Synthesis And Hydrogenation Performance Of Supported Transition Metal Phosphide Catalysts

In this paper, the several transitional metal phosphides supported on silica and alumina were prepared by in-situ temperature-programmed reduction (TPR) of oxidic precursors in flowing H2 in a fixed bed reactor. The precursors were obtained by co-impregnation. The forming process and structure of the phosphides catalysts were characterized by means of XRD, in-situ XRD, BET and TPR. The HDS and HDN performance were evaluated in a fixed bed flow micro-reactor using dibenzothiophene(DBT) and quinoline(Q) as the feedstock at conditions of pressure 2.0MPa, LHSV 3h-1 and H2/oil 300/1 (V/V). The effect between the HDS and HDN were investigated through different feeding procedures at the same micro-reactor. The hydrogenation activities of different catalysts were investigated and compared each other. The experimental results show that the highest HDS activity is observed at a total loading of 25wt% Ni2P, 30wt% for HDN. The best Ni/P molar ratio is 2/1.6, reduction tempreture is 600℃, H2 flow rate is higher than 80ml/min. Ni2P/SiO2 catalyst presents better hydrogenation activities in HDS and HDN alone. In the presence of Q, the conversion of DBT remarkably decrease and the direct hydrogenolysis forming BP become dominant, suggesting that the hydrogenation route of DBT yielding CHB is suppressed. In the presence of DBT, the hydrodenitrogenation of Q is also remarkably decreased. The main effect of DBT on quinoline HDN is suppressing its hydrogenation route, this shows that DBT and Q exist strong competitive adsorption in the same hydrogenation active sites. The hydrogenation activities of different catalysts is in the order of Ni2P/SiO2>NiMoP/SiO2>Ni2P/ Al2O3.The hydrogenation performance of Ni2P/SiO2 catalyst was evaluated using FCC gasoline and FCC diesel oil as the feed. The results show that HDS of FCC diesel oil is 80.7%, HDN is 45.6%, and its hydridenitrogenation activity is higher than traditional CoMoWS/γ-Al2O3 catalyst at the condition of 360°C, 4MPa, LHSV 2h-1, H2/oil 500/1 (V/V). HDS of FCC gasoline can reach 81%, olefin saturation ratio is only 9.9% at the condition of 320°C, 1.6MPa, LHSV 4h-1, H2/oil 300/1 (V/V), this shows that Ni2P/SiO2 catalyst has high selectivity for hydrodesulfurization of FCC gasoline.