Ni/CeO2 catalysts prepared by aqueous hydrazine reduction

摘要

In this study 1-5%Ni catalysts supported on commercial CeO2 were prepared by the chemical reduction in aqueous hydrazine. They were characterized by H-2-TPR, H-2-adsorption, H-2-TPD, XRD, TEM, STEM, EDS and X-mapping techniques. We obtained chestnut bur-like nickel morphology not reported in the literature for Ni/CeO2 catalysts. These structures consisted in a central ball of 0.3 mu m composed of smaller crystallites with mean size of 20-40 nm and surrounded by needles of 0.1-0.3 mu m. Small spherical particles (<= 2 nm) were also observed. Nickel was found in a highly reduced state and, in contrast to SiO2, the ceria support highly preserves the nickel from partial oxidation in air atmosphere. Noticeably, reduction of ceria by hydrazine occurred in the aqueous media at 353 K whereas it starts only at 640 K in gaseous hydrogen atmosphere. (C) 2007 Elsevier B.V. All rights reserved.