Effect of preparation method of nanosized zeolite HY-Al₂O₃ composite as NiMo catalyst support on diesel HDS

Two NiMo catalysts using the nanosized zeolite HY-Al₂O₃ composite (labeled as NYA) prepared by mechanical mixing method and sol-gel method as the support were prepared and characterized by XRD, BET, TPD, H₂-TPR, HRTEM and FT-IR spectroscopy. The former catalyst possessed larger pore volume and specific surface area, more acid amount, superior reducibility of metal phase and higher dispersion of edge and corner Mo atoms, and showed higher hydrodesulfurization (HDS) performance. Compared with the former catalyst, the latter catalyst had more MoO₃ to be converted to active type-Ⅱ NiMoS phase, possessed higher stacking degree and bigger length of MoS₂ slabs, and showed lower active phase dispersion. Although the sol-gel method was beneficial to increase the precursor ratio of type-Ⅱ NiMoS phase, the poor pore structure caused by this method inhibited this advantage and reduced the catalytic activity of the catalyst.