On the effectiveness factor calculation for a reaction – diffusion process in an immobilized biocatalyst pellet

Abstract

This contribution deals with effectiveness factor ( η) and concentration profile of key component estimations when a single independent reaction takes place in a porous catalyst structure where enzymes are immobilized. The procedure is quite general since any kinetic expression can be handled and the case of catalytic activity distribution can also be taken into account. With the knowledge of kinetic parameters and effective diffusivity η and concentration profiles can be estimated through very simple algebraic equations. Thus, the numerical solution of a non linear second order boundary value differential equation, which usually needs some spline scheme, is avoided. The obtained approximate results are compared with numerical findings for the case of slab geometry where a very simple numerical procedure can be used to solve the resulting differential non linear equation. Approximate results are shown very accurate in the whole range of kinetic parameters, even in those cases where the reaction kinetics shows an apparent negative order of reaction and η values can be above unity. Tables are used to better compare approximate and numerical values. Concentration profile predictions are also very accurate in the region nearby the external surface of the catalyst particle. These approximate results are used to establish criteria to analyze experimental kinetic data in those cases where diffusional phenomena, that could affect chemical parameter estimations, must be avoided.