Composite Ionic Liquid Research Articles

Polyurethane/poly (Ionic Liquids) Cellulosic Composites and their Evaluation for Separation of CO2 from Natural Gas

The development of both versatile and inexpensive sorbents for CO2/CH4 separation has become one of the greatest challenges to the environment and natural gas processing. This study reports the preparation and characterization of polyurethane (PU)/ cellulose based poly(ionic liquid)(CPIL) composites for CO2/CH4 separation. PU matrix was reinforced with CPIL in the range of 10-30 wt%. Several characterization techniques (TGA, DSC, DMTA and FESEM ) were used to study the physical properties of composites when the PU matrix is reinforced with cellulose based poly (ionic liquids) (CPIL) up to 30%. CO2 sorption, reusability and CO2/CH4 selectivity were assessed by pressure-decay technique. Results showed that CPIL addition in PU matrix promoted the increase in both thermal stability and mechanical properties when compared to PU. The best result for CO2 sorption (35.0 mgCO2/g) was obtained for PU/CPIL-TBP 10% which presented a higher sorption value when compared to PU (24.1 mgCO2/g) and PU/CELLULOSE 10% (26.8 mgCO2/g). PU/CPIL-TBP 20% demonstrated higher CO2/CH4 selectivity. PU/CPIL composites appear as promissory materials for CO2 capture. These compounds combine the benefits of ionic liquids (ILs) (high ionic conductivity, chemical and thermal stability) and cellulose (thermal stability) with PU properties (mechanical stability, processing and tunable macromolecular design).

Towards Biohydrogen Separation Using Poly(Ionic Liquid)/Ionic Liquid Composite Membranes.

Considering the high potential of hydrogen (H2) as a clean energy carrier, the implementation of high performance and cost-effective biohydrogen (bioH2) purification techniques is of vital importance, particularly in fuel cell applications. As membrane technology is a potentially energy-saving solution to obtain high-quality biohydrogen, the most promising poly(ionic liquid) (PIL)–ionic liquid (IL) composite membranes that had previously been studied by our group for CO2/N2 separation, containing pyrrolidinium-based PILs with fluorinated or cyano-functionalized anions, were chosen as the starting point to explore the potential of PIL–IL membranes for CO2/H2 separation. The CO2 and H2 permeation properties at the typical conditions of biohydrogen production (T = 308 K and 100 kPa of feed pressure) were measured and discussed. PIL–IL composites prepared with the [C(CN)3]− anion showed higher CO2/H2 selectivity than those containing the [NTf2]− anion. All the membranes revealed CO2/H2 separation performances above the upper bound for this specific separation, highlighting the composite incorporating 60 wt % of [C2mim][C(CN)3] IL.

Lignosulfonate/Dicationic Ionic Liquid Composite as a Task-Specific Catalyst Support for Enabling Efficient Synthesis of Unsymmetrical 1,3-Diynes with A Low Substrate Ratio

In Glaser heterocoupling reactions, one of the alkyne precursors have to be used in five to ten times of excess. This not only wasted the organic substrate, but also decreased the catalytic efficiency of the metal catalysts. To solve this problem, we prepared a lignosulfonate/dicationic ionic liquid composite via ion exchange process. The thereby obtained materials can be used as catalyst supports for preparing heterogeneous Cu-based catalysts. The supports and the catalysts were characterized by many physicochemical methods including FT-IR, elemental analysis (EA), FSEM, FTEM, XPS, and TG. Interestingly, the catalyst can enrich the alkynol component in the reaction system, thus enabling Glaser heterocoupling reactions of alkynols and phenylacetylenes to proceed well with a low substrate ratio. The substrate scope of the Glaser heterocoupling reaction, enriching effect of the composite support for the alkynol component, and recyclability of the catalyst were also investigated.

High‐performance natural rubber latex composites developed by a green approach using ionic liquid‐modified multiwalled carbon nanotubes

ABSTRACTThe effect of multiwalled carbon nanotubes (MWCNTs) modified by a hydrophilic ionic liquids (ILs), including 1‐ethyl‐3‐methylimidazolium bromide and 1‐hexyl‐3‐methylimidazolium bromide, was studied. The obtained water‐suspensible carbon nanotubes (CNTs) were still homogeneously distributed in water a month after sonication. The microstructural development of filler networks and the uniform dispersion of MWCNTs in the presence of IL were analyzed by TEM. The apparent physical (cation–π/π–π) interaction between the MWCNTs and the IL was characterized by Raman spectroscopy, DSC, and TGA. Furthermore, high‐performance composites of natural rubber latex (NRL) and CNTs modified with IL were obtained by the liquid latex blending method. The CNTs were homogeneously distributed in the matrix and CNT–ILs improved the fatigue resistance and mechanical properties of the NRL/CNT–IL composites. This study demonstrates a simple and eco‐friendly approach to develop multifunctional advanced materials based on IL‐modified MWCNT elastomer composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46588.

Molecular analysis of selective gas adsorption within composites of ionic polyimides and ionic liquids as gas separation membranes

The CO2 separation characteristics of ionic polyimides (i-PIs) are modeled using molecular dynamics simulations in combination with grand canonical Monte Carlo calculations. The performance of neat i-PI systems is evaluated, as well as composite structures containing both i-PIs and various ionic liquids (ILs). The i-PI + IL composites are based on combinations of 1-n-butyl-3-methylimidazolium ([C4mim+]) cations with three common molecular anions: (bis(trifluoromethylsulfonyl)imide ([Tf2N−]), tetrafluoroborate ([BF4−]), and hexafluorophosphate ([PF6−]). It is found that 50 mol% IL inclusion can increase CO2/CH4 selectivity by 16% in [BF4−]-based materials and by 36% in [PF6−]-based materials from mixtures of 5% CO2/95% CH4. While the [BF4−]-based system shows higher CO2/CH4 selectivity, the [Tf2N−]-based system shows higher CO2/N2 gas selectivity. A comprehensive structural analysis (fractional free volume (FFV), pore size distribution, surface area, etc.) is used to highlight the underlying differences among the different i-PI + IL systems that lead to the different adsorption properties.

Preparation of poly (vinyl alcohol)/ionic liquid composites with improved processability and electrical conductivity for fused deposition modeling

This work aims to realize the fused deposition modeling (FDM) process of poly (vinyl alcohol) (PVA), which is a multi-hydroxyl polymer with good comprehensive properties. However, achieving the FDM process for PVA is quite challenging due to its narrow thermal processing window. To address this problem, an ionic liquid (IL) was introduced to improve the thermal processability of PVA. The materials, the FDM process and properties of the FDM products were systematically evaluated. The results indicated that the PVA/IL composites exhibited significantly improved thermal processing properties. The PVA/IL filament prepared with a suitable viscosity and modulus ratio showed good printability. The tensile strength of the FDM parts increased from 8.7 MPa to 13.6 MPa due to the difference in the interlayer bond strength when the nozzle temperatures ranged from 170 °C to 200 °C. The zero shear rate viscosity, the relaxation time and the surface tension at different printing temperatures were analyzed and provide theoretical insight into the diffusion of polymer chains at the interface during the FDM process. Interestingly, the 3D printed composites were flexible and exhibited tailored electrical conductivity with a strong dependence on the printing temperature, revealing the potential to be functional parts in the field of flexible electronics.

Natural Fiber Welding with Novel Ionic Liquids

Natural Fiber Welding (NFW) is a versatile biopolymer manipulation process that uses ionic liquids (ILs) to disrupt the intermolecular interactions between polymer strands. NFW enables the reconfiguration of biopolymer material structure as well as the integration of functional materials within the biopolymer matrix. This process is thought to require ILs that have both chaotropic anions and hydrogen bond donating cations, with past work focusing on ILs that have been shown to be solvents capable of the full dissolution of biopolymer materials (e.g. cotton, silk, linen, and keratin). In the present work, we looked to expand the suite of ILs that could be used for NFW by investigating the impact of IL structure and composition on the NFW process with emphasis placed on studying the impact of cation structure. Fluorescently labeled cotton yarns were exposed to selected ILs under controlled time, temperature, and atmospheric conditions. Confocal fluorescence microscopy and scanning electron microscopy were used to evaluate the level of welding in the IL-treated cotton yarns, and atomic force microscopy and tensile strength testing were used to evaluate changes in the physical properties of the welded yarns. Initial results indicate that NFW may not require the use of an IL with a hydrogen bond donating cation as long as a chaotropic anion is present.

Automation of ionic liquid enhanced membrane bag-assisted-liquid-phase microextraction with liquid chromatography-tandem mass spectrometry for determination of glucocorticoids in water

A novel fully automated liquid-phase microextraction (LPME) procedure making use of a conical polypropylene membrane bag to hold the solvent, coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with positive electrospray ionisation was developed to determine glucocorticoids (including cortisol, cortisone, dexamethasone, prednisone and prednisolone) in water. The solvent was a synergistic mixture of 10% v/v of ionic liquid, 1-butyl-3-methylimidazolium methylsulfate in n-octanol. The use of ionic liquid as an additive enhanced the extraction performance due to the favourable ionic and hydrogen bonding interactions with the analytes. Different experimental parameters such as the types of organic solvent as supported liquid membrane and ionic liquid, various composition of ionic liquid, volume of extractant phase, agitation time and speed, temperature of extraction were investigated. Under the most favourable extraction conditions, enrichment factors of 49.4–83.1 were obtained for the target compounds with relative standard deviations of <10%. The intra-day repeatability of the method ranged from 4.23 to 6.42% and the inter-day reproducibility ranged from 6.87 to 9.20%. Good linearity 0.05–50 ng mL−1 (prednisolone) and 0.1–50 ng mL−1 (all other analytes) with coefficients of determination of 0.991 or better, was obtained. The membrane bag-assisted-LPME UHPLC-MS/MS approach exhibited high sensitivity, linearity and repeatability for the extraction of the glucocorticoids and also offered an automated streamlined process, from the point where analytes were extracted, to the final analysis of the water samples. The method was employed to determine the concentration of these contaminants in the influent and effluent of a wastewater treatment plant.

Experimental Study of Carbon Dioxide Solubility in Aqueous N-Methyldiethanolamine Solution with 1-Butylpyridinium Tetrafluoroborate Ionic Liquid

New experimental data for CO2 solubility in the aqueous solutions of N-methyldiethanolamine (MDEA) and 1-butylpyridinium tetrafluoroborate ([Bpy][BF4]) ionic liquid (IL) are reported. The experiments were conducted in a static high pressure equilibrium cell. Solubility measurement of CO2 was performed in various solution compositions of IL and MDEA in a wide temperature range of 298.15–343.15 K and pressures up to 4 MPa. The experimental results revealed that, by increasing the weight percent of IL, the absorption capacity of aqueous mixtures diminishes. It was also observed that the main capacity of CO2 loading in the absorbent solutions belonged to MDEA through chemical absorption, whereas its concentration was more effective than IL in gas solubility. The experimental results are correlated using a semiempirical model with good accuracy.

Ionic liquid/reduced graphene oxide/nickel-palladium nanoparticle hybrid synthesized for non-enzymatic electrochemical glucose sensing

Ionic liquids (ILs) were synthesized for the purpose of graphene oxide modification through π-π bonding and anchoring highly dispersed bimetallic Ni-Pd nanoparticles on reduced graphene oxide (RGO). Metallic ions (Pd2+ and Ni2+) were initially attached to an ionic liquid and graphene oxide composite. The ionic liquid served as a stabilizer following metal ions and graphene oxide sheets reduction by NaBH4, which produced an IL/RGO/Ni-Pd hybrid. The π-π interaction between the synthesized ionic liquid and graphene oxide was characterized by nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform infrared spectroscopy (FTIR), and ultraviolet–visible spectroscopy (UV–vis). The result of transmission electron microscopy (TEM) demonstrated Ni-Pd NPs (3–5 nm in size) were uniformly dispersed on the IL/RGO composite. Electrochemical measurements revealed IL/RGO/Ni-Pd modified glassy carbon electrodes directly catalyzed glucose oxidation and displayed enhanced current response compared with RGO/Ni-Pd including a response time within 3 s, a linear range from 0.2 μM to 10 mM, good reproducibility, considerable stability, and excellent anti-interference to electro-active molecules. The superior catalytic activity and selectivity make the IL/RGO/Ni-Pd hybrid a promising nanomaterial for applications in direct detection of glucose.

CO2 selective metal organic framework ZIF-8 modified through ionic liquid encapsulation: A computational study

Nano-scale porous solids are alternate candidates for CO2 handling towards the development of materials for post-combustion CO2 capture with low energy demands and milder operating conditions. Zeolitic imidazolate framework-8 (ZIF-8) is one of the most investigated Metal Organic Frameworks (MOFs) for separation of gas mixtures. In this work, we investigate a new approach of tailoring MOF separation efficiency, by confining pairs of [bmim+][Tf2N−] ionic liquid (IL) in the cages of ZIF-8 (IL@ZIF-8). Molecular force fields, developed by the authors for both the ZIF-8 framework and the [bmim+][Tf2N−] IL, are used in molecular simulations of the system. Monte Carlo simulations are used for sorption of CO2/CH4 and CO2/N2 mixtures computations. The results show an increase of the CO2 sorption due to the presence of the IL, which increases CO2 selectivity and capacity dramatically. Recently reported experiments agree with our findings. Moreover, we explore how CO2 selectivity and capacity varies with IL composition in the IL@ZIF-8 complex, as means to define an optimum IL composition in terms of the separation efficiency.

Multi-scale modeling of isobutane alkylation with 2-butene using composite ionic liquids as catalyst

The alkylation kinetics of isobutane with 2-butene catalyzed by composite ionic liquid (CIL) was investigated with batch experiments. The optimized reaction time of CIL-catalyzed alkylation was found to be less than 30 s, much shorter than the traditional H2SO4-catalyzed one. Based on the carbonium ion mechanism, the kinetic model was further established, in which the concentration profiles of three groups of key components in alkylates with time can be well predicted, i.e. trimethylpentane (TMPs), dimethylhexanes (DMHs) and heavy ends (HEs). The rate constant related to the formation of TMPs in the CIL alkylation is more than two orders of magnitude larger than that in the H2SO4 alkylation. The enhancement of the rate constants for the CIL alkylation at the macroscopic scale can be ascribed into the higher solvation and diffusion of isobutane in the CIL at the microscopic scale, which is confirmed by the solvation free energy and diffusion coefficient calculation using molecular dynamics simulation. Hopefully, the multi-scale information in this work can bring novel insights into the understanding of CIL-catalyzed alkylation and further the design and optimization of this process.

Flame Retardant and Stable Li1.5Al0.5Ge1.5(PO4)3-Supported Ionic Liquid Gel Polymer Electrolytes for High Safety Rechargeable Solid-State Lithium Metal Batteries

Recently, poor security in conventional liquid electrolytes and high interfacial resistance at the electrode/electrolyte interface are the most challenging barriers for the expanded application of lithium batteries. In this regard, easy processing and flexible composite ionic liquid gel polymer electrolytes (ILGPEs) supported by Li1.5Al0.5Ge1.5(PO4)3 (LAGP) are fabricated and investigated. The electrolyte is effectively combined with good electrochemical performances and thermal safety. Among these, the effects of different types of fillers such as the inert filler-SiO2 and the active filler-LAGP on the ionic conductivity were studied in detail. LAGP particles can not only effectively reduce the crystallinity of the polymer matrix but also provide lithium ions and act as the lithium-ion conductor leading to higher ionic conductivity and Li+ ion transference number. Especially, the electrolyte shows good compatibility and no dendrite with the Li metal anode, significantly improving cyclic stability of LiFe...

Deactivation mechanism and activity-recovery approach of composite ionic liquids for isobutane alkylation

The deactivation mechanism and the activity recovery approach of composite ionic liquid (CIL), a kind of acidic chloroaluminate ionic liquids (ILs) modified with CuCl for the in 2013 successfully commercialized catalysis of isobutane alkylation are being discussed in this paper. CIL showed catalytic activity only in the presence of both Brønsted and Lewis acids. CIL deactivation was caused by the loss of Brønsted acidity and/or Lewis acidity. Brønsted acidity decreased by the loss of trace amount of formed chlorohydrocarbons with the outflowing alkylate. Lewis acidity was deactivated mainly due to the complexation of the formed acid soluble oil (ASO) with the CIL anions. Brønsted acidity was maintained by the continuous addition of hydrogen chloride (HCl) or tert-butyl chloride, and Lewis activity was recovered by AlCl3 addition. However, Brønsted acidity could not be recovered when Lewis acidity was lost and was thus dependent on Lewis acidity. Furthermore, ASO interacted with active components of CIL, causing the loss of copper via precipitation of CuCl which is the major contributor to the high selectivity. Therefore, CuCl was added simultaneously with AlCl3 to maintain the high selectivity of alkylate.

Development and application of composite ionic liquid catalyzed isobutane alkylation technology

Alkylate from isobutane alkylation is an ideal blending component of motor gasoline. In China its blending ratio in gasoline is continuously increased with upgrading the gasoline quality standards. A series of studies on ionic liquid catalyzed isobutane alkylation were carried out around a new industrial process of alkylate production. The composition, structure and catalytic performance of chloroaluminate ionic liquids were studied, and a composite ionic liquid (CIL) with high catalytic activity and high selectivity was designed and synthesized. The deactivation mechanism of CIL during isobutane alkylation was studied and a feasible regeneration scheme was developed, including a Lewis acid activity monitoring method of chloroaluminate ionic liquids. A long period (2 months) operation test was carried out in a pilot plant, and then the initial process development of CIL catalyzed isobutane alkylation technology (CILA) was completed. A new type static mixing reactor and a hydrocyclone were developed. The first industrial plant of CILA was designed and constructed. The plant includes feed pretreatment, alkylation reaction, catalyst regeneration, product separation and clean-up systems. The industrial operation results were excellent. Butene conversion reached 100%, research octane number of alkylate maintained stably at above 95 and could reached up to above 98 at optimal operating conditions, end boiling point of alkylate was below 198 °C, and Cl content in alkylate was below 5 mg/L. CILA can produce clean alkylate with clean process, having a good application prospect and promotion value.

Liquid-liquid equilibria and COSMO-SAC modeling of organic solvent/ionic liquid - hydroxyacetone - water mixtures

In this work conventional organic solvents (ethyl acetate, n-propyl acetate, n-butyl acetate, chloroform) as well as ionic liquids, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][Tf2N]) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf2N]), were investigated for the extraction of hydroxyacetone from aqueous solution. The liquid–liquid equilibrium (LLE) data for the ternary systems were experimentally determined at T = 298.15 K and atmospheric pressure. In terms of the distribution coefficient and selectivity, [EMIM][Tf2N] and [BMIM][Tf2N] were found to be the most effective solvents for the extraction of hydroxyacetone from aqueous solution, and the composition of ionic liquids in the raffinate phase was found to be negligible. The experimental results were correlated with the NRTL and UNIQUAC models. The root mean square deviations (RMSD) obtained between the NRTL and UNIQUAC correlations for all the systems were in the range of 0.19–5.18%. COSMO-SAC was then used to make a first principles prediction of the phase equilibria of the systems studied. For the organic solvent-based systems, the deviations between predicted and experimental values were in the range of 3.49–8.00% (% RMSD) whereas for the ionic liquid systems, the deviations were in the range of 16.81–18.53%.

Efficient hydro-liquefaction of woody biomass over ionic liquid nickel based catalyst

The effective hydro-liquefaction process of sawdust is proposed over different ionic liquid Ni-based catalysts at 320 °C. This study investigated the relationship between ionic liquid composition and catalytic performance. The maximum sawdust conversion of 83.11% and liquid yield of 52.38% were achieved over the catalytic system including nickel chloride and 1-butyl-3-methyllimidazolium bromide ([Bmim]Br), suggesting that the anion in ionic liquid played an vital role on the sawdust hydro-liquefaction. The defined impact index was provided to further evaluate the liquefaction performance using ionic liquid Ni-based catalyst. The largest impact index obtained from [Bmim]Br/NiCl2 was in agreement with its excellent catalytic liquefaction performance. The analysis of ionic liquid Ni-based catalyst indicated the coordination interaction between ionic liquid and nickel chloride, which would be favorable to feedstock conversion and improve the bio-oil quality.According to the component distribution, the introduced ionic liquid Ni-based catalytic system was beneficial to sawdust cracking, resulting in the increased amount of smaller compounds. Additionally, the oil compositions highly depended on the employed type of ionic liquid.

Voltammetric sensing based on the use of advanced carbonaceous nanomaterials: a review.

This review (with 210 references) summarizes recent developments in the design of voltammetric chemical sensors and biosensors based on the use of carbon nanomaterials (CNMs). It is divided into subsections starting with an introduction into the field and a description of its current state. This is followed by a large section on various types of voltammetric sensors and biosensors using CNMs with subsections on sensors based on the use of carbon nanotubes, graphene, graphene oxides, graphene nanoribbons, fullerenes, ionic liquid composites with CNMs, carbon nanohorns, diamond nanoparticles, carbon dots, carbon nanofibers and mesoporous carbon. The third section gives conclusion and an outlook. Tables are presented on the application of such sensors to voltammetric detection of neurotransmitters, metabolites, dietary minerals, proteins, heavy metals, gaseous molecules, pharmaceuticals, environmental pollutants, food, beverages, cosmetics, commercial goods and drugs of abuse. The authors also describe advanced approaches for the fabrication of robust functional carbon nano(bio)sensors for voltammetric quantification of multiple targets. Graphical Abstract Featuring execellent electrical, catalytic and surface properies, CNMs have gained enormous attention for designing voltammetric sensors and biosensors. Functionalized CNM-modified electrode interfaces have demonstrated their prominent role in biological, environmental, pharmaceutical, chemical, food and industrial analysis.

Pd nanoparticles/polyoxometalate–ionic liquid composites on SiO2 as multifunctional catalysts for efficient production of ketones from diaryl ethers

Effective and selective transformation of diaryl ethers to value-added ketones.

Ionic Liquids as "Masking" Solvents of the Relative Strength of Bases in Proton Transfer Reactions.

Equilibrium constants for the proton transfer reaction between pyridines and trifluoroacetic acid were measured in room-temperature ionic liquids (ILs) of different cation-anion compositions. The experimental equilibrium constants for ion-pair formation were corrected according to the Fuoss equation. The calculated equilibrium constants for the formation of free ions were taken as a quantitative measure of the base strength in IL solutions and compared with the relative constants in water. The effect of IL composition is discussed for a series of fixed IL anions and fixed IL cations. Finally, the sensitivity of the proton transfer reaction to the electronic effects of the substituent groups on the pyridine ring was quantified by applying the Hammett equation. A more marked levelling effect on the base strength was observed in ILs than in water. The Hammett reaction constants ρ were then correlated with solvent parameters according to a multi-parametric analysis, which showed that both specific hydrogen-bond donor/acceptor and non-specific interactions play an important role, with α and permittivity being the main parameters affecting the ability of the IL to differentiate the strength of the base.