Hydrocracking of a Long Chain Alkyl-Cycloalkane: Role of Porosity and Metal-Acid Balance

Hydroisomerization and hydrocracking of octylcyclohexane (C14H28) were performed over Pt and NiMoS-supported catalysts, at 300 degrees C and 60 bar, with a molar H-2 to hydrocarbon ratio of 7 mol/mol. The feed, composed of 5 wt.% phenyloctane dissolved in n-heptane, was initially hydrogenated in situ over a pre-catalyst, Pt or NiMoS/Al2O3. The C-14 naphthene underwent isomerization and cracking under high hydrogen pressure over the bifunctional catalysts, whose acid function was represented by large-pore zeolities (USY, Beta) or amorphous silica-alumina (SA). For the Pt-catalysts, Beta was slightly more active than USY. Both zeolites produced a similar product pattern. Sulfide catalysts were less well equilibrated than Pt ones and hence less active. They led to some over-cracking, but the cracking selectivity of our naphthene reactant was much less sensitive to the metal-acid balance than the cracking selectivity of n-alkanes. The comparison of reactivity of octylcyclohexane with n-hexadecane and perhydrophenanthrene is also discussed.