Metal−Oxygen Cluster Compounds (Heteropoly Oxometalates) of 1B and 3B Monovalent Cations and Their Micropore Structure

Parent, Magali; Moffat, J.B.

doi:10.1021/la9601667

Cited by 21 publications

(5 citation statements)

References 24 publications

(36 reference statements)

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“…Therefore NLDFT methods are likely more accurate in the reporting of phosphomolybdate surface areas, despite BET values being commonly reported. The NLDFT surface areas ranged from 0.387 to 28 [27,36,98], although work by Okuhara et al supports our finding [41]. The surface area also decreases with respect to increased cation size, which also contrasts with established findings [25,30,37,38,64].…”

Section: Discussioncontrasting

confidence: 85%

Structural and Activity Investigation into Al3+, La3+ and Ce3+ Addition to the Phosphomolybdate Heteropolyanion for Isobutane Selective Oxidation

et al. 2010

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Twelve phosphomolybdate compounds were synthesized via cationic exchange and were of the form: M x H 3-3x [PMo 12 O 40 ] (M = Al, La or Ce; 0 B x B 1). These compounds were analyzed by XRD and adsorption isotherm. Aluminum addition causes a primitive cubic phase, while lanthanum and cerium yield body-centered structures. La and Ce addition reduces surface area of phosphomolybdate structure. Temperature-programmed experiments for the selective oxidation of isobutane yielded methacrolein, 3-methyl-2-oxetanone (lactone), acetic acid (not with aluminous compounds), propene (only with aluminous compounds), carbon dioxide and water. The preference for propene rather than acetic acid formation with Al 3? may be due to the smaller cation size, or primitive cubic structure. These products form via two distinct reaction processes, labeled categories 1 and 2. Category 1 formation is associated with isobutane forming products on the surface, but reaction rate determined by bulk migration of charged particles. Category 2 formation is concerned with isobutane penetrating deep within the bulk of the substrate and forming products which subsequently desorb in a series of bell-shaped humps. Methacrolein forms via both category 1 and 2, whilst all other products form via category 2 exclusively. Kinetic analysis showed apparent activation barriers for category 1 methacrolein formation range from 67 ± 2 kJ mol -1 to [350 kJ mol -1 , and occur in groups with small, medium and large activation barriers. The addition of ?3 metal cations to the phosphomolybdate anion increase thermal stability, significantly decreasing deactivation; IR spectroscopy shows that the Keggin structure remains intact during temperature-programmed experiments with the Al, La and Ce salts.

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Section: Discussioncontrasting

confidence: 85%

Structural and Activity Investigation into Al3+, La3+ and Ce3+ Addition to the Phosphomolybdate Heteropolyanion for Isobutane Selective Oxidation

et al. 2010

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“…1B II), in agreement with those referred to in the literature [23] for this heteropolyacid. The first band is not assigned, while the others are ascribed to the stretching vibrations ence between the Al 3+ and [H 5 O 2 ] + cations, as was reported for diverse salts in the literature, where the variations in the lattice parameters have been attributed to such difference [25]. Instead, the diffraction pattern of the Cu 2+ salt (Fig.…”

Section: Resultsmentioning

confidence: 80%

2-Methoxynaphthalene acylation using aluminum or copper salts of tungstophosphoric and tungstosilicic acids as catalysts

et al. 2011

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“…It is evident that transformation of the HPA to the corresponding oxides is modified by the presence of these cations and the stability of the intermediate species between the hydrated form of the HPA and the increase in crystallized molybdenum oxide in the presence of the metal counterions. Earlier work has shown that the salts of the heteropoly acids prepared with monovalent cations have a higher thermal stability than those of the parent acids.…”

Section: Discussionmentioning

confidence: 99%

Structural Features and Thermal Stability of Titania-Supported 12-Molybdophosphoric Heteropoly Compounds

Damyanova

Fierro

1998

Chem. Mater.

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The structure and thermal decomposition of unsupported and titania-supported 12-phosphoromolybdic acid (HPMo) and its Co and Ni salts have been studied by different techniques including X-ray diffraction, thermogravimetric analysis, FT-infrared, Raman, and X-ray spectroscopic techniques. The transformation of heteropoly anion of bulk HPMo begins at a temperature lower than for its TiO 2 -supported counterpart with the formation of a mixture of R-and -MoO 3 . In the thermal transformation of TiO 2 -supported HPMo, two steps have been identified. The intermediate species formed between the hydrated form of the heteropoly compound and the crystallized molybdenum oxides display the same nuclearity and composition as that of the Keggin precursor. The stability of the HPA supported on titania increases due to the anion-support interaction and this is even enhanced in the Co-and Ni-exchanged homologues.

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Metal−Oxygen Cluster Compounds (Heteropoly Oxometalates) of 1B and 3B Monovalent Cations and Their Micropore Structure

Cited by 21 publications

References 24 publications

Structural and Activity Investigation into Al3+, La3+ and Ce3+ Addition to the Phosphomolybdate Heteropolyanion for Isobutane Selective Oxidation

Structural and Activity Investigation into Al3+, La3+ and Ce3+ Addition to the Phosphomolybdate Heteropolyanion for Isobutane Selective Oxidation

2-Methoxynaphthalene acylation using aluminum or copper salts of tungstophosphoric and tungstosilicic acids as catalysts

Structural Features and Thermal Stability of Titania-Supported 12-Molybdophosphoric Heteropoly Compounds

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