Chemical Engineering Science, Vol.54, No.20, 4535-4546, 1999
Pattern formation in homogeneous and heterogeneous reactor models
This work qualitatively and quantitatively compares spatiotemporal patterns in homogeneous and heterogeneous models of a fixed catalytic bed for reactions with oscillatory kinetics. Pattern selection is based on the oscillatory or bistable nature of the kinetics and on the nature of fronts. The heterogenous model can exhibit local bistability while the homogeneous model does not admit this property: when flow terms are accounted for both models can be approximated by a cell-model suggesting a simple conversion between the parameters of both models. The parameter-conversion approximation (1/Pe,(eff) = 1/Pe + 1/beta, where beta is the external transport parameter) can predict quite well the dynamics of the heterogenous model with a pseudohomogeneous one when beta much greater than Pe, but it fails when both parameters are comparable. The dynamic behavior is sensitive to the boundary conditions applied. Several qualitative differences between the two models are pointed out.