The chemistry of acetates on the Rh(111) surface

Journal Article · Sat Jan 01 00:00:00 EST 1994 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1994.1005· OSTI ID:7185288

Houtman, C J; Brown, N F; Barteau, M A ^[1]

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1. Univ. of Delaware, Newark (United States)

The formation of acetates by the dissociation of acetic acid on the clean Rh(111) surface and by reactions of acetic acid, acetaldehyde, and ethanol with preadsorbed oxygen atoms was examined using HREELS and TPD. Acetate intermediates were identified by the characteristic vibrations of the O-C-O moiety symmetrically bonded to the surface via both oxygen atoms. Acetates formed from acetic acid on the clean Rh(111) surface decomposed via two pathways. C-O scission by 278 K released adsorbed carbon monoxide and atomic oxygen; decarboxylation at 372 K liberated carbon dioxide and hydrogen. Acetates were formed after the adsorption of both ethanol and acetaldehyde on the Rh(111)-(2 x 2)O surface, as well as after the adsorption of acetic acid. For the alcohol and the aldehyde, the adsorbed intermediate involved in the reaction with atomic oxygen was likely [eta][sup 2](C,O)-acetaldehyde. For acetic acid on the Rh(111)(2 x 2)O surface, acetates were formed via direct transfer of the acid hydrogens to the surface oxygen atoms to form surface hydroxyls. When oxygen atoms were present on the surface, the only pathway for acetate decomposition was decarboxylation at 430 K. Thus coadsorbed oxygen atoms provide significant stabilization of acetates on Rh(111), as previously observed for formates on the same surface. In the presence of adsorbed oxygen, a portion of the methyl groups of surface acetates was oxidized to CO at temperatures below those expected for reactions of atomic carbon and oxygen species. This observation suggests that oxygen intervenes in the acetate decomposition pathway prior to the complete fragmentation of these intermediates. 63 refs., 11 figs., 10 tabs.

• DOE Contract Number: FG02-84ER13290
• OSTI ID: 7185288
• Journal Information: Journal of Catalysis; (United States), Vol. 145:1; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
10 SYNTHETIC FUELS
ACETATES
CHEMICAL REACTIONS
RHODIUM
CATALYTIC EFFECTS
DESORPTION
ELECTRON SPECTROSCOPY
MILLER INDICES
REACTION INTERMEDIATES
CARBOXYLIC ACID SALTS
ELEMENTS
METALS
PLATINUM METALS
SORPTION
SPECTROSCOPY
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties
100200 - Synthetic Fuels- Production- (1990-)