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Abstract

Zirconia modified with sulfate is a potential catalyst for the isomerization of n-butane to i-butane. The number of adsorption sites for small alkanes and the respective differential heats of adsorption on zirconia samples are thus of interest. In order to study the adsorption of propane, n-butane, and i-butane on a series of zirconia catalysts including partially deactivated samples, SETARAM MS-70 calorimeters were coupled with a volumetric system. At 313 K and an equilibrium pressure of 5 mbar, typically 10 to 100 µmol alkane per g catalyst were adsorbed. The majority of the sites on the materials were similar, with heats of adsorption between 40-60 kJ mol-1, only a small number of sites at coverages < 2 µmol g-1 was different. A number of interesting phenomena occurred: 1. For particularly active catalysts, the heats of adsorption of i-butane and n-butane increased with increasing coverage. 2. The adsorption was occasionally followed by secondary reactions. 3. After hours of constant pressure, a spontaneous, but slow uptake of sorptive with considerable heat evolution was observed.

Methods: BET, GC, Microcalorimetry
Elements: Fe, O, S, Zr