Superacid and catalytic properties of sulfated zirconia

Journal Article · Fri Oct 01 00:00:00 EDT 1993 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1993.1304· OSTI ID:5224110

Chen, F R; Coudurier, G; Vedrine, J C ^[1]; Joly, J F ^[2]

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1. Institut de Recherches sur la Catalyse, Villeurbanne (France)
2. Institut Francais du Petrole, Rueil Malmaison (France)

Zirconium hydroxide was sulfated by aqueous H[sub 2]SO[sub 4] solutions of different normalities. The presence of sulfur was observed to slow down the decrease of the surface area and the tetragonal-to-monoclinic phase transformation of zirconia with increasing calcination temperature. Acidic properties were studied by the Hammett indicator technique. Charge transfer complex formation was studied by ESR using benzene as a probe to study strong ionizing properties of the samples, since benzene has a high ionizing potential value (9.24 eV). The observed ESR signal was assigned to biphenyl cation with hyperfine splittings equal to a[sub H] = 6.74, 3.37, and 0.52 G for 2, 4, and 4 protons, respectively. Its intensity was observed to be maximum for a calcination temperature equal to 600[degrees]C and a sulfur content equal to 1.5 to 3 wt%. This corresponds very probably to the maximum of strong Lewis acidity. Catalytic properties were studied for the isomerization of n-butane to i-butane in the 150 to 300[degrees]C range. The highest catalytic activity in flow reactor was observed for the samples calcined at 600[degrees]C as for benzene ionization properties, which indicates a close correlation. Hydrogen was observed to sharply decrease the deactivation rate suggesting that the active sites do not correspond to sulfur-reduced species and that Bronsted acid sites are probably necessary for the reaction. It is proposed that both strong Lewis and Bronsted sites are involved for n-butane isomerization. Zr[sup 3+] cations were also observed by ESR for sulfated zirconia samples outgassed above 600[degrees]C with maximum intensity between 650 and 750[degrees]C. It is proposed that they arise from the reduction of Zr[sup 4+] cations by SO[sub 4][sup 2[minus]] decomposition into SO[sub 2] and O[sub 2]. The presence of such Zr[sup 3+] species was not related to catalytic properties. 28 refs., 14 figs., 2 tabs.

• OSTI ID: 5224110
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 143:2; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020400 -- Petroleum-- Processing
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKANES
BROENSTED ACIDS
BUTANE
CATALYSIS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
ELECTRON SPIN RESONANCE
HETEROGENEOUS CATALYSIS
HYDROCARBONS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
ISOMERIZATION
LEWIS ACIDS
MAGNETIC RESONANCE
MONOCLINIC LATTICES
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RESONANCE
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
TETRAGONAL LATTICES
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES