(569ao) Computational Identification of New Ethylene Oxide Reaction Pathways

Ethylene oxide (EO) is a vital compound used as an intermediate in the creation of other important compounds, such an ethylene glycol and glycol ether. In industry, EO is produced by selective ethylene oxidation (epoxidation) with supported Ag catalysts. Achieving high selectivity towards EO rather than CO₂ is the primary goal of research in this area, and understanding the factors that influence selectivity is critical for improving performance. The most widely accepted intermediate in EO is the oxametallacycle (OMC), which contains an O-Ag-C-C ring. However, possible reactions between surface O and the OMC have not been comprehensively studied. In this work, density functional theory (DFT) was used to systematically study the possible reaction pathways from the OMC in the presence of surface O. We find that surface O opens up two kinetically and thermodynamically favorable pathways, neither which form EO. Specifically, the formation of ethylenedioxy and O-assisted C-H bond scission are quite facile and predicted to be more favorable than the traditional EO (ring-closure) and acetaldehyde (H transfer) pathways. Furthermore, we found surface O has a similar effect on propylene oxide production from propylene oxidation. These results show the potential importance of surface O in influencing selectivity, as surface O promotes these non-selective reactions. Thus, these reaction pathways should be considered in both design and kinetic models of EO catalysts.