Kinetics of cinnamaldehyde hydrogenation-concentration dependent selectivity

For the isothermal hydrogenation of cinnamaldehyde over Pt/C/monolithic catalysts three kinetic models have been evaluated, each model based on different sets of assumptions. A single-site and a two-site model with the surface reactions as rate-controlling steps were unable to describe the experimental data satisfactorily, while a single-site model with adsorption, surface reactions, and desorption all rate controlling could describe the experimental data adequately. This model includes apparent direct reaction steps from reactant to various end-products, due to the competition between desorption and subsequent conversion of intermediates at the catalyst surface. The selectivity to the unsaturated alcohol increases with increasing reactant concentration, which is ascribed to a change in adsorption mode, possibly due to some assembling phenomena of the reactant at the catalyst surface. (C) 2001 Elsevier Science B.V. All rights reserved.