With the exception of work by Goto et al., all these earlier studies considered only a bimolecular reaction with pseudofirst-order kinetics; i.e., first order with respect to the limiting reactant and zero order for the excess reactant. Goto et al. used pseudo-nth-order kinetics. Recently, Beaudry et al. (1987) and Harold and Ng (1 987) demonstrated that pseudofirst-order kinetics can be misleading in that depletion of the supposedly abundant (zeroorder) reactant may occur within the pellet. Also recently, suggested that bimolecular kinetics, first order with respect to each reactant, is essential for hydrodesulfurization processes.
Since zero-order kinetics in actuality loses its physical meaning when the zero-order reactant is no longer in excess and other kinetic expressions are more appropriate for some commercial processes, the objective of this work is to examine the behavior of a single reaction that is first order with respect to both gaseous and liquid reactants. Emphasis is placed on elucidating the interplay between internal diffusion, reaction, and external mass transfer on the partially wetted surface, and to examine the impact of the interplay on catalyst effectiveness.
Model Development
A two-dimensional model is developed to describe the isothermal, irreversible reaction between a dissolved gas reactant A and a nonvolatile liquid reactant B within a partially wetted, uniformly active porous catalytic pellet. As illustrated in Figure , the pellet has a square cross section with each side of length S and is externally wetted about the four corners. Each of the four identical liquid films is of a uniform depth and covers an equal