Effect of fluorine addition on the formation of active species and hydrotreating activity of NiWS/Al2O3 catalysts

被引:33
作者
Song, CJ [1 ]
Kwak, C [1 ]
Moon, SH [1 ]
机构
[1] Seoul Natl Univ, Sch Chem Engn, Inst Chem Proc, Kwanak Ku, Seoul 151744, South Korea
关键词
hydrodesulfurization; fluorine; nickel-tungsten;
D O I
10.1016/S0920-5861(02)00022-6
中图分类号
O69 [应用化学];
学科分类号
081704 ;
摘要
Fluorine-added Ni/Al2O3, W/Al2O3 and NiW/Al2O3 catalysts were prepared and their surface properties investigated using temperature-programmed reduction, diffuse reflectance spectroscopy and temperature-programmed sulfidation. The hydrodesulfurization (HDS) of thiophene was used as a model reaction to examine the activity of fluorinated NiW/Al2O3. Fluorination led to an increase in the formation of polymeric tungstates in W/Al2O3 and the surface nickel spinel species in the case of Ni/Al2O3. Fluorination promoted the sulfidation of the NiW/Al2O3 catalyst and the interaction of nickel with tungsten to produce the Ni-W-O species, a precursor of active catalytic sites. The activity of NiW/Al2O3 was increased by fluorination up to a fluorine content of 4 wt.%, and then decreased at higher fluorine contents. Two opposite effects of fluorination determine the characteristic changes in the activity of NiW/Al2O3: the enhanced sulfidation of the catalyst and incorporation of nickel with tungsten, both of which promote the activity, and a decrease in the dispersion of active species, which lowers the activity. The activity results obtained in this study are different from those reported previously [Appl. Catal. A 144 (1996) 343], suggesting that the extent of catalyst modification by fluorination is strongly dependent on the conditions of catalyst preparation. (C) 2002 Elsevier Science B.V. All rights reserved.
引用
收藏
页码:193 / 200
页数:8
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