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Dynamics of redox behavior of nano-sized VOx species over Ti–Si-MCM-41 from time-resolved in situ UV/Vis analysis

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Abstract.
Time-resolved in situ UV/Vis spectroscopy has been successfully applied for analyzing the reduction
degree of highly dispersed VOx (0.4–1.1 V/nm2) species over Ti–Si-MCM-41 (Ti/Si = 0–1.5) materials in
the oxidative dehydrogenation of propane (ODP) as well as for deriving the kinetic parameters of reduction
(with C3H8) and reoxidation (with O2 and N2O) of these species. This quantitative kinetic study
enabled to recognize at least two types of differently reducible VOx species in the samples with titanium.
Three effects of titanium on redox properties of VOx species were identified: (i) the constant of reduction
of oxidized VOx species by C3H8 increases, (ii) the constant of oxidation of reduced VOx species by O2
decreases; and (iii) the constant of oxidation of reduced VOx species by N2O increases. These effects
are highly relevant for the ODP performance. The intrinsic ODP activity increases linearly with an
increase in the constant of reduction of oxidized VOx species. Propene selectivity is determined by the
ratio of the constants of reduction and reoxidation of VOx species; the higher the ratio, the higher the
selectivity. This ratio can be tuned by the oxidizing agent (O2 vs. N2O) and by the Ti/Si ratio.

Keywords:
In situ UV/Vis
Vanadia
Silica
Titanium
Propane
Propene
ODP
N2O
Reaction mechanism

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Informasi Detail

Judul Seri

Journal of Catalysis

No. Panggil

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Penerbit

London : Elsevier Inc.., 2009

Deskripsi Fisik

Journal of Catalysis 265 (2009) 8–18

Bahasa

English

ISBN/ISSN

00219517

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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