Oxidative cleavage of propene on Ir(111): double-bond scission during the formation of acetate

• Published in: Surface science Vol. 398; no. 1-2; pp. 11 - 27
• Main Authors: Karseboom, S.G., Davis, J.E., Mullins, C.B.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 10-02-1998; Amsterdam Elsevier Science; New York, NY
• Subjects: Alkenes; Catalysis; Chemisorption; Chemistry; Electron energy loss spectroscopy; Exact sciences and technology; General and physical chemistry; Iridium; Low index single crystal surfaces; Oxidation; Solid-gas interface; Surface physical chemistry; Thermal desorption spectroscopy; Chemisorption; Alkenes; Low index single crystal surfaces; Thermal desorption spectroscopy; Oxidation; Catalysis; Iridium; Electron energy loss spectroscopy; Gas solid adsorption; Oxygen; Propene; Coadsorption; Gas solid interface; Thermodesorption; Experimental study
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/S0039-6028(98)80007-1

High-resolution electron energy-loss spectroscopy (HREELS) and temperature-programmed reactive desorption (TPRD) techniques have been used to examine the interaction of coadsorbed propene (propylene) and oxygen on the Ir(111) surface. At less than 80 K, propene adsorbs onto oxygen-precovered Ir(111) in a π-bound state. Acetate and η2(C,O)-acetone as well as gaseous acetone, water and dihydrogen are produced by 295 K during the oxidation of this species. Isotopic labeling experiments suggest that acetate and η2(C,O)-acetone are produced in parallel to or in competition with one another rather than from each other, and that π-allyl (CH2CHCH2) is not a precursor to either species. In contrast, exposing the bare Ir(111) surface to propylene at less than 80 K results in adsorbed propylene, which is more strongly rehybridized than that on the oxygen-precovered Ir(111) surface. This propylene, nominally referred to as di-σ-bound propylene, could also be oxidized to acetate and η2(C,O)-acetone. Possible mechanisms for the oxidation of π-bound propene are developed, and comparisons/contrasts are made between the interaction of propene and oxygen on Ir(111) and the interaction of 2-methylpropene (isobutylene) and oxygen on this surface.