Comparative study of the texture and structure of aerogel and xerogel sulphated zirconia doped with nickel

Abstract

Aerogels and xerogels based on sulphated zirconia doped with nickel in the same atomic ratios S/Zr = 0.5 and Ni/Zr = 0.1 have been synthesized by solgel method using two drying ways of the solvent in solid preparation steps. Aerogels obtained by drying in supercritical conditions of solvent stabilize zirconia tetragonal phase even at high calcination temperatures and present a developed surface area, whereas xerogels obtained by ordinary solvent drying in an oven are amorphous. TPR and XPS studies revealed that Ni seems to exist in different species in the two kinds of solids and it is more reducible in aerogels.

Effect of drying conditions on the textural, structural and catalytic properties of Cr/ZrO2–SO4: n-hexane conversion

“…Furthermore, it is important to emphasize the key role played by chromium for the stabilization of this phase in agreement with previous study on chromium supported [17]. Chromium, in opposition to other metals such as nickel [12], can be anchored into the sulfated zirconia lattice which preserves the crystallite growth and consequently stabilizes a pure ZrO 2 tetragonal phase for a large domain of temperatures.…”

“…The results revealed that this catalytic system is very performing [6][7][8][9]. Thanks to their hydrogenatingdehydrogenating and redox properties, transition metals can constitute an interesting alternative to the expensive platinum [10][11][12]. Good control of the preparation conditions is decisive.…”

“…The sol-gel method is one of the methods well-known for the homogeneity that it offers to solids. When it is associated to super critical drying, the sol-gel procedure favors the development of surface area thanks to development of a nanocrystalline particles [12,13].…”

Effect of the doping agent nature on the characteristic and catalytic properties of aerogel zirconia catalysts doped with sulfate groups or heteropolytungstic acid

“…The n-hexane isomerization into different branched isomers, e.g., 2,2-dimethylbutane (2,2-DMB), 2,3-dimethylbutane (2,3-DMB) and 2-methylpentane (2-MP) has been extensively investigated in the Laboratory of Materials Chemistry and Catalysis (Laboratoire de Chimie des Matériaux et Catalyse (LCMC)). Catalysts involved are acidic ones, e.g., zirconia doped with sulfate groups and transition metals such as nickel, cerium and chromium [4][5][6][7][8][9]. Such catalysts have been prepared by sol-gel method and dried either in supercritical condition of solvents or in ordinary condition [4][5][6][7][8][9] since sol-gel route offers a better control of the homogeneity of the prepared solids as regards to other methods [10][11][12].…”

“…Catalysts involved are acidic ones, e.g., zirconia doped with sulfate groups and transition metals such as nickel, cerium and chromium [4][5][6][7][8][9]. Such catalysts have been prepared by sol-gel method and dried either in supercritical condition of solvents or in ordinary condition [4][5][6][7][8][9] since sol-gel route offers a better control of the homogeneity of the prepared solids as regards to other methods [10][11][12]. For zirconia based catalysts, the sol-gel method offered the opportunity to introduce in one step zirconium alkoxide, metal precursor and sulfate groups as dopant in order to assure the homogeneity and to control morphological and textural properties of the final materials [13,14].The obtained results showed that aerogels manifest developed textural properties as well as higher acidity.…”