Pore-Structure Engineering of Hierarchical Ni/Y Catalysts for the Enhanced Selective Hydrocracking of Naphthalene to BTX

Abstract

Selective hydrocracking of naphthalene over bifunctional catalysts is promising for the upgrading of polycyclic aromatic hydrocarbons into high-value BTX. The key to achieving high hydrocracking activity and BTX yield is to design bifunctional catalysts with moderate hydrogenation and ring-opening cracking capability, which relies on appropriate acid and textural properties as well as suitable metal–support interactions. Herein, we designed hierarchical Ni/PTY (post-treatment Y) catalysts with open hierarchical pore structure, moderate acidity and highly dispersed small-sized Ni species via the pore-structure engineering of Y zeolites and the ethylenediamine-assisted impregnation strategy. The open hierarchical pore structure and tunable acidity of Ni/PTY catalysts optimized the balance between metal–acid sites, which was beneficial to the selectivity of the hydrogenation route, isomerization route and cracking route. As a result, the optimized Ni/PTY catalysts showed a superior naphthalene conversion of 88.7% and BTX yield of 62.5% with high turnover frequency values (TOF, 14.5 h^–1) and reaction rate constants (k_HCK, 2.8 h^–1). Furthermore, the possible reaction pathway and mechanism was proposed and studied for such Ni/PTY catalyst system.