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 °C and 60 bar, with a molar H2 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 C14 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. In the hydrocracking of cyclohexane with a long alkyl side chain over different bifunctional catalysts, i. e. zeolites USY, beta and silica‐alumina, the main reaction pathway is the generation of additional branchings on the naphthene ring, followed by exocyclic cracking into a long, branched paraffin and a substituted naphthene ring. In contrast to a bulkier three‐ring naphthene reactant, little shape selectivity is observed in the product distribution.