Catalytic combustion of ethane over palladium foil in the 300-450 degrees C range: Kinetics and surface composition studies - Université Claude Bernard Lyon 1 Accéder directement au contenu
Article Dans Une Revue Journal of Catalysis Année : 1998

Catalytic combustion of ethane over palladium foil in the 300-450 degrees C range: Kinetics and surface composition studies

P. W. Jacobs
  • Fonction : Auteur
G. A. Somorjai
  • Fonction : Auteur

Résumé

Catalytic oxidation of ethane over palladium foils was studied and the kinetic parameters were determined for the reaction. The studies were carried out at 800 Torr total pressure over a wide range of reaction conditions in the temperature range of 300-425 degrees C. The catalyst surface composition was characterized before and after reaction by Auger electron spectroscopy (AES). While we detected only metallic palladium before reaction, the postreaction analysis showed significant formation of PdOx, a surface oxide, at all temperatures and under all ethane/oxygen ratios. The catalyst that exhibits optimum combustion activity is the one covered with 0.3 to 0.5 monolayer of oxygen. Carbon monoxide temperature-programmed desorption (CO-TPD) was used to evaluate the surface area of the metallic and oxidized palladium in order to normalize the measured catalytic reaction rates. The turnover rate for ethane combustion is in the range of 1-260 s(-1) (molecule(s) of CO2 produced per surface palladium atom per second) in the studied temperature range. Under stoichiometric reaction conditions at 325 degrees C the rate for ethylene combustion is 100 times faster than that of ethane and the turnover rate for ethylene formation is calculated to be 0.6 s(-1) (molecule(s) of C2H4 produced per surface palladium atom per second). At 325 degrees C the kinetic orders are 1, 0, and -1 for ethane, carbon dioxide, and water, respectively. The order in oxygen is -1/2 under stoichiometric and fuel-rich conditions and 0 under oxidizing conditions. Apparent activation energies of 104, 116, and 189 kJ/mol under fuel lean, stoichiometric, and fuel-rich conditions, respectively, were observed. While CO2 is the main carbonaceous product, unoxidized and partially oxidized species, methane and ethylene, are produced in small amounts. The product distribution is typically 98.6 mol% CO2, 0.9 mol% C2H4, and 0.5 mol% CH4 at 10% conversion during a reaction at 350 degrees C under stoichiometric conditions. (C) 1998 Academic Press.

Dates et versions

hal-01400708 , version 1 (22-11-2016)

Identifiants

Citer

C. Descorme, P. W. Jacobs, G. A. Somorjai. Catalytic combustion of ethane over palladium foil in the 300-450 degrees C range: Kinetics and surface composition studies. Journal of Catalysis, 1998, 178 (2), pp.668-678. ⟨10.1006/jcat.1998.2186⟩. ⟨hal-01400708⟩
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