Hydrocracking of 1-methylnaphthalene/decahydronaphthalene mixture catalyzed by zeolite-alumina composite supported NiMo catalysts

Various zeolite-alumina composites supported NiMo catalysts were prepared and their properties for hydrocracking of a decahydronaphthalene (decalin) solution containing 10 wt.% of 1-methylnaphthalene (1-MN) and 0.1 wt.% of dibenzothiophene were investigated in order to estimate not only hydrocracking of hydrocarbons but also isomerization and hydrogenation of 1-MN. 1-MN was converted to 2-MN for almost all the catalysts. The hydrogenation activities to form methyltetralin decreased in the order NiMo/Beta(940)60A > NiMo/Beta(980)60A > NiMo/HY(5.5)60A > NiMo/USY(390)60A > NiMo/USY(360)60A > NiMo/ZSM60A at 300 °C where Beta(940) β zeolite with SiO2/Al2O3 = 37, Beta(980) β zeolite with SiO2/Al2O3 = 500, HY(5.5) Y zeolite with SiO2/Al2O3 = 5.5, USY(360) dealuminated Y zeolite with SiO2/Al2O3 = 14, USY(390) dealuminated Y zeolite with SiO2/Al2O3 = 400, ZSM ZSM-5 zeolite with SiO2/Al2O3 = 1500, 60A alumina content in a composite support. Hydrocracking was observed at 360 °C specifically for β zeolite containing catalysts and the highest yields of benzene, toluene and xylene were obtained for NiMo/Beta(940)35A. It is elucidated that mesopore is favorable for hydrocracking and that the strength of the acid sites as well as homogeneous dispersion of metal species played an important role.