DETERMINATION OF BOUNDARY CONDITIONS FOR ZERO-ORDER CHEMICAL REACTION INSIDE A SINGLE CATALYST PELLET UNDER TRANSIENT CONDITION

The transient boundary condition for a zero-order chemical reaction occurring inside a porous catalyst pellet is determined in this paper by applying a singular perturbation technique to a full transient nonequilibrium adsorption and reaction problem. The reactant exhaustion phenomenon is observed during the transient time course and the reactant-free core interface moves toward the center of the pellet. It was found in this paper that the reactant concentration is zero at the core interface and the slope of the reactant concentration profile at this interface is non-zero, and this non-zero slope of the reactant finally reaches zero when t -> infinity and phi > phi(cri), which is the steady state boundary condition used by many workers in their steady state analysis.