gamma-Alumina is used as a catalyst for converting methanol to dimethyl ether. The process takes place in a packed or fluidized bed reactor consisting of microporous particles with distributed pore Sizes and interconnectivities. The efficiency of the process is, however, significantly, affected by the pore space structure of the particles. All the previous attempts for modeling this phenomenon have used continuum formulation of the problem based 017 classical equations of mass transport and reaction, without any regards for the effect of pore space morphology. In this article, we study the catalyst's performance by developing a network model for the pore space, with distributed pore sizes and interconnectivities. The network model is used to study the effect of several parameters such as pore space morphology, concentration, and temperature on catalyst's effectiveness factor. The results will be used for reactor simulations. (c) 2008 American Institute of Chemical Engineers AIChE J, 55: 442-449, 2009