The oxidation state and catalytic activity of supported rhodium

Journal Article · Fri Apr 01 04:00:00 EST 1983 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(83)90274-9· OSTI ID:5614849

Oh, S E; Carpenter, J E

Rhodium is a common constituent of three-way catalysts used for the simultaneous conversion of nitrogen oxides, carbon monoxide, and hydrocarbons in automobile exhaust. The literature data indicate that supported rhodium can form surface oxides quite readily in an oxidizing gaseous environment. Moreover, the oxidation state of rhodium has been reported to influence the catalytic activity. Such characteristics of supported rhodium have important implications in three-way automotive emission control, because the exhaust composition surrounding three-way catalysts fluctuates between net-oxidizing and net-reducing conditions. This paper describes the results of laboratory experiments aimed at investigating how the intrinsic properties of an alumina-supported rhodium catalyst change in response to such oscillations in feedstream composition. The results of steady-state and transient experiments which illustrate how the catalytic activity of Rh is affected by changes in the stoichiometry of its gas-phase surroundings. The formal oxidation state of the Rh is then determined by X-ray photoelectron spectroscopy (XPS), following pretreatment either with single-component gases or with reactant mixtures. The surface of the pretreated sample was also characterized by CO titration of the oxygen bound to the catalyst as a result of Rh oxidation.

• Research Organization: General Motors Research Lab., Warren, MI
• OSTI ID: 5614849
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 80:2; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
330700 -- Advanced Propulsion Systems-- Emission Control
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
AIR POLLUTION
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYSIS
CATALYTIC CONVERTERS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
CONVERSION
ELECTRON SPECTROSCOPY
ELEMENTS
EQUIPMENT
HYDROCARBONS
METALS
NITROGEN COMPOUNDS
NITROGEN OXIDES
ORGANIC COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
PLATINUM METALS
POLLUTION
POLLUTION CONTROL EQUIPMENT
RHODIUM
SPECTROSCOPY
TRANSITION ELEMENTS
X-RAY SPECTROSCOPY