Reversibility of hydrogen chemisorption on a ceria-supported rhodium catalyst

Journal Article · Tue Sep 01 00:00:00 EDT 1992 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1016/0021-9517(92)90134-4· OSTI ID:7141592

Bernal, S; Calvino, J J; Cifredo, G A; Izquierdo, J.M. Rodriguez ^[1]; Perrichon, V; Laachir, A ^[2]

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1. Univ. de Cadiz, Perto Real (Spain)
2. Inst. de Recherches sur la Catalyse (France)

Cerium dioxide is an important component of the so-called three-way catalysts. This work reports on some new aspects of the chemistry of hydrogen-ceria systems. It is shown that, at room temperature, in the presence of highly dispersed rhodium, ceria chemisorbs large amounts of hydrogen. As deduced from magnetic measurements carried out in situ, this spillover process leads to the reduction of ceria to an extent of 21% of the total amount of cerium ions present in the sample, which is roughly equivalent to the complete surface reduction of the oxide. It is found that over a highly hydroxylated sample the reduction of ceria induced by the spillover process is partly reversible even at 295 K. If the sample is pumped off at 773 K, the initial oxidation state of ceria is almost completely recovered. Both the rate and extent of hydrogen chemisorption on ceria were found to be sensitive to the specific pretreatment applied to the catalyst. Over bare ceria, hydrogen chemisorption at 298 K was negligible, temperatures as high as 473 K being necessary to activate the process. In contrast to the rhodium-containing catalyst, over pure ceria the desorption of hydrogen leads to a much larger extent to water formation, thus revealing a deeper irreversible reduction of the oxide.

• OSTI ID: 7141592
• Journal Information: Journal of Catalysis; (United States), Vol. 137:1; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
33 ADVANCED PROPULSION SYSTEMS
CERIUM OXIDES
SORPTIVE PROPERTIES
HYDROGEN
CHEMISORPTION
RHODIUM
CATALYTIC EFFECTS
AMBIENT TEMPERATURE
CATALYSIS
CATALYSTS
CATALYTIC CONVERTERS
REDUCTION
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
VALENCE
CERIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
EQUIPMENT
METALS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
POLLUTION CONTROL EQUIPMENT
RARE EARTH COMPOUNDS
SEPARATION PROCESSES
SORPTION
SURFACE PROPERTIES
TEMPERATURE RANGE
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties
330700 - Advanced Propulsion Systems- Emission Control