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Title: In-situ transient studies on supported noble metal catalysts

Abstract

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 supportedmore » 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.« less

Authors:
Publication Date:
Research Org.:
Illinois Univ., Chicago, IL (United States)
OSTI Identifier:
6927465
Resource Type:
Miscellaneous
Resource Relation:
Other Information: Thesis (Ph.D.)
Country of Publication:
United States
Language:
English
Subject:
33 ADVANCED PROPULSION SYSTEMS; 54 ENVIRONMENTAL SCIENCES; 01 COAL, LIGNITE, AND PEAT; CARBON MONOXIDE; OXIDATION; PALLADIUM; CATALYTIC EFFECTS; PLATINUM; RHODIUM; ADSORPTION; ALUMINIUM OXIDES; CARBON DIOXIDE; CATALYST SUPPORTS; CHEMICAL REACTION KINETICS; CHEMISORPTION; DESORPTION; FOURIER TRANSFORMATION; HYDROGEN; HYDROGENATION; INFRARED SPECTRA; MASS SPECTROSCOPY; MEASURING METHODS; SILICON OXIDES; SURFACE PROPERTIES; SYNTHESIS; TIME DEPENDENCE; TRANSIENTS; ALUMINIUM COMPOUNDS; CARBON COMPOUNDS; CARBON OXIDES; CHALCOGENIDES; CHEMICAL REACTIONS; ELEMENTS; INTEGRAL TRANSFORMATIONS; KINETICS; METALS; NONMETALS; OXIDES; OXYGEN COMPOUNDS; PLATINUM METALS; REACTION KINETICS; SEPARATION PROCESSES; SILICON COMPOUNDS; SORPTION; SPECTRA; SPECTROSCOPY; TRANSFORMATIONS; TRANSITION ELEMENTS; 330702* - Emission Control- Carbon Monoxide; 540120 - Environment, Atmospheric- Chemicals Monitoring & Transport- (1990-); 010800 - Coal, Lignite, & Peat- Waste Management

Citation Formats

Li, Yaoen. In-situ transient studies on supported noble metal catalysts. United States: N. p., 1988. Web.
Li, Yaoen. In-situ transient studies on supported noble metal catalysts. United States.
Li, Yaoen. Fri . "In-situ transient studies on supported noble metal catalysts". United States.
@article{osti_6927465,
title = {In-situ transient studies on supported noble metal catalysts},
author = {Li, Yaoen},
abstractNote = {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.},
doi = {},
url = {https://www.osti.gov/biblio/6927465}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1988},
month = {1}
}

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