Abstract: Two kinds of typical C₉+ heavy aromatic hydrocarbon feedstocks were selected for hydrocarbon composition analysis. The analysis results showed that trimethylbenzene and ethyltoluene were the major component in the C9+ heavy aromatic hydrocarbon feedstocks. Therefore, trimethylbenzene and ethyltoluene were selected as model compounds to calculate the standard molar reaction enthalpy change, standard molar Gibbs free energy change, and standard equilibrium constant of the hydrodealkylation reactions in the temperature range of 350-650 ℃, and the thermodynamic calculation results of dealkylation reaction were analyzed. The results indicated that the hydrodealkylation reactions of trimethylbenzene and ethyltoluene were exothermic reaction within the temperature range of 350-650 ℃, and the exothermic energy of the reactions was negatively correlated with the symmetry of the molecular structure, which might be related to overcoming the steric hindrance of methyl or ethyl groups. The dealkylation of trimethylbenzene and ethyltoluene can be carried out spontaneously in standard conditions, meanwhile the equilibrium constants of the reactions gradually decreases with the increase of reaction temperature.

Key words: C₉+ heavy aromatic hydrocarbon, hydrodealkylation, trimethylbenzene, ethyltoluene, reaction thermodynamics