Comparative study on the influence of second metals on Ag-loaded mesoporous SrTiO3 catalysts for ethylene oxide evolution

Ag/mesoporous-assembled SrTiO3 catalysts with different loaded second metals (Au, Ba, Pd, Sn, and Cu) were tested for catalytic activity toward ethylene oxide formation from the epoxidation reaction of ethylene, in comparison to Ag- and Au-loaded on the SrTiO3 supports. To promote long-term stability, Sn was added to the optimum bimetallic catalyst. The catalysts were analytically characterized by 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) analyses. The addition of a second metal of Au, Ba, or Cu significantly improved the catalytic performance for ethylene epoxidation, whereas the Pd and Sn did not. The Cu–Ag bimetallic catalyst exhibited the highest catalytic ethylene oxide production activity. An addition of Sn to this catalyst greatly promoted the long-term stability toward the ethylene epoxidation.

Graphical abstractEO selectivity as a function of time on stream for 17.16 wt.% Ag/SrTiO3 catalyst compared with 1.41 wt.% Cu–17.16 wt.% Ag/SrTiO3 catalyst and 0.32 wt.% Sn–1.39 wt.% Cu–17.16 wt.% Ag/SrTiO3 catalyst (6% O2 and 6% C2H4 balanced with He, a space velocity of 6000 h−1, a pressure of 24.7 psia, a reaction temperature of 548 K).Figure optionsDownload full-size imageDownload high-quality image (129 K)Download as PowerPoint slideHighlights► The catalytic activity was improved by adding appropriate second metals on Ag/SrTiO3 catalyst. ► The bimetallic Cu–Ag catalyst significantly improved catalytic performance of Ag/SrTiO3. ► The 0.32 wt.% Sn loaded on 1.39 wt.% Cu–17.16 wt.% Ag/SrTiO3 was the most effective catalyst. ► Addition of Sn promoter with a proper amount on bimetallic Cu–Ag catalyst reduced coke formation.