The Influence of Supercritical Carbon Dioxide (SC-CO2) on Electrolytes and Hydrogenation of Soybean Oil

The electrochemical hydrogenation of soybean oil with supercritical carbon dioxide (SC-CO2) has been studied to seek ways for substantial reduction of the trans fatty acids (TFA). The solubility of CO2 in electrolytes and the conductivity of electrolytes were investigated using a self-made electrochemical hydrogenation reactor. The optimum hydrogenation parameters were assessed. Both the solubility of CO2 in electrolytes and the conductivity of electrolytes increased with increasing CO2 pressure. When the pressure reached a critical point of CO2, the solubility of CO2 expressed as a mole fraction was 0.42 in cathode electrolyte and 0.1 in anode electrolyte. At 8 MPa, the conductivity of electrolytes was 1.5 times higher than that at 2 MPa. When the pressure was higher than the critical point of CO2, the solubility of CO2 in electrolytes and the conductivity of electrolytes reached a stable value. The optimum condition for electrochemical hydrogenation of soybean oil in SC-CO2 were reaction pressure (8 MPa), reaction temperature (48 °C), current (125 mA), agitation speed (300 rpm), and reaction time (8 h). Fatty acid profile, iodine value, and TFA content were evaluated at the optimum parameters. This investigation showed that the electrochemical hydrogenation of soybean oil in SC-CO2 was improved. The reaction time was shortened by 4 h, and TFA content was reduced by 35.8% compared to traditional hydrogenation process.