SSRG International Journal of Applied Chemistry ( SSRG – IJAC ) – Volume 3 Issue 2 May to Aug 2016 ISSN: 2393 - 9133 www.internationaljournalssrg.org Page 1 Ni nanoparticles dispersed on γ-Al 2 O 3 by induced-gelation sol-gel method M. Mónica Guraya #1 , Soledad Perez Catán *2 , Miguel D. Sánchez ## , and Sergio Moreno ** # Complejo Tecnológico Pilcaniyeu, CNEA, Bustillo 9500, 8400- S.C.de Bariloche, Argentina. Universidad Tecnológica Nacional, Facultad Regional Buenos Aires-Extensión Áulica Bariloche, Argentina. * Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, CNEA, Bustillo 9500, 8400- S.C.de Bariloche, Argentina. ## Departamento de Física, Universidad Nacional del Sur y Planta Piloto de Ingeniería Química (UNS- CONICET), Avda Alem 1253, 8000-Bahía Blanca, Argentina. ** Centro Atómico Bariloche, CONICET, Bustillo 9500, 8400- S.C.de Bariloche, Argentina. Abstract – A series of Ni/γ-Al 2 O 3 samples were prepared by the sol-gel method using a solution of nickel nitrate as gelation agent. The Ni content of the samples was in the range 7-39 wt%. High specific BET areas, from 150 to 200 m 2 /g, were determined in samples after 4 h calcination at 600 ºC. As the metal was incorporated into the alumina during formation of the porous structure, high metal-support interaction and nickel dispersion were expected. To investigate the extent of these effects, reducing treatments were carried out and monitored by Thermogravimetry (TG), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and X-ray Diffractrometry (XRD). All XRD spectra from calcined samples showed patterns corresponding to NiO and spinel- like NiAl 2 O 4 structures. Reducing treatments at 400ºC were performed in a TG set up, in 10% H 2 /Ar flow, until no mass change was detected. XRD spectra recorded afterwards showed Niº diffraction peaks corresponding to 20nm metal particles but also NiO and NiAl 2 O 4 patterns consistent with smaller particles of 4-7 nm in size. Subsequent treatments at 700ºC also in H 2 /Ar flow allowed accomplishing the metal reduction. XRD spectra indicated that reduction was complete in all samples after 30 min plateau. This time proved short enough to avoid introducing much distortion in the alumina matrix as confirmed by BET area. All samples showed particles of 20-30 nm in size under TEM, indicating that this method allows the obtention of high dispersed Ni particles even for very high Ni contents. Keywords: Ni/gamma-alumina, NiAl2O4 spinel, high dispersion Ni I. INTRODUCTION Ni catalysts supported on mesoporous alumina have been widely investigated for decades due to their applicability in many industrial processes involving hydrocarbons decomposition [1]-[4]. In the last years this one and other active materials have been proposed for membranes coatings to be used in both catalytic membrane reactors and hydrogen separation [5]-[10]. Regardless the specific application involved, a general requirement of high and stable metal dispersion is demanded. This property is associated to formation of very small metal particles, which are resistant to sintering and carbon deposition in case of reforming and oxidation reactions [11]-[14]. High specific support area is also necessary when designing a catalyst or membrane coatings; for this purpose -Al 2 O 3 is particularly suitable for moderate operation temperatures [15]-[17]. Kim et al. have studied the influence of strong metal support interaction (SMSI) [12] on the final Ni particle size, i.e. after calcination and subsequent reduction to obtain Ni 0 . Murata et al. [18] have reported that Ni/Al 2 O 3 catalysts were more active and stable than the corresponding supported on Si 2 O. The general agreement among authors is that nickel aluminate species produced by SMSI give nickel nanoparticles, i.e. high metal dispersion [19], [20]. Sample preparation by impregnation methods proved efficient in obtaining Ni/-Al 2 O 3 materials, although high metal dispersion can only be achieved with low Ni contents. Xu et al. [21] demonstrated that high metal loadings in impregnated samples led to large metal particles and, therefore, to low metal dispersion. Sol-gel methods however, are more suitable for producing small nickel particles as many studies have established [22]. A disadvantage observed in Ni/-Al 2 O 3 materials, where SMSI mostly generates NiAl 2 O 4 – like species, is that reduction temperature becomes high, thus resulting undesirable matrix distortion the porous alumina support, which reduces its specific area [23]. In this work we prepared a series of Ni/- Al 2 O 3 samples via sol-gel, where peptising was modified in order to favor the dispersion of Ni ions in