Catalytic properties of a mixed calcium-cobalt orthophosphate, II. Determination of the active sites in propan-2-OL dehydrogenation

Legrouri, A.; Lenzi, Jacopo; Lenzi, Marcelo Kaminski

doi:10.1007/bf02475257

Cited by 7 publications

(4 citation statements)

References 12 publications

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“…Whitlockite or β-Ca 3 (PO 4 ) 2 -like compounds, for example, Ca 9 R(VO 4 ) 7 (R = rare-earth metals and Bi), have been extensively studied in expectation of their applications as nonlinear optical (NLO) materials. − In Ca 9 Bi(VO 4 ) 7 , its NLO signal is about 3 times as large as that of KH 2 PO 4 . Tricalcium bis(phosphate), Ca 3 (PO 4 ) 2 , pure and doped with foreign cations has also been investigated as likely candidates for biomaterials, − luminescent materials, and catalysts …”

Section: Introductionmentioning

confidence: 99%

Polar and Centrosymmetric Phases in Solid Solutions Ca₃_-_xSr_x(PO₄)₂ (0 ⩽ x ⩽ 16/7)

et al. 2002

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Solid solutions Ca 3-x Sr x (PO 4 ) 2 (0 e x e 16/7) were studied by X-ray powder diffraction, infrared spectroscopy, differential scanning calorimetry, electrical-conductivity measurements, and second-harmonic generation. Phosphates with 0 e x e 12/7 ( -phase) crystallize in space group R3c, Z ) 21, a ≈ 10 Å, and c ≈ 38 Å. Sr-rich phosphates with 13/7 e x e 16/7 ( ′-phase) have a somewhat different crystal structure: space group R3 hm, Z ) 10.5, a ≈ 10 Å, and c ≈ 19 Å. The solid solutions with 0 e x e 12/7 showed a reversible high-temperature phase transition a ′, where the and ′ phases have noncentrosymmetric and centosymmetric structures, respectively. The temperature of the phase transition decreased with increasing Sr content. In Ca 3 (PO 4 ) 2 , a new phase transition, a ′, was observed at 920°C in the electrical-conductivity measurements. The structure parameters of polar -Ca 2 Sr(PO 4 ) 2 (x ) 1) and centrosymmetric ′-Ca 5/7 Sr 16/7 (PO 4 ) 2 (x ) 16/7) at room temperature were refined by Rietveld refinements of the X-ray diffraction data: space group R3c, Z ) 21, a ) 10.5612(2) Å, and c ) 38.0588 (5) Å for -Ca 2 Sr(PO 4 ) 2 and space group R3 hm, Z ) 10.5, a ) 10.7015(2) Å, and c ) 19.5787(2) Å for ′-Ca 5/7 Sr 16/7 (PO 4 ) 2 . -Ca 2 Sr(PO 4 ) 2 is isotypic with -Ca 3 (PO 4 ) 2 . In -Ca 2 Sr(PO 4 ) 2 , the M4 site is 50% occupied by Sr 2+ ions, and the M6 site is vacant. In both structures, Ca 2+ and Sr 2+ ions enter the M1-M3 sites whereas Ca 2+ ions selectively occupy the M5 site. ′-Ca 5/7 Sr 16/7 (PO 4 ) 2 contains some disordered atoms: (1) cations at the M3 site are statistically distributed among several positions near the center of symmetry, (2) P1O 4 tetrahedra are orientationally disordered, and (3) the M4 site (M6 site in -Ca 2 Sr(PO 4 ) 2 ) is occupied by 0.165Sr 2+ + 0.085Ca 2+ + 0.750. The mechanism of the a ′ phase transition in Ca 3-x Sr x (PO 4 ) 2 (0 e x e 12/7) is discussed on the basis of the crystal data.

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Section: Introductionmentioning

confidence: 99%

Polar and Centrosymmetric Phases in Solid Solutions Ca₃_-_xSr_x(PO₄)₂ (0 ⩽ x ⩽ 16/7)

et al. 2002

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“…β-TCP has been used as an ideal candidate for bone substitute, inorganic filling of biodegradable composites, substrate for evaluation of cell seeding efficacy, proliferation, osteogenic differentiation, and carrier for bone growth factors to stimulate bone healing and formation, because of its excellent osteoconductive and biodegenerative characteristics . Besides, it can also find other applications of this compound, which involve drug carrier, luminescence materials, and catalyst . It has been reported that the protein adsorption property of β-TCP is dependent upon its size and terminal facets .…”

Section: Introductionmentioning

confidence: 99%

Controls of Tricalcium Phosphate Single-Crystal Formation from Its Amorphous Precursor by Interfacial Energy

Tao

Pan

Zhai

et al. 2009

Crystal Growth & Design

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Different from the conventional solution precipitation, amorphous precursor involves widely in biomineralizations. It is believed that the development of crystalline structures with a well-defined shape in biological systems is essentially facilitated by the occurrence of these transient amorphous phases. However, the previous studies have not elucidated the physicochemical factors influencing the transformation from the transient phase into the stable phase. In this study, the evolutions from the amorphous calcium phosphate to the different-shaped (hexagon and octahedron; octahedron is an unexpected morphology of the crystal with space group of R3̅c) single crystals of β-tricalcium phosphate (β-TCP) were examined. The hexagonal β-TCP crystals were formed via the phase transformation of amorphous precursor in CaCl2−Na2HPO4-ethylene glycol solution; however, the octahedral β-TCP crystals were formed in Ca(OH)2-(NH4)2HPO4-ethylene glycol solution. Because the interfacial energies between amorphous phase and crystals were much smaller than those between solutions and crystals, the crystallization of the β-TCP phase occurred directly in the amorphous substrate rather than from the solution. It was interesting that the final morphology of product was also determined by the interfacial energy between the transformed crystal and solution. The current work demonstrated that the amorphous precursor epitaxial nucleation process and morphology selection of crystals in the amorphous phase could also be understood by an interfacial energy control. This result might provide an in-depth understanding of the biomimetic synthesis of crystals via a pathway of amorphous precursors.

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“…Kobaltphosphat als heterogener Katalysator eingesetzt werden kann. [145,[146][147][148] In der chemischen Industrie ist Katalyse ein großes Thema, weil erst durch katalysierte Reaktionen eine schnelle, energiesparende und dadurch umweltschonende Produktion möglich wird.…”

Section: Schlussfolgerungunclassified

“…[180] Kobaltorthophosphat ist ein heterogener Katalysator, der die Reaktion der oxidativen Dehydrierung und Dehydratisierung von leichten Kohlenwasserstoffen katalysieren kann. Legrouri et al [146,147] untersuchten den Calcium-Kobaltphosphatkatalysator hinsichtlich aktiver Zentren an- Schema 3-1. Katalytische Reaktion von Butan-2-ol mit Sauerstoff zu den Produkten Buten und Butanon.…”

Section: üBerlegungen Zur Katalytischen Aktivität Von Kobaltphosphatunclassified

Experimentelle Ladungsdichteuntersuchungen von nichtkovalenten Wechselwirkungen

Helena¹

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Catalytic properties of a mixed calcium-cobalt orthophosphate, II. Determination of the active sites in propan-2-OL dehydrogenation

Cited by 7 publications

References 12 publications

Polar and Centrosymmetric Phases in Solid Solutions Ca₃_-_xSr_x(PO₄)₂ (0 ⩽ x ⩽ 16/7)

Polar and Centrosymmetric Phases in Solid Solutions Ca₃_-_xSr_x(PO₄)₂ (0 ⩽ x ⩽ 16/7)

Controls of Tricalcium Phosphate Single-Crystal Formation from Its Amorphous Precursor by Interfacial Energy

Experimentelle Ladungsdichteuntersuchungen von nichtkovalenten Wechselwirkungen

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Catalytic properties of a mixed calcium-cobalt orthophosphate, II. Determination of the active sites in propan-2-OL dehydrogenation

Cited by 7 publications

References 12 publications

Polar and Centrosymmetric Phases in Solid Solutions Ca3-xSrx(PO4)2 (0 ⩽ x ⩽ 16/7)

Polar and Centrosymmetric Phases in Solid Solutions Ca3-xSrx(PO4)2 (0 ⩽ x ⩽ 16/7)

Controls of Tricalcium Phosphate Single-Crystal Formation from Its Amorphous Precursor by Interfacial Energy

Experimentelle Ladungsdichteuntersuchungen von nichtkovalenten Wechselwirkungen

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Polar and Centrosymmetric Phases in Solid Solutions Ca₃_-_xSr_x(PO₄)₂ (0 ⩽ x ⩽ 16/7)

Polar and Centrosymmetric Phases in Solid Solutions Ca₃_-_xSr_x(PO₄)₂ (0 ⩽ x ⩽ 16/7)