Dynamic behavior of fixed-bed reactors with “large-pore” catalysts: A bidimensional heterogeneous diffusion/convection model

Abstract

A complete bidimensional, heterogeneous model taking into account intraparticle diffusion and convection (HT dc) was developed and used to analyze the dynamic behavior of a fixed-bed catalytic reactor containing large-pore catalysts. Results were compared with those obtained by simpler bidimensional models: HT d, a heterogeneous model which considers only intraparticle diffusion and the pseudo-homogenous (PH) model. Two situations were tested: the pseudo-steady-state approximation for the catalyst and the transient regime inside particle. The integration of model equations was carried out using the method of lines. Orthogonal collocation in finite elements was employed to discretize space coordinates: reactor axial coordinate (accomplished by available software), reactor radial coordinate and particle space position (handled by the authors). Hot spots obtained with bidimensional HT models are lower than those predicted with unidimensional models. However, the maximum temperature rise predicted by the PH model is higher than in the corresponding unidimensional PH model.