1Departent of Cehmistry, Faculty of Science, Ferdowsi University of Meshhad, P.O. Box 91735-654, Meshhad, I.R. IRAN
2National Iranian Oil Research Center (NIORC), Ray, I.R. IRAN
Oxidation of ethylene to ethylene oxide over silver catalyst and selenium modified catalyst has been studied by continuous flow and pulse techniques over the temperature range of 230-280 °C. The results are discussed in terms of reaction mechanisms proposed by others, rejecting mechanisms which involve peroxide formation. It has been shown that not only selectivity towards ethylene oxide production increases considerably by introduction of 0.01 atom percent of selenium into silver, but the reactivity increases also. Above 270 °C selectivity drops almost to the level of unmodified catalyst because selenium atoms diffuse into the grooves between silver crystals on the surface of catalyst. It has also been shown that intermolecular conversion of ethylene oxide to acetaldehyde decreases.