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A combined HAADF STEM and density functional theory study of tantalum and niobium locations in the Mo–V–Te–Ta(Nb)–O M1 phases

Paper ID Volume ID Publish Year Pages File Format Full-Text
49837 46769 2012 5 PDF Available
Title
A combined HAADF STEM and density functional theory study of tantalum and niobium locations in the Mo–V–Te–Ta(Nb)–O M1 phases
Abstract

The M1 phases of the Mo–V–Te–Nb mixed-metal oxides are highly promising catalysts for direct propane (amm)oxidation. Nb is beneficial to the activity and selectivity for acrylonitrile, but direct evidence for Nb location is lacking because structural methods cannot distinguish Nb (Z = 41) from Mo (Z = 42). We have employed high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) and density functional theory (DFT) to study the Ta (Z = 73) location in a Mo–V–Te–Ta–O M1 phase produced via hydrothermal synthesis, which possesses uniform Ta distribution compared to M1 phases previously synthesized via slurry evaporation. The HAADF STEM and DFT results indicate that Ta predominantly occupies the pentagonal bipyramidal site (S9). Moreover DFT results validate the previous hypothesis that Ta and Nb both prefer the S9 site.

Graphical abstractThe Ta location in the Mo–V–Te–Ta–O M1 phase was investigated by HAADF STEM and DFT calculations, which strongly indicated its location in the pentagonal bipyramidal site S9. The Nb location in the Mo–V–Te–Nb–O M1 phase was probed by the same theoretical methods, which supported the earlier hypothesis that Nb preferred the same pentagonal bipyramidal site S9.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Mo–V–Te–Ta–O M1 phase with uniform Ta distribution was synthesized hydrothermally. ► Ta was predominantly located in site 9 by HAADF STEM and DFT calculations. ► DFT calculations showed that Nb is predominantly located in site 9.

Keywords
Ta-M1, Mo–V–Te–Ta–O M1 phases; Nb-M1, Mo–V–Te–Nb–O M1 phases; SE, slurry evaporation; HT, hydrothermal synthesis; DM, Digital MicrographHeterogeneous catalysis; Propane (amm)oxidation; Mixed metal oxides; Mo–V–Te–Ta(Nb)–O M1 phase; DFT; HAADF STEM
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A combined HAADF STEM and density functional theory study of tantalum and niobium locations in the Mo–V–Te–Ta(Nb)–O M1 phases
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Communications - Volume 29, 5 December 2012, Pages 68–72
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us