Supported Ionic Liquid Phase Research Articles

Selective recovery of indium from iron-rich solutions using an Aliquat 336 iodide supported ionic liquid phase (SILP)

Selective recovery of valuable metals from secondary (waste) sources is essential for better resource efficiency. However, low-grade waste streams typically have complex and variable compositions and low concentrations of valuable metals. Therefore, development of novel technologies, able to deal with these complex and variable waste streams, is necessary. In this work, we present a process for the separation and purification of indium from iron-rich matrix solutions making use of a supported ionic liquid phase (SILP). The SILP used in this study was synthesized by impregnating AmberliteXAD–16N with the iodide form of the quaternary ammonium salt Aliquat336. The SILP was characterized by infrared spectroscopy, elemental analysis, density, specific surface area and porosity and it was tested for the selective recovery of indium. Adsorption was preceded by the addition of an excess of iodide anions to the solution, to form indium iodide species, which were extracted to the ionic liquid of the SILP. A high selectivity for indium over iron could be achieved because iron iodide species are not stable in aqueous medium. The reaction kinetics and several adsorption parameters, including anion concentration, adsorbent mass, stripping and reusability of the adsorbent were investigated, using synthetic binary iron-indium solutions containing iron in large excess in comparison with indium, as is typically the case in low-grade ores or industrial process residues. Finally, the developed indium recovery process was validated on a real leachate of goethite residue. A pure indium solution of 49 mg L–1 was obtained with an indium-over-iron mass ratio of 7.9 and a selectivity factor equal to 5400.

Supported ionic liquid-palladium catalyst for the highly effective hydrochlorination of acetylene

Vinyl chloride monomer (VCM) is an important platform molecule for the manufacture of polyvinyl chloride (PVC) via the direct hydrochlorination route from acetylene. However it is plagued by the toxicity of the mercury chloride (HgCl2) catalyst. Here we show that a 0.5Pd-10IL/AC catalyst, working as an environmentally friendly and highly efficient catalyst in supported-ionic-liquid-phase (SILP) system, is an plausible alternative for the commercially used HgCl2 catalyst for acetylene hydrochlorination. It performs higher activity and more stable conversion than ionic liquid (IL)-free 0.5Pd/AC catalyst during a 10 h reaction. Furthermore, the low-loading 0.15Pd-10IL/AC catalyst demonstrates a stable catalytic performance with a negligible loss of C2H2 conversion after 500 h under typical industrial reaction conditions. After careful characterization of the catalysts and additional catalytic tests, we ascribe the IL influence on the activity and stability of the catalysts to the stabilization and dispersion of active Pd species in the IL layer, the possible coordination of the IL to the Pd atoms, and the confinement of Pd complexes within the pores supports. This efficient and stable non-mercury catalyst provides an opportunity for green route to large-scale vinyl chloride production.

Water-Tolerant Trifloaluminate Ionic Liquids: New and Unique Lewis Acidic Catalysts for the Synthesis of Chromane.

The first example of triflometallate ionic liquids, named in analogy to chlorometallate ionic liquids, is reported. Trifloaluminate ionic liquids, synthesized from 1-alkyl-3-methylimidazolium triflates and aluminum triflate, were characterized by multinuclear NMR spectroscopy and FT-IR spectroscopy, revealing the existence of oligonuclear, multiply-charged trifloaluminate anions, with multiple bridging triflate modes. Acceptor numbers were determined to quantify their Lewis acidity, rendering trifloaluminate ionic liquids as medium-strength Lewis acids (AN = ca. 65). Used as acidic catalysts in the cycloaddition of 2,4-dimethylphenol and isoprene (molar ratio 2:1) to prepare chromane, trifloaluminate systems outperformed literature systems, showing high activity (conversions 94–99%, selectivities 80–89%) and at low loadings (0.2 mol%) at 35°C. Using these new systems as supported ionic liquid phase (SILP) on multi-walled carbon nanotubes (ionic liquid loading 16 wt%) delivered a recyclable catalytic system, with activity enhanced with respect to the homogenous regime.

Oligomerization of light olefins in the presence of a supported Brønsted acidic ionic liquid catalyst

Oligomerization of C4-C5 olefins and olefin mixtures has been investigated in the presence of a supported ionic liquid phase (SILP) catalyst, obtained by the physisorption of 1-(4-sulfobutyl)-3-methylimidazolium trifluoromethanesulfonate on silica. Surface properties of the SILP phase were determined from the experimental data of their nitrogen adsorption/desorption isotherms. Fresh and spent catalyst were characterised by 13C- and 29Si-CP MAS NMR spectroscopy and thermogravimetric analysis. Reactivity of alkenes followed the awaited order of isobutene>but-1-ene>pent-1-ene. The main products of oligomerization of hydrocarbon mixtures, modelling the C4-C5 fraction of waste polyethylene cracking products, were isoolefins in the boiling point range corresponding to kerosene fraction components, which is applicable as jet fuel after hydrotreatment. Stability and recyclability of the catalyst could greatly be enhanced by a pretreatment of the fresh catalyst, carrying out an oligomerization experiment with pure isobutene.

Combined multi-step precipitation and supported ionic liquid phase chromatography for the recovery of rare earths from leach solutions of bauxite residues

Rare-earth elements (REEs) were efficiently recovered by a supported ionic liquid phase (SILP) after iron(III) precipitation from simulated bauxite residue (BR) leachates in sulfuric acid media, since leaching of BR with sulfuric acid is more feasible than leaching with other mineral acids. The SILP betainium sulfonyl(trifluoromethanesulfonylimide) poly(styrene-co-divinylbenzene) [Hbet-STFSI-PS-DVB] exhibits a high selectivity for the rare-earth elements (REEs) over other elements in acidic BR leachates. However, scandium(III) uptake by the [Hbet-STFSI-PS-DVB] from sulfuric acid leachates is difficult due to strong electrostatic interactions of small scandium(III) ions with sulfate anions. Sulfuric acid leachates generally contain high concentrations of base metal ions like iron(III) and this reduces the efficiency of the [Hbet-STFSI-PS-DVB] for uptake of REEs. Therefore, a precipitation step for iron(III) removal with aqueous ammonia solution was introduced, as a simple and economically viable pretreatment step of BR leachate, prior to the REEs recovery by the SILP. Iron(III) precipitation from sulfuric acid BR leachates increased the efficiency of purification by column chromatography. Additionally, scandium(III) phosphate precipitation, after iron(III) removal, was performed in order to compare and assess the optimum route for scandium(III) purification between the two common processes: selective precipitation and elution chromatography. After scandium(III) phosphate precipitation, the recovery and subsequent purification of the remaining REEs on the [Hbet-STFSI-PS-DVB] column were also examined, and resulted in a higher purity of these REEs.

Compatibility of supported ionic liquid phase catalysts under ultrasonication

Various supported ionic liquid phase (SILP) catalysts containing hexafluorophosphate anion have been prepared by covalent grafting of imidazolium ionic liquid in the matrix of cellulose, silica and Merrifield resin followed by anion metathesis reaction. The compatibility of SILP catalysts in the synthesis of 1,4-dihydropyridines under ultrasonication is investigated. The results revealed that SILP catalysts can be effectively used under ultrasonication without physical, chemical and structural changes as evidenced from various analytical techniques.

Reverse water gas shift reaction using supported ionic liquid phase catalysts

The reverse water–gas shift reaction (RWGSR) using a supported ionic liquid-phase (SILP) catalyst consisting of Ru catalyst, ionic liquid (1-butyl-3-methylimidazolium chloride ([C4mim]Cl)), and porous silica gel support, was investigated. The catalytic activity of the SILP catalyst toward RWGSR strongly depends on the kind of Ru catalyst and amount of IL. Among the three kinds of Ru catalysts ([RuCl2(CO)3]2, Ru3(CO)12, and RuCl3), [RuCl2(CO)3]2 exhibits the best catalytic activity. Brunauer–Emmett–Teller (BET) surface area analysis and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses of the SILP catalyst based on [RuCl2(CO)3]2 and [C4mim]Cl revealed that both the solvation of the active catalytic Ru species and the surface area of the ionic liquid phase strongly affect catalytic activity. Hence, these factors help to determine the optimum amount of [C4mim]Cl in the SILP catalyst. The resulting SILP catalyst, with an optimum constitution, exhibited greater catalytic activity than the homogeneous system in which the same amounts of [RuCl2(CO)3]2 and [C4mim]Cl were employed. Catalytically active Ru species during RWGSR in both systems were investigated by means of electrospray ionization-mass spectrometry (ESI-MS). Interestingly, the rate-determining step in the two systems was different, implying that the silica support lowers the activation energy of the protonation reaction in the catalytic cycle. Therefore, the facilitation of the RWGSR by a SILP catalyst system can be realized by good mass transport, derived from the large surface area, as well as the effect of the silica support on activation energy. Furthermore, 20 cycles of the RWGSR using the SILP catalyst were accomplished.

Continuous Flow Asymmetric Hydrogenation with Supported Ionic Liquid Phase Catalysts Using Modified CO2as the Mobile Phase: from Model Substrate to an Active Pharmaceutical Ingredient

The continuous flow asymmetric hydrogenation of (hetero)aromatic enamides has been realized using a Rh-Quinaphos catalyst immobilized in a supported ionic liquid phase (SILP) and employing supercritical CO2 modified with toluene (modCO2) as the mobile phase. This approach allows expansion of the scope of the original SILP/scCO2 system to nonvolatile substrates with poor solubility in pure CO2. The potential of a SILP catalyst in combination with modCO2 was demonstrated for an industrial case study using the continuous flow hydrogenation for the synthesis of a key intermediate of an active pharmaceutical ingredient (API) from AstraZeneca’s portfolio. Toluene was selected as the most promising modifier, and the influence of the ratio of modifier to CO2 was evaluated in detail. The catalyst support was found to play a major role for maintaining constant performance and the use of hydrophobic fluorous reverse-phase silica (FRP-SiO2) instead of dehydroxylated silica strongly enhanced the long-term stability un...

Chemoselective Supported Ionic-Liquid-Phase (SILP) Aldehyde Hydrogenation Catalyzed by an Fe(II) PNP Pincer Complex

A base-tolerant supported ionic-liquid-phase (SILP) system containing a well-defined hydride Fe(II) PNP pincer complex has been prepared, structurally characterized, and used as catalyst in the hydrogenation of aldehydes to alcohols. The new SILP catalyst, with the optimum pore filling, was highly active exhibiting TONs and TOFs of up to 1000 and 4000 h–1, respectively, under mild conditions (25 °C, 10–50 bar H2 pressure) without significant leaching of both the complex and the IL.

Supported ionic liquid phase (SILP) facilitated gas-phase enzyme catalysis – CALB catalyzed transesterification of vinyl propionate

The supported ionic liquid phase (SILP) technology has been used to immobilizeCandida Antarctica Lipase B(CALB) within a hybrid monolith.

Carbon-based SILP catalysis for the selective hydrogenation of aldehydes using a well-defined Fe(ii) PNP complex

In this work, the supported ionic liquid phase (SILP) method was applied for the immobilization of a newly developed, well-defined hydride Fe(ii) PNP pincer complex dissolved an in ionic liquid (IL) onto polymer-based spherical activated carbon.

Insight into the dispersion behavior of 1-butyl-3-methylimiazolium chloride confined in nanoscale pores of carbon materials.

It is important to understand the behaviour of ionic liquids (ILs) in nanoscale pores, as application of supported ionic liquid phase (SILP) materials has attracted much attention. The main intention of this investigation is to study the dispersion performance of ionic liquid on activated carbons with different surface oxygen groups. Several active carbons with diverse oxygenated surface groups were obtained by oxidation and reduction methods. All samples were impregnated with [Bmim]Cl at different loadings. The blocked porosity of ionic liquid on SILP materials mainly depends on the amount of ionic liquid and surface oxygen content. In addition, stability of the supported IL in water was tested by analyzing the leached amount of IL. We found that the supported IL is not easily leached from the interface of carbon with low amount of surface oxygen. This may be due to the high free π-electron density of oxygen-free supports, forming more CH–π bonds with H atoms at the C2 position of the acidic cation. In addition, we propose that dispersion of ionic liquid in the pores depends on the density of surface free π-electrons of carbon materials.

Improvement of imidazolium-based ionic liquids on the activity of ruthenium catalyst for acetylene hydrochlorination

Imidazolium-based Ionic Liquids (IBILs) were employed to synthesize Ru-based catalysts using the Supported Ionic Liquid Phase (SILP) technique for acetylene (C2H2) hydrochlorination, combining the characterizations of transmission electron microscopy (TEM), N2 adsorption-desorption (BET), thermogravimetric analysis (TGA), temperature-programmed desorption (TPD), and X-ray photoelectron spectra (XPS), etc. The optimal Ru10%[BMIM]BF4/AC catalyst achieved the C2H2 conversion of 98.9% and the selectivity to vinyl chloride monomer (VCM) of 99.8% under the temperature of 170°C and the C2H2 gas hourly space velocity (GHSV) of 180h−1. Further, other IBILs with different anions were chosen to fabricate Ru-based catalysts, and the catalysts showed high activity and selectivity similar with Ru10%[BMIM]BF4/AC catalyst. It is demonstrated that IBILs additives can significantly improve the dispersion of ruthenium species and prevent the appearance of coke deposition owing to the interactions between Ru species and [BMIM]BF4. Moreover, the oxygen-containing functional groups on the carbon support are associated with the interactions among Ru species and [BMIM]BF4.

Trimerization of ethylene catalyzed by Cr-based catalyst immobilized on the supported ionic liquid phase

Two types of heterogeneous catalysts based on bis(2-dodecylsulfanyl-ethyl)-amine.CrCl3 complex immobilized into the modified SBA-15 channels has been synthesized. For the first catalyst [Cr-SNS@SBA-15(700)], the pristine mesoporous silica was subjected to dehydroxylation at 700 °C while another catalyst [Cr-SNS-IL(BF4)@SBA-15] was prepared using supported ionic liquid phase (SILP) with tetrafluouroborate (BF4) as a counter ion. The materials were characterized by transmission electron microscopy (TEM), nitrogen adsorption–desorption analysis, thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, elemental analysis (CHNS), X-ray diffraction (XRD) and UV-Visible spectroscopy. The catalytic activity of both catalysts was then investigated for ethylene trimerization reaction under various reaction conditions by emphasizing the use of low catalyst loading and Al:Cr molar ratio. The studies indicated that Cr-SNS-IL(BF4)@SBA-15 catalyst showed higher activity than either Cr-SNS@SBA-15(700) or homogeneous Cr-SNS under exactly the same reaction conditions. It was found that supported BF4− ions play a crucial role in the improvement of catalytic activity and selectivity to 51079 and > 99%, respectively. This study would open a new window in the design of types of supported catalysts for ethylene oligomerization mediated by more appropriate catalytic activity and selectivity.

Highly Selective Continuous Gas‐Phase Methoxycarbonylation of Ethylene with Supported Ionic Liquid Phase (SILP) Catalysts

AbstractSupported ionic liquid phase (SILP) technology was applied for the first time to the Pd‐catalyzed continuous, gas‐phase methoxycarbonylation of ethylene to selectively produce methyl propanoate (MP) in high yields. The influence of catalyst and reaction parameters such as, for example, ionic liquid loading, metal concentration, and ligand loadings was studied, and in particular the SILP catalyst activity and stability was found to be strongly dependent on the ligand to metal ratio.

Removal of Multiple Contaminants from Water by Polyoxometalate Supported Ionic Liquid Phases (POM-SILPs).

The simultaneous removal of organic, inorganic, and microbial contaminants from water by one material offers significant advantages when fast, facile, and robust water purification is required. Herein, we present a supported ionic liquid phase (SILP) composite where each component targets a specific type of water contaminant: a polyoxometalate-ionic liquid (POM-IL) is immobilized on porous silica, giving the heterogeneous SILP. The water-insoluble POM-IL is composed of antimicrobial alkylammonium cations and lacunary polyoxometalate anions with heavy-metal binding sites. The lipophilicity of the POM-IL enables adsorption of organic contaminants. The silica support can bind radionuclides. Using the POM-SILP in filtration columns enables one-step multi-contaminant water purification. The results show how multi-functional POM-SILPs can be designed for advanced purification applications.

Stabilizing Au(III) in supported-ionic-liquid-phase (SILP) catalyst using CuCl2 via a redox mechanism

High-valent Au(III) complexes have attracted much attention as catalysts in many reactions. Nevertheless Au(III) catalysts suffer from instability of the oxidized metal complexes during preparation and use. Herein, we demonstrated that Au(III) catalysts can be stabilized against reduction to metallic Au0 by modifying supported-ionic-liquid-phase-stabilized Au(III) catalyst with CuCl2. It was found that the that reduced Au0 could be re-oxidized in situ to Au3+ species by CuCl2 during the reaction and further stabilized by the electron transfer from Cu to these active species. When evaluated in the acetylene hydrochlorination reaction, the Au-Cu-IL/AC catalyst displayed an excellent specific activity with the turnover frequency (TOF) as high as 168.5h−1 and more than 99.8% selectivity for the product, vinyl chloride (VCM). Furthermore, the Au-Cu-IL/AC catalyst demonstrated a stable catalytic performance with a negligible loss of C2H2 conversion after 500h under typical industrial reaction conditions for acetylene hydrochlorination. Therefore, the findings of this work provide an efficient approach for designing stable high-valent metals for long-term operation, and also pave the way for the application of Au-Cu-IL/AC catalyst in industrial VCM production.

Detailed Investigation of the Mechanism of Rh-Diphosphite Supported Ionic Liquid Phase (SILP)-Catalyzed 1-Butene Hydroformylation in the Gas Phase via Combined Kinetic and Density Functional Theory (DFT) Modeling Studies

A detailed kinetic investigation of the gas-phase continuous hydroformylation of 1-butene has been carried out. The supported ionic liquid phase (SILP) catalyst was based on a Rh-diphosphite, the ionic liquid [EMIM][NTf2], and silica support material. Based on the established Wilkinson mechanism, the hyperbolic rate expressions were used to fit the experimental results. While the hydroformylation could be modeled with high accuracy, the hydrogenation and isomerization trends could not be reproduced by the given rate expressions. An alternative reaction mechanism was developed and allowed an excellent fit of experimental data by the new reaction rate expressions. Initial steps of the mechanism were studied using density functional theory (DFT) calculations.

Recovery of scandium(iii) from diluted aqueous solutions by a supported ionic liquid phase (SILP)

Recovery of scandium from secondary resources like bauxite residue by a supported ionic liquid phase (SILP).

Elemental Mercury Capture from Flue Gas by a Supported Ionic Liquid Phase Adsorbent

As promising functional materials, ionic liquids have been widely used in flue gas purification and separation. Previous studies reported that ionic liquid based mixtures can be used for mercury removal due to their high economic efficiency and environmental friendliness. In comparison with ionic liquid based mixtures, a supported ionic liquid phase (SILP) adsorbent shows significantly improved mercury removal performance because of its greatly enhanced gas/liquid interfacial area. In this study, a novel supported task-specific ionic liquid phase adsorbent [C4mim][FeCl4]–SiO2 was prepared for high efficiency elemental mercury capture from flue gas. The Hg0 removal performance was investigated in a bench-scale fixed bed reactor, and the reaction mechanism was proposed based on the temperature programmed desorption (TPD) test. The results showed that Hg0 removal was mainly due to the oxidation by [C4mim][FeCl4]. The addition of [C4mim][FeCl4] on SiO2 in a certain composition range enhanced the Hg0 removal performance, and the optimized ionic liquid loading is 30%. The Hg0 removal by the adsorbent was favored at higher temperatures. TPD results showed that the mercury compound formed on the adsorbent was HgCl2. The Hg0 removal mechanism involves combined physisorption and chemisorption, which consists of Hg0 oxidation to HgCl2 by the ionic liquid and physical adsorption of HgCl2 on the porous adsorbent.