Heavy oil hydroprocessing requires catalysts with enhanced mesoporosity and moderate acidity. Mesostructured aluminum modified SBA-15 have been identified as suitable catalytic supports for sulfided phases employed in this process. In this work, a series of SBA-15 based materials were synthesized using hexane as a micellar swelling agent for pore widening. Particularly, the effect of the hexane to Pluronic P123 mass ratio on key properties was assessed. Among the synthesized materials, the one prepared with a hexane: P123 mass ratio of 3.5 showed the best textural properties: BET surface area = 499 m(2) x g(-1), total pore volume = 1.8 cm(3) x g(-1), and average pore diameter = 27 nm. The acidity of this material was further modified by grafting aluminum over it. The resulting materials were employed as supports for sulfided Fe-W tested in the hydroprocessing of phenanthrene at 11 MPa and 623 K. Catalysts activity was found to related to the dispersion of the oxide precursor of the active metals which in turn was dependent on Al/Si molar ratio of the supports. Catalysts promoted the formation of 9,10-dihydrophenanthrene, a reaction intermediary in phenanthrene hydroprocessing. The catalyst with an Al/Si molar ratio of 0.04 showed the highest selectivity to this compound. The latter was correlated to a higher content of tetrahedral aluminum in the support. In general, the modifications performed over the SBA-15 support enhanced their pore size distributions and acidity and promoted the selective partial hydrogenation for the central ring of phenanthrene. The findings are important for the search of new catalysts in heavy oil hydroprocessing. Graphical Abstract [GRAPHICS] .