Thermodynamic equilibrium analysis of ring opening of decalin

Abstract

Thermodynamic equilibrium calculations were carried out in order to understand the effect of temperature and hydrogen-to-hydrocarbon ratio on the yield and selectivity of ring opening products that are obtained from hydrocracking of decalin. Thermochemical analysis of single hydrocracking reactions involving selected alkanes and naphthenes indicates that endocyclic cracking of naphthenes is less favored than acyclic and exocyclic cracking reactions due to entropy considerations. The equilibrium calculations were performed in the temperature range 298–800K at a pressure of 1bar for a mixture of compounds obtained from hydrocracking of decalin using the assumption that the reaction mixture behaves as an ideal gas. The quantum chemical method G3MP2 was used to calculate the standard Gibbs free energy of formation for compounds for which thermochemical data are so far unavailable in the open literature. The results from equilibrium calculations indicate that, as long as cracking (CR) and dehydrogenation (DH) products are allowed to form simultaneously, total ring opening (TRO) products cannot be present in the reaction mixture in appreciable concentrations. If the pathways leading to the formation of CR products are excluded from the equilibrium calculations, the yield of TRO products reaches a significant value of ∼0.75kg/kg decalin fed in the temperature range 400–500K. The highest yield of TRO products, ∼1kg/kg decalin fed, observed for a hydrogen-to-hydrocarbon ratio of 4 in the temperature range <500K could be the maximum achievable yield for TRO products of decalin. The TRO products consist mostly of saturated ring opening (SRO) products and traces of unsaturated ring opening (USRO) products.