Preparation And Performance Of Silica Supported Molybdenum Catalyst Added Ti For Hydrodenitrogenation

The removal of nitrogen in petrolenum fractions has become a paramount problem in the refining industry as result of continuous decline in quality of petroleum feedstocks and increasingly stringent environment regulations.In addition,nitrogen-containing compounds significantly reduce the activity of catalysts for hydrodenitrogenation(HDN).Transition metal phosphides have recently been the focus of research due to its higher activity compared to metal sulfide for HDN.Molybdenum phosphide was chosen as the HDN catalysts in the present dissertation because it is reported to have the highest activity among transition metal phosphides.Moreover,the effect of TiO₂ addition to supported molybdenum phosphide catalysts on the HDN was investigated.The catalysts were characterized by TEM,XRD,TPR. The main contents are as follows:A series of SiO₂-supported molybdenum phosphide catalysts with initial Mo/P atomic ratio of 0.5-2 and loading level of 15-35wt%in the oxidic precursors were prepared by an in-situ reduction method.Quinoline is easily hydrogenated to DHQ on molybdenum phospides catalysts.The activity of hydrogenation reaction is higher than that of the C-N breaking and the C-N breaking is the rate-controlling Step for quinoline HDN on MoP/SiO₂.It is found that the supported MoP catatlysts prepared by in-situ reduction method is superior to that by the convention reduction-passivation-reduction method in HDN.A series of supported molybdenum phosphide catalysts containing TiO₂ were prepared by two methods and investigated in HDN of quinoline.The activity of molybdenum phosphide for quinoline HDN increased significantly by the addition of TiO₂.The activity of supported MoP containing TiO₂ is much higher than that of supported MoP.TiO₂ enrichment on the surface of the catalysts was observed,which may play an important role in the enhancement of HDN activity.The product distribution analysis suggested that the ability of both hydrogenation and C-N breaking is enhanced by the addition of TiO₂.The synergetic effect of TiO₂ and molybdenum phosphide was observed.The increase in the quinoline HDN activity may be attributed to higher electron density caused by the transfer of the electron in Ti³⁺species to molybdenum phosphide.