Experimental and theoretical study of NiMoW, NiMo, and NiW sulfide catalysts supported on an Al-Ti-Mg mixed oxide during the hydrodesulfurization of dibenzothiophene
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This work presents a comparative study of the structural, textural, superficial, morphological, electronic, and catalytic properties of NiMo, NiW and NiMoW/AlTiMg sulfide catalysts during the hydrodesulfurization (HDS) of dibenzothiophene (DBT). The AlTiMg mixed oxide support was synthesized by the sol-gel method, the catalysts were synthesized by the co-impregnation method using an atomic ratio of Ni = Ni/(Ni + metals) = 0.5 and a molar ratio of Mo:W (1:1). The materials were characterized by XRD, FT-IR spectroscopy, FT-IR pyridine adsorption, N2 physisorption, UV-Vis DRS, Raman spectroscopy and SEM. The catalytic activity was evaluated using a high-pressure batch reactor at 350 C and 3.1 MPa. The catalyst surfaces were analyzed using Density Functional Theory (DFT) to elucidate their activity differences. The catalytic activity during HDS-DBT indicated that the best catalyst was NiMoW. This catalyst exhibited adequate pore size and high specific surface area, coupled with the presence of Ni, Mo and W species in octahedral coordination, as well as good morphological properties. DFT calculations revealed that the NiMoW catalyst surface possesses unique electronic properties, such as the lowest surface energy and the highest density of d-type states over the Fermi level compared to NiMo and NiW catalyst surfaces. 2013 Elsevier Ltd. All rights reserved.