Heat of adsorption of carbon monoxide on a Pd/Al{sub 2}O{sub 3} solid using in situ infrared spectroscopy at high temperatures

Journal Article · Fri Dec 10 04:00:00 EST 1999 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1999.2661· OSTI ID:20005898

Dulaurent, O; Chandes, K; Bouly, C; Bianchi, D

The adsorption of CO (1% CO/He mixture, 1 atm total pressure) on a reduced 1.4% Pd/Al{sub 2}O{sub 3} solid is studied in the temperature range 300--800 K by in situ Fourier transform infrared (FTIR) spectroscopy using a suitably constructed small-internal-volume infrared cell. Two main IR bands are detected above and below 2,000 cm{sup {minus}1}, ascribed to linear and bridged adsorbed CO species on palladium atoms, respectively. The change in IR band intensities with adsorption temperature is used to determine the evolution in the coverage {theta} of the various adsorbed species with this parameter. The observed curves are in good accord with an adsorption model assuming a linear decrease in the heats of adsorption in step with the increase in coverage. This allows determination of the heats of adsorption of each species at various coverages. For instance, at {theta} {approx} 0, the heats of adsorption are 92 and 168 kJ/mol for the linear and bridged CO species, respectively. As previously observed on platinum-containing solids, the disproportionation reaction 2CO {r{underscore}arrow} C{sub ads} + CO{sub 2} detected at high temperatures (a) limits the adsorption temperature and the partial pressures of CO, and (b) creates some changes in the surface of the palladium particles. The heats of adsorption of the adsorbed species determined according to the present experimental procedure are discussed in relation to data in the literature concerning various Pd-containing solids: monocrystals, model particles, and supported catalysts. Several experimental data, i.e., effects of aging of the solid, are presented and discussed in relation to the heats of adsorption of CO.

• Research Organization: Univ. Claude Bernard, Villeurbanne (FR)
• OSTI ID: 20005898
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 188; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
54 ENVIRONMENTAL SCIENCES
ADSORPTION HEAT
AIR POLLUTION CONTROL
ALUMINIUM OXIDES
CARBON MONOXIDE
CATALYSIS
PALLADIUM
SORPTIVE PROPERTIES
SYNTHESIS GAS