DIFFUSION-CONTROLLED, HETEROGENEOUS REACTION IN A MATERIAL WITH A BIMODAL PORESIZE DISTRIBUTION

Authors
Citation
M. Loewenberg, DIFFUSION-CONTROLLED, HETEROGENEOUS REACTION IN A MATERIAL WITH A BIMODAL PORESIZE DISTRIBUTION, The Journal of chemical physics, 100(10), 1994, pp. 7580-7589
Citations number
14
Categorie Soggetti
Physics, Atomic, Molecular & Chemical
ISSN journal
00219606
Volume
100
Issue
10
Year of publication
1994
Pages
7580 - 7589
Database
ISI
SICI code
0021-9606(1994)100:10<7580:DHRIAM>2.0.ZU;2-U
Abstract
A theoretical analysis is developed for diffusion-controlled heterogen eous reaction in a material with a bimodal poresize distribution. A co nfigurational averaging procedure is used to describe a sparse, random network of macropore capillaries contained in a reactive, otherwise h omogeneous matrix. The analysis is valid for a wide range of reactivit ies, and is particularly suited for conditions where reactant concentr ation varies on a length scale comparable to the diameter of, or the s pacing between the macropores. The results depend on the reactivity on the matrix, the void volume of the macropore network, and the macropo re to matrix diffusivity ratio. A local effectiveness parameter, which depends on the reactivity and macropore void volume, characterizes th e reaction behavior in the material. An exact numerical solution is ob tained that depends analytically on the parameters of the problem, and an accurate analytical representation is derived that depends very si mply on the local effectiveness, the macropore void volume, and the di ffusivity ratio; typical results are presented. The solution reduces t o simplified models of the heterogeneous reaction in the low- and high -reactivity limits, where reactant concentration varies on a length sc ale that is large compared to the macropore spacing or small compared to the macropore diameter.