Activation and isomerization of n-butane on sulfated zirconia model systems—an integrated study across the materials and pressure gaps

C. Breitkopf; H. Papp; X. Li; R. Olindo; J. A. Lercher; R. Lloyd; S. Wrabetz; F. C. Jentoft; K. Meinel; S. Förster; K.-M. Schindler; H. Neddermeyer; W. Widdra; A. Hofmann; J. Sauer

doi:10.1039/B701854A

Activation and isomerization of n-butane on sulfated zirconia model systems—an integrated study across the materials and pressure gaps†

C. Breitkopf,^a H. Papp,^a X. Li,^b R. Olindo,^b J. A. Lercher,^b R. Lloyd,^c S. Wrabetz,^c F. C. Jentoft,^c K. Meinel,^d S. Förster,^d K.-M. Schindler,^d H. Neddermeyer,^d W. Widdra,^d A. Hofmann^e and J. Sauer^e

Author affiliations

^a Universität Leipzig, Institut für Technische Chemie, Linnéstraße 3, Leipzig, Germany

^b Technische Universität München, Lehrstuhl für Technische Chemie II, Lichtenbergstraße 4, Garching, Germany

^c Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, Berlin, Germany

^d Martin-Luther-University Halle-Wittenberg, Institute of Physics, Hoher Weg 8, Halle, Germany

^e Institut für Chemie, Humboldt-Universität zu Berlin, Unter den Linden 6, Berlin, Germany

Abstract

Butane activation has been studied using three types of sulfated zirconia materials, single crystalline epitaxial films, nanocrystalline films, and powders. A surface phase diagram of zirconia in interaction with SO₃ and water was established by DFT calculations, which was verified by LEED investigations on single-crystalline films and by IR spectroscopy on powders. At high sulfate surface densities a pyrosulfate species is the prevailing structure in the dehydrated state; if such species are absent, the materials are inactive. Theory and experiment show that the pyrosulfate can react with butane to give butene, H₂O and SO₂, hence butane can be activated via oxidative dehydrogenation. This reaction occurred on all investigated materials; however, isomerization could only be proven for powders. Transient and equilibrium adsorption measurements in a wide pressure and temperature range (isobars measured via UPS on nanocrystalline films, microcalorimetry and temporal analysis of products measurements on powders) show weak and reversible interaction of butane with a majority of sites but reactive interaction with <5 μmol g⁻¹ sites. Consistently, the catalysts could be poisoned by adding sodium to the surface in a ratio S/Na = 35. Future research will have to clarify what distinguishes these few sites.

Physical Chemistry Chemical Physics

Activation and isomerization of n-butane on sulfated zirconia model systems—an integrated study across the materials and pressure gaps†

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Activation and isomerization of n-butane on sulfated zirconia model systems—an integrated study across the materials and pressure gaps

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