Promotion of Re/Al2O3 and Re/C catalysts by Ni sulfide in the HDS and HDN of gas oil:Effects of Ni loading and support

摘要

Two series of NiRe catalysts supported on gamma-Al2O3 and activated carbon having constant wt.% Re2O3 content(3.51 and 1.97,respectively)and various Ni/Re atomic ratios were prepared to investigate the promoting action of Ni on sulfided Re catalysts in the simultaneous hydro-desulfurization(HDS)and hydrodenitrogenation(HDN)of gas oil.The catalysts were characterized using textural analysis,X-ray diffraction,diffuse reflectance spectroscopy,energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy.On both Ni(x)Re/Al2O3 and Ni(x)Re/C catalysts,the dependence of HDS and HDN activities showed initially an increase and subsequent decrease with increasing Ni content,with optimum Ni/Re atomic ratios of ~0.94 for Ni(x)Re/Al2O3 catalysts and ~1.25 for Ni(x)Re/C catalysts.The decline in activity was attributed to a reduction in Re dispersion and a low Ni sulfidation for the alumina-supported catalysts,and to a separate location of Re and Ni on the support surface,as well as to an incomplete Ni sulfidation for the carbon-supported catalysts.The synergetic effect in activity observed between Ni and Re was slightly higher for HDS than for HDN,especially at low reaction temperature(325 °C)and on carbon-supported catalysts.On the basis of these promotional effects on catalytic activities and HDN/HDS selectivity,and the characterization results,the nature of the promotion observed on NiRe supported catalysts was discussed.