- Synthesis of bimetallic trifluoroacetates through a crystallochemical investigation of their monometallic counterparts: The case of (A, A′)(CF3COO)2·: N H2O (A, A′ = Mg, Ca, Sr, Ba, Mn)
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Owing to their potential as single-source precursors for compositionally complex materials, there is growing interest in the rational design of multimetallic compounds containing fluorinated ligands. In this work, we show that chemical and structural principles for a materials-by-design approach to bimetallic trifluoroacetates can be established through a systematic investigation of the crystal-chemistry of their monometallic counterparts. A(CF3COO)2·nH2O (A = Mg, Ca, Sr, Ba, Mn) monometallic trifluoroacetates were employed to demonstrate the feasibility of this approach. The crystal-chemistry of monometallic trifluoroacetates was mapped using variable-temperature single-crystal X-ray diffraction, powder X-ray diffraction, and thermal analysis. The evolution with temperature of the previously unknown crystal structure of Mg(CF3COO)2·4H2O was found to be identical to that of Mn(CF3COO)2·4H2O. More important, the flexibility of Mnx(CF3COO)2x·4H2O (x = 1, 3) to adopt two structures, one isostructural to Mg(CF3COO)2·4H2O, the other isostructural to Ca3(CF3COO)6·4H2O, enabled the synthesis of Mg-Mn and Ca-Mn bimetallic trifluoroacetates. Mg0.45Mn0.55(CF3COO)2·4H2O was found to be isostructural to Mg(CF3COO)2·4H2O and exhibited isolated metal-oxygen octahedra with Mg2+ and Mn2+ nearly equally distributed over the metal sites (Mg/Mn: 45/55). Ca1.72Mn1.28(CF3COO)6·4H2O was isostructural to Ca3(CF3COO)6·4H2O and displayed trimers of metal-oxygen corner-sharing octahedra; Ca2+ and Mn2+ were unequally distributed over the central (Ca/Mn: 96/4) and terminal (Ca/Mn: 38/62) octahedral sites.
- Dulani Dhanapala,Mannino, Natalie A.,Mendoza, Laura M.,Tauni Dissanayake,Martin, Philip D.,Suescun, Leopoldo,Rabuffetti, Federico A.
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- Photoluminescence of nanocrystalline SrMgF4 prepared by a solution chemical route
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SrMgF4 was prepared by precipitation in aqueous solution. Alkaline earth metal acetates and ammonium fluoride were used as precursors. After drying and annealing the samples at different temperatures and times, single phase SrMgF4 was obtained. By varying the annealing conditions, the mean crystallite size could be adjusted. Furthermore, the thermally treated samples displayed UV-excited intensive broad band luminescence in the visible region. The emissions colour and intensity can be adjusted by the tempering conditions. X-Ray diffraction, TEM-microscopy, fluorescence and IR-spectroscopy were used for analysis.
- C.Veitsch,Kubel,Hagemann
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- Defluorination of graphite fluoride applying magnesium
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Consolidated stoichiometric mixtures of graphite fluoride (1) and magnesium (2) upon ignition under argon atmosphere (0,1 MPa) yield very high flame temperature of ～ 5600 K as determined by infrared emission spectroscopy. The combustion product was analysed by X-ray powder diffraction and revealed the presence of magnesium fluoride and graphite as well as structurally low ordered carbon. A possible reaction mechanism is discussed.
- Koch, Ernst-Christian
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- The influence of HS-AlF3 on the decomposition reaction of MgH2
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The influence of nanoscopic aluminium fluoride prepared via a sol-gel-synthesis route developed by our group on the thermal decomposition of MgH2 used as hydrogen storage material has been comprehensively investigated. Combined XRD and MAS NMR experiments have been performed to follow structural changes in ball milled MgH2/HS-AlF3 mixtures at thermal decomposition. Although the behaviour of Lewis acidic metal fluorides is discussed being catalytic, our results with HS-AlF3 clearly give a different picture. We found strong evidence for a decrease of the decomposition temperature in combination with a significant acceleration of the decomposition rate; however, the action of at least AlF3 is not catalytic in nature. As shown, a fluoride against hydride exchange is taking place, thus transforming AlF3 irreversibly into AlH3, which is followed by decomposition into metallic Al (MgAl alloy).
- Noack, Johannes,Scholz, Gudrun,Rüdiger, Stephan,Feist, Michael,Kemnitz, Erhard
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- Synthesis and characterization of MgF2 and KMgF3 nanorods
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MgF2 nanorods with diameters of 60-100nm were synthesized by a microemulsion method. Subsequent hydrothermal reaction of as-synthesized MgF2 nanorods and KF at 240°C for 3 days or 140°C for 7 days resulted in KMgF3 nanorods, which retained the rod-like morphology of the source material MgF2 in the reaction process. The morphology of as-synthesized MgF2 strongly depended on the molar ratio between water and the surfactant CTAB and the concentration of CTAB.
- Cao, Minhua,Wang, Yonghui,Qi, Yanjuan,Guo, Caixin,Hu, Changwen
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- Synthesis and characterization of new Mg-O-F system and its application as catalytic support
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The Mg-O-F system (MgF2-MgO) with different contents of MgF2 (100-0%) and MgO is tested as support of iridium catalysts in the hydrogenation of toluene as a function of the MgF2/MgO ratio. Mg-O-F samples have been prepared by the reaction of magnesium carbonate with hydrofluoric acid. The MgF2-MgO supports, after calcination at 500 °C, are classified as mesoporous of surface area (34-135 m2·g- 1) depending on the amount of MgO introduced. The Ir/Mg-O-F catalysts have been tested in the hydrogenation of toluene. The highest activity, expressed as TOF, min- 1, was obtained for the catalyst supported on Mg-O-F containing 75 mol%MgF2.
- Zieliński, Micha?,Kiderys, Angelika,Pietrowski, Mariusz,Tomska-Foralewska, Iwona,Wojciechowska, Maria
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- BaSr(NH4)Mg5F15, A tetragonal tungsten bronze structure with ammonium barium disorder and its solid solutions Ba xSr2-x(NH4)Mg5F15 (x = 1.8-0.6)
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The new fluoride BaSr(NH4)Mg5F15 precipitates as a nanocrystalline powder from aqueous solutions of the alkaline earth ions and ammonium fluoride. The compound crystallizes in the tetragonal tungsten bronze structure type with lattice parameters of a,b = 12.4492(14) A and c = 3.9421(4) A (space group P4/mbm [Nr. 127], structure refinement from powder data, RBragg = 4.0%). Corner-linked magnesium-fluoride octahedra form a channel structure which contains one empty triangular channel, one channel filled with Sr2+ [CN = 8+4] and one channel with disordered Ba2+ and NH4+ (ratio 1:1) with CN = 7+8. Solid solutions between the composition limits Ba(Ba0.8Sr 0.2)(NH4)Mg5F15 and (Ba 0.6Sr0.4)Sr(NH4)Mg5F15 were obtained. The crystallite size increases from 15 to 75 nm with increasing barium concentration. The thermal stability between 350 to 450°C depends on the amount of absorbed (NH4)F. Heated samples show luminescence and phosphorescence.
- Kubel,Pantazi
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- Improving hydrogen sorption kinetics of MgH2 by mechanical milling with TiF3
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MgH2 + TiF3 system was mechanically prepared and investigated with regard to hydrogen absorption/desorption performance. It was found that the sorption kinetics of MgH2 can be markedly improved by mechanical milling with 4 mol% TiF3, in particular at reduced operation temperatures. Even at a moderate temperature range (313-373 K), the hydrogen absorption can be largely completed within about 25 s. On the desorption aspect, the catalytic enhancement arising upon adding TiF3 allows the sample to desorb near 5 wt.% hydrogen within 600 s at 573 K. Furthermore, such enhancement in kinetics was observed to persist in the absorption/desorption cycles. Preliminary XRD examination was also performed to understand the observed catalytic effect of TiF3 additive.
- Ma, Lai-Peng,Wang, Ping,Cheng, Hui-Ming
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- Reaction of magnesium oxide and magnesium silicates with ammonium hydrodifluoride
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The reactions of magnesium oxide and magnesium silicates (forsterite and serpentines) with ammonium hydrodifluoride is studied using DTA, X-ray powder diffraction, and IR spectroscopy. The conditions for the formation of intermediate phases are determined
- Nesterov,Makarov,Kalinnikov
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- Sol-gel-fluorination synthesis of amorphous magnesium fluoride
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The sol-gel fluorination process is discussed for the reaction of magnesium alkoxides with HF in non-aqueous solvents to give X-ray amorphous nano-sized magnesium fluoride with high surface areas in the range of 150-350 m 2/g (HS-MgF2). The H2 type hysteresis of nitrogen adsorption-desorption BET-isotherms is indicative for mesoporous solids. A highly distorted structure causes quite high Lewis acidity, shown by NH 3 temperature-programmed desorption (NH3-TPD) and catalytic test reactions. XPS data of amorphous and conventionally crystalline MgF2 are compared, both show octahedral coordination at the metal site. Thermal analysis, F-MAS NMR- and IR-spectroscopy give information on composition and structure of the precursor intermediate as well as of the final metal fluoride. The preparation of complex fluorides, M+MgF 3-, by the sol-gel route is reported. From the magnesium fluoride gel of the above process thin films for optical application are obtained by, e.g., spin coating.
- Krishna Murthy,Gross, Udo,Ruediger, Stephan,Kemnitz, Erhard,Winfield, John M.
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- Characterization of surfacial basic sites of sol gel-prepared alkaline earth fluorides by means of PulseTA
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The CO2 adsorption properties of a series of different sol gel-prepared metal fluorides of the alkaline earth row and aluminium, among them two mixed (doped) metal fluorides was investigated by applying Pulse Thermal Analysis. The alkaline earth flurorides, which exhibit nanoscopic properties, have not only acid, but basic sites as well. For the first time, these basic sites have been characterized by the exothermicity of the first CO2 injection pulse. If the basicity is weak or absent, the alternating injection of water can generate OH groups at the surface of the fluorides. They mostly act as basic sites and allow a stronger differentiation of the basic properties, but the formed OH groups can exhibit an acid character as well. The impact of OH groups can affect a different influence on the sorption properties of the solids: the adsorption ability vs. CO2 can be promoted, suppressed or remain unaffected.
- Feist,Teinz,Manuel, S. Robles,Kemnitz
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- Iridium supported on MgF2-MgO as catalyst for toluene hydrogenation
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The use of mixed magnesium oxo-fluoride support, obtained by one-step sol-gel method, for iridium active phase allowed obtaining new catalysts of high activities in the hydrogenation of toluene. The Ir/MgF2-MgO catalyst was a hundred times more active than that of the iridium system supported on MgF2. The effect of the MgO content and catalyst pre-treatment conditions appeared to have a clear influence on the activity of tested iridium catalysts. The highest activity, expressed as TOF, s- 1, was obtained for the catalyst activated at 500 °C supported on magnesium oxo-fluoride containing 60 mol.% MgO.
- Zieliński, Micha?,Wojciechowska, Maria
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- EFFECT OF GRAIN GROWTH ON HOT-PRESSED OPTICAL MAGNESIUM FLUORIDE CERAMICS.
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An optical MgF//2 ceramic was hot-pressed at 838 to 983 K with 241-MPa pressure. In the early stages of grain growth the mechanical strength was directly proportional to grain size, which appeared to contradict the expectations of the Petch and Knudsen relations. Optical transmission was inversely proportional to grain size, especially in the visible wavelength. This study thus demonstrates a particular case in which increasing grain size promotes higher mechanical strength but lower optical transmission.
- Lin,Hon,Yang
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- Combustion synthesis of silicon carbide assisted by a magnesium plus polytetrafluoroethylene mixture
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In this study, the use of SiC combustion synthesis for immobilization of 14C was considered. Due to the low exothermicity of the reaction between silicon and graphite, a highly exothermic mixture (magnesium and polytetrafluoroethylene) was used
- Ayral,Rouessac,Massoni
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- Synthesis and studies of magnesium hexafluorozirconates MgZrF6 ? nH2O (n = 5, 2, 0)
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Crystalline magnesium hexafluorozirconate MgZrF6 ? 5H 2O isostructural to MnZrF6 ? 5H2O, and having a chain-like structure, was synthesized and studied. According to thermogravimetry, the compound undergoes stepwise dehydration in the temperature range of 50-420°C to give the stable phase MgZrF6 ? 2H 2O and the final product MgZrF6 isostructural to the cubic modification of MZrF6 (M = Cu, Fe). The vibrational spectra of the initial compound and the dehydration products are analyzed and the structures of the compounds are considered.
- Didenko,Gaivoronskaya,Voit,Gerasimenko,Kavun, V. Ya.
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- A novel vapor-phase catalytic synthetic approach for industrial production of 1,1,1,3,3,3-hexafluoroisopropyl methylether
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1,1,1,3,3,3-Hexafluoroisopropylmethyl ether (HFE-356mmz) is an important substitute for chlorofluorocarbons and hydrochlorofluorocarbons due to its zero ozone depletion potential and low global warming potential. However, mass production of HFE-356mmz remains a long-standing challenge. Herein, we applied metal fluorides as catalysts in the methylation of 1,1,1,3,3,3-hexafluoroisopropanol to produce HFE-356mmz for the first time. The catalyst not only improves the synthetic efficiency, but also makes the reaction solvent-free. The pollution-free, recyclable, and continuous synthetic process enables industrial production of HFE-356mmz. To optimize the synthetic efficiency, a series of metal fluorides (AlF3, MgF2, CaF2, SrF2, and BaF2) was used, among which MgF2 exhibited the highest activity. Through careful examination of each metal fluoride, it was found that the activity of the catalyst was determined by co-operative action of the surface acid–base properties and the total amount of surface acid sites. Based on these results, a rational mechanism for the vapor-phase methylation was proposed.
- Li, Wei,Yang, Gang,Lu, Fengniu,Zhang, Xiaoling
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- Upgrading of furfural to biofuel precursors: Via aldol condensation with acetone over magnesium hydroxide fluorides MgF2- x(OH)x
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Wastes from lignocellulosic materials, especially hemicellulose, are extremely promising resources to produce fuels from renewable raw materials. Furfural, resulting from the depolymerization of hemicellulose, is often considered as an extremely interesting platform molecule. Particularly, new biofuels containing molecules with 8 and 13 carbon atoms can be produced from aldol condensation of furfural and acetone followed by a deoxygenation reaction. In this work, several magnesium hydroxide fluorides MgF2-x(OH)x were prepared by a sol-gel method with various F/Mg ratios (0 to 2) at 100 °C. All solid samples were fully characterized by several techniques (nitrogen adsorption-desorption, TEM, IR, XRD and ICP). MgF2-x(OH)x were mainly composed of an intimate mixture of MgF2 and Mg(OH)2-x(OCH3)x and exhibited both acid-base properties and high surface areas. From CO2 adsorption experiments, a basicity scale corresponding to basic sites with moderate strength was established: MgF1.5(OH)0.5 > MgF(OH) ～ MgF1.75(OH)0.25 > MgF0.5(OH)1.5 > Mg(OH)2 ? MgF2. It was proposed that the presence of fluorine allowed stabilization of the basic sites with moderate strength at ambient atmosphere. The aldol condensation of furfural and acetone was carried out under mild reaction conditions (50 °C, Patm) over MgF2-x(OH)x. These catalysts were involved in this reaction without using a classical activation step for basic solid catalysts, which constitutes a major advantage of energy conservation and thus, economic efficiency. The solid with a F/Mg ratio equal to 1.5 (MgF1.5(OH)0.5) exhibited the highest activity, the furanic dimer (1,5-di(furan-2-yl)penta-1,4-dien-3-one) being the main product. A good correlation between the catalytic activity and the basicity scale was highlighted. Based on these results, the nature of active sites was proposed: a combination of a Lewis acid site (coordinatively unsaturated metal site) in the vicinity of a basic site (hydroxyl groups of Mg(OH)2-x(OCH3)x). The effect of the furfural/acetone ratio on the catalytic properties of MgF1.5(OH)0.5 was also investigated.
- Xu, Minrui,Célérier, Stéphane,Comparot, Jean-Dominique,Rousseau, Julie,Corbet, Matthieu,Richard, Frédéric,Clacens, Jean-Marc
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p. 5793 - 5802
(2019/11/05)
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- Polyoxometalate-MgF2 hybrids as heterogeneous solid acid catalysts for efficient biodiesel production
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A series of highly active and stable Keggin heteropolyacid catalysts were prepared through mixing of 12-tungstophosphoric acid (TPA) with magnesium fluoride (MgF2). Among those acidic catalysts, the Mg20F39TPA-1.0 hybrid with moderate acidity (0.96 mmol g-1) and good dispersion of active sites presented pronounced catalytic performance in esterification of oleic acid (up to 95% oleic acid conversion). Particularly, Mg20F39TPA-1.0 was also efficient for the transesterification of Jatropha oil with a high acid value, giving biodiesel in 93% yield. Moreover, the catalyst showed good durability and reusability for at least five consecutive cycles.
- Yang, Kai-Li,Huang, Shan,Pan, Hu,Zhang, Heng,Liu, Xiao-Fang,Yang, Song
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p. 33335 - 33343
(2017/07/12)
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- How does TiF4 affect the decomposition of MgH2 and its complex variants?-An XPS investigation
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Magnesium hydride and its complex variants, i.e. Mg(AlH4)2 and Mg(BH4)2 are known for their high hydrogen capacity. The theoretical capacities of these three are 7.6 wt%, 9.3 wt% and 14.4 wt%, respectively. In spite of having very attractive H2 capacities, their high operating temperature, i.e. more than 300 °C and sluggish kinetics are big issues to be solved before these can be realized for a practical hydrogen storage system. There are several efforts devoted to reduce the working temperature and enhance the sorption kinetics using various additives. Ti-based additives have always been interesting contenders in enhancing the kinetics as well as altering thermodynamics thus reducing the working temperature for various hydrides. Recently, TiF4 has shown superior catalytic activity on the decomposition of Mg(AlH4)2. This motivates us to study its effect on the decomposition of all the above-mentioned Mg-based hydrides. It is observed that the addition of 10 wt% TiF4 to the above materials greatly influences the decomposition temperature. The decomposition temperature for all three reactions is shifted to the lower temperature side. The oxidation state of the catalyst surface has been investigated using the XPS technique and then the detailed mechanism associated with this improvement is proposed herein.
- Jain, Ankur,Agarwal, Shivani,Kumar, Sanjay,Yamaguchi, Shotaro,Miyaoka, Hiroki,Kojima, Yoshitsugu,Ichikawa, Takayuki
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p. 15543 - 15551
(2017/08/10)
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- A silicon tetrafluoride, methanol and magnesium and silicate preparing method of magnesium fluoride
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The invention relates to the technical field of chemical industry and in particular relates to a method for preparing methyl silicate and magnesium fluoride by utilizing reactions of silicon tetrafluoride, methanol and magnesium. The method comprises the following steps of: a. adding methanol and magnesium powder to a reaction kettle; b. raising the temperature of the reaction system to a preset temperature to react; c. after reaction is completed, cooling the reaction system, adding prepared methanol solution of silicon tetrafluoride to the reaction kettle until the reaction system is neutral; d. separating solid from liquid through filtration; e. washing the solid obtained in step d with methanol and drying the washed solid to obtain the target product magnesium fluoride; and f. distilling the filtrate obtained in step d to remove methanol, thus obtaining methyl silicate with high boiling point. The method can be used for producing by-product silicon tetrafluoride by efficiently utilizing phosphate fertilizers.
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Paragraph 0019; 0020
(2017/01/05)
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- Optimisation of a sol-gel synthesis route for the preparation of MgF2 particles for a large scale coating process
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A synthesis route for the preparation of optically transparent magnesium fluoride sols using magnesium acetate tetrahydrate as precursor is described. The obtained magnesium fluoride sols are stable for several months and can be applied for antireflective coatings on glass substrates. Reaction parameters in the course of sol synthesis are described in detail. Thus, properties of the precursor materials play a crucial role in the formation of the desired magnesium fluoride nanoparticles, this is drying the precursor has to be performed under defined mild conditions, re-solvation of the dried precursor has to be avoided and addition of water to the final sol-system has to be controlled strictly. Important properties of the magnesium fluoride sols like viscosity, particle size distribution, and structural information are presented as well.
- Scheurell,Noack,K?nig,Hegmann,Jahn,Hofmann,L?bmann,Lintner,Garcia-Juan,Eicher,Kemnitz
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p. 19501 - 19508
(2015/11/27)
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- The study of an alcoholysis reaction of silicon tetrafluoride with alcohols and magnesium to prepare tetraalkoxysilanes and magnesium fluoride
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An efficient alcoholysis reaction of silicon tetrafluoride with alcohols in the presence of magnesium can directly prepare tetraalkoxysilane and magnesium fluoride. The reaction can afford tetraethoxysilane, tetramethoxysilane, and magnesium fluoride in good yields with the aid of a catalytic amount of iodine.
- Zhang, Zongfan,Huang, Zhong,Tian, Qiang,Li, Yuye,Li, Xia,Liang, Xuesong,Du, Lusha
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p. 567 - 573
(2015/05/20)
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- Sol-gel synthesis and characterisation of nanoscopic FeF3-MgF2 heterogeneous catalysts with bi-acidic properties
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Nanoscopic metal fluorides with surface hydroxy groups are of broad interest in heterogeneous catalysis. With both Lewis and Bronsted acid sites on the surface, these catalysts can be applied to a wide range of reactions. Having previously synthesised AlF3- and MgF2-based catalysts, we report a new transition metal fluoride with bi-acidity. A pre-dehydration procedure was developed to introduce hydroxy groups to a Lewis acid, FeF3. Subsequently, ternary nanoscopic FeF3-MgF2 with enhanced porosity was prepared through a one-step fluorination. The interaction between MgF2 and FeF3 was elucidated. Surface characterisation revealed a remarkable increase in the surface area of FeF3-MgF2 compared with FeF3. More importantly, medium-strong Lewis and Bronsted acid sites were detected on the FeF3-MgF2 surface. In line with its bi-acidity, FeF3-MgF2 was highly active in the model reaction, the isomerisation of citronellal to isopulegol. Finally, we discuss how the porosity and surface acidity jointly determine the activity of FeF3-MgF2. Our study demonstrates the feasibility of ternary FeF3-MgF2 and opens new possibilities to synthesise bi-acidic fluoride catalysts.
- Guo, Ying,Gaczynski, Piotr,Becker, Klaus-Dieter,Kemnitz, Erhard
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p. 2223 - 2232
(2013/08/23)
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- ANTIBIOFILM COATING CONTAINING FLUORIDE SALT NANOPARTICLES
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An aspect of embodiments of the invention relates to antibacterial and anti-biofilm coatings comprising nanoparticles of a fluoride salt selected from the group consisting of MgF2, SnF2, SnF4 and YF3. The nano-particles may have an average particle size greater than or equal to about 1 nanometer (nm) and less than about 500 nm. An aspect of an embodiment of the invention relates to methods of producing the nano-particles by sonication. In an embodiment of the invention, the coating is manufactured using sonication. In embodiments of the invention, the coating is coated on a temperature sensitive substrate. Further aspects of embodiments of the invention relate to nanoparticulate fluoride salts selected from the group consisting of MgF2, SnF2, SnF4 and YF3 with enhanced physical properties, enhanced biological qualities and/or enhanced purity in comparison to previously described particles.
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Paragraph 00024-00029
(2013/03/26)
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- Method for the manufacture of magnesium fluoride sols and magnesium fluoride sol
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A method is described to produce magnesium fluoride sols in an alcohol, especially in ethanol, with improved properties by the reaction of magnesium acetate or magnesium alcoholate with HF in C1 to C3 aliphatic alcohol or C2 or C3 aliphatic diol, preferably ethanol, in the presence of a specific amount of water. Improved magnesium fluoride sols are also described. The sols are useful to provide coatings of MgF2 on solar cells. The invention also provides solutions containing magnesium acetate, specific organic solvents, carbon dioxide and optionally water.
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- The catalytic and physico-chemical properties of Ni/MgF2-MgO catalysts
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The MgF2-MgO system of different quantitative compositions was tested as a potential support for nickel catalysts to be used for hydrogenation of toluene. The catalytic performance of the system was studied as a function of the MgF2/
- Zieliński, Micha?
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- Structural studies on Ba2SrMg4F14 and Ba2MM′Mg4F14 (M= Ca, Sr, Ba)
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The new barium strontium magnesium fluoride Ba2SrMg 4F14 has been prepared as an almost single-phase colorless powder by precipitating amorphous precursors and heating them at 650° C. The compound crystallizes in the space group P42/mnm (no. 136) with a = 12.45514(4), c = 7.46092(3) A, V = 1157.42(1) A3 and Z = 4. It is isostructural with the previously known Ca analog, Ba2.2Ca0.8Mg4F14. The structure is built up from a channel-forming network of tetrahedral (MgF6)4 units linked by bridging fluorine atoms. The channels contain the Ba 2+ ions (CN = 11) and Sr2+ ions (CN = 8, CaF2 type-related environment). Solid solutions with composition Ba 2(Sr1?xCax)Mg4F14 with x = 0.13(1), 0.36(1) and 0.51(1) as well as Ba2(Sr0.83(1) Ba0.17(1))Mg4F14 were synthesized and characterized by powder X-ray diffraction.
- Kubel, Frank,Wandl, Nicole,Pantazi, Mariana
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- Highly selective metal fluoride catalysts for the dehydrohalogenation of 3-chloro-1,1,1,3-tetrafluorobutane
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For the first time, dehydrochlorination and dehydrofluorination reactions are studied on the same substrate, 3-chloro-1,1,1,3-tetrafluorobutane, employing nanoscopic metal fluorides AlF3, MgF2, CaF2, SrF2, and BaF2 as catalysts that are prepared according the fluorolytic sol-gel synthesis. AlF3 is exclusively selective toward dehydrofluorination, whereas BaF2 is 100% selective toward dehydrochlorination. The acid-base character of the catalysts is investigated and, as a result, mechanistic proposals for the dehydrofluorination and the dehydrochlorination are given. Thus, at high conversion level, selective catalysts for both dehydrofluorination and dehydrochlorination on the same substrate have been developed.
- Teinz, Katharina,Wuttke, Stefan,Boerno, Fabian,Eicher, Johannes,Kemnitz, Erhard
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p. 175 - 182
(2011/10/18)
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- Formation of unsaturated C3 hydrocarbons by the protolysis of magnesium sesquicarbide with ammonium halides
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The protolysis of magnesium sesquicarbide, Mg2C3, with inorganic acids provides an interesting alternative to the more common hydrolysis of ionic carbides for obtaining their respective hydrocarbons. In particular, protolysis reactio
- Disch, Sabrina,Cheetham, Anthony K.,Ruschewitz, Uwe
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p. 969 - 973
(2008/10/09)
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- Interaction, composition, and optical properties of the MgF 2(MgO)-EuF3 system
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The interaction between MgO and EuF3 resulting in the formation of magnesium fluoride and europium(III) oxyfluorides of variable composition are investigated. A substantial difference between the diffuse reflection spectra of the fluoride phase and oxyfluoride phases of europium(III) is found, specifically, an intense band peaked at 260-270 nm appears in the latter. The effect of silicon and high vacuum as reducers on the systems containing the oxide phase is investigated. For these phases, europium(II) compounds are found, which is confirmed by X-ray powder diffraction analysis and diffuse reflection and luminescence spectroscopy. The character of thermogravimetric curves for the MgF2-EuF3-Si and MgO-EuF3-Si systems is fundamentally different, which allows us to propose a new method for estimating the MgO content in MgF2. Nauka/Interperiodica 2007.
- Timukhin,Zinchenko,Eremin,Kovalevskaya,Topilova
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p. 927 - 932
(2008/10/09)
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- Chemical interaction between LiF and MgAl2O4 spinel during sintering
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Reactions between LiF and MgAl2O4 at temperatures up to 1500°C are examined with a variety of tools, including differential scanning calorimetry, thermo-gravimetric analysis, X-ray diffraction, and scanning electron microscopy. LiAlO2 and MgF2 are found to be the active reaction products at these temperatures. A transient liquid phase comprising MgF2 and LiF forms at intermediate temperatures, but then is consumed at higher temperatures during the reformation of MgAl2O4. If processed as an uncompacted powder mixture, all of the initial LiF in the system eventually vaporizes at temperatures exceeding 1300°C. A new reaction sequence relevant to the densification of LiF-doped MgAl2O4 spinel is proposed.
- Rozenburg,Reimanis,Kleebe,Cook, Ron L.
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p. 2038 - 2042
(2008/10/09)
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- Method for the preparation of high surface area metal fluorides
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The present invention is related to a method for preparing an amorphous metal fluoride of the formula MX+FX-δ comprising the steps of a) providing a precursor, whereby the precursor comprises a structure having a formula of Mx+F(x-δ)-yBy; and b) reacting the precursor with a fluorinating agent generating the amorphous metal flouride having a formula of Mx+Fx-δ, whereby M is selected from the group comprising metals of the second, third and fourth main group and any subgroup of the periodic table, B is a coordinately bound group; x is any integer of 2 or 3; y is any integer between 1 and 3; δ is 0 to 0.1; and x?δ>y.
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Page/Page column 6
(2010/10/20)
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- Improving H-sorption in MgH2 powders by addition of nanoparticles of transition metal fluoride catalysts and mechanical alloying
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Mechanical alloying of nanograined MgH2 with addition of small amounts of FeF3 can produce, via a fluoride transfer reaction, a nanocomposite powder containing both the transition metal and fluorine as catalysts. The solid-state phase transformations and microstructural changes during milling and/or during heating were studied by X-ray diffraction during in-situ heating, transmission electron microscopy, differential scanning calorimetry and magnetization measurements. The fluoride transfer reaction occurs partially during milling and can be completed during the first heating cycle. An improved H-desorption behavior was observed in such nanocomposite powder in comparison with the best reported values for MgH2-based composites.
- De Castro,Yavari,Lemoulec,Ishikawa,Botta F
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p. 270 - 274
(2008/10/09)
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- Decomposition of dichlorodifluoromethane with simultaneous halogen fixation by vanadium oxide supported on magnesium oxide
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Dichlorodifluoromethane (CCl2F2, 1% in He) decomposition with simultaneous halogen fixation by vanadium oxide supported on magnesium oxide was studied at 723 K in a flow apparatus. The pretreatment condition and vanadium loading of supported vanadium oxide samples affected the CCl2F2 decomposition efficiency. Through characterization studies (XRD, IR, Raman, and XPS) and reference experiments, Mg 3(VO4)2 was revealed to be the active species to initiate CCl2F2 decomposition, leading to MgF 2, MgCl2, and CO2 formation. The model experiments also suggested a detailed mechanism that VOCl3 was formed from Mg3(VO4)2 by a reaction with CCl 2F2 or the major intermediate compound CCl4, and that VOCl3 reacted with MgO to regenerate Mg3(VO 4)2 and to promote chlorine fixation as MgCl2.
- Tamai, Tsukasa,Inazu, Koji,Aika, Ken-Ichi
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p. 1565 - 1574
(2007/10/03)
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- Enhanced dichlorodifluoromethane decomposition with selective fluorine absorption by acidic fluoriated magnesinm oxide
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CCl2F2 decomposition with simultaneous halogen absorption by partially fluorinated MgO (MgF2-MgO) was studied, focusing on the effects of the acidity of the surface. CCl2F 2 decomposition by MgF2-MgO was greatly promoted by fluorination of MgO at 10 mol% or higher. CCl2F2 decomposition was not a catalytic process over MgF2-MgO but basically a selective fluorine absorption reaction with MgO to form MgF2. Chlorine was released in the form of CCl4 regardless of reaction temperature and degree of fluorination of MgO due to low reactivity to CCl 4. NH3-TPD and pyridine adsorption experiments were carried out to characterize the acid sites on MgF2-MgO samples. The amount of acid sites became maximum for 10% MgF2-MgO and the strength of acid sites increased as fluorination proceeded. CCl2F2 decomposition was revealed to be initiated by Lewis acid sites on MgF 2-MgO formed by CCl2F2 decomposition as well as by fluorination with hydrofluoric acid aqueous solution. Thus, formation of the Lewis acid sites was considered to be the key step for efficient CCl 2F2 decomposition with selective fluorine absorption.
- Tamai, Tsukasa,Inazu, Koji,Aika, Ken-Ichi
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p. 1239 - 1247
(2007/10/03)
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- Structure and magnetism of fluorides Cs2MCu3F10 (M = Mg, Mn, Co, Ni), variants of the CsCu2F5 type
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X-ray structure determinations of single crystals showed that compounds Cs2MCu3F10 crystallize with Z = 2 in space group P21/n (No.14) (M = Mn) of the CsCu2F5 type resp. in its supergroup I2/m (No. 12) (M = Mg, Co, Ni). Cs2MgCu3F10: a = 714.9(1), b = 736.8(1), c = 940.4(1)pm, b = 96.29(1)°, (Mg-F: 199.2pm); Cs2MnCu3F10: a = 725.1(1), b = 742.7(1), c = 951.0(2) pm, b = 97.28(3)°, (Mn-F: 209.1 pm); Cs2CoCu3F10: a = 717.8(3), b = 739.1(2), c = 939.4(4)pm, b = 97.49(2)°, (Co-F: 203.1pm); Cs2NiCu3F10: a = 716.3(1), b = 737.7(1), c = 938.2(2) pm, b = 97.09(1)°, (Ni-F: 201.0 pm). As determined directly for the Mg compound and generally concluded from the average distances M-F noted, M substitution concerns mainly the octahedrally coordinated position of the CsCu2F5 structure, the distortion of which is very much reduced thereby. Within the remaining [CuF4] and [CuF5] coordinations, in contrast to CsCu2F5, one F ligand is disordered, in case of the Mn compound the pyramidally coordinated Cu atom, too. The magnetic properties are complex and point to frustration and spin glass effects. Only at the diamagnetically substituted variants with M = Mg, Zn no Neel point appears, which is reached at 27, 23, 36 and 55 K for M = Mn, Co, Ni and Cu, resp.. At lower temperatures ferri- resp. weak ferromagnetism and hysteresis is observed.
- Kaiser,Dahlke,Babel
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p. 993 - 1000
(2008/10/08)
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- Synthesis and crystal structure analysis of NaSrMg2F7, a fully fluorinated compound of the pyrochlore family
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During our research on alkali-fluorides, the compound NaSrMg2F7 has been prepared by a precipitation reaction of Sr2+, Mg2+ and Na+ with F- for the first time. The powder crystallizes as a single phase in the form of spherical agglomerates ～0.25 μm in diameter. The compound crystallizes in the space group Fd3m (Nr. 227) with lattice parameter a = 10.4379(4) A?. Structural analysis by the Rietveld method was done from X-ray diffraction data. In agreement with the structure analysis, spectroscopical investigations confirm the presence of two coupled fluoride ions. The crystal structure corresponds to the pyrochlore structure type A2B2X7 with 50% occupation of Sr2+ or Na+ at the A site. WILEY-VCH Verlag GmbH, 2001.
- Kubel, Frank,Dundjerski, Barbara
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p. 1589 - 1592
(2008/10/08)
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- The crystal structure of Kx(MgxIn1-x)F3 (x = 0.38): A new magnéli-bronze type fluoride
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Kx(MgxIn1-x)F3 (x = 0.38) is monoclinic, pseudo tetragonal: a = 12.781(2) ?, b = 12.787(2) ?, c = 7.930(1) ?, β = 90,00(1)°, Z = 20. The crystal structure was solved in the space group P21/a (No. 14), subgroup of the tetragonal space group P4/mbm (No. 127), from X-ray single crystal data using 4302 unique reflections (1770 with Fo/σ(Fo) > 4). The final observed R factor is 0.053. Kx(MgxIn1-x)F3 has the Magnéli-bronze structural type, which consists in a tridimensional framework of mixed [(MgxIn1-x)F6] octahedra linked together by corners. The potassium ions are mainly located in large almost fully occupied 15-coordinated sites and in practically empty 12-coordinated cavities.
- Caramanian, Armen,Dupont, Nathalie,Gredin, Patrick,De Kozak, Ariel
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p. 933 - 938
(2008/10/08)
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- OPTIMIZATION OF PHYSICOCHEMICAL PROPERTIES AND CONDITIONS OF PREPARATION OF CATALYSTS USED FOR THE SYNTHESIS OF FLUORINATED ORGANIC COMPOUNDS
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The physicochemical properties of magnesium fluoride and chromium-magnesium fluoride catalyst, and their activities in dehydrochlorination and fluorination of chlorinated aliphatic hydrocarbons have been studied as functions of preparation conditions.The optimal characteristics of the catalysts (Ssp, VΣ, Vmi, Vma, P) with respect to dehydrochlorination of tetrachloropropane and fluorination of trifluorotrichloroethane have been found.The dependence of the activities of MgF2 and CrF3/MgF2 on their porous structure has been revealed.The optimal technological parameters have been determined, which ensure preparation of magnesium fluoride and chromium-magnesium fluoride catalysts with required physicochemical properties.
- Kramerova, G. E.,Dul'tseva, Z. A.,Yurchenko, E. N.
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- INTERACTION OF Mg(II) CATION WITH SOLUTIONS OF HEXAFLUOROSILICIC ACID AND HEXAFLUOROSILICATE ANIONS
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In the production of wet-process phosphoric acid from magnesium carbonate-containing phosphorites interactions between the magnesium cations and fluorine-containing anions take place in the process pulp.Using model neutralization of solutions of hexafluorosilicic acid of various concentrations with basic magnesium carbonate as an example, it has been demonstrated that the composition of solid-phase products depends upon the acidity of the medium: at pH 0.86 MgSiF6*6H2O is formed, whereas at pH 1.70 magnesium fluoride precipitates.
- Lapinskii, A. V.,Suprunchuk, V. I.,Astrelin, I. M.
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p. 1288 - 1290
(2007/10/02)
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- INVESTIGATION OF THE REACTION PRODUCTS OF MAGNESIUM CARBONATE WITH HYDROFLUORIC ACID SOLUTIONS.
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It was established that upon the reaction of magnesium carbonate with hydrofluoric acid solutions partially hydrolyzed magnesium fluorides are formed. A scheme of the stepwise decomposition of the latter upon thermal treatment is given.
- Shapoval,Didash,Seredenko,Lutsenko
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