Different approximations to determine the kinetic of reactions involved in fluidized catalytic cracking have been developed. Given the high complexity of this process, model compounds representing the real mixtures are selected. Results for experimental catalytic cracking of methylcyclohexane (MCH) have been reported in several papers given its importance in the formation of aromatic compounds. However, detailed mechanism, and thus chemical kinetics for the specific reaction, is not well understood. This paper describes the catalytic cracking for MCH over Y zeolite, based on electronic structure simulations, taking into account different important steps such as: hydrocarbon adsorption, H+ transfer from zeolite¿s active site to hydrocarbon and C-C bond breaking, both for the ring opening, and for the cracking reaction.