Electrochemical behavior of aluminum and some of its alloys in chloroaluminate ionic liquids: electrolytic extraction and electrorefining

The electrochemical behaviors of pure Al, Al–6%Si, Al–3%Cu, and Al–3.7%Cu–0.9%Mg–0.8%Pb–0.6%Fe alloys were investigated in the chloroaluminate ionic liquids 1-butyl-3-methylimidazolium chloride [BMIm]Cl/AlCl₃ (40/60 mol%) and 1-ethyl-3-methylimidazolium chloride [EMIm]Cl/AlCl₃ (40/60 mol%). Electrolytic extraction of copper from Al–Cu alloys in the employed ionic liquids was explored. The alloys were anodically dissolved in the ionic liquids and then pure copper was recovered under potentiostatic conditions. Due to the large difference between the deposition potentials of Cu and Al, pure Cu can be obtained without Al contamination. Electrorefining of Al–3%Cu and Al–6%Si alloys was also investigated in [BMIm]Cl/AlCl₃ (40/60 mol%) at room temperature. High purity aluminum deposits were obtained with significantly low energy consumption of about 2 kWh/kg of Al.     

A new method for practical electrodeposition of aluminium from ionic liquids

Successful electrodeposition of aluminium from ionic liquids has been long achieved scientifically. Nevertheless, standard industrial procedures have not yet been established due to the difficulties associated with using closed system filled with inert gas for the electrodeposition process. This paper presents a new methodology in which electrodeposition of aluminium is conducted in air, after preparation of ionic liquids in a glove box and covering them by a nonwater-absorbable layer of particular organic compound. This compound is stable and shows no reaction with the ionic liquid. Using this new methodology, functional aluminium layers were successfully deposited from a first generation ionic liquid AlCl₃/1-ethyl-3-methylimidazolium chloride – [EMIm]Cl – (60/40 mol%) on low carbon steel. Cyclic voltammetry (CV) measurements revealed that there was no significant difference in electrochemical properties characteristic of Al deposition when conducted in open air. SEM/EDX assessments showed that uniform, dense and adherent Al layers were obtained. Adherence of Al to the steel substrate was improved via in-situ electrochemical etching.     

Electrodeposition of Al,Zn, and Pt on silver-coated textile fibres from ionic liquids

In the present paper, we report on the electrodeposition of aluminium, zinc and platinum on silver-coated textile fibres from ionic liquids. For electrodeposition of Al, the 60:40 mol% mixture of AlCl₃/1-ethyl-3-methylimidazolium chloride ([EMIm]Cl) and 1.7 M AlCl₃ in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py_1,4]TFSA) were employed. It was observed that microcrystalline aluminium was electrodeposited on the textile fibres in 60:40 mol% AlCl₃/[EMIm]Cl. The deposited Al layers either on single fibres or on textile assemblies are well adherent and uniform. An adherent, homogeneous and nanocrystalline Al layer was obtained on the silver-coated textile samples from 1.7 M AlCl₃/[Py_1,4]TFSA at 75 °C. The obtained Al layers from 60:40 mol% AlCl₃/[EMIm]Cl on the textile fibres exhibit a good corrosion resistance in an aqueous iodide/iodine electrolyte. Furthermore, we obtain Al microtubes from the investigated ionic liquids after dissolving the textile fibres. In addition, zinc electrodeposition was carried out on the textile samples from 60:40 mol% ZnCl₂/[EMIm]Cl at 80 °C. The electrodeposition of platinum on the textiles was done from 50 mM PtCl₂ in 1-butyl-1-methylpyrrolidinium dicyanamide ([Py_1,4]DCA).     

Effect of ionic liquid 1-methylimidazolium chloride on the vapour liquid equilibrium of water,methanol, ethanol,and {water + ethanol} mixture

Measurements of vapour pressure data were conducted using a quasi-static ebulliometer for systems containing water, methanol, ethanol, and a mixture of {water + ethanol} in the presence of an ionic liquid (IL), namely, 1-methylimidazolium chloride ([MIm]Cl), wherein the IL-content ranged from w₂ = (0.10 to 0.50). The vapour pressure data of IL-containing binary systems were correlated by the NRTL model with an overall average absolute relative deviation (AARD) of 0.0103, and the resulting binary parameters were used to predict the vapour pressures of a ternary system {water + ethanol + [MIm]Cl} with an AARD less than 0.0077. Further, the isobaric vapour liquid equilibria (VLE) for the ternary system {water + ethanol + IL} with IL-content of w₃ = (0.10, 0.30, and 0.50) for [MIm]Cl and x₃ = 0.15 for [MIm]Cl, [C₄MIm]Cl, and [C₆MIm]Cl were predicted at 101.3 kPa, respectively. It is indicated that [MIm]Cl presents the strongest ability to enhance the relative volatility of ethanol to water in the mixture of {water + ethanol} than that of [C₄MIm]Cl and [C₆MIm]Cl, which is consistent with the cationic sizes and hence the ionic hydration ability. Therefore, distillation separation of the azeotrope of {water + ethanol} can be sufficiently facilitated by the addition of [MIm]Cl at a specified content.     

Determination of the activities in the (Ni + Al) alloys in the temperature range 870 K to 920 K by a solid-state galvanic cell using a CaF2 electrolyte

The activities of aluminium and nickel are constituents in the (Ni + Al) superalloys in the concentration range 50 mol% to 70 mol% of Al at the temperatures (870, 900, and 920) K were determined with the help of solid-state galvanic cells involving calcium fluoride as an electrolyte. The partial molar Gibbs free energies of aluminium and nickel in the alloys, and the Gibbs free energy of mixing were calculated from the e.m.f. data. The values of the standard Gibbs free energies of formation of the intermetallic compounds NiAl, Ni₂Al₃, and NiAl₃ are also given.     

Thermodynamic studies of the ionic liquid 1-hexyl-3-methylimidazolium chloride [C6mim][Cl] in polyethylene glycol aqueous solutions

Vapour pressure osmometery (VPO) measurements at T = 308.15 K for {[C₆mim][Cl] + water}, {[C₆mim][Cl] + (0.005, 0.0155, and 0.0263) mol · kg⁻¹ PEG2000 + water} and {[C₆mim][Cl] + (0.0017, 0.0052, and 0.0088) mol · kg⁻¹ PEG6000 + water} systems and isopiestic measurements at T = 298.15 K for {[C₆mim][Cl] + PEG2000 + water} and {[C₆mim][Cl] + PEG6000 + water} systems have been carried out. The VPO measurements were carried out at very low concentrations of PEG and from which the values of the water activities, osmotic coefficients, vapour pressure and activity coefficients were obtained. The data obtained from the VPO method show that over the whole concentration range of the ionic liquid (IL), the activity coefficients of [C₆mim][Cl] in the presence of PEG2000 are increased. Although, at high IL concentrations, the values of the activity coefficient of [C₆mim][Cl] in the presence of PEG6000 are also increased, however for low concentrations of IL the values of the activity coefficient of [C₆mim][Cl] in pure water are larger than those in aqueous PEG6000 solutions. For a known IL concentration, the values of water activity coefficient for the binary {[C₆mim][Cl] + water} system are larger than those for the ternary {[C₆mim][Cl] + PEG + water} systems and decrease by increasing the concentration of PEG or decreasing the molar mass of PEG. The constant water activity lines of the all ternary systems obtained from the isopiestic method show positive deviation from the linear isopiestic relation (Zdanovskii–Stokes–Robinson rule) derived using the semi-ideal hydration model. The results have been interpreted in terms of the solute–water and solute–solute interactions.     

Synthesis and properties of 5,10,15,20-tetra(4-lauroylimidophenyl)porphyrin and its metal complexes

Transition metal complexes of 5,10,15,20-tetra(4-lauroylimidophenyl)porphyrin TLPPM [M = Mn(Cl), Fe(Cl), Co, Ni, Cu, Zn] have been synthesized and characterized by means of elemental analyses, UV–VIS spectra, infrared spectra, ¹H NMR spectra, molar conductance, differential scanning calorimetry (DSC), polarized optical microscopy (POM), cyclic voltammetry, luminescence spectra and surface photovoltage spectroscopies. The porphyrin ligand shows liquid crystalline behaviour, and it exhibits a high phase transition temperature 182 °C and a broad mesophase temperature span, 88 °C. The oxidation and reduction properties of the compounds were investigated by cyclic voltammetry. The photovoltaic properties and charge transfer process of the compounds were investigated by surface photovoltage spectroscopy (SPS) and electric field-induced surface photovoltage spectroscopic (EFISPS) techniques, which revealed that all the compounds are p-type semiconductors. Quantum yields of the S₁ → S₀ fluorescence were measured at room temperature. These studies will contribute to further choice and application of the liquid crystals.     

(Liquid + liquid) equilibrium of aqueous biphasic systems composed of 1-benzyl or 1-hexyl-3-methylimidazolium chloride ionic liquids and inorganic salts

(Liquid + liquid) equilibria for {1-benzyl-3-methylimidazolium chloride ([BzMIM]Cl) or 1-hexyl-3-methylimidazolium chloride ([HMIM]Cl) + inorganic salts (potassium phosphate K₃PO₄, potassium carbonate K₂CO₃, or dipotassium hydrogen phosphate K₂HPO₄) + H₂O} aqueous biphasic systems (ABSs) are presented at T = 298.15 K. An empirical equation was used to correlate the binodal data. The experimental tie lines were appropriately correlated by the Othmer–Tobias and Brancroft empirical equations. The influence of the selected inorganic salts in the phase segregation was investigated by means the calculated effective excluded volume (EEV) and Setschenow-type equation. The salting-out ability of salts was also evaluated in terms of the Gibbs energy of hydration of salt (ΔG_hyd) and assessed with EEV values.     

Glass transition behaviour of the quaternary ammonium type ionic liquid, {[DEME][I] + H2O} mixtures

By a simple DTA system, the glass transition temperatures of the quaternary ammonium type ionic liquid, {N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium iodide, [DEME][I] + H₂O} mixtures after quick pre-cooling were measured as a function of water concentration (x mol% H₂O). Results were compared with the previous results of {[DEME][BF₄] + H₂O} mixtures in which double glass transitions were observed in the water concentration region of (16.5 to 30.0) mol% H₂O. Remarkably, we observed the double glass transition phenomenon in {[DEME][I] + H₂O} mixtures too, but the two-T_gs regions lie towards the water-rich side of (77.5 to 85.0) mol% H₂O. These clearly reflect the difference in the anionic effect between ${\text{BF}}_4^{-}$ and I^? on the water structure. The end of the glass-formation region of {[DEME][I] + H₂O} mixtures is around x = 95.0 mol% H₂O, and this is comparable to that of {[DEME][BF₄] + H₂O} mixtures (x = 96.0 mol% H₂O).     

(Vapour + liquid) equilibria,volumetric and compressibility behaviour of binary and ternary aqueous solutions of 1-hexyl-3-methylimidazolium chloride,methyl potassium malonate,and ethyl potassium malonate

(Vapour + liquid) equilibrium data (water activity, vapour pressure, osmotic coefficient, and activity coefficient) of binary aqueous solutions of 1-hexyl-3-methylimidazolium chloride ([C₆mim][Cl]), methyl potassium malonate, and ethyl potassium malonate and ternary {[C₆mim][Cl] + methyl potassium malonate} and {[C₆mim][Cl] + ethyl potassium malonate} aqueous solutions were obtained through the isopiestic method at T = 298.15 K. These results reveal that the ionic liquid behaves as surfactant-like and aggregates in aqueous solutions at molality about 0.4 mol · kg⁻¹. The constant water activity lines of all the ternary systems investigated show small negative deviations from the linear isopiestic relation (Zdanovskii–Stokes–Robinson rule) derived using the semi-ideal hydration model. The density and speed of sound measurements were carried out on solutions of methyl potassium malonate and ethyl potassium malonate in water and of [C₆mim][Cl] in aqueous solutions of 0.25 mol · kg⁻¹ methyl potassium malonate and ethyl potassium malonate at T = (288.15 to 308.15) K at atmospheric pressure. From the experimental density and speed of sound data, the values of the apparent molar volume, apparent molar isentropic compressibility and excess molar volume were evaluated and from which the infinite dilution apparent molar volume and infinite dilution apparent molar isentropic compressibility were calculated at each temperature. Although, there are no clear differences between the values of the apparent molar volume of [C₆mim][Cl] in pure water and in methyl potassium malonate or ethyl potassium malonate aqueous solutions, however, the results show a positive transfer isentropic compressibility of [C₆mim][Cl] from pure water to the methyl potassium malonate or ethyl potassium malonate aqueous solutions. The results have been interpreted in terms of the solute–water and solute–solute interactions.     

Dual role of the six-coordinated molybdenum and lead ions in novel of photochromic properties of the molybdenum–lead–borate glasses

Transparent glasses were prepared by conventional melting–quenching method in the xMoO₃·(100 ? x)[3B₂O₃·PbO] system where 0 ≤ x ≤ 15 mol%. By increasing the MoO₃ content up to 20 mol% the PbMoO₄ crystalline phase appears. These systems exhibit a photochromic effect which can be induced through laser exposures (λ = 633 nm) directly on the bulk sample. Structural investigations by FTIR spectroscopy show that the photosensitive effect is due to a reduction of Mo⁶⁺ to Mo⁴⁺ and/or Mo⁵⁺ promoted by the oxidation of Pb²⁺ and some structural changes of the borate network.     

Functionalized N-heterocyclic carbene iridium complexes: Synthesis,structure and addition polymerization of norbornene

Picolyl, pyridine, and methyl functionalized N-heterocyclic carbene iridium complexes [Cp¹Ir(C^N)Cl]Cl (4, C^N = 3-Methyl-1-picolyimidazol-2-ylidene), [Cp¹Ir(C^N)Cl][Cp¹IrCl₃] (5), [Cp¹Ir(C-N)Cl]Cl (6, C-N = 3-Methyl-1-pyridylimidazol-2-ylidene) and [Cp¹Ir(L)Cl₂] (7, L = 1,3-dimethylimidazol-2-ylidene) have been synthesized by transmetallation from Ag(I) carbene species, and characterized by ¹H NMR, ¹³C NMR spectra and elemental analyses. The molecular structures of 5–7 have been confirmed by X-ray single-crystal analyses. The iridium carbene complexes 4 and 6 show moderate catalytic activities (3.03 × 10⁵ g PNB (mol Ir)^?1 h^?1 and 1.70 × 10⁶ g PNB (mol Ir)^?1 h^?1) for the addition polymerization of norbornene in the presence of methylaluminoxane (MAO) as co-catalyst. The produced polynorbornene have been characterized by IR, ¹H NMR and ¹³C NMR spectra, showing it follows the vinyl-addition-type of polymerization.     

Electrochemiluminescent metallopolymers: Tuning the emission wavelength by energy transfer between two bound centres

The electrochemical and photonic properties of a metallopolymer in which both [Ru(dpp)₂Cl]⁺ (N5Cl) and [Ru(dpp)₂]²⁺ (N6) moieties are coordinated to a poly(4-vinylpyridine) backbone are described, dpp is 4,7-diphenyl-1,10-phenanthroline. Cyclic voltammetry and luminescence studies indicate that approximately 2% of centres are bis-coordinated to the PVP backbone, i.e., 2% are [Ru(dpp)₂]²⁺. When dissolved in ethanol or acetonitrile, two photoluminescence peaks are observed, at 620 and 720 nm corresponding to the N6 and N5Cl moieties, respectively. This dual emission indicates that the two centres communicate weakly in solution. In contrast, in aqueous solution or in thin films, a single emission band at 720 nm is observed suggesting efficient energy transfer to the N5Cl moiety. Polymer films generate electrochemiluminescence in the presence of oxalate as a co-reactant with an emission maximum at 730 nm corresponding to emission from the N5Cl centres alone.     

New chloro and triphenylsiloxy derivatives of dioxomolybdenum(VI) chelated with pyrazolylpyridine ligands: Catalytic applications in olefin epoxidation

Dioxomolybdenum(VI) complexes of general formula [MoO₂X₂L₂] (X = Cl, OSiPh₃; L₂ = 2-(1-butyl-3-pyrazolyl)pyridine, ethyl[3-(2-pyridyl)-1-pyrazolyl]acetate) were prepared and characterised by ¹H NMR, IR and Raman spectroscopy. The assignment of the vibrational spectra was supported by ab initio calculations. A single crystal X-ray diffraction study of the complex [MoO₂Cl₂{ethyl[3-(2-pyridyl)-1-pyrazolyl]acetate}] showed that the compound is monomeric and crystallises in the tetragonal system with space group P4₁. The four complexes are active and selective catalysts for the liquid-phase epoxidation of olefins by tert-butylhydroperoxide. Selectivities to the corresponding epoxides were mostly 100% (for conversions of at least 34%) for the substrates cyclooctene, cyclododecene, 1-octene, trans-2-octene and (R)-(+)-limonene. For styrene epoxidation, the corresponding diol was also formed in significant quantities. The turnover frequencies for cyclooctene epoxidation at 55 °C were around 340 mol mol_Mo⁻¹ h⁻¹ for the chloro complexes and 160 mol mol_Mo⁻¹ h⁻¹ for the triphenylsiloxy complexes. The addition of co-solvents (1,2-dichloroethane or n-hexane) had a detrimental effect on catalytic activities. Kinetic studies for the two complexes bearing the ligand ethyl[3-(2-pyridyl)-1-pyrazolyl]acetate revealed an apparent first order dependence of the initial rate of cyclooctene conversion with respect to cyclooctene or oxidant concentration.     

Synthetic procedures and structural features of new di- and tri-nuclear chelate compounds of Cd(II) with sulfur and nitrogen donor ligands

Cd(dmpymt)₂ reacts with CdCl₂, CdBr₂·4H₂O, CdI₂, 2,2′-bipyridine and 1,10-phenanthroline to give the dimeric chelates [Cd(dmpymt)(bpy)Cl]₂ and [Cd(dmpymt)(phen)Cl]₂, as well as the tri-nuclear complexes [Cd₃(dmpymt)₄(bpy)₂Br₂] and [Cd₃(dmpymt)₄(bpy)₂I₂] (dmpymtH = 4,6-dimethylpyrimidine-2-thione; bpy = 2,2′-bipyridine; phen = 1,10-phenantroline). In all complexes the Cd(II) centers present the coordination number six. The new compounds are examples of the managing of the final aggregation state of thiolate metal complexes by introducing co-ligands to block specific coordination sites of the metal center.     

Performance of a bench-scale membrane pilot plant for the upgrading of biogas in a wastewater treatment plant

A bench-scale membrane pilot plant for upgrading biogas generated at a municipal wastewater treatment plant was constructed and operated for extended periods of time. The raw biogas was available at 45–60 psia (3.1–4.1 bar) and contained 62.6 mol% CH₄, the balance being mainly CO₂ and a large number of organic impurities. The operation of the pilot plant was tested with two identical hollow-fiber modules for periods of over 1000 h (41 days) with each module. One of the hollow-fiber modules was tested at an average pressure of about 525 psia (36 bar) and at stage-cuts of 0.34–0.41, and the other module at about 423 psia (29 bar) and at stage-cuts of 0.36–0.39. The flow rates of the biogas feed were 30–36 ft³/h (2.4×10⁻⁴–2.8×10⁻⁴ m³/s) and 21–24 ft³/h (1.7×10⁻⁴–1.9×10⁻⁴ m³/s), respectively. The CH₄ concentration in the retentate stream (the upgraded biogas) was raised in these tests to 92–95 mol% CH₄. The performance of the pilot plant was stable over the entire test periods. An even higher CH₄ concentration of 97 mol% was reached in short-term tests at a stage-cut of 0.46. The raw biogas had to be pretreated to prevent the condensation of organic impurities which tended to dissolve the hollow fibers. Upgraded biogas containing over 90 mol% CH₄ produced in a large-scale membrane separation plant could be used for the generation of electricity. At the same time, the permeate (waste) stream would contain over 15 mol% CH₄ and could be used for heating applications.     

Helical chains of [MO5Cl] octahedra – Three compounds in the new family AEM2Te3O8Cl2 (AE = Ca,Sr and M = Co,Ni)

The compounds CaCo₂Te₃O₈Cl₂, SrCo₂Te₃O₈Cl₂ and SrNi₂Te₃O₈Cl₂ were synthesized via solid–gas reactions and investigated using single-crystal X-ray diffraction. While the compound CaCo₂Te₃O₈Cl₂ formed large enough single crystals to allow for a detailed structural analysis, crystals of the Sr-containing compounds yielded evidence that they are isostructural. CaCo₂Te₃O₈Cl₂ crystallizes in the monoclinic system, space group P2₁/c, a = 6.537(2) Å, b = 9.088(2) Å, c = 19.500(9) Å, β = 113.36(4)°, Z = 4. It exhibits [CoO₅Cl] helical chains along the [010] direction, connected by [CaO₈] polyhedra, [TeO₃E] tetrahedra and [TeO₄E] trigonal bipyramids (the lone pair of electrons on Te^IV is designated as E) to form a layer. The layers are held together only by weak van der Waals forces; the shortest interlayer distance is a Te?Cl contact of 3.432(4) Å.     

Surveying the {AuCl} adducts of bulky phosphines bearing the 2,6-dimesitylphenyl group

A series of gold chloride {AuCl} adducts of the sterically demanding phosphines DmpPR₂ (Dmp = 2,6-dimesitylphenyl; R = H (1); Me (2); Cl (3)) have been prepared. The adducts are readily formed by the reaction of Au(tht)Cl and DmpPR₂, yielding [(DmpPR₂)AuCl] (R = H (4); Me (5); Cl (6)) in moderate to excellent yields. All three new compounds have been structurally characterized. The structures demonstrate little or no significant intermolecular Au?Au or intramolecular Au?arene interactions. In addition, the new difluoroarylphosphine DmpPF₂ (7) has been prepared and structurally characterized.     

Vibrational interactions in dimethylgold(III) halides and carboxylates

The far-infrared and Raman spectra of binuclear molecules [Me₂AuX]₂ (X = Cl, Br, I) and [Me₂Au(OOCR)]₂ (R = Me, CF₃, Bu^t, Ph) in the 600–70 cm⁻¹ region are reported. The experimentally measured vibrational frequencies of [Me₂AuX]₂ are in a good agreement with density functional theory predictions. The Au…Au vibrational interactions predicted to be in the 270–60 cm⁻¹ region of [Me₂AuX]₂ far-IR and Raman spectra have been observed. The Raman-active Au…Au vibrations of the [Me₂Au(OOCR)]₂ molecules were found to be in the same region as those of [Me₂AuX]₂. The Au–X stretching modes were observed between 100 and 250 cm⁻¹ in accordance with the DFT predictions. Their frequencies in the IR spectra of [Me₂AuX]₂ increase in the sequence I < Br < Cl while the AuC₂ stretching frequencies decrease in the same order. This fact might be an evidence of the decreasing covalent character of the gold-halogen bridges. The Au–O stretching bands of dimethylgold(III) carboxylates have been observed in the 500–250 cm⁻¹ region, and Au–C stretching frequencies of both [Me₂AuX]₂ and [Me₂Au(OOCR)]₂ compounds have been found between 600 and 500 cm⁻¹.     

Molecular switching complexes with iron and tin as central atom

The precursor [Fe^III(L)Cl] (LH₂ = N,N′-bis(2′-hydroxy-benzyliden)-1,6-diamino-3-N-hexane is a high-spin (S = 5/2) complex. This precursor is combined with the bridging units [Sn^IV(X)₄] (X = CN^?, NCS^?) to yield star-shaped pentanuclear clusters, [(LFe^III–X)₄Sn]Cl₄. For X = CN^? the ⁵⁷Fe-Mössbauer data show a multiple spin transition between iron(III) in the high-spin and low-spin state, while the ^119mSn-Mössbauer data indicate a valence tautomerism between Sn(IV) and Sn(II). Changing the bridging unit from X = CN^? to X = NCS^? turns the switchability off.