Controlled growth of graphene on γ-Al2O3 as highly efficient nanocomposite support of NiMoW catalysts by engineering approaches of chemical vapor deposition technique for hydrotreating of vacuum gas oil

Abstract

In this study, a novel γ-Al2O3@Graphene-Cu nanocomposite support has been successfully prepared by the CVD method with a mixed gas of methane/hydrogen to improve hydrotreating (HDT) activities further and explore the metals-support interaction. Furthermore, the impacts of physicochemical properties (specific surface areas, pore volumes, average pore diameter, and acidity) in increasing the efficiency of γ-Al2O3@Gr-Cu nanocomposite catalysts in the HDT reactions of DBT/Quinoline model fuel and vacuum gas oil (VGO) have been thoroughly investigated. It has been found that growing graphene on γ-Al2O3 could reduce particle size and expand the specific surface area of γ-Al2O3@Gr nanocomposite catalysts, resulting in higher HDT activity. Raman spectroscopy, XRD, HR-TEM, SEM, BET surface, ICP, TPD, and TPR techniques with a view to linking catalytic activities with the synthesis method and Mo/W ratio were used to fully characterization of the prepared nanocomposite catalysts. Catalytic activities of γ-Al2O3@Gr-Cu nanocomposite are studied by varying operating conditions in the hydrotreating of VGO feedstock. It transpires that NiMo3W10/γ-Al2O3@Gr-Cu nanocomposite catalyst with the highest turnover frequency (3.8×104 s−1), high surface area (330 m2. g−1), large pore size (95.8 Å), and acidity (1.92 mmol NH3 g−1) have the best adsorption properties compared with a commercial catalyst which lead to an increase in the synergistic effect in trimetallic NiMoW catalysts related to the tighter interaction between W and Mo, which enhanced the solidification degree of metal and was also ascribed to the organization of significantly active mixed NiMoWS sites.