The oxidative dehydrogenation of propane (ODHP) has been extensively studied by non-steady-state kinetic experiments and by various experimental characterization techniques under conditions as close as possible to reaction conditions. It can be described in terms of the Mars-Van Krevelen mechanism. This work reports on Monte-Carlo simulations of the ODHP over VMgO catalysts, aimed at relating the main experimental insights obtained previously on the catalytic reaction to a theoretical description of the working catalyst. The "theoretical field of catalysis" is explored by handling new Monte-Carlo models with a catalytic reaction graph, 2D pattern recognition of adsorbed molecules, 3D oxygen bulk diffusion and finally the description of the selective, non-selective routes of the ODHP process.