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Reoxidation dynamics of highly dispersed VOx species supported on y-alumina

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Abstract
The VOx/y-Al2O3 catalyst VA-200, which was introduced in a previous article, is further characterized by
XPS and visible Raman spectroscopy. The reoxidation of highly dispersed VOx species with gas phase
oxygen is investigated in detail and is described by an empirical kinetic model. It is observed that the
reoxidation of reduced VOx/y-Al2O3 catalyst is strongly affected by the presence of water. The proposed
kinetic model includes a distinct coverage of VOx species with water or hydroxyl groups in the
investigated temperature range of 479–712 K. Hydrated surface species are oxidized under release of
water. Best fits of the experimental data can be achieved with first order rate laws with respect to oxygen
concentration. Experiments are performed in an ideally mixed Berty-type reactor using oxygen stepmarking
over the reduced catalyst. The evolution of oxygen concentration using the kinetic model is in
agreement with the experimentally observed behaviour. The signal of water released during the reaction
can be modeled only qualitatively, which (presumably) stems from its sorption behaviour on the acidic
alumina support. The oxidation of VOx species furthermore depends on the reaction temperature. The
oxidation of V+III to V+V cannot be completely achieved at temperatures below 673 K. However, the
activation energy of this reaction is low, as suggested by the absence of strong variations of the response
shapes with respect to temperature.

Keywords: VOx/y-Al2O3, Vanadia, Oxidation, Kinetics, Mars–van Krevelen, Water

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Informasi Detail

Judul Seri

Applied Catalysis A: General

No. Panggil

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Penerbit

London : Elsevier B.V.., 2009

Deskripsi Fisik

Applied Catalysis A: General 353 (2009) 288–295

Bahasa

English

ISBN/ISSN

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

KIMIA

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

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