Divergent pathways of acetaldehyde and ethanol decarbonylation on the Rh(111) surface
- Univ. of Delaware, Newark (United States)
The decomposition reactions of acetaldehyde and ethanol on the Rh(111) surface were compared in temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) experiments. The decarbonylation of acetaldehyde produced methane at 267 K in TPD. For acetaldehyde coverages less than 0.05 monolayer, no methane was desorbed, but for a coverage that saturated the first layer, methane was produced with 50% selectivity. Coadsorbing deuterium with a low coverage of acetaldehyde resulted in the enhancement of methane production. This result indicates that the selectivity to methane was partially controlled by the availability of hydrogen atoms on the surface required to hydrogenate the hydrocarbon species produced by acetaldehyde decarbonylation. Monodeuterated methane was the primary methane product observed after these coadsorption experiments. Thus it was concluded that acetaldehyde decarbonylates via a methyl migration mechanism on the Rh(111) surface. Decarbonylation of ethanol did not produce methane. The absence of methane production indicated that the decomposition of ethanol on the Rh(111) surface did not proceed via dehydrogenation to adsorbed acetaldehyde, but instead, ethanol appeared to dehydrogenate by methyl hydrogen abstraction resulting in the formation of an oxametallacycle. Since this proposed intermediate rapidly dehydrogenated to carbon monoxide and surface carbon, it was difficult to characterize spectroscopically. The existence of an ethanol decomposition pathway that does not include acetaldehyde intermediates indicates that ethanol formation on supported Rh catalysts may not be the result of acetaldehyde hydrogenation.
- DOE Contract Number:
- FG02-84ER13290
- OSTI ID:
- 5564775
- Journal Information:
- Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 130:2; ISSN 0021-9517; ISSN JCTLA
- Country of Publication:
- United States
- Language:
- English
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100200* -- Synthetic Fuels-- Production-- (1990-)
ACETALDEHYDE
ADSORPTION
ALCOHOLS
ALDEHYDES
ALKANES
CARBON
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CARBONYLATION
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CONTROL
DECOMPOSITION
DEHYDROGENATION
DEPOSITION
DESORPTION
DEUTERIUM
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY-LOSS SPECTROSCOPY
ETHANOL
HYDROCARBONS
HYDROGEN ISOTOPES
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
METALS
METHANE
NONMETALS
NUCLEI
ODD-ODD NUCLEI
OPTIMIZATION
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
QUANTITY RATIO
REACTION INTERMEDIATES
REACTION KINETICS
RHODIUM
SORPTION
SPECTROSCOPY
STABLE ISOTOPES
SURFACE PROPERTIES
SYNTHESIS
TEMPERATURE CONTROL
TRACER TECHNIQUES
TRANSITION ELEMENTS