Effect of Rhenium on Ag/ SrTiO3 Catalyst in Ethylene Epoxidation Reaction: Synthesize, Characterization and Evaluation

In this study, silver catalysts on SrTiO3 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 (3 catalyst. Rhenium leads to the weakening of the peaks intensity in the crystalline structure of the catalysts. In addition, the predominance of Ag (111) surface facets compared to the Ag (110) and Ag (100) surface facets are obvious in the XRD results. The ability of the catalysts in oxygen adsorption and desorption is studied through O2-TPD results. Ethylene conversion increases by adding rhenium to the Ag-Cs/SrTiO3 catalyst in the temperature range of 210 to 220 °C. Ethylene oxide selectivity increases slightly from 80% to 84% in the Ag-Cs-Re/SrTiO3 while this value in the Ag-Cs/SrTiO3 catalyst decreases from 65% to 34%, in the mentioned temperature range. Severe sensitivity of the rhenium-conation catalyst to the inlet concentration of carbon dioxide (6 mol %) is observed through a 50% drop in the produced ethylene oxide compared to the product which doesn’t have any carbon dioxide in the feed.