Article,
Catalytic effectiveness of irregular interfaces and rough pores: the ``land surveyor approximation''
CHEMICAL ENGINEERING SCIENCE, 56 (17): 5011-5023 (2001)
DOI: 10.1016/S0009-2509(01)00165-8
Abstract
We apply the concept of active zone in Laplacian transport to
investigate the steady state mass transfer of a diffusive species
towards an arbitrarily irregular catalytic interface. By means of a
recently proposed coarse-graining technique, it is possible to compute
the reactive flux on the catalytic interface from its geometry alone.
without solving the general Laplace problem. As a result, we demonstrate
by direct numerical simulation of molecular diffusion and first-order
reaction that this method allows one to predict the catalytic
effectiveness of a slit-shaped pore with an arbitrary rough geometry and
over a wide range of diffusion-reaction conditions. It is found that.
contrary to the traditional pseudo-homogeneous approach. the effect of
the irregular morphology at the mesoscopic pore level is to modify the
reaction rate and not the effective diffusion coefficient. We show that,
for all practical situations where the reactant penetration in the pore
is significant. a simplified picture of a smooth pore with an effective
reactivity k(eff) can be used to describe the efficiency of a rough
pore. Remarkably, k(eff) is the product of the intrinsic reactivity by a
screening factor S, which has an elementary geometrical meaning, namely,
the ratio between the real and the apparent surface area. (C) 2001
Elsevier Science Ltd. All rights reserved.
