Relationships between physico-chemical properties and catalytic activity of polymer-supported palladium catalysts .2. Mathematical model

A mathematical model including external mass transport, diffusion in the particle and chemical reaction inside the particle was developed to describe a hydrogenation process in an isothermal batchwise system with a polymer-supported metal catalyst. Various types of reaction kinetics were implemented into the model, e.g., the power law or the Langmuir-Hinshelwood type. The validity of the model was tested on data obtained from the hydrogenation of a 1 M methanol solution of cyclohexene at 25 degrees C and 0.5-1.5 MPa. Diffusional coefficients inside the catalyst, the hydrogenation rate constant and the adsorption constant of hydrogen were estimated. The best model proved to be the model considering the dissociation of hydrogen and neglecting the adsorption terms in the denominator of the Langmuir-Hinshelwood kinetics. Using polymer supports of different swellability, a linear correlation between the logarithm of the diffusional coefficient of a solute inside the polymer and the reciprocal of the swelling volume of the polymer support was derived from ESR measurements. A comparison with values of diffusional coefficients obtained from catalytic tests confirmed the validity of this correlation.