XPS and reaction investigation of alkali promotion of Rh/La[sub 2]O[sub 3]

Journal Article · Wed Mar 31 23:00:00 EST 1993 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1993.1098· OSTI ID:6131448

Gallaher, G R; Goodwin, Jr, J G; Huang, Chenshi; Houalla, M ^[1]

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1. Univ. of Pittsburgh, PA (United States)

In order to investigate the combined effect of a promoter and a detached support species on a supported metal catalyst, alkali promotion of Rh on the decorative support La[sub 2]O[sub 3] was investigated by X-ray photoelectron spectroscopy, X-ray diffraction, H[sub 2] and CO chemisorption, ethane hydrogenolysis, and cyclopropane hydrogenation. Previously, decorating lanthana moieties have been found to partially suppress ethane hydrogenolysis and cyclopropane hydrogenation on Rh/La[sub 2]O[sub 3]. The major effects of alkali promotion of Rh/La[sub 2]O[sub 3] on these reactions were a decline in apparent activation energy for ethane hydrogenolysis and a moderate additional suppression of cyclopropane hydrogenation activity. Alkali promotion of the more active Rh/SiO[sub 2] reference catalyst, which is not decorated by support entities, resulted in a much more significant suppression of these reactions. For Rh/La[sub 2]O[sub 3], alkali promotion appeared to block sites and/or pathways for hydrogen spillover. In addition, Rb inhibited the Rh-catalyzed decomposition of carbonate species on the lanthana support. No additional effect of alkali promotion was indicated on the [minus]1-eV shift of Rh 3d[sub 5/2] binding energy observed on Rh/La[sub 2]O[sub 3] relative to Rh/SiO[sub 2]. This is consistent with the lack of a Rh 3d[sub 5/2] binding energy shift observed for Rb-promotion of Rh/SiO[sub 2]. The Rb 3p[sub 3/2] binding energy was shifted to the same extent as Rh in Rb/Rh/La[sub 2]O[sub 3], suggesting that the chemical environment for Rb differs between SiO[sub 2]-supported and La[sub 2]O[sub 3]-supported systems or, more likely, that the binding energy shifts observed for this system are just due to differences in the binding energies for the reference carbon on SiO[sub 2] vs on La[sub 2]O[sub 3]. 44 refs., 4 figs., 7 tabs.

• OSTI ID: 6131448
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 140:2; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ACTIVATION ENERGY
ALKALI METAL COMPLEXES
ALKALI METAL COMPOUNDS
ALKANES
BINDING ENERGY
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISORPTION
COHERENT SCATTERING
COMPLEXES
DECOMPOSITION
DIFFRACTION
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY
ETHANE
HYDROCARBONS
HYDROGEN
HYDROGENATION
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
POTASSIUM COMPOUNDS
PROMOTERS
PROPANE
RARE EARTH COMPOUNDS
REFRACTORY METAL COMPOUNDS
RHODIUM COMPOUNDS
RUBIDIUM COMPLEXES
SCATTERING
SEPARATION PROCESSES
SORPTION
SORPTIVE PROPERTIES
SPECTROSCOPY
SURFACE PROPERTIES
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY