Abstract <p>This work presents the results of kinetic study of thermocatalytic degradation of decalin, acting as a model compound of cycloalkanes characteristic for the composition of heavy oil residues. The kinetic scheme of the process based on elementary stages including formation and subsequent transformation of primary molecular products was proposed and substantiated for the first time. HYmmm zeolite modified with sodium tetrachloroferrate was used as a catalytic system. The dynamics of product formation was quantitatively analyzed by chromatography-mass-spectrometry and gas chromatography to determine the dependence of the molar fraction of decalin and its derivatives on the contact time with the catalyst at 550°C. It was found that the process proceeds through the formation of primary molecular products: naphthalene, butylcyclohexane, 1-methyl-2-propylcyclohexane and 1,2-diethylcyclohexane, which are intermediate compounds and undergo further transformations to form gaseous hydrocarbons C₁–C₄, components of gasoline and kerosene-gasoil fractions. A reaction mechanism including the formation of a catalytically active complex of decalin with the catalyst and its subsequent transformations by several routes was proposed. The applied kinetic approach allowed to adequately describe the experimental data and to determine the rate constant of the process (<i>k</i> = 0.42±0.02 s^–1). The obtained results can be used for prediction of selectivity of thermocatalytic processing of heavy oil feedstock and optimization of technological parameters.</p>