DFT insights into the hydrodenitrogenation mechanism of quinoline catalyzed by different Ni-promoted MoS edge sites: Effect of the active phase morphology.

Density functional theory calculations are performed to investigate the hydrodenitrogenation (HDN) mechanism of quinoline over different Ni-promoted MoS edges. Based on the calculations, the hydrogenation and ring-opening reaction pathways are explored systematically, and the structure-activity relationship of different active sites is discussed in detail. In the hydrogenation reaction process, the 100% Ni-promoted M-edge and 50% Ni-promoted S-edge are favorable for the formations of 5,6,7,8-tetrahydroquinoline and 1,2,3,4-tetrahydroquinoline, respectively. Furthermore, the 100% Ni-promoted M-edge is more preferable for the generation of decahydroquinoline rather than the 50% Ni-promoted S-edge. In the denitrogenation reaction step, the 100% Ni-promoted M-edge is beneficial for the formation of ortho-propylaniline and 2-propylcyclohexylamine, while 50% Ni-promoted S-edge is only conducive to the formation of 2-propylcyclohexylamine. Therefore, it can be concluded that both hydrogenation derivatives and denitrogenation products exhibit strong dependence on the active phase morphology, meaning that multiple active sites can be involved in one catalytic HDN cycle.