Thermodynamic Considerations on the Oxidation State of Co/γ-Al2 O3 and Ni/γ-Al2 O3 Catalysts under Dry and Steam Reforming Conditions
- Resource Type
- Authors
- Andreas Giehr; Lubow Maier; Olaf Deutschmann; Stephan Andreas Schunk
- Source
- ChemCatChem. 10:751-757
- Subject
- inorganic chemicals
Methane reformer
Carbon dioxide reforming
010405 organic chemistry
Organic Chemistry
Inorganic chemistry
chemistry.chemical_element
010402 general chemistry
01 natural sciences
Catalysis
Methane
0104 chemical sciences
Inorganic Chemistry
Steam reforming
Nickel
chemistry.chemical_compound
chemistry
Oxidation state
Physical and Theoretical Chemistry
Cobalt
- Language
- ISSN
- 1867-3880
The oxidation state of the active metal is an important factor for catalyst stability under dry and steam reforming conditions. This works explores the correlation of the oxidation state of the active metal with the coking behavior of alumina supported cobalt and nickel catalysts from a thermodynamic point of view. To this end, the thermodynamics of the oxidation of Co/γ-Al2O3 and Ni/γ-Al2O3 are investigated using calculations at both standard and technical reforming conditions. It is shown that oxidation of nickel by water or CO2 cannot occur spontaneously under reforming conditions regardless of participation of the alumina support material due to positive Gibbs reaction energies. Cobalt, in contrast, is more easily oxidized and may form CoAl2O4 through interaction with the support. This phase may react with surface carbon to regenerate the catalyst after carbon formation due to thermal cracking of methane. A Mars-van-Krevelen type reaction scheme is proposed to explain the higher coking resistance of cobalt compared to nickel.