INFLUENCE OF NON-ISOTROPIC DIFFUSION ON EFFECTIVE REACTION RATES IN CATALYST PARTICLES

Abstract

The non-isotropic diffusion and reaction problem in cylindrical particles of different cross-sections is analyzed in this contribution employing the one-dimensional Generalized Cylinder Model (1D-GCG). Such a model presents a single parameter of straightforward calculation from the geometrical magnitudes of the catalyst particles. Different but uniform values of axial and transversal effective diffusivities are assumed. The performance of the 1D-GCG model for the effectiveness factor estimation is assessed for a variety of particle shapes and a set of kinetic expressions. Maximum errors in the predictions, varying a Thiele modulus and the axial-to-transversal diffusivities ratio, are below 6% for the first order reaction and rise up to around of 9% and 11% for a LHHW (Langmuir-Hinshelwood-Hougen-Watson) expression at the verge of the appearance of multiple steady states, in the case of Raschig rings and solid circular cylinders, respectively.