The Influence of Support on the Low-Temperature Activity of Pd in the Reaction of CO Oxidation: 3. Kinetics and Mechanism of the Reaction

• Published in: Journal of catalysis Vol. 161; no. 2; pp. 517 - 523
• Main Authors: Pavlova, S.N., Sadykov, V.A., Bulgakov, N.N., Bredikhin, M.N.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.07.1996
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1006/jcat.1996.0213

The unsteady and steady-state kinetics of low-temperature CO oxidation over Pd supported on TiO2, SiO2, and Al2O3were investigated by using pulse/flow microcatalytic installation.In situFourier-transformed IR spectroscopy was used to monitor Pd surface under reaction conditions. The kinetic parameters were found to differ considerably from those typical for the high-temperature region. Room-temperature CO oxidation was demonstrated to be structure-sensitive and to proceed via interaction between weakly bound CO and oxygen located at defect centers. Analysis by a semiempirical interacting bonds method showed weakly bound forms of CO to appear due to cooperative Pd–Pd bond rearrangement induced by CO adsorption/desorption processes, while oxygen incorporation into the subsurface layer hinders this reconstruction, thus strengthening Pd–CO bond. In the range of 298–373 K, transition to a mechanism of the usual Langmuir–Hinshelwood type occurs, affecting observed kinetic features of the reaction.