Metropolis Monte Carlo technique has been applied to simulate the crystallization process in the melt of vanadium sulfuric acid supported catalysts. The inch is a lattice binary compound consisting of (V4+)(2) and (V5+)(2) binuclear complexes (dimers) confined by pore walls of cylindrical or slitlike shape. It has been shown that the crystallization process retards significantly as the pore size decreases. This result is in good agreement with the experimental data obtained earlier. The effect of the energy properties of pore walls (attractive, repulsive, or inert) on the crystallization features has been studied as well.