Ethylene epoxidation in a low-temperature dielectric barrier discharge system: effect of electrode geometry

Abstract

Ethylene oxide is a valuable chemical feedstock in producing many industrial chemicals, such as ethylene glycol, solvents, antifreezes, and adhesives. Hence, the partial oxidation of ethylene to ethylene oxide, so-called ethylene epoxidation, has been of great interest in many global research studies. In this work, the epoxidation of ethylene under a cylindrical dielectric barrier discharge (DBD) reactor was initially studied to find the optimum operating conditions and then was compared with that under a parallel DBD reactor. For the cylindrical DBD system, it was found that the ethylene oxide yield increased with decreasing O₂/C₂H₄ molar ratio, under the O₂ -lean condition, and decreasing feed flow rate; however, there were optimum applied voltage and input frequency to obtain the highest ethylene oxide yield. The highest ethylene oxide yield of 2.41% was achieved when an O₂/C₂H₄ molar ratio of 0.25:1 (1:4), an applied voltage of 15 kV, an input frequency of 500 Hz, a feed flow rate of 50 cm³/min, and electrode gap distance of 5 mm were used. Under these optimum conditions, the power consumption was found to be 12.72x10¹⁶ Ws/molecule of ethylene oxide produced. The optimum conditions were used to comparatively investigate the epoxidation performance with the parallel DBD system. It was found that at the optimum conditions, the cylindrical DBD system still exhibited higher epoxidation performance. Therefore, the cylindrical DBD system was found to exhibit a high potential to produce ethylene oxide from ethylene epoxidation reaction.