| Autor: |
Olivier Dulaurent, Daniel Bianchi, Abdennour Bourane, Karine Chandes |
| Rok vydání: |
2001 |
| Předmět: |
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| Zdroj: |
Applied Catalysis A: General. 214:193-202 |
| ISSN: |
0926-860X |
| DOI: |
10.1016/s0926-860x(01)00483-5 |
| Popis: |
The present study compares the evolution of the IR band of the linear CO species (denoted by L) adsorbed on a 2.9% Pt/Al 2 O 3 catalyst with the increase in the temperature either in a helium flow (temperature programmed desorption-infrared experiments denoted by TPDIR) or in a x % CO/He flow (adsorption equilibrium-infrared experiments, denoted by AEIR). The AEIR method allows us to follow the change in the coverage, θ L of the L species with the adsorption temperature T a and then to determine its heats of adsorption at several coverages using an adsorption model. The TPDIR method allows us to determine the change in θ L with the desorption temperature T d . The comparison between the experimental and theoretical curves θ L = f ( T d ) reveals that the readsorption of CO cannot be prevented during the TPDIR experiments even at high helium flow rates. The curves θ L = f ( T d ) are in agreement with a pseudo adsorption equilibrium which may provide the heat of adsorption of the L species if some experimental parameters are known (flow rate, weight of catalyst, amount of adsorbed species at 300 K, rate of increasing temperatures). However, it is shown that the TPDIR method is very sensitive to parallel reactions such as the reaction between the L species and H 2 O produced by the OH groups of the support. It is shown that AEIR experiments are not influenced by those parallel reactions and constitutes a simple method to determine the heats of adsorption of adsorbed species at several coverages. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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