Modeling of gas transport in a microporous solid using a slice selection procedure: Application to the diffusion of benzene in ZSM5
Abstract
The analytical solution of the equations of gas diffusion in a heterogeneous zeolite bed is presented. The
problem is handled by assuming that the bed consists of a large number of very thin layers of solid,
perpendicular to the direction of propagation of the gas. Mass transfer by diffusion in such a material is
determined by a system of differential equations with boundary and interface conditions. The results
allow us to make the theoretical determination of the time dependence of the concentration profiles and
the inter- and intracrystallite diffusion coefficients of a gas in each layer of the bed. A numerical
application concerns the diffusion of benzene in a cylindrical bed of ZSM5 displaced vertically and
rapidly, step-by-step, inside the NMR probe. Thus, the time dependence of the concentration of gas
absorbed at the level of each slice and each crystallite can be obtained. These coupled investigations give
a better understanding of the diffusion process in this multilayer material.