Influence of the A-site cation in ACoO[sub 3] (A = La, Pr, Nd, and Gd) perovskite-type oxides on catalytic activity for methane combustion

Journal Article · Mon Feb 28 23:00:00 EST 1994 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1016/0021-9517(94)90030-2· OSTI ID:6779044

Baiker, A ^[1]; Marti, P E ^[2]; Keusch, P ^[3]; Fritsch, E; Reller, A ^[4]

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1. Swiss Federal Institute of Technology, Zuerich (Switzerland)
2. Paul Scherrer Institut, Villigen (Switzerland)
3. Univ. of Zuerich (Switzerland)
4. Univ. of Hamburg (Germany)

The effect of rare-earth ions (La, Pr, Nd, and Gd) in ACoO[sub 3] perovskites on the thermal behavior and on the catalytic activity for methane oxidation has been studied. The thermal reduction, as investigated by oxygen desorption analysis, revealed for all perovskites one evolution step occurring above 1100 K. Transmission electron micrographs at the beginning of the desorption step revealed the presence of superstructures, which are attributed to the formation of oxygen-deficient domains (ACoO[sub 2.5] [le] ACoO[sub 3-x] [le] ACoO[sub 3]) adopting perovskite-related brownmillerite-type structures. A model for the sequence of the structural changes of the perovskites during the reduction is proposed. The amount of oxygen which evolved above 1100 K increased with decreasing size of the lanthanide ion. Comparative catalytic studies were carried out in a fixed-bed microreactor at atmospheric pressure in the temperature range 600-1200 K. The activities at 830 K, expressed as reaction rates referred to the BET surface area, increased in the order PrCoO[sub 3] [much lt] LaCoO[sub 3] < NdCoO[sub 3] < GdCoO[sub 3]. However, no significant influence of the A-site cations on the catalytic activity of ACoO[sub 3] perovskites can be markedly affected by the presence of Co[sub 3]O[sub 4] impurity in the perovskites. 30 refs., 10 figs., 3 tabs.

• OSTI ID: 6779044
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 146:1; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
034000* -- Natural Gas-- Combustion
ALKANES
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
COBALT COMPOUNDS
COBALT OXIDES
COMBUSTION
DESORPTION
ELECTRON MICROSCOPY
GADOLINIUM COMPOUNDS
GADOLINIUM OXIDES
HYDROCARBONS
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
METHANE
MICROSCOPY
NEODYMIUM COMPOUNDS
NEODYMIUM OXIDES
ORGANIC COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PRASEODYMIUM COMPOUNDS
PRASEODYMIUM OXIDES
RARE EARTH COMPOUNDS
SORPTION
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
TEMPERATURE RANGE 1000-4000 K
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY