Ethylene Epoxidation Activity Over Ag-Based Catalysts on Different Nanocrystalline Perovskite Titanate Supports

Ag-based catalysts on different nanocrystalline perovskite supports (MgTiO3, CaTiO3, SrTiO3, and BaTiO3), and nanocrystalline TiO2 support prepared by a sol-gel method and on a commercial alpha-Al2O3 support were comparatively studied for catalytic activity of the ethylene epoxidation reaction. The dependence of ethylene oxide production performance on calcination temperature of the support, type of titanate nanocrystal supports, Ag loading, and reaction temperature was systematically investigated. The catalysts were analytically characterized by a Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), temperature programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). Among studied catalysts, the 17.2 wt% Ag/SrTiO3 catalyst exhibited the highest catalytic activity towards ethylene epoxidation reaction. The long-term stability of the dominant catalysts (which exhibited a high catalytic activity to produce ethylene oxide) was studied at 48 h of time on stream. As shown in the figure, the 17.2 wt% Ag/SrTiO3 catalyst with the support calcination temperature of 923 K is the most effective catalyst for the ethylene epoxidation reaction, giving not only the highest EO selectivity but also providing the highest long-term stability.