Study of the active phase of silver catalysts for ethylene epoxidation

Ethylene Epoxidation in Low-Temperature AC Dielectric Barrier Discharge: Effects of Oxygen-to-Ethylene Feed Molar Ratio and Operating Parameters

“…In comparisons, although the maximum EO yield of 5.6% obtained under the aforementioned best conditions (an O 2 /C 2 H 4 feed molar ratio of 1:1, a feed flow rate of 50 cm 3 / min, an input frequency of 500 Hz, an applied voltage of 19 kV, and an electrode gap distance of 10 mm) using the studied DBD system was lower than the EO yields of 30 and 10% obtained from the catalytic epoxidation process using 15 wt.% Ag/Al 2 O 3 at reaction temperatures of 280 and 350°C, respectively [15], the DBD system is still considered to exhibit a high potential to be employed for EO production under much lower operating temperatures. Again, the present work is the first time to demonstrate the use of the sole DBD system to synthesize EO without the presence of catalysts.…”

“…As shown in the aforementioned results, there were several reactions occurring in the plasma reaction zone so it is not possible to easily carry out the kinetic consideration of the ethylene epoxidation reaction. Future works will then be focused on the combination of the low-temperature DBD system with various reported catalytically active catalysts used in the conventional catalytic process, especially Ag/Al 2 O 3 -based catalysts [5][6][7][8][9][10][11][12][13][14][15]20], aiming to enhance the EO yield. The comparative study of ethylene epoxidation under different kinds of lowtemperature plasma discharges, such as corona discharge system with pin and plate electrodes, is also of our strong interest.…”

“…Since 1940, almost all EO produced industrially has been made using this method [4]. To date, silver catalysts supported on alpha-alumina (Ag/a-Al 2 O 3 ) with alkali and transition metal promoters [5][6][7][8][9][10][11][12][13][14][15], such as Cs, Cu, Re, and Au, or with addition of chlorine-containing moderators into gaseous reactants [16][17][18][19][20], such as dichloroethane (C 2 H 4 Cl 2 ) and vinyl chloride (C 2 H 3 Cl), provide high selectivity for EO. However, the conventional catalytic process normally requires high temperatures, i.e.…”

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

“…The most extensively and effectively used technique for the ethylene epoxidation is catalytic processes, with the aid of silver-based catalysts supported on low-surface-area alpha-alumina-Ag/(LSA) a-Al 2 O 3 -without or with alkali and transition metal promoters (e.g., Cs, Cu, and Au), since these catalysts provide a reasonably high selectivity for ethylene oxide [5][6][7][8][9][10][11][12][13][14][15][16][17]. However, a high-temperature operation is required to efficiently drive these conventional catalytic processes.…”

Pretreatment Effect on CO Oxidation over Highly Ordered Mesoporous Silver Catalyst

“…17,18 Silver catalysts are also well-known for the epoxidation of ethylene. 19 In this work, the catalytic properties of a mesoporous silver material were investigated for CO oxidation for the first time, and the pretreatment effects on the catalytic activity were addressed.…”