Enhancement of CO hydrogenation of rhodium by TiO/sub x/ overlayers
The kinetics of CO hydrogenation at atmospheric pressure over a polycrystalline Rh foil with titania deposits were characterized with respect to the surface composition. The titania overlayers (TiO/sub x/, x approx. 1.9) were prepared by titanium evaporation under ultrahigh vacuum with subsequent oxidation. Coverages were determined by Auger electron spectroscopy (AES). A sharp maximum in methanation activity, relative to the clean Rh surface, was observed with coverage. A threefold enhancement in activity was found for a TiO/sub x/ coverage of 0.15 of a monolayer. The increase in rate at low coverages was accompanied by a higher selectivity toward olefins (10% ..-->.. 31%), a lower activation energy (24.4 ..-->.. 16.8 kcalmol), a higher H/sub 2/ reaction order (1.0 ..-->.. 2.6), and a higher CO reaction order (-1.0 ..-->.. -0.3). The kinetic parameters for olefin production were noticeably different than those for paraffin production as well. The dependence of the activity on TiO/sub x/ coverage has been modeled through a Monte Carlo simulation assuming the existence of sites of high activity at the oxide-metal interface. This model is consistent with the premise of Ti/sup 3 +/ participation in the dissociation of CO. 33 references
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5330284
- Journal Information:
- J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 106:2; ISSN JCTLA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
010408* -- Coal
Lignite
& Peat-- C1 Processes-- (1987-)
ACTIVATION ENERGY
ALKANES
ALKENES
AUGER ELECTRON SPECTROSCOPY
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY
EQUATIONS
HYDROCARBONS
HYDROGENATION
KINETIC EQUATIONS
KINETICS
LAYERS
MATHEMATICAL MODELS
METALS
METHANATION
MONTE CARLO METHOD
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
REACTION KINETICS
RHODIUM
SPECTROSCOPY
SYNTHESIS
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS