DIFFUSION AND REACTION IN 3-DIMENSIONAL NETWORKS - GENERAL KINETICS

During the last ten years design of catalyst particles and porous stru ctures has made considerable progress. Because of the complicated inte raction of diffusion and reaction in catalysts there is a demand for m ore detailed models of porous structures. We have taken a three-dimens ional network of interconnected cylindrical pores as pore model. Other pore structures, e.g. slit pores, could also be taken. The network ha s a predefined pore radii distribution, connectivity and porosity. Mas s transport in the single pores of the network is described by the dus ty-gas model. Unlike in previous publications, the present network mod el can be applied to any reaction kinetics. To solve the mass balances of the whole network, the mass balances of the single pores of the ne twork have to be salved simultaneously, because these single mass bala nces are coupled by the boundary conditions in the nodes of the networ k. At each node of the network a condition similar to Kirchhoff's Law has to hold. At the outer nodes of the network boundary conditions eit her of the Dirichlet type or the Neumann type can be formulated. The r esulting system of differential equations has been solved by the finit e-difference method. This leads to a large system of non-linear equati ons. To solve this non-linear system a damped Newton method has been a pplied.