THERMAL-DECOMPOSITION OF ETHYLENE-OXIDE ON PD(111) - COMPARISON OF THE PATHWAYS FOR THE SELECTIVE OXIDATION OF ETHYLENE AND OLEFIN METHATHESIS

The product distribution detected in the multimass temperature-program med desorption of a saturated overlayer of ethylene oxide adsorbed on Pd(111) at approximately 180 K indicates that it decomposes to yield e thylene and acetaldehyde. These observations are interpreted by postul ating that ethylene oxide reacts to form an oxymetallocycle. This is p roposed to thermally decompose in a manner analogous to carbometallocy cles that form during olefin metathesis catalysis by the reaction betw een an alkene and a surface carbene. Thus, the metallocycle can decomp ose to yield ethylene and deposit adsorbed atomic oxygen or undergo a beta-hydrogen transfer to form acetaldehyde.