Chloroaluminate Ionic Liquids Research Articles

Polystyrene-supported chloroaluminate ionic liquid as a new heterogeneous Lewis acid catalyst for Knoevenagel condensation

Abstract Non-hygroscopic polystyrene-supported chloroaluminate ionic liquid was prepared from the reaction of Merrifield resin with 1-methylimidazole followed by reaction with aluminum chloride. This Lewis acidic ionic liquid is environmentally friendly heterogeneous catalyst for the Knoevenagel condensation of aromatic and aliphatic aldehydes with ethyl cyanoacetate. The catalyst is stable (as a bench top catalyst) and reusable.

Polystyrene-Supported Pyridinium Chloroaluminate Ionic Liquid as a New Heterogeneous Lewis Acid Catalyst for Knoevenagel Condensation

Non-hygroscopic polystyrene-supported chloroaluminate ionic liquid was prepared from the reaction of Merrifield resin with pyridine followed by reaction with aluminium chloride. This Lewis acidic ionic liquid is an environmentally friendly heterogeneous catalyst for the Knoevenagel condensation of aromatic and aliphatic aldehydes with ethyl cyanoacetate. The catalyst is stable (as a bench top catalyst) and can be easily recovered and reused without appreciable change in its efficiency.

Enhanced activity and selectivity in n-octane isomerization using a bifunctional SCILL catalyst

Bifunctional Solid Catalyst with Ionic Liquid Layer (SCILL) systems are presented and applied in the skeleton isomerization of n-octane in a slurry-phase reaction mode. It is demonstrated that Pt on silica, coated with a thin film of acidic chloroaluminate ionic liquid exhibits remarkable catalytic performance under mild conditions in the presence of hydrogen. Interestingly, both selectivity and activity of n-octane isomerization increase in these systems as a function of hydrogen pressure. This does not only suggest a hydrogenation activity of the catalytic Pt-centers embedded in the strongly Lewis acidic ionic liquid but also a significant increase in the proton acidity in this system as a function of the hydrogen pressure.

Electrochemical Investigation of Quinone Complexation by Lewis Acids in a Chloroaluminate Ionic Liquid

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Silica Based Cocatalysts for Heterogeneous Olefin Dimerization and Ethene Polymerization Reactions with Nickel Complexes

AbstractWe have developed a new buffered silica‐based Lewis acid cocatalyst for olefin dimerization and polymerization reactions with nickel complexes. The Lewis acidities of EtAlCl2 and Et2AlCl‐modified silicas were adjusted by the addition of BiPh3 or N‐methylpyrrole buffers. The buffered heterogeneous cocatalysts were employed to activate nickel complexes for selective propene dimerization reactions to give dimers in 91 % yield. Buffer addition also reduced the rate of ligand abstraction from the catalytically active nickel center. In combination with a nickel diimine complex, ethene was polymerized to give 69 wt % polyethylene and 31 wt % oligomers. The polyethylene displayed a molecular mass of 154 kg mol−1 and a polydispersity index (PDI) of 3.26. The oligomers consisted of 93 % butenes, 46 % thereof being 1‐butene. Furthermore, triphenylbismuth‐buffered Lewis acidic chloroaluminate ionic liquids were coated on surface‐modified silica to yield a supported ionic liquid phase (SILP) system. Dimer selectivities of up to 94 % were obtained with the SILP system in nickel‐catalyzed propene dimerization reactions. The newly developed silica‐based cocatalysts provide promising new olefin dimerization systems suitable for fixed bed applications.

Electrochemical Investigation of Ketone Complexation by Lewis Acids in a Chloroaluminate Ionic Liquid

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Facile Synthesis of New Cationic Triphenylphosphine Derivatives and their Use for Propene Dimerization Reactions in Buffered Chloroaluminate Ionic Liquids

AbstractWe describe the facile synthesis of new, cationic triphenylphosphine derivatives containing para‐trimethylammonium substituents. The ionic phosphines were successfully employed in nickel‐catalyzed propene dimerization reactions in highly Lewis acidic chloroaluminate ionic liquids. Buffering of such liquids is achieved by an interaction of the Lewis basic phosphine with the Lewis acidic aluminum centers. The PAl interaction of triarylphosphines and tri‐tert‐butylphosphine with the highly acidic ionic liquid [1‐butyl‐3‐methylimidazolium]+ [Al2Cl7]− was monitored by 31P and 27Al NMR spectroscopy. Coupling of tri‐tert‐butylphosphine with 27Al resulted in an expected but unusual sextet in the 31P NMR spectrum and a doublet in the 27Al NMR spectrum.

Nickel‐Catalyzed Propene Dimerization Reactions in Triphenylbismuth‐Buffered Chloroaluminate Ionic Liquids: High Performance with Unconventional Cations

AbstractThe addition of triphenylbismuth (BiPh3) efficiently buffers Lewis acidic chloroaluminate ionic liquids over a wide range of compositions. Since the melting points of these ternary mixtures are lower compared to unbuffered chloroaluminate systems, the scope of cations for the formation of buffered room temperature ionic liquids is greatly extended. The buffered ionic liquids were used to activate nickel complexes for selective biphasic propene dimerization reactions. Lifetimes, selectivities and productivities of such dimerization catalysts could be adjusted by the choice of the cation and the composition. At lower reaction temperatures, the selectivities to give dimers increased significantly. Propene dimers were obtained with selectivities of up to 98%. A cation screening with 100 ammonium and phosphonium halide salts was performed. N‐Methylpyrrolidine hydrochloride gave the best results in terms of selectivity and lifetime. Propene dimerization reactions in BiPh3‐buffered chloroaluminate melts were catalyzed by various soluble nickel compounds with similar performances. The introduction of basic, sterically demanding tricyclohexylphosphine ligands led to higher degrees of branching, however, at the expense of lower dimer selectivities.

Low-temperature Electrodeposition of Aluminium from Lewis Acidic 1-Allyl-3-methylimidazolium Chloroaluminate Ionic Liquids

Lewis acidic 1-allyl-3- methylimidazolium chloroaluminate ionic liquids were used as promising electrolytes in the low-temperature electrodeposition of aluminium. Systematic studies on deposition process have been performed by cyclic voltammetry and chronoamperometry. The surface morphology and X-ray diffraction (XRD) patterns of deposits prepared at different experimental conditions were also investigated. It was shown that the nucleation density and growth rate of crystallites had a great effect on the structure of aluminium deposited. The crystallographic orientation of deposits was mainly influenced by temperature and current density. Smooth, dense and well adherent aluminium coatings were obtained on copper substrates at 10–25 mA·cm−2 and 313.2–353.2 K. Moreover, the current efficiency of deposition and purity of aluminium have been significantly improved, demonstrating that the ionic liquids tested have a prospectful potential in electroplating and electrorefining of aluminium.

Buffered Aluminum Chloride as a Highly Efficient Cocatalyst for Olefin Dimerization and Polymerization

AbstractA binary cocatalyst system based on simple aluminum chloride and weak Lewis bases such as triphenylbismuth or N‐methylpyrrole has been developed. A donor–acceptor interaction kept aluminum chloride dissolved in toluene or methylene chloride. The systems were investigated by use of 27Al NMR spectroscopy and were used as cocatalysts in nickel‐catalyzed dimerization and polymerization reactions of α‐olefins. Their Lewis acidities correlated to the line width of the 27Al NMR signals and were influenced by the solvent and the type and amount of buffer. For propene dimerization reactions, dimer selectivities of up to 95 % were achieved. Ethene was dimerized to give butenes (up to 92 %), of which 79 % were 1‐butene. With a Brookhart‐type nickel diimine complex, ethene was polymerized with a cocatalyst solely based on aluminum chloride. Up to 38 wt % of the reaction products were polyethylene with a typical molecular weight of 140 kg mol−1. The donor–acceptor interactions of triphenylbismuth and N‐methylpyrrole with aluminum chloride were successfully transferred to Lewis acidic chloroaluminate ionic liquids. Ethene was polymerized with a nickel diimine complex dissolved in buffered chloroaluminate ionic liquids in the absence of alkylaluminum groups.

ChemInform Abstract: Application of Chloroaluminate Ionic Liquid as Catalyst and Medium for the Dealkylation of Esters.

AbstractThe ionic liquid Py·HBr/AlCl3, the best among four chloroaluminate ionic liquids testet, can be reused six times without any loss of its activity.

Aluminium Nanowire Electrodes for Lithium-Ion Batteries

In this paper, we report on the fabrication of mechanically stable aluminium nanowire electrodes for application in lithium-ion batteries. The electrochemical synthesis of the nanowire electrodes was performed in the chloroaluminate ionic liquid 1-ethyl-3-methylimidazolium chloride [EMIm]Cl/AlCl3 (40:60 mol %) using polycarbonate templates. The fabricated nanowire electrodes exhibit high mechanical stability after 50 cycles of lithium deposition/stripping without significant disintegration of the nanowire structure. The mechanical stability and strong adhesion of the Al-nanowires with the electrodeposited Al-electrode can lead to long cycling life. The fabricated Al-nanowire electrodes deliver a capacity of 790 mAh g–1 at 1C-rate.

Synthesis of 1-Acetylpyrene via Friedel-Crafts Reaction Using Chloroaluminate Ionic Liquids as Dual Catalyst and Solvent

Synthesis of 1-Acetylpyrene via Friedel-Crafts Reaction Using Chloroaluminate Ionic Liquids as Dual Catalyst and Solvent

Catalytic coupling and cracking reactions of alkanes in Lewis acidic chloroaluminate ionic liquids enhanced by molecular oxygen

In the presence of molecular oxygen, [BMIM]+[Al2Cl7]− (BMIM = 1-butyl-3-methylimidazolium) ionic liquids catalyzed coupling reactions of cyclohexane and methylcyclohexane to give dimers and trimers. Further, conversions and reaction rates of n-heptane cracking and disproportionation reactions were strongly enhanced if an atmosphere of dry air was applied instead of an inert gas.

Heavy Metal with a Heavy Impact: Olefin Dimerization Reactions in Triphenylbismuth Buffered Chloroaluminate Ionic Liquids

AbstractThe addition of weak Lewis bases such as NPh3, PPh3, or BiPh3 (Ph=phenyl) to Lewis acidic chloroaluminate ionic liquids yielded efficient cocatalysts for nickel catalyst precursors in highly selective biphasic dimerization reactions of α‐olefins. Triphenylbismuth buffered systems were found to produce up to 96 % dimers from propene. Selectivities and activities were influenced by varying the compositions of the ionic liquids. Furthermore, buffer addition reduced the melting points of the resulting liquids. This effect allowed a screening of many different organic halide salts, which were found to strongly influence the lifetimes and selectivities of the corresponding biphasic olefin dimerization systems. An optimized system dimerized ethene, propene, 1‐butene, and 1‐hexene with high selectivities. It is even possible to recycle amines and buffers used for these compositions by a simple acid base extraction of the spent ionic liquid catalyst systems. We also proposed a mechanism for these NiII catalyzed selective olefin dimerization reactions in alkylaluminum free buffered chloroaluminate melts. The addition of small amounts of BiPh3 to an ionic liquid composition used in the commercial DIFASOL process increased the selectivity to give dimers from a biphasic propene dimerization reaction by 15 %.

Corrosion characteristics of nickel, copper, and stainless steel in a Lewis neutral chloroaluminate ionic liquid

Corrosion of nickel, copper, and 316 stainless steel in aluminum chloride/1-ethyl-3-methylimidazolium chloride ionic liquid (IL) is investigated by means of electrochemical techniques. SEM analyses are performed to examine the reaction mechanisms. While Ni shows good stability, Cu has high corrosion susceptibility in this IL. For 316 steel, pitting corrosion occurs at a lower potential than that of passivation. In the non-aqueous, low-oxygen, and high-ion-containing IL, the material corrosion properties are totally different from those found in conventional environments. Since ILs have found increasing potential in diverse applications, new corrosion prevention strategies are needed to overcome the IL-derived material corrosion problems.

Solubility Behaviour of TiCl4, ZrCl4, and HfCl4 in Chloroaluminate Ionic Liquids

AbstractThe solubility of NbCl5, TaCl5, TiCl4, ZrCl4, and HfCl4 in neutral [BMIM][AlCl4] (BMIM = 1‐butyl‐3‐methylimidazolium) was determined. While TiCl4 was immiscible with the neutral ionic liquid, 0.80 molar equivalents of ZrCl4 and stoichiometric amounts of HfCl4 dissolved in the melt at ambient temperature. The crystal structures and the unit cell parameters of [BMIM]2[Ti2Cl10], [BMIM]2[Zr2Cl10], and [PhNMe3][Hf2Cl9] were determined. [BMIM]2[Ti2Cl10], and [BMIM]2[Zr2Cl10] were crystallised from basic chloroaluminate melts. With a trimethylanilinium cation, [PhNMe3][Hf2Cl9] crystallised from an equimolar composition of PhNMe3Cl, AlCl3, and HfCl4. Obviously, HfCl4 abstracted a chloride ligand from [AlCl4]– to give highly Lewis acidic [Al2Cl7]– anions.

Modeling of Aluminium Deposition from Chloroaluminate Ionic Liquids

A finite-element model of the electrodeposition of aluminium from chloroaluminate ionic liquids is introduced. The purpose of this model is to give an explanation for the reasonable current densities that can be achieved in chloroaluminate ionic liquids despite the fact that the electrochemically active complexes are transformed into inactive complexes during the electrodeposition of aluminium. The obtainable current density in the electrodeposition from chloroaluminate ionic liquids strongly depends on the chemical rate constants for establishing the equilibrium . A high current (up to 3000 A m−2) was found for both high and low rate constants whereas a minimum current (200 A m−2) was found for intermediate rate constants due to kinetics and thermodynamics. The model is compared to experiments conducted in the ionic liquid AlCl3 - [C2mim]Cl (60/40 mol%) where [C2mim]Cl is 1-ethyl-3-methylimidazolium chloride.

Liquid-Phase Isobutane/Butene-Alkylation Using Promoted Lewis-Acidic IL-Catalysts

The effect of different promoters on activity and selectivity of Lewis-acidic chloroaluminate ionic liquid catalysts was studied for isobutane/2-butene alkylation. When tert-butyl halides are used as promoters, the active species of the alkylation reaction, which is the tert-butyl cation, is directly generated whereas upon catalysis with Bronsted-acid supported ionic liquids, this species is indirectly provided through a hydride shift between protonated 2-butene and isobutane. Experimental results both from batch and continuously operated liquid phase alkylation reactors indicate, that tert-butyl halides are able to speed up the reaction rate significantly and shift the C8-selectivity towards the desired high-octane trimethylpentanes (TMPs). However, secondary reactions like oligomerization and cracking could not be suppressed by the use of this additives and high deactivation rates in continuous opperation were observed. Suggestions are made, how the product composition is effected by the additive and how the promoted IL-catalyst system is deactivated with time on stream.

Application of chloroaluminate ionic liquid as catalyst and medium for the dealkylation of esters

Dealkylation of esters to carboxylic acids was performed using chloroaluminate ionic liquids (PyHBr/AlCl3, PyHCl/AlCl3, Me3NHCl/AlCl3, Et3NHCl/AlCl3) as catalyst and medium. The catalytic activity of PyHBr/AlCl3 (X(AlCl3) = 0.67) proved to be superior to the other three ionic liquids for the dealkylation of methyl benzoate with a conversion of 97% after 3 h at 140 °C. After easy separation from the products the ionic liquid PyHBr/AlCl3 could be reused six times without loss of its activity.