The reaction mechanism of ethylene epoxidation on silver

Book chapter, 2025

Ethylene epoxidation remains one of the most industrially significant catalytic processes, as it serves as the primary route to ethylene oxide—an essential precursor chemical in the production of ethylene glycol, surfactants, and other chemicals. Despite nearly a century of commercial operation, the detailed reaction mechanism of silver-based catalysts remains the focus of intensive research. This chapter offers a detailed overview of the mechanistic pathways involved in ethylene epoxidation, particularly the competition between selective epoxide formation and total oxidation routes. In particular, it explores the role of different silver surface facets, the dynamic behavior of chemisorbed oxygen species, and the influence of surface modifiers such as chlorine and alkali metals. Special attention is given to the nature of electrophilic and nucleophilic oxygen species and their role in determining selectivity. Results from advanced experimental techniques, including in situ and operando spectroscopy, alongside density functional theory (DFT) and microkinetic modeling, are discussed and provide a multi-scale perspective on the catalyst behavior. Finally, we outline ongoing challenges and future directions, including integrating machine learning and data-driven approaches to unravel complex reaction networks.