Partial oxidation of propene is promoted by Au following deposition of atomic oxygen (0.3 ML) via O 3 decomposition on Au(111) at 200 K. Several partial oxidation products-acrolein, acrylic acid, and carbon suboxide (O=C=C=C=O)-are produced in competition with combustion to CO 2 and H 2O. Acrolein is the primary partial oxidation product, and it is further oxidized to the other products by excess oxygen. We propose that acrolein is derived from allyloxy intermediate that is formed via insertion of oxygen into the allylic C-H bond. While no propene epoxide formation is detected from oxidation of C 3H 6, a small amount of epoxidation is observed during reaction of C 3D 6 and CD 3CH=CH 2. These results are strong indications that small changes in the energy required for allylic C-H activation, in this case due to a kinetic isotope effect, may dramatically change the selectivity; thus, small modifications of the properties of oxygen on Au may lead to the more desirable epoxidation process. Our results are discussed in the context of the origin of activity of Au-based catalysts.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry