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 alpha-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 alpha-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. (C) 2012 Elsevier B.V. All rights reserved.