Ethylene epoxidation over shape-selective silver-based catalysts

The catalytic activity and selectivity of silver catalysts in the ethylene epoxidation reaction are intrinsically linked to their faceting. Here, silver nanowires, representing Ag(100), and silver spherical catalysts, embodying Ag(111), were synthesized using modified polyol and wet impregnation methods, respectively. Recognizing the size-dependent nature of catalysis, two distinct sizes of spherical particles were synthesized to serve as comparative benchmarks for silver nanowire activity and selectivity. Silver spherical catalysts were promoted with optimal cesium loading. Furthermore, silver nanowires underwent cesium promotion at varying loadings, as meticulously detailed in the methodology. Unpromoted silver nanowires exhibited superior ethylene oxide selectivity compared to both unpromoted and promoted spherical catalysts. Additionally, the ethylene oxide selectivity was enhanced with the addition of the promoter, achieving activity and selectivity levels comparable to the best reported in the literature. Morphological analysis of spent silver nanowire catalysts revealed exceptional stability even after extended study periods.