1314-11-0Relevant articles and documents
The superconductor (Tl,Hg,Ca)2- (Ba,Sr)2(Ca,Sr,Tl)Cu2O7.6
Valldor, Martin,Bryntse, Ingrid,Morawski, Andrzej
, p. i126-i128 (2002)
The crystal structure of superconductor (Tl,Hg,Ca)2-(Ba,Sr)2(Ca,Sr,Tl)Cu2O7.6 was investigated. The compound contained both Tl and Hg in the charge reservoir (CR), Sr is located at both alkali-earth (AE) metal
Deciphering local complex order by HAADF in a disordered mixed polyanion iron oxide: Sr4Fe2[Fe0.5(SO4)0.25(CO3)0.25]O7.25
Gonano, Bruno,Bréard, Yohann,Pelloquin, Denis,Caignaert, Vincent,Pérez, Olivier,Pautrat, Alain,Bazin, Philippe,Suard, Emmanuelle,Boullay, Philippe
, p. 13088 - 13093 (2018/10/02)
A layered iron compound involving two divalent polyanions (carbonate and sulfate anions) was synthesized by solid state chemistry in a closed ampule in the form of a ceramic. The Sr4Fe2[Fe0.5(SO4)0.25(CO3)0.25]O7.25 compound derives from the third term of the Ruddlesden and Popper family, Sr4Fe3O10. A multiscale approach through transmission electron microscopy (TEM) and powder neutron diffraction (PND) studies shows that SO4 and CO3 groups substitute for the iron polyhedron of the central layer of the perovskite blocks and the absence of long range ordering between sulfate and carbonates and FeO5 groups. Nevertheless, waves disturbing the expected periodicity of the atomic layer are evidenced in HAADF images. An accurate analysis of these images provides a view of the local cationic order correlated with SO4 and CO3 for FeO5 substitution.
Characterization of an alkaline earth metal-doped solid superacid and its activity for the esterification of oleic acid with methanol
Huang, Chien-Chang,Yang, Chieh-Ju,Gao, Pei-Jyuan,Wang, Nai-Ci,Chen, Ching-Lung,Chang, Jo-Shu
, p. 3609 - 3620 (2015/06/25)
The leaching of grafted sulfate groups is one of the major issues for the solid acid catalysts with sulfate modification. A detailed study of sulfated alkaline earth metal-ferric composite oxides was carried out to suppress the leaching of sulfate groups as well as maintain high reactivity during the esterification of oleic acid. The acid properties and quantities of the active sites present on the catalysts were studied with pyridine-adsorption, FT-IR, TGA, and titration methods. The following order of acidic strength was observed: SO42-/Sr-Fe oxide > SO42-/Ca-Fe oxide > SO42-/Mg-Fe oxide. After sulfate modification, sulfate ions are linked to the composite oxides in a bridged bidentate form. SO42-/Sr-Fe oxide exhibits superacidic nature due to the high induction effect of the sulfated ion grafted on the Sr cation. TGA and FT-IR spectroscopic analyses provide new insights into the function of the iron cations implanted on the catalyst surface for enhancing the turnover frequency (TOF) of the active sites on SO42-/Sr-Fe oxide in the esterification. It was verified that the active energy of SO42-/Sr-Fe oxide for the esterification of oleic acid with methanol was as low as 28.53 ± 0.72 kJ mol-1. In the reusability study, SO42-/Sr-Fe oxide exhibited high reusability in the esterification, due to the high stability of the sulfate ion grafted on SO42-/Sr-Fe oxide.
High-pressure synthesis and crystal structures of the strontium oxogallates Sr2Ga2O5 and Sr5Ga6O14
Kahlenberg, Volker,Goettgens, Valerie,Mair, Philipp,Schmidmair, Daniela
, p. 27 - 35 (2015/05/13)
Abstract High-pressure synthesis experiments in a piston-cylinder apparatus at 1.5 GPa/3.0 GPa and 1000°C resulted in the formation of single-crystals of Sr2Ga2O5 and Sr5Ga6O14, respectively. The structures of both compounds have been solved from single-crystal diffraction data sets using direct methods. The first compound is orthorhombic with space group type Pbca (a=10.0021(4) ?, b=9.601(4) ?, c=10.6700(4) ?, V=1024.6(4) ?3, Mr=394.68 u, Z=8, Dx=5.12 g/cm3) and belongs to the group of single layer gallates. Individual sheets are parallel to (0 0 1) and can be built from the condensation of unbranched vierer single chains running along [0 1 0]. The layers are characterized by the presence of four- and strongly elliptical eight-membered rings of corner connected tetrahedra in UUDD and UUUUDDDD conformation. Strontium atoms are sandwiched between the tetrahedral layers for charge compensation and are coordinated by six and seven oxygen ligands, respectively. Sr2Ga2O5 is isotypic with several other double sulfides and selenides. To the best of our knowledge, it is the first example of an oxide with this structure type. From a structural point of view, Sr5Ga6O14 is a phyllogallate as well. The crystal structure adopts the monoclinic space group P21/c (a=8.1426(3) ?, b=8.1803(3) ?, c=10.8755(4) ?, β=91.970(4)°V=723.98(5) ?3, Mr=1080.42 u, Z=2, Dx=4.96 g/cm3). Individual sheets extend along (0 0 1). Basic building units are unbranched dreier single chains parallel to [1 0 0]. The layers contain tertiary (Q3) und quaternary (Q4) connected [GaO4]-tetrahedra in the ratio 2:1 resulting in a Ga:O ratio of 3:7 and the formation of exclusively five-membered rings. Linkage between adjacent tetrahedral sheets is provided by three symmetrically independent strontium ions which are surrounded by six to eight oxygen atoms. The layers in Sr5Ga6O14 are similar to those observed in the melilite structure-type. Crystallochemical relationships between the present phases and other known compounds are discussed in detail.
Synthesis and crystal structure of oxygen-deficient Bilayer Ruthenate Sr3Ru2O7-δ
Martinez-Anaya, Oliver,Garcia-Valdes, Jesus,De La Mora, Pablo,Tavizon, Gustavo
, p. 777 - 783 (2014/06/09)
The structural properties of oxygen-deficient Ruddlesden-Popper-type Sr3Ru2O7-δ compounds are presented. Sr3Ru2O7-δ compounds (δ≤0.17, 0.23, 0.28, 0.40, and 0.47) were obtained by hydrogen reduction of the parent Sr3Ru2O7 ruthenate. Rietveld structure refinements were performed to determine the crystal structure of the reduced compounds. Oxygen deficiency in the samples was studied by redox titrations and the Ru3+ content was confirmed by electron paramagnetic resonance. Magnetisation measurements were performed to study the magnetic response of the reduced phases. Removal of the oxygen atoms from the parent compound resulted in the decrease of the c-lattice parameter and increase of the a-lattice parameter that is related to partial reduction of Ru4+, in Sr3Ru2O7, to Ru3+. Rietveld analyses showed that the apical oxygen atoms of the RuO6 octahedra were partially lost during reduction. Redox titration experiments showed a linear correlation between reduction of the compounds and the annealing time under H2. CSIRO 2014.
One-pot synthesis of glycidol from glycerol and dimethyl carbonate over a highly efficient and easily available solid catalyst NaAlO2
Bai, Rongxian,Zhang, Hongkun,Mei, Fuming,Wang, Shu,Li, Tao,Gu, Yanlong,Li, Guangxing
, p. 2929 - 2934 (2013/10/08)
The one-pot synthesis of glycidol from glycerol and dimethyl carbonate (DMC) was developed by using a solid base catalyst. A series of solid base catalysts have been investigated in this reaction. It was found that NaAlO 2, a cheap and easily available raw material, was a highly efficient heterogeneous catalyst for the one-pot synthesis of glycidol, and it can be easily recovered and reused. Under the reaction conditions of a DMC-glycerol molar ratio of 2, catalyst-glycerol weight ratio of 3%, reaction time of 90 min, and temperature of 80-92 °C, the conversion of glycerol and the selectivity to glycidol reached 94.7% and 80.7%, respectively. Activity tests of the catalyst after exposure to the air showed that, to a certain extent, the NaAlO2 catalyst is tolerant to water and carbon dioxide, which makes the present system a practically interesting process for glycidol synthesis.
METHOD OF MAKING ALCOHOLS
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Page/Page column 9, (2013/03/26)
A method of making one or more alcohols with a single hydroxy group, such as methanol and ethanol, the method comprising contacting a polyol and water with a basic catalyst. The polyol may be glycerol, for example. The '. catalyst may be magnesium oxide.
Topochemical fluorination of Sr3(M0.5Ru 0.5)2O7 (M = Ti, Mn, Fe), n = 2, Ruddlesden-popper phases
Romero, Fabio Denis,Bingham, Paul A.,Forder, Susan D.,Hayward, Michael A.
, p. 3388 - 3398 (2013/05/08)
Reaction of the appropriate Sr3(M0.5Ru 0.5)2O7 (M = Ti, Mn, Fe), n = 2, Ruddlesden-Popper oxide with CuF2 under flowing oxygen results in formation of the oxide-fluoride phases Sr3(Ti0.5Ru 0.5)2O7F2, Sr3(Mn 0.5Ru0.5)2O7F2, and Sr3(Fe0.5Ru0.5)2O 5.5F3.5 via a topochemical anion insertion/substitution process. Analysis indicates the titanium and manganese phases have Ti 4+, Ru6+ and Mn4+, Ru6+ oxidation state combinations, respectively, while Moessbauer spectra indicate an Fe3+, Ru5.5+ combination for the iron phase. Thus, it can be seen that the soft fluorination conditions employed lead to formation of highly oxidized Ru6+ centers in all three oxide-fluoride phases, while oxidation states of the other transition metal M cations remain unchanged. Fluorination of Sr3(Ti0.5Ru0.5) 2O7 to Sr3(Ti0.5Ru 0.5)2O7F2 leads to suppression of magnetic order as the fluorinated material approaches metallic behavior. In contrast, fluorination of Sr3(Mn0.5Ru0.5) 2O7 and Sr3(Fe0.5Ru 0.5)2O7 lifts the magnetic frustration present in the oxide phases, resulting in observation of long-range antiferromagnetic order at low temperature in Sr3(Mn0.5Ru 0.5)2O7F2 and Sr3(Fe 0.5Ru0.5)2O5.5F3.5. The influence of the topochemical fluorination on the magnetic behavior of the Sr3(M0.5Ru0.5)2OxF y phases is discussed on the basis of changes to the ruthenium oxidation state and structural distortions.
Volatile Imidazoles and Group 2 Imidazole Based Metal Precursors
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Page/Page column 29, (2012/02/15)
Sterically hindered imidazole ligands are described, along with their synthesis, which are capable of coordinating to Group 2 metals, such as: calcium, magnesium, strontium, in an eta-5 coordination mode which permits the formation of monomeric or dimeric
Role of SrMoO4 in Sr2MgMoO6 synthesis
Vasala,Yamauchi,Karppinen
, p. 1312 - 1317 (2011/08/04)
Here we investigate the elemental and phase compositions during the solid-state synthesis of the promising SOFC-anode material, Sr 2MgMoO6, and demonstrate that molybdenum does not notably evaporate under the normal synthesis conditions with temperatures up to 1200 °C due to the formation of SrMoO4 as an intermediate product at low temperatures, below 600 °C. However, partial decomposition of the Sr2MgMoO6 phase becomes evident at the higher temperatures (～1500 °C). The effect of SrMoO4 on the electrical conductivity of Sr2MgMoO6 is evaluated by preparing a series of Sr2MgMoO6 samples with different amounts of additional SrMoO4. Under the reducing operation conditions of an SOFC anode the insulating SrMoO4 phase is apparently reduced to the highly conductive SrMoO3 phase. Percolation takes place with 2030 wt% of SrMoO4 in a Sr2MgMoO6 matrix, with a notable increase in electrical conductivity after reduction. Conductivity values of 14, 60 and 160 S/cm are determined at 800 °C in 5% H2/Ar for the Sr2MgMoO6 samples with 30, 40 and 50 wt% of added SrMoO4, respectively.
