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Surface Characterization of W/Ni/Al2O3 Catalysts

Published online by Cambridge University Press:  10 February 2011

M. H. Jordão ,
J. M. Assaf  and
P. A. P. Nascente
M. H. Jordão
Affiliation:
Departamento de Engenharia Química, Universidade Federal de São Carlos, 13565–905 Sao Carlos, SP, Brazil, [email protected]
J. M. Assaf
Affiliation:
Departamento de Engenharia Química, Universidade Federal de São Carlos, 13565–905 Sao Carlos, SP, Brazil, [email protected]
P. A. P. Nascente
Affiliation:
Centro de Caracterização e Desenvolvimento de Materials, Departamento de Engenharia de Materials, Universidade Federai de São Carlos, 13565–905 Sao Carlos, SP, Brazil, [email protected]
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Abstract

Catalysts containing tungsten and nickel oxides are important in hydrodesulfurization (HDS), hydrogénation (HY), and steam reforming of hydrocarbons. A series of W/Ni/Al2O3 catalysts was prepared by two different methods: (1) coprecipitation of nickel and aluminium hydroxicarbonate from their nitrates, followed by calcination and impregnation of tungsten; (2) precipitation of boehmite from aluminium nitrate, followed by impregnations of nickel, firstly, and tungsten. The nickel content was kept constant, while the amount of tungsten varied from 2.5 to 15.5 wt-%. The resulting oxides were characterized by inductively coupled plasma spectroscopy (ICP), atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), temperature programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). ICP and AAS were used to determine the W, Ni, and Al concentrations. XRD detected two phases: NiO and NiAl2O4 (no phase containing metallic tungsten was detected). Increasing the amount of W, the quantity of NiAl2O4 rose, the quantity of NiO decreased, and the particle size of NiO enlarged. The TPR profiles presented three peaks: one at about 1000 °C, associated to a very stable phase; for the samples prepared by coprecipitation, the other two peaks corresponded to “free NiO” and a nonstoichiometric aluminate. For the samples prepared by impregnation, those peaks corresponded to NiO and NiAl2O4. XPS identified Al2O3, NiAl2O4, and Al2(WO4)3 for both preparation methods. Increasing the amount of tungsten in the impregnated samples, NiWO4 was also observed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 497: Symposium Z – Recent Advances in Catalytic Materials , 1997 , 243
Copyright
Copyright © Materials Research Society 1998

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References

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