Supported Ionic Liquid Phase Research Articles

Effect of SILPs on the Vulcanization and Properties of Ethylene-Propylene-Diene Elastomer.

Ionic liquids (ILs) are increasingly used in elastomer technology due to unique physico-chemical properties, which are stable at the temperature of preparation and during processing of rubber compounds. The latest IL application concept is supported ionic liquid-phase (SILP) materials, where an IL film is immobilized on the solid phase. The main aim of this work was studying the influence of IL immobilized on the surface of solid supports, such as silica and carbon black, on the vulcanization process, mechanical properties, and thermal behavior of ethylene–propylene–diene (EPDM) elastomer. Application of the SILP materials enabled the control of EPDM vulcanization without deterioration of the crosslink density, damping properties, thermal stability, and resistance of the vulcanizates to thermo-oxidative aging. Slight improvements in the tensile strength and hardness of the vulcanizates were observed.

Double carbonylation of iodoarenes in the presence of a pyridinium SILP-Pd catalyst

The efficiency of a palladium catalyst, immobilised on a supported ionic liquid phase (SILP) with adsorbed 1-butyl-4-methylpyridinium chloride, was investigated in aminocarbonylation reactions. Double carbonylation was found to be the main reaction using different iodoarenes and aliphatic amines as substrates. Application of aniline derivatives as nucleophiles led to the exclusive formation of substituted benzamides. The stabilisation effect of the adsorbed pyridinium ionic liquid was compared to that of imidazolium and phosphonium derivatives. It was proved that the pyridinium SILP-palladium catalyst could be reused in at least 10 cycles. Recyclability was tested in five successive runs for all of the substrates.

Gas dehydration using the ionic liquid [EMIM][MeSO3] supported on silica gel – Structural and water vapor sorption properties

Structural and water vapor sorption properties of supported ionic liquid phase (SILP) materials, here of the ionic liquid [EMIM][MeSO3] coated on silica gels, were studied. The distribution of the IL over the silica supports is uniform. The porosity of the SILPs shows good agreement with expected values based on the density of the pure IL. The water sorption in pure [EMIM][MeSO3] as well as by the SILPs can be described by Guggenheim-Anderson-de Boer sorption isotherms. If the silica surface is covered by at least a complete monolayer of IL, the surface has no noticeable effect on the sorption capacity, and the capacity of the SILP corresponds to that of the pure IL until capillary condensation occurs. SILPs are promising candidates for gas dehydration, as the water sorption capacity per mass of silica is about six times higher compared to uncoated silica.

Photocatalytic Degradation of Methyl Orange by Magnetically Retrievable Supported Ionic Liquid Phase Photocatalyst.

A magnetically retrievable ferrocene appended supported ionic liquid phase (SILP) photocatalyst containing a molybdate anion has been synthesized and characterized by Fourier transform infrared, X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray diffraction, energy dispersive spectroscopy, and vibrating sample magnetometer analysis. The optical properties of the photocatalyst were probed by photoluminescence and UV–vis diffuse reflectance spectroscopy. The discharge of undesirable dye effluents from textile industrial plants in the environment is the major concern of environmental pollution and toxicity. In this context, we employed the as-prepared SILP photocatalyst for degradation of methyl orange (MO) under UV light (365 nm) irradiation, and subsequently, recycling studies were performed. The histological alteration in gills of the fish is employed as a tool for monitoring toxins in the environment. In view of this, the histo-toxicological assessment on freshwater fish Tilapia mossambica gills asserted the damage of secondary gill lamellae due to MO. Conversely, structural modifications in the gill architecture were not observed by virtue of photodegraded products confirming that the degraded product is nontoxic in nature. Additionally, the normal behavior of fishes on exposure to photodegraded products reveals that research findings are beneficial for the aquatic ecosystem.

Magnetic Nanoparticle Supported Ionic Liquid Phase Catalyst for Oxidation of Alcohols

A new magnetic nanoparticle supported ionic liquid phase (SILP) catalyst containing perruthenate anions was prepared by a multistep procedure. The various analytical techniques such as FT-IR spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, thermogravimetric analysis, energy dispersive X-ray analysis, and vibrating sample magnetometer analysis ascertained the successful formation of catalyst. The performance of a magnetically retrievable SILP catalyst was evaluated in the selective oxidation of alcohols. The split test and leaching studies of the SILP catalyst confirmed its heterogeneous nature. In addition, the reusability potential of SILP catalyst was also investigated which revealed its robust activity up to six consecutive cycles.

Elucidating the ionic liquid distribution in monolithic SILP hydroformylation catalysts by magnetic resonance imaging.

Monolithic silicon carbide supported ionic liquid-phase (SILP) Rh-catalysts have very recently been introduced for gas-phase hydroformylation as an important step toward industrial upscaling. This study investigates the monolithic catalyst system in combination with different impregnation procedures with non-invasive magnetic resonance imaging (MRI). The findings were supported by X-ray microtomography (micro-CT) data of the monolithic pore structure and a catalytic performance test of the catalyst system for 1-butene gas-phase hydroformylation. MRI confirmed a homogeneous impregnation of the liquid phase throughout the full cross-section of the cylindrical monoliths. Consistent impregnations from one side to the other of the monoliths were achieved with a stabilizer in the system that helped preventing inhomogeneous rim formation. External influences relevant for industrial application, such as long-term storage and temperature exposure, did not affect the homogeneous liquid-phase distribution of the catalyst. The work elucidates important parameters to improve liquid-phase catalyst impregnation to obtain efficient monolithic catalysts for industrial exploitation in gas-phase hydroformylation as well as other important industrial processes.

Peroxotungstate-Based Ionic Hybrid as a Triphase Heterogeneous Catalyst for Efficient Benzyl Alcohol Oxidation Under Mild Conditions

Supported ionic-liquid-phases (SILPs) were synthesized via reaction of 1-methyl-3-(3-triethoxysilylpropyl)imidazolium hexafluorophosphate (ImCl-PF6) with SBA-15 and then peroxotungstate molecules were immobilized on SILPs. The resulting material (W-ImCl-PF6-SBA-15) was characterized via 29Si MAS NMR to detect the chemical environment around Si and its textural and thermogravimetric behavior were determined. To obtain insight into the role of ImCl-PF6 during catalysis, an ImCl-PF6-free catalyst (W/SBA-15) was also synthesized. W-ImCl-PF6-SBA-15 and W/SBA-15 were investigated as catalysts for benzyl alcohol oxidation, as a model reaction, under solvent-free conditions with H2O2.The presence of ImCl-PF6 was crucial for obtaining excellent catalytic activity, and W-ImCl-PF6-SBA-15 showed higher activity and stability than these of W/SBA-15. Optimized reaction conditions were employed to several selected alcohols oxidation and, remarkably, excellent aldehydes selectivity was achieved. The importance of ImCl-PF6-functionalized SBA-15 was evidenced via recycling experiments of benzyl alcohol oxidation, and W-ImCl-PF6-SBA-15 was recycled for ten reaction runs without significant change in benzyl alcohol conversion, benzaldehyde selectivity, and tungsten content.

Unraveling Toluene Conversion during the Liquid Phase Hydrogenation of Cyclohexene (in Toluene) with Rh Hybrid Catalysts

Monitoring hydrogen consumption has allowed studying the progress of the liquid phase hydrogenation of cyclohexene in toluene with Rh SILP (supported ionic liquid phase) catalysts prepared by the immobilization of the [{RhCl(cod)}2] complex on different carbon materials. An excess of hydrogen consumption with respect to the required amount for cyclohexene hydrogenation was registered and related with the solvent (toluene) hydrogenation. The study carried out led to unraveling the extent of toluene hydrogenation and to determining if the rate of this reaction is affected by the properties of the carbon material used as support. The results revealed that the Rh SILP catalysts we prepared showed acceptable toluene conversion, with 100% selectivity to the total hydrogenated product, and that the effect of the carbon support is the same as for cyclohexene hydrogenation.

Influence of the Ionic Liquid on the Activity of a Supported Ionic Liquid Phase FeII Pincer Catalyst for the Hydrogenation of Aldehydes.

The catalytic hydrogenation of different aldehydes to the corresponding alcohols was investigated using an FeII hydride pincer complex as catalyst in the supported ionic liquid phase (SILP) reaction mode. Two different ionic liquids of the type [X4441][NTf2] with X=N or P were applied with mesoporous silica gel as support, which was coated first with a chemisorbed monolayer of the corresponding modified IL to remove acidic surface OH‐groups and to prevent IL leaching. Quantitative conversion with turn‐over frequencies in the order of 1000 h– 1 were obtained for various aromatic and heteroaromatic aldehydes and highly selective aldehyde reduction was observed also for substrates containing reducible C=C bonds. Aldehydes with longer aliphatic chains or cycloalkyl substituents, however, showed no conversion here, in contrast to a previous study with an imidazolium‐based ionic liquid. These differences were ascribed primarily to differences in substrate/ionic liquid interactions. Whereas [N4441][NTf2] and [P4441][NTf2] gave essentially identical results for different substrates in single‐batch reactions, prolonged use of the catalyst in repeated reaction cycles lead to a quick drop‐off in catalyst activity in [P4441][NTf2], but a continuous, quantitative conversion in [N4441][NTf2].

Brønsted acidic SILP-based catalysts with H3PMo12O40 or H3PW12O40 in the oxidative desulfurization of fuels

In this manuscript novel heterogeneous catalysts for fuel desulfurization via peroxide oxidation are reported. The obtained catalysts combine high catalytic activity and stability with perfect synthetic availability, their composition and structure were ascertained. The catalysts represent supported ionic liquid phases (SILPs): Brønsted acidic ILs, namely 4-(3′- ethylimidazolium)-butanesulfonate, with two heteropolyacids (HPA) (sulfated ionic liquid protonated by H3PMo12O40 or H3PW12O40). Silica and γ-Al2O3 were used as support materials. These compositions ensure higher stability of heteropolyanions and make the catalyst stable over several successive oxidation cycles. The most active catalyst based on phosphomolybdic acid provides a high conversion rate for thiophene, thioanisole, and dibenzothiophene (turn over frequency of about 150–1200 h−1 per mole of HPA). Another important benefit of the reported systems is the desulfurization of diesel fuel with a very high efficiency (residual amount of sulfur <10 ppm) under mild conditions.

CO2 Capture by Supported Ionic Liquid Phase: Highlighting the Role of the Particle Size

CO2 capture by fixed-bed sorption has been evaluated using Supported Ionic Liquid Phase (SILP) based on the ionic liquid 1-butyl-3-methylimidazolium acetate ([bmim][acetate]). The SILP sorbent was prepared with three remarkably different mean particle sizes and characterized by porous texture, morphology, thermal stability, and elemental composition. The thermodynamics and kinetics of the CO2 capture process has been studied, testing the effects of SILP particle size, sorption temperature, gas flow rate, and CO2 partial pressure. The CO2 sorption isotherms at different temperatures were obtained by gravimetric measurements, revealing that the equilibrium sorption capacity is only due to the IL incorporated on the silica support of SILP. The experimental isotherms were successfully fitted to the Langmuir–Freundlich model. Fixed-bed experiments of CO2 capture were carried out to evaluate the performance of the SILP sorbents at different operating conditions. All the breakthrough curves were well described b...

Selective recovery of germanium from iron-rich solutions using a supported ionic liquid phase (SILP)

A supported ionic liquid phase (SILP) was developed to selectively recover germanium from iron-rich aqueous solutions. The SILP was synthesised by impregnating Amberlite XAD-16N with Aliquat 336, a mixture of quaternary ammonium salts. Characterisation was performed using elemental analysis, infrared spectroscopy, specific surface area, porosity and density measurements. Adsorption was preceded by the addition of citrate anions to the iron-rich aqueous solutions, to form germanium(IV) citrate complexes, which were extracted to the ionic liquid layer of the SILP. The reaction kinetics and several adsorption parameters, including pH, anion concentration and adsorbent mass, were investigated using synthetic single-element germanium solutions. The coordination of germanium(IV) to the citrate ligands was elucidated using Extended X-ray Absorption Fine Structure (EXAFS). Subsequently, the optimal adsorption parameters were tested on a multi-element solution with elemental concentrations resembling those of a leachate of goethite residue from the zinc industry. A high selectivity for germanium over iron could be achieved. Finally, the stripping and the reusability of the SILP were studied. A germanium solution of 44 mg·L−1 was obtained with a germanium-over-iron mass ratio of 39. This corresponds to a selectivity factor equal to 34 400, demonstrating the high potential of the reported process.

Highly Effective Supported Ionic Liquid-Phase (SILP) Catalysts: Characterization and Application to the Hydrosilylation Reaction

Organosilicon compounds, because of their unique properties, are widely used in a variety of organic processes, and thus the constant improvement of current methods is still needed. We present slurry-phase hydrosilylation reactions using novel supported ionic liquid-phase (SILP) catalysts containing rhodium complexes immobilized in four phosphonium ionic liquids (ILs) on silica support. The obtained new SILP catalysts were analyzed by infrared technique, low-temperature nitrogen physisorption at 77 K, and scanning electronic microscopy with energy-dispersive X-ray spectroscopy to provide structural information on these materials. Moreover, the catalytic activity in hydrosilylation reactions was evaluated and compared with the catalytic activity of rhodium catalysts dissolved in the same ILs when using a biphasic reaction system (IL/catalyst as one phase and mixture of substrates as a second phase). The rhodium-based SILP catalysts proved to be much more efficient than when used in a biphasic system compos...

Improving the performance of supported ionic liquid phase (SILP) catalysts for the ultra-low-temperature water–gas shift reaction using metal salt additives

Addition of CuCl to supported ionic liquid phase (SILP) catalysts enhances the activity in the low temperature water–gas shift (WGS) reaction.

Multi-walled carbon nanotube-based composite materials as catalyst support for water-gas shift and hydroformylation reactions.

In times of depleting fossil fuel reserves, optimizing industrial catalytic reactions has become increasingly important. One possibility for optimization is the use of homogenous catalysts, which are advantageous over heterogeneous catalysts because of mild reaction conditions as well as higher selectivity and activity. A new emerging technology, supported ionic liquid phase (SILP), was developed to permanently immobilize homogeneous catalyst complexes for continuous processes. However, these SILP catalysts are unable to form freestanding supports by themselves. This study presents a new method to introduce the SILP system into a support made from multi-walled carbon nanotubes (MWCNT). In a first step, SILP catalysts were prepared for hydroformylation as well as low-temperature water–gas shift (WGS) reactions. These catalysts were integrated into freestanding microtubes formed from MWCNTs, with silica (for hydroformylation) or alumina particles (for WGS) incorporated. In hydroformylation, the activity increased significantly by around 400% when the pure MWCNT material was used as SILP support. An opposite trend was observed for WGS, where pure alumina particles exhibited the highest activity. A significant advantage of the MWCNT composite materials is the possibility to coat them with separation layers, which allows their application in membrane reactors for more efficient processes.

Ionic liquids as an enabling tool to integrate reaction and separation processes

This tutorial review highlights representative examples of ionic liquid (IL)-based (bio)catalytic systems integrating reaction and separation, as a tool for the development of sustainable chemical processes (e.g.IL/scCO2biphasic reactors, membrane reactors, nanodrop systems, microfluidic devices, supported IL phases, sponge-like ILs,etc.).

Fifteen Years of Supported Ionic Liquid Phase-Catalyzed Hydroformylation: Material and Process Developments

This review describes the development of supported ionic liquid phase (SILP) materials as novel hydroformylation catalysts. Ligand-modified rhodium catalysts can be immobilized in a thin film of ionic liquid, which itself is dispersed on a porous material. The solid SILP catalysts have been improved with respect to activity, selectivity, and stability. In addition, their applicability in continuous gas-phase processes opens new opportunities for improved chemical production routes.

Mechanism of the Water-Gas Shift Reaction Catalyzed by Efficient Ruthenium-Based Catalysts: A Computational and Experimental Study.

Supported ionic liquid phase (SILP) catalysis enables a highly efficient, Ru-based, homogeneously catalyzed water-gas shift reaction (WGSR) between 100 °C and 150 °C. The active Ru-complexes have been found to exist in imidazolium chloride melts under operating conditions in a dynamic equilibrium, which is dominated by the [Ru(CO)3 Cl3 ]- complex. Herein we present state-of-the-art theoretical calculations to elucidate the reaction mechanism in more detail. We show that the mechanism includes the intermediate formation and degradation of hydrogen chloride, which effectively reduces the high barrier for the formation of the requisite dihydrogen complex. The hypothesis that the rate-limiting step involves water is supported by using D2 O in continuous catalytic WGSR experiments. The resulting mechanism constitutes a highly competitive alternative to earlier reported generic routes involving nucleophilic addition of hydroxide in the gas phase and in solution.

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.