Investigation of structures of PEO‐MgCl2 based solid polymer electrolytes

The crystallinity of polyelectrolytes has long been known to affect their ionic conductivity, but the effects of water of hydration on polyelectrolyte structure are not commonly studied. Here, polymer complexes consisting of poly(ethylene oxide) (PEO) with magnesium chloride (anhydrous MgCl₂, MgCl₂·4H₂O, and MgCl₂·6H₂O, respectively) have been prepared by a mixed‐solvent method. Fourier transform‐infrared measurements indicate each magnesium chloride salt can coordinate with PEO to form a complex. The structures of (PEO)_xMgCl₂·4H₂O and (PEO)_xMgCl₂·6H₂O complexes are similar, whilst the structure of (PEO)_xMgCl₂ complex is different to both. Wide angle X‐ray diffraction studies indicate in each polymer complex system the crystallization of PEO is depressed by the interaction of magnesium cation with the ether oxygen of PEO. PEO in (PEO)_xMgCl₂ and (PEO)_xMgCl₂·4H₂O are shown to be amorphous, but in (PEO)_xMgCl₂·6H₂O it is crystalline. Polar optical microscopy images indicate in each PEO/magnesium chloride system the crystalline morphology clearly changes with the increase of magnesium salt content. The reason for the formation of the spherulites with special morphology are the strong interaction between magnesium cation and ether oxygen of PEO, and the different evaporation rates of ethanol and chloroform in mixed solvent. A better understanding of the effects of hydration on polyelectrolyte crystallinity can help in improving their use in a variety of applications. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2013, 51, 1162–1174     

Catalyseurs Ziegler-Natta supportés sur MgCl2 pour la polymérisation stéréorégulée du propène. III. Systèmes catalytiques à hautes performances comprenant un solide ternaire: MgCl2, ester aromatique,TiCl4

An examination of the precatalyst which contains three compounds (MgCl₂–TiCl₄-aromatic ester) uncovered numberous properties that apparently are common to all precatalysts and have already been observed in the simpler systems: a continous decrease in the polymerization rate during polymerization, characterized by a deactivation index that does not depend on the precatalyst but only on the cocatalyst; isotacTiClty control by the [AI]/[aromatic ester] ratio in the cocatalytic solution; and fast and reversible control of kinetics and tacTiClty by the same ratio. The precatalyst prepared by impregnation of the aromatic ester in MgCl₂ or MgCl₂–TiCl₄ presents moderate or no improvement when compared with the simpler MgCl₂–TiCl₄ catalysts. The yellow precatalyst prepared by milling MgCl₂ with the aromatic ester and impregnating with TiCl₄ are the only products that provide high activity and isotactic index above 95% simultaneously, as revealed by the patent literature. Interpretation of the role played by the electron donor, based on infrared studies, are proposed: in the precatalyst it controls fixation of TiCl₄ on MgCl₂; in the cocatalytic solution it regulates the isospecificity of the active site by contact with the alkylaluminium-aromatic ester complex and slows polymerization. Free electron donor gradually poisons the active centers.     

Electrodeposition of magnesium–lithium–dysprosium ternary alloys with controlled components from dysprosium oxide assisted by magnesium chloride in molten chlorides

In the work, Gibbs energy showed that MgCl₂ can chloridize Dy₂O₃ and release Dy(III) ions in the LiCl–KCl–MgCl₂–Dy₂O₃ melts. Dy(III) ions were observed by cyclic voltammetry, square wave voltammetry in melts. X-ray diffraction (XRD) pattern of melts indicated that Dy₂O₃ was chlorinated by MgCl₂ and formed DyCl₃. XRD pattern of non-dissolved residue, which was left after the melts were washed with water to remove the soluble salt, showed that the new compounds (i.e., DyOCl, MgO, and Dy(OH)₃) were produced. The concentration of Dy(III) reached a maximum when the concentration of Mg(II) ions exceeded 8?×?10^?4 mol cm^?3 in melts by inductive coupled plasma atomic emission spectrometer analyses of melts. Galvanostatic electrolysis was conducted to extract Dy element from LiCl–KCl–MgCl₂–Dy₂O₃ melts by forming Mg–Li–Dy alloys. The components of Dy and Li in alloys were controlled within a small range by the concentration of MgCl₂ in melts, current density, and additions of Dy₂O₃. XRD patterns of alloys indicated that Mg₃Dy phase was formed. Scanning electron microscope images with energy-dispersive X-ray spectroscopy showed that Dy elements were mainly distributed in the grain boundary. Grain size was refined, due to a more content of Dy elements in alloys by optical microscopy images.     

Propylene polymerization with catalysts containing divalent titanium

The behavior in propylene polymerization of divalent titanium compounds of type [η⁶-areneTiAl₂Cl₈], both as such and supported on activated MgCl₂, has been studied and compared to that of the simple catalyst MgCl₂/TiCl₄. Triethylaluminium was used as cocatalyst. The Ti–arene complexes were active both in the presence and in the absence of hydrogen, in contrast to earlier reports that divalent titanium species are active for ethylene but not for propylene polymerization. ¹³C-NMR analysis of low molecular weight polymer fractions indicated that the hydrogen activation effect observed for the MgCl₂-supported catalysts should be ascribed to reactivation of 2,1-inserted (“dormant”) sites via chain transfer, rather than to (re)generation of active trivalent Ti via oxidative addition of hydrogen to divalent species. Decay in activity during polymerization was observed with both catalysts, indicating that for MgCl₂/TiCl₄ catalysts decay is not necessarily due to overreduction of Ti to the divalent state during polymerization. In ethylene polymerization both catalysts exhibited an acceleration rather than a decay profile. It is suggested that the observed decay in activity during propylene polymerization may be due to the formation of clustered species that are too hindered for propylene but that allow ethylene polymerization. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2645–2652, 1997     

Experimental and calculated vibrational spectra and structure of Ziegler-Natta catalyst precursor: 50/1 comilled MgCl2-TiCl4

The vibrational Infrared and Raman Spectra of a MgCl₂-TiCl₄ Ziegler-Natta catalyst precursor with a 50/1 MgCl₂/TiCl₄ ratio have been recorded. The Raman spectrum of this catalyst precursor, in the range 50-500 cm⁻¹, shows clear scattering lines which can be assigned to the complex MgCl₂-TiCl₄, well separated from those of the initial species. Analogous, but less clear signals can be found in the infrared spectrum. Vibrational symmetry analysis and quantum chemical calculations of suitable models of MgCl₂-TiCl₄ complex have been made for the interpretation of the experimentally recorded spectra. The observed spectroscopic signals can be explained in terms of the existence of only one type of MgCl₂-TiCl₄ complex where the TiCl₄ molecules are complexed on the MgCl₂ along the (110) lateral cuts in a local C_2v symmetry with the Ti atoms in an octahedral coordination.     

Phase Diagram of the Quaternary System KCl–MgCl<Subscript>2</Subscript>–NH<Subscript>4</Subscript>Cl–H<Subscript>2</Subscript>O at <Emphasis Type="Italic">t</Emphasis> = 60.00 °C and Their Application

Based on the requirement for the comprehensive exploitation and utilization of the salt lake resources magnesium chloride and potassium chloride, a new technology to produce KCl and ammonium carnallite (NH₄Cl·MgCl₂·6H₂O) by using NH₄Cl as salting-out agent to separate carnallite is proposed. The solubilities of quaternary system KCl–MgCl₂–NH₄Cl–H₂O were measured by the isothermal method at t = 60.00 °C and the corresponding phase diagram was plotted and analyzed. The analysis of this phase diagram shows that there are seven saturation points and eight regions of crystallization. These eight regions of crystallization represent salts corresponding to KCl, NH₄Cl, MgCl₂·6H₂O, (K_1?n (NH₄) _n )Cl, ((NH₄) _n K_1?n )Cl, (K_1?n (NH₄) _n )Cl·MgCl₂·6H₂O, KCl·MgCl₂·6H₂O and NH₄Cl·MgCl₂·6H₂O. According to the phase diagram analysis and calculations, ammonium carnallite (NH₄Cl·MgCl₂·6H₂O) and KCl can be obtained using carnallite as raw materials and ammonium chloride as salting-out agent at t = 60.00 °C. The new technology shows the advantages of being easy to operate and having low energy consumption. The research on this quaternary phase diagram is the foundation for reasonable development of carnallite resources and comprehensive utilization of the salt lake brines.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. XXIV. Darstellung und Eigenschaften von Tetrabenzylmolybdän und -uran

Contributions to the Chemistry of Transition Metal Alkyl Compounds. XXIV. Preparation and Properties of Tetrabenzyl Molybdenum and Tetrabenzyl Uranium Tetrabenzyl molybdenum, (C₆H₅CH₂)₄Mo, can be obtained by the reaction of MoCl₄ · 2 THF with dibenzyl magnesium. The compound forms darkbrown crystals, which are stable at room temperature. The analogous reaction of UCl₄ · 3 THF with dibenzyl magnesium yields a reddish brown complex of tetrabenzyl uranium of the formula (C₆H₅CH₂)₄U · MgCl₂. The synthesized compounds are characterized more in detail.     

Comparative characterization of MgCl2/ethyl benzoate/TiCl4 and MgCl2/2,2,6,6 tetramethylpiperidine/TiCl4 Ziegler-Natta precatalysts

In this article we present the results of the preparation and characterization of two Ziegler–Natta precatalysts: MgCl₂/Ethyl benzoate (EB)/TiCl₄ and MgCl₂/2,2,6,6 tetramethylpiperidine (TMPiP)/TiCl₄ by means of FTIR, X-ray diffraction, SEM, BET surface area measurements, and other techniques applied at different steps of their preparation procedures. The precatalysts were prepared by impregnating with TiCl₄ a given amount of MgCl₂, which was previously ball-milled with the electron donor chosen. Prior to impregnation, the ball-milled material presented different surface compounds depending on the electron donor used: [(MgCl₂)₂] · 2EB, MgCl₂ · EB, or a salt of the amine. The solid milled with EB is more homogeneous than the one milled with the TMPiP. Titanium is better retained in the solid milled with EB. This precatalyst has better morphological properties and larger BET surface area. By means of FTIR, we found evidences that an adequate surface structure for the formation of stereospecific sites in MgCl₂/TMPiP/TiCl₄ was formed. © 1994 John Wiley & Sons, Inc.     

Interference of salts on the determination of lead by electrothermal atomic absorption spectrometry. Ion chromatographic study

The influence of various salts on the atomization signal of lead has been examined by using a transverse heated atomic absorption spectrometer. To get more information about interference mechanisms, volatilization of salts has been studied by ion chromatographic analysis of the residue left on the furnace after drying or charring. The use of a Pd/Mg chemical modifier in these model solutions has also been examined. In 0.1 M chloride medium, NaCl, MgCl₂ and CaCl₂ do not interfere significantly. However, their different behaviour in the furnace, and particularly hydrolysis of MgCl₂ influence greatly the charring curves of Pb. The use of a Pd/Mg modifier appears interesting only in the case of NaCl. Indeed, Pd stabilizes Pb sufficiently to permit the removal of NaCl by charring. In the case of MgCl₂, Pb is not sufficiently stabilized to remove chloride through hydrolysis of MgCl₂ or volatilization of MgCl₂. In the presence of CaCl₂, the Pb signal is delayed and coincides with the background absorption signal of CaCl₂; the stabilization effect is not sufficient to eliminate CaCl₂ by charring before atomization. At 0.1 M nitrate concentration, the presence of NaNO₃, Mg(NO₃)₂, and particularly Ca(NO₃)₂, greatly modifies the atomization signal shape of Pb. Pb is more stabilized in nitrate medium, but losses are observed at the decomposition step of nitrate salts. In this medium, the stabilization effect of Pd leads to a single peak signal and permits elimination of nitrate decomposition products before atomization. Interference effects are more important in the presence of 0.1 M sulphate salts and increase with the acidity of the medium. Na₂SO₄, which is reduced to Na₂S on the graphite, does not interfere significantly. However, the decomposition products of MgSO₄ and CaSO₄ induce an important interference effect on the determination of Pb which is stabilized in the furnace. In the case of Na₂SO₄, the use of the Pd/Mg modifier delays the atomization signal which coincides with the background absorption signal, leading to an important interference effect which cannot be eliminated by charring. In the presence of MgSO₄ and CaSO₄, the stabilizing effect of Pd permits the elimination of decomposition products of sulphate salts before atomization and suppresses the chemical interference effect.     

The determination of the complex refractive indices of some concentrated aqueous salt solutions at submillimetre wavelengths

Recent developments in far infrared laser spectrometry and dispersive Fourier transform spectrometry have allowed the full spectral variation of both parts of the complex refractive indices of some aqueous salt solutions in the spectral region 25–450 cm^?1 to be determined. The salts studied were LiCl, LiClO₄, NaCl, NaClO₄, NaI, KCl, KBr, KI, KF, MgCl₂, Mg(ClO₄) and Bu₄NBr (tetrabutylammonium bromide). The results show that in the presence of some electrolytes the optical constants of the solution differ significantly from those of pure water, and that in localised spectral regions the absorption can be many times less than that of pure water.     

Sensitive spectrophotometric determination of molybdenum(VI) with Pyrogallol Red and cetyltrimethylammonium ions

Pyrogallol red in the presence of cetyltrimethylammonium bromide is proposed for the spectrophotometric determination of microgram amounts of molybdenum. The sensitivity of the color reaction between molybdenum and Pyrogallol Red has been greatly increased by the sensitizing action of cetyltrimethylammonium bromide (?_{600 nm} = 90,000). Beer's law is obeyed over the range 0.1–0.4 μg/ml of molybdenum. The composition of the complex may therefore be formulated as Mo:PR:CTA = 1:2:4.     

Synthesis and Crystal Structure of a Tetranuclear Molybdenum(II) Silylamido Cluster

Treatment of molybdenum(II) chloride with the difunctional silylamide Li₂Me₂Si(NPh)₂ led to the formation of the tetranuclear cluster compound [Mo₄{Me₂Si(NPh)₂}₄]. According to the X-ray crystal structure determination, the central core of the cluster consists of four molybdenum atoms in a nearly rectangular arrangement. There are two μ₄-κ-N,N,N',N'-Me₂Si(NPh)₂^2– ligands capping the Mo₄ rectangle and two μ₂-Me₂Si(NPh)₂^2– ligands located at opposite edges. The alternating Mo–Mo distances of 218.1(1) and 279.5(1) pm indicate the presence of a cyclobutadiyne type cluster with alternating Mo–Mo triple and single bonds.     

Synthesis of molybdenum disulfide particles by aerosol-assisted chemical vapor deposition

It was shown that dimethylformamide can be, in principle, used as a solvent of ammonium thiomolybdate for obtaining molybdenum disulfide particles by the aerosol-assisted chemical vapor deposition method. IR Fourier spectroscopy was used to examine (NH₄)₂MoS₄–C₃H₇NO liquid solutions and the thermal stability of dimethylformamide and ammonium thiomolybdate vapors. It was demonstrated that pyrolysis at temperatures of 700–900°C yields spherical molybdenum disulfide microparticles with average diameters in the range 0.6–1 µm and “onion” structure.     

Magnesium chloride-supported,high-mileage catalysts for olefin polymerization. V. BET,porosimetry, and x-ray diffraction studies

The physical state of the material obtained during the various stages of preparation of a typical MgCl₂-supported, high-mileage propylene polymerization catalyst was studied by BET, mercury porosimetry, and x-ray diffraction techniques. The starting MgCl₂ and the substance after HCl treatment have negligible BET surface areas. Mercury porosimetry showed that they have large pores with radii > 200 nm which are probably crevices between MgCl₂ crystallites. The most pronounced physical changes occur during dry porcelain ball milling in the presence of ethyl benzoate. After 60 h or more of ball milling the material had a 5.1–7.3 m² g^?1 BET surface area, twice the pore surface area, and a smaller pore radius than before ball milling and a large reduction in crystallite sizes to almost ultimate dimensions. The crystallites were probably held together by complexation with ethyl benzoate in the form of large agglomerates. Subsequent reactions with p-cresol and triethyl aluminum had minor effects in further reduction of the MgCl² crystallite size but efficiently brokeup the agglomerates. The final refluxing with TiCl₄ increased the BET surface area to 110–150 m² g^?1 but may have increased the crystallite size somewhat due to cocrystallization of TiCl₃ and AlCl₃ with MgCl₂. There may have been only 8–10 crystallites in each catalyst particle. The surface structure of the catalyst resembled those of the classical Ziegler-Natta γ-TiCl₃·0.33 AlCl₃ catalyst.     

Selective extraction of gadolinium from Sm2O3 and Gd2O3 mixtures in a single step assisted by MgCl2 in LiCl–KCl melts

The chloration of MgCl₂ was studied in the LiCl–KCl–MgCl₂–Gd₂O₃–Sm₂O₃ melts. Gd(III) and Sm(III) ions were observed by cyclic voltammetry and square wave voltammetry assisted by MgCl₂ in melts. X-ray diffraction (XRD) patterns of melts indicated Gd₂O₃ and Sm₂O₃ were chlorinated by MgCl₂ and formed GdCl₃ and SmCl₃. XRD patterns of non-dissolved residues, which were left after the melts were washed with water to remove the soluble salt, showed that the new compounds (i.e., GdOCl, SmOCl, MgO, Gd(OH)₃, and Sm(OH)₃) were produced. Potentiostatic electrolysis experiments were performed to extract Gd from Gd₂O₃ and Sm₂O₃ mixtures assisted by MgCl₂. Separation between Gd₂O₃ and Sm₂O₃ was also achieved in a single step with the formation of Mg–Li–Gd alloys. XRD patterns of alloys indicated that Mg₃Gd phase was formed. Scanning electron microscope images with energy dispersive X-ray spectroscopy showed Gd elements were mainly distributed in the grain boundary.     

Amalgamation of ziegler-natta and metallocene catalysts

The MgCl₂ supported half titanocenes and Ti(4, 4, 4-trifluoro-1-phenyl-1, 3-butanedionato)₂Cl₂ catalysts were synthesized and applied to propene polymerization. Without supporting on MgCl₂, those complexes displayed almost no activity even using methylaluminoxane (MAO) as cocatalyst. When supported on MgCl₂, on the other hand, the resulting catalysts could be activated by ordinary alkylaluminums to yield polypropene in fairly high yields. The catalyst isospecificity was markedly improved by the addition of a suitable Lewis base.     

Function of the hydrogen bond in the conversion of α- to β-Mo8O264− ions: Formation and structure of tetra(tributylhydrogenammonium) β-octamolybdate

Complex β-(Bu₃NH)₄Mo₈O₂₆ has been transformed from α-(Bu₄N)₄Mo₈O₂₆ in the presence of o-mercaptophenol (H₂mp) and CuCl₂ in MeOH, and structurally characterized. It can be considered as a dimer [(Bu₃NH)₂Mo₄O₁₃]₂ with a center of symmetry. Each molybdenum atom is in a severely distorted octahedral environment. Two types of H bond between the cations and the anions have been found in the complex: N–H⋯O and C–H⋯O, which may play important roles in the α→β transformation.     

Magnesium chloride supported high-mileage catalysts for olefin polymerization. I. Chemical composition and oxidation states of titanium

The chemical composition of a MgCl₂-supported, high-mileage catalyst has been determined at every stage of its preparation. Ball milling of MgCl₂ with ethyl benzoate (EB) resulted in the incorporation of 95% of the EB present to give MgCl₂·EB_0.15. A mild reaction with a half-mole equivalent of p-cresol (PC) at 50°C for 1 h resulted in near quantitative retention of p-cresol by the support. The composition is now approximately MgCl₂·EB_0.15P?_0.5. Addition of an amount of AlEt₃ corresponding to half-mole equivalent of p-cresol liberated one mole of ethane per mole of p-cresol, thus signaling quantitative reaction between the two components. The support contains on the average one ethyl group per Al. Further reaction with TiCl₄ resulted in the incorporation of titanium of approximately 8, 38, and 54% in the oxidation states of +2, +3, and +4, respectively. The ratio of Al to Ti in the catalyst lies in the range of 0.5–1.0. Only 19% of all the Ti⁺³ species in the catalyst can be observed by electron paramagnetic resonance (EPR); these are attributable to isolated Ti⁺³ complexes. The remaining EPR silent Ti⁺³ species are believed to be bridged to another Ti⁺³ by Cl ligands. The total Cl content is equal to the sum of 2 × Mg + 3 × Al + 3.5 × Ti. Most of the p-cresol moiety apparently disappeared from the support, leaving much of ethyl benzoate in the catalyst. Activation with AlEt₃/methyl-p-toluate complex reduces 90% of the Ti⁺⁴ in the catalyst to lower oxidation states. The ester apparently moderates the alkylating power of AlEt₃ to avoid excessive formation of divalent titanium sites. There appears to be a constant fraction of 1/4–1/5 of the titanium which is isolated and the remainder is in bridged clusters independent of the oxidation states of titanium.     

Highly active MgCl2‐supported CpMCl3 (M = Ti,Zr) catalysts for ethylene polymerization

Monocyclopentadienyl compounds, CpMCl₃ (M = Ti, Zr) supported on activated MgCl₂ were used for the polymerizations of ethylene in the presence of methylaluminoxane (MAO) or a common alkylaluminium as a cocatalyst. By supporting CpMCl₃ on MgCl₂, the catalyst activity was increased drastically to show high activity similar to MgCl₂‐supported TiCl₄ catalysts. The activity of the CpZrCl₃ /MgCl₂ catalyst was higher than that of the CpTiCl₃/MgCl₂ one. Both catalysts gave polymers with high molecular weight (M_w) and broad molecular weight distribution (M_w/M_n) in comparison with the corresponding soluble half‐metallocene catalysts.