Ethylene Epoxidation in AC Dielectric Barrier Discharge Over Silver-Based Catalysts with Different Second Metals

Plasma Chemistry and Plasma Processing - This work was to investigate the effects of Ag-based catalysts and the addition of a second metal (Sn or Cu) loaded on an 0.1% wt% Ag catalyst on the...     

Influence of Operating Parameters,Al2O3 and Ni/Al2O3 Catalysts on Plasma-Assisted CO2 Reforming of CH4 in a Parallel Plate Dielectric Barrier Discharge for High H2/CO Ratio Syngas Production

Plasma Chemistry and Plasma Processing - This work aimed to investigate plasma-assisted CO2 reforming of CH4 in a parallel plate dielectric barrier discharge (DBD) system for production of high...     

Ethylene Epoxidation in Low-Temperature AC Dielectric Barrier Discharge: Effect of Electrode Geometry

In this work, the epoxidation of ethylene under a cylindrical dielectric barrier discharge (DBD) reactor and a parallel DBD reactor was comparatively studied. The effects of important operating parameters—feed O₂/C₂H₄ molar ratio, applied voltage, input frequency, and residence time—were investigated on the reaction performance in terms of reactant conversions, product selectivities, product yields, and power consumptions per molecule of ethylene converted and per molecule of ethylene oxide produced. The optimum conditions obtained from the operating parameter investigation were used for a comparative performance evaluation of both DBD reactor systems. It was found that under the optimum conditions of each system, the cylindrical DBD system exhibited superior epoxidation performance for ethylene oxide production compared to the parallel DBD system, indicating that the electrode geometry (electrode edge length-to-electrode surface area ratio) plays a significant role in the ethylene epoxidation.     

Ethylene Epoxidation in an AC Dielectric Barrier Discharge Jet System

In this work, ethylene epoxidation was investigated in a dielectric barrier discharge jet (DBDJ) with a separate ethylene/oxygen feed under oxygen lean conditions. The ethylene (C₂H₄) stream was directly injected behind the plasma zone in order to reduce all undesired reactions, including C₂H₄ cracking and further reactions, while the oxygen (O₂) balanced with argon was fed through the plasma zone totally to maximize the formation of active oxygen species. The effects of various operating parameters, such as total feed flow rate, O₂/C₂H₄ feed molar ratio, applied voltage, input frequency, and C₂H₄ feed position on the ethylene epoxidation activity, were investigated to determine the optimum operating conditions for this new DBDJ system. The highest ethylene oxide (EO) selectivity (55.2 %) and yield (27.6 %), as well as the lowest power consumption (3.3 × 10^?21 and 6.0 × 10^?21 Ws/molecule C₂H₄ converted and EO produced, respectively) were obtained at a total feed flow rate of 1,625 cm³/min (corresponding to a residence time of 0.022 s), an O₂/C₂H₄ feed molar ratio of 0.25:1, an applied voltage of 9 kV, an input frequency of 300 Hz, and a C₂H₄ feed position of 3 mm behind the plasma zone. The superior activity of the ethylene epoxidation in the DBDJ system resulted from a small reaction volume as well as a separate ethylene/oxygen feed.     

Ethylene Epoxidation over Alumina- and Silica-Supported Silver Catalysts in Low-Temperature AC Dielectric Barrier Discharge

In this work, ethylene epoxidation reaction for ethylene oxide production over silver catalysts loaded on two different supports (silica and alumina particles) in a low-temperature AC dielectric barrier discharge (DBD) reactor was investigated. The DBD plasma system was operated under the following base conditions: an O₂/C₂H₄ feed molar ratio of 1/4, a total feed flow rate of 50 cm³/min, an electrode gap distance of 0.7 cm, an input frequency of 500 Hz, and an applied voltage of 19 kV. From the results, the presence of silver catalysts improved the ethylene oxide production performance. The silica support interestingly provided a higher ethylene oxide selectivity than the alumina support. The optimum Ag loading on the silica support was found to be 20 wt%, exhibiting the highest ethylene oxide selectivity of 30.6%.     

Ethylene Epoxidation in Cylindrical Dielectric Barrier Discharge: Effects of Separate Ethylene/Oxygen Feed

The effects of separate C₂H₄/O₂ feed and C₂H₄ feed position on the ethylene epoxidation reaction in an AC cylindrical dielectric barrier discharge reactor were investigated. The highest EO selectivity of 34?% and EO yield of 7.5?%, as well as the lowest power consumption of 1.72?×?10^?16 Ws/molecule of EO produced, were obtained at a C₂H₄ feed position of 0.25, an O₂/C₂H₄ feed molar ratio of 1/4, an applied voltage of 13?kV, an input frequency of 550?Hz, and a total feed flow rate of 75?cm³/min. The results demonstrated, for the first time, that the separate feed of C₂H₄ and O₂ could provide better ethylene epoxidation performance in terms of higher EO selectivity and yield, and lower power consumption, as compared to the mixed feed. All undesired reactions including C₂H₄ cracking, dehydrogenation, oxidation, and coupling reactions are lowered by the ethylene separate feed because of a decrease in opportunity of ethylene molecules to be activated by generated electrons.