(570v) Structure of Flame-Made Vanadia/Silica and Catalytic Behavior in the Oxidative Dehydrogenation of Propane | AIChE

(570v) Structure of Flame-Made Vanadia/Silica and Catalytic Behavior in the Oxidative Dehydrogenation of Propane

Authors 

Jiang, Y. - Presenter, ETH Zürich
Pratsinis, S. E. - Presenter, Swiss Federal Institute of Technology, Particle Technology Laboratory, ETH Zurich
Baiker, A. - Presenter, ETH Zürich


Catalyst based on supported vanadia showed
promising results for the ODH reaction. Here vanadia/silica particles with a specific
surface area up to 330 m2g-1 and a V2O5
content up to 50 wt.% or V surface density up to 27.6 V nm-2
were prepared by flame-spray-pyrolysis. Selected samples were tested for the
ODH of propane. The as-prepared flame-made catalysts showed dominantly isolated
monomeric VOx surface species for V-loadings exceeding even the
typical ?monolayer coverage? (2 V nm-2) of classic
wet-impregnated materials as confirmed by Raman and NMR analysis. The turnoverfrequency
of flame-made catalysts decreased with increasing vanadia loading while the
presence of small V2O5 crystallites seemed to be less critical.
The conversion (global activity), however, showed a maximum for the 20 wt.%
V2O5/SiO2 (4.6 V nm-2)
catalyst. Catalysts consisting dominantly of isolated monomeric VOx-species
exhibited higher selectivity to propylene than those where crystalline V2O5
prevailed. Nevertheless, the highest propylene yield was measured for catalysts
with high V surface density containing both monomeric VOx and
crystalline V2O5. Flame-spray-pyrolysis proved to be a
very versatile method for synthesis of V2O5/SiO2
catalysts with high dispersion and well defined structure of the active sites.

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