Showing papers on "Molten salt published in 2002"

Ionic liquid (molten salt) phase organometallic catalysis.

Abstract: For economical and ecological reasons, synthetic chemists are confronted with the increasing obligation of optimizing their synthetic methods. Maximizing efficiency and minimizing costs in the production of molecules and macromolecules constitutes, therefore, one of the most exciting challenges of synthetic chemistry.1-3 The ideal synthesis should produce the desired product in 100% yield and selectivity, in a safe and environmentally acceptable process.4 It is now well recognized that organometallic homogeneous catalysis offers one of the most promising approaches for solving this basic problem.2 Indeed, many of these homogeneous processes occur in high yields and selectivities and under mild reaction conditions. Most importantly, the steric and electronic properties of these catalysts can be tuned by varying the metal center and/or the ligands, thus rendering tailor-made molecular and macromolecular structures accessible.5,6 Despite the fact that various efficient methods, based on organometallic homogeneous catalysis, have been developed over the last 30 years on the laboratory scale, the industrial use of homogeneous catalytic processes is relatively limited.7 The separation of the products from the reaction mixture, the recovery of the catalysts, and the need for organic solvents are the major disadvantages in the homogeneous catalytic process. For these reasons, many homogeneous processes are not used on an industrial scale despite their benefits. Among the various approaches to address these problems, liquidliquid biphasic catalysis (“biphasic catalysis”) has emerged as one of the most important alternatives.6-11 The concept of this system implies that the molecular catalyst is soluble in only one phase whereas the substrates/products remain in the other phase. The reaction can take place in one (or both) of the phases or at the interface. In most cases, the catalyst phase can be reused and the products/substrates are simply removed from the reaction mixture by decantation. Moreover, in these biphasic systems it is possible to extract the primary products during the reaction and thus modulate the product selectivity.12 For a detailed discussion about this and other concepts of homogeneous catalyst immobilization, the reader is referred elsewhere.6,7 These biphasic systems might combine the advantages of both homogeneous (greater catalyst efficiency and mild reaction conditions) and heterogeneous (ease of catalyst recycling and separation of the products) catalysis. The advent of water-soluble organometallic complexes, especially those based on sulfonated phosphorus-containing ligands, has enabled various biphasic catalytic reactions to be conducted on an industrial scale.13-15 However, the use of water as a * Corresponding author. Fax: ++ 55 51 3316 73 04. E-mail: dupont@iq.ufrgs.br. 3667 Chem. Rev. 2002, 102, 3667−3692

Ionic Liquids: Solvents for the Electrodeposition of Metals and Semiconductors

Abstract: In a wider sense, ionic liquids are molten salts that melt below 100 °C. As their name suggests, they are solely composed of ions and many combinations of organic and/or inorganic cations and anions exist. Depending on the systems they can reach electrochemical windows of more than 4 V and thus they give access to a number of elements that cannot be electrodeposited from aqueous solutions, such as the light and refractory metals, as well as elemental and compound semiconductors. Presumably, ionic liquids will become important for electrochemical nanotechnology.

Green industrial applications of ionic liquids

Abstract: Preface. Obituary: Prof. Murray H. Brooker. Introductory Address. Potential for Use of Ionic Liquids in Czech Industry J. Kotlan. Potential to Apply Ionic Liquids in Industry: Exemplified for the Use as Solvents in Industrial Applications of Homogeneous Catalysis P. Wasserscheid. Ionic Liquids as Catalysts for Ethylbenzene Production M.P. Atkins, C. Bowlas, B. Ellis, F. Hubert, A. Rubatto, P. Wasserscheid. Applications of Ionic Liquids to Biphasic Catalysis H. Olivier-Bourbigou, F. Hugues. High-Temperature NMR Studies of Ionic-Liquid Catalysts O.B. Lapina, V.V. Terskikh, B.S. Bal'zhinimaev, K.M. Eriksen, R. Fehrmann. Ionic Liquids as Alternatives to Traditional Organic and Inorganic Solvents R. Pagni. The Pros and Cons of Using Ionic Liquids in the Pharmaceutical Industry R.M. Freer, A. Curzons. Room Temperature Ionic Liquids as Replacements for Traditional Organic Solvents and their Applications towards 'Green Chemistry' in Separation Processes A.E. Visser, R.P. Swatloski, W.M. Reichert, H.D. Willauer, J.G. Huddleston, R.D. Rogers. Application of Room-Temperature Ionic Liquids to the Chemical Processing of Biomass-Derived Feedstocks L. Moens, N. Khan. Room-Temperature Sulfur Chloride Ionic Liquids in Processes for the Isolation of Noble and Other Metals V.I. Pekhnyo, S.V. Volkov, N.G. Alexandrova. Ionic Liquids for Oil Shale Treatment M. Koel, K. Hollis, J. Rubin, T. Lombardo, B. Smith. Ionic Liquids in the Nuclear Industry: Solutions for the Nuclear Fuel Cycle W.R. Pitner, A.E. Bradley, D.W. Rooney, D. Sanders, K.R. Seddon, R.C. Thied, J.E. Hatter. Non-Invasive Spectroscopic On-Line Methods to Monitor Industrial Processes: A Review M.H. BrookerDAGGER, R.W. Berg. Ionic Liquids as Catalysts for Sulfuric Acid Production and Cleaning ofFlue Gases R. Fehrmann, K.M. Eriksen, S.B. Rasmussen. Modelling the Liquid Behaviour of Ionic Liquids E.A. Gontcharenko, P.F. Zil'berman, V.S. Znamenskii. The Challenges of Building a Molten Salt Database J. Fuller, M. Gaune-Escard. The Past, Present and Future of Ionic Liquids as Battery Electrolytes J. Wilkes. Radical-Ion Melts of Aluminium, Gallium and Sulfur Halides for Novel Power Sources S.V. Volkov, Z.A. Fokina, O.G. Yanko. Electrochemistry of Niobium, Tantalum and Titanium in Low-Temperature Carbamide-Halide Melts N. Tumanova, O. Boyko, N. Buryak, S. Kochetova. Electrochemistry of Niobium in Rubidium and Caesium Halide and Oxohalide Melts, and the Electrochemical Synthesis of Novel Niobium Compounds V.V. Grinevitch, A.V. Arakcheeva, S.A. Kuznetsov. Photochemistry in Ionic Liquids C.M. Gordon. Ionic Liquids Derived from Natural Products and Other Novel Chemistries: Synthesis and Chemistry of Ionic Liquids Composed of Functionalised Ions J.H. Davis, Jr. Ionic Liquids and Supercritical CO2 L.A. Blanchard, Z. Gu, J.F. Brennecke, E.J. Beckman. Acids and Bases in Ionic Liquids K.E. Johnson. Ionic Liquid Crystals as Universal Matrices (Solvents): Main Criteria for Ionic Mesogenicity T.A. Mirnaya, S.V. Volkov. Ionic Liquids as Solvents for Organic Synthesis A.R. Sethi, P. Smith, N. Srinivasan, T. Welton. East-West Collaboration within the NATO Science Programme: Opportunities and Project Management S. Boghosian. Alkane and Cycloalkane Transformations in Superelectrophilic Liquids I.S. Akhrem, A.V. Orlinkov, M.E. Vol'pin. The Dissolution of Kerogen in Ionic Liquids Y. Patell, K.R. Seddon, L. Dutta, A. Fleet. Electrochemical Synthesis of Volatile Metal Complexes, as Precursors for Functional

Novel polymer electrolytes prepared by copolymerization of ionic liquid monomers

Abstract: Ionic liquid monomer couples were prepared by the neutralization of 1-vinylimidazole with vinylsulfonic acid or 3-sulfopropyl acrylate. These ionic liquid monomer couples were viscous liquid at room temperature and showed low glass transition temperature (Tg) at −83 °C and −73 °C, respectively. These monomer couples were copolymerized to prepare ion conductive polymer matrix. Thus prepared ionic liquid copolymers had no carrier ions, and they showed very low ionic conductivity of below 10−9 S cm−1. Equimolar amount of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to imidazolium salt unit was then added to generate carrier ions in the ionic liquid copolymers. Poly(vinylimidazolium-co-vinylsulfonate) containing equimolar LiTFSI showed the ionic conductivity of 4 × 10−8 S cm−1 at 30 °C. Advanced copolymer, poly(vinylimidazolium-co-3-sulfopropyl acrylate) which has flexible spacer between the anionic charge and polymer main chain, showed the ionic conductivity of about 10−6 S cm−1 at 30 °C, which is 100 times higher than that of copolymer without spacer. Even an excess amount of LiTFSI was added, the ionic conductivity of the copolymer kept this conductivity. This tendency is completely different from the typical polyether systems. Copyright © 2002 John Wiley & Sons, Ltd.

Ionic liquid-coated enzyme for biocatalysis in organic solvent.

Abstract: Ionic liquid-coated enzyme (ILCE) is described as a useful catalyst for biocatalysis in organic solvent An ionic liquid, [PPMIM]-[PF6] (1, [PPMIM] = 1-(3'-phenylpropyl)-3-methylimidazolium), which is solid at room temperature and becomes liquid above 53 degreesC, was synthesized in two steps from N-methylimidazole The coating of enzyme was done by simply mixing commercially available enzyme with 1 in the liquid phase above 53 degreesC and then allowing the mixture to cool A representative ILCE, prepared with a lipase from Pseudomonas cepacia, showed markedly enhanced enantioselectivity without losing any significant activity

A Highly Conductive Room Temperature Molten Fluoride: EMIF ⋅ 2.3 HF

Abstract: Reaction of 1-ethyl-3-methylimidazolium chloride (EMICl) and anhydrous hydrogen fluoride gives a nonvolatile, room temperature molten salt. EMIF.2.3HF. The elemental analysis, vibrational, and nuclear magnetic resonance spectroscopy suggests the presence of oligomeric anions. (HF) n F - , in the salt The liquid is stable in air and able to he handled in a Pyrex glass vessel. The specific conductivity is 100 mS cm -1 at 298 K. which is extremely high compared with other salts of this kind. The high conductivity is realized by its low viscosity(4.85cP at 298 K) The liquid temperature ranges from 180 to 350 K, and electro-chemical window is about 3.2 V when a vitreous carbon is used for the electrode material.

A force field for liquid state simulations on room temperature molten salts: 1-Ethyl-3-methylimidazolium tetrachloroaluminate

Abstract: A classical force field for the room temperature molten salt 1-ethyl-3-methylimidazolium tetrachloroaluminate has been developed and successfully tested against experimental data (neutron diffraction, diffusion constants) by molecular dynamics computer simulation corresponding to a temperature of 298 K. The force field parameters for the cation have been derived from the AMBER description for the protonated amino acid histidine, whereas the AlCl4- parameters have been achieved by parametrization of intramolecular terms with van der Waals parameters taken from the literature. All atomic partial charges have been obtained from ab initio calculations using the RESP methodology.

High-speed heck reactions in ionic liquid with controlled microwave heating.

Abstract: Palladium-catalyzed Heck arylations in the polar and robust ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF(6)), have for the first time been accomplished under microwave irra ...

The influence of NOx on soot oxidation rate: molten salt versus platinum

Abstract: A systematic study was carried out to assess the influence of simulated diesel exhaust on the activity of molten salt, Cs2SO4·V2O5, supported on ceramic foam and Pt/-alumina catalysts in the oxidation of diesel soot. Gas compositions containing O2 ,N O x , CO, C3H6, and SO2 were used. The activity of molten salt catalyst, an active catalyst for the oxidation of soot with O2, is slightly affected by the gas component due to NO2 already present in NOx . In contrast, the presence of NOx , significantly increases the soot oxidation rate with platinum catalyst. These changes were due to the catalytic oxidation of NO to NO2 with platinum, followed by soot oxidation with NO2. Three configurations are compared, viz. a fixed bed containing a physical mixture of Pt catalyst and soot, Pt catalyst upstream of a fixed bed containing soot, and Pt catalyst upstream of soot loaded on ceramic foam supported molten salt. The reaction cycle of oxidation of NO, followed by soot oxidation with the NO2 produced, was observed only in a physical mixture of platinum catalyst and soot. © 2002 Elsevier Science B.V. All rights reserved.

A new class of hybrid materials via salt inclusion: novel copper(II) arsenates Na(5)ACu(4)(AsO(4))(4)Cl(2) (A = Rb, Cs) composed of alternating covalent and ionic lattices.

Abstract: Two novel copper(II) arsenates Na5ACu4(AsO4)4Cl2 (A = Rb, Cs) were synthesized by conventional solid-state methods using reactive molten salt media. These compounds are isostructural and crystallize in an orthorhombic lattice (Fmmm, No. 69; Z = 8). The cell constants are a = 14.632(3) A, b = 18.872(2) A, c = 14.445(3) A, V = 3989(1) A3, for A = Rb; a = 14.638(3) A, b = 18.990(4) A, c = 14.418(3) A, V = 4008(1) A3, for A = Cs. Single-crystal structure studies reveal a new composite framework consisting of alternating covalent and ionic lattices. The covalent lattice contains highly oriented oligomeric mu-oxo [Cu4O12]16- tetrameric units with a cyclo-S8-like Cu4O4 magnetic core that resembles the building block of layered cuprates. The ionic slab consists of a novel framework of mixed alkali metal chloride lattice and rarely seen Na6O8 clusters. Similar to organic-inorganic hybrid materials, the title compounds present a new class of host-guest chemistry via salt inclusion reactions.

Molten Salts: From Fundamentals to Applications

Abstract: Preface. Molten Salts: Fundamentals. Interionic Forces and Relevant Statistical Mechanics M.P. Tosi. Electronic Properties of Metal/Molten Salt Solutions W.W. Warren, Jr. Light Scattering from Molten Salts: Structure and Dynamics G.N. Papatheodorou, S.N. Yannopoulos. Neutron Scattering: Technique and Applications to Molten Salts A.K. Adya. Metal-Molten Salt Interfaces: Wetting Transitions and Electrocrystallization W. Freyland. Modelling of Thermodynamic Data H.A. Oye. Thermodynamic Model of Molten Silicate Systems V. Danek, Z. Panek. Data Mining and Multivariate Analysis in Materials Science: Informatics Strategies for Materials Databases K. Rajan, et al. Pyrochemistry in Nuclear Industry T. Inoue, Y. Sakamura. Molten Salts for Safe, Low Waste and Proliferation Resistant Treatment of Radwaste in Accelerator Driven and Critical Systems V.V. Ignatiev. Electrochemical Techniques Some Aspects of Electrochemical Behaviour of Refractory Metal Complexes S.A. Kuznetsov. Origin and Control of Low-Melting Behavior in Salts, Polysalts, Salt Solvates, and Glassformers C.A. Angell. Electrodes and Electrolytes for Molten Salt Batteries: Expanding the Temperature Regimes R.T. Carlin, J. Fuller. Synthesis and Catalysis in Room-Temperature Ionic Liquids P.J. Smith, et al. Coordination Compounds in Melts S.V. Volkov. Calorimetric Methods M. Gaune-Escard. Subject Index.

Dielectric relaxation and underlying dynamics of acetonitrile and 1-ethyl-3-methylimidazolium triflate mixtures using THz transmission spectroscopy

Abstract: We use terahertz (THz) transmission spectroscopy to obtain the frequency dependent complex dielectric functions for pure acetonitrile, pure 1-ethyl-3-methylimidazolium triflate (emim triflate, a room temperature molten salt), and mixtures of the two liquids. The behavior of the pure liquids is modeled with either two (acetonitrile) or three (emim triflate) Debye relaxations. We then discuss the interactions of the molten salt and solvent based on the modified Debye relaxations evident in the mixtures. We determine that at low molten salt concentrations, the mixtures behave like electrolyte solutions of a crystalline salt dissolved in a solvent. At higher molten salt concentrations, the behavior is that of a mixture of two liquids.

Light-emitting electrochemical cells using a molten delocalized salt

Abstract: The device performances of light-emitting electrochemical cells are improved by adding a room-temperature molten salt (tetrahexylammonium-bis-trifluoro-methyl-sulfonyl imide) directly into the light-emitting layer. For poly(9,9-dihexyl-fluorene-2,7-diyl) with an indium-tin-oxide anode and an aluminum cathode, the power efficiency can be increased by more than one order of magnitude. An even more pronounced effect is observed for poly [2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylenevinylene]. Equally important for both luminescent polymers, the operating voltage is drastically reduced.

Molten salt receiver cooling system

Abstract: A flow of molten salt is provided through a solar-thermal heat exchange receiver. The receiver converts solar energy, reflected from heliostats, to thermal energy that is stored in molten salt. A vessel holds a store of molten salt for cooling the receiver upon a loss of flow. At the outlet of the receiver, an air separator removes air entrained in the flow of molten salt. From the air separator, the flow of molten salt proceeds through a downcomer having flow obstacles to a hot storage tank.

Solid-liquid equilibria in mixtures of molten salt hydrates for the design of heat storage materials

Abstract: Enthalpy of melting can be used to store heat in a simple way for time periods of hours and days. Knowledge of the solid-liquid equilibria represents the most important pre- sumption for systematic evaluations of the suitability of hydrated salt mixtures. In this paper, two approaches for predicting solid-liquid equilibria in ternary or higher component systems are discussed using the limited amount of thermodynamic data available for such systems. One method is based on the modified Brunauer-Emmett-Teller (BET) model as formulated by Ally and Braunstein. In cases of a strong tendency toward complex formation of salt components, the BET model is no longer applicable. Reaction chain models have been used to treat such systems. Thereby, the reaction chain represents a method to correlate step-wise hydration or com- plexation enthalpies and entropies and, thus, reduce the number of adjustable parameters. Results are discussed for systems containing MgCl 2 , CaCl 2 , ZnCl 2 , and alkali metal chlo- rides.