Regulating metal–acid active sites in hierarchical porous Ni/Y for selective hydrocracking of naphthalene

• Bifunctional hierarchical porous Ni/RCY catalysts with different metal–acid active sites were synthesized for the selective HCK of naphthalene. • The larger external surface area and mesoporous structure facilitate the dispersion of Ni species and lower mass transfer resistance. • Catalysts with optimized acid properties and MSI could expose more active sites for HDG and cracking and improve selective HCK performance. • The adsorption and reaction mechanism of naphthalene selective HCK were investigated and proposed. • Ni/RCY-4 exhibited excellent performance with the highest BTX yield of 39.1 % and higher naphthalene conversion of 99.7 %. The preparation of high efficiency hydrocracking (HCK) catalyst is the key to the production of BTX (benzene, toluene and xylene) from polycyclic aromatic hydrocarbons (PAHs). In this work, the recrystallized Y zeolite (RCY) was obtained by structural reorganization of the microporous parent Y zeolite (PY), and a series of Ni/RCY catalysts with different metal–acid active sites were prepared by ethylenediamine coordination impregnation, which were used for the BTX production by hydrocracking of naphthalene. The suitable acidity and hierarchical pore structure of Ni/RCY could promote the dispersion of Ni metal, thus forming small-sized nanoparticles, which is in favor of the accessibility and diffusion of naphthalene. Besides, the electron-deficient Ni species between adjacent acid sites and metals could be generated on Ni/RCY, which could improve the metal-support interaction (MSI) and catalytic activity. Ni/RCY-4 catalyst showed the superior hydrocracking conversion (99.7 %), BTX yield (39.1 %), the reaction rate constant (k, 3.1 h −1 ) and turnover frequency (TOF, 16.6 h −1 ) of selective hydrocracking. The activation energy was lowest (64.1kJ·mol −1 ) among the reported catalysts in the literature. Moreover, the possible reaction mechanism of selective hydrocracking of naphthalene to BTX was further proposed.