Role of ZrO2 and Porosity Induced by Activated Carbon and Starch Templates in NiMo/Al2O3-ZrO2 Catalysts for Naphthalene Hydrogenation and 4,6-Dimethyldibenzothiophene Hydrodesulfurization

The influence of zirconia incorporation and template type on the physicochemical properties of NiMo/Al2O3-ZrO2 catalysts was investigated for the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and the hydrogenation (HYD) of naphthalene (N). Catalysts were prepared by co-impregnation on supports synthesized via a sol-gel method using starch (A) and activated carbon (C) as structure-directing templates, followed by zirconium incorporation through a grafting procedure. The resulting materials were characterized by SEM–EDX, N2 physisorption, H2-TPR, XPS, HRTEM, and pyridine-FTIR. SEM-EDX confirmed homogeneous metal distributions and compositions close to nominal values (Mo = 20 wt%, Ni = 5 wt%, Zr = 11 wt%) with Ni/(Ni + Mo) = 0.30. N2 adsorption–desorption isotherms correspond to type IV(a) with H3-H4 hysteresis loops, characteristic of mesoporous structures. After metal incorporation, surface areas decreased to 96 m2 g−1 for NiMo/Al2O3 and 81 m2 g−1 for Zr-modified catalysts, while the activated carbon-templated sample preserved a larger mesoporous volume (0.335 cm3 g−1) and higher macroporosity (72%). H2-TPR profiles indicated improved reducibility for Zr-containing catalysts. XPS revealed an increase of MoS2 species from 45% in NiMo/Al2O3 to 75% in NiMo/Al2O3-ZrO2(C), accompanied by a higher degree of sulfidation index (DSI) from 47.1% to 73.9%. HRTEM analysis of Zr-modified catalysts revealed longer MoS2 slabs (11.8–12.1 nm) and higher edge-to-corner ratios (17–17.4) compared with NiMo/Al2O3 (6.2 nm; fe/fc = 8.2). Pyridine-FTIR showed a substantial increase in total acidity from 91 to 421 μmol g−1 upon Zr addition. Catalytically, NiMo/Al2O3-ZrO2(C) exhibited the highest HDS conversion (40%), reaction rate (10.5 × 10−9 mol s−1 g−1), and TOF (4.69 × 10−5 s−1), whereas NiMo/Al2O3-ZrO2(A) reached the highest naphthalene conversion (97.18%), with a reaction rate of 27.4 × 10−7 mol s−1 g−1 and TOF of 12.9 × 10−3 s−1. These results demonstrate that Zr incorporation and the activated carbon template favored hydrodesulfurization, whereas the starch template promoted hydrogenation performance.