Ethylene epoxidation in a low-temperature parallel plate dielectric barrier discharge system: effects of ethylene feed position and Ag/SiO₂ catalyst existence

Abstract

Ethylene oxide (C2H4O, EO) is the valuable chemical feedstock or intermediate for many important applications, such as solvents, antifreeze, textiles, detergents, adhesives, polyurethane foam, and pharmaceuticals. Ethylene oxide is a colorless flammable gas or refrigerated liquid with a faintly sweet odor and is the simplest molecule of an epoxide. The partial oxidation of ethylene to ethylene oxide, so-called ethylene epoxidation, has been of great interest in many global research works. The objective in this work was to investigate the ethylene epoxidation performance using a parallel plate dielectric barrier discharge (DBD) system by initially producing oxygen active species prior to reacting with ethylene. The effects of various operating parameters, including ethylene feed position, oxygen-to-ethylene feed molar ratio, Ag/SiO2 catalyst existence, applied voltage, input frequency, and feed flow rate on the ethylene epoxidation activity were examined. It was found that the highest EO selectivity of 72 % was obtained when the DBD was operated at an ethylene feed position fraction of 0.5, an O2/C2H4 feed molar ratio of 0.2:1, the presence of Ag loading of 10 %, an applied voltage of 19 kV, an input frequency of 500 Hz, and a total feed flow rate of 50 cm3/min. At these optimum conditions, the power consumption to create an EO molecule was found to be as low as 16.56×10-16 Ws /molecule of E0 produced. Moreover, the presence of Ag catalyst loaded on SiO2 provided a much higher EO selectivity (%) as twice as compared with the sole plasma system.