Selective Hydrogenation of Naphthalene over γ-Al2O3-Supported NiCu and NiZn Bimetal Catalysts

A series of Cu and Zn modified Ni/Al2O3 catalysts were prepared using an incipient impregnation method for the selective hydrogenation of naphthalene into tetralin. X-ray diffraction (XRD), H2-Temperature programmed reduction (H2-TPR), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were applied to reveal the structure regulation, and density functional theory (DFT) calculations were performed to investigate the electronic effect and reactant adsorptions on the active sites. The results showed that the addition of CuO promoted the hydrogenation of naphthalene with an inhibited tetraline selectivity. However, a simultaneously increasing naphthalene conversion and tetraline selectivity were achieved over the Zn modified Ni/Al2O3 catalysts. The characterization and calculation results revealed that the doping of CuO improved the hydrogenation activity with a low tetralin selectivity due to the H spillover from the Cu. The addition of ZnO decreased the interaction between NiOx and Al2O3 in NiZn/Al2O3 catalysts, which efficiently increased the reduction ability of NiOx species and, thus, improved the naphthalene hydrogenation activity. The electron transfer from ZnO to NiOx weakened the adsorption of tetraline and resulted in increased tetraline selectivity. This work provides insight into developing efficient catalysts for heavy aromatics conversions via rational surface engineering.