invention is to provide a method for electrochemically reducing sulfur dioxide to produce hydrogen sulfide based on a dual-electrode flow electrolytic cell. The method fills the cathode chamber of the dual-electrode flow electrolytic cell with a cation exchange resin, utilizes the proton exchange property of the cation exchange resin to alleviate the problem of local pH increase on the electrode surface, improves the mass transfer of the SO2 electrochemical reduction reaction, greatly reduces the influence of bubbles on the electrode surface, reduces the reaction cell pressure, and improves the reaction stability.

[0005] In order to achieve the above technical objectives, the present invention provides a method for preparing hydrogen sulfide by electrochemical reduction of sulfur dioxide based on a dual-electrode flow electrolytic cell. The method is to fill the cathode chamber of the dual-electrode flow electrolytic cell with a cation exchange resin during the electrochemical reduction of sulfur dioxide to prepare hydrogen sulfide using the dual-electrode flow electrolytic cell.

[0006] The key to the technical solution of the present invention is to utilize the ion proton exchange characteristics of the cation exchange resin to exchange H +Ion exchange and proton transfer to the electrode surface alleviate the adverse factors of the sharp increase in pH on the electrode surface under high current density on SO2 reduction, and promote the electrode reaction. At the same time, the cation exchange resin is filled in the electrolyte channel of the cathode chamber, which will cause the electrolyte flow channel to narrow. According to the Bernoulli equation, when the liquid narrows from the flow channel, the flow rate will increase. Therefore, the filling resin will improve the flow state of the electrolyte in the microchannel, which will greatly increase the flow rate of the electrolyte, reduce the adhesion of bubbles on the electrode surface, and promote the mass transfer of the SO2 electrochemical reduction reaction, thereby accelerating the refresh rate of the electrolyte on the electrode surface and improving the discharge efficiency of hydrogen by-products, reducing the residence time of bubbles on the electrode surface, reducing the reactor resistance, reducing the reaction tank pressure, and improving the reaction stability.

[0007] As a preferred embodiment, the cation exchange resin is at least one of a strongly acidic 732 hydrogen cation exchange resin, a strongly acidic 732 sodium ion exchange resin, and a weakly acidic acrylic cation exchange resin, each having a certain proton exchange and transfer capacity. Most preferably, the strongly acidic 732 hydrogen cation exchange resin and / or the strongly acidic 732 sodium ion exchange resin are used.

[0008] As a preferred embodiment, the cation exchange resin is pretreated by soaking it in 2% to 5% by weight dilute hydrochloric acid for 18 to 30 hours. This soaking in dilute hydrochloric acid causes the resin to swell, removes impurities from the resin pores, improves its proton exchange capacity, and facilitates the passage of the electrolyte.

[0009] As a preferred solution, the filling amount of the cation exchange resin is 0.5 to 1.25 g / cm 3 If the filling amount is higher than 1.25g / cm 3 When the electrolyte channel of the cathode chamber is tightly filled with cation exchange resin, the pressure of the resin on the gas diffusion electrode is too large, which may easily cause the gas diffusion electrode to rupture; if the filling amount is less than 0.5g / cm 3 When the cation exchange resin flows in the channel, it cannot contact the electrode surface well (such as Figure 2 ).

[0010] As a preferred embodiment, the dual-electrode flow electrolysis cell uses an inert metal as the anode and a gas diffusion electrode as the cathode. The cathode and anode compartments are separated by a proton membrane or a bipolar membrane. The gas diffusion electrode comprises a porous hydrophobic matrix and a catalytic material on its surface. The cathode compartment electrolyte is a sulfur dioxide absorption solution, and the anode compartment electrolyte is a sodium hydroxide solution. The sulfur dioxide absorption solution is a solution obtained by absorbing sulfur dioxide using a conventional alkaline solution, such as a sodium sulfite solution obtained by absorbing sulfur dioxide using a sodium hydroxide solution.

[0011] As a preferred embodiment, the porous hydrophobic substrate comprises hydrophobic carbon paper, a polytetrafluoroethylene membrane, or a metal membrane with a hydrophobic surface treatment; the catalytic material comprises metal nanoparticles of at least one of lead, copper, cobalt, iron, nickel, gold, silver, platinum, and palladium. The gas diffusion electrode utilizes the hydrophobic carbon paper, polytetrafluoroethylene membrane, or metal membrane with a hydrophobic surface treatment as the substrate, and the catalytic material is deposited on the surface of the porous hydrophobic substrate by methods such as drop coating, spray coating, and vapor deposition.

[0012] As a preferred solution, the catalyst loading amount of the catalytic material on the surface of the porous hydrophobic substrate is 0.1 to 3 mg / cm 2 .

[0013] As a preferred solution, the electrolyte flow rate in the anode chamber and cathode chamber of the dual-electrode flow electrolytic cell is controlled within the range of 10-30 mL / min, the cell voltage is controlled within the range of 0.1-10 V, and the electrode current is controlled within the range of 0.1-250 mA.

[0014] As a preferred solution, the anode and cathode chambers of the electrolytic cell are separated by a proton membrane or a bipolar membrane, and an inert gas such as Ar or He is introduced into the gas diffusion chamber as a carrier gas. The schematic diagram of the dual-electrode flow electrolytic cell device is shown in FIG. Figure 1 shown.

[0015] Compared with the prior art, the technical solution of the present invention brings the following beneficial technical effects:

[0016] The present invention effectively solves technical problems such as unstable and high cell pressure during the electrochemical reduction of sulfur dioxide to produce hydrogen sulfide using a dual-electrode flow electrolytic cell by filling the cathode chamber electrolyte channel with a cation exchange resin. By filling the cathode chamber of the dual-electrode flow electrolytic cell with a cation exchange resin, the proton-exchanging properties of the cation exchange resin are utilized to alleviate the problem of local pH elevation on the electrode surface, improve mass transfer in the SO2 electrochemical reduction reaction, and significantly reduce the impact of bubbles on the electrode surface. This method is simple and can significantly increase the current density of the electrocatalytic reduction of SO2 to H2S, significantly reduce the reaction cell pressure, and significantly improve the stability of the cell pressure. The electrolysis energy consumption is low, and the resin cost is low, which is conducive to large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the structure of a two-electrode flow electrolytic cell.

[0018] Figure 2 Schematic diagram of cation exchange resin filling, a) resin filling is excessive; b) resin filling is moderate; c) resin filling is insufficient; among them, the yellow balls represent cation exchange resin, and the black rectangles are gas diffusion electrodes.

[0019] Figure 3 Schematic diagram of the preparation of gas diffusion electrodes by spraying method (spray gun spraying).

[0020] Figure 4 To compare the cell voltage stability of Example 1 with Example 1 and Example 2 in the constant current (-200 mA) electrolysis of sulfur dioxide to produce hydrogen sulfide. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below with reference to specific embodiments. However, the protection scope of the claims of the present invention is not limited to the scope of the embodiments.

[0022] The two-electrode flow electrolysis cell involved in the following examples is as follows Figure 1 As shown:

[0023] The dual-electrode flow electrolytic cell uses nickel foam as the anode and a gas diffusion electrode as the cathode. The cathode chamber and the anode chamber are separated by a commercially available FBM-PK bipolar membrane. The cathode chamber electrolyte is a sodium sulfite solution obtained by absorbing sulfur dioxide with sodium hydroxide, and the anode chamber electrolyte is a sodium hydroxide solution. The cathode chamber electrolyte is filled with a cation exchange resin, and Ar gas is introduced into the gas diffusion chamber of the dual-electrode flow electrolytic cell as a carrier gas.

[0024] The preparation method of the gas diffusion electrode adopts the common spraying method in the prior art, specifically as follows Figure 3 As shown in the figure, commercial copper nanoparticle catalysts of different masses were weighed and ultrasonically dispersed into an ethanol aqueous solution until the nanoparticles were evenly dispersed and the concentration was about 10 g / L. The catalyst was loaded on a cut hydrophobic carbon paper with a fixed area by spraying with a gun to prepare a gas diffusion electrode to obtain a loading of 0.1 to 3 mg / cm 2 catalyst.

[0025] The cation exchange resins used in the following examples were pretreated by soaking them in 3% by mass dilute hydrochloric acid for 24 hours. The particle size of the cation exchange resins was 0.315 to 1.25 mm.

[0026] Unless otherwise specified in the following examples, the chemical reagents used are conventional commercially available products and are of analytical grade.

[0027] Comparative Example 1

[0028] Na2SO3 solution (converted to SO2 is 0.1mol / L) is used as the cathode electrolyte, and NaOH solution (1.5mol / L) is used as the anolyte. The cathode electrolyte (flow rate 10mL / min) and the anolyte (flow rate 30mL / min) are continuously pumped into the flow electrolytic cell using a peristaltic pump. No resin is filled, and the Ar gas flow rate in the gas diffusion cell is 2.5mL / min. With a copper loading of 1mg / cm 2 The gas diffusion electrode (Cu@CFP) was used as the working electrode, the reduction current was -200 mA, the average cell voltage was -5.87 V, and the voltage fluctuated greatly due to the influence of bubbles ( Figure 4 ).

[0029] Example 1

[0030] Na2SO3 solution (converted to SO2 of 0.1 mol / L) was used as the cathode electrolyte, and NaOH solution (1.5 mol / L) was used as the anolyte. The cathode electrolyte (flow rate 10 mL / min) and anolyte (flow rate 30 mL / min) were continuously pumped into the flow electrolysis cell using a peristaltic pump. The cathode electrolyte channel was filled with strongly acidic 732 sodium-type ion exchange resin with a resin filling amount of 0.5 g / cm 3 The Ar gas velocity in the gas diffusion cell was 2.5 mL / min. The copper loading was 1 mg / cm 2 The gas diffusion electrode (Cu@CFP) was used as the working electrode, the reduction current was -200 mA, the average cell voltage was -4.53 V, and the voltage was affected by bubbles and became smaller ( Figure 4 ).

[0031] Example 2

[0032] Na2SO3 solution (converted to SO2 of 0.1 mol / L) was used as the cathode electrolyte, and NaOH solution (1.5 mol / L) was used as the anolyte. The cathode electrolyte (flow rate 10 mL / min) and anolyte (flow rate 30 mL / min) were continuously pumped into the flow electrolysis cell using a peristaltic pump. The cathode electrolyte channel was filled with strongly acidic 732 hydrogen-type ion exchange resin with a resin filling amount of 0.5 g / cm 3 The Ar gas velocity in the gas diffusion cell was 2.5 mL / min. The copper loading was 1 mg / cm 2 The gas diffusion electrode (Cu@CFP) was used as the working electrode, the reduction current was -200 mA, the average cell voltage was -4.53 V, and the voltage was affected by bubbles and became smaller ( Figure 4 ).

[0033] Comparative Example 2

[0034] Na2SO3 solution (converted to SO2 is 0.1mol / L) is used as the cathode electrolyte, and NaOH solution (1.5mol / L) is used as the anolyte. The cathode electrolyte (flow rate 10mL / min) and the anolyte (flow rate 30mL / min) are continuously pumped into the flow electrolytic cell using a peristaltic pump. No resin is filled, and the Ar gas flow rate in the gas diffusion cell is 2.5mL / min. With a copper loading of 1mg / cm 2 The gas diffusion electrode (Cu@CFP) was used as the working electrode, the reduction current was -250 mA, and the average cell voltage was -6.62 V.

[0035] Example 3

[0036] Na2SO3 solution (converted to SO2 of 0.1 mol / L) was used as the cathode electrolyte, and NaOH solution (1.5 mol / L) was used as the anolyte. The cathode electrolyte (flow rate 10 mL / min) and anolyte (flow rate 30 mL / min) were continuously pumped into the flow electrolysis cell using a peristaltic pump. The cathode electrolyte channel was filled with strongly acidic 732 hydrogen-type ion exchange resin with a resin filling amount of 0.5 g / cm 3 The Ar gas velocity in the gas diffusion cell was 2.5 mL / min. The copper loading was 1 mg / cm 2 The gas diffusion electrode (Cu@CFP) was used as the working electrode, the reduction current was -250 mA, and the average cell voltage was -5.09 V.

[0037] Example 4

[0038] Na2SO3 solution (converted to SO2 of 0.1 mol / L) was used as the cathode electrolyte, and NaOH solution (1.5 mol / L) was used as the anolyte. The cathode electrolyte (flow rate 10 mL / min) and anolyte (flow rate 30 mL / min) were continuously pumped into the flow electrolysis cell using a peristaltic pump. The cathode electrolyte channel was filled with strongly acidic 732 hydrogen-type ion exchange resin with a resin filling amount of 0.2 g / cm 3 The Ar gas velocity in the gas diffusion cell was 2.5 mL / min. The copper loading was 1 mg / cm 2 The gas diffusion electrode (Cu@CFP) was used as the working electrode, the reduction current was -250 mA, and the average cell voltage was -6.37 V.

Claims

1. A method for producing hydrogen sulfide by electrochemical reduction of sulfur dioxide using a dual-electrode flow electrolytic cell, characterized in that: In the process of electrochemically reducing sulfur dioxide to produce hydrogen sulfide using a double-electrode flow electrolytic cell, a cation exchange resin is filled in the cathode chamber of the double-electrode flow electrolytic cell; the cation exchange resin is at least one of a strongly acidic 732 hydrogen-type cation exchange resin and a strongly acidic 732 sodium-type ion exchange resin.

2. The method for producing hydrogen sulfide by electrochemical reduction of sulfur dioxide using a dual-electrode flow electrolytic cell according to claim 1, wherein: The filling amount of the cation exchange resin is 0.1~2 g / cm 3 .

3. The method for producing hydrogen sulfide by electrochemical reduction of sulfur dioxide using a dual-electrode flow electrolytic cell according to claim 2, wherein: The particle size of the cation exchange resin is 0.315-1.25 mm.

4. The method for preparing hydrogen sulfide by electrochemical reduction of sulfur dioxide using a dual-electrode flow electrolytic cell according to claim 1 or 3, characterized in that: The cation exchange resin is pretreated by the following method: soaking in dilute hydrochloric acid with a mass percentage concentration of 2% to 5% for 18 to 30 hours.

5. The method for preparing hydrogen sulfide by electrochemical reduction of sulfur dioxide using a dual-electrode flow electrolytic cell according to claim 1 or 3, characterized in that: The dual-electrode flow electrolysis cell uses an inert metal as an anode and a gas diffusion electrode as a cathode. The cathode chamber and the anode chamber are separated by a proton membrane or a bipolar membrane. The gas diffusion electrode comprises a porous hydrophobic matrix and a catalytic material on its surface. The electrolyte in the cathode chamber is a sulfur dioxide absorption solution, and the electrolyte in the anode chamber is a sodium hydroxide solution.

6. The method for preparing hydrogen sulfide by electrochemical reduction of sulfur dioxide using a dual-electrode flow electrolytic cell according to claim 5, characterized in that: The porous hydrophobic substrate includes hydrophobic carbon paper, polytetrafluoroethylene membrane or metal membrane with hydrophobic surface treatment; The catalytic material comprises metal nanoparticles of at least one of lead, copper, cobalt, iron, nickel, gold, silver, platinum and palladium.

7. The method for preparing hydrogen sulfide by electrochemical reduction of sulfur dioxide using a dual-electrode flow electrolytic cell according to claim 6, characterized in that: The loading amount of the catalytic material on the surface of the porous hydrophobic substrate is 0.1~3 mg / cm 2 .

8. The method for producing hydrogen sulfide by electrochemical reduction of sulfur dioxide using a dual-electrode flow electrolytic cell according to claim 1, wherein: The electrolyte flow rates in the anode chamber and cathode chamber of the dual-electrode flow electrolytic cell are controlled within the range of 10-30 mL / min, and the cell voltage is controlled within the range of 0.1-10 V.

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