Vanadium Pentoxide - a Compound with Five-Coordinated Vanadium Atoms.

Byström, Anders; Wilhelmi, Karl-Axel; Brotzen, Otto

doi:10.3891/acta.chem.scand.04-1119

Cited by 197 publications

(57 citation statements)

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“…Maxima that occur at similar distances indicate the presence of only one type of oxygen atom. 53 Crystalline V 2 O 5 has a distorted trigonal pyramidal structure and four distinct V-O distances (the V-O shell at 0.188 nm is doubly degenerate), 54 and the maxima do not coincide. The imaginary part and the magnitude of the radial scattering function are accurately described by incorporating all four V-O distances in the simulation (fitting parameters in Table 4).…”

Section: + Exchange Stoichiometry In H-zsm5mentioning

confidence: 99%

Synthesis, Structure, and Catalytic Reactivity of Isolated V⁵⁺-Oxo Species Prepared by Sublimation of VOCl₃ onto H-ZSM5

Lacheen

Iglesia

2006

J. Phys. Chem. B

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Isolated and uniform V 5+ -oxo species were grafted onto H-ZSM5 at V/Al f ratios of 0.2-1 via sublimation of VOCl 3 precursors. These methods avoid the restricted diffusion of solvated oligomers in aqueous exchange, which leads to poorly dispersed V 2 O 5 at external zeolite surfaces. Sublimation methods led to stable and active V-ZSM5 catalysts for oxidative dehydrogenation (ODH) reactions; they led to an order of magnitude increase in primary C 2 H 6 ODH rates compared with impregnated ZSM5 catalysts at similar V/Al f ratios and showed similar activity to impregnated VO x /Al 2 O 3 . The structure of grafted V 5+ -oxo species was probed using spectroscopic and titration methods. Infrared spectra in the OH region and isotopic exchange of D 2 with residual OH groups showed that exposure to VOCl 3(g) at 473 K led to stoichiometric replacement of H + by each (VOCl 2 ) + species. Raman spectra supported by Density Functional Theory electronic structure and frequency calculations showed that, at V/Al f < 0.5, hydrolysis and subsequent dehydration led to the predominant formation of (VO 2 ) + species coordinated to one Al site with single-site catalytic behavior (0.7-0.9 × 10 -3 mol C 2 H 4 V -1 s -1 , 673 K). At higher V/Al f ratios, simulation of extended X-ray absorption fine structure spectra indicated that V 2 O 4 2+ dimers coexisted with VO 2 + monomers and led to an enhancement in ODH rates as a result of bridging V-O-V (1.3 × 10 -3 mol C 2 H 4 V -1 s -1 ). These V 5+ -oxo species form via initial reactions between VOCl 3(g) and OH groups to form HCl (g) , hydrolysis of grafted (VOCl 2 ) + to form HCl (g) and (VO(OH) 2 ) + , and intramolecular and intermolecular condensation to form monomers and dimers, respective with the concurrent evolution of H 2 O. Raman and X-ray spectroscopies did not detect crystalline V 2 O 5 at V/Al f ratios of 0.2-1, but V 2 O 5 crystals were apparent in samples prepared by impregnation or physical mixtures of V 2 O 5 /H-ZSM5. Framework Al atoms and zeolite crystal structures are maintained during VOCl 3 treatment and subsequent hydrolysis; 27 Al and 29 Si MAS NMR showed that these synthetic protocols removes <10% of the framework Al atoms (Al f ).

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Section: + Exchange Stoichiometry In H-zsm5mentioning

confidence: 99%

Synthesis, Structure, and Catalytic Reactivity of Isolated V⁵⁺-Oxo Species Prepared by Sublimation of VOCl₃ onto H-ZSM5

Lacheen

Iglesia

2006

J. Phys. Chem. B

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“…a nalysis. The structure of V20 5 was described by Bystr om et al [10] as havin g the space group P mrnn. wit h two molecules per unit cell, and t he indexed x-r ay powder diffraction pattern was r epor ted by Swanso n et al The comp ound V20 s·9N bz0 5 was fo un d to OCc ur in t he present stud y and to be stable to t he incongruent melting point at about 1290 °0.…”

Section: Compounds In the Pseud O-binar Y Systemmentioning

confidence: 99%

Phase equilibria in the system vanadium oxide-niobium oxide

Waring¹,

Roth²

1965

J. RES. NATL. BUR. STAN. SECT. A.

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Tbe p ha se diagram for the pseudo-binary system 1'20 5--Kb20 S was co nstructed from fusion c haracte ristics a n d x-ray diffraction . data. Three co mpounds wer.e postulated for thc system . . . . . In a dd it ion, the Nb20 5 ric h portions of the follo wmg bmary system s we re re lnvestlgatecl: ZnO -Nb20" NiO -Nb20 5, A120 3 -N b20 5, Ti02.-Nb20 5, and ZrOz-Nbz0 5• I n eac~ case an Nb20 5 sol id solution ha d been reported p reviou sly 1Il excess of ~O Illo.le p e.L' cent ~ b~? 5 . H OlI'c\'cr subsequ ent dn,ta JI1chcatecl t hat tbese ~b205 sohd SOlut lOll S co nt::unecl di SC I etc compo1l11~ls whi ch are l'r1 atcd to t.hose found in the pseudo-bina ry \'20 5-N b20 5 •

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“…8). In the monohydrate, the vanadium is in strict five-fold coordination with oxygen, forming a trigonal bipyramid configuration which links into endless chains of composition (V03 ) n" by sharing edges, A similar type of chain has been confirmed for VgOs by Bystrom, Wilhelmi, Brotzen (1950), but the chains are linked laterally to form sheets, and the vanadium coordination is distorted so that it approaches sixfold. The tvo structures are compared in figure 9> in which the end view of the chain elements are projected on the (001) planes.…”

Section: The Metavanaclatesmentioning

confidence: 95%

The crystal chemistry and mineralogy of vanadium

Evans¹

1956

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Transmitted herewith are three copies of TEI-622, "The crystal chemistry and mineralogy of vanadium," by Ho-ward T. Evans, Jr.Me are asking Mr. Hosted to approve our plan to publish this report as a chapter of a Geological Survey professional paper on mineralogy and geochemistry of the ores of the Colorado Plateau. Aelrnovledgment of AEC sponsorship will be made in the introductory chapter* .JAN iia 20U

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Vanadium Pentoxide - a Compound with Five-Coordinated Vanadium Atoms.

Cited by 197 publications

References 0 publications

Synthesis, Structure, and Catalytic Reactivity of Isolated V⁵⁺-Oxo Species Prepared by Sublimation of VOCl₃ onto H-ZSM5

Synthesis, Structure, and Catalytic Reactivity of Isolated V⁵⁺-Oxo Species Prepared by Sublimation of VOCl₃ onto H-ZSM5

Phase equilibria in the system vanadium oxide-niobium oxide

The crystal chemistry and mineralogy of vanadium

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Vanadium Pentoxide - a Compound with Five-Coordinated Vanadium Atoms.

Cited by 197 publications

References 0 publications

Synthesis, Structure, and Catalytic Reactivity of Isolated V5+-Oxo Species Prepared by Sublimation of VOCl3 onto H-ZSM5

Synthesis, Structure, and Catalytic Reactivity of Isolated V5+-Oxo Species Prepared by Sublimation of VOCl3 onto H-ZSM5

Phase equilibria in the system vanadium oxide-niobium oxide

The crystal chemistry and mineralogy of vanadium

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Product

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Synthesis, Structure, and Catalytic Reactivity of Isolated V⁵⁺-Oxo Species Prepared by Sublimation of VOCl₃ onto H-ZSM5

Synthesis, Structure, and Catalytic Reactivity of Isolated V⁵⁺-Oxo Species Prepared by Sublimation of VOCl₃ onto H-ZSM5