Reaction of microporous solids: the discrete random pore model

Abstract

The universally used assumption of proportionality between reaction rate and pore surface-area is modified for application to solids dominated by micropores, where it is shown that the discreteness of the solid phase necessitates some corrections. A new discrete random pore model, which modifies the earlier random pore model results, is proposed for such solids. An exact method and two other approximate methods for predicting the evolution of pore volume distribution are discussed in light of the discrete random pore model. It is observed that the structural parameter characterizing reactivity is effectively reduced in value due to the discreteness of the solid. The new results are used to interpret the difference between reaction rate and structurally determined values of this parameter reported in the literature for the char steam reaction. The importance and need for the development of better molecular models for such systems is stressed.