نتایج جستجو برای: α keggin
تعداد نتایج: 165395 فیلتر نتایج به سال:
A new double-Keggin-ion-templated, molybdenum-oxide-based organic-inorganic hybrid compound has been hydrothermally synthesized and its electrocatalytic properties investigated.
mixed-addenda vanadium substituted polyoxometalate supported on anatase tio2 crushed nano leaf was synthesized by an unusual reaction with titanium tetraisopropoxide at 100 ºc via sol–gel method under oil-bath condition. the materials characterized by xrd, tem, ir and uv–vis techniques. in the present work, efficient oxidative of thiols with polyoxometalate-tio2/hydrogen peroxide ...
The bulk structural evolution of a vanadium containing heteropolyoxomolybdate (HPOM), H4[PVMo11O40] * 13 H2O, with vanadium substituting for Mo in the Keggin ion was studied under reducing (propene) and partial oxidation reaction conditions (propene and oxygen) by in situ X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) combined with mass spectrometry. During treatment in propene...
A complimentary combination of Density Functional Theory (DFT) methodology and Electrospray Ionization-Mass Spectrometry (ESI-MS) has been utilized to increase our limited understanding of the first nucleation steps in the formation of the [XM(12)O(40)](n-) Keggin polyoxometalates (POMs) (where addenda metal atom M = W or Mo, and the heteroatom X = P or As). We postulate that the first key step...
A tetra-n-butylammonium (TBA) salt of a γ-Keggin -6-charged germanodecatungstate, [γ-H(2)GeW(10)O(36)](6-) (I), could act as an efficient homogeneous catalyst for Knoevenagel condensation of active methylene compounds with carbonyl compounds.
By using mixed rigid and flexible organic ligands, three Keggin based compounds, [Ag6(tbz)4(bmz)2(H3PW12O40)]·4H2O (1), [Ag(H2bdpm)2(H2PMo12O40)]·7.5H2O (2), and [Ag4(tbz)2(H2bdpm)2(HPMo12O40)]·2H2O (3) (Htbz = thiabendazole, Hbmz = benzimidazole, H2bdpm = 1,1'-bis(3,5-dimethyl-1H-pyrazolate)methane), were hydrothermally synthesized and structurally characterized. Through adopting rigid Htbz li...
When using heteropolycompounds in the selective oxidation of isobutane to methacrolein and methacrylic acid, both the keeping of the primary structure (Keggin units) and the presence of acidic sites are necessary to obtain the desired products. The structural evolution of supported (NH4)3HPMo11VO40 (APMV) catalysts under preliminary thermal oxidizing and reducing treatments was investigated. Va...
The rational self-assembly of mono-lacunary Keggin clusters with 4d and 4f metal salts via a conventional method has yielded two novel polyoxometalate-based 4d-4f heterometallic compounds containing lacunary Keggin anions connected to ten metal atoms: {[Ag{Ag2(H2O)4}{Ln(H2O)6}2H ⊂ {SiW11Ln(H2O)4O39}2]·nH2O (Ln = Ce and n = 7 for 1, Ln = Pr and n = 3 for 2). Their structures were determined by s...
Abstract A series of α -MoO 3 -TiO 2 mixed oxides were prepared by calcining a mixture the heteropolyacid H PMo 12 O 40 and TiO at temperatures ranging from 350 °C to 600 °C. The thus characterized tested for oxidation cyclohexene oxidizing /CO . FTIR XRD characterizations showed that Keggin structure was preserved calcination below 400 Above 450 °C, Keggin’s collapses. analysis revealed as tem...
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