A simple jump model for describing the molecular traffic control effect

Derouane and Gabelica postulated in the concept of 'molecular traffic control' (MTC) an enhancement of the effective conversion rate in catalytic reactions if the reactant and product molecules avoid each other by preferentially choosing different channel systems on their diffusion path into and out of the catalytic particles. As a main deficiency of this concept, so far no clear theoretical criteria for the occurrence of this effect are known. In the present communication, we consider a network of channels with single-file confinement and selective adsorption affinity to either the reactant or the product molecules as a model with which for the first time the possibility of reactivity enhancement by MTC may be rigorously demonstrated. The molecular distributions are analyzed over the different elements of the channel system in dependence on the intrinsic reactivity and the pore filling factors. The obtained patterns are compared with those of a reference system where all channels are equally accessible by the reactant and product molecules. Attention is also given to the effect of particle self-blockages under MTC, which occurs for large intrinsic reactivity and great pore filling factors. It is demonstrated that under these conditions the simulations end up in an immobilized state, which is a function of the particular simulation run. Such behavior is an artifact of the used jump lattice model and is observable for the MTC system but not for the reference system. (C) 2001 Elsevier Science B.V. All rights reserved.