On the structure and surface properties of NiO/MgO–La 2 O 3 catalyst: Influence of the support composition and preparation method Sergio L. Gonza ´lez-Corte ´s Æ Ismael Aray Æ Serbia M. A. Rodulfo-Baechler Æ Claudio A. Lugo Æ Hector L. Del Castillo Æ Alfonso Loaiza-Gil Æ Freddy E. Imbert Æ Humberto Figueroa Æ Wilfredo Pernı ´a Æ Alfonso Rodrı ´guez Æ Oduber Delgado Æ Rodrigo Casanova Æ Juan Mendialdua Æ Fulgencio Rueda Received: 28 October 2006 / Accepted: 25 January 2007 / Published online: 30 April 2007 Ó Springer Science+Business Media, LLC 2007 Abstract This work addresses the effect of catalyst preparation method and the carrier compositions (MgO– La 2 O 3 ) over the NiO-support interaction, which affect the reducibility, textural properties and the different oxygen species chemisorbed at different temperatures over MgO– La 2 O 3 supported NiO catalysts. The materials were prepared by wet sequential impregnation and wet co-impregnation with different Mg molar fractions [Mg/ (La+Mg)]. The samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), infrared (IR) spectroscopy, scanning electron microscopy (SEM), changes of surface potential and BET surface area measurements. The total oxidation of methane was use as model reaction. It has been found that the catalyst formulations (i.e. NiO/MgO–La 2 O 3 ) and the preparation methods not only affect the interaction among the catalyst components, but also the texture and material morphology as a result of different degrees of particle aggregation. The wet sequential impregnation-prepared catalysts showed a stronger MgO–La 2 O 3 interaction than wet co-impregnation-prepared samples. A marked tendency of NiO to react with MgO rather than La 2 O 3 following a mechanism of lattice substitution is observed. Mg-free catalyst showed LaNiO 3 and NiO as major crys- talline Ni-containing phases. The ternary Ni–Mg–La–O system, on the other hand, facilitates the formation of poorly reducible Ni phase, whereas the La-free catalyst (i.e. NiO/MgO) displayed the lowest content of Ni-reduc- ible phase, owing to the formation of Ni 1–x Mg x O solid solution. Measurements of surface potential changes together with catalytic studies suggest that La-containing catalysts present oxygen vacancies, which markedly affect the chemical nature of the surface oxygen species and hence their catalytic behaviour. Introduction The goal of catalytic material preparation is to design a probable commercial product, which could be used as an active, selective and stable catalyst for a determined cata- lytic process. In order to achieve this goal, the best pre- parative method must be able to produce a catalytic material with appropriate textural properties (i.e., suffi- ciently high surface area and uniform pore distribution) and suitable mechanical strength. Supported and unsupported (or bulk) catalysts are usually thought to have an uniform chemical composition, which might present a multiphase structure as a consequence of either doping, promoting, surface or bulk segregation or even the effect of the reac- tion environment on the catalyst. Schwarz and co-workers [1] divided the preparation routes of catalysts into two categories: Methods in which the active phase is generated S. L. Gonza ´lez-Corte ´s (&)  I. Aray  S. M. A. Rodulfo-Baechler  C. A. Lugo  H. L. Del Castillo  A. Loaiza-Gil  F. E. Imbert  H. Figueroa  W. Pernı ´a Laboratorio de Cine ´tica y Cata ´lisis, Departamento de Quı ´mica, Facultad de Ciencias, Universidad de Los Andes, La Hechicera, Merida 5101, Venezuela e-mail: goncor@ula.ve A. Rodrı ´guez  O. Delgado  R. Casanova  J. Mendialdua  F. Rueda Laboratorio de Fı ´sica de Superficies, Departamento de Fı ´sica, Facultad de Ciencias, Universidad de Los Andes, La Hechicera, Merida 5101, Venezuela 123 J Mater Sci (2007) 42:6532–6540 DOI 10.1007/s10853-007-1552-7