Oxygen adsorption on supported silver catalysts investigated by microgravimetric and transient techniques

Journal Article · Fri Oct 01 04:00:00 EDT 1993 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1993.1291· OSTI ID:5154243

Kondarides, D I; Verykios, X E ^[1]

---

1. Univ. of Patras (Greece)

Oxygen adsorption on [alpha]-Al[sub 2]O[sub 3]-supported Ag catalysts was investigated in the temperature range 40 to 400[degrees]C. The adsorption kinetics, studied with a vacuum ultramicrobalance and analyzed with the Elovich equation, indicate that three kinetically distinguishable processes take place, with activation energies of [approximately]1, 10.5, and 24 kcal/mol. Temperature-programmed desorption (TPD) experiments confirm the existence of three adsorbed oxygen species. A weakly adsorbed species, which is found to desorb below 150[degrees]C, is related to the 10.5 kcal/mol adsorption process and is assigned to molecularly adsorbed oxygen. The adsorption peak at 285[degrees]C is related to the almost nonactivated process and is ascribed to atomic oxygen, which is probably multicoordinated on the surface. At high adsorption temperatures (300 and 400[degrees]C) a third peak, desorbing above 400[degrees]C, is observed in the TPD profiles and is related to the highly activated process of 24 kcal/mol which is revealed by the gravimetric experiments. This species is suggested to be subsurface oxygen based on the results of TPD experiment conducted after isotope exchange of preadsorbed [sup 16]O[sub 2] and [sup 18]O[sub 2]. Temperature-programmed reaction (TPR) experiments showed that all three species are active toward ethylene combustion. 36 refs., 9 figs., 1 tab.

• OSTI ID: 5154243
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 143:2; 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
400800 -- Combustion
Pyrolysis
& High-Temperature Chemistry
ACTIVATION ENERGY
ADSORPTION
ALKENES
CATALYSIS
CATALYST SUPPORTS
CHEMICAL ANALYSIS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMBUSTION
ELEMENTS
ENERGY
ETHYLENE
GRAVIMETRIC ANALYSIS
HETEROGENEOUS CATALYSIS
HYDROCARBONS
ISOTOPIC EXCHANGE
KINETICS
METALS
NONMETALS
ORGANIC COMPOUNDS
OXIDATION
OXYGEN
QUANTITATIVE CHEMICAL ANALYSIS
REACTION KINETICS
SILVER
SORPTION
SORPTIVE PROPERTIES
SURFACE PROPERTIES
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENTS