Metal chlorides supported on silica as efficient catalysts for selective isomerization of endo-tetrahydrodicyclopentadiene to exo-tetrahydrodicyclopentadiene for JP-10 producing

A series of heterogeneous catalysts based on different metal chlorides (AlCl3, NbCl5, ZnCl2) immobilized on silica gel have been prepared. The catalytic activity of obtained catalysts for the isomerization of endo-tetrahydrodicyclopentadiene (endo-THDCPD) to its exo-isomer (exo-THDCPD, the main component of JP-10 fuel) has been investigated in detail. The physicochemical properties of the catalysts were studied by SEM, low temperature nitrogen adsorption, NH3-TPD. Supported AlCl3 exhibited the excellent catalyst activity and a high selectivity without side-reactions such as skeletal rearrangement, alkylation, etc., whereas NbCl5 and ZnCl2 immobilized on SiO2 showed much less catalytic activity. It was found that addition of alkyl halides such as 1,2-dichloroethane reduced catalytic activity. Using the optimized catalyst system, the isomerization of endo-THDCPD to exo-THDCPD was performed under mild conditions (50 °C) at a fast rate, with more than 98% conversion and selectivity higher than 99%. Thermodynamic and kinetic parameters of the endo-exo isomerization reaction were determined.