MODELING THE COMPLEX PROBLEM OF INTRACRYSTALLINE DIFFUSION AND 1ST-ORDER PHENOMENA IN MICROPOROUS SOLID PARTICLES UNDER CONSTANT-VOLUME VARIABLE-CONCENTRATION CONDITIONS

Microporous solids with pore diameters comparable to effective molecul ar cross-sections are mainly used as both stereo-selective adsorbents and shape-selective catalysts. Often complex phenomena govern the over all rate of processes of both physical adsorption and catalytic reacti on. Transport and reaction rates are usually determined independently of each other. In contrast to this procedure, this paper describes a w ay to model such phenomena comprising internal diffusion in microporou s particles coupled with any first-order rate process inherent both in the physical system, i.e. sorption system with nonlinear sorption iso therm and any particle size distribution, and the experimental apparat us characteristics. Modelling and complete solution of the models for both constant and variable boundary conditions were carried out by mea ns of non-linear Volterra integral equations. It becomes possible to d etermine both the diffusion coefficients and rate constants of constit uents of a complex process using only one experimental arrangement. Th e approach is incorporated into the software ZEUS (zeolite uptake simu lator).