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          Institute: Fritz-Haber-Institut     Collection: Inorganic Chemistry     Display Documents

ID: 9778.0, Fritz-Haber-Institut / Inorganic Chemistry
Isomerization of n-Butane and of n-Pentane in the Presence of Sulfated Zirconia: Formation of Surface Deposits Investigated by In Situ UV-vis Diffuse Reflectance Spectroscopy
Authors:Ahmad, Rafat; Melsheimer, Jörg; Jentoft, Friederike C.; Schlögl, Robert
Research Context:Project 1, Acid-base & redox properties of promoted sulfated zirconia
Date of Publication (YYYY-MM-DD):2003
Title of Journal:Journal of Catalysis
Start Page:365
End Page:374
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:Catalytic performance and formation of carbonaceous deposits were studied simultaneously during alkane isomerization over sulfated zirconia in a fixed bed flow reactor with an optical window for in situ UV-vis diffuse reflectance spectroscopy. The reactions of n-butane (5 kPa) at 358 and 378 K and of n-pentane (0.25 kPa) at 298 and 308 K passed within 5 h or less through an induction period, a conversion maximum, and a period of deactivation; a steady activity of 64 and 77 µmol g-1 h-1 (isobutane formation) and 3 µmol g-1 h-1 (isopentane, both temperatures) remained. UV-vis spectra indicate the formation of unsaturated surface deposits; the band positions at 310 nm (n-butane reaction) and 330 nm (n-pentane) are within the range of monoenic allylic cations. More highly conjugated allylic cations (bands at 370 and 430 nm) became evident during n-butane reaction at 523 K. The chronology of events suggests that the surface deposits are (i) a result only of the bimolecular and not the monomolecular reaction mechanism, and (ii) are formed in a competitive reaction to the alkane product
Free Keywords:n-butane, n-pentane, isomerization, sulfated zirconia, deactivation, in situ UV-vis spectroscopy
Last Change of the Resource (YYYY-MM-DD):2003-02-14
External Publication Status:published
Document Type:Article
Communicated by:Robert Schlögl
Affiliations:Fritz-Haber-Institut/Inorganic Chemistry/Functional Characterization
Fritz-Haber-Institut/Inorganic Chemistry/Inorganic Chemistry
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