Effects of oxide supports on ethylene epoxidation activity over Ag-based catalysts

In this study, Ag-based catalysts with different loadings on various oxide supports, including low-surface-area α-Al2O3, Al2O3 C, Al2O3,Acid, SiO2 90, TiO2 and SrTiO3 synthesized by a sol–gel process, were investigated for ethylene epoxidation over a range of reaction temperatures. The specific surface area, crystallinity, surface morphology, oxidation state, metal crystallite size, and oxygen and ethylene adsorption characteristics of all prepared catalysts were characterized and correlated to the ethylene epoxidation activity. Compared with conventional Ag catalysts supported on low-surface-area α-Al2O3, the 17.16 wt% Ag/SrTiO3 catalyst exhibited much better catalytic activity for the ethylene epoxidation reaction, providing both the highest EO yield of 4.5% and EO selectivity up to 99%. The results indicate that high oxygen and ethylene uptakes, together with the large size of Ag particles, play an important role in achieving the best catalytic activity of the Ag/SrTiO3 catalyst towards ethylene epoxidation reaction.

EO selectivity as a function of Ag loading on SrTiO3 and TiO2 supports (6% O2 and 6% C2H4 balanced with He, a space velocity of 6000 h−1, a pressure of 24.7 psia, a temperature of 548 K).Figure optionsDownload high-quality image (61 K)Download as PowerPoint slideHighlights
► The effects of various oxide supports for Ag catalysts on EO selectivity and yield were studied.
► Ag/SrTiO3 was an effective catalyst for ethylene epoxidation (high EO selectivity and yield).
► The 17.16 wt% Ag/SrTiO3 gave the highest EO yield of 4.5% with the selectivity 99%.
► It produced no CO2 at the reaction temperature below 548 K.
► The superior performance may be related to its higher oxygen and ethylene adsorption ability.