Ethylene epoxidation in a low-temperature dielectric barrier discharge system

Abstract

Since ethylene oxide is a valuable chemical feedstock in producing many industrial chemicals, 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 dielectric barrier discharge (DBD) was initially studied to find the optimum operating conditions and then was compared with that under a corona discharge with various reported catalytically active catalysts. For the DBD system, it was found that the ethylene oxide yield decreased. with increasing O2/C2H4 molar ratio, feed flow rate, input frequency, and electrode gap distance, while the ethylene oxide yield increased with increasing applied voltage up to 19 kV. The highest ethylene oxide yield of 5.62% was obtained when an input frequency of 500 Hz and an applied voltage of 19 kV were used, with an O2/C2H4 molar ratio of 1/1, a feed flow rate of 50 cm3/min, and an electrode gap distance of 10 mm. Under these optimum conditions, the power consumption was found to be 6.07xl0-16 Ws/molecule of ethylene oxide produced. When comparing with the corona discharge system with 0.2 wt.% Au-12.5 wt.% Ag/(low-surface-area) a-Al2O3 catalyst exhibiting comparative good epoxidation performance, the DBD system still provided the better performance in terms of C2H4 conversion, C2H4O yield, and power consumption per C2H4O molecule produced