Synthesis of Ni/NiAlOx Catalysts for Hydrogenation Saturation of Phenanthrene.

The saturation of octahydrophenanthrene was the rate-determining step in the hydrogenation process from phenanthrene to perhydrophenanthrene, which was due to the steric hindrance and competitive adsorption of octahydrophenanthrene. In this work, a series of Ni/NiAlOx catalysts with a uniform electron-deficient state of Ni derived from the nickel aluminate structure was synthesized to overcome the disadvantage of noble catalyst and the traditional sulfided catalysts in the saturation hydrogenation process of phenanthrene. Results showed that the catalyst calcinated at 650°C possessed more Ni2+ (∼98%) occupying octahedral sites and exhibited the highest robs (1.53 × 10-3 mol kg-1 s-1) and TOF (14.64 × 10-3 s-1) for phenanthrene hydrogenation. Furthermore, its ability to overcome steric hindrance and promote the rate-determining step was proven by octahydrophenanthrene hydrogenation. Comparing the evolution of hydrogenation activity with the change in the electronic structure of surface Ni sites, it was shown that the increase of metallic electron deficiency hindered the π-back bonding between surface Ni and aromatic rings, which was unfavorable for aromatic adsorption. As a result, the phenanthrene hydrogenation saturation performance can be enhanced by stabilizing the electron-deficient state of surface Ni on an optimal degree.

Naphthalene Hydrogenation Saturation over Ni2P/Al2O3 Catalysts Synthesized by Thermal Decomposition of Hypophosphite.

A series of Ni2P/Al2O3 catalysts with different Ni2P loadings were synthesized via thermal decomposition of hypophosphite and employed for naphthalene hydrogenation saturation. Results showed that Ni2P loading greatly affected Ni2P particle size and the number of active sites of the as-synthesized catalysts, which was derived from the variable interaction between POx and Al2O3. When the hydrogenation saturation reaction was performed at 300 °C, 4 MPa, a H2/oil volume ratio of 600, and a liquid hourly space velocity (LHSV) of 3 h-1, 98% naphthalene conversion and 98% selectivity to decalin were achieved over Ni2P/Al2O3 catalysts with 10 wt % Ni2P. The superior naphthalene hydrogenation saturation performance was ascribed to the large specific surface area (169 m2·g-1), small Ni2P particle size (3.8 nm), and the high number of exposed active sites (CO sorption 30 µmol·g-1), which were beneficial to the adsorption and diffusion of the reactant molecules on the catalyst.