Kinetics of propylene hydrogenation on nanostructured palladium clusters

Surfactant-stabilised palladium nanoclusters with an average diameter of about 7.3 nm (determined by XRD) are used as catalysts in propylene hydrogenation. Experiments performed in an isothermal batch reactor (T = 308 K), with total pressures in the range 0.25-9.0 bar and with initial hydrogen molar ratios varying between 0.05 and 0.40, provide a further insight on the reaction kinetics. It is shown that a Langmuir-Hinshelwood rate equation well represents the reaction data, which mechanism involves competitive adsorption of the reagents, with dissociation of hydrogen on the catalyst surface, and where surface reaction is the limiting step. Nonlinear optimization of the initial rate data provided the kinetic parameters of the rate law (k = 5.569 mol g(Pd)(-1) s(-1); K-H2 = 3.799 x 10(-2) bar(-1) and K-C3H6 = 0.996 bar(-1)), which is validated by integration of the mass balance in the batch reactor. (C) 2004 Elsevier B.V. All rights reserved.