A mathematical model was constructed for the analysis of how the porous structure parameters of a reforming catalyst grain affect catalytic efficiency. The physical model of the grain (layered model, bidispersive) and the kinetic scheme of the process simplify, the real image of the phenomenon; however, the conclusions drawn from the analysis of the mathematical model and from relevant assumptions are consistent with the overall knowledge gained in this field and make the model applicable to the analysis of the properties of bidispersive systems. The model includes (and compares) the results for three different hypothetical kinetic schemes that involve pseudo-reactions of group components. In every instance.. the mathematical model responded in a similar, qualitative way to any change in the values of the porous structure parameters. However, the choice of the most probable kinetic scheme that may be useful in optimizing the porous structure must be supported by experimental verification.