Ethylene oxide (EO) is a key starting material for the production of a wide range of organic intermediates and final products, and is produced by the direct vapor phase oxidation of ethylene in the presence of promoted silver catalysts. Although the overall kinetics of the oxidation of ethylene to EO is well-known, the molecular details of this process, especially with regard to the influence of the promoters, are not well understood. In this study, the influence of promoters (Cl, Cs and Re) on ethylene oxidation will be presented. High Sensitivity-Low Energy Ion Scattering (HS-LEIS) of the fresh calcined catalysts revealed that the Al2O3-Ag particles were extensively covered by the promoters. This reveals that ethylene oxidation studies with unpromoted or “naked” Ag catalysts are not meaningful since they are not representative of actual industrial Ag catalysts that are highly selective for ethylene oxide (&gt;90%). Raman spectroscopy showed that the Cs promoter forms CsCO3 and the rhenium oxide promoter forms CsReO4 on the Ag particles. The influence of different reaction environments on the promoters and Ag-O was also examined with in situ Raman spectroscopy and will be presented. The reaction mechanism was determined from steady-state isotopic transient kinetic analysis (SSITKA) measurements with oxygen isotopes (16O2 à 18O2). The SSITKA studies also demonstrated that the ethylene oxidation reaction proceeds via a Langmuir-Hinshelwood mechanism involving gas phase molecular O2.

Ethylene oxidation by promoted supported Ag/Al2O3 catalysts: A fundamental perspective of an industrial catalyst

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.