Vanadium−antimony oxide selective oxidation catalysts are prepared using a novel peroxide-based sol−gel synthesis procedure. The catalysts are prepared by reaction of soluble peroxovanadium complexes with antimony trioxide under refluxing conditions. The procedure produces a stable colloidal sol of microcrystalline rutile vanadium antimonate having an average particle size of 6.7 nm. Drying the sol gives a gel consisting of pure rutile vanadium antimonate having the vanadium/antimony ratio of about 1/1, consistent with the stoichiometry of the well-characterized crystalline phase V8/9Sb8/9□2/9O4. The driving force for the formation of this phase is the redox reaction between a V5+peroxo complex and Sb3+oxide to form the V4+,Sb5+-containing vanadium antimonate. The peroxide-based sol−gel preparation procedure allows formation of vanadium antimonate under milder conditions than previous synthesis methods that rely on heating of mixtures of vanadium and antimony oxides.

High-resolution electron microscopy has been utilized to elucidate the structural nature of oxygen-containing planar inversion domain boundaries in aluminum nitride. A model for this defect is proposed which incorporates the necessary structural elements needed to describe the entire AlN-Al2O3 system. Image simulations of the proposed defect structure, for a range of imaging conditions, are in excellent agreement with experimental micrographs and provide substantial evidence for the validity of the proposed model.

The structure of a novel vanadyl (IV) orthophosphate hydrate (VO)3(PO4)2 · 9H2O has been solved and refined with the use of high resolution X-ray powder diffraction data taken on Beamline X7A at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL). The unit cell is monoclinic, P21n, Z = 2, a = 7.4315(1), b = 16.6256(2), c = 6.2954(1) Å, β = 92.388°(1)). The structure consists of large “squares” of (VO6PO4)4 moieties linked together by bridging PO4 tetrahedra and VO6 octahedra forming a corrugated layered structure in three dimensions with water molecules located within the open cells.

Na 0.5 Bi 0.5 MoO 4 (I), I4 1 /a, a=5.2717,c=11.5801A, R p =4.06%. Na 0.32 Bi 0.56 MoO 4 (II), I4 1 /a, a=5?2785, c=11.6410A, R p =4.82%. Na 0.5 Ce 0.5 MoO 4 (III), I4 1 /a a=5.31167, c=11.6600A, R p =12.34%. Na 0.5 La 0.5 MoO 4 (IV), I4 1 /a, a=5.3424, c=11.7376A, R p =10.82%.

Four synthetic iron titanium oxides with the pseudobrookite (AB2O5, Cmcm, Z = 4) structure have been prepared and characterized by neutron diffraction and zero-field, natural abundance 57Fe Mossbauer effect spectroscopy (MES). The combination of the element specificity of MES with the different neutron scattering lengths of Ti and Fe (−0.33 and 0.95 × 10−12 cm, respectively) offers a unique opportunity to distinguish between cation distributions on the two (“A” and “B”) sites. Two of the samples have been prepared in low temperature experiments (quenched from 1200°C) and have the stoichiometry FeTi2O5, and Fe.6Mg.6Ti1.8O5. The third and fourth samples are commercial iron titanium oxides prepared by the reduction of ilmenite ore with carbon above 1700°C. The stoichiometries of these samples are Mn0.05Fe0.33Ti2.52O5 and Fe.33Mg.31Ti2.36O5. Results from these experiments indicate that for each of these samples the B site is predominantly (>65%) occupied by Ti, while the A site contains a mixture of Ti, Fe, and/or Mg. However, only at higher temperatures (>1700°C) is the B site devoid of ferrous cations. These results suggest that an “ordered” model for ferrous titanium-rich oxides of the pseudobrookite structure (100% Ti occupancy of the B site) is descriptive only at elevated temperatures, and that at lower temperatures a “disordered” model (partial iron occupation of the B site) is a more accurate representation of the structure. Because of this difference, it may be possible to predict the thermal history of naturally occurring samples based on cation distributions.

The oxygen-related defect in an aluminum nitride (AIN) single crystal and in polycrystalline ceramics is investigated utilizing photoluminescence spectroscopy, thermal conductivity measurements, x-ray diffraction lattice parameter measurements, and transmission electron microscopy. The results of these measurements indicate that at oxygen concentrations near 0.75 at.%, a transition in the oxygen accommodating defect occurs. On both sides of this transition, simple structural models for the oxygen defect are proposed and shown to be in good agreement with the thermal conductivity and lattice parameter measurements, and to be consistent with the formation of various extended defects (e.g., inversion domain boundaries) at higher oxygen concentrations.

The thermal decomposition of two metastable ferrous titanium oxide compounds of commercial interest have been studied by in situ X-ray and neutron diffraction at elevated temperatures as well as by 57Fe Mossbauer effect spectroscopy. Thermal decomposition was monitored by collecting neutron diffraction data (taken at the Argonne National Laboratory Intense Pulsed Neutron Source (IPNS) powder diffractometers) at 30-min intervals at 900 and 1000°C. Previous work has shown that each of these materials (pseudobrookite structure, AB2O5), (Mn0.05Fe0.33Ti0.52)(Ti2.0)O5 and (Mg0.21Fe0.33Ti0.46)(Ti1.9Mg0.1)O5, has a significant amount of Ti in the +3 oxidation state and is completely ordered (no Fe located in the “B” site). The results of these “in situ” diffraction studies show that, prior to the thermal decomposition of the slags, there is a redistribution of cations within the pseudobrookite structure. Specifically, at temperatures in the range 600–700°C, iron cations move from the “A” sites to the “B” sites and Ti cations move from the “B” to the “A” sites. It is after this order-disorder transition that decomposition commences. At temperatures above 900°C, the neutron diffraction data show at least two modes of decomposition describing the high temperature chemistry of these disordered materials. The first mode produces iron metal and rutile (TiO2) and is modeled by the equation

AbstractBy the use of both X‐ray absorption near edge structure (XANES) and extended X‐ray absorption fine structure (EXAFS), the immediate coordination environments of the Bi and Mo cations in three bismuth molybdate phases with general composition Bi2O3·nMoO3, for n = 3 (α‐phase), n = 2 (β‐phase), n = 1 (γ‐phase) are probed.

It has been discovered that acetonitrile can be selectively oxidized in the vapor phase to glycolonitrile (hydroxyacetonitrile) or, in the presence of water, to glycolamide (hydroxyacetamide) using vanadium oxide catalysts. Partial reduction of the catalysts is required to obtain optimum selectivities to the desired partial oxidation products. Crystalline V6O13 present in active catalysts is apparently necessary for activation of acetonitrile by heterolytic CH bond cleavage. A general mechanism for this new catalytic reaction is proposed.

AbstractDie Gegenwart von MoO3 bewirkt, daß die a‐ β‐ Umwandlung von Sb2O4 statt bei 935 bei 850°C erfolgt und gleichzeitig Mo in der Hochtemp.‐Form (B) aufgelöst wird.

In order to understand the chemistry of altermetal dopants in antimony oxide, the detailed structural characterization of two β-Sb2O4 compounds is reported, Mo-doped β-Sb2O4 (1.5 metal%) and V-doped β-Sb2O4 (5 metal%). The methods used to characterize these materials are X-ray and neutron diffraction, scanning electron microscopy, Mo K-edge extended X-ray absorption fine structure spectroscopy, and elemental analysis. The atomic position of each of these dopants in Sb2O4 is radically different as is the overall effect on the host structure. Molybdenum does not substitute for Sb atoms, rather the Mo atoms are found in channels of electron density formed by Sb3+ lone pairs. The two nearest Sb3+ are absent and the oxygen stoichiometry is preserved. The formula is Sb1.97Mo0.015O4. Vanadium incorporates substitutionally for the Sb3+ atoms and there are random oxygen vacancies in the resultant structure. The formula is Sb1.9V0.1O3.67. In each case the atomic positions of the host structure (Sb and O) are remarkably unaltered. The β-Sb2O4 structure can accommodate Mo and V simultaneously, presumably both means of metal incorporation are employed in this ternary oxide.

The compositions FeSb2O6 and FeSb5O12 of the two-phase FeSbO4–α-Sb2O4 system, an active and selective catalyst for the oxidation and ammoxidation of propylene, have been structurally characterized by Rietveld analysis of powder neutron-diffraction data. Results of the analysis indicate that the presence of Sb2O4 has no effect on the bulk structural parameters of FeSbO4. Specifically (a) the unit cell of FeSbO4 does not depend upon the presence of Sb2O4 or calcination temperature, (b) antimony atoms are not found in the intersticies of the coexisting iron antimonate and (c) the apparent Sb/Fe ratio is 1 in iron antimonate. Additionally, the Sb/Fe occupancy in the rutile FeSbO4 structure is random as no supercell reflections were observed. Results of scanning electron microscope and X-ray photoelectron spectroscopy experiments have been interpreted to show that Sb enrichment occurs on coprepared samples of the two-phase mixture. Based on this evidence and the lack of alteration of the bulk structures of both phases it is suggested that surface alteration in this two-phase system is the key to enhanced selective catalytic oxidation activity.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStabilization of high-temperature antimony oxide with molybdenum incorporation. Structure of molybdenum-doped antimony oxide (Sb2O4) by powder neutron diffraction and extended x-ray absorption fine structure spectroscopyRaymond G. Teller, Mark R. Antonio, James F. Brazdil, M. Mehicic, and Robert K. GrasselliCite this: Inorg. Chem. 1985, 24, 21, 3370–3375Publication Date (Print):October 1, 1985Publication History Published online1 May 2002Published inissue 1 October 1985https://pubs.acs.org/doi/10.1021/ic00215a015https://doi.org/10.1021/ic00215a015research-articleACS PublicationsRequest reuse permissionsArticle Views170Altmetric-Citations17LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

The Bi2-xCexMo3O12 two phase system has been examined for its activity in the catalytic oxidation of propylene to acrylonitrile. The two phases have been characterized as a solid solution of Bi in cerium molybdate and Ce in bismuth molybdate. Results of these oxidation studies have been correlated with structural results on the pure and doped end members. A plot of catalytic activity versus x shows three maxima which coincide with the maximum concentration of Ce in Bi2Mo3O12, Bi in Ce2Mo3O12 and equal concentrations of cerium in bismuth molybdate and bismuth in cerium molybdate. These results suggest that selective propylene ammoxidation occurs in a trifunctional matrix which contains metals that; activate propylene to form an allyl intermediate (Bi), insert oxygen into the allylic intermediate, (Mo) and contain a redox couple (Ce). Aspects of phase cooperation in a multiphase catalyst are also discussed.

The structure of Bi1.8Ce0.2(MoO4)3 has been refined with powder neutron diffraction data by the Rietveld method. The structure can be derived by severely distorting the scheelite structure (AMO4) and is perhaps better written A23Ø13MO4, where Ø = cation vacancy. Of the two bismuth atom sites, cerium preferentially occupies the more symmetric of the two (Bi(2) in the structure) with some cerium found in the scheelite subcell vacancies also. This site preference is understood by examining the symmetries of the two Bi sites. Crystal data: monoclinic, space group P21c, Z = 4, a = 7.697(2), b = 11.535(3), c = 11.944(3), β = 115.19.

AbstractMittels Einkristall‐Röntgenbeugungsuntersuchungen werden die Strukturen des durch Umsetzung von ReCl3(PMe3Ph)3 bzw. ReC 4(PMe3Ph)3 in THF mit LiAlH4 erhaltenen Titel‐Pentahydrids (61% Ausb.) bzw. ‐Heptahydrids (29%) bestimmt.

The structures of H5Re(PMe2Ph)3 and H7Re(PMe2Ph)2 have been solved by single-crystal X-ray diffraction methods. Although the hydride ligands could not be directly located in this study, the overall structure of the complexes could be deduced from a knowledge of the central rhenium/phosphorus core of the molecules. The ReP3 skeleton of H5Re(PMe2Ph)3 has distorted pyramidal geometry (PReP angles 149.5°, 101.9°, 99.8°) consistent with dodecahedral structure for the H5ReP3 core. The ReP2 backbone of H7Re(PMe2Ph)2 is bent (PReP angle 146.8°), suggesting a tricapped trigonal prismatic geometry for the H7ReP2 core in which the P atoms are placed in opposing axial and equatorial positions. Crystallographic details: H5Re(PMe2Ph)3: space group P21/c (monoclinic); a = 6.876(3) Å, b = 19.493(7) Å, c = 19.646(8) Å, β = 103.26(2)°, V = 2563.0 Å3, Z = 4; R = 6.7% for 2067 reflections. H7Re(PMe2Ph)2: space group P21/n (monoclinic); a = 19.083(17) Å, b = 6.337(4) Å, c = 15.234(13) Å, β = 93.72(4)°, V = 1834.0 Å3, Z = 4; R = 5.0% for 1672 reflections.