Effect of NiO content on structural, surface and catalytic characteristics of nano-crystalline NiO/CeO2 system

The NiO/CeO2 nano-composite catalysts containing different nickel content prepared by impregnation method have been characterized by X R D and TEM. The surface and catalytic properties of Ni/Ce mixed oxide solids were determined by nitrogen adsorption at -196 degrees C and catalytic conversion of isopropanol at different temperatures. These composites can be described as a mixture of nickel oxide and ceria modified by the insertion of a part of nickel in the ceria lattice. The size of the nickel oxide varies considerably from clusters to a crystallized material, depending on the amount of nickel oxide. From the characterization of the composites, it was concluded: at low Ni loading, the ceria surface is gradually covered with the dispersed NiO species. At higher loading, highly dispersed NiO, well crystalline nickel oxide and Ni-Ce-O solid solution coexist. It was verified that the structural, morphological, surface and catalytic properties could be influenced by nickel loading. This treatment led to a slightly increase in the crystallite size of ceria particles. On the other hand, the augmentation in the nickel content brought about an increase in the crystallite size, lattice constant and unit cell volume of nickel oxide. The nickel loading brought about an increase in the formation of Ni-Ce-O solid solution with subsequent creation of oxygen vacancies. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.