ORIGINAL PAPER Comparative study of aerogels nanostructured catalysts: Ni/ZrO 2 –SO 4 2- and Ni/ZrO 2 –Al 2 O 3 –SO 4 2- N. Kamoun & M. K. Younes & A. Ghorbel & A. S. Mamede & A. Rives Received: 18 February 2014 /Revised: 23 May 2014 /Accepted: 23 May 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract A series of Ni/ZrO 2 –SO 4 2- and Ni/ZrO 2 –Al 2 O 3 – SO 4 2- catalysts were prepared in one step by the sol–gel method and dried in hypercritical conditions of the solvent. The characteristic properties of those solids were investigated using many techniques: the XRD, the physisorption of N 2 , the IR, the UV–visible, and the X-ray photoelectron spectroscopy (XPS). Textural analysis reveals the mesoporosity of all the aerogel catalysts. Moreover, the addition of alumina to nickel sulfated zirconia at high calcination temperature increased twice the specific surface area, from 72 to 158 m 2 /g. XRD patterns show that nickel-promoted sulfated zirconia calcined at different temperature develops the tetragonal and the mono- clinic ZrO 2 phase, whereas the nickel sulfated zirconia alumi- na exhibits only the ZrO 2 tetragonal phase. The addition of aluminum to nickel sulfated zirconia induces significant changes in symmetry of nickel by the migration of Ni ions from octahedral to tetrahedral coordination. XPS spectrosco- py shows that the nickel in Ni/ZrO 2 –SO 4 2- catalysts is more reducible than those in Ni/ZrO 2 –Al 2 O 3 –SO 4 2- . Nickel sulfat- ed zirconia catalyst exhibits higher activity than nickel sulfat- ed zirconia alumina, in the n-hexane isomerization reaction. Keywords Isomerization . Aluminum . Sol–gel route . Aerogel . Sulfated zirconia . Nickel Introduction In the current petrochemical industry, skeletal isomerization of alkanes catalyzed by a solid acid is an important process for the production of clean fuels of high octane number. Among various acidic solids, sulfated zirconia is an attractive isomer- ization catalyst due to its super-acidity, thermal stability, and excellent activity for skeletal isomerization of short alkanes at low temperatures [1, 2]. It is well known that the catalytic properties of sulfated zirconia are highly influenced by the preparation method [3]. Sol–gel method seems to be an at- tractive route for the preparation of these oxides. The resulting materials exhibit a large surface area and high porosity. Previous works in our laboratory [4] have revealed the benefit effect of the simultaneous use of sol–gel method and hyper- critical solvent evacuation’ s conditions on catalytic perfor- mance and textural properties of sulfated zirconia. However, despite its high activity, the stability of sulfated zirconia is rather limited [5]. It prevented its use in commercial processes. To improve the lifetime of sulfated zirconia in catalysis, various transition metals such as nickel [6], chromi- um [7] iron, or manganese [8, 9] have been found to stabilize the catalytic activity of sulfated zirconia. Another method to improve the catalytic properties of sulfated zirconia is mixing this catalyst with a small proportion of different oxides as alumina, titania, gallium, and iron oxides [10–15]. Gao et al. claim that the existence of small amounts of Al 2 O 3 into sulfated zirconia increases the catalytic activity and stability of n-butane isomerization performed at 250 °C in the presence of H 2 [10]. In this regard, the study of the combined effect of both Ni and Al on the stability and catalytic activity of sulfated N. Kamoun (*) : M. K. Younes : A. Ghorbel Laboratoire de Chimie des Matériaux et Catalyse, Département de Chimie, Faculté des Sciences de Tunis, Université Tunis El Manar, 2092 Tunis, Tunisia e-mail: nesrine_kam@yahoo.fr A. S. Mamede Unité de Catalyse et de Chimie du Solide UCCS, Université Lille Nord de France F-59000, CNRS UMR 8181, Ecole Nationale Supérieure de Chimie de Lille, 59652 Villeneuve d’Ascq, France A. Rives Unité de Catalyse et de Chimie du Solide UCCS, Université Lille Nord de France F-59000, CNRS UMR 8181, Université Lille1, 59655 Villeneuve d’Ascq, France Ionics DOI 10.1007/s11581-014-1168-2