Hydrodenitrogenation of quinoline over Ni-Mo/Al2O3 catalyst modified with fluorine and phosphorus

In this paper, the effects of fluorine and phosphorus on the physical and chemical properties of Ni-Mo/Al2O3 catalysts and the hydrodenitrogenation (HDN) activity of quinoline were investigated. The acidity, pore structure, and dispersion of Mo of the catalysts were analyzed with TG-DTA, BET, and XRD techniques. The activities of hydrodenitrogenation and hydrogenation of the catalysts were investigated using hydrogenation of quinoline at high pressure in a micro-reactor. Experimental results verified that phosphorus can promote the formation of moderate and strong acidic sites, the dispersion of Mo, and the formation of the active phases; therefore, the hydrogenation activity of aromatic rings and the hydrogenolysis activity of C-N bonds increase. The hydrogenation and hydrogenolysis accelerate each other, which results in the increase of HDN activity. It is concluded that phosphorus is a promoter for HDN activity of the Ni-Mo/Al2O3 catalysts. Fluorine can promote the formation of weak and moderate acidic sites and the dispersion of Mo, but inhibit the formation of the active phases. Therefore, the hydrogenation activity of aromatic rings and the hydrogenolysis activity of C-N bonds decrease, which results in the decrease of HDN activity. It is concluded that fluorine is not a promoter for HDN activity of the Ni-Mo/Al2O3 catalysts. The possible promoting mechanism of fluorine and phosphorus for the Ni-Mo/Al2O3 catalyst is put forward and discussed.