Diaphragm Electrolysis Cell For Preparing Raw Material For Phosgene Synthesis By Electrolysis Of Carbon Dioxide

The conversion of carbon dioxide into high value chemicals has attracted great interest in chemical industry.However,owing to the lack of efficient technology,no breakthrough has been achieved in this field.In this work,we sough to construct a novel electrolysis cell for carbon dioxide reduction to carbon monoxide in organic electrolyte,with chlorine produced as by-products.The obtained carbon monoxide and chlorine can be used as feedstock to produce phosgene.Phosgene can be further used as a feedstock to produce high-value down-stream products.Our research will focus on the following aspects:(1)We have constructed a membrane electrolysis cell for CO₂ reduction to CO in Bu₄NClO₄/PC,with Cl₂ produced on the anode from HCloxidized in aqueous solution.Using Nafion membrane to separate the cathodic chamber from the anodic chamber.Tetrabutyl ammonium perchlorate/propylene carbonate(Bu₄NClO₄/PC)was served as the catholyte,HClaqueous solution was served as the anolyte,An Au foil was employed as the cathode,and a graphite rod was employed as the anode,and the H-type diaphragm electrolytic cell was composed.In the process of electrolytic reaction,HClwas oxidized on the anode to generate Cl₂.H⁺in the anode chamber pass through the ion exchange membrane and enter the cathode chamber to participate in CO₂ electroreduction reaction and generate CO.(2)The kinetic characteristics of the electro-reduction reaction of CO₂ in 0.1M Bu₄NClO₄/PC were analyzed.According to the gas chromatography test results,CO₂ can be reducted to CO on the cathode.Constant potential electrolysis was conducted at-2.241V(vs.SHE)on the cathode.The current density reached 6.42 mA·cm^-2,and the Faradaic efficiency of CO formation stabilized at 88.4%.The results of the 5h long-term electrolysis experiment shows that the electrode is not poisoned,the organic electrolyte does not deteriorate,and the performance of the proton exchange membrane does not degrade.(3)The kinetics of the oxidation reaction of HClon the anode was studied,and the anode gas products were analyzed by iodine titration.The results showed that HClcan be electrooxidized on the anode to generate Cl₂.In 18 wt%HClaqueous solution,the detected current density reached to 2.21 mA·cm^-2 at 1.360V(vs.SHE),with the Faraday efficiency of Cl₂ formation maintained77.8%.(4)In order to improve the performance of the electrolyzer,we have optimized the concentration of the catholyte and anolyte.When the catholyte concentration was 0.3M and the anolyte solution was 22 wt%,the current density of CO generated was reached 15.42 mA·cm^-2,and the current efficiency was increased to 92.23%.The current density of Cl₂ was reached 2.53mA·cm^-2,and the current efficiency was increased to 82.5%.(5)We have constructed a multi-chamber diaphragm electrolytic cell,carried out expanded experiments,and compared with other mainstream technologies.It is believed that the multi-chamber diaphragm electrolytic cell proposed in this paper has the advantages of simple operation method,high product added value,and strong industrial applicability.The phosgene chemical industry and the field of CO₂ emission reduction have broad industrial application prospects.