Multi-cyclic hydrocarbons from biomass are sustainable alternative for jet fuel. Here we report an unexpected hydrogenated intramolecular cyclization of diphenylmethane derivatives synthesized by alkylation of bio-derived compounds. With the presence of commonly used zeolite-Pd/C dual catalyst, conventional hydrodeoxygenation (HDO) occurs to produce dicyclohexylmethane. However, when only hydrogenation catalysts like Pd/C or Ni is used, novel intramolecular cyclization takes place to produce perhydrofluorene with the selectivity as high as 96.0%. The two pathways were illustrated by step-bystep controlled reactions in detail and a mechanism was proposed to explain the reason for perhydrofluorene formation. Moreover, this intramolecular cyclization is versatile for diphenylmethane with -OCH3 or AOH group at any position. The synthesized perhydrofluorene shows density of 0.96 g/mL, much higher than any biofuels reported and even higher than the widely used high-density fuel JP-10 derived from petroleum. It is believed that this biofuel can be excellent additive to improve the density of other jet fuels. (C) 2017 Elsevier Ltd. All rights reserved.