MODIFIED LINEAR DRIVING-FORCE APPROXIMATIONS FOR CYCLIC ADSORPTION-DESORPTION PROCESSES

This work deals with linear driving force (LDF) approximations to the intraparticle pore diffusion equation assuming linear equilibrium. Two approaches are used to calculate global rate coefficients for the LDF model: the usual way where the average intraparticle concentration is calculated from the LDF model and a new one that uses the solution of the diffusion equation. The cyclic steady-state solutions to various cyclic perturbations are presented and compared for both methods. Also the global rate coefficients for processes with half-cycles of differ ent length subjected to square wave perturbations are presented. It is shown that the two rate coefficients needed to represent a cycle are practically equal. To avoid the difficulties associated with the non-u niversality, i.e. dependence on the perturbation type, of the global r ate coefficients, an instantaneous rate coefficient is presented, vali d for perturbations smoother than the square wave. (C) 1997 Elsevier S cience Ltd.