Enhanced phenanthrene hydrogenation saturation performance of Ni-Co/NiAlOX catalysts and its catalytic mechanism

Hydrogenation saturation of phenanthrene was an effective method to acquire high energy density fuels. It is essential to design highly active and stable hydrogenation saturated catalyst to realize the above reaction. Herein, series of Ni-Co/NiAlOx catalysts were synthesized by reducing at different temperatures. Activity evaluation showed that the catalysts reduced at 560 °C (Cat-560) possessed a phenanthrene conversion amount of 8.0 mmol·g -1 active component·h −1 and 98% perhydrophenanthrene selectivity after running 6 h under 300 °C, 5 MPa. Furthermore, it was found that Cat-560 presented superior specific activity (4.3 mmol·kg −1 ·s −1 ) and TOF (41.1 × 10 −3  s −1 ) for symmetric octahydrophenanthrene hydrogenation (the rate determining reaction), and its specific activity was 3 times as high as that of the catalysts reduced at 520 °C The excellent hydrogenation performance of Cat-560 could be attributed to its special geometric and electronic structure. Characterization indicated that the Ni 2+ in Ni-Co/NiAlO X catalyst was mainly located in the nickel aluminum spinel octahedral sites, which was beneficial to the reduction of Ni and the formation of smaller Ni particles. Moreover, it was explored that the Ni d charge density of Cat-560 catalyst was −0.12 e, which was suitable for the adsorption and activation of phenanthrene and symmetric octahydrophenanthrene.