The purpose of this study is the development and simulation of a mathematical model describing species reaction and transport, as well as energy transport at the pellet-scale. Mass, momentum, and energy are continuously interchanged between the gas phase surrounding the pellets and the catalyst pelletsâ?? gas and solid interior. The velocity, temperature, and speciesâ?? concentration profiles within the catalyst pellet can be captured by momentum/energy/species transport models accounting for convection/conduction/reaction/diffusion mechanisms. The dusty gas model is combined with speciesâ?? and energy transport equations to derive the pellet-domain model. Investigation of pressure effects, pellet size, and pore distribution on species transport along the pellet radius is conducted. The effectiveness factor of each species is calculated.