In-situ transient studies on supported noble metal catalysts
Transient studies on the oxidation of CO have been performed over Pd/SiO[sub 2], Pt/SiO[sub 2], Rh/SiO[sub 2] and Pt/Al[sub 2]O[sub 3] catalysts using a rapid scan FTIR coupled to a quadrupole mass spectrometer. The data from the oxidation reaction on Pd/SiO[sub 2] and Pt/SiO[sub 2] can be explained in terms of a CO-O[sub 2] reaction model consisting of CO islands with highly reactive boundaries. The results for self-sustained CO-O[sub 2] explains the coupling of the autocatalytic and inhibition steps. Induction times required for the formation of gas phase CO[sub 2] were found to be nearly two orders of magnitude lower on Rh/SiO[sub 2] than those observed for Pt/SiO[sub 2] and Pd/SiO[sub 2]. The reactivity of linearly adsorbed CO on Rh/SiO[sub 2] was found to be considerably greater than that of the dicarbonyl species both at 85 and 200C. H[sub 2]-CO-O[sub 2] transient studies on Rh/SiO[sub 2] also suggest the formation of mixed hydrogen-CO adlayers. Hydrogen was observed to react with the dicarbonyl species to form a hydrido-carbonyl species. The CO which is displaced by hydrogen reacts rapidly with chemisorbed oxygen to form CO[sub 2]. A novel technique which enables the measurement of rate constants for adsorption and desorption over supported metal catalysts has been developed and tested. This technique has been successfully applied to the measurement of both adsorption and desorption rate constants for CO adsorbed on a 1% Pt/SiO[sub 2] catalyst. At low temperatures, it is possible to obtain the rate constants for only the reversibly adsorbed CO. A sticking coefficient corresponding to the adsorption of weakly bound CO on Pt under conditions of high CO surface coverage was obtained.
- Research Organization:
- Illinois Univ., Chicago, IL (United States)
- OSTI ID:
- 6927465
- Country of Publication:
- United States
- Language:
- English
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ADSORPTION
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISORPTION
DESORPTION
ELEMENTS
FOURIER TRANSFORMATION
HYDROGEN
HYDROGENATION
INFRARED SPECTRA
INTEGRAL TRANSFORMATIONS
KINETICS
MASS SPECTROSCOPY
MEASURING METHODS
METALS
NONMETALS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PALLADIUM
PLATINUM
PLATINUM METALS
REACTION KINETICS
RHODIUM
SEPARATION PROCESSES
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SPECTRA
SPECTROSCOPY
SURFACE PROPERTIES
SYNTHESIS
TIME DEPENDENCE
TRANSFORMATIONS
TRANSIENTS
TRANSITION ELEMENTS