The Active Phase Construction Of NiMoS Supported Catalysts And Study Of Catalytic Performance

The research had been done to investigate the effect of impregnation order and carrier types on active phase and catalystic performance of sulfided NiMo catalysts. The catalysts of IMo IINiS(impregnating Ni after impregnating Mo), INiIIMoS(impregnating Mo after impregnating Ni) and NiMoS(impregnating Ni and Mo together) were prepared with precursors of ammonium tetrathionate(ATTM) and nickel nitrate,based on four carriers of Al2O3、SiO2、active carbon and SBA-15 respectively. Comprehensive characterizations including low temperature N2 adsorption-desorption、XRD、Py-IR、TPR、TEM and XPS were conducted on these catalysts, and the hydrodesulfurization reaction activity were evaluated with dibenzothiophene(DBT) as model compounds. Experimental results showed that INiIIMoS catalysts had the highest activity for all kinds of carriers, then followed by the NiMoS and IMoIINiS catalysts.The content of-SH group(Bronsted acid sites) and CUS(Lewis acid sites) on the surface of different sulfided NiMo catalysts were different. The CUS content was close to zero on all these atalysts, so the hydrogenation(HYD) activity was really weak; while-SH group content was high, especially INiIIMoS catalyst had the highest-SH group, therefore its hydrogenolysis(DDS) activity was supreme. Meanwhile, the 12% low load active component had excellent dispersibility on sulfided NiMo catalyst surface. The stacked MoS2 particles were mostly 2-3 layers short stacking and the chip length were shorter. The INi IIMoS catalyst had maximum number of MoS2 cluster layers and the length were shortest, accordingly it showed the highest HDS activity.The reason why impregnating Mo after impregnating Ni was the best order was that Ni could partially cover the carrier surface so that it could further weaken the interaction between Mo components and carrier. This could help MoS2 form a more perfect crystalline and disperse more uniformly on the surface, then Ni could implant well on MoS2 to form more type II Ni-Mo-S phase, therefore INi IIMoS catalysts had the highest activity. For the AC carrier, its good hydrophobic surface was superior to disperse Ni better than Mo, so that firstly impregnating Ni could distribute more evenly in the surface of the activated carbon carrier, and then the Mo components could impregnate better on the basis of Ni uniform dispersion.