System and method for preparing ethylene or synthesis gas by electrolyzing carbon dioxide

Abstract

The invention discloses a system and a method for preparing ethylene or synthesis gas by electrolyzing carbon dioxide, and belongs to the technical field of electrochemistry, the system comprises a carbon dioxide electrolytic cell, a cathode gas inlet system, a cathode gas purification system, a cathode catalytic electrode regeneration system, an anode circulating system, an anode gas-liquid separation system and a power supply. By adding the in-situ regeneration system to the cathode catalytic electrode, the service life of the original catalytic electrode and the whole system can be prolonged by more than 10 times; the control system verified by combining test and simulation can regenerate the catalytic electrode and the electrolysis system in real time, so that the continuous and stable operation of the whole electrolysis system is realized, and the service life of the system device is further prolonged. The whole set of system device improves the comprehensive utilization rate of the electrolytic cell, and has important significance on large-scale industrial production.

Claims

1. A system for electrolyzing carbon dioxide to produce ethylene or syngas, characterized in that, It includes a carbon dioxide electrolyzer, a cathode gas inlet system, a cathode gas purification system, a cathode catalytic electrode regeneration system, an anode circulation system, an anode gas-liquid separation system and a power supply; Among them, the carbon dioxide electrolyzer is electrically connected to the power supply; the carbon dioxide electrolyzer includes a cathode chamber and an anode chamber, and a membrane electrode is provided between the cathode chamber and the anode chamber; the membrane electrode includes a diaphragm, a cathode catalyst and an anode catalyst, the cathode catalyst is located in the cathode chamber and fits one side of the diaphragm, and the anode catalyst is located in the anode chamber and fits the other side of the diaphragm; the diaphragm is located between the cathode catalyst and the anode catalyst; The cathode gas inlet system is communicated with the inlet of the cathode chamber, and the cathode gas purification system is communicated with the outlet of the cathode chamber; the inlet of the cathode catalytic electrode regeneration system is communicated with the outlet of the cathode chamber, and the outlet of the cathode catalytic electrode regeneration system is communicated with the inlet of the cathode chamber; The outlet of the anode circulation system is communicated with the inlet of the anode chamber, the outlet of the anode chamber is communicated with the inlet of the anode gas-liquid separation system, and the inlet of the anode circulation system is communicated with the liquid outlet of the anode gas-liquid separation system; a control valve is provided between the anode circulation system and the anode chamber.

2. The system for electrolyzing carbon dioxide to produce ethylene or syngas according to claim 1, wherein The cathode gas inlet system includes a CO2 storage tank and a humidifier, the CO2 storage tank is communicated with the humidifier, and the humidifier is communicated with the cathode chamber; a control valve, a flowmeter and a pressure gauge are sequentially provided between the humidifier and the cathode chamber.

3. The system for electrolyzing carbon dioxide to produce ethylene or syngas according to claim 2, wherein A control valve is provided between the cathode gas purification system and the cathode chamber; the cathode gas purification system includes a chromatographic detection device and a purification device; the chromatographic detection device and the purification device are connected in parallel and communicated with the outlet of the cathode chamber; The cathode catalytic electrode regeneration system includes a regeneration liquid storage tank and a regeneration liquid circulation pump; the regeneration liquid storage tank is communicated with the regeneration liquid circulation pump, the regeneration liquid storage tank is communicated with the outlet of the cathode chamber, and the regeneration liquid circulation pump is communicated with the flowmeter; a control valve is provided between the regeneration liquid storage tank and the cathode chamber, and a control valve is provided between the regeneration liquid circulation pump and the flowmeter.

4. The system for electrolyzing carbon dioxide to produce ethylene or syngas according to claim 1, wherein The electrode plate in the carbon dioxide electrolyzer is any one of a stainless steel electrode plate, a nickel electrode plate, a carbon electrode plate, a titanium electrode plate and an alloy electrode plate; The diaphragm is an anion exchange membrane, a cation exchange membrane or a composite diaphragm.

5. The system for electrolyzing carbon dioxide to produce ethylene or syngas according to claim 4, wherein The cathode catalyst is any one of a silver-based catalyst, a gold-based catalyst, a copper-based catalyst, a nickel-based catalyst, a bismuth-based catalyst, an iron-based catalyst, an alloy catalyst, and a single-atom catalyst; the loading amount of the cathode catalyst is 0.5-20.0 mg / cm 2 ; The anode catalyst is an oxygen evolution catalyst, and the loading amount of the anode catalyst is 0.2 - 12.0 mg / cm 2 .

6. The system for electrolyzing carbon dioxide to produce ethylene or syngas according to claim 3, wherein The regeneration solution in the regeneration liquid storage tank is any one of deionized water, a low-concentration salt solution, a low-concentration alkaline solution and a low-concentration acidic solution.

7. A method for electrolyzing carbon dioxide to produce ethylene or syngas, characterized in that, Using the system according to any one of claims 1-6, it includes the following steps: (1) Electrolysis: Pass humidified CO2 gas into the cathode chamber of the carbon dioxide electrolyzer, pass electrolyte into the anode chamber, keep warm for electrolysis, after the product on the anode side is separated from oxygen by gas-liquid separation, the electrolyte is circulated back to the anode chamber of the electrolyzer through the anode circulation system; the mixed gas of ethylene, hydrogen, carbon monoxide and unreacted carbon dioxide generated on the cathode side is analyzed by gas chromatography for composition and stored after subsequent separation; (2) Catalytic electrode regeneration: Adjust the protection voltage, close the carbon dioxide inlet valve and the outlet control valve of the cathode chamber, open the control valve of the cathode catalytic electrode regeneration system, start the regeneration liquid circulation pump, circulate and flush the catalytic electrode, then close the control valve of the cathode catalytic electrode regeneration system, and purge with CO2 to complete the regeneration of the catalytic electrode.

8. The method for electrolyzing carbon dioxide to produce ethylene or syngas according to claim 7, wherein The electrolyte described in step (1) is any one or a mixture of potassium carbonate, potassium bicarbonate, potassium hydroxide, sodium hydroxide, sodium carbonate, and sodium bicarbonate electrolytes, and the concentration of the electrolyte is 0.05 - 4.0 mol / L.

9. The method for electrolyzing carbon dioxide to produce ethylene or syngas according to claim 8, characterized in that, In step (1), the current density of electrolysis is 5 mA / cm 2 - 600 mA / cm 2 , the electrolysis voltage is 2.4 V - 4.5 V, and the electrolysis reaction temperature is 20°C - 90°C; The CO2 inlet rate during electrolysis is 0.1 - 5 mL / (min·cm 2 membrane electrode area).

10. The method for electrolyzing carbon dioxide to produce ethylene or syngas according to claim 7, wherein In step (2), during the regeneration process, the protection voltage is 0.3V - 1.6V, the regeneration temperature is 20 - 80°C, and the regeneration time is 10 min - 10 h; The purging time of the post-regenerated electrode with CO2 gas is 1 min - 5 h, and the CO2 inlet rate is 0.1 - 5 mL / (min·cm 2 membrane electrode area).

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