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The effect of Nb or Ta substitution into the M1 phase of the MoV(Nb,Ta)TeO selective oxidation catalyst

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Abstract.
We use aberration corrected high-angle annular dark field (HAADF) imaging to systematically study,
atomic column by atomic column, the effects of substituting Nb or Ta into the M1 phase of the
MoV(Nb,Ta)TeO propane (amm)oxidation catalyst. The HAADF results indicate that the x,y coordinates of
themetal sites within the M1 framework are unaffected by the substitution of either Nb or Ta for Mo. The
HAADF analysis of the Ta-substituted catalyst demonstrated that the Ta preferentially substitutes into
the pentagonal bipyramidal site, and by analogy, we anticipate that Nb substitutes similarly.
Compositional analysis of the entire framework suggests that Ta/Nb behaves as a director of V among
the octahedra that link the pentagonal rings, and the variable V occupancy may be correlated with
variations in catalytic activities and selectivities. Finally, HAADF imaging provided evidence of
coexistence of Ta-rich and Ta-poor domains. Similar phase segregation behavior may be present in Nbsubstituted specimens, but would be very difficult to detect.

Keywords:
Aberration-corrected STEM
HAADF
M1/M2
MoVTeNbO
MoVTaTeO
Propane oxidation

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Informasi Detail

Judul Seri

Catalysis Today

No. Panggil

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Penerbit

London : Elsevier B.V.., 2009

Deskripsi Fisik

Catalysis Today 142 (2009) 320–328

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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