Effect of Rhenium on Ag/ SrTiO۳ Catalyst in Ethylene Epoxidation Reaction: Synthesize, Characterization and Evaluation

In this study, silver catalysts on SrTiO۳ support contain cesium, and rhenium promoters are synthesized using the impregnation method for ethylene epoxidation reaction. SEM results show a small decrease in metal dispersion by adding cesium (۳ catalyst. Rhenium leads to the weakening of the peaks intensity in the crystalline structure of the catalysts. In addition, the predominance of Ag (۱۱۱) surface facets compared to the Ag (۱۱۰) and Ag (۱۰۰) surface facets are obvious in the XRD results. The ability of the catalysts in oxygen adsorption and desorption is studied through O۲-TPD results. Ethylene conversion increases by adding rhenium to the Ag-Cs/SrTiO۳ catalyst in the temperature range of ۲۱۰ to ۲۲۰ °C. Ethylene oxide selectivity increases slightly from ۸۰% to ۸۴% in the Ag-Cs-Re/SrTiO۳ while this value in the Ag-Cs/SrTiO۳ catalyst decreases from ۶۵% to ۳۴%, in the mentioned temperature range. Severe sensitivity of the rhenium-conation catalyst to the inlet concentration of carbon dioxide (۶ mol %) is observed through a ۵۰% drop in the produced ethylene oxide compared to the product which doesn’t have any carbon dioxide in the feed.

Keywords:

Ethylene Epoxidation , Ethylene Oxide , Rhenium , Silver , Strontium Titanate