The deactivation of ion-exchange resin catalysts in the alkylation of o-xylene with styrene is a result of deposition of styrene oligomers within the pores (Part I). The pore space of the virgin catalyst is first represented in the form of an interconnected capillary bulge-throat network by using mercury porosimetry data. The effect of various topological parameters of the catalyst on the performance of the catalyst is studied. The process of deposition of the byproduct is simulated by analysing the deposition profiles in the computer-generated 3D network. The experimental and simulated results are compared for different ion-exchange resin catalysts. A close agreement between the simulated and experimental results is observed.