Over a superacid ZrO2/SO4 system (ZS8: microcrystalline tetragonal, SO4 content ≈ 2.6 groups per nm2), the isomerization of n-butane proceeds rapidly and with high yield of i-butane at 423 K, if the catalyst is calcined in dry air at ≈ 823 K. The active catalyst typically shows: all surface sulfates in a highly covalent form, a high concentration of strong (aprotic) Lewis acid sites, and a fairly low (though never null) concentration of (protonic) Brønsted acid sites. A partial rehydration of the catalyst gradually converts the surface sulfates first into a less covalent form and then into an ionic form, decreases the concentration of strong Lewis sites, and increases (up to a factor of ≈ 10) the concentration of Brønsted sites, while the catalytic activity is gradually extinguished. Initial activity and initial surface features can be recovered by repeating the catalyst activation step. © 1994 Academic Press, Inc.

On the acid-catalyzed isomerization of light paraffins over a ZrO2/SO4 System: The effect of hydration

PINNA, Francesco;SIGNORETTO, Michela;STRUKUL, Giorgio
1994-01-01

Abstract

Over a superacid ZrO2/SO4 system (ZS8: microcrystalline tetragonal, SO4 content ≈ 2.6 groups per nm2), the isomerization of n-butane proceeds rapidly and with high yield of i-butane at 423 K, if the catalyst is calcined in dry air at ≈ 823 K. The active catalyst typically shows: all surface sulfates in a highly covalent form, a high concentration of strong (aprotic) Lewis acid sites, and a fairly low (though never null) concentration of (protonic) Brønsted acid sites. A partial rehydration of the catalyst gradually converts the surface sulfates first into a less covalent form and then into an ionic form, decreases the concentration of strong Lewis sites, and increases (up to a factor of ≈ 10) the concentration of Brønsted sites, while the catalytic activity is gradually extinguished. Initial activity and initial surface features can be recovered by repeating the catalyst activation step. © 1994 Academic Press, Inc.
1994
149
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10278/21266
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