Electrochemical degradation and value-added conversion method for sulfur hexafluoride waste gas

Abstract

The invention discloses a sulfur hexafluoride waste gas electrochemical degradation and value-added conversion method, and belongs to the technical field of electrochemistry and environmental engineering. The method comprises the following steps: preparing a nano-metal modified graphite electrode; placing the obtained nano-metal modified graphite electrode in an electrolyte, and activating by taking a platinum sheet as a counter electrode; the activated nano-metal modified graphite electrode is used as a working electrode to be placed in an H-type electrolytic tank, an electrolyte is added, sulfur hexafluoride gas containing oxygen is introduced, and electrolysis is performed, so that the electrochemical system for efficiently degrading SF6 at normal temperature and normal pressure can be obtained, directional conversion of SF6 to a high-added-value fluorine / sulfur-containing chemical product is realized, secondary pollution is avoided, and the electrochemical system is suitable for industrial production. The catalytic activity and the anti-fluorination capability of the electrode material are improved, and the service life of the system is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of electrochemistry and environmental engineering technology, specifically relating to an electrochemical system and method for degrading sulfur hexafluoride waste gas and converting it into high-value-added chemicals. Background Technology

[0002] Sulfur hexafluoride (SF6) is widely used in power equipment due to its excellent insulating properties, but it has an extremely high global warming potential and an atmospheric lifetime of up to 3200 years. Existing treatment technologies include gas recovery, adsorption, pyrolysis, plasma, and photocatalysis, but these generally suffer from high energy consumption, low efficiency, and severe secondary pollution. For example, Chinese patent application CN119874465A developed a method for preparing fluorinated diphenylmethane compounds using SF6 as a fluorine source via photocatalysis. This method is reported to have mild reaction conditions and inexpensive and readily available raw materials. However, photocatalytic processes typically suffer from inherent drawbacks such as low reaction efficiency and long reaction times (usually several hours to tens of hours), which limits their efficiency and economic viability on an industrial scale.

[0003] Chinese patent application CN117466703A discloses a method for synthesizing phenylpropynyl fluoride compounds from sulfur hexafluoride. This method is similar to the aforementioned patented technology, employing a blue light-excited photocatalytic system to extend the substrate to phenylpropynyl alcohol compounds, and emphasizing its advantages of simple operation and good substrate adaptability. However, this technology also faces inherent bottlenecks in photocatalytic reaction pathways, namely, the reaction time is typically long, and energy utilization efficiency and space-time yield need further improvement, making it difficult to meet the requirements of large-scale continuous production.

[0004] In recent years, the electrochemical conversion of SF6 into high-value-added fluorinated chemicals has become an important research direction in this field. In 2022, Pavel Nagorny et al. reported an electrochemical synthesis method using SF6 as a fluorinating agent, successfully preparing 17 glycosyl fluorides with a yield of up to 98%. Mechanistic studies showed that SF6 is reduced at the cathode to produce fluorinated intermediates (such as SF4). Simultaneously, zinc ions generated by zinc anodic oxidation effectively capture sulfur and fluorine byproducts in the reaction, forming harmless zinc salts and thus avoiding secondary pollution. This work pioneered the use of SF6 waste gas for organic electrosynthesis; however, its applicable substrate types are relatively limited, mainly focusing on glycosyl fluorides, failing to fully demonstrate the potential of SF6 in the synthesis of other high-value fluorinated chemicals. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to provide a method for the electrochemical degradation and conversion of sulfur hexafluoride.

[0006] The present invention solves the above-mentioned technical problems through the following technical means: This invention proposes a method for the electrochemical degradation and conversion of sulfur hexafluoride, comprising the following steps: (1) A suspension is formed by uniformly mixing nano-transition metal oxide, 4-bromoboronic acid diazonium phenyl tetrafluoroborate and inorganic acid; the graphite electrode is immersed in the suspension and allowed to stand, then m-porphyrin dimethyl ester and cobalt acetate are added and the immersion continues; the electrode is removed and dried under an inert atmosphere to obtain a nano-metal modified graphite electrode. (2) The graphite electrode modified with nano-metal obtained in (1) was placed in an electrolyte and activated with a platinum sheet as the counter electrode; (3) Place the activated nano-metal-modified graphite electrode as the working electrode in an H-type electrolytic cell, add electrolyte, and pass in sulfur hexafluoride gas containing oxygen to carry out electrolysis.

[0007] Preferably, the ratio of the nano-transition metal oxide, 4-bromoboronic acid diazonium benzoate tetrafluoroborate, and sulfuric acid is 0.3~0.8g:0.05~0.4g:7~15mL; more preferably, it is 0.5g:0.1g:10mL.

[0008] Preferably, the mass ratio of the nano-transition metal oxide, m-porphyrin dimethyl ester, and cobalt acetate is (0.3~0.8):(0.03~0.07):(0.01~0.04); more preferably, it is 0.5:0.05:0.02.

[0009] Preferably, the nano-transition metal oxide is one or a mixture of copper oxide, zinc oxide, cerium oxide, cobalt oxide, titanium oxide, nickel oxide, and zirconium oxide.

[0010] Preferably, the particle size of the nano-transition metal oxide is 20~80nm.

[0011] Preferably, the inorganic acid is one or a mixture of sulfuric acid, nitric acid, and hydrochloric acid.

[0012] Preferably, the standing period is: standing at 35~45℃ for 44~52 h; more preferably at 40℃ for 50 h.

[0013] Preferably, in (2) and (3), the electrolyte is composed of an electrolyte and an organic solvent; the electrolyte is one or a mixture of 4-bromoboronic acid diazonium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, tetrabutylammonium perchlorate, and tetrabutylammonium hexafluorophosphate; the organic solvent in the electrolyte is one or a mixture of acetonitrile, ethanol, methanol, ethylenediamine, tetrahydrofuran, and N,N-dimethylformamide.

[0014] Preferably, the activation conditions are: activation at 2~4 V for 20~40 min, more preferably 3 V for 30 min.

[0015] Preferably, the oxygen-containing sulfur hexafluoride gas is SF6 gas containing 0.5-1.5% O2 by volume; more preferably, it is 1%.

[0016] Preferably, the concentration of the sulfur hexafluoride gas is 800~1200 ppm; more preferably 1000 ppm.

[0017] Preferably, in (3), the conditions for electrolysis are: 2~6 V, 25~35℃, 2~6h; more preferably 4 V, 30℃, 2.5h.

[0018] The beneficial effects of this invention are as follows: 1. This invention develops an electrochemical value-added conversion method for SF6 that can handle complex substrates and has both high efficiency and good economic benefits, so as to achieve efficient, low-energy consumption and no secondary pollution of SF6 degradation and resource conversion.

[0019] 2. This invention provides an electrochemical system for the efficient degradation of SF6 at room temperature and pressure, realizing the directional conversion of SF6 into high-value-added fluorine / sulfur-containing chemicals, avoiding secondary pollution, improving the catalytic activity and anti-fluorination ability of electrode materials, and extending the service life of the system.

[0020] 3. This invention achieves efficient degradation of SF6 at room temperature and pressure, with controllable products that can be directionally synthesized into high-value-added fluorine-containing chemicals. Electrodes synthesized using this invention exhibit high resistance to fluorination and can be reused without secondary pollution after electrochemical regeneration, aligning with the principles of green chemistry and a circular economy.

[0021] Of course, implementing any product or method of the present invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0022] Figure 1 This is a scanning electron microscope image of the electrode material in Embodiment 1 of the present invention; Figure 2 This is a linear scanning voltammetry curve diagram from Embodiment 1 of the present invention; Figure 3 This is a timing current curve diagram from Embodiment 1 of the present invention; Figure 4 This is a graph showing the degradation rate of the product in Example 1 of the present invention; Detailed Implementation To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art.

[0023] Unless otherwise specified, the test materials and reagents used in the following examples are commercially available or prepared by known methods.

[0024] Unless otherwise specified, all techniques or conditions described in the embodiments can be performed in accordance with the techniques or conditions described in the literature in this field or in the product manual. Unless otherwise specified, the quantitative experiments in the following embodiments are all repeated three times or more, and the results are averaged.

[0025] Example 1: A method for the electrochemical degradation and conversion of sulfur hexafluoride includes the following steps: (1) Take 0.5 g of nano-copper oxide powder (20~80 nm), add 10 mL of 10% (v / v) sulfuric acid solution and 0.1 g of 4-bromoboronic acid diazonium tetrafluoroborate, and stir for 30 minutes to form a uniform suspension. Immerse the graphite electrode (10 mm in diameter) in the suspension and let it stand at 40 °C for 48 hours. Add 0.05 g of m-porphyrin dimethyl ester and 0.02 g of cobalt acetate, and continue to soak at 40 °C for 48 hours. Take out the electrode and dry it at 80 °C under a nitrogen atmosphere to obtain a nano-metal-modified graphite electrode. (The scanning electron microscope image of the prepared nano-metal-modified graphite electrode material shows that the metal distribution on the surface of the prepared sample is uniform.) (2) The reactor was selected as a flow cell. The graphite electrode modified with nano-metals obtained in (1) was placed in an acetonitrile solution containing 0.1 M tetrabutyltetrafluoroborate ammonium, with a platinum sheet as the counter electrode, and activated at 3 V for 30 minutes. (After activation, the linear sweep voltammetry curve was tested, and the results are as follows) Figure 2 As shown, there is a current response to the electrochemical degradation of SF6. (3) The activated nano-metal-modified graphite electrode was placed in an H-type electrolytic cell as the working electrode. An electrolyte solution containing 0.1 M tetrabutyltetrafluoroborate in acetonitrile was added, and SF6 gas containing 1% O2 (initial concentration 1000 ppm) was introduced. Electrolysis was carried out (controlled voltage 4 V, temperature 30℃, reaction time 2.5 h). After the electrolysis reaction was completed, the gaseous products were qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry.

[0026] Depend on Figure 4 It can be seen that the degradation rate of SF6 is over 90%.

[0027] Example 2: The difference between this embodiment and Embodiment 1 is that: In step (1), the amount of nano copper oxide powder is 0.3g, the amount of 4-bromoboronic acid diazonium phenyl tetrafluoroborate is 0.05g, the amount of sulfuric acid solution is 7mL, the amount of m-porphyrin dimethyl ester is 0.3g, and the amount of cobalt acetate is 0.01g; the standing time is: standing at 45℃ for 44h; In step (2), activation is performed at 2V for 40 minutes; In step (3), SF6 gas containing 1.5% O2 (initial concentration 800 ppm) is introduced, and the electrolysis conditions are: 6 V, 25℃, 2h.

[0028] The rest is the same as in Example 1.

[0029] Example 3: The difference between this embodiment and Embodiment 1 is that: In step (1), the amount of nano copper oxide powder is 0.8g, the amount of 4-bromoboronic acid diazonium phenyl tetrafluoroborate is 0.4g, the amount of sulfuric acid solution is 10mL, the amount of m-porphyrin dimethyl ester is 0.07g, and the amount of cobalt acetate is 0.04g; the standing time is: standing at 35℃ for 52h; In step (2), activation is performed at 4V for 20 minutes; In step (3), SF6 gas containing 0.5% O2 (initial concentration 1200 ppm) is introduced, and the electrolysis conditions are: 2V, 35℃, 6h.

[0030] The rest is the same as in Example 1.

[0031] Example 4: The difference between this embodiment and Embodiment 1 is that: In step (1), sulfuric acid is replaced with nitric acid. In steps (2) and (3), the electrolyte is an ethanol solution of 4-bromoboronic acid diazonium tetrafluoroborate. The rest is the same as in Example 1.

[0032] Example 5: The difference between this embodiment and Embodiment 1 is that: In step (1), sulfuric acid is replaced with hydrochloric acid. In steps (2) and (3), the electrolyte is a tetrahydrofuran solution of tetrabutylammonium hexafluorophosphate; The rest is the same as in Example 1.

[0033] The methods in Examples 2-5 also showed good degradation and conversion effects on SF6 gas, with degradation rates similar to those in Example 1.

[0034] Comparative Example 1: The difference between this comparative example and Example 1 is that in step (1), the nano copper oxide powder is missing, while the rest is the same as in Example 1.

[0035] Results: After the reaction, the products were tested and analyzed, and the SF6 degradation rate was as low as 20%.

[0036] Comparative Example 2: The difference between this comparative example and Example 1 is that in step (3), SF6 gas without O2 is introduced, and the rest is the same as in Example 1.

[0037] Results: After the reaction, the product was tested and analyzed, and SF6 was reduced to below 30%.

[0038] Comparative Example 3: The difference between this comparative example and Example 1 is that in step (3), the electrolyte is an acetonitrile solution that does not contain tetrabutyltetrafluoroborate, while the rest is the same as in Example 1.

[0039] Results: After the reaction, the products were tested and analyzed, and the SF6 degradation rate was as low as less than 1%.

[0040] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for electrochemical degradation conversion of sulfur hexafluoride, characterized in that, It comprises the following steps: (1) uniformly mixing nano transition metal oxide, 4-bromoboronic acid diazonium benzene tetrafluoroborate and inorganic acid to form a suspension; immersing a graphite electrode in the suspension, standing, adding mesoporphyrin dimethyl ester and cobalt acetate, and continuing to soak; taking out the electrode, drying under an inert atmosphere, and obtaining a nano metal modified graphite electrode; (2) placing the nano metal modified graphite electrode obtained in (1) in an electrolyte, taking a platinum sheet as a counter electrode, and activating; (3) placing the activated nano metal modified graphite electrode as a working electrode in an H-type electrolytic cell, adding an electrolyte, and introducing oxygen-containing sulfur hexafluoride gas to perform electrolysis.

2. The method of claim 1, wherein, The nano transition metal oxide, 4-bromoboronic acid diazonium benzene tetrafluoroborate and sulfuric acid are used in a ratio of 0.3-0.8 g:0.05-0.4 g:7-15 mL.

3. The method of claim 1, wherein, The nano transition metal oxide, mesoporphyrin dimethyl ester and cobalt acetate are used in a mass ratio of (0.3-0.8):(0.03-0.07):(0.01-0.04).

4. The method of claim 1, wherein, The nano transition metal oxide is a mixture of one or more of copper oxide, zinc oxide, cerium oxide, cobalt oxide, titanium oxide, nickel oxide and zirconium oxide; the particle size of the nano transition metal oxide is 20-80 nm; and the inorganic acid is a mixture of one or more of sulfuric acid, nitric acid and hydrochloric acid.

5. The method of claim 1, wherein, The standing is standing at 35-45°C for 44-52 h.

6. The method of claim 1, wherein, In (2) and (3), the electrolyte is composed of an electrolyte and an organic solvent; the electrolyte is a mixture of one or more of 4-bromoboronic acid diazonium benzene tetrafluoroborate, tetrabutylammonium tetrafluoroborate, tetrabutylammonium perchlorate and tetrabutylammonium hexafluorophosphate; and the organic solvent in the electrolyte is a mixture of one or more of acetonitrile, ethanol, methanol, ethylenediamine, tetrahydrofuran and N,N-dimethylformamide.

7. The method of claim 1, wherein, The activation condition is: activating at a voltage of 2-4 V for 20-40 min.

8. The method of claim 1, wherein, The oxygen-containing sulfur hexafluoride gas is specifically SF6 gas containing 0.5-1.5% by volume of O2.

9. The method of claim 1, wherein, The concentration of the sulfur hexafluoride gas is 800-1200 ppm.

10. The method of claim 1, wherein, In (3), the electrolysis condition is: 2-6 V, 25-35°C, 2-6 h.

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