High hydrogenation performance of the mesoporous NiMo/Al(Ti, Zr)–HMS catalysts

Hexagonal mesoporous silica (HMS) material with and without Al, Ti and Zr ions (Si/X, X = Al, Ti or Zr atomic ratio of 40) were used as support for the preparation of the hydrotreating NiMo catalysts. The samples were characterized by 29Si NMR, SBET, XRD, HRTEM, Raman spectroscopy, FT-IR spectroscopy of adsorbed NO on freshly sulfided samples, XPS of the used samples and H2 chemisorption. The catalytic activity of the samples was evaluated in the reaction of hydrogenation of naphthalene. All samples showed high hydrogenation activity in the first step of the reaction when tetraline is formed. However, in the second step of the reaction leading to the formation of cis-decaline and trans-decaline, the presence of Al, Ti and Zr ions increased the hydrogenation ability of the samples. The NiMo/HMS and a reference (NiMo/γ-Al2O3) catalysts were good for mild hydrogenation (tetraline formation), while in the NiMo/(Al, Ti, Zr)–HMS catalysts were superior when deep hydrogenation is necessary (cis-decaline and trans-decaline formation). We found three interesting correlations, (i) oxidized Ni species in the sulfided samples with the deep (complete) hydrogenation (tetraline to decalines), (ii) the dispersion of the sulfided Ni and Mo species with the rate constant of the naphthalene consumption and, (iii) the population of MoOT species (Tterminal bonding) with the second hydrogenation step (tetraline transformation to decaline).