Binary mixtures of HMIMPF6 ionic liquid and n-butyl acetate cosolvent in the extraction of acetone from aqueous solutions

A remarkable disadvantage of pure ionic liquids, to be used as a solvent in different processes, is their high viscosity and density. Here, n-butyl acetate was used as a cosolvent in the liquid–liquid system of {water?+?acetone?+?1-hexyl-3-methylimidazolium hexafluorophosphate (HMIMPF₆) ionic liquid}. Mixtures of the ionic liquid and the cosolvent were used as the organic phase to extract acetone from aqueous phase. A drastic decrease in viscosity and a significant decrease in density of the ionic liquid were achieved in the presence of cosolvent. Accordingly, the liquid–liquid equilibrium of different provided systems was studied under temperature of 298.2?K and atmospheric pressure of 81.5?kPa. Binary phase regions and corresponding tie-lines and binodal curves were obtained for ternary and quaternary systems. Results show the extension of the binodal solubility region as well as enhancements up to 41.8% in the acetone separation factor. The tie-line data consistency was confirmed by the Othmer–Tobias and the Hand equations. Moreover, the nonrandom two-liquid model of activity coefficient was applied satisfactorily to reproduce the equilibrium data with a root-mean-square deviation of only 1.95%.     

Comparative investigation on electrochemical behavior of hydroquinone at carbon ionic liquid electrode, ionic liquid modified carbon paste electrode and carbon paste electrode

Ionic liquid, 1-heptyl-3-methylimidazolium hexafluorophosphate (HMIMPF₆), has been used to fabricate two new electrodes, carbon ionic liquid electrode (CILE) and ionic liquid modified carbon paste electrode (IL/CPE), using graphite powder mixed with HMIMPF₆ or the mixture of HMIMPF₆/paraffin liquid as the binder, respectively. The electrochemical behaviors of hydroquinone at the CILE, the IL/CPE and the CPE were investigated in phosphate buffer solution. At all these electrodes, hydroquinone showed a pair of redox peaks. The order of the current response and the standard rate constant of hydroquinone at these electrodes were as follows: CILE > IL/CPE > CPE, while the peak-to-peak potential separation was in an opposite sequence: CILE < IL/CPE < CPE. The results show the superiority of CILE to IL/CPE and CPE, and IL/CPE to CPE in terms of promoting electron transfer, improving reversibility and enhancing sensitivity. The CILE was chosen as working electrode to determine hydroquinone by differential pulse voltammetry, which can be used for sensitive, simple and rapid determination of hydroquinone in medicated skin cosmetic cream.     

Modeling and simulation of mass transfer in near-critical extraction using a hollow fiber membrane contactor

In this study is presented a general methodology to predict the performance of a continuous near-critical fluid extraction process to remove compounds from aqueous solutions using a hollow fiber membrane contactor. The stabilization of the gas-liquid interface in the membrane porosity and a high surface area to contact both phases represent some of the advantages that hollow fiber contactors offer over conventional contactor devices for the extraction of compounds from liquid feeds.A mathematical model has been developed integrating a resistances-in-series mass transfer system that takes into account boundary layers, membrane porosity and thermodynamic considerations with mass balances of the membrane contactor. Simulation algorithms were easily implemented with low calculation requirements.The system studied in this work is a membrane based extractor of ethanol and acetone from aqueous solutions using near-critical CO₂. Predictions of extraction percentages obtained by simulations have been compared to the experimental values reported by Bothun et al. [2003a. Compressed solvents for the extraction of fermentation products within a hollow fiber membrane contactor. Journal of Supercritical Fluids 25, 119-134]. Simulations of extraction percentage of ethanol and acetone show an average difference of 36.3% and 6.75% with the experimental data, respectively. More accurate predictions of the extraction of acetone could be explained by a better estimation of the transport properties in the aqueous phase that controls the extraction of this solute.When the model was validated, the effect of the configuration and the operating parameters was studied and local mass transfer resistances were evaluated. The proposed approach allows the evaluation of the relevance of membrane hydrophobicity for extraction in solutions under different thermodynamic conditions. This original methodology based on well-known phenomenological equations represents a general approach which could be applied in other processes using membrane contactors with different configurations.     

Selective Separation of Toluene/n‐Heptane by Supported Ionic Liquid Membranes with [Bmim][BF4]

Room‐temperature ionic liquids serve as alternative solvents for volatile organic compounds in liquid‐liquid extraction and liquid membrane separation. 1‐Butyl‐3‐methylimidazolium tetrafluoroborate ([Bmim][BF₄]) was applied for extraction and supported ionic liquid membranes (SILMs) to separate toluene and n‐heptane. A high separation factor of toluene was achieved due to the strong interaction between ionic liquid cations and toluene. The mass transfer performance of the SILM process was enhanced by higher operating temperature. With the increase of initial toluene concentration in the feed phase, the mass transfer flux and removal efficiency of the SILM process were improved, while the separation factor decreased. The mass transfer flux was growing with the increase of flow rate at both sides. The SILM process was stable over a long time period due to the high viscosity and low volatility of [Bmim][BF₄].     

Long Term Pilot Plant Experience on Aromatics Extraction with Ionic Liquids

Since 2004, we have been conducting pilot plant trials with various contactors and different ionic liquids for petrochemical model feeds as well as real refinery feeds. Our pilot plant contains a Rotating Disc Contactor with a height of 6 m and a diameter of 60 mm. Up to 100 kg of ionic liquid and 200 L of feed are applied in experiments. In this paper, the hydrodynamic and mass transfer performance of a rotating disc contactor has been characterized for toluene/n-heptane, a model FCC feed and a real LCCS refinery feed using 3-methyl-N-butyl-pyridinum dicyanamide ([3-mebupy]N(CN)₂) as the ionic liquid. Experiments with the real LCCS feed demonstrated comparable extraction performance to the model FCC feed. Over the past 5 years, the same batches of the ionic liquid have been repeatedly regenerated by evaporation and reused. Our studies revealed that, although coloration occurs, the extraction performance of the ionic liquids has not changed even after several years of usage. After the real LCCS refinery feed experiments, validation with the toluene/n-heptane model feed confirmed unchanged extraction performance.

Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science and Technology to view the free supplemental file.     

Mass transfer modeling of membrane carrier system for extraction of Ce(IV) from sulfate media using hollow fiber supported liquid membrane

A theoretical and experimental study on the extraction and stripping of Ce(IV) ions from sulfate media using microporous hydrophobic hollow fiber supported liquid membrane has been performed. The experiments were made in the recycling mode. Tri-n-octylamine (TOA) was used as extractant diluted in kerosene and sodium hydroxide was use as strip solution. The mathematical model focused on the extraction side of a liquid membrane system. The aqueous feed mass transfer coefficient (k_i) and the organic mass transfer coefficient (k_m) which were calculated from the model were 9.47 X 10^-2 and 6.303 cm/s, respectively. Therefore, the rate controlling step is the diffusion of the cerium complex across a liquid membrane. In addition, the mass transfer modeling was performed and the validity of the developed model was evaluated with experimental data and found to tie in well with the theoretical value when the concentration of TOA was higher than 5% (v/v).     

Separation of m-cresol from aromatic hydrocarbon and alkane using ionic liquids via hydrogen bond interaction

Low temperature coal tar contained a large amount of phenols, aromatic hydrocarbons and alkanes; the separation of phenols from coal tar has a great significance to the deep processing of coal tar. In this work, the separation of m-cresol from cumene and n-heptane by liquid–liquid extraction using ionic liquids (ILs) as extractants was studied. The suitable ILs were screened by conductor-like screening model for real solvents (COSMO-RS) model and the liquid–liquid phase equilibrium (LLE) experiments were to verify the accuracy of the screening results. The extraction conditions such as extraction time, extraction temperature and mass ratio of ILs to model oils were evaluated. An internal mechanism of the m-cresol extract by ILs was revealed by COSMO-RS calculation and FT-IR. The results showed that the selected ILs can extract m-cresol effectively from cumene and n-heptane, 1-ethyl-3-methylimidazolium acetate (emimCH₃COO) was the best extraction solvent. A hydrogen bond between anion of ILs and phenolic hydroxyl groups was observed. M-cresol in model oils could be extracted with extraction efficiencies up to 98.85% at an emimCH₃COO: model oils mass ratio of 0.5 and 298.15 K, emimCH₃COO could be regenerated and reused for 4 cycles without obvious decreases in extraction efficiency and extractant mass.     

Extraction of dioxouranium(VI) in small channels using ionic liquids

The extraction behaviour of dioxouranium(VI) from nitric acid solutions with tributylphosphate (TBP) dissolved (30%, v/v) in room temperature ionic liquids (viz. 1-butyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide, [C₄mim][NTf₂], 1-decyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide, [C₁₀mim][NTf₂], and trihexyltetradecylphosphonium bis{(trifluoromethyl)sulfonyl}amide, [P_6 6 6 14][NTf₂]) was investigated. The experiments were performed in a capillary (0.5 mm internal diameter) made of Teflon, operated in the plug flow regime. The effects of ionic liquid type, initial nitric acid concentration, and residence time on dioxouranium(VI) extraction were studied. UV–vis spectroscopy was used for the determination of the dioxouranium(VI) concentration in the ionic liquid phase. For increasing [HNO₃]_aq,init, the %extraction decreased and then increased for [C₄mim][NTf₂], while for the other two ionic liquids it increased. The %extraction also increased with residence time in the channel. Overall mass transfer coefficients were about 0.2 s^–1 in all TBP/ionic liquid systems at the initial nitric acid concentration of 3 M when a 10 cm capillary was used.     

Extraction separation of toluene/cyclohexane with hollow fiber supported ionic liquid membrane

A supported liquid membrane with ionic liquid was used for the separation of toluene/cyclohexane. The interactions of ionic liquid with toluene and cyclohexane were calculated and experimentally studied by quantum chemical calculation and liquid-liquid extraction process. The results showed [BPy][BF₄] have stronger interaction with toluene than that with cyclohexane. The selectivity of SILM processes was larger than 10 at the temperature of 323 K and the flow rate of 13.5 mL·min^?1 on both shell side and lumen side. Due to the higher viscosity of IL, SILM process had good long-term stability. As the effects of mass transfer driving force of SILM process, the flux and removal efficiency increased with increase of initial toluene concentration, while the selectivity decreased because of the competitive transport. Base on the resistance in-series model and experimental results, the mass transfer resistance was mainly lay liquid membrane phase. The influence of flow rates on both sides was slight. The higher temperature could enhance the mass transfer performance significantly. The removal efficiency increased from 28.2% to 45.1% with the increasing of operation temperature from 298 K to 323 K.     

Numerical Simulation of Absorbing CO2 with Ionic Liquids

Although separating CO₂ from flue gas with ionic liquids has been regarded as a new and effective method, the mass transfer properties of CO₂ absorption in these solvents have not been researched. In this paper, a coupled computational fluid dynamic (CFD) model and population balance model (PBM) was applied to study the mass transfer properties for capturing CO₂ with ionic liquids solvents. The numerical simulation was performed using the Fluent code. Considering the unique properties of ionic liquids, the Eulerian‐Eulerian two‐flow model with a new drag coefficient correlation was employed for the gas‐liquid fluid dynamic simulation. The gas holdup, interfacial area, and bubble size distribution in the bubble column reactor were predicted. The mass transfer coefficients were estimated with Higbie's penetration model. Furthermore, the velocity field and pressure field in the reactor were also predicted in this paper.     

Extraction Behavior of Cu(II) Ion From Chloride Medium to the Hydrophobic Ionic Liquids Using 1,10-Phenanthroline

The study of liquid-liquid extraction of Cu(II) ion was carried out by using a series of hydrophobic ionic liquids; 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄mimPF₆]), 1-hexyl-3-methylimidazolium hexafluorophospahate ([C₆mimPF₆]), 1-butyl-3-methylimidazolium bistrifluoromethylsulfonyl imide ([C₄mimNTf₂]) and 1-hexyl-3-methylimidazolium bistrifluoromethylsulfonyl imide ([C₆mimNTf₂]) as extraction phase. Cu(II) prefer to extract into [C₄mimPF₆] which is the less hydrophobic of ionic liquids. The extraction behavior of Cu(II) ion depends on the type of counterion and the extraction of Cu(II) ion in ionic liquid system proceeds via similar mechanism with a molecular organic solvent. From these results, it was proposed that the extraction of Cu complexes from chloride medium proceeds through ion pair mechanism.     

Proposed kinetic mechanism of biodiesel production through lipase catalysed interesterification with a methyl acetate acyl acceptor and ionic liquid [BMIM][PF6] co‐solvent

The production of biodiesel was investigated using a lipase‐catalysed (Novozym 435) reaction involving methyl acetate and ionic liquid [BMIM][PF₆] as a co‐solvent to produce an environmentally friendly, “green” process. Experiments were conducted at various amounts of ionic liquid. The reaction mechanism was examined through use of kinetic modelling and the effect of ionic liquid was studied for the first time. Studies indicated that the reaction followed a Ping–Pong Bi–Bi mechanism, and that the ionic liquid present in the system led to reduced initial reaction rates due to mass transfer limitations.     

Separation of Toluene-Trichlorotrinitrobenzene Mixture with CO2 at Elevated Pressures

Abstract

A flow apparatus was used to study the separation of toluene from a liquid mixture containing mainly toluene and TCTNB (trichlorotrinitrobenzene) with CO₂ at elevated pressures. Experimental results indicated that toluene of 100% purity could be obtained when the operating pressures were below the critical pressure of the CO₂-toluene mixture. The most appropriate operating conditions were found to be at a temperature of 311 K and at a pressure of 61.2 atm. Because the solubility of toluene in CO₂ for the system CO₂-toluene-TCTNB was found to be close to that for the binary system CO₂-toluene, the data for the latter system could be used to model the present extraction operation. The effects of several packings, including glass beads of different sizes and structure packing, on mass transfer rate were also measured in this work. The data indicated that the interphase mass transfer resistances played an important role during the extraction.     

REACTIVE EXTRACTION OF LEVULINIC ACID FROM AQUEOUS SOLUTIONS WITH TRI-n-OCTYLAMINE (TOA) IN 1-OCTANOL: EQUILIBRIA,KINETICS, AND MODEL DEVELOPMENT

Levulinic acid, a carboxylic acid containing a ketone structure, can be used as an acidulant in foods and beverages. Reactive extraction is a promising alternative for the recovery of carboxylic acids from aqueous streams. The design of an amine extraction process requires kinetic data for the acid-amine + solvent system used. In this study, equilibrium and kinetic data on the extraction of levulinic acid from aqueous solutions using tri-n-octylamine (TOA) in 1-octanol have been determined. The mass transfer coefficients of levulinic acid, TOA, and 2:1 levulinic acid-amine complex in 1-octanol were calculated from the acetic acid mass transfer coefficient, which was determined by measuring its fluxes of simple diffusion from kerosene to water. Based on the Hatta number and the criterion given by Doraiswamy and Sharma, the reaction regime has been found to be instantaneous reaction regime occurring at the interface on the organic phase side. An extraction model comprising equilibrium complexation constant w.r.t 2:1 levulinic acid-TOA complex formation, K_E2i (14.794 (m³ kmol^?1)²), and complex mass transfer coefficient, k_B2A (2.193 × 10^?6 m s^?1), has been developed.     

Computer‐aided design of ionic liquids as solvents for extractive desulfurization

Although ionic liquids (ILs) have been widely explored as solvents for extractive desulfurization (EDS) of fuel oils, systematic studying of the optimal design of ILs for this process is still scarce. The UNIFAC‐IL model is extended first to describe the EDS system based on exhaustive experimental data. Then, based on the obtained UNIFAC‐IL model and group contribution models for predicting the melting point and viscosity of ILs, a mixed‐integer nonlinear programming (MINLP) problem is formulated for the purpose of computer‐aided ionic liquid design (CAILD). The MINLP problem is solved to optimize the liquid‐liquid extraction performance of ILs in a given multicomponent model EDS system, under consideration of constraints regarding the IL structure, thermodynamic and physical properties. The top five IL candidates preidentified from CAILD are further evaluated by means of process simulation using ASPEN Plus. Thereby, [C₅MPy][C(CN)₃] is identified as the most suitable solvent for EDS. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1013–1025, 2018     

The kinetic modelling of a steam distillation unit for the extraction of aniseed (Pimpinella anisum) essential oil

A simplified model that considered the oil constituents as one constituent, anethole, the major component, was used to describe the mass transfer of steam extraction of aniseed essential oil. The model can be used to optimise and control the process. Depending on the oil content, two mass transfer regimes were identified (i) the first one corresponds to an unsaturated surface extraction and (ii) the second corresponds to the slower transfer of oil from the deeper parts of the material to the surface, which may be due to concentration gradients and chemical bonding. The model was validated by experimental data obtained from a pilot‐plant system. Solid‐steam mass transfer coefficients were determined and a critical oil content was found to limit the two mass transfer regimes. The value for this critical oil concentration (x_B) was found to be 0.011 (g oil g^?1 solid). In addition, an optimal operating pressure of 200 kPa was found to give maximum extraction yield. Copyright © 2005 Society of Chemical Industry     

新型PVC/OHA/D2EHPA基膜增强型聚合物包容膜的制备及性能评价

为解决聚合物包容膜(PIM)传输效率低的问题。制备了一种以聚氯乙烯(PVC)为基体,包含固液两种载体的基膜增强型PIM。以N-羟基正辛酰胺(OHA)作为新型载体固定于基膜孔道内,利用其与有机萃取剂二(2-乙基己基)磷酸酯(D2EHPA)的协同作用,实现高效传质。对制备的基膜增强型PIM进行SEM、EDS、FTIR、XPS、力学性能以及传质性能考察与表征。结果表明,载体配比为22% OHA+17% D2EHPA的基膜增强性PIM对50 mg/L的Zn_²⁺的10h回收效果最佳,萃取率和反萃率分别为59.86%和51.10%。5个周期的运行实验中,基膜增强型PIM初始传质通量为587.36 mg.m_^-2.h_^-1,约是仅包含液相萃取剂PIM传质通量(312.64 mg.m_^-2.h_^-1)的2倍。5个循环周期结束后,基膜增强型PIM传质通量仍高于仅包含液相萃取剂PIM传质通量。     

Improvement of biphasic polymerization by application of binary ionic liquid mixture

The mixture of two ionic liquids, 1-n-butyl-3-methylimidazolium and 1-(2-phenylethyl)-3-methylimidazolium chloroaluminates, [C₄-mim][AlCl₄] and [PhC₂-mim][AlCl₄], were applied as a medium to immobilize the Cp₂TiCl₂ titanocene catalyst for biphasic ionic liquid/hexane ethylene polymerization. The system makes possible to perform the reaction at lower temperatures, below the melting temperature of the aralkyl ionic liquid. A better separation of the ionic liquid phase was observed and an easier mass transfer of the polymer product from the ionic liquid to the hexane phase was obtained. The polyethylene reveals bimodal distribution of molecular weight. It is characterized by a high bulk density (500 g/dm³) and crystallinity degree (86%). The recycling of the ionic liquid medium containing the catalyst activated by AlEtCl₂, results in the highest yield obtained in such systems (550 kg PE(mol Ti)⁻¹).     

Efficient capture of carbon dioxide with novel mass‐transfer intensification device using ionic liquids

A novel mass‐transfer intensified approach for CO₂ capture with ionic liquids (ILs) using rotating packed bed (RPB) reactor was presented. This new approach combined the advantages of RPB as a high mass‐transfer intensification device for viscous system and IL as a novel, environmentally benign CO₂ capture media with high thermal stability and extremely low volatility. Amino‐functionalized IL (2‐hydroxyethyl)‐trimethyl‐ammonium (S)?2‐pyrrolidinecarboxylic acid salt ([Choline][Pro]) was synthesized to perform experimental examination of CO₂ capture by chemical absorption. In RPB, it took only 0.2 s to reach 0.2 mol CO₂/mol IL at 293 K, indicating that RPB was kinetically favorable to absorption of CO₂ in IL because of its efficient mass‐transfer intensification. The effects of operation parameters on CO₂ removal efficiency and IL absorbent capacity were studied. In addition, a model based on penetration theory was proposed to explore the mechanism of gas–liquid mass transfer of ILs system in RPB. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2957–2965, 2013