Infrared studies of ethene hydrogenation over ZrO2. Part 3.—Reaction mechanism

Abstract

The mechanism of ethene hydrogenation over ZrO₂ between 200 and 370 K has been examined by means of in situ infrared (IR) spectroscopy. Dissociatively adsorbed hydrogen forming ZrH and OH species on the ZrO₂ did not react with gaseous ethene but was just replaced by it. However, preadsorbed π-bonded ethene was found to be hydrogenated by gaseous H₂ to ‘side-on’ adsorbed ethane followed by a transformation into the more stable ‘end-on’ adsorbed ethane. Intermediate species such as ethyl groups were not observed. It was concluded that H₂ was activated on (or in the vicinity of) the site on which ethene was already preadsorbed as a π-bonded species.