Kinetics of the NO+H-2 reaction over supported noble metal based catalysts: Support effect on their adsorption properties

摘要

This paper reports a kinetic investigation of the global reduction of NO by H-2 which has been considered as a probe reaction for characterising the adsorption properties of supported palladium based catalysts. A particular attention has been paid towards the influence of the support on the catalytic properties of Pd, particularly towards the production of undesirable by-products such as nitrous oxide (N2O) and ammonia (NH3). It has been found that the kinetics of the overall NO + H-2 reaction on Pd/Al2O3 can be correctly depicted according to a Langmuir-Hinshelwood mechanism involving the dissociation of nitrosyl species assisted by chernisorbed hydrogen atoms. On the other hand, Pd/LaCoO3 exhibits a different kinetic behaviour towards the adsorption of hydrogen depending on the pre-activation thermal treatment. In that case, different mechanisms may occur. (c) 2006 Elsevier B.V. All rights reserved.